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dex/vendor/github.com/coreos/go-oidc/verify.go
2017-01-06 15:39:36 -08:00

270 lines
7.8 KiB
Go

package oidc
import (
"bytes"
"encoding/base64"
"encoding/json"
"errors"
"fmt"
"strings"
"time"
"golang.org/x/net/context"
"golang.org/x/oauth2"
jose "gopkg.in/square/go-jose.v2"
)
// IDTokenVerifier provides verification for ID Tokens.
type IDTokenVerifier struct {
keySet *remoteKeySet
config *verificationConfig
}
// verificationConfig is the unexported configuration for an IDTokenVerifier.
//
// Users interact with this struct using a VerificationOption.
type verificationConfig struct {
issuer string
// If provided, this value must be in the ID Token audiences.
audience string
// If not nil, check the expiry of the id token.
checkExpiry func() time.Time
// If specified, only these sets of algorithms may be used to sign the JWT.
requiredAlgs []string
// If not nil, don't verify nonce.
nonceSource NonceSource
}
// VerificationOption provides additional checks on ID Tokens.
type VerificationOption interface {
// Unexport this method so other packages can't implement this interface.
updateConfig(c *verificationConfig)
}
// Verifier returns an IDTokenVerifier that uses the provider's key set to verify JWTs.
//
// The returned IDTokenVerifier is tied to the Provider's context and its behavior is
// undefined once the Provider's context is canceled.
func (p *Provider) Verifier(options ...VerificationOption) *IDTokenVerifier {
config := &verificationConfig{issuer: p.issuer}
for _, option := range options {
option.updateConfig(config)
}
return newVerifier(p.remoteKeySet, config)
}
func newVerifier(keySet *remoteKeySet, config *verificationConfig) *IDTokenVerifier {
// As discussed in the godocs for VerifrySigningAlg, because almost all providers
// only support RS256, default to only allowing it.
if len(config.requiredAlgs) == 0 {
config.requiredAlgs = []string{RS256}
}
return &IDTokenVerifier{
keySet: keySet,
config: config,
}
}
func parseJWT(p string) ([]byte, error) {
parts := strings.Split(p, ".")
if len(parts) < 2 {
return nil, fmt.Errorf("oidc: malformed jwt, expected 3 parts got %d", len(parts))
}
payload, err := base64.RawURLEncoding.DecodeString(parts[1])
if err != nil {
return nil, fmt.Errorf("oidc: malformed jwt payload: %v", err)
}
return payload, nil
}
func contains(sli []string, ele string) bool {
for _, s := range sli {
if s == ele {
return true
}
}
return false
}
// Verify parses a raw ID Token, verifies it's been signed by the provider, preforms
// any additional checks passed as VerifictionOptions, and returns the payload.
//
// See: https://openid.net/specs/openid-connect-core-1_0.html#IDTokenValidation
//
// oauth2Token, err := oauth2Config.Exchange(ctx, r.URL.Query().Get("code"))
// if err != nil {
// // handle error
// }
//
// // Extract the ID Token from oauth2 token.
// rawIDToken, ok := oauth2Token.Extra("id_token").(string)
// if !ok {
// // handle error
// }
//
// token, err := verifier.Verify(ctx, rawIDToken)
//
func (v *IDTokenVerifier) Verify(ctx context.Context, rawIDToken string) (*IDToken, error) {
jws, err := jose.ParseSigned(rawIDToken)
if err != nil {
return nil, fmt.Errorf("oidc: mallformed jwt: %v", err)
}
// Throw out tokens with invalid claims before trying to verify the token. This lets
// us do cheap checks before possibly re-syncing keys.
payload, err := parseJWT(rawIDToken)
if err != nil {
return nil, fmt.Errorf("oidc: malformed jwt: %v", err)
}
var token idToken
if err := json.Unmarshal(payload, &token); err != nil {
return nil, fmt.Errorf("oidc: failed to unmarshal claims: %v", err)
}
t := &IDToken{
Issuer: token.Issuer,
Subject: token.Subject,
Audience: []string(token.Audience),
Expiry: time.Time(token.Expiry),
IssuedAt: time.Time(token.IssuedAt),
Nonce: token.Nonce,
claims: payload,
}
// Check issuer.
