vendor: revendor

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
+
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+
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+      and distribution as defined by Sections 1 through 9 of this document.
+
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+      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.
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+      including but not limited to software source code, documentation
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+
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+      form, that is based on (or derived from) the Work and for which the
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+      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
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+
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+      whether in tort (including negligence), contract, or otherwise,
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+      negligent acts) or agreed to in writing, shall any Contributor be
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+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.

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()
+}

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),
+	}
+}

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,
+	}
+}

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
+}

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
+}

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)
+}

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,
+}