Merge pull request #752 from ericchiang/saml

Add an experimental SAML connector
2017-01-09 18:33:00 -08:00 · 2017-01-09 18:33:00 -08:00 · 7f72ea786d
commit 7f72ea786d
parent 15fadeaf86 7ea2d24011
28 changed files with 4075 additions and 22 deletions
--- a/Documentation/saml-connector.md
+++ b/Documentation/saml-connector.md
@ -0,0 +1,72 @@
+# Authentication through SAML 2.0
+
+## Overview
+
+The experimental SAML provider allows authentication through the SAML 2.0 HTTP POST binding.
+
+The connector uses the value of the `NameID` element as the user's unique identifier which dex assumes is both unique and never changes. Use the `nameIDPolicyFormat` to ensure this is set to a value which satisfies these requirements.
+
+## Caveats
+
+There are known issues with the XML signature validation for this connector. In addition work is still being done to ensure this connector implements best security practices for SAML 2.0.
+
+The connector doesn't support signed AuthnRequests or encrypted attributes.
+
+The connector doesn't support refresh tokens since the SAML 2.0 protocol doesn't provide a way to requery a provider without interaction.
+
+## Configuration
+
+```yaml
+connectors:
+- type: samlExperimental # will be changed to "saml" later without support for the "samlExperimental" value
+  id: saml
+  config:
+    # Issuer used for validating the SAML response.
+    issuer: https://saml.example.com
+    # SSO URL used for POST value.
+    ssoURL: https://saml.example.com/sso
+
+    # CA to use when validating the SAML response.
+    ca: /path/to/ca.pem
+
+    # CA's can also be provided inline as a base64'd blob. 
+    #
+    # catData: ( RAW base64'd PEM encoded CA )
+
+    # To skip signature validation, uncomment the following field. This should
+    # only be used during testing and may be removed in the future.
+    # 
+    # insucreSkipSignatureValidation: true
+
+    # Dex's callback URL. Must match the "Destination" attribute of all responses
+    # exactly.  
+    redirectURI: https://dex.example.com/callback
+
+    # Name of attributes in the returned assertions to map to ID token claims.
+    usernameAttr: name
+    emailAttr: email
+    groupsAttr: groups # optional
+
+    # By default, multiple groups are assumed to be represented as multiple
+    # attributes with the same name.
+    #
+    # If "groupsDelim" is provided groups are assumed to be represented as a
+    # single attribute and the delimiter is used to split the attribute's value
+    # into multiple groups.
+    #
+    # groupsDelim: ", "
+
+
+    # Requested format of the NameID. The NameID value is is mapped to the ID Token
+    # 'sub' claim.  This can be an abbreviated form of the full URI with just the last
+    # component. For example, if this value is set to "emailAddress" the format will
+    # resolve to:
+    #
+    #     urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress
+    #
+    # If no value is specified, this value defaults to:
+    #
+    #     urn:oasis:names:tc:SAML:2.0:nameid-format:persistent
+    #
+    nameIDPolicyFormat: persistent
+```
--- a/README.md
+++ b/README.md
@ -37,6 +37,7 @@ More docs for running dex as a Kubernetes authenticator can be found [here](Docu
 * Identity provider logins
  * [LDAP](Documentation/ldap-connector.md)
  * [GitHub](Documentation/github-connector.md)
+  * [SAML 2.0 (experimental)](Documentation/saml-connector.md)
 * Client libraries
  * [Go][go-oidc]

--- a/cmd/dex/config.go
+++ b/cmd/dex/config.go
@ -14,6 +14,7 @@ import (
 	"github.com/coreos/dex/connector/ldap"
 	"github.com/coreos/dex/connector/mock"
 	"github.com/coreos/dex/connector/oidc"
+	"github.com/coreos/dex/connector/saml"
 	"github.com/coreos/dex/server"
 	"github.com/coreos/dex/storage"
 	"github.com/coreos/dex/storage/kubernetes"
@ -177,11 +178,12 @@ type ConnectorConfig interface {
 }

 var connectors = map[string]func() ConnectorConfig{
-	"mockCallback": func() ConnectorConfig { return new(mock.CallbackConfig) },
-	"mockPassword": func() ConnectorConfig { return new(mock.PasswordConfig) },
-	"ldap":         func() ConnectorConfig { return new(ldap.Config) },
-	"github":       func() ConnectorConfig { return new(github.Config) },
-	"oidc":         func() ConnectorConfig { return new(oidc.Config) },
+	"mockCallback":     func() ConnectorConfig { return new(mock.CallbackConfig) },
+	"mockPassword":     func() ConnectorConfig { return new(mock.PasswordConfig) },
+	"ldap":             func() ConnectorConfig { return new(ldap.Config) },
+	"github":           func() ConnectorConfig { return new(github.Config) },
+	"oidc":             func() ConnectorConfig { return new(oidc.Config) },
+	"samlExperimental": func() ConnectorConfig { return new(saml.Config) },
 }

 // UnmarshalJSON allows Connector to implement the unmarshaler interface to
--- a/cmd/example-app/main.go
+++ b/cmd/example-app/main.go
@ -241,12 +241,15 @@ func (a *app) handleLogin(w http.ResponseWriter, r *http.Request) {

 	authCodeURL := ""
 	scopes = append(scopes, "openid", "profile", "email")
-	if a.offlineAsScope {
+	if r.FormValue("offline_acecss") != "yes" {
+		authCodeURL = a.oauth2Config(scopes).AuthCodeURL(exampleAppState)
+	} else if a.offlineAsScope {
 		scopes = append(scopes, "offline_access")
 		authCodeURL = a.oauth2Config(scopes).AuthCodeURL(exampleAppState)
 	} else {
 		authCodeURL = a.oauth2Config(scopes).AuthCodeURL(exampleAppState, oauth2.AccessTypeOffline)
 	}
+
 	http.Redirect(w, r, authCodeURL, http.StatusSeeOther)
 }

--- a/cmd/example-app/templates.go
+++ b/cmd/example-app/templates.go
@ -14,6 +14,9 @@ var indexTmpl = template.Must(template.New("index.html").Parse(`<html>
       </p>
       <p>
         Extra scopes:<input type="text" name="extra_scopes" placeholder="list of scopes">
+       </p>
+	   <p>
+	     Request offline access:<input type="checkbox" name="offline_access" value="yes" checked>
       </p>
       <input type="submit" value="Login">
    </form>
--- a/connector/connector.go
+++ b/connector/connector.go
@ -66,6 +66,23 @@ type CallbackConnector interface {
 	HandleCallback(s Scopes, r *http.Request) (identity Identity, err error)
 }

+// SAMLConnector represents SAML connectors which implement the HTTP POST binding.
+//
+// RelayState is handled by the server.
+type SAMLConnector interface {
+	// POSTData returns an encoded SAML request and SSO URL for the server to
+	// render a POST form with.
+	POSTData(s Scopes) (sooURL, samlRequest string, err error)
+
+	// TODO(ericchiang): Provide expected "InResponseTo" ID value.
+	//
+	// See: https://www.oasis-open.org/committees/download.php/35711/sstc-saml-core-errata-2.0-wd-06-diff.pdf
+	// "3.2.2 Complex Type StatusResponseType"
+
+	// HandlePOST decodes, verifies, and maps attributes from the SAML response.
+	HandlePOST(s Scopes, samlResponse string) (identity Identity, err error)
+}
+
 // RefreshConnector is a connector that can update the client claims.
 type RefreshConnector interface {
 	// Refresh is called when a client attempts to claim a refresh token. The
--- a/connector/saml/saml.go
+++ b/connector/saml/saml.go
@ -0,0 +1,387 @@
+// Package saml contains login methods for SAML.
+package saml
+
+import (
+	"bytes"
+	"compress/flate"
+	"crypto/rand"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/pem"
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"strings"
+	"time"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/beevik/etree"
+	dsig "github.com/russellhaering/goxmldsig"
+
+	"github.com/coreos/dex/connector"
+)
+
+const (
+	bindingRedirect = "urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect"
+	bindingPOST     = "urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
+
+	nameIDFormatEmailAddress = "urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress"
+	nameIDFormatUnspecified  = "urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified"
+	nameIDFormatX509Subject  = "urn:oasis:names:tc:SAML:1.1:nameid-format:X509SubjectName"
+	nameIDFormatWindowsDN    = "urn:oasis:names:tc:SAML:1.1:nameid-format:WindowsDomainQualifiedName"
+	nameIDFormatEncrypted    = "urn:oasis:names:tc:SAML:2.0:nameid-format:encrypted"
+	nameIDFormatEntity       = "urn:oasis:names:tc:SAML:2.0:nameid-format:entity"
+	nameIDFormatKerberos     = "urn:oasis:names:tc:SAML:2.0:nameid-format:kerberos"
+	nameIDFormatPersistent   = "urn:oasis:names:tc:SAML:2.0:nameid-format:persistent"
+	nameIDformatTransient    = "urn:oasis:names:tc:SAML:2.0:nameid-format:transient"
+)
+
+var (
+	nameIDFormats = []string{
+		nameIDFormatEmailAddress,
+		nameIDFormatUnspecified,
+		nameIDFormatX509Subject,
+		nameIDFormatWindowsDN,
+		nameIDFormatEncrypted,
+		nameIDFormatEntity,
+		nameIDFormatKerberos,
+		nameIDFormatPersistent,
+		nameIDformatTransient,
+	}
+	nameIDFormatLookup = make(map[string]string)
+)
+
+func init() {
+	suffix := func(s, sep string) string {
+		if i := strings.LastIndex(s, sep); i > 0 {
+			return s[i+1:]
+		}
+		return s
+	}
+	for _, format := range nameIDFormats {
+		nameIDFormatLookup[suffix(format, ":")] = format
+		nameIDFormatLookup[format] = format
+	}
+}
+
+// Config represents configuration options for the SAML provider.
+type Config struct {
+	// TODO(ericchiang): A bunch of these fields could be auto-filled if
+	// we supported SAML metadata discovery.
+	//
+	// https://www.oasis-open.org/committees/download.php/35391/sstc-saml-metadata-errata-2.0-wd-04-diff.pdf
+
+	Issuer string `json:"issuer"`
+	SSOURL string `json:"ssoURL"`
+
+	// X509 CA file or raw data to verify XML signatures.
+	CA     string `json:"ca"`
+	CAData []byte `json:"caData"`
+
+	InsecureSkipSignatureValidation bool `json:"insecureSkipSignatureValidation"`
+
+	// Assertion attribute names to lookup various claims with.
+	UsernameAttr string `json:"usernameAttr"`
+	EmailAttr    string `json:"emailAttr"`
+	GroupsAttr   string `json:"groupsAttr"`
+	// If GroupsDelim is supplied the connector assumes groups are returned as a
+	// single string instead of multiple attribute values. This delimiter will be
+	// used split the groups string.
+	GroupsDelim string `json:"groupsDelim"`
+
+	RedirectURI string `json:"redirectURI"`
+
+	// Requested format of the NameID. The NameID value is is mapped to the ID Token
+	// 'sub' claim.
+	//
+	// This can be an abbreviated form of the full URI with just the last component. For
+	// example, if this value is set to "emailAddress" the format will resolve to:
+	//
+	//		urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress
+	//
+	// If no value is specified, this value defaults to:
+	//
+	//		urn:oasis:names:tc:SAML:2.0:nameid-format:persistent
+	//
+	NameIDPolicyFormat string `json:"nameIDPolicyFormat"`
+}
+
+type certStore struct {
+	certs []*x509.Certificate
+}
+
+func (c certStore) Certificates() (roots []*x509.Certificate, err error) {
+	return c.certs, nil
+}
+
+// Open validates the config and returns a connector. It does not actually
+// validate connectivity with the provider.
+func (c *Config) Open(logger logrus.FieldLogger) (connector.Connector, error) {
+	return c.openConnector(logger)
+}
+
+func (c *Config) openConnector(logger logrus.FieldLogger) (interface {
+	connector.SAMLConnector
+}, error) {
+	requiredFields := []struct {
+		name, val string
+	}{
+		{"issuer", c.Issuer},
+		{"ssoURL", c.SSOURL},
+		{"usernameAttr", c.UsernameAttr},
+		{"emailAttr", c.EmailAttr},
+		{"redirectURI", c.RedirectURI},
+	}
+	var missing []string
+	for _, f := range requiredFields {
+		if f.val == "" {
+			missing = append(missing, f.name)
+		}
+	}
+	switch len(missing) {
+	case 0:
+	case 1:
+		return nil, fmt.Errorf("missing required field %q", missing[0])
+	default:
+		return nil, fmt.Errorf("missing required fields %q", missing)
+	}
+
+	p := &provider{
+		issuer:       c.Issuer,
+		ssoURL:       c.SSOURL,
+		now:          time.Now,
+		usernameAttr: c.UsernameAttr,
+		emailAttr:    c.EmailAttr,
+		groupsAttr:   c.GroupsAttr,
+		groupsDelim:  c.GroupsDelim,
+		redirectURI:  c.RedirectURI,
+		logger:       logger,
+
+		nameIDPolicyFormat: c.NameIDPolicyFormat,
+	}
+
+	if p.nameIDPolicyFormat == "" {
+		p.nameIDPolicyFormat = nameIDFormatPersistent
+	} else {
+		if format, ok := nameIDFormatLookup[p.nameIDPolicyFormat]; ok {
+			p.nameIDPolicyFormat = format
+		} else {
+			return nil, fmt.Errorf("invalid nameIDPolicyFormat: %q", p.nameIDPolicyFormat)
+		}
+	}
+
+	if !c.InsecureSkipSignatureValidation {
+		if (c.CA == "") == (c.CAData == nil) {
+			return nil, errors.New("must provide either 'ca' or 'caData'")
+		}
+
+		var caData []byte
+		if c.CA != "" {
+			data, err := ioutil.ReadFile(c.CA)
+			if err != nil {
+				return nil, fmt.Errorf("read ca file: %v", err)
+			}
+			caData = data
+		} else {
+			caData = c.CAData
+		}
+
+		var (
+			certs []*x509.Certificate
+			block *pem.Block
+		)
+		for {
+			block, caData = pem.Decode(caData)
+			if block == nil {
+				break
+			}
+			cert, err := x509.ParseCertificate(block.Bytes)
+			if err != nil {
+				return nil, fmt.Errorf("parse cert: %v", err)
+			}
+			certs = append(certs, cert)
+		}
+		if len(certs) == 0 {
+			return nil, errors.New("no certificates found in ca data")
+		}
+		p.validator = dsig.NewDefaultValidationContext(certStore{certs})
+	}
+	return p, nil
+}
+
+type provider struct {
+	issuer string
+	ssoURL string
+
+	now func() time.Time
+
+	// If nil, don't do signature validation.
+	validator *dsig.ValidationContext
+
+	// Attribute mappings
+	usernameAttr string
+	emailAttr    string
+	groupsAttr   string
+	groupsDelim  string
+
+	redirectURI string
+
+	nameIDPolicyFormat string
+
+	logger logrus.FieldLogger
+}
+
+func (p *provider) POSTData(s connector.Scopes) (action, value string, err error) {
+
+	// NOTE(ericchiang): If we can't follow up with the identity provider, can we
+	// support refresh tokens?
+	if s.OfflineAccess {
+		return "", "", fmt.Errorf("SAML does not support offline access")
+	}
+
+	r := &authnRequest{
+		ProtocolBinding: bindingPOST,
+		ID:              "_" + uuidv4(),
+		IssueInstant:    xmlTime(p.now()),
+		Destination:     p.ssoURL,
+		Issuer: &issuer{
+			Issuer: p.issuer,
+		},
+		NameIDPolicy: &nameIDPolicy{
+			AllowCreate: true,
+			Format:      p.nameIDPolicyFormat,
+		},
+	}
+
+	data, err := xml.MarshalIndent(r, "", "  ")
+	if err != nil {
+		return "", "", fmt.Errorf("marshal authn request: %v", err)
+	}
+
+	buff := new(bytes.Buffer)
+	fw, err := flate.NewWriter(buff, flate.DefaultCompression)
+	if err != nil {
+		return "", "", fmt.Errorf("new flate writer: %v", err)
+	}
+	if _, err := fw.Write(data); err != nil {
+		return "", "", fmt.Errorf("compress message: %v", err)
+	}
+	if err := fw.Close(); err != nil {
+		return "", "", fmt.Errorf("flush message: %v", err)
+	}
+
+	return p.ssoURL, base64.StdEncoding.EncodeToString(buff.Bytes()), nil
+}
+
+func (p *provider) HandlePOST(s connector.Scopes, samlResponse string) (ident connector.Identity, err error) {
+	rawResp, err := base64.StdEncoding.DecodeString(samlResponse)
+	if err != nil {
+		return ident, fmt.Errorf("decode response: %v", err)
+	}
+	if p.validator != nil {
+		if rawResp, err = verify(p.validator, rawResp); err != nil {
+			return ident, fmt.Errorf("verify signature: %v", err)
+		}
+	}
+
+	var resp response
+	if err := xml.Unmarshal(rawResp, &resp); err != nil {
+		return ident, fmt.Errorf("unmarshal response: %v", err)
+	}
+
+	if resp.Destination != "" && resp.Destination != p.redirectURI {
+		return ident, fmt.Errorf("expected destination %q got %q", p.redirectURI, resp.Destination)
+
+	}
+
+	assertion := resp.Assertion
+	if assertion == nil {
+		return ident, fmt.Errorf("response did not contain an assertion")
+	}
+	subject := assertion.Subject
+	if subject == nil {
+		return ident, fmt.Errorf("response did not contain a subject")
+	}
+
+	switch {
+	case subject.NameID != nil:
+		if ident.UserID = subject.NameID.Value; ident.UserID == "" {
+			return ident, fmt.Errorf("NameID element does not contain a value")
+		}
+	default:
+		return ident, fmt.Errorf("subject does not contain an NameID element")
+	}
+
+	attributes := assertion.AttributeStatement
+	if attributes == nil {
+		return ident, fmt.Errorf("response did not contain a AttributeStatement")
+	}
+
+	if ident.Email, _ = attributes.get(p.emailAttr); ident.Email == "" {
+		return ident, fmt.Errorf("no attribute with name %q", p.emailAttr)
+	}
+	ident.EmailVerified = true
+
+	if ident.Username, _ = attributes.get(p.usernameAttr); ident.Username == "" {
+		return ident, fmt.Errorf("no attribute with name %q", p.usernameAttr)
+	}
+
+	if s.Groups && p.groupsAttr != "" {
+		if p.groupsDelim != "" {
+			groupsStr, ok := attributes.get(p.groupsAttr)
+			if !ok {
+				return ident, fmt.Errorf("no attribute with name %q", p.groupsAttr)
+			}
+			// TOOD(ericchiang): Do we need to further trim whitespace?
