forked from coreos/go-oidc
/
jwks.go
257 lines (222 loc) · 7.22 KB
/
jwks.go
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package oidc
import (
"context"
"crypto"
"crypto/ecdsa"
"crypto/ed25519"
"crypto/rsa"
"errors"
"fmt"
"io"
"net/http"
"sync"
"time"
jose "github.com/go-jose/go-jose/v4"
)
// StaticKeySet is a verifier that validates JWT against a static set of public keys.
type StaticKeySet struct {
// PublicKeys used to verify the JWT. Supported types are *rsa.PublicKey and
// *ecdsa.PublicKey.
PublicKeys []crypto.PublicKey
}
// VerifySignature compares the signature against a static set of public keys.
func (s *StaticKeySet) VerifySignature(ctx context.Context, jwt string) ([]byte, error) {
// Algorithms are already checked by Verifier, so this parse method accepts
// any algorithm.
jws, err := jose.ParseSigned(jwt, allAlgs)
if err != nil {
return nil, fmt.Errorf("parsing jwt: %v", err)
}
for _, pub := range s.PublicKeys {
switch pub.(type) {
case *rsa.PublicKey:
case *ecdsa.PublicKey:
case ed25519.PublicKey:
default:
return nil, fmt.Errorf("invalid public key type provided: %T", pub)
}
payload, err := jws.Verify(pub)
if err != nil {
continue
}
return payload, nil
}
return nil, fmt.Errorf("no public keys able to verify jwt")
}
// 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 any
// keys change. Reuse a common remote key set instead of creating new ones as needed.
func NewRemoteKeySet(ctx context.Context, jwksURL string) *RemoteKeySet {
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}
}
// RemoteKeySet is a KeySet implementation that validates JSON web tokens against
// a jwks_uri endpoint.
type RemoteKeySet struct {
jwksURL string
ctx context.Context
now func() time.Time
// guard all other fields
mu sync.RWMutex
// inflight suppresses parallel execution of updateKeys and allows
// multiple goroutines to wait for its result.
inflight *inflight
// A set of cached keys.
cachedKeys []jose.JSONWebKey
}
// 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
}
// paresdJWTKey is a context key that allows common setups to avoid parsing the
// JWT twice. It holds a *jose.JSONWebSignature value.
var parsedJWTKey contextKey
// VerifySignature validates a payload against a signature from the jwks_uri.
//
// Users MUST NOT call this method directly and should use an IDTokenVerifier
// instead. This method skips critical validations such as 'alg' values and is
// only exported to implement the KeySet interface.
func (r *RemoteKeySet) VerifySignature(ctx context.Context, jwt string) ([]byte, error) {
jws, ok := ctx.Value(parsedJWTKey).(*jose.JSONWebSignature)
if !ok {
// The algorithm values are already enforced by the Validator, which also sets
// the context value above to pre-parsed signature.
//
// Practically, this codepath isn't called in normal use of this package, but
// if it is, the algorithms have already been checked.
var err error
jws, err = jose.ParseSigned(jwt, allAlgs)
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 := r.keysFromCache()
for _, key := range keys {
if keyID == "" || key.KeyID == keyID {
if payload, err := jws.Verify(&key); err == nil {
return payload, nil
}
}
}
// If the kid doesn't match, check for new keys from the remote. This is the
// strategy recommended by the spec.
//
// https://openid.net/specs/openid-connect-core-1_0.html#RotateSigKeys
keys, err := r.keysFromRemote(ctx)
if err != nil {
return nil, fmt.Errorf("fetching keys %w", 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) {
r.mu.RLock()
defer r.mu.RUnlock()
return r.cachedKeys
}
// 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, 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
}
// 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, error) {
req, err := http.NewRequest("GET", r.jwksURL, nil)
if err != nil {
return nil, fmt.Errorf("oidc: can't create request: %v", err)
}
resp, err := doRequest(r.ctx, req)
if err != nil {
return nil, fmt.Errorf("oidc: get keys failed %w", err)
}
defer resp.Body.Close()
body, err := io.ReadAll(resp.Body)
if err != nil {
return nil, fmt.Errorf("unable to read response body: %v", err)
}
if resp.StatusCode != http.StatusOK {
return nil, 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, fmt.Errorf("oidc: failed to decode keys: %v %s", err, body)
}
return keySet.Keys, nil
}