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server: set sane bcrypt cost upper bound

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This commit is contained in:
Eric Stroczynski
2017-08-17 14:46:07 -07:00
parent 20fd3163d9
commit 2b354c8fdb
4 changed files with 38 additions and 161 deletions
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38
server/api.go
View File

@@ -21,8 +21,16 @@ import (
// to determine if the server supports specific features.
const apiVersion = 2
// recCost is the recommended bcrypt cost, which balances hash strength and time
const recCost = 12
const (
// recCost is the recommended bcrypt cost, which balances hash strength and
// efficiency.
recCost = 12
// upBoundCost is a sane upper bound on bcrypt cost determined by benchmarking:
// high enough to ensure secure encryption, low enough to not put unnecessary
// load on a dex server.
upBoundCost = 16
)
// NewAPI returns a server which implements the gRPC API interface.
func NewAPI(s storage.Storage, logger logrus.FieldLogger) api.DexServer {
@@ -83,16 +91,20 @@ func (d dexAPI) DeleteClient(ctx context.Context, req *api.DeleteClientReq) (*ap
return &api.DeleteClientResp{}, nil
}
// checkCost returns an error if the hash provided does not meet minimum cost requirement, and the actual bcrypt cost
func checkCost(hash []byte) (int, error) {
// checkCost returns an error if the hash provided does not meet lower or upper
// bound cost requirements.
func checkCost(hash []byte) error {
actual, err := bcrypt.Cost(hash)
if err != nil {
return 0, fmt.Errorf("parsing bcrypt hash: %v", err)
return fmt.Errorf("parsing bcrypt hash: %v", err)
}
if actual < bcrypt.DefaultCost {
return actual, fmt.Errorf("given hash cost = %d, does not meet minimum cost requirement = %d", actual, bcrypt.DefaultCost)
return fmt.Errorf("given hash cost = %d does not meet minimum cost requirement = %d", actual, bcrypt.DefaultCost)
}
return actual, nil
if actual > upBoundCost {
return fmt.Errorf("given hash cost = %d is above upper bound cost = %d, recommended cost = %d", actual, upBoundCost, recCost)
}
return nil
}
func (d dexAPI) CreatePassword(ctx context.Context, req *api.CreatePasswordReq) (*api.CreatePasswordResp, error) {
@@ -103,13 +115,9 @@ func (d dexAPI) CreatePassword(ctx context.Context, req *api.CreatePasswordReq)
return nil, errors.New("no user ID supplied")
}
if req.Password.Hash != nil {
cost, err := checkCost(req.Password.Hash)
if err != nil {
if err := checkCost(req.Password.Hash); err != nil {
return nil, err
}
if cost > recCost {
d.logger.Warnln("bcrypt cost = %d, password encryption might timeout. Recommended bcrypt cost is 12", cost)
}
} else {
return nil, errors.New("no hash of password supplied")
}
@@ -140,13 +148,9 @@ func (d dexAPI) UpdatePassword(ctx context.Context, req *api.UpdatePasswordReq)
}
if req.NewHash != nil {
cost, err := checkCost(req.NewHash)
if err != nil {
if err := checkCost(req.NewHash); err != nil {
return nil, err
}
if cost > recCost {
d.logger.Warnln("bcrypt cost = %d, password encryption might timeout. Recommended bcrypt cost is 12", cost)
}
}
updater := func(old storage.Password) (storage.Password, error) {

18
server/api_test.go
View File

@@ -134,14 +134,13 @@ func TestCheckCost(t *testing.T) {
tests := []struct {
name string
inputHash []byte
expectedCost int
wantErr bool
}{
{
name: "valid cost",
// bcrypt hash of the value "test1" with cost 12
// bcrypt hash of the value "test1" with cost 12 (default)
inputHash: []byte("$2a$12$M2Ot95Qty1MuQdubh1acWOiYadJDzeVg3ve4n5b.dgcgPdjCseKx2"),
expectedCost: recCost,
},
{
name: "invalid hash",
@@ -156,15 +155,14 @@ func TestCheckCost(t *testing.T) {
},
{
name: "cost above recommendation",
// bcrypt hash of the value "test1" with cost 20
inputHash: []byte("$2a$20$yODn5quqK9MZdePqYLs6Y.Jr4cOO1P0aXsKz0eTa2rxOmu8e7ETpi"),
expectedCost: 20,
// bcrypt hash of the value "test1" with cost 17
inputHash: []byte("$2a$17$tWuZkTxtSmRyWZAGWVHQE.7npdl.TgP8adjzLJD.SyjpFznKBftPe"),
wantErr: true,
},
}
for _, tc := range tests {
cost, err := checkCost(tc.inputHash)
if err != nil {
if err := checkCost(tc.inputHash); err != nil {
if !tc.wantErr {
t.Errorf("%s: %s", tc.name, err)
}
@@ -175,10 +173,6 @@ func TestCheckCost(t *testing.T) {
t.Errorf("%s: expected err", tc.name)
continue
}
if cost != tc.expectedCost {
t.Errorf("%s: exepcted cost = %d but got cost = %d", tc.name, tc.expectedCost, cost)
}
}
}