+			ident.Groups = strings.Split(groupsStr, p.groupsDelim)
+		} else {
+			groups, ok := attributes.all(p.groupsAttr)
+			if !ok {
+				return ident, fmt.Errorf("no attribute with name %q", p.groupsAttr)
+			}
+			ident.Groups = groups
+		}
+	}
+
+	return ident, nil
+}
+
+// verify checks the signature info of a XML document and returns
+// the signed elements.
+func verify(validator *dsig.ValidationContext, data []byte) (signed []byte, err error) {
+	doc := etree.NewDocument()
+	if err := doc.ReadFromBytes(data); err != nil {
+		return nil, fmt.Errorf("parse document: %v", err)
+	}
+
+	result, err := validator.Validate(doc.Root())
+	if err != nil {
+		return nil, err
+	}
+	doc.SetRoot(result)
+	return doc.WriteToBytes()
+}
+
+func uuidv4() string {
+	u := make([]byte, 16)
+	if _, err := rand.Read(u); err != nil {
+		panic(err)
+	}
+	u[6] = (u[6] | 0x40) & 0x4F
+	u[8] = (u[8] | 0x80) & 0xBF
+
+	r := make([]byte, 36)
+	r[8] = '-'
+	r[13] = '-'
+	r[18] = '-'
+	r[23] = '-'
+	hex.Encode(r, u[0:4])
+	hex.Encode(r[9:], u[4:6])
+	hex.Encode(r[14:], u[6:8])
+	hex.Encode(r[19:], u[8:10])
+	hex.Encode(r[24:], u[10:])
+
+	return string(r)
+}
--- a/connector/saml/saml_test.go
+++ b/connector/saml/saml_test.go
@ -0,0 +1,42 @@
+package saml
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+	"io/ioutil"
+	"testing"
+
+	sdig "github.com/russellhaering/goxmldsig"
+)
+
+func loadCert(ca string) (*x509.Certificate, error) {
+	data, err := ioutil.ReadFile(ca)
+	if err != nil {
+		return nil, err
+	}
+	block, _ := pem.Decode(data)
+	if block == nil {
+		return nil, errors.New("ca file didn't contain any PEM data")
+	}
+	return x509.ParseCertificate(block.Bytes)
+}
+
+func TestVerify(t *testing.T) {
+	cert, err := loadCert("testdata/okta-ca.pem")
+	if err != nil {
+		t.Fatal(err)
+	}
+	s := certStore{[]*x509.Certificate{cert}}
+
+	validator := sdig.NewDefaultValidationContext(s)
+
+	data, err := ioutil.ReadFile("testdata/okta-resp.xml")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := verify(validator, data); err != nil {
+		t.Fatal(err)
+	}
+}
--- a/connector/saml/testdata/okta-ca.pem
+++ b/connector/saml/testdata/okta-ca.pem
@ -0,0 +1,19 @@
+-----BEGIN CERTIFICATE-----
+MIIDpDCCAoygAwIBAgIGAVjgvNroMA0GCSqGSIb3DQEBBQUAMIGSMQswCQYDVQQGEwJVUzETMBEG
+A1UECAwKQ2FsaWZvcm5pYTEWMBQGA1UEBwwNU2FuIEZyYW5jaXNjbzENMAsGA1UECgwET2t0YTEU
+MBIGA1UECwwLU1NPUHJvdmlkZXIxEzARBgNVBAMMCmRldi05NjkyNDQxHDAaBgkqhkiG9w0BCQEW
+DWluZm9Ab2t0YS5jb20wHhcNMTYxMjA4MjMxOTIzWhcNMjYxMjA4MjMyMDIzWjCBkjELMAkGA1UE
+BhMCVVMxEzARBgNVBAgMCkNhbGlmb3JuaWExFjAUBgNVBAcMDVNhbiBGcmFuY2lzY28xDTALBgNV
+BAoMBE9rdGExFDASBgNVBAsMC1NTT1Byb3ZpZGVyMRMwEQYDVQQDDApkZXYtOTY5MjQ0MRwwGgYJ
+KoZIhvcNAQkBFg1pbmZvQG9rdGEuY29tMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA
+4dW2YlcXjZwnTmLnV7IOBq8hhrdbqlNwdjCHRyx1BizOk3RbVP56grgPdyWScTCPpJ6vZZ8rtrY0
+m1rwr+cxifNuQGKTlE33g2hReo/N9f3LFUMITlnnNH80Yium3SYuEqGeHLYerelXOnEKx6x+X5qD
+eg2DRW6I9/v/mfN2KAQEDqF9aSNlNFWZWmb52kukMv3tLWw0puaevicIZ/nZrW+D3CLDVVfWHeVt
+46EF2bkLdgbIJOU3GzLoolgBOCkydX9x6xTw6knwQaqYsRGflacw6571IzWEwjmd17uJXkarnhM1
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+7Yk1j4GV/135zLOlsaonq8zfsu05VfY5XydNPFEkyIVcegLa8RiqALyFf+FjY/wVyhXtARw7NBUo
+u/Jh63cVya/VEoP1SVa0XQLf/ial+XuwdBBL1yc+7o2XHOfluDaXw/v2FWYpZtICf3a39giGaNWp
+eCT4g2TDWM4Jf/X7/mRbLX9tQO7XRural1CXx8VIMcmbKNbUtQiO8yEtVQ+FJKOsl7KOSzkgqNiL
+rJy+Y0D9biLZVKp07KWAY2FPCEtCkBrvo8BhvWbxWMA8CVQNAiTylM27Pc6kbc64pNr7C1Jx1wuE
+mVy9Fgb4PA2N3hPeD7mBmGGp7CfDbGcy
+-----END CERTIFICATE-----
--- a/connector/saml/testdata/okta-resp.xml
+++ b/connector/saml/testdata/okta-resp.xml
@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="UTF-8"?><saml2p:Response xmlns:saml2p="urn:oasis:names:tc:SAML:2.0:protocol" Destination="http://localhost:5556/dex/callback" ID="id108965453120986171998428970" InResponseTo="_fd1b3ef9-ec09-44a7-a66b-0d39c250f6a0" IssueInstant="2016-12-20T22:18:23.771Z" Version="2.0"><saml2:Issuer xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" Format="urn:oasis:names:tc:SAML:2.0:nameid-format:entity">http://www.okta.com/exk91cb99lKkKSYoy0h7</saml2:Issuer><ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#"><ds:SignedInfo><ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/><ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/><ds:Reference URI="#id108965453120986171998428970"><ds:Transforms><ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/><ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/></ds:Transforms><ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><ds:DigestValue>Phu93l0D97JSMIYDZBdVeNLN0pwBVHhzUDWxbh4sc6g=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>M2gMHOmnMAFgh2apq/2jHwDYmisUkYMUqxrWkQJf3RHFotl4EeDlcqq/FzOboJc3NcbKBqQY3CWsWhWh5cNWHDgNneaahW4czww+9DCM0R/zz5c6GuMYFEh5df2sDn/dWk/jbKMiAMgPdKJ2x/+5Xk9q4axC52TdQrrbZtzAAAn4CgrT6Kf11qfMl5wpDarg3qPw7ANxWn2DKzCsvCkOIwM2+AXh+sEXmTvvZIQ0vpv098FH/ZTGt4sCwb1bmRZ3UZLhBcxVc/sjuEW/sQ6pbQHkjrXIR5bxXzGNUxYpcGjrp9HGF+In0BAc+Ds/A0H142e1rgtcX8LH2pbG8URJSQ==</ds:SignatureValue><ds:KeyInfo><ds:X509Data><ds:X509Certificate>MIIDpDCCAoygAwIBAgIGAVjgvNroMA0GCSqGSIb3DQEBBQUAMIGSMQswCQYDVQQGEwJVUzETMBEG
+A1UECAwKQ2FsaWZvcm5pYTEWMBQGA1UEBwwNU2FuIEZyYW5jaXNjbzENMAsGA1UECgwET2t0YTEU
+MBIGA1UECwwLU1NPUHJvdmlkZXIxEzARBgNVBAMMCmRldi05NjkyNDQxHDAaBgkqhkiG9w0BCQEW
+DWluZm9Ab2t0YS5jb20wHhcNMTYxMjA4MjMxOTIzWhcNMjYxMjA4MjMyMDIzWjCBkjELMAkGA1UE
+BhMCVVMxEzARBgNVBAgMCkNhbGlmb3JuaWExFjAUBgNVBAcMDVNhbiBGcmFuY2lzY28xDTALBgNV
+BAoMBE9rdGExFDASBgNVBAsMC1NTT1Byb3ZpZGVyMRMwEQYDVQQDDApkZXYtOTY5MjQ0MRwwGgYJ
+KoZIhvcNAQkBFg1pbmZvQG9rdGEuY29tMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA
+4dW2YlcXjZwnTmLnV7IOBq8hhrdbqlNwdjCHRyx1BizOk3RbVP56grgPdyWScTCPpJ6vZZ8rtrY0
+m1rwr+cxifNuQGKTlE33g2hReo/N9f3LFUMITlnnNH80Yium3SYuEqGeHLYerelXOnEKx6x+X5qD
+eg2DRW6I9/v/mfN2KAQEDqF9aSNlNFWZWmb52kukMv3tLWw0puaevicIZ/nZrW+D3CLDVVfWHeVt
+46EF2bkLdgbIJOU3GzLoolgBOCkydX9x6xTw6knwQaqYsRGflacw6571IzWEwjmd17uJXkarnhM1
+51pqwIoksTzycbjinIg6B1rNpGFDN7Ah+9EnVQIDAQABMA0GCSqGSIb3DQEBBQUAA4IBAQDQOtlj
+7Yk1j4GV/135zLOlsaonq8zfsu05VfY5XydNPFEkyIVcegLa8RiqALyFf+FjY/wVyhXtARw7NBUo
+u/Jh63cVya/VEoP1SVa0XQLf/ial+XuwdBBL1yc+7o2XHOfluDaXw/v2FWYpZtICf3a39giGaNWp
+eCT4g2TDWM4Jf/X7/mRbLX9tQO7XRural1CXx8VIMcmbKNbUtQiO8yEtVQ+FJKOsl7KOSzkgqNiL
+rJy+Y0D9biLZVKp07KWAY2FPCEtCkBrvo8BhvWbxWMA8CVQNAiTylM27Pc6kbc64pNr7C1Jx1wuE
+mVy9Fgb4PA2N3hPeD7mBmGGp7CfDbGcy</ds:X509Certificate></ds:X509Data></ds:KeyInfo></ds:Signature><saml2p:Status xmlns:saml2p="urn:oasis:names:tc:SAML:2.0:protocol"><saml2p:StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success"/></saml2p:Status><saml2:Assertion xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" ID="id10896545312129779529177535" IssueInstant="2016-12-20T22:18:23.771Z" Version="2.0"><saml2:Issuer Format="urn:oasis:names:tc:SAML:2.0:nameid-format:entity" xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">http://www.okta.com/exk91cb99lKkKSYoy0h7</saml2:Issuer><ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#"><ds:SignedInfo><ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/><ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/><ds:Reference URI="#id10896545312129779529177535"><ds:Transforms><ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/><ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/></ds:Transforms><ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><ds:DigestValue>ufwWUjecX6I/aQb4WW9P9ZMLG3C8hN6LaZyyb/EATIs=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>jKtNBzxAL67ssuzWkkbf0yzqRyZ51y2JjBQ9C6bW8io/JOYQB2v7Bix7Eu/RjJslO7OBqD+3tPrK7ZBOy2+LFuAh3cDNa3U5NhO0raLrn/2YoJXfjj3XX3hyQv6GVxo0EY1KJNXOzWxjp9RVDpHslPTIL1yDC/oy0Mlzxu6pXBEerz9J2/Caenq66Skb5/DAT8FvrJ2s1bxuMagShs3APhC1hD8mvktZ+ZcN8ujs2SebteGK4IoOCx+e8+v2CyycBv1l5l+v5I+D2HnbAw4LfvHnW4rZOJT2AvoI47p1YBK1qDsJutG3jUPKy4Yx5YF73Xi1oytr+rrHyx/lfFPd2A==</ds:SignatureValue><ds:KeyInfo><ds:X509Data><ds:X509Certificate>MIIDpDCCAoygAwIBAgIGAVjgvNroMA0GCSqGSIb3DQEBBQUAMIGSMQswCQYDVQQGEwJVUzETMBEG
+A1UECAwKQ2FsaWZvcm5pYTEWMBQGA1UEBwwNU2FuIEZyYW5jaXNjbzENMAsGA1UECgwET2t0YTEU
+MBIGA1UECwwLU1NPUHJvdmlkZXIxEzARBgNVBAMMCmRldi05NjkyNDQxHDAaBgkqhkiG9w0BCQEW
+DWluZm9Ab2t0YS5jb20wHhcNMTYxMjA4MjMxOTIzWhcNMjYxMjA4MjMyMDIzWjCBkjELMAkGA1UE
+BhMCVVMxEzARBgNVBAgMCkNhbGlmb3JuaWExFjAUBgNVBAcMDVNhbiBGcmFuY2lzY28xDTALBgNV
+BAoMBE9rdGExFDASBgNVBAsMC1NTT1Byb3ZpZGVyMRMwEQYDVQQDDApkZXYtOTY5MjQ0MRwwGgYJ
+KoZIhvcNAQkBFg1pbmZvQG9rdGEuY29tMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA
+4dW2YlcXjZwnTmLnV7IOBq8hhrdbqlNwdjCHRyx1BizOk3RbVP56grgPdyWScTCPpJ6vZZ8rtrY0
+m1rwr+cxifNuQGKTlE33g2hReo/N9f3LFUMITlnnNH80Yium3SYuEqGeHLYerelXOnEKx6x+X5qD
+eg2DRW6I9/v/mfN2KAQEDqF9aSNlNFWZWmb52kukMv3tLWw0puaevicIZ/nZrW+D3CLDVVfWHeVt
+46EF2bkLdgbIJOU3GzLoolgBOCkydX9x6xTw6knwQaqYsRGflacw6571IzWEwjmd17uJXkarnhM1
+51pqwIoksTzycbjinIg6B1rNpGFDN7Ah+9EnVQIDAQABMA0GCSqGSIb3DQEBBQUAA4IBAQDQOtlj
+7Yk1j4GV/135zLOlsaonq8zfsu05VfY5XydNPFEkyIVcegLa8RiqALyFf+FjY/wVyhXtARw7NBUo
+u/Jh63cVya/VEoP1SVa0XQLf/ial+XuwdBBL1yc+7o2XHOfluDaXw/v2FWYpZtICf3a39giGaNWp
+eCT4g2TDWM4Jf/X7/mRbLX9tQO7XRural1CXx8VIMcmbKNbUtQiO8yEtVQ+FJKOsl7KOSzkgqNiL
+rJy+Y0D9biLZVKp07KWAY2FPCEtCkBrvo8BhvWbxWMA8CVQNAiTylM27Pc6kbc64pNr7C1Jx1wuE
+mVy9Fgb4PA2N3hPeD7mBmGGp7CfDbGcy</ds:X509Certificate></ds:X509Data></ds:KeyInfo></ds:Signature><saml2:Subject xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion"><saml2:NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified">eric.chiang+okta@coreos.com</saml2:NameID><saml2:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer"><saml2:SubjectConfirmationData InResponseTo="_fd1b3ef9-ec09-44a7-a66b-0d39c250f6a0" NotOnOrAfter="2016-12-20T22:23:23.772Z" Recipient="http://localhost:5556/dex/callback"/></saml2:SubjectConfirmation></saml2:Subject><saml2:Conditions NotBefore="2016-12-20T22:13:23.772Z" NotOnOrAfter="2016-12-20T22:23:23.772Z" xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion"><saml2:AudienceRestriction><saml2:Audience>http://localhost:5556/dex/callback</saml2:Audience></saml2:AudienceRestriction></saml2:Conditions><saml2:AuthnStatement AuthnInstant="2016-12-20T22:18:23.771Z" SessionIndex="_fd1b3ef9-ec09-44a7-a66b-0d39c250f6a0" xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion"><saml2:AuthnContext><saml2:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport</saml2:AuthnContextClassRef></saml2:AuthnContext></saml2:AuthnStatement></saml2:Assertion></saml2p:Response>
--- a/connector/saml/types.go
+++ b/connector/saml/types.go
@ -0,0 +1,177 @@
+package saml
+
+import (
+	"encoding/xml"
+	"fmt"
+	"time"
+)
+
+const timeFormat = "2006-01-02T15:04:05Z"
+
+type xmlTime time.Time
+
+func (t xmlTime) MarshalXMLAttr(name xml.Name) (xml.Attr, error) {
+	return xml.Attr{
+		Name:  name,
+		Value: time.Time(t).UTC().Format(timeFormat),
+	}, nil
+}
+
+func (t *xmlTime) UnmarshalXMLAttr(attr xml.Attr) error {
+	got, err := time.Parse(timeFormat, attr.Value)
+	if err != nil {
+		return err
+	}
+	*t = xmlTime(got)
+	return nil
+}
+
+type samlVersion struct{}
+
+func (s samlVersion) MarshalXMLAttr(name xml.Name) (xml.Attr, error) {
+	return xml.Attr{
+		Name:  name,
+		Value: "2.0",
+	}, nil
+}
+
+func (s *samlVersion) UnmarshalXMLAttr(attr xml.Attr) error {
+	if attr.Value != "2.0" {
+		return fmt.Errorf(`saml version expected "2.0" got %q`, attr.Value)
+	}
+	return nil
+}
+
+type authnRequest struct {
+	XMLName xml.Name `xml:"urn:oasis:names:tc:SAML:2.0:protocol AuthnRequest"`
+
+	ID      string      `xml:"ID,attr"`
+	Version samlVersion `xml:"Version,attr"`
+
+	ProviderName string  `xml:"ProviderName,attr,omitempty"`
+	IssueInstant xmlTime `xml:"IssueInstant,attr,omitempty"`
+	Consent      bool    `xml:"Consent,attr,omitempty"`
+	Destination  string  `xml:"Destination,attr,omitempty"`
+
+	ForceAuthn      bool   `xml:"ForceAuthn,attr,omitempty"`
+	IsPassive       bool   `xml:"IsPassive,attr,omitempty"`
+	ProtocolBinding string `xml:"ProtocolBinding,attr,omitempty"`
+
+	Subject      *subject      `xml:"Subject,omitempty"`
+	Issuer       *issuer       `xml:"Issuer,omitempty"`
+	NameIDPolicy *nameIDPolicy `xml:"NameIDPolicy,omitempty"`
+
+	// TODO(ericchiang): Make this configurable and determine appropriate default values.
