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Refactor token verification to support x5c header

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Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)
This commit is contained in:
Josh Hawn 2014-12-17 16:10:07 -08:00
parent b54bf450dc
commit 2e3af8efcf
1 changed files with 110 additions and 98 deletions
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198
auth/token/token.go
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@ -56,22 +56,8 @@ type Header struct {
Type string `json:"typ"`
SigningAlg string `json:"alg"`
KeyID string `json:"kid,omitempty"`
RawJWK json.RawMessage `json:"jwk"`
SigningKey libtrust.PublicKey `json:"-"`
}
// CheckSigningKey parses the `jwk` field of a JOSE header and sets the
// SigningKey field if it is valid.
func (h *Header) CheckSigningKey() (err error) {
if len(h.RawJWK) == 0 {
// No signing key was specified.
return
}
h.SigningKey, err = libtrust.UnmarshalPublicKeyJWK([]byte(h.RawJWK))
h.RawJWK = nil // Don't need this anymore!
return
X5c []string `json:"x5c,omitempty"`
RawJWK json.RawMessage `json:"jwk,omitempty"`
}
// Token describes a JSON Web Token.
@ -135,10 +121,6 @@ func NewToken(rawToken string) (*Token, error) {
return nil, ErrMalformedToken
}
if err = token.Header.CheckSigningKey(); err != nil {
return nil, ErrMalformedToken
}
if err = json.Unmarshal(claimsJSON, token.Claims); err != nil {
return nil, ErrMalformedToken
}
@ -174,108 +156,86 @@ func (t *Token) Verify(verifyOpts VerifyOptions) error {
return ErrInvalidToken
}
// If the token header has a SigningKey field, verify the signature
// using that key and its included x509 certificate chain if necessary.
// If the Header's SigningKey field is nil, try using the KeyID field.
signingKey := t.Header.SigningKey
if signingKey == nil {
// Find the key in the given collection of trusted keys.
trustedKey, ok := verifyOpts.TrustedKeys[t.Header.KeyID]
if !ok {
log.Errorf("token signed by untrusted key with ID: %q", t.Header.KeyID)
// Verify that the signing key is trusted.
signingKey, err := t.VerifySigningKey(verifyOpts)
if err != nil {
log.Error(err)
return ErrInvalidToken
}
signingKey = trustedKey
}
// First verify the signature of the token using the key which signed it.
// Finally, verify the signature of the token using the key which signed it.
if err := signingKey.Verify(strings.NewReader(t.Raw), t.Header.SigningAlg, t.Signature); err != nil {
log.Errorf("unable to verify token signature: %s", err)
return ErrInvalidToken
}
// Next, check if the signing key is one of the trusted keys.
if _, isTrustedKey := verifyOpts.TrustedKeys[signingKey.KeyID()]; isTrustedKey {
// We're done! The token was signed by
// a trusted key and has been verified!
return nil
}
// Otherwise, we need to check the sigining keys included certificate chain.
return t.verifyCertificateChain(signingKey, verifyOpts.Roots)
}
// verifyCertificateChain attempts to verify the token using the "x5c" field
// of the given leafKey which was used to sign it. Returns a nil error if
// the key's certificate chain is valid and rooted an one of the given roots.
func (t *Token) verifyCertificateChain(leafKey libtrust.PublicKey, roots *x509.CertPool) error {
// In this case, the token signature is valid, but the key that signed it
// is not in our set of trusted keys. So, we'll need to check if the
// token's signing key included an x509 certificate chain that can be
// verified up to one of our trusted roots.
x5cVal, ok := leafKey.GetExtendedField("x5c").([]interface{})
if !ok || x5cVal == nil {
log.Error("unable to verify token signature: signed by untrusted key with no valid certificate chain")
return ErrInvalidToken
// VerifySigningKey attempts to get the key which was used to sign this token.
// The token header should contain either of these 3 fields:
// `x5c` - The x509 certificate chain for the signing key. Needs to be
// verified.
// `jwk` - The JSON Web Key representation of the signing key.
// May contain its own `x5c` field which needs to be verified.
// `kid` - The unique identifier for the key. This library interprets it
// as a libtrust fingerprint. The key itself can be looked up in
// the trustedKeys field of the given verify options.
// Each of these methods are tried in that order of preference until the
// signing key is found or an error is returned.
func (t *Token) VerifySigningKey(verifyOpts VerifyOptions) (signingKey libtrust.PublicKey, err error) {
// First attempt to get an x509 certificate chain from the header.
var (
x5c = t.Header.X5c
rawJWK = t.Header.RawJWK
keyID = t.Header.KeyID
)
switch {
case len(x5c) > 0:
signingKey, err = parseAndVerifyCertChain(x5c, verifyOpts.Roots)
case len(rawJWK) > 0:
signingKey, err = parseAndVerifyRawJWK(rawJWK, verifyOpts)
case len(keyID) > 0:
signingKey = verifyOpts.TrustedKeys[keyID]
if signingKey == nil {
err = fmt.Errorf("token signed by untrusted key with ID: %q", keyID)
}
default:
err = errors.New("unable to get token signing key")
}
// Ensure each item is of the correct type.
