oidc: ignore cancellation of remote key set context

This has largely caused confusion. Detach the context from its parent
and just use as a bag-of-values for configuration.

oidc/jwks.go

@@ -64,16 +64,28 @@ func newRemoteKeySet(ctx context.Context, jwksURL string, now func() time.Time)
 	if now == nil {
 		now = time.Now
 	}
-	return &RemoteKeySet{jwksURL: jwksURL, ctx: ctx, now: now}
+	return &RemoteKeySet{
+		jwksURL: jwksURL,
+		now:     now,
+		// For historical reasons, this package uses contexts for configuration, not just
+		// cancellation. In hindsight, this was a bad idea.
+		//
+		// Attemps to reason about how cancels should work with background requests have
+		// largely lead to confusion. Use the context here as a config bag-of-values and
+		// ignore the cancel function.
+		ctx: context.WithoutCancel(ctx),
+	}
 }
 
 // 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
 
+	// Used for configuration. Cancelation is ignored.
+	ctx context.Context
+
 	// guard all other fields
 	mu sync.RWMutex
 

oidc/oidc_test.go

@@ -675,3 +675,84 @@ func TestVerifierAlg(t *testing.T) {
 	}
 
 }
+
+func TestCanceledContext(t *testing.T) {
+	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatalf("generating random key: %v", err)
+	}
+	pub := priv.Public()
+	pubKey := jose.JSONWebKey{
+		Algorithm: "ES256",
+		Key:       pub,
+		Use:       "sign",
+	}
+
+	signingKey := jose.SigningKey{
+		Algorithm: jose.ES256,
+		Key:       priv,
+	}
+
+	ts := &testIssuer{
+		algs: []string{"ES256"},
+		jwks: &jose.JSONWebKeySet{
+			Keys: []jose.JSONWebKey{
+				pubKey,
+			},
+		},
+	}
+	srv := httptest.NewServer(ts)
+	ts.baseURL = srv.URL
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	provider, err := NewProvider(ctx, srv.URL)
+	if err != nil {
+		t.Fatalf("creating provider: %v", err)
+	}
+
+	// Explicitly cancel the context.
+	cancel()
+
+	now := time.Now()
+
+	claims := struct {
+		Iss string `json:"iss"`
+		Sub string `json:"sub"`
+		Aud string `json:"aud"`
+		Exp int64  `json:"exp"`
+		Iat int64  `json:"iat"`
+	}{
+		Iss: srv.URL,
+		Sub: "test-user",
+		Aud: "test-client",
+		Exp: now.Add(time.Hour).Unix(),
+		Iat: now.Add(-time.Hour).Unix(),
+	}
+	payload, err := json.Marshal(claims)
+	if err != nil {
+		t.Fatalf("marshaling claims: %v", err)
+	}
+	signer, err := jose.NewSigner(signingKey, nil)
+	if err != nil {
+		t.Fatalf("creating signing key: %v", err)
+	}
+	jws, err := signer.Sign(payload)
+	if err != nil {
+		t.Fatalf("signing token: %v", err)
+	}
+	rawIDToken, err := jws.CompactSerialize()
+	if err != nil {
+		t.Fatalf("serializing token: %v", err)
+	}
+
+	config := &Config{
+		ClientID: "test-client",
+	}
+	verifier := provider.Verifier(config)
+
+	ctx = context.Background()
+	if _, err := verifier.Verify(ctx, rawIDToken); err != nil {
+		t.Fatalf("verifying token: %v", err)
+	}
+}

oidc/verify.go

@@ -120,8 +120,8 @@ type Config struct {
 }
 
 // VerifierContext returns an IDTokenVerifier that uses the provider's key set to
-// verify JWTs. As opposed to Verifier, the context is used for all requests to
-// the upstream JWKs endpoint.
+// verify JWTs. As opposed to Verifier, the context is used to configure requests
+// to the upstream JWKs endpoint. The provided context's cancellation is ignored.
 func (p *Provider) VerifierContext(ctx context.Context, config *Config) *IDTokenVerifier {
 	return p.newVerifier(NewRemoteKeySet(ctx, p.jwksURL), config)
 }