+	RequestAuthnContext *requestAuthnContext `xml:"RequestAuthnContext,omitempty"`
+}
+
+type subject struct {
+	XMLName xml.Name `xml:"urn:oasis:names:tc:SAML:2.0:assertion Subject"`
+
+	NameID *nameID `xml:"NameID,omitempty"`
+
+	// TODO(ericchiang): Do we need to deal with baseID?
+}
+
+type nameID struct {
+	XMLName xml.Name `xml:"urn:oasis:names:tc:SAML:2.0:assertion NameID"`
+
+	Format string `xml:"Format,omitempty"`
+	Value  string `xml:",chardata"`
+}
+
+type issuer struct {
+	XMLName xml.Name `xml:"urn:oasis:names:tc:SAML:2.0:assertion Issuer"`
+	Issuer  string   `xml:",chardata"`
+}
+
+type nameIDPolicy struct {
+	XMLName     xml.Name `xml:"urn:oasis:names:tc:SAML:2.0:protocol NameIDPolicy"`
+	AllowCreate bool     `xml:"AllowCreate,attr,omitempty"`
+	Format      string   `xml:"Format,attr,omitempty"`
+}
+
+type requestAuthnContext struct {
+	XMLName xml.Name `xml:"urn:oasis:names:tc:SAML:2.0:protocol RequestAuthnContext"`
+
+	AuthnContextClassRefs []authnContextClassRef
+}
+
+type authnContextClassRef struct {
+	XMLName xml.Name `xml:"urn:oasis:names:tc:SAML:2.0:protocol AuthnContextClassRef"`
+	Value   string   `xml:",chardata"`
+}
+
+type response struct {
+	XMLName xml.Name `xml:"urn:oasis:names:tc:SAML:2.0:protocol Response"`
+
+	ID      string      `xml:"ID,attr"`
+	Version samlVersion `xml:"Version,attr"`
+
+	Destination string `xml:"Destination,attr,omitempty"`
+
+	Issuer *issuer `xml:"Issuer,omitempty"`
+
+	// TODO(ericchiang): How do deal with multiple assertions?
+	Assertion *assertion `xml:"Assertion,omitempty"`
+}
+
+type assertion struct {
+	XMLName xml.Name `xml:"urn:oasis:names:tc:SAML:2.0:assertion Assertion"`
+
+	Version       samlVersion `xml:"Version,attr"`
+	ID            string      `xml:"ID,attr"`
+	IssueInstance xmlTime     `xml:"IssueInstance,attr"`
+
+	Issuer issuer `xml:"Issuer"`
+
+	Subject *subject `xml:"Subject,omitempty"`
+
+	AttributeStatement *attributeStatement `xml:"AttributeStatement,omitempty"`
+}
+
+type attributeStatement struct {
+	XMLName xml.Name `xml:"urn:oasis:names:tc:SAML:2.0:assertion AttributeStatement"`
+
+	Attributes []attribute `xml:"Attribute"`
+}
+
+func (a *attributeStatement) get(name string) (s string, ok bool) {
+	for _, attr := range a.Attributes {
+		if attr.Name == name {
+			ok = true
+			if len(attr.AttributeValues) > 0 {
+				return attr.AttributeValues[0].Value, true
+			}
+		}
+	}
+	return
+}
+
+func (a *attributeStatement) all(name string) (s []string, ok bool) {
+	for _, attr := range a.Attributes {
+		if attr.Name == name {
+			ok = true
+			for _, val := range attr.AttributeValues {
+				s = append(s, val.Value)
+			}
+		}
+	}
+	return
+}
+
+type attribute struct {
+	XMLName xml.Name `xml:"urn:oasis:names:tc:SAML:2.0:assertion Attribute"`
+
+	Name string `xml:"Name,attr"`
+
+	NameFormat   string `xml:"NameFormat,attr,omitempty"`
+	FriendlyName string `xml:"FriendlyName,attr,omitempty"`
+
+	AttributeValues []attributeValue `xml:"AttributeValue,omitempty"`
+}
+
+type attributeValue struct {
+	XMLName xml.Name `xml:"AttributeValue"`
+	Value   string   `xml:",chardata"`
+}
--- a/glide.lock
+++ b/glide.lock
@ -1,6 +1,8 @@
-hash: 4d7d84f09a330d27458fb821ae7ada243cfa825808dc7ab116db28a08f9166a2
-updated: 2017-01-08T19:23:40.352046548+01:00
+hash: 2f68b742168a81ebbe604be42801d37e9da71dff5aeb6b8f8e91ed81ff0edec0
+updated: 2017-01-09T14:51:09.514065012-08:00
 imports:
+- name: github.com/beevik/etree
+  version: 4cd0dd976db869f817248477718071a28e978df0
 - name: github.com/cockroachdb/cockroach-go
  version: 31611c0501c812f437d4861d87d117053967c955
  subpackages:
@ -26,6 +28,8 @@ imports:
  version: e7e23673cac3f529f49e22f94e4af6d12bb49dba
 - name: github.com/inconshreveable/mousetrap
  version: 76626ae9c91c4f2a10f34cad8ce83ea42c93bb75
+- name: github.com/jonboulle/clockwork
+  version: bcac9884e7502bb2b474c0339d889cb981a2f27f
 - name: github.com/kylelemons/godebug
  version: eadb3ce320cbab8393bea5ca17bebac3f78a021b
  subpackages:
@ -41,6 +45,8 @@ imports:
  version: c97913dcbd76de40b051a9b4cd827f7eaeb7a868
  subpackages:
  - cacheobject
+- name: github.com/russellhaering/goxmldsig
+  version: d9f653eb27ee8b145f7d5a45172e81a93def0860
 - name: github.com/Sirupsen/logrus
  version: d26492970760ca5d33129d2d799e34be5c4782eb
 - name: github.com/spf13/cobra
--- a/glide.yaml
+++ b/glide.yaml
@ -131,3 +131,11 @@ import:
  version: v0.11.0
 - package: golang.org/x/sys/unix
  version: 833a04a10549a95dc34458c195cbad61bbb6cb4d
+
+# XML signature validation for SAML connector
+- package: github.com/russellhaering/goxmldsig
+  version: d9f653eb27ee8b145f7d5a45172e81a93def0860
+- package: github.com/beevik/etree
+  version: 4cd0dd976db869f817248477718071a28e978df0
+- package: github.com/jonboulle/clockwork
+  version: bcac9884e7502bb2b474c0339d889cb981a2f27f
--- a/server/handlers.go
+++ b/server/handlers.go
@ -227,6 +227,31 @@ func (s *Server) handleConnectorLogin(w http.ResponseWriter, r *http.Request) {
 			if err := s.templates.password(w, authReqID, r.URL.String(), "", false); err != nil {
 				s.logger.Errorf("Server template error: %v", err)
 			}
+		case connector.SAMLConnector:
+			action, value, err := conn.POSTData(scopes)
+			if err != nil {
+				s.logger.Errorf("Creating SAML data: %v", err)
+				s.renderError(w, http.StatusInternalServerError, "Connector Login Error")
+				return
+			}
+
+			// TODO(ericchiang): Don't inline this.
+			fmt.Fprintf(w, `<!DOCTYPE html>
+			  <html lang="en">
+			  <head>
+			    <meta http-equiv="content-type" content="text/html; charset=utf-8">
+			    <title>SAML login</title>
+			  </head>
+			  <body>
+			    <form method="post" action="%s" >
+				    <input type="hidden" name="SAMLRequest" value="%s" />
+				    <input type="hidden" name="RelayState" value="%s" />
+			    </form>
+				<script>
+				    document.forms[0].submit();
+				</script>
+			  </body>
+			  </html>`, action, value, authReqID)
 		default:
 			s.renderError(w, http.StatusBadRequest, "Requested resource does not exist.")
 		}
@ -266,20 +291,24 @@ func (s *Server) handleConnectorLogin(w http.ResponseWriter, r *http.Request) {
 }

 func (s *Server) handleConnectorCallback(w http.ResponseWriter, r *http.Request) {
-	// SAML redirect bindings use the "RelayState" URL query field. When we support
-	// SAML, we'll have to check that field too and possibly let callback connectors
-	// indicate which field is used to determine the state.
-	//
-	// See:
-	//   https://docs.oasis-open.org/security/saml/v2.0/saml-bindings-2.0-os.pdf
-	//   Section: "3.4.3 RelayState"
-	state := r.URL.Query().Get("state")
-	if state == "" {
-		s.renderError(w, http.StatusBadRequest, "User session error.")
+	var authID string
+	switch r.Method {
+	case "GET": // OAuth2 callback
+		if authID = r.URL.Query().Get("state"); authID == "" {
+			s.renderError(w, http.StatusBadRequest, "User session error.")
+			return
+		}
+	case "POST": // SAML POST binding
+		if authID = r.PostFormValue("RelayState"); authID == "" {
+			s.renderError(w, http.StatusBadRequest, "User session error.")
+			return
+		}
+	default:
+		s.renderError(w, http.StatusBadRequest, "Method not supported")
 		return
 	}

-	authReq, err := s.storage.GetAuthRequest(state)
+	authReq, err := s.storage.GetAuthRequest(authID)
 	if err != nil {
 		if err == storage.ErrNotFound {
 			s.logger.Errorf("Invalid 'state' parameter provided: %v", err)
@ -296,13 +325,28 @@ func (s *Server) handleConnectorCallback(w http.ResponseWriter, r *http.Request)
 		s.renderError(w, http.StatusInternalServerError, "Requested resource does not exist.")
 		return
 	}
-	callbackConnector, ok := conn.Connector.(connector.CallbackConnector)
-	if !ok {
+
+	var identity connector.Identity
+	switch conn := conn.Connector.(type) {
+	case connector.CallbackConnector:
+		if r.Method != "GET" {
+			s.logger.Errorf("SAML request mapped to OAuth2 connector")
+			s.renderError(w, http.StatusBadRequest, "Invalid request")
+			return
+		}
+		identity, err = conn.HandleCallback(parseScopes(authReq.Scopes), r)
+	case connector.SAMLConnector:
+		if r.Method != "POST" {
+			s.logger.Errorf("OAuth2 request mapped to SAML connector")
+			s.renderError(w, http.StatusBadRequest, "Invalid request")
+			return
+		}
+		identity, err = conn.HandlePOST(parseScopes(authReq.Scopes), r.PostFormValue("SAMLResponse"))
+	default:
 		s.renderError(w, http.StatusInternalServerError, "Requested resource does not exist.")
 		return
 	}

-	identity, err := callbackConnector.HandleCallback(parseScopes(authReq.Scopes), r)
 	if err != nil {
 		s.logger.Errorf("Failed to authenticate: %v", err)
 		s.renderError(w, http.StatusInternalServerError, "Failed to return user's identity.")
--- a/vendor/github.com/beevik/etree/LICENSE
+++ b/vendor/github.com/beevik/etree/LICENSE
@ -0,0 +1,24 @@
+Copyright 2015 Brett Vickers. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+   1. Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+   2. Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY COPYRIGHT HOLDER ``AS IS'' AND ANY
+EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER OR
+CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
--- a/vendor/github.com/beevik/etree/etree.go
+++ b/vendor/github.com/beevik/etree/etree.go
@ -0,0 +1,938 @@
+// Copyright 2015 Brett Vickers.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package etree provides XML services through an Element Tree
+// abstraction.
+package etree
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/xml"
+	"errors"
+	"io"
+	"os"
+	"strings"
+)
+
+const (
+	// NoIndent is used with Indent to disable all indenting.
+	NoIndent = -1
+)
+
+// ErrXML is returned when XML parsing fails due to incorrect formatting.
+var ErrXML = errors.New("etree: invalid XML format")
+
+// ReadSettings allow for changing the default behavior of the ReadFrom*
+// methods.
+type ReadSettings struct {
+	// CharsetReader to be passed to standard xml.Decoder. Default: nil.
+	CharsetReader func(charset string, input io.Reader) (io.Reader, error)
+}
+
+// newReadSettings creates a default ReadSettings record.
+func newReadSettings() ReadSettings {
+	return ReadSettings{}
+}
+
+// WriteSettings allow for changing the serialization behavior of the WriteTo*
+// methods.
+type WriteSettings struct {
+	// CanonicalEndTags forces the production of XML end tags, even for
+	// elements that have no child elements. Default: false.
+	CanonicalEndTags bool
+
+	// CanonicalText forces the production of XML character references for
+	// text data characters &, <, and >. If false, XML character references
+	// are also produced for " and '. Default: false.
+	CanonicalText bool
+
+	// CanonicalAttrVal forces the production of XML character references for
+	// attribute value characters &, < and ". If false, XML character
+	// references are also produced for > and '. Default: false.
+	CanonicalAttrVal bool
+}
+
+// newWriteSettings creates a default WriteSettings record.
+func newWriteSettings() WriteSettings {
+	return WriteSettings{
+		CanonicalEndTags: false,
+		CanonicalText:    false,
+		CanonicalAttrVal: false,
+	}
+}
+
+// A Token is an empty interface that represents an Element, CharData,
+// Comment, Directive, or ProcInst.
+type Token interface {
+	Parent() *Element
+	dup(parent *Element) Token
+	setParent(parent *Element)
+	writeTo(w *bufio.Writer, s *WriteSettings)
+}
+
+// A Document is a container holding a complete XML hierarchy. Its embedded
+// element contains zero or more children, one of which is usually the root
+// element.  The embedded element may include other children such as
+// processing instructions or BOM CharData tokens.
+type Document struct {
+	Element
+	ReadSettings  ReadSettings
+	WriteSettings WriteSettings
+}
+
+// An Element represents an XML element, its attributes, and its child tokens.
+type Element struct {
+	Space, Tag string   // namespace and tag
+	Attr       []Attr   // key-value attribute pairs
+	Child      []Token  // child tokens (elements, comments, etc.)