x5c := make([]string, len(x5cVal))
for i, val := range x5cVal {
certString, ok := val.(string)
if !ok || len(certString) == 0 {
log.Error("unable to verify token signature: signed by untrusted key with malformed certificate chain")
return ErrInvalidToken
}
x5c[i] = certString
return
}
func parseAndVerifyCertChain(x5c []string, roots *x509.CertPool) (leafKey libtrust.PublicKey, err error) {
if len(x5c) == 0 {
return nil, errors.New("empty x509 certificate chain")
}
// Ensure the first element is encoded correctly.
leafCertDer, err := base64.StdEncoding.DecodeString(x5c[0])
if err != nil {
log.Errorf("unable to decode signing key leaf cert: %s", err)
return ErrInvalidToken
return nil, fmt.Errorf("unable to decode leaf certificate: %s", err)
}
// And that it is a valid x509 certificate.
leafCert, err := x509.ParseCertificate(leafCertDer)
if err != nil {
log.Errorf("unable to parse signing key leaf cert: %s", err)
return ErrInvalidToken
return nil, fmt.Errorf("unable to parse leaf certificate: %s", err)
}
// Verify that the public key in the leaf cert *is* the signing key.
leafCryptoKey, ok := leafCert.PublicKey.(crypto.PublicKey)
if !ok {
log.Error("unable to get signing key leaf cert public key value")
return ErrInvalidToken
}
leafPubKey, err := libtrust.FromCryptoPublicKey(leafCryptoKey)
if err != nil {
log.Errorf("unable to make libtrust public key from signing key leaf cert: %s", err)
return ErrInvalidToken
}
if leafPubKey.KeyID() != leafKey.KeyID() {
log.Error("token signing key ID and leaf certificate public key ID do not match")
return ErrInvalidToken
}
// The rest of the x5c array are intermediate certificates.
// The rest of the certificate chain are intermediate certificates.
intermediates := x509.NewCertPool()
for i := 1; i < len(x5c); i++ {
intermediateCertDer, err := base64.StdEncoding.DecodeString(x5c[i])
if err != nil {
log.Errorf("unable to decode signing key intermediate cert: %s", err)
return ErrInvalidToken
return nil, fmt.Errorf("unable to decode intermediate certificate: %s", err)
}
intermediateCert, err := x509.ParseCertificate(intermediateCertDer)
if err != nil {
log.Errorf("unable to parse signing key intermediate cert: %s", err)
return ErrInvalidToken
return nil, fmt.Errorf("unable to parse intermediate certificate: %s", err)
}
intermediates.AddCert(intermediateCert)
@ -290,12 +250,64 @@ func (t *Token) verifyCertificateChain(leafKey libtrust.PublicKey, roots *x509.C
// TODO: this call returns certificate chains which we ignore for now, but
// we should check them for revocations if we have the ability later.
if _, err = leafCert.Verify(verifyOpts); err != nil {
log.Errorf("unable to verify signing key certificate: %s", err)
return ErrInvalidToken
return nil, fmt.Errorf("unable to verify certificate chain: %s", err)
}
// The signing key's x509 chain is valid!
return nil
// Get the public key from the leaf certificate.
leafCryptoKey, ok := leafCert.PublicKey.(crypto.PublicKey)
if !ok {
return nil, errors.New("unable to get leaf cert public key value")
}
leafKey, err = libtrust.FromCryptoPublicKey(leafCryptoKey)
if err != nil {
return nil, fmt.Errorf("unable to make libtrust public key from leaf certificate: %s", err)
}
return
}
func parseAndVerifyRawJWK(rawJWK json.RawMessage, verifyOpts VerifyOptions) (pubKey libtrust.PublicKey, err error) {
pubKey, err = libtrust.UnmarshalPublicKeyJWK([]byte(rawJWK))
if err != nil {
return nil, fmt.Errorf("unable to decode raw JWK value: %s", err)
}
// Check to see if the key includes a certificate chain.
x5cVal, ok := pubKey.GetExtendedField("x5c").([]interface{})
if !ok {
// The JWK should be one of the trusted root keys.
if _, trusted := verifyOpts.TrustedKeys[pubKey.KeyID()]; !trusted {
return nil, errors.New("untrusted JWK with no certificate chain")
}
// The JWK is one of the trusted keys.
return
}
// Ensure each item in the chain is of the correct type.
x5c := make([]string, len(x5cVal))
for i, val := range x5cVal {
certString, ok := val.(string)
if !ok || len(certString) == 0 {
return nil, errors.New("malformed certificate chain")
}
x5c[i] = certString
}
// Ensure that the x509 certificate chain can
// be verified up to one of our trusted roots.
leafKey, err := parseAndVerifyCertChain(x5c, verifyOpts.Roots)
if err != nil {
return nil, fmt.Errorf("could not verify JWK certificate chain: %s", err)
}
// Verify that the public key in the leaf cert *is* the signing key.
if pubKey.KeyID() != leafKey.KeyID() {
return nil, errors.New("leaf certificate public key ID does not match JWK key ID")
}
return
}
// accessSet returns a set of actions available for the resource