23
server/server.go
View File

@@ -288,25 +288,14 @@ func (db passwordDB) Login(ctx context.Context, s connector.Scopes, email, passw
}
return connector.Identity{}, false, nil
}
// Return an error if password-hash comparison takes longer than 10 seconds
errCh := make(chan error, 1)
go func() {
errCh <- bcrypt.CompareHashAndPassword(p.Hash, []byte(password))
}()
select {
case err = <-errCh:
if err != nil {
return connector.Identity{}, false, nil
}
case <-time.After(time.Second * 10):
var cost int
if cost, err = bcrypt.Cost(p.Hash); err == nil {
err = fmt.Errorf("password-hash comparison timeout: your bcrypt cost = %d, recommended cost = %d", cost, recCost)
}
// This check prevents dex users from logging in using static passwords
// configured with hash costs that are too high or low.
if err := checkCost(p.Hash); err != nil {
return connector.Identity{}, false, err
}
if err := bcrypt.CompareHashAndPassword(p.Hash, []byte(password)); err != nil {
return connector.Identity{}, false, nil
}
return connector.Identity{
UserID: p.UserID,
Username: p.Username,

112
server/server_test.go
View File

@@ -818,7 +818,7 @@ func TestPasswordDB(t *testing.T) {
pw := "hi"
h, err := bcrypt.GenerateFromPassword([]byte(pw), bcrypt.MinCost)
h, err := bcrypt.GenerateFromPassword([]byte(pw), bcrypt.DefaultCost)
if err != nil {
t.Fatal(err)
}
@@ -896,116 +896,6 @@ func TestPasswordDB(t *testing.T) {
}
// A warning message should be logged if password-hash comparison takes longer than 10s
func TestLoginTimeout(t *testing.T) {
s := memory.New(logger)
conn := newPasswordDB(s)
pw := "test1"
tests := []struct {
name, email, password string
pwHash []byte
wantIdentity connector.Identity
wantInvalid bool
wantedErr string
}{
{
name: "valid password min cost",
email: "jane@example.com",
password: pw,
// bcrypt hash of the value "test1" with cost 4
pwHash: []byte("$2a$04$lGqOe5gnlpsfreQ1OJHxGOO7f5FyyESyICkswSFATM1cnBVgCyyuG"),
wantIdentity: connector.Identity{
Email: "jane@example.com",
Username: "jane",
UserID: "foobar",
EmailVerified: true,
},
},
{
name: "valid password reccomended cost",
email: "jane@example.com",
password: pw,
// bcrypt hash of the value "test1" with cost 12
pwHash: []byte("$2a$12$VZNNjuCUGX2NG5S1ci.3Ku9mI9DmA9XeXyrr7YzJuyTxuVBGdRAbm"),
wantIdentity: connector.Identity{
Email: "jane@example.com",
Username: "jane",
UserID: "foobar",
EmailVerified: true,
},
},
{
name: "valid password timeout cost",
email: "jane@example.com",
password: pw,
// bcrypt hash of the value "test1" with cost 20
pwHash: []byte("$2a$20$yODn5quqK9MZdePqYLs6Y.Jr4cOO1P0aXsKz0eTa2rxOmu8e7ETpi"),
wantedErr: fmt.Sprintf("password-hash comparison timeout: your bcrypt cost = 20, recommended cost = %d", recCost),
},
{
name: "invalid password min cost",
email: "jane@example.com",
password: pw,
// bcrypt hash of the value "test2" with cost 4
pwHash: []byte("$2a$04$pX8wwwpxw8xlXrToYaEgZemK0JIibMZYXPsgau7aPDoGyHPF73br."),
wantInvalid: true,
},
{
name: "invalid password timeout cost",
email: "jane@example.com",
password: pw,
// bcrypt hash of the value "test2" with cost 20
pwHash: []byte("$2a$20$WBD9cs63Zf0zqS99yyrQhODoDXphWw8MlYqVYRiftJH.lRJ1stnAa"),
wantedErr: fmt.Sprintf("password-hash comparison timeout: your bcrypt cost = 20, recommended cost = %d", recCost),
},
}
sEmail, sUsername, sUserID := "jane@example.com", "jane", "foobar"
for _, tc := range tests {
// Clean up before new test case
s.DeletePassword(sEmail)
s.CreatePassword(storage.Password{
Email: sEmail,
Username: sUsername,
UserID: sUserID,
Hash: tc.pwHash,
})
ident, valid, err := conn.Login(context.Background(), connector.Scopes{}, tc.email, tc.password)
if err != nil {
if err.Error() != tc.wantedErr {
t.Errorf("%s: error was incorrect:\n%v", tc.name, err)
}
continue
}
if tc.wantedErr != "" {
t.Errorf("%s: expected error", tc.name)
continue
}
if !valid {
if !tc.wantInvalid {
t.Errorf("%s: expected valid response", tc.name)
}
continue
}
if tc.wantInvalid {
t.Errorf("%s: expected invalid response", tc.name)
continue
}
if diff := pretty.Compare(tc.wantIdentity, ident); diff != "" {
t.Errorf("%s: %s", tc.email, diff)
}
}
}
type storageWithKeysTrigger struct {
storage.Storage
f func()