+	parent     *Element // parent element
+}
+
+// An Attr represents a key-value attribute of an XML element.
+type Attr struct {
+	Space, Key string // The attribute's namespace and key
+	Value      string // The attribute value string
+}
+
+// CharData represents character data within XML.
+type CharData struct {
+	Data       string
+	parent     *Element
+	whitespace bool
+}
+
+// A Comment represents an XML comment.
+type Comment struct {
+	Data   string
+	parent *Element
+}
+
+// A Directive represents an XML directive.
+type Directive struct {
+	Data   string
+	parent *Element
+}
+
+// A ProcInst represents an XML processing instruction.
+type ProcInst struct {
+	Target string
+	Inst   string
+	parent *Element
+}
+
+// NewDocument creates an XML document without a root element.
+func NewDocument() *Document {
+	return &Document{
+		Element{Child: make([]Token, 0)},
+		newReadSettings(),
+		newWriteSettings(),
+	}
+}
+
+// Copy returns a recursive, deep copy of the document.
+func (d *Document) Copy() *Document {
+	return &Document{*(d.dup(nil).(*Element)), d.ReadSettings, d.WriteSettings}
+}
+
+// Root returns the root element of the document, or nil if there is no root
+// element.
+func (d *Document) Root() *Element {
+	for _, t := range d.Child {
+		if c, ok := t.(*Element); ok {
+			return c
+		}
+	}
+	return nil
+}
+
+// SetRoot replaces the document's root element with e. If the document
+// already has a root when this function is called, then the document's
+// original root is unbound first. If the element e is bound to another
+// document (or to another element within a document), then it is unbound
+// first.
+func (d *Document) SetRoot(e *Element) {
+	if e.parent != nil {
+		e.parent.RemoveChild(e)
+	}
+	e.setParent(&d.Element)
+
+	for i, t := range d.Child {
+		if _, ok := t.(*Element); ok {
+			t.setParent(nil)
+			d.Child[i] = e
+			return
+		}
+	}
+	d.Child = append(d.Child, e)
+}
+
+// ReadFrom reads XML from the reader r into the document d. It returns the
+// number of bytes read and any error encountered.
+func (d *Document) ReadFrom(r io.Reader) (n int64, err error) {
+	return d.Element.readFrom(r, d.ReadSettings.CharsetReader)
+}
+
+// ReadFromFile reads XML from the string s into the document d.
+func (d *Document) ReadFromFile(filename string) error {
+	f, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = d.ReadFrom(f)
+	return err
+}
+
+// ReadFromBytes reads XML from the byte slice b into the document d.
+func (d *Document) ReadFromBytes(b []byte) error {
+	_, err := d.ReadFrom(bytes.NewReader(b))
+	return err
+}
+
+// ReadFromString reads XML from the string s into the document d.
+func (d *Document) ReadFromString(s string) error {
+	_, err := d.ReadFrom(strings.NewReader(s))
+	return err
+}
+
+// WriteTo serializes an XML document into the writer w. It
+// returns the number of bytes written and any error encountered.
+func (d *Document) WriteTo(w io.Writer) (n int64, err error) {
+	cw := newCountWriter(w)
+	b := bufio.NewWriter(cw)
+	for _, c := range d.Child {
+		c.writeTo(b, &d.WriteSettings)
+	}
+	err, n = b.Flush(), cw.bytes
+	return
+}
+
+// WriteToFile serializes an XML document into the file named
+// filename.
+func (d *Document) WriteToFile(filename string) error {
+	f, err := os.Create(filename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = d.WriteTo(f)
+	return err
+}
+
+// WriteToBytes serializes the XML document into a slice of
+// bytes.
+func (d *Document) WriteToBytes() (b []byte, err error) {
+	var buf bytes.Buffer
+	if _, err = d.WriteTo(&buf); err != nil {
+		return
+	}
+	return buf.Bytes(), nil
+}
+
+// WriteToString serializes the XML document into a string.
+func (d *Document) WriteToString() (s string, err error) {
+	var b []byte
+	if b, err = d.WriteToBytes(); err != nil {
+		return
+	}
+	return string(b), nil
+}
+
+type indentFunc func(depth int) string
+
+// Indent modifies the document's element tree by inserting CharData entities
+// containing carriage returns and indentation. The amount of indentation per
+// depth level is given as spaces. Pass etree.NoIndent for spaces if you want
+// no indentation at all.
+func (d *Document) Indent(spaces int) {
+	var indent indentFunc
+	switch {
+	case spaces < 0:
+		indent = func(depth int) string { return "" }
+	default:
+		indent = func(depth int) string { return crIndent(depth*spaces, crsp) }
+	}
+	d.Element.indent(0, indent)
+}
+
+// IndentTabs modifies the document's element tree by inserting CharData
+// entities containing carriage returns and tabs for indentation.  One tab is
+// used per indentation level.
+func (d *Document) IndentTabs() {
+	indent := func(depth int) string { return crIndent(depth, crtab) }
+	d.Element.indent(0, indent)
+}
+
+// NewElement creates an unparented element with the specified tag. The tag
+// may be prefixed by a namespace and a colon.
+func NewElement(tag string) *Element {
+	space, stag := spaceDecompose(tag)
+	return newElement(space, stag, nil)
+}
+
+// newElement is a helper function that creates an element and binds it to
+// a parent element if possible.
+func newElement(space, tag string, parent *Element) *Element {
+	e := &Element{
+		Space:  space,
+		Tag:    tag,
+		Attr:   make([]Attr, 0),
+		Child:  make([]Token, 0),
+		parent: parent,
+	}
+	if parent != nil {
+		parent.addChild(e)
+	}
+	return e
+}
+
+// Copy creates a recursive, deep copy of the element and all its attributes
+// and children. The returned element has no parent but can be parented to a
+// another element using AddElement, or to a document using SetRoot.
+func (e *Element) Copy() *Element {
+	var parent *Element
+	return e.dup(parent).(*Element)
+}
+
+// Text returns the characters immediately following the element's
+// opening tag.
+func (e *Element) Text() string {
+	if len(e.Child) == 0 {
+		return ""
+	}
+	if cd, ok := e.Child[0].(*CharData); ok {
+		return cd.Data
+	}
+	return ""
+}
+
+// SetText replaces an element's subsidiary CharData text with a new string.
+func (e *Element) SetText(text string) {
+	if len(e.Child) > 0 {
+		if cd, ok := e.Child[0].(*CharData); ok {
+			cd.Data = text
+			return
+		}
+	}
+	cd := newCharData(text, false, e)
+	copy(e.Child[1:], e.Child[0:])
+	e.Child[0] = cd
+}
+
+// CreateElement creates an element with the specified tag and adds it as the
+// last child element of the element e. The tag may be prefixed by a namespace
+// and a colon.
+func (e *Element) CreateElement(tag string) *Element {
+	space, stag := spaceDecompose(tag)
+	return newElement(space, stag, e)
+}
+
+// AddChild adds the token t as the last child of element e. If token t was
+// already the child of another element, it is first removed from its current
+// parent element.
+func (e *Element) AddChild(t Token) {
+	if t.Parent() != nil {
+		t.Parent().RemoveChild(t)
+	}
+	t.setParent(e)
+	e.addChild(t)
+}
+
+// InsertChild inserts the token t before e's existing child token ex. If ex
+// is nil (or if ex is not a child of e), then t is added to the end of e's
+// child token list. If token t was already the child of another element, it
+// is first removed from its current parent element.
+func (e *Element) InsertChild(ex Token, t Token) {
+	if t.Parent() != nil {
+		t.Parent().RemoveChild(t)
+	}
+	t.setParent(e)
+
+	for i, c := range e.Child {
+		if c == ex {
+			e.Child = append(e.Child, nil)
+			copy(e.Child[i+1:], e.Child[i:])
+			e.Child[i] = t
+			return
+		}
+	}
+	e.addChild(t)
+}
+
+// RemoveChild attempts to remove the token t from element e's list of
+// children. If the token t is a child of e, then it is returned. Otherwise,
+// nil is returned.
+func (e *Element) RemoveChild(t Token) Token {
+	for i, c := range e.Child {
+		if c == t {
+			e.Child = append(e.Child[:i], e.Child[i+1:]...)
+			c.setParent(nil)
+			return t
+		}
+	}
+	return nil
+}
+
+// ReadFrom reads XML from the reader r and stores the result as a new child
+// of element e.
+func (e *Element) readFrom(ri io.Reader, charsetReader func(charset string, input io.Reader) (io.Reader, error)) (n int64, err error) {
+	r := newCountReader(ri)
+	dec := xml.NewDecoder(r)
+	dec.CharsetReader = charsetReader
+	var stack stack
+	stack.push(e)
+	for {
+		t, err := dec.RawToken()
+		switch {
+		case err == io.EOF:
+			return r.bytes, nil
+		case err != nil:
+			return r.bytes, err
+		case stack.empty():
+			return r.bytes, ErrXML
+		}
+
+		top := stack.peek().(*Element)
+
+		switch t := t.(type) {
+		case xml.StartElement:
+			e := newElement(t.Name.Space, t.Name.Local, top)
+			for _, a := range t.Attr {
+				e.createAttr(a.Name.Space, a.Name.Local, a.Value)
+			}
+			stack.push(e)
+		case xml.EndElement:
+			stack.pop()
+		case xml.CharData:
+			data := string(t)
+			newCharData(data, isWhitespace(data), top)
+		case xml.Comment:
+			newComment(string(t), top)
+		case xml.Directive:
+			newDirective(string(t), top)
+		case xml.ProcInst:
+			newProcInst(t.Target, string(t.Inst), top)
+		}
+	}
+}
+
+// SelectAttr finds an element attribute matching the requested key and
+// returns it if found. The key may be prefixed by a namespace and a colon.
+func (e *Element) SelectAttr(key string) *Attr {
+	space, skey := spaceDecompose(key)
+	for i, a := range e.Attr {
+		if spaceMatch(space, a.Space) && skey == a.Key {
+			return &e.Attr[i]
+		}
+	}
+	return nil
+}
+
+// SelectAttrValue finds an element attribute matching the requested key and
+// returns its value if found. The key may be prefixed by a namespace and a
+// colon. If the key is not found, the dflt value is returned instead.
+func (e *Element) SelectAttrValue(key, dflt string) string {
+	space, skey := spaceDecompose(key)
+	for _, a := range e.Attr {
+		if spaceMatch(space, a.Space) && skey == a.Key {
+			return a.Value
+		}
+	}
+	return dflt
+}
+
+// ChildElements returns all elements that are children of element e.
+func (e *Element) ChildElements() []*Element {
+	var elements []*Element
+	for _, t := range e.Child {
+		if c, ok := t.(*Element); ok {
+			elements = append(elements, c)
+		}
+	}
+	return elements
+}
+
+// SelectElement returns the first child element with the given tag. The tag
+// may be prefixed by a namespace and a colon.
+func (e *Element) SelectElement(tag string) *Element {
+	space, stag := spaceDecompose(tag)
+	for _, t := range e.Child {
+		if c, ok := t.(*Element); ok && spaceMatch(space, c.Space) && stag == c.Tag {
+			return c
+		}
+	}
+	return nil
+}
+
+// SelectElements returns a slice of all child elements with the given tag.
+// The tag may be prefixed by a namespace and a colon.
+func (e *Element) SelectElements(tag string) []*Element {
+	space, stag := spaceDecompose(tag)
+	var elements []*Element
+	for _, t := range e.Child {
+		if c, ok := t.(*Element); ok && spaceMatch(space, c.Space) && stag == c.Tag {
+			elements = append(elements, c)
+		}
+	}
+	return elements
+}
+
+// FindElement returns the first element matched by the XPath-like path
+// string. Panics if an invalid path string is supplied.
+func (e *Element) FindElement(path string) *Element {
+	return e.FindElementPath(MustCompilePath(path))
+}
+
+// FindElementPath returns the first element matched by the XPath-like path
+// string.
+func (e *Element) FindElementPath(path Path) *Element {
+	p := newPather()
+	elements := p.traverse(e, path)
+	switch {
+	case len(elements) > 0:
+		return elements[0]
+	default:
+		return nil
+	}
+}
+
+// FindElements returns a slice of elements matched by the XPath-like path
+// string. Panics if an invalid path string is supplied.
+func (e *Element) FindElements(path string) []*Element {
+	return e.FindElementsPath(MustCompilePath(path))
+}
+
+// FindElementsPath returns a slice of elements matched by the Path object.
+func (e *Element) FindElementsPath(path Path) []*Element {
+	p := newPather()
+	return p.traverse(e, path)
+}
+
+// indent recursively inserts proper indentation between an
+// XML element's child tokens.
+func (e *Element) indent(depth int, indent indentFunc) {
+	e.stripIndent()
+	n := len(e.Child)
+	if n == 0 {
+		return
+	}
+
+	oldChild := e.Child
+	e.Child = make([]Token, 0, n*2+1)
+	isCharData, firstNonCharData := false, true
+	for _, c := range oldChild {
+
+		// Insert CR+indent before child if it's not character data.
+		// Exceptions: when it's the first non-character-data child, or when
+		// the child is at root depth.
+		_, isCharData = c.(*CharData)
+		if !isCharData {
+			if !firstNonCharData || depth > 0 {
+				newCharData(indent(depth), true, e)
+			}
+			firstNonCharData = false
+		}
+
+		e.addChild(c)
+
+		// Recursively process child elements.
+		if ce, ok := c.(*Element); ok {
+			ce.indent(depth+1, indent)
+		}
+	}
+
+	// Insert CR+indent before the last child.
+	if !isCharData {
+		if !firstNonCharData || depth > 0 {
+			newCharData(indent(depth-1), true, e)
+		}
+	}
+}
+
+// stripIndent removes any previously inserted indentation.
+func (e *Element) stripIndent() {
+	// Count the number of non-indent child tokens
+	n := len(e.Child)
+	for _, c := range e.Child {
+		if cd, ok := c.(*CharData); ok && cd.whitespace {
+			n--
+		}
+	}
+	if n == len(e.Child) {
+		return
+	}
+
+	// Strip out indent CharData
+	newChild := make([]Token, n)
+	j := 0
+	for _, c := range e.Child {
+		if cd, ok := c.(*CharData); ok && cd.whitespace {
+			continue
+		}
+		newChild[j] = c
+		j++
+	}
+	e.Child = newChild
+}
+
+// dup duplicates the element.
+func (e *Element) dup(parent *Element) Token {
+	ne := &Element{
+		Space:  e.Space,
+		Tag:    e.Tag,
+		Attr:   make([]Attr, len(e.Attr)),
+		Child:  make([]Token, len(e.Child)),
+		parent: parent,
+	}
+	for i, t := range e.Child {
+		ne.Child[i] = t.dup(ne)
+	}
+	for i, a := range e.Attr {
+		ne.Attr[i] = a
+	}
+	return ne
+}
+
+// Parent returns the element token's parent element, or nil if it has no
+// parent.
+func (e *Element) Parent() *Element {
+	return e.parent
+}
+
+// setParent replaces the element token's parent.
+func (e *Element) setParent(parent *Element) {
+	e.parent = parent
+}
+
+// writeTo serializes the element to the writer w.
+func (e *Element) writeTo(w *bufio.Writer, s *WriteSettings) {
+	w.WriteByte('<')
+	if e.Space != "" {
+		w.WriteString(e.Space)
+		w.WriteByte(':')
+	}
+	w.WriteString(e.Tag)
+	for _, a := range e.Attr {
+		w.WriteByte(' ')
+		a.writeTo(w, s)
+	}
+	if len(e.Child) > 0 {
+		w.WriteString(">")
+		for _, c := range e.Child {
+			c.writeTo(w, s)
+		}
+		w.Write([]byte{'<', '/'})
+		if e.Space != "" {
+			w.WriteString(e.Space)
+			w.WriteByte(':')
+		}
+		w.WriteString(e.Tag)
+		w.WriteByte('>')
+	} else {
+		if s.CanonicalEndTags {
+			w.Write([]byte{'>', '<', '/'})
+			if e.Space != "" {
+				w.WriteString(e.Space)
+				w.WriteByte(':')
+			}
+			w.WriteString(e.Tag)
+			w.WriteByte('>')
+		} else {
+			w.Write([]byte{'/', '>'})
+		}
+	}
+}
+
+// addChild adds a child token to the element e.
+func (e *Element) addChild(t Token) {
+	e.Child = append(e.Child, t)
+}
+
+// CreateAttr creates an attribute and adds it to element e. The key may be
+// prefixed by a namespace and a colon. If an attribute with the key already
+// exists, its value is replaced.
+func (e *Element) CreateAttr(key, value string) *Attr {
+	space, skey := spaceDecompose(key)
+	return e.createAttr(space, skey, value)
+}
+
+// createAttr is a helper function that creates attributes.
+func (e *Element) createAttr(space, key, value string) *Attr {
+	for i, a := range e.Attr {
+		if space == a.Space && key == a.Key {
+			e.Attr[i].Value = value
+			return &e.Attr[i]
+		}
+	}
+	a := Attr{space, key, value}
+	e.Attr = append(e.Attr, a)
+	return &e.Attr[len(e.Attr)-1]
+}
+
+// RemoveAttr removes and returns the first attribute of the element whose key
+// matches the given key. The key may be prefixed by a namespace and a colon.