if t.Issuer != v.config.issuer {
return nil, fmt.Errorf("oidc: id token issued by a different provider, expected %q got %q", v.config.issuer, t.Issuer)
}
// If a client ID has been provided, make sure it's part of the audience.
if v.config.audience != "" {
if !contains(t.Audience, v.config.audience) {
return nil, fmt.Errorf("oidc: expected audience %q got %q", v.config.audience, t.Audience)
}
}
// If a checkExpiry is specified, make sure token is not expired.
if v.config.checkExpiry != nil {
if t.Expiry.Before(v.config.checkExpiry()) {
return nil, fmt.Errorf("oidc: token is expired (Token Expiry: %v)", t.Expiry)
}
}
// If a set of required algorithms has been provided, ensure that the signatures use those.
var keyIDs, gotAlgs []string
for _, sig := range jws.Signatures {
if len(v.config.requiredAlgs) == 0 || contains(v.config.requiredAlgs, sig.Header.Algorithm) {
keyIDs = append(keyIDs, sig.Header.KeyID)
} else {
gotAlgs = append(gotAlgs, sig.Header.Algorithm)
}
}
if len(keyIDs) == 0 {
return nil, fmt.Errorf("oidc: no signatures use a require algorithm, expected %q got %q", v.config.requiredAlgs, gotAlgs)
}
// Get keys from the remote key set. This may trigger a re-sync.
keys, err := v.keySet.keysWithID(ctx, keyIDs)
if err != nil {
return nil, fmt.Errorf("oidc: get keys for id token: %v", err)
}
if len(keys) == 0 {
return nil, fmt.Errorf("oidc: no keys match signature ID(s) %q", keyIDs)
}
// Try to use a key to validate the signature.
var gotPayload []byte
for _, key := range keys {
if p, err := jws.Verify(&key); err == nil {
gotPayload = p
}
}
if len(gotPayload) == 0 {
return nil, fmt.Errorf("oidc: failed to verify id token")
}
// Ensure that the payload returned by the square actually matches the payload parsed earlier.
if !bytes.Equal(gotPayload, payload) {
return nil, errors.New("oidc: internal error, payload parsed did not match previous payload")
}
// Check the nonce after we've verified the token. We don't want to allow unverified
// payloads to trigger a nonce lookup.
if v.config.nonceSource != nil {
if err := v.config.nonceSource.ClaimNonce(t.Nonce); err != nil {
return nil, err
}
}
return t, nil
}
// VerifyAudience ensures that an ID Token was issued for the specific client.
//
// Note that a verified token may be valid for other clients, as OpenID Connect allows a token to have
// multiple audiences.
func VerifyAudience(clientID string) VerificationOption {
return clientVerifier{clientID}
}
type clientVerifier struct {
clientID string
}
func (v clientVerifier) updateConfig(c *verificationConfig) {
c.audience = v.clientID
}
// VerifyExpiry ensures that an ID Token has not expired.
func VerifyExpiry() VerificationOption {
return expiryVerifier{}
}
type expiryVerifier struct{}
func (v expiryVerifier) updateConfig(c *verificationConfig) {
c.checkExpiry = time.Now
}
// VerifySigningAlg enforces that an ID Token is signed by a specific signing algorithm.
//
// Because so many providers only support RS256, if this verifiction option isn't used,
// the IDTokenVerifier defaults to only allowing RS256.
func VerifySigningAlg(allowedAlgs ...string) VerificationOption {
return algVerifier{allowedAlgs}
}
type algVerifier struct {
algs []string
}
func (v algVerifier) updateConfig(c *verificationConfig) {
c.requiredAlgs = v.algs
}
// Nonce returns an auth code option which requires the ID Token created by the
// OpenID Connect provider to contain the specified nonce.
func Nonce(nonce string) oauth2.AuthCodeOption {
return oauth2.SetAuthURLParam("nonce", nonce)
}
// NonceSource represents a source which can verify a nonce is valid and has not
// been claimed before.
type NonceSource interface {
ClaimNonce(nonce string) error
}
// VerifyNonce ensures that the ID Token contains a nonce which can be claimed by the nonce source.
func VerifyNonce(source NonceSource) VerificationOption {
return nonceVerifier{source}
}
type nonceVerifier struct {
nonceSource NonceSource
}
func (n nonceVerifier) updateConfig(c *verificationConfig) {
c.nonceSource = n.nonceSource
}