blob: e6a82c842956b9009ed42b23c1cd5f45e460599e [file] [log] [blame]
package oidc
import (
"context"
"errors"
"fmt"
"io/ioutil"
"net/http"
"sync"
"time"
"github.com/pquerna/cachecontrol"
jose "gopkg.in/square/go-jose.v2"
)
// keysExpiryDelta is the allowed clock skew between a client and the OpenID Connect
// server.
//
// When keys expire, they are valid for this amount of time after.
//
// If the keys have not expired, and an ID Token claims it was signed by a key not in
// the cache, if and only if the keys expire in this amount of time, the keys will be
// updated.
const keysExpiryDelta = 30 * time.Second
// NewRemoteKeySet returns a KeySet that can validate JSON web tokens by using HTTP
// GETs to fetch JSON web token sets hosted at a remote URL. This is automatically
// used by NewProvider using the URLs returned by OpenID Connect discovery, but is
// exposed for providers that don't support discovery or to prevent round trips to the
// discovery URL.
//
// The returned KeySet is a long lived verifier that caches keys based on cache-control
// headers. Reuse a common remote key set instead of creating new ones as needed.
//
// The behavior of the returned KeySet is undefined once the context is canceled.
func NewRemoteKeySet(ctx context.Context, jwksURL string) KeySet {
return newRemoteKeySet(ctx, jwksURL, time.Now)
}
func newRemoteKeySet(ctx context.Context, jwksURL string, now func() time.Time) *remoteKeySet {
if now == nil {
now = time.Now
}
return &remoteKeySet{jwksURL: jwksURL, ctx: ctx, now: now}
}
type remoteKeySet struct {
jwksURL string
ctx context.Context
now func() time.Time
// guard all other fields
mu sync.Mutex
// inflight suppresses parallel execution of updateKeys and allows
// multiple goroutines to wait for its result.
inflight *inflight
// A set of cached keys and their expiry.
cachedKeys []jose.JSONWebKey
expiry time.Time
}
// inflight is used to wait on some in-flight request from multiple goroutines.
type inflight struct {
doneCh chan struct{}
keys []jose.JSONWebKey
err error
}
func newInflight() *inflight {
return &inflight{doneCh: make(chan struct{})}
}
// wait returns a channel that multiple goroutines can receive on. Once it returns
// a value, the inflight request is done and result() can be inspected.
func (i *inflight) wait() <-chan struct{} {
return i.doneCh
}
// done can only be called by a single goroutine. It records the result of the
// inflight request and signals other goroutines that the result is safe to
// inspect.
func (i *inflight) done(keys []jose.JSONWebKey, err error) {
i.keys = keys
i.err = err
close(i.doneCh)
}
// result cannot be called until the wait() channel has returned a value.
func (i *inflight) result() ([]jose.JSONWebKey, error) {
return i.keys, i.err
}
func (r *remoteKeySet) VerifySignature(ctx context.Context, jwt string) ([]byte, error) {
jws, err := jose.ParseSigned(jwt)
if err != nil {
return nil, fmt.Errorf("oidc: malformed jwt: %v", err)
}
return r.verify(ctx, jws)
}
func (r *remoteKeySet) verify(ctx context.Context, jws *jose.JSONWebSignature) ([]byte, error) {
// We don't support JWTs signed with multiple signatures.
keyID := ""
for _, sig := range jws.Signatures {
keyID = sig.Header.KeyID
break
}
keys, expiry := r.keysFromCache()
// Don't check expiry yet. This optimizes for when the provider is unavailable.
for _, key := range keys {
if keyID == "" || key.KeyID == keyID {
if payload, err := jws.Verify(&key); err == nil {
return payload, nil
}
}
}
if !r.now().Add(keysExpiryDelta).After(expiry) {
// Keys haven't expired, don't refresh.
return nil, errors.New("failed to verify id token signature")
}
keys, err := r.keysFromRemote(ctx)
if err != nil {
return nil, fmt.Errorf("fetching keys %v", err)
}
for _, key := range keys {
if keyID == "" || key.KeyID == keyID {
if payload, err := jws.Verify(&key); err == nil {
return payload, nil
}
}
}
return nil, errors.New("failed to verify id token signature")
}
func (r *remoteKeySet) keysFromCache() (keys []jose.JSONWebKey, expiry time.Time) {
r.mu.Lock()
defer r.mu.Unlock()
return r.cachedKeys, r.expiry
}
// keysFromRemote syncs the key set from the remote set, records the values in the
// cache, and returns the key set.
func (r *remoteKeySet) keysFromRemote(ctx context.Context) ([]jose.JSONWebKey, error) {
// Need to lock to inspect the inflight request field.
r.mu.Lock()
// If there's not a current inflight request, create one.
if r.inflight == nil {
r.inflight = newInflight()
// This goroutine has exclusive ownership over the current inflight
// request. It releases the resource by nil'ing the inflight field
// once the goroutine is done.
go func() {
// Sync keys and finish inflight when that's done.
keys, expiry, err := r.updateKeys()
r.inflight.done(keys, err)
// Lock to update the keys and indicate that there is no longer an
// inflight request.
r.mu.Lock()
defer r.mu.Unlock()
if err == nil {
r.cachedKeys = keys
r.expiry = expiry
}
// Free inflight so a different request can run.
r.inflight = nil
}()
}
inflight := r.inflight
r.mu.Unlock()
select {
case <-ctx.Done():
return nil, ctx.Err()
case <-inflight.wait():
return inflight.result()
}
}
func (r *remoteKeySet) updateKeys() ([]jose.JSONWebKey, time.Time, error) {
req, err := http.NewRequest("GET", r.jwksURL, nil)
if err != nil {
return nil, time.Time{}, fmt.Errorf("oidc: can't create request: %v", err)
}
resp, err := doRequest(r.ctx, req)
if err != nil {
return nil, time.Time{}, fmt.Errorf("oidc: get keys failed %v", err)
}
defer resp.Body.Close()
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, time.Time{}, fmt.Errorf("unable to read response body: %v", err)
}
if resp.StatusCode != http.StatusOK {
return nil, time.Time{}, fmt.Errorf("oidc: get keys failed: %s %s", resp.Status, body)
}
var keySet jose.JSONWebKeySet
err = unmarshalResp(resp, body, &keySet)
if err != nil {
return nil, time.Time{}, fmt.Errorf("oidc: failed to decode keys: %v %s", err, body)
}
// If the server doesn't provide cache control headers, assume the
// keys expire immediately.
expiry := r.now()
_, e, err := cachecontrol.CachableResponse(req, resp, cachecontrol.Options{})
if err == nil && e.After(expiry) {
expiry = e
}
return keySet.Keys, expiry, nil
}