+// If an equal attribute does not exist, nil is returned.
+func (e *Element) RemoveAttr(key string) *Attr {
+	space, skey := spaceDecompose(key)
+	for i, a := range e.Attr {
+		if space == a.Space && skey == a.Key {
+			e.Attr = append(e.Attr[0:i], e.Attr[i+1:]...)
+			return &a
+		}
+	}
+	return nil
+}
+
+var xmlReplacerNormal = strings.NewReplacer(
+	"&", "&amp;",
+	"<", "&lt;",
+	">", "&gt;",
+	"'", "&apos;",
+	`"`, "&quot;",
+)
+
+var xmlReplacerCanonicalText = strings.NewReplacer(
+	"&", "&amp;",
+	"<", "&lt;",
+	">", "&gt;",
+	"\r", "&#xD;",
+)
+
+var xmlReplacerCanonicalAttrVal = strings.NewReplacer(
+	"&", "&amp;",
+	"<", "&lt;",
+	`"`, "&quot;",
+	"\t", "&#x9;",
+	"\n", "&#xA;",
+	"\r", "&#xD;",
+)
+
+// writeTo serializes the attribute to the writer.
+func (a *Attr) writeTo(w *bufio.Writer, s *WriteSettings) {
+	if a.Space != "" {
+		w.WriteString(a.Space)
+		w.WriteByte(':')
+	}
+	w.WriteString(a.Key)
+	w.WriteString(`="`)
+	var r *strings.Replacer
+	if s.CanonicalAttrVal {
+		r = xmlReplacerCanonicalAttrVal
+	} else {
+		r = xmlReplacerNormal
+	}
+	w.WriteString(r.Replace(a.Value))
+	w.WriteByte('"')
+}
+
+// NewCharData creates a parentless XML character data entity.
+func NewCharData(data string) *CharData {
+	return newCharData(data, false, nil)
+}
+
+// newCharData creates an XML character data entity and binds it to a parent
+// element. If parent is nil, the CharData token remains unbound.
+func newCharData(data string, whitespace bool, parent *Element) *CharData {
+	c := &CharData{
+		Data:       data,
+		whitespace: whitespace,
+		parent:     parent,
+	}
+	if parent != nil {
+		parent.addChild(c)
+	}
+	return c
+}
+
+// CreateCharData creates an XML character data entity and adds it as a child
+// of element e.
+func (e *Element) CreateCharData(data string) *CharData {
+	return newCharData(data, false, e)
+}
+
+// dup duplicates the character data.
+func (c *CharData) dup(parent *Element) Token {
+	return &CharData{
+		Data:       c.Data,
+		whitespace: c.whitespace,
+		parent:     parent,
+	}
+}
+
+// Parent returns the character data token's parent element, or nil if it has
+// no parent.
+func (c *CharData) Parent() *Element {
+	return c.parent
+}
+
+// setParent replaces the character data token's parent.
+func (c *CharData) setParent(parent *Element) {
+	c.parent = parent
+}
+
+// writeTo serializes the character data entity to the writer.
+func (c *CharData) writeTo(w *bufio.Writer, s *WriteSettings) {
+	var r *strings.Replacer
+	if s.CanonicalText {
+		r = xmlReplacerCanonicalText
+	} else {
+		r = xmlReplacerNormal
+	}
+	w.WriteString(r.Replace(c.Data))
+}
+
+// NewComment creates a parentless XML comment.
+func NewComment(comment string) *Comment {
+	return newComment(comment, nil)
+}
+
+// NewComment creates an XML comment and binds it to a parent element. If
+// parent is nil, the Comment remains unbound.
+func newComment(comment string, parent *Element) *Comment {
+	c := &Comment{
+		Data:   comment,
+		parent: parent,
+	}
+	if parent != nil {
+		parent.addChild(c)
+	}
+	return c
+}
+
+// CreateComment creates an XML comment and adds it as a child of element e.
+func (e *Element) CreateComment(comment string) *Comment {
+	return newComment(comment, e)
+}
+
+// dup duplicates the comment.
+func (c *Comment) dup(parent *Element) Token {
+	return &Comment{
+		Data:   c.Data,
+		parent: parent,
+	}
+}
+
+// Parent returns comment token's parent element, or nil if it has no parent.
+func (c *Comment) Parent() *Element {
+	return c.parent
+}
+
+// setParent replaces the comment token's parent.
+func (c *Comment) setParent(parent *Element) {
+	c.parent = parent
+}
+
+// writeTo serialies the comment to the writer.
+func (c *Comment) writeTo(w *bufio.Writer, s *WriteSettings) {
+	w.WriteString("<!--")
+	w.WriteString(c.Data)
+	w.WriteString("-->")
+}
+
+// NewDirective creates a parentless XML directive.
+func NewDirective(data string) *Directive {
+	return newDirective(data, nil)
+}
+
+// newDirective creates an XML directive and binds it to a parent element. If
+// parent is nil, the Directive remains unbound.
+func newDirective(data string, parent *Element) *Directive {
+	d := &Directive{
+		Data:   data,
+		parent: parent,
+	}
+	if parent != nil {
+		parent.addChild(d)
+	}
+	return d
+}
+
+// CreateDirective creates an XML directive and adds it as the last child of
+// element e.
+func (e *Element) CreateDirective(data string) *Directive {
+	return newDirective(data, e)
+}
+
+// dup duplicates the directive.
+func (d *Directive) dup(parent *Element) Token {
+	return &Directive{
+		Data:   d.Data,
+		parent: parent,
+	}
+}
+
+// Parent returns directive token's parent element, or nil if it has no
+// parent.
+func (d *Directive) Parent() *Element {
+	return d.parent
+}
+
+// setParent replaces the directive token's parent.
+func (d *Directive) setParent(parent *Element) {
+	d.parent = parent
+}
+
+// writeTo serializes the XML directive to the writer.
+func (d *Directive) writeTo(w *bufio.Writer, s *WriteSettings) {
+	w.WriteString("<!")
+	w.WriteString(d.Data)
+	w.WriteString(">")
+}
+
+// NewProcInst creates a parentless XML processing instruction.
+func NewProcInst(target, inst string) *ProcInst {
+	return newProcInst(target, inst, nil)
+}
+
+// newProcInst creates an XML processing instruction and binds it to a parent
+// element. If parent is nil, the ProcInst remains unbound.
+func newProcInst(target, inst string, parent *Element) *ProcInst {
+	p := &ProcInst{
+		Target: target,
+		Inst:   inst,
+		parent: parent,
+	}
+	if parent != nil {
+		parent.addChild(p)
+	}
+	return p
+}
+
+// CreateProcInst creates a processing instruction and adds it as a child of
+// element e.
+func (e *Element) CreateProcInst(target, inst string) *ProcInst {
+	return newProcInst(target, inst, e)
+}
+
+// dup duplicates the procinst.
+func (p *ProcInst) dup(parent *Element) Token {
+	return &ProcInst{
+		Target: p.Target,
+		Inst:   p.Inst,
+		parent: parent,
+	}
+}
+
+// Parent returns processing instruction token's parent element, or nil if it
+// has no parent.
+func (p *ProcInst) Parent() *Element {
+	return p.parent
+}
+
+// setParent replaces the processing instruction token's parent.
+func (p *ProcInst) setParent(parent *Element) {
+	p.parent = parent
+}
+
+// writeTo serializes the processing instruction to the writer.
+func (p *ProcInst) writeTo(w *bufio.Writer, s *WriteSettings) {
+	w.WriteString("<?")
+	w.WriteString(p.Target)
+	if p.Inst != "" {
+		w.WriteByte(' ')
+		w.WriteString(p.Inst)
+	}
+	w.WriteString("?>")
+}
--- a/vendor/github.com/beevik/etree/helpers.go
+++ b/vendor/github.com/beevik/etree/helpers.go
@ -0,0 +1,188 @@
+// Copyright 2015 Brett Vickers.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package etree
+
+import (
+	"io"
+	"strings"
+)
+
+// A simple stack
+type stack struct {
+	data []interface{}
+}
+
+func (s *stack) empty() bool {
+	return len(s.data) == 0
+}
+
+func (s *stack) push(value interface{}) {
+	s.data = append(s.data, value)
+}
+
+func (s *stack) pop() interface{} {
+	value := s.data[len(s.data)-1]
+	s.data[len(s.data)-1] = nil
+	s.data = s.data[:len(s.data)-1]
+	return value
+}
+
+func (s *stack) peek() interface{} {
+	return s.data[len(s.data)-1]
+}
+
+// A fifo is a simple first-in-first-out queue.
+type fifo struct {
+	data       []interface{}
+	head, tail int
+}
+
+func (f *fifo) add(value interface{}) {
+	if f.len()+1 >= len(f.data) {
+		f.grow()
+	}
+	f.data[f.tail] = value
+	if f.tail++; f.tail == len(f.data) {
+		f.tail = 0
+	}
+}
+
+func (f *fifo) remove() interface{} {
+	value := f.data[f.head]
+	f.data[f.head] = nil
+	if f.head++; f.head == len(f.data) {
+		f.head = 0
+	}
+	return value
+}
+
+func (f *fifo) len() int {
+	if f.tail >= f.head {
+		return f.tail - f.head
+	}
+	return len(f.data) - f.head + f.tail
+}
+
+func (f *fifo) grow() {
+	c := len(f.data) * 2
+	if c == 0 {
+		c = 4
+	}
+	buf, count := make([]interface{}, c), f.len()
+	if f.tail >= f.head {
+		copy(buf[0:count], f.data[f.head:f.tail])
+	} else {
+		hindex := len(f.data) - f.head
+		copy(buf[0:hindex], f.data[f.head:])
+		copy(buf[hindex:count], f.data[:f.tail])
+	}
+	f.data, f.head, f.tail = buf, 0, count
+}
+
+// countReader implements a proxy reader that counts the number of
+// bytes read from its encapsulated reader.
+type countReader struct {
+	r     io.Reader
+	bytes int64
+}
+
+func newCountReader(r io.Reader) *countReader {
+	return &countReader{r: r}
+}
+
+func (cr *countReader) Read(p []byte) (n int, err error) {
+	b, err := cr.r.Read(p)
+	cr.bytes += int64(b)
+	return b, err
+}
+
+// countWriter implements a proxy writer that counts the number of
+// bytes written by its encapsulated writer.
+type countWriter struct {
+	w     io.Writer
+	bytes int64
+}
+
+func newCountWriter(w io.Writer) *countWriter {
+	return &countWriter{w: w}
+}
+
+func (cw *countWriter) Write(p []byte) (n int, err error) {
+	b, err := cw.w.Write(p)
+	cw.bytes += int64(b)
+	return b, err
+}
+
+// isWhitespace returns true if the byte slice contains only
+// whitespace characters.
+func isWhitespace(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if c := s[i]; c != ' ' && c != '\t' && c != '\n' && c != '\r' {
+			return false
+		}
+	}
+	return true
+}
+
+// spaceMatch returns true if namespace a is the empty string
+// or if namespace a equals namespace b.
+func spaceMatch(a, b string) bool {
+	switch {
+	case a == "":
+		return true
+	default:
+		return a == b
+	}
+}
+
+// spaceDecompose breaks a namespace:tag identifier at the ':'
+// and returns the two parts.
+func spaceDecompose(str string) (space, key string) {
+	colon := strings.IndexByte(str, ':')
+	if colon == -1 {
+		return "", str
+	}
+	return str[:colon], str[colon+1:]
+}
+
+// Strings used by crIndent
+const (
+	crsp  = "\n                                                                "
+	crtab = "\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t"
+)
+
+// crIndent returns a carriage return followed by n copies of the
+// first non-CR character in the source string.
+func crIndent(n int, source string) string {
+	switch {
+	case n < 0:
+		return source[:1]
+	case n < len(source):
+		return source[:n+1]
+	default:
+		return source + strings.Repeat(source[1:2], n-len(source)+1)
+	}
+}
+
+// nextIndex returns the index of the next occurrence of sep in s,
+// starting from offset.  It returns -1 if the sep string is not found.
+func nextIndex(s, sep string, offset int) int {
+	switch i := strings.Index(s[offset:], sep); i {
+	case -1:
+		return -1
+	default:
+		return offset + i
+	}
+}
+
+// isInteger returns true if the string s contains an integer.
+func isInteger(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if (s[i] < '0' || s[i] > '9') && !(i == 0 && s[i] == '-') {
+			return false
+		}
+	}
+	return true
+}
--- a/vendor/github.com/beevik/etree/path.go
+++ b/vendor/github.com/beevik/etree/path.go
@ -0,0 +1,470 @@
+// Copyright 2015 Brett Vickers.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package etree
+
+import (
+	"strconv"
+	"strings"
+)
+
+/*
+A Path is an object that represents an optimized version of an
+XPath-like search string.  Although path strings are XPath-like,
+only the following limited syntax is supported:
+
+    .               Selects the current element
+    ..              Selects the parent of the current element
+    *               Selects all child elements
+    //              Selects all descendants of the current element
+    tag             Selects all child elements with the given tag
+    [#]             Selects the element of the given index (1-based,
+                      negative starts from the end)
+    [@attrib]       Selects all elements with the given attribute
+    [@attrib='val'] Selects all elements with the given attribute set to val
+    [tag]           Selects all elements with a child element named tag
+    [tag='val']     Selects all elements with a child element named tag
+                      and text equal to val
+
+Examples:
+
+Select the title elements of all descendant book elements having a
+'category' attribute of 'WEB':
+    //book[@category='WEB']/title
+
+Select the first book element with a title child containing the text
+'Great Expectations':
+    .//book[title='Great Expectations'][1]
+
+Starting from the current element, select all children of book elements
+with an attribute 'language' set to 'english':
+    ./book/*[@language='english']
+
+Select all descendant book elements whose title element has an attribute
+'language' set to 'french':
+    //book/title[@language='french']/..
+*/
+type Path struct {
+	segments []segment
+}
+
+// ErrPath is returned by path functions when an invalid etree path is provided.
+type ErrPath string
+
+// Error returns the string describing a path error.
+func (err ErrPath) Error() string {
+	return "etree: " + string(err)
+}
+
+// CompilePath creates an optimized version of an XPath-like string that
+// can be used to query elements in an element tree.
+func CompilePath(path string) (Path, error) {
+	var comp compiler
+	segments := comp.parsePath(path)
+	if comp.err != ErrPath("") {
+		return Path{nil}, comp.err
+	}
+	return Path{segments}, nil
+}
+
+// MustCompilePath creates an optimized version of an XPath-like string that
+// can be used to query elements in an element tree.  Panics if an error
+// occurs.  Use this function to create Paths when you know the path is
+// valid (i.e., if it's hard-coded).
+func MustCompilePath(path string) Path {
+	p, err := CompilePath(path)
+	if err != nil {
+		panic(err)
+	}
+	return p
+}
+
+// A segment is a portion of a path between "/" characters.
+// It contains one selector and zero or more [filters].
+type segment struct {
+	sel     selector
+	filters []filter
+}
+
+func (seg *segment) apply(e *Element, p *pather) {
+	seg.sel.apply(e, p)
+	for _, f := range seg.filters {
+		f.apply(p)
+	}
+}
+
+// A selector selects XML elements for consideration by the
+// path traversal.
+type selector interface {
+	apply(e *Element, p *pather)
+}
+
+// A filter pares down a list of candidate XML elements based
+// on a path filter in [brackets].
+type filter interface {
+	apply(p *pather)
+}
+
+// A pather is helper object that traverses an element tree using
+// a Path object.  It collects and deduplicates all elements matching
+// the path query.
+type pather struct {
+	queue      fifo
+	results    []*Element
+	inResults  map[*Element]bool
+	candidates []*Element
+	scratch    []*Element // used by filters
+}
+
+// A node represents an element and the remaining path segments that
+// should be applied against it by the pather.
+type node struct {
+	e        *Element
+	segments []segment
+}
+
+func newPather() *pather {
+	return &pather{
+		results:    make([]*Element, 0),
+		inResults:  make(map[*Element]bool),
+		candidates: make([]*Element, 0),
+		scratch:    make([]*Element, 0),
+	}
+}
+
+// traverse follows the path from the element e, collecting
+// and then returning all elements that match the path's selectors
+// and filters.
+func (p *pather) traverse(e *Element, path Path) []*Element {
+	for p.queue.add(node{e, path.segments}); p.queue.len() > 0; {
+		p.eval(p.queue.remove().(node))
+	}
+	return p.results
+}
+
+// eval evalutes the current path node by applying the remaining
+// path's selector rules against the node's element.
+func (p *pather) eval(n node) {
+	p.candidates = p.candidates[0:0]
+	seg, remain := n.segments[0], n.segments[1:]
+	seg.apply(n.e, p)
+
+	if len(remain) == 0 {
+		for _, c := range p.candidates {
+			if in := p.inResults[c]; !in {
+				p.inResults[c] = true
+				p.results = append(p.results, c)
+			}
+		}
+	} else {
+		for _, c := range p.candidates {
+			p.queue.add(node{c, remain})
+		}
+	}
+}
+
+// A compiler generates a compiled path from a path string.
+type compiler struct {
+	err ErrPath
+}
+
+// parsePath parses an XPath-like string describing a path
+// through an element tree and returns a slice of segment
+// descriptors.
+func (c *compiler) parsePath(path string) []segment {
+	// If path starts or ends with //, fix it
+	if strings.HasPrefix(path, "//") {
+		path = "." + path
+	}
+	if strings.HasSuffix(path, "//") {
+		path = path + "*"
+	}
+
+	// Paths cannot be absolute
+	if strings.HasPrefix(path, "/") {
+		c.err = ErrPath("paths cannot be absolute.")
+		return nil
+	}
+
+	// Split path into segment objects
+	var segments []segment
+	for _, s := range splitPath(path) {
+		segments = append(segments, c.parseSegment(s))
+		if c.err != ErrPath("") {
+			break
+		}
+	}
+	return segments
+}
+
+func splitPath(path string) []string {
+	pieces := make([]string, 0)
+	start := 0
+	inquote := false
+	for i := 0; i+1 <= len(path); i++ {
+		if path[i] == '\'' {
+			inquote = !inquote
+		} else if path[i] == '/' && !inquote {
+			pieces = append(pieces, path[start:i])
+			start = i + 1
+		}
+	}
+	return append(pieces, path[start:])
+}
+
+// parseSegment parses a path segment between / characters.
+func (c *compiler) parseSegment(path string) segment {
+	pieces := strings.Split(path, "[")
+	seg := segment{
+		sel:     c.parseSelector(pieces[0]),
+		filters: make([]filter, 0),
+	}
+	for i := 1; i < len(pieces); i++ {
+		fpath := pieces[i]
+		if fpath[len(fpath)-1] != ']' {
+			c.err = ErrPath("path has invalid filter [brackets].")
+			break
+		}
+		seg.filters = append(seg.filters, c.parseFilter(fpath[:len(fpath)-1]))
+	}
+	return seg
+}
+
+// parseSelector parses a selector at the start of a path segment.
+func (c *compiler) parseSelector(path string) selector {
+	switch path {
+	case ".":
+		return new(selectSelf)
+	case "..":
+		return new(selectParent)
+	case "*":
+		return new(selectChildren)
+	case "":
+		return new(selectDescendants)
+	default:
+		return newSelectChildrenByTag(path)
+	}
+}
+
+// parseFilter parses a path filter contained within [brackets].
+func (c *compiler) parseFilter(path string) filter {
+	if len(path) == 0 {
+		c.err = ErrPath("path contains an empty filter expression.")
+		return nil
+	}
+
+	// Filter contains [@attr='val'] or [tag='val']?
+	eqindex := strings.Index(path, "='")
+	if eqindex >= 0 {
+		rindex := nextIndex(path, "'", eqindex+2)
+		if rindex != len(path)-1 {
+			c.err = ErrPath("path has mismatched filter quotes.")
+			return nil
+		}
+		switch {
+		case path[0] == '@':
+			return newFilterAttrVal(path[1:eqindex], path[eqindex+2:rindex])
+		default:
+			return newFilterChildText(path[:eqindex], path[eqindex+2:rindex])
+		}
+	}
+
+	// Filter contains [@attr], [N] or [tag]
+	switch {
+	case path[0] == '@':
+		return newFilterAttr(path[1:])
+	case isInteger(path):
+		pos, _ := strconv.Atoi(path)
+		switch {
+		case pos > 0:
+			return newFilterPos(pos - 1)
+		default:
+			return newFilterPos(pos)
+		}
+	default:
+		return newFilterChild(path)
+	}
+}
+
+// selectSelf selects the current element into the candidate list.
+type selectSelf struct{}
+
+func (s *selectSelf) apply(e *Element, p *pather) {
+	p.candidates = append(p.candidates, e)
+}
+
+// selectParent selects the element's parent into the candidate list.
+type selectParent struct{}
+
+func (s *selectParent) apply(e *Element, p *pather) {
+	if e.parent != nil {
+		p.candidates = append(p.candidates, e.parent)
+	}
+}
+
+// selectChildren selects the element's child elements into the
+// candidate list.
+type selectChildren struct{}
+
+func (s *selectChildren) apply(e *Element, p *pather) {
+	for _, c := range e.Child {
+		if c, ok := c.(*Element); ok {
+			p.candidates = append(p.candidates, c)
+		}
+	}
+}
+
+// selectDescendants selects all descendant child elements
+// of the element into the candidate list.
+type selectDescendants struct{}
+
+func (s *selectDescendants) apply(e *Element, p *pather) {
+	var queue fifo
+	for queue.add(e); queue.len() > 0; {
+		e := queue.remove().(*Element)
+		p.candidates = append(p.candidates, e)
+		for _, c := range e.Child {
+			if c, ok := c.(*Element); ok {
+				queue.add(c)
+			}
+		}
+	}
+}
+
+// selectChildrenByTag selects into the candidate list all child
+// elements of the element having the specified tag.
+type selectChildrenByTag struct {
+	space, tag string
+}
+
+func newSelectChildrenByTag(path string) *selectChildrenByTag {
+	s, l := spaceDecompose(path)
+	return &selectChildrenByTag{s, l}
+}
+
+func (s *selectChildrenByTag) apply(e *Element, p *pather) {
+	for _, c := range e.Child {
+		if c, ok := c.(*Element); ok && spaceMatch(s.space, c.Space) && s.tag == c.Tag {
+			p.candidates = append(p.candidates, c)
+		}
+	}
+}
+
+// filterPos filters the candidate list, keeping only the
+// candidate at the specified index.
+type filterPos struct {
+	index int
+}
+
+func newFilterPos(pos int) *filterPos {
+	return &filterPos{pos}
+}
+
+func (f *filterPos) apply(p *pather) {
+	if f.index >= 0 {
+		if f.index < len(p.candidates) {
+			p.scratch = append(p.scratch, p.candidates[f.index])
+		}
+	} else {
+		if -f.index <= len(p.candidates) {
+			p.scratch = append(p.scratch, p.candidates[len(p.candidates)+f.index])
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
+// filterAttr filters the candidate list for elements having
+// the specified attribute.
+type filterAttr struct {
+	space, key string
+}
+
+func newFilterAttr(str string) *filterAttr {
+	s, l := spaceDecompose(str)
+	return &filterAttr{s, l}
+}
+
+func (f *filterAttr) apply(p *pather) {
+	for _, c := range p.candidates {
+		for _, a := range c.Attr {
+			if spaceMatch(f.space, a.Space) && f.key == a.Key {
+				p.scratch = append(p.scratch, c)
+				break
+			}
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
+// filterAttrVal filters the candidate list for elements having
+// the specified attribute with the specified value.
+type filterAttrVal struct {
+	space, key, val string
+}
+
+func newFilterAttrVal(str, value string) *filterAttrVal {
+	s, l := spaceDecompose(str)
+	return &filterAttrVal{s, l, value}
+}
+
+func (f *filterAttrVal) apply(p *pather) {
+	for _, c := range p.candidates {
+		for _, a := range c.Attr {
+			if spaceMatch(f.space, a.Space) && f.key == a.Key && f.val == a.Value {
+				p.scratch = append(p.scratch, c)
+				break
+			}
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
+// filterChild filters the candidate list for elements having
+// a child element with the specified tag.
+type filterChild struct {
+	space, tag string
+}
+
+func newFilterChild(str string) *filterChild {
+	s, l := spaceDecompose(str)
+	return &filterChild{s, l}
+}
+
+func (f *filterChild) apply(p *pather) {
+	for _, c := range p.candidates {
+		for _, cc := range c.Child {
+			if cc, ok := cc.(*Element); ok &&
+				spaceMatch(f.space, cc.Space) &&
+				f.tag == cc.Tag {
+				p.scratch = append(p.scratch, c)
+			}
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
+// filterChildText filters the candidate list for elements having
+// a child element with the specified tag and text.
+type filterChildText struct {
+	space, tag, text string
+}
+
+func newFilterChildText(str, text string) *filterChildText {
+	s, l := spaceDecompose(str)
+	return &filterChildText{s, l, text}
+}
+
+func (f *filterChildText) apply(p *pather) {
+	for _, c := range p.candidates {
+		for _, cc := range c.Child {
+			if cc, ok := cc.(*Element); ok &&
+				spaceMatch(f.space, cc.Space) &&
+				f.tag == cc.Tag &&
+				f.text == cc.Text() {
+				p.scratch = append(p.scratch, c)
+			}
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
--- a/vendor/github.com/jonboulle/clockwork/LICENSE
+++ b/vendor/github.com/jonboulle/clockwork/LICENSE
@ -0,0 +1,201 @@
+Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "{}"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright {yyyy} {name of copyright owner}
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
--- a/vendor/github.com/jonboulle/clockwork/clockwork.go
+++ b/vendor/github.com/jonboulle/clockwork/clockwork.go
@ -0,0 +1,179 @@
+package clockwork
+
+import (
+	"sync"
+	"time"
+)
+
+// Clock provides an interface that packages can use instead of directly
+// using the time module, so that chronology-related behavior can be tested
+type Clock interface {
+	After(d time.Duration) <-chan time.Time
+	Sleep(d time.Duration)
+	Now() time.Time
+	Since(t time.Time) time.Duration
+}
+
+// FakeClock provides an interface for a clock which can be
+// manually advanced through time
+type FakeClock interface {
+	Clock
+	// Advance advances the FakeClock to a new point in time, ensuring any existing
+	// sleepers are notified appropriately before returning
+	Advance(d time.Duration)
+	// BlockUntil will block until the FakeClock has the given number of
+	// sleepers (callers of Sleep or After)
+	BlockUntil(n int)
+}
+
+// NewRealClock returns a Clock which simply delegates calls to the actual time
+// package; it should be used by packages in production.
+func NewRealClock() Clock {
+	return &realClock{}
+}
+
+// NewFakeClock returns a FakeClock implementation which can be
+// manually advanced through time for testing. The initial time of the
+// FakeClock will be an arbitrary non-zero time.
+func NewFakeClock() FakeClock {
+	// use a fixture that does not fulfill Time.IsZero()
+	return NewFakeClockAt(time.Date(1984, time.April, 4, 0, 0, 0, 0, time.UTC))
+}
+
+// NewFakeClockAt returns a FakeClock initialised at the given time.Time.
+func NewFakeClockAt(t time.Time) FakeClock {
+	return &fakeClock{
+		time: t,
+	}
+}
+
+type realClock struct{}
+
+func (rc *realClock) After(d time.Duration) <-chan time.Time {
+	return time.After(d)
+}
+
+func (rc *realClock) Sleep(d time.Duration) {
+	time.Sleep(d)
+}
+
+func (rc *realClock) Now() time.Time {
+	return time.Now()
+}
+
+func (rc *realClock) Since(t time.Time) time.Duration {
+	return rc.Now().Sub(t)
+}
+
+type fakeClock struct {
+	sleepers []*sleeper
+	blockers []*blocker
+	time     time.Time
+
+	l sync.RWMutex
+}
+
+// sleeper represents a caller of After or Sleep
+type sleeper struct {
+	until time.Time
+	done  chan time.Time
+}
+
+// blocker represents a caller of BlockUntil
+type blocker struct {
+	count int
+	ch    chan struct{}
+}
+
+// After mimics time.After; it waits for the given duration to elapse on the
+// fakeClock, then sends the current time on the returned channel.
+func (fc *fakeClock) After(d time.Duration) <-chan time.Time {
+	fc.l.Lock()
+	defer fc.l.Unlock()
+	now := fc.time
+	done := make(chan time.Time, 1)
+	if d.Nanoseconds() == 0 {
+		// special case - trigger immediately
+		done <- now
+	} else {
+		// otherwise, add to the set of sleepers
+		s := &sleeper{
+			until: now.Add(d),
+			done:  done,
+		}
+		fc.sleepers = append(fc.sleepers, s)
+		// and notify any blockers
+		fc.blockers = notifyBlockers(fc.blockers, len(fc.sleepers))
+	}
+	return done
+}
+
+// notifyBlockers notifies all the blockers waiting until the
+// given number of sleepers are waiting on the fakeClock. It
+// returns an updated slice of blockers (i.e. those still waiting)
+func notifyBlockers(blockers []*blocker, count int) (newBlockers []*blocker) {
+	for _, b := range blockers {
+		if b.count == count {
+			close(b.ch)
+		} else {
+			newBlockers = append(newBlockers, b)
+		}
+	}
+	return
+}
+
+// Sleep blocks until the given duration has passed on the fakeClock
+func (fc *fakeClock) Sleep(d time.Duration) {
+	<-fc.After(d)
+}
+
+// Time returns the current time of the fakeClock
+func (fc *fakeClock) Now() time.Time {
+	fc.l.RLock()
+	t := fc.time
+	fc.l.RUnlock()
+	return t
+}
+
+// Since returns the duration that has passed since the given time on the fakeClock
+func (fc *fakeClock) Since(t time.Time) time.Duration {
+	return fc.Now().Sub(t)
+}
+
+// Advance advances fakeClock to a new point in time, ensuring channels from any
+// previous invocations of After are notified appropriately before returning
+func (fc *fakeClock) Advance(d time.Duration) {
+	fc.l.Lock()
+	defer fc.l.Unlock()
+	end := fc.time.Add(d)
+	var newSleepers []*sleeper
+	for _, s := range fc.sleepers {
+		if end.Sub(s.until) >= 0 {
+			s.done <- end
+		} else {
+			newSleepers = append(newSleepers, s)
+		}
+	}
+	fc.sleepers = newSleepers
+	fc.blockers = notifyBlockers(fc.blockers, len(fc.sleepers))
+	fc.time = end
+}
+
+// BlockUntil will block until the fakeClock has the given number of sleepers
+// (callers of Sleep or After)
+func (fc *fakeClock) BlockUntil(n int) {
+	fc.l.Lock()
+	// Fast path: current number of sleepers is what we're looking for
+	if len(fc.sleepers) == n {
+		fc.l.Unlock()
+		return
+	}
+	// Otherwise, set up a new blocker
+	b := &blocker{
+		count: n,
+		ch:    make(chan struct{}),
+	}
+	fc.blockers = append(fc.blockers, b)
+	fc.l.Unlock()
+	<-b.ch
+}
--- a/vendor/github.com/russellhaering/goxmldsig/LICENSE
+++ b/vendor/github.com/russellhaering/goxmldsig/LICENSE
@ -0,0 +1,175 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
--- a/vendor/github.com/russellhaering/goxmldsig/canonicalize.go
+++ b/vendor/github.com/russellhaering/goxmldsig/canonicalize.go
@ -0,0 +1,251 @@
+package dsig
+
+import (
+	"sort"
+	"strings"
+
+	"github.com/beevik/etree"
+)
+
+// Canonicalizer is an implementation of a canonicalization algorithm.
+type Canonicalizer interface {
+	Canonicalize(el *etree.Element) ([]byte, error)
+	Algorithm() AlgorithmID
+}
+
+type c14N10ExclusiveCanonicalizer struct {
+	InclusiveNamespaces map[string]struct{}
+}
+
+// MakeC14N10ExclusiveCanonicalizerWithPrefixList constructs an exclusive Canonicalizer
+// from a PrefixList in NMTOKENS format (a white space separated list).
+func MakeC14N10ExclusiveCanonicalizerWithPrefixList(prefixList string) Canonicalizer {
+	prefixes := strings.Fields(prefixList)
+	prefixSet := make(map[string]struct{}, len(prefixes))
+
+	for _, prefix := range prefixes {
+		prefixSet[prefix] = struct{}{}
+	}
+
+	return &c14N10ExclusiveCanonicalizer{
+		InclusiveNamespaces: prefixSet,
+	}
+}
+
+// Canonicalize transforms the input Element into a serialized XML document in canonical form.
+func (c *c14N10ExclusiveCanonicalizer) Canonicalize(el *etree.Element) ([]byte, error) {
+	scope := make(map[string]c14nSpace)
+	return canonicalSerialize(excCanonicalPrep(el, scope, c.InclusiveNamespaces))
+}
+
+func (c *c14N10ExclusiveCanonicalizer) Algorithm() AlgorithmID {
+	return CanonicalXML10ExclusiveAlgorithmId
+}
+
+type c14N11Canonicalizer struct{}
+
+// MakeC14N11Canonicalizer constructs an inclusive canonicalizer.
+func MakeC14N11Canonicalizer() Canonicalizer {
+	return &c14N11Canonicalizer{}
+}
+
+// Canonicalize transforms the input Element into a serialized XML document in canonical form.
+func (c *c14N11Canonicalizer) Canonicalize(el *etree.Element) ([]byte, error) {
+	scope := make(map[string]struct{})
+	return canonicalSerialize(canonicalPrep(el, scope))
+}
+
+func (c *c14N11Canonicalizer) Algorithm() AlgorithmID {
+	return CanonicalXML11AlgorithmId
+}
+
+func composeAttr(space, key string) string {
+	if space != "" {
+		return space + ":" + key
+	}
+
+	return key
+}
+
+type attrsByKey []etree.Attr
+
+func (a attrsByKey) Len() int {
+	return len(a)
+}
+
+func (a attrsByKey) Swap(i, j int) {
+	a[i], a[j] = a[j], a[i]
+}
+
+func (a attrsByKey) Less(i, j int) bool {
+	// As I understand it: any "xmlns" attribute should come first, followed by any
+	// any "xmlns:prefix" attributes, presumably ordered by prefix. Lastly any other
+	// attributes in lexicographical order.
+	if a[i].Space == "" && a[i].Key == "xmlns" {
+		return true
+	}
+
+	if a[i].Space == "xmlns" {
+		if a[j].Space == "xmlns" {
+			return a[i].Key < a[j].Key
+		}
+		return true
+	}
+
+	if a[j].Space == "xmlns" {
+		return false
+	}
+
+	return composeAttr(a[i].Space, a[i].Key) < composeAttr(a[j].Space, a[j].Key)
+}
+
+type c14nSpace struct {
+	a    etree.Attr
+	used bool
+}
+
+const nsSpace = "xmlns"
+
+// excCanonicalPrep accepts an *etree.Element and recursively transforms it into one
+// which is ready for serialization to exclusive canonical form. Specifically this
+// entails:
+//
+// 1. Stripping re-declarations of namespaces
+// 2. Stripping unused namespaces
+// 3. Sorting attributes into canonical order.
+//
+// NOTE(russell_h): Currently this function modifies the passed element.
+func excCanonicalPrep(el *etree.Element, _nsAlreadyDeclared map[string]c14nSpace, inclusiveNamespaces map[string]struct{}) *etree.Element {
+	//Copy alreadyDeclared map (only contains namespaces)
+	nsAlreadyDeclared := make(map[string]c14nSpace, len(_nsAlreadyDeclared))
+	for k := range _nsAlreadyDeclared {
+		nsAlreadyDeclared[k] = _nsAlreadyDeclared[k]
+	}
+
+	//Track the namespaces used on the current element
+	nsUsedHere := make(map[string]struct{})
+
+	//Make sure to track the element namespace for the case:
+	//<foo:bar xmlns:foo="..."/>
+	if el.Space != "" {
+		nsUsedHere[el.Space] = struct{}{}
+	}
+
+	toRemove := make([]string, 0, 0)
+
+	for _, a := range el.Attr {
+		switch a.Space {
+		case nsSpace:
+
+			//For simplicity, remove all xmlns attribues; to be added in one pass
+			//later.  Otherwise, we need another map/set to track xmlns attributes
+			//that we left alone.
+			toRemove = append(toRemove, a.Space+":"+a.Key)
+			if _, ok := nsAlreadyDeclared[a.Key]; !ok {
+				//If we're not tracking ancestor state already for this namespace, add
+				//it to the map
+				nsAlreadyDeclared[a.Key] = c14nSpace{a: a, used: false}
+			}
+
+			// This algorithm accepts a set of namespaces which should be treated
+			// in an inclusive fashion. Specifically that means we should keep the
+			// declaration of that namespace closest to the root of the tree. We can
+			// accomplish that be pretending it was used by this element.
+			_, inclusive := inclusiveNamespaces[a.Key]
+			if inclusive {
+				nsUsedHere[a.Key] = struct{}{}
+			}
+
+		default:
+			//We only track namespaces, so ignore attributes without one.
+			if a.Space != "" {
+				nsUsedHere[a.Space] = struct{}{}
+			}
+		}
+	}
+
+	//Remove all attributes so that we can add them with much-simpler logic
+	for _, attrK := range toRemove {
+		el.RemoveAttr(attrK)
+	}
+
+	//For all namespaces used on the current element, declare them if they were
+	//not declared (and used) in an ancestor.
+	for k := range nsUsedHere {
+		spc := nsAlreadyDeclared[k]
+		//If previously unused, mark as used
+		if !spc.used {
+			el.Attr = append(el.Attr, spc.a)
+			spc.used = true
+
+			//Assignment here is only to update the pre-existing `used` tracking value
+			nsAlreadyDeclared[k] = spc
+		}
+	}
+
+	//Canonicalize all children, passing down the ancestor tracking map
+	for _, child := range el.ChildElements() {
+		excCanonicalPrep(child, nsAlreadyDeclared, inclusiveNamespaces)
+	}
+
+	//Sort attributes lexicographically
+	sort.Sort(attrsByKey(el.Attr))
+
+	return el.Copy()
+}
+
+// canonicalPrep accepts an *etree.Element and transforms it into one which is ready
+// for serialization into inclusive canonical form. Specifically this
+// entails:
+//
+// 1. Stripping re-declarations of namespaces
+// 2. Sorting attributes into canonical order
+//
+// Inclusive canonicalization does not strip unused namespaces.
+//
+// TODO(russell_h): This is very similar to excCanonicalPrep - perhaps they should
+// be unified into one parameterized function?
+func canonicalPrep(el *etree.Element, seenSoFar map[string]struct{}) *etree.Element {
+	_seenSoFar := make(map[string]struct{})
+	for k, v := range seenSoFar {
+		_seenSoFar[k] = v
+	}
+
+	ne := el.Copy()
+	sort.Sort(attrsByKey(ne.Attr))
+	if len(ne.Attr) != 0 {
+		for _, attr := range ne.Attr {
+			if attr.Space != nsSpace {
+				continue
+			}
+			key := attr.Space + ":" + attr.Key
+			if _, seen := _seenSoFar[key]; seen {
+				ne.RemoveAttr(attr.Space + ":" + attr.Key)
+			} else {
+				_seenSoFar[key] = struct{}{}
+			}
+		}
+	}
+
+	for i, token := range ne.Child {
+		childElement, ok := token.(*etree.Element)
+		if ok {
+			ne.Child[i] = canonicalPrep(childElement, _seenSoFar)
+		}
+	}
+
+	return ne
+}
+
+func canonicalSerialize(el *etree.Element) ([]byte, error) {
+	doc := etree.NewDocument()
+	doc.SetRoot(el)
+
+	doc.WriteSettings = etree.WriteSettings{
+		CanonicalAttrVal: true,
+		CanonicalEndTags: true,
+		CanonicalText:    true,
+	}
+
+	return doc.WriteToBytes()
+}
--- a/vendor/github.com/russellhaering/goxmldsig/clock.go
+++ b/vendor/github.com/russellhaering/goxmldsig/clock.go
@ -0,0 +1,55 @@
+package dsig
+
+import (
+	"time"
+
+	"github.com/jonboulle/clockwork"
+)
+
+// Clock wraps a clockwork.Clock (which could be real or fake) in order
+// to default to a real clock when a nil *Clock is used. In other words,
+// if you attempt to use a nil *Clock it will defer to the real system
+// clock. This allows Clock to be easily added to structs with methods
+// that currently reference the time package, without requiring every
+// instantiation of that struct to be updated.
+type Clock struct {
+	wrapped clockwork.Clock
+}
+
+func (c *Clock) getWrapped() clockwork.Clock {
+	if c == nil {
+		return clockwork.NewRealClock()
+	}
+
+	return c.wrapped
+}
+
+func (c *Clock) After(d time.Duration) <-chan time.Time {
+	return c.getWrapped().After(d)
+}
+
+func (c *Clock) Sleep(d time.Duration) {
+	c.getWrapped().Sleep(d)
+}
+
+func (c *Clock) Now() time.Time {
+	return c.getWrapped().Now()
+}
+
+func NewRealClock() *Clock {
+	return &Clock{
+		wrapped: clockwork.NewRealClock(),
+	}
+}
+
+func NewFakeClock(wrapped clockwork.Clock) *Clock {
+	return &Clock{
+		wrapped: wrapped,
+	}
+}
+
+func NewFakeClockAt(t time.Time) *Clock {
+	return &Clock{
+		wrapped: clockwork.NewFakeClockAt(t),
+	}
+}
--- a/vendor/github.com/russellhaering/goxmldsig/keystore.go
+++ b/vendor/github.com/russellhaering/goxmldsig/keystore.go
@ -0,0 +1,63 @@
+package dsig
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"math/big"
+	"time"
+)
+
+type X509KeyStore interface {
+	GetKeyPair() (privateKey *rsa.PrivateKey, cert []byte, err error)
+}
+
+type X509CertificateStore interface {
+	Certificates() (roots []*x509.Certificate, err error)
+}
+
+type MemoryX509CertificateStore struct {
+	Roots []*x509.Certificate
+}
+
+func (mX509cs *MemoryX509CertificateStore) Certificates() ([]*x509.Certificate, error) {
+	return mX509cs.Roots, nil
+}
+
+type MemoryX509KeyStore struct {
+	privateKey *rsa.PrivateKey
+	cert       []byte
+}
+
+func (ks *MemoryX509KeyStore) GetKeyPair() (*rsa.PrivateKey, []byte, error) {
+	return ks.privateKey, ks.cert, nil
+}
+
+func RandomKeyStoreForTest() X509KeyStore {
+	key, err := rsa.GenerateKey(rand.Reader, 1024)
+	if err != nil {
+		panic(err)
+	}
+
+	now := time.Now()
+
+	template := &x509.Certificate{
+		SerialNumber: big.NewInt(0),
+		NotBefore:    now.Add(-5 * time.Minute),
+		NotAfter:     now.Add(365 * 24 * time.Hour),
+
+		KeyUsage:              x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{},
+		BasicConstraintsValid: true,
+	}
+
+	cert, err := x509.CreateCertificate(rand.Reader, template, template, &key.PublicKey, key)
+	if err != nil {
+		panic(err)
+	}
+
+	return &MemoryX509KeyStore{
+		privateKey: key,
+		cert:       cert,
+	}
+}
--- a/vendor/github.com/russellhaering/goxmldsig/sign.go
+++ b/vendor/github.com/russellhaering/goxmldsig/sign.go
@ -0,0 +1,186 @@
+package dsig
+
+import (
+	"crypto"
+	"crypto/rand"
+	"crypto/rsa"
+	_ "crypto/sha1"
+	_ "crypto/sha256"
+	"encoding/base64"
+	"errors"
+	"fmt"
+
+	"github.com/beevik/etree"
+)
+
+type SigningContext struct {
+	Hash          crypto.Hash
+	KeyStore      X509KeyStore
+	IdAttribute   string
+	Prefix        string
+	Canonicalizer Canonicalizer
+}
+
+func NewDefaultSigningContext(ks X509KeyStore) *SigningContext {
+	return &SigningContext{
+		Hash:          crypto.SHA256,
+		KeyStore:      ks,
+		IdAttribute:   DefaultIdAttr,
+		Prefix:        DefaultPrefix,
+		Canonicalizer: MakeC14N11Canonicalizer(),
+	}
+}
+
+func (ctx *SigningContext) SetSignatureMethod(algorithmID string) error {
+	hash, ok := signatureMethodsByIdentifier[algorithmID]
+	if !ok {
+		return fmt.Errorf("Unknown SignatureMethod: %s", algorithmID)
+	}
+
+	ctx.Hash = hash
+
+	return nil
+}
+
+func (ctx *SigningContext) digest(el *etree.Element) ([]byte, error) {
+	canonical, err := ctx.Canonicalizer.Canonicalize(el)
+	if err != nil {
+		return nil, err
+	}
+
+	hash := ctx.Hash.New()
+	_, err = hash.Write(canonical)
+	if err != nil {
+		return nil, err
+	}
+
+	return hash.Sum(nil), nil
+}
+
+func (ctx *SigningContext) constructSignedInfo(el *etree.Element, enveloped bool) (*etree.Element, error) {
+	digestAlgorithmIdentifier, ok := digestAlgorithmIdentifiers[ctx.Hash]
+	if !ok {
+		return nil, errors.New("unsupported hash mechanism")
+	}
+
+	signatureMethodIdentifier, ok := signatureMethodIdentifiers[ctx.Hash]
+	if !ok {
+		return nil, errors.New("unsupported signature method")
+	}
+
+	digest, err := ctx.digest(el)
+	if err != nil {
+		return nil, err
+	}
+
+	signedInfo := &etree.Element{
+		Tag:   SignedInfoTag,
+		Space: ctx.Prefix,
+	}
+
+	// /SignedInfo/CanonicalizationMethod
+	canonicalizationMethod := ctx.createNamespacedElement(signedInfo, CanonicalizationMethodTag)
+	canonicalizationMethod.CreateAttr(AlgorithmAttr, string(ctx.Canonicalizer.Algorithm()))
+
+	// /SignedInfo/SignatureMethod
+	signatureMethod := ctx.createNamespacedElement(signedInfo, SignatureMethodTag)
+	signatureMethod.CreateAttr(AlgorithmAttr, signatureMethodIdentifier)
+
+	// /SignedInfo/Reference
+	reference := ctx.createNamespacedElement(signedInfo, ReferenceTag)
+
+	dataId := el.SelectAttrValue(DefaultIdAttr, "")
+	if dataId == "" {
+		return nil, errors.New("Missing data ID")
+	}
+
+	reference.CreateAttr(URIAttr, "#"+dataId)
+
+	// /SignedInfo/Reference/Transforms
+	transforms := ctx.createNamespacedElement(reference, TransformsTag)
+	if enveloped {
+		envelopedTransform := ctx.createNamespacedElement(transforms, TransformTag)
+		envelopedTransform.CreateAttr(AlgorithmAttr, EnvelopedSignatureAltorithmId.String())
+	}
+	canonicalizationAlgorithm := ctx.createNamespacedElement(transforms, TransformTag)
+	canonicalizationAlgorithm.CreateAttr(AlgorithmAttr, string(ctx.Canonicalizer.Algorithm()))
+
+	// /SignedInfo/Reference/DigestMethod
+	digestMethod := ctx.createNamespacedElement(reference, DigestMethodTag)
+	digestMethod.CreateAttr(AlgorithmAttr, digestAlgorithmIdentifier)
+
+	// /SignedInfo/Reference/DigestValue
+	digestValue := ctx.createNamespacedElement(reference, DigestValueTag)
+	digestValue.SetText(base64.StdEncoding.EncodeToString(digest))
+
+	return signedInfo, nil
+}
+
+func (ctx *SigningContext) constructSignature(el *etree.Element, enveloped bool) (*etree.Element, error) {
+	signedInfo, err := ctx.constructSignedInfo(el, enveloped)
+	if err != nil {
+		return nil, err
+	}
+
+	sig := &etree.Element{
+		Tag:   SignatureTag,
+		Space: ctx.Prefix,
+	}
+
+	xmlns := "xmlns"
+	if ctx.Prefix != "" {
+		xmlns += ":" + ctx.Prefix
+	}
+
+	sig.CreateAttr(xmlns, Namespace)
+
+	sig.Child = append(sig.Child, signedInfo)
+
+	// Must propagate down the attributes to the 'SignedInfo' before digesting
+	for _, attr := range sig.Attr {
+		signedInfo.CreateAttr(attr.Space+":"+attr.Key, attr.Value)
+	}
+
+	digest, err := ctx.digest(signedInfo)
+	if err != nil {
+		return nil, err
+	}
+
+	key, cert, err := ctx.KeyStore.GetKeyPair()
+	if err != nil {
+		return nil, err
+	}
+
+	rawSignature, err := rsa.SignPKCS1v15(rand.Reader, key, ctx.Hash, digest)
+	if err != nil {
+		return nil, err
+	}
+
+	signatureValue := ctx.createNamespacedElement(sig, SignatureValueTag)
+	signatureValue.SetText(base64.StdEncoding.EncodeToString(rawSignature))
+
+	keyInfo := ctx.createNamespacedElement(sig, KeyInfoTag)
+	x509Data := ctx.createNamespacedElement(keyInfo, X509DataTag)
+	x509Certificate := ctx.createNamespacedElement(x509Data, X509CertificateTag)
+	x509Certificate.SetText(base64.StdEncoding.EncodeToString(cert))
+
+	return sig, nil
+}
+
+func (ctx *SigningContext) createNamespacedElement(el *etree.Element, tag string) *etree.Element {
+	child := el.CreateElement(tag)
+	child.Space = ctx.Prefix
+	return child
+}
+
+func (ctx *SigningContext) SignEnveloped(el *etree.Element) (*etree.Element, error) {
+	sig, err := ctx.constructSignature(el, true)
+	if err != nil {
+		return nil, err
+	}
+
+	ret := el.Copy()
+	ret.Child = append(ret.Child, sig)
+
+	return ret, nil
+}
--- a/vendor/github.com/russellhaering/goxmldsig/tls_keystore.go
+++ b/vendor/github.com/russellhaering/goxmldsig/tls_keystore.go
@ -0,0 +1,34 @@
+package dsig
+
+import (
+	"crypto/rsa"
+	"crypto/tls"
+	"fmt"
+)
+
+//Well-known errors
+var (
+	ErrNonRSAKey           = fmt.Errorf("Private key was not RSA")
+	ErrMissingCertificates = fmt.Errorf("No public certificates provided")
+)
+
+//TLSCertKeyStore wraps the stdlib tls.Certificate to return its contained key
+//and certs.
+type TLSCertKeyStore tls.Certificate
+
+//GetKeyPair implements X509KeyStore using the underlying tls.Certificate
+func (d TLSCertKeyStore) GetKeyPair() (*rsa.PrivateKey, []byte, error) {
+	pk, ok := d.PrivateKey.(*rsa.PrivateKey)
+
+	if !ok {
+		return nil, nil, ErrNonRSAKey
+	}
+
+	if len(d.Certificate) < 1 {
+		return nil, nil, ErrMissingCertificates
+	}
+
+	crt := d.Certificate[0]
+
+	return pk, crt, nil
+}
--- a/vendor/github.com/russellhaering/goxmldsig/validate.go
+++ b/vendor/github.com/russellhaering/goxmldsig/validate.go
@ -0,0 +1,397 @@
+package dsig
+
+import (
+	"bytes"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"regexp"
+
+	"github.com/beevik/etree"
+)
+
+var uriRegexp = regexp.MustCompile("^#[a-zA-Z_][\\w.-]*$")
+
+type ValidationContext struct {
+	CertificateStore X509CertificateStore
+	IdAttribute      string
+	Clock            *Clock
+}
+
+func NewDefaultValidationContext(certificateStore X509CertificateStore) *ValidationContext {
+	return &ValidationContext{
+		CertificateStore: certificateStore,
+		IdAttribute:      DefaultIdAttr,
+	}
+}
+
+// TODO(russell_h): More flexible namespace support. This might barely work.
+func inNamespace(el *etree.Element, ns string) bool {
+	for _, attr := range el.Attr {
+		if attr.Value == ns {
+			if attr.Space == "" && attr.Key == "xmlns" {
+				return el.Space == ""
+			} else if attr.Space == "xmlns" {
+				return el.Space == attr.Key
+			}
+		}
+	}
+
+	return false
+}
+
+func childPath(space, tag string) string {
+	if space == "" {
+		return "./" + tag
+	} else {
+		return "./" + space + ":" + tag
+	}
+}
+
+// The RemoveElement method on etree.Element isn't recursive...
+func recursivelyRemoveElement(tree, el *etree.Element) bool {
+	if tree.RemoveChild(el) != nil {
+		return true
+	}
+
+	for _, child := range tree.Child {
+		if childElement, ok := child.(*etree.Element); ok {
+			if recursivelyRemoveElement(childElement, el) {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+// transform applies the passed set of transforms to the specified root element.
+//
+// The functionality of transform is currently very limited and purpose-specific.
+//
+// NOTE(russell_h): Ideally this wouldn't mutate the root passed to it, and would
+// instead return a copy. Unfortunately copying the tree makes it difficult to
+// correctly locate the signature. I'm opting, for now, to simply mutate the root
+// parameter.
+func (ctx *ValidationContext) transform(root, sig *etree.Element, transforms []*etree.Element) (*etree.Element, Canonicalizer, error) {
+	if len(transforms) != 2 {
+		return nil, nil, errors.New("Expected Enveloped and C14N transforms")
+	}
+
+	var canonicalizer Canonicalizer
+
+	for _, transform := range transforms {
+		algo := transform.SelectAttr(AlgorithmAttr)
+		if algo == nil {
+			return nil, nil, errors.New("Missing Algorithm attribute")
+		}
+
+		switch AlgorithmID(algo.Value) {
+		case EnvelopedSignatureAltorithmId:
+			if !recursivelyRemoveElement(root, sig) {
+				return nil, nil, errors.New("Error applying canonicalization transform: Signature not found")
+			}
+
+		case CanonicalXML10ExclusiveAlgorithmId:
+			var prefixList string
+			ins := transform.FindElement(childPath("", InclusiveNamespacesTag))
+			if ins != nil {
+				prefixListEl := ins.SelectAttr(PrefixListAttr)
+				if prefixListEl != nil {
+					prefixList = prefixListEl.Value
+				}
+			}
+
+			canonicalizer = MakeC14N10ExclusiveCanonicalizerWithPrefixList(prefixList)
+
+		case CanonicalXML11AlgorithmId:
+			canonicalizer = MakeC14N11Canonicalizer()
+
+		default:
+			return nil, nil, errors.New("Unknown Transform Algorithm: " + algo.Value)
+		}
+	}
+
+	if canonicalizer == nil {
+		return nil, nil, errors.New("Expected canonicalization transform")
+	}
+
+	return root, canonicalizer, nil
+}
+
+func (ctx *ValidationContext) digest(el *etree.Element, digestAlgorithmId string, canonicalizer Canonicalizer) ([]byte, error) {
+	data, err := canonicalizer.Canonicalize(el)
+	if err != nil {
+		return nil, err
+	}
+
+	digestAlgorithm, ok := digestAlgorithmsByIdentifier[digestAlgorithmId]
+	if !ok {
+		return nil, errors.New("Unknown digest algorithm: " + digestAlgorithmId)
+	}
+
+	hash := digestAlgorithm.New()
+	_, err = hash.Write(data)
+	if err != nil {
+		return nil, err
+	}
+
+	return hash.Sum(nil), nil
+}
+
+func (ctx *ValidationContext) verifySignedInfo(signatureElement *etree.Element, canonicalizer Canonicalizer, signatureMethodId string, cert *x509.Certificate, sig []byte) error {
+	signedInfo := signatureElement.FindElement(childPath(signatureElement.Space, SignedInfoTag))
+	if signedInfo == nil {
+		return errors.New("Missing SignedInfo")
+	}
+
+	// Any attributes from the 'Signature' element must be pushed down into the 'SignedInfo' element before it is canonicalized
+	for _, attr := range signatureElement.Attr {
+		signedInfo.CreateAttr(attr.Space+":"+attr.Key, attr.Value)
+	}
+
+	// Canonicalize the xml
+	canonical, err := canonicalizer.Canonicalize(signedInfo)
+	if err != nil {
+		return err
+	}
+
+	signatureAlgorithm, ok := signatureMethodsByIdentifier[signatureMethodId]
+	if !ok {
+		return errors.New("Unknown signature method: " + signatureMethodId)
+	}
+
+	hash := signatureAlgorithm.New()
+	_, err = hash.Write(canonical)
+	if err != nil {
+		return err
+	}
+
+	hashed := hash.Sum(nil)
+
+	pubKey, ok := cert.PublicKey.(*rsa.PublicKey)
+	if !ok {
+		return errors.New("Invalid public key")
+	}
+
+	// Verify that the private key matching the public key from the cert was what was used to sign the 'SignedInfo' and produce the 'SignatureValue'
+	err = rsa.VerifyPKCS1v15(pubKey, signatureAlgorithm, hashed[:], sig)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (ctx *ValidationContext) validateSignature(el *etree.Element, cert *x509.Certificate) (*etree.Element, error) {
+	el = el.Copy()
+
+	// Verify the document minus the signedInfo against the 'DigestValue'
+	// Find the 'Signature' element
+	sig := el.FindElement(SignatureTag)
+
+	if sig == nil {
+		return nil, errors.New("Missing Signature")
+	}
+
+	if !inNamespace(sig, Namespace) {
+		return nil, errors.New("Signature element is in the wrong namespace")
+	}
+
+	// Get the 'SignedInfo' element
+	signedInfo := sig.FindElement(childPath(sig.Space, SignedInfoTag))
+	if signedInfo == nil {
+		return nil, errors.New("Missing SignedInfo")
+	}
+
+	reference := signedInfo.FindElement(childPath(sig.Space, ReferenceTag))
+	if reference == nil {
+		return nil, errors.New("Missing Reference")
+	}
+
+	transforms := reference.FindElement(childPath(sig.Space, TransformsTag))
+	if transforms == nil {
+		return nil, errors.New("Missing Transforms")
+	}
+
+	uri := reference.SelectAttr("URI")
+	if uri == nil {
+		// TODO(russell_h): It is permissible to leave this out. We should be
+		// able to fall back to finding the referenced element some other way.
+		return nil, errors.New("Reference is missing URI attribute")
+	}
+
+	if !uriRegexp.MatchString(uri.Value) {
+		return nil, errors.New("Invalid URI: " + uri.Value)
+	}
+
+	// Get the element referenced in the 'SignedInfo'
+	referencedElement := el.FindElement(fmt.Sprintf("//[@%s='%s']", ctx.IdAttribute, uri.Value[1:]))
+	if referencedElement == nil {
+		return nil, errors.New("Unable to find referenced element: " + uri.Value)
+	}
+
+	// Perform all transformations listed in the 'SignedInfo'
+	// Basically, this means removing the 'SignedInfo'
+	transformed, canonicalizer, err := ctx.transform(referencedElement, sig, transforms.ChildElements())
+	if err != nil {
+		return nil, err
+	}
+
+	digestMethod := reference.FindElement(childPath(sig.Space, DigestMethodTag))
+	if digestMethod == nil {
+		return nil, errors.New("Missing DigestMethod")
+	}
+
+	digestValue := reference.FindElement(childPath(sig.Space, DigestValueTag))
+	if digestValue == nil {
+		return nil, errors.New("Missing DigestValue")
+	}
+
+	digestAlgorithmAttr := digestMethod.SelectAttr(AlgorithmAttr)
+	if digestAlgorithmAttr == nil {
+		return nil, errors.New("Missing DigestMethod Algorithm attribute")
+	}
+
+	// Digest the transformed XML and compare it to the 'DigestValue' from the 'SignedInfo'
+	digest, err := ctx.digest(transformed, digestAlgorithmAttr.Value, canonicalizer)
+	if err != nil {
+		return nil, err
+	}
+
+	decodedDigestValue, err := base64.StdEncoding.DecodeString(digestValue.Text())
+	if err != nil {
+		return nil, err
+	}
+
+	if !bytes.Equal(digest, decodedDigestValue) {
+		return nil, errors.New("Signature could not be verified")
+	}
+
+	//Verify the signed info
+	signatureMethod := signedInfo.FindElement(childPath(sig.Space, SignatureMethodTag))
+	if signatureMethod == nil {
+		return nil, errors.New("Missing SignatureMethod")
+	}
+
+	signatureMethodAlgorithmAttr := signatureMethod.SelectAttr(AlgorithmAttr)
+	if digestAlgorithmAttr == nil {
+		return nil, errors.New("Missing SignatureMethod Algorithm attribute")
+	}
+
+	// Decode the 'SignatureValue' so we can compare against it
+	signatureValue := sig.FindElement(childPath(sig.Space, SignatureValueTag))
+	if signatureValue == nil {
+		return nil, errors.New("Missing SignatureValue")
+	}
+
+	decodedSignature, err := base64.StdEncoding.DecodeString(signatureValue.Text())
+
+	if err != nil {
+		return nil, errors.New("Could not decode signature")
+	}
+	// Actually verify the 'SignedInfo' was signed by a trusted source
+	err = ctx.verifySignedInfo(sig, canonicalizer, signatureMethodAlgorithmAttr.Value, cert, decodedSignature)
+	if err != nil {
+		return nil, err
+	}
+
+	return transformed, nil
+}
+
+func contains(roots []*x509.Certificate, cert *x509.Certificate) bool {
+	for _, root := range roots {
+		if root.Equal(cert) {
+			return true
+		}
+	}
+	return false
+}
+
+func (ctx *ValidationContext) verifyCertificate(el *etree.Element) (*x509.Certificate, error) {
+	now := ctx.Clock.Now()
+	el = el.Copy()
+
+	idAttr := el.SelectAttr(DefaultIdAttr)
+	if idAttr == nil || idAttr.Value == "" {
+		return nil, errors.New("Missing ID attribute")
+	}
+
+	signatureElements := el.FindElements("//" + SignatureTag)
+	var signatureElement *etree.Element
+
+	// Find the Signature element that references the whole Response element
+	for _, e := range signatureElements {
+		e2 := e.Copy()
+
+		signedInfo := e2.FindElement(childPath(e2.Space, SignedInfoTag))
+		if signedInfo == nil {
+			return nil, errors.New("Missing SignedInfo")
+		}
+
+		referenceElement := signedInfo.FindElement(childPath(e2.Space, ReferenceTag))
+		if referenceElement == nil {
+			return nil, errors.New("Missing Reference Element")
+		}
+
+		uriAttr := referenceElement.SelectAttr(URIAttr)
+		if uriAttr == nil || uriAttr.Value == "" {
+			return nil, errors.New("Missing URI attribute")
+		}
+
+		if uriAttr.Value[1:] == idAttr.Value {
+			signatureElement = e
+			break
+		}
+	}
+
+	if signatureElement == nil {
+		return nil, errors.New("Missing signature referencing the top-level element")
+	}
+
+	// Get the x509 element from the signature
+	x509Element := signatureElement.FindElement("//" + childPath(signatureElement.Space, X509CertificateTag))
+	if x509Element == nil {
+		return nil, errors.New("Missing x509 Element")
+	}
+
+	x509Text := "-----BEGIN CERTIFICATE-----\n" + x509Element.Text() + "\n-----END CERTIFICATE-----"
+	block, _ := pem.Decode([]byte(x509Text))
+	if block == nil {
+		return nil, errors.New("Failed to parse certificate PEM")
+	}
+
+	cert, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		return nil, err
+	}
+
+	roots, err := ctx.CertificateStore.Certificates()
+	if err != nil {
+		return nil, err
+	}
+
+	// Verify that the certificate is one we trust
+	if !contains(roots, cert) {
+		return nil, errors.New("Could not verify certificate against trusted certs")
+	}
+
+	if now.Before(cert.NotBefore) || now.After(cert.NotAfter) {
+		return nil, errors.New("Cert is not valid at this time")
+	}
+
+	return cert, nil
+}
+
+func (ctx *ValidationContext) Validate(el *etree.Element) (*etree.Element, error) {
+	cert, err := ctx.verifyCertificate(el)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return ctx.validateSignature(el, cert)
+}
--- a/vendor/github.com/russellhaering/goxmldsig/xml_constants.go
+++ b/vendor/github.com/russellhaering/goxmldsig/xml_constants.go
@ -0,0 +1,78 @@
+package dsig
+
+import "crypto"
+
+const (
+	DefaultPrefix = "ds"
+	Namespace     = "http://www.w3.org/2000/09/xmldsig#"
+)
+
+// Tags
+const (
+	SignatureTag              = "Signature"
+	SignedInfoTag             = "SignedInfo"
+	CanonicalizationMethodTag = "CanonicalizationMethod"
+	SignatureMethodTag        = "SignatureMethod"
+	ReferenceTag              = "Reference"
+	TransformsTag             = "Transforms"
+	TransformTag              = "Transform"
+	DigestMethodTag           = "DigestMethod"
+	DigestValueTag            = "DigestValue"
+	SignatureValueTag         = "SignatureValue"
+	KeyInfoTag                = "KeyInfo"
+	X509DataTag               = "X509Data"
+	X509CertificateTag        = "X509Certificate"
+	InclusiveNamespacesTag    = "InclusiveNamespaces"
+)
+
+const (
+	AlgorithmAttr  = "Algorithm"
+	URIAttr        = "URI"
+	DefaultIdAttr  = "ID"
+	PrefixListAttr = "PrefixList"
+)
+
+type AlgorithmID string
+
+func (id AlgorithmID) String() string {
+	return string(id)
+}
+
+const (
+	RSASHA1SignatureMethod   = "http://www.w3.org/2000/09/xmldsig#rsa-sha1"
+	RSASHA256SignatureMethod = "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"
+	RSASHA512SignatureMethod = "http://www.w3.org/2001/04/xmldsig-more#rsa-sha512"
+)
+
+//Well-known signature algorithms
+const (
+	// Supported canonicalization algorithms
+	CanonicalXML10ExclusiveAlgorithmId AlgorithmID = "http://www.w3.org/2001/10/xml-exc-c14n#"
+	CanonicalXML11AlgorithmId          AlgorithmID = "http://www.w3.org/2006/12/xml-c14n11"
+
+	EnvelopedSignatureAltorithmId AlgorithmID = "http://www.w3.org/2000/09/xmldsig#enveloped-signature"
+)
+
+var digestAlgorithmIdentifiers = map[crypto.Hash]string{
+	crypto.SHA1:   "http://www.w3.org/2000/09/xmldsig#sha1",
+	crypto.SHA256: "http://www.w3.org/2001/04/xmlenc#sha256",
+	crypto.SHA512: "http://www.w3.org/2001/04/xmlenc#sha512",
+}
+
+var digestAlgorithmsByIdentifier = map[string]crypto.Hash{}
+var signatureMethodsByIdentifier = map[string]crypto.Hash{}
+
+func init() {
+	for hash, id := range digestAlgorithmIdentifiers {
+		digestAlgorithmsByIdentifier[id] = hash
+	}
+	for hash, id := range signatureMethodIdentifiers {
+		signatureMethodsByIdentifier[id] = hash
+	}
+}
+
+var signatureMethodIdentifiers = map[crypto.Hash]string{
+	crypto.SHA1:   RSASHA1SignatureMethod,
+	crypto.SHA256: RSASHA256SignatureMethod,
+	crypto.SHA512: RSASHA512SignatureMethod,
+}