oauth: use provider-specific key for verification (fixes #248)

CHANGELOG.md

@@ -4,6 +4,10 @@ Based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## HEAD
 
+### Fixed
+
+* Use provider-specific signing key for verification.
+
 ## 1.18.1
 
 ### Added

app/tokens/oauth/oauth.go

@@ -36,21 +36,21 @@ func (c *Claims) Sign(signingKey jose.SigningKey) (string, error) {
 
 // Parse will deserialize a string into Claims if and only if the claims pass all validations. In
 // this case the token must contain a nonce already known from a different channel (like a cookie).
-func Parse(tokenStr string, cfg *app.Config, nonce string) (*Claims, error) {
+func Parse(tokenStr string, signingKey interface{}, authNURL string, nonce string) (*Claims, error) {
 	token, err := jwt.ParseSigned(tokenStr)
 	if err != nil {
 		return nil, errors.Wrap(err, "ParseSigned")
 	}
 
 	claims := Claims{}
-	err = token.Claims(cfg.OAuthSigningKey, &claims)
+	err = token.Claims(signingKey, &claims)
 	if err != nil {
 		return nil, errors.Wrap(err, "Claims")
 	}
 
 	err = claims.Claims.Validate(jwt.Expected{
-		Audience: jwt.Audience{cfg.AuthNURL.String()},
-		Issuer:   cfg.AuthNURL.String(),
+		Audience: jwt.Audience{authNURL},
+		Issuer:   authNURL,
 	})
 	if err != nil {
 		return nil, errors.Wrap(err, "Validate")

app/tokens/oauth/oauth_test.go

@@ -29,21 +29,25 @@ func TestOAuthToken(t *testing.T) {
 		assert.True(t, token.Audience.Contains("https://authn.example.com"))
 		assert.NotEmpty(t, token.IssuedAt)
 
-		tokenStr, err := token.Sign(jose.SigningKey{Algorithm: jose.HS256, Key: cfg.OAuthSigningKey})
+		key := jose.SigningKey{Algorithm: jose.HS256, Key: cfg.OAuthSigningKey}
+
+		tokenStr, err := token.Sign(key)
 		require.NoError(t, err)
 
-		_, err = oauth.Parse(tokenStr, cfg, nonce)
+		_, err = oauth.Parse(tokenStr, key.Key, cfg.AuthNURL.String(), nonce)
 		require.NoError(t, err)
 	})
 
 	t.Run("parsing with an unknown nonce", func(t *testing.T) {
 		token, err := oauth.New(cfg, nonce, "https://app.example.com/return")
 		require.NoError(t, err)
 
-		tokenStr, err := token.Sign(jose.SigningKey{Algorithm: jose.HS256, Key: cfg.OAuthSigningKey})
+		key := jose.SigningKey{Algorithm: jose.HS256, Key: cfg.OAuthSigningKey}
+
+		tokenStr, err := token.Sign(key)
 		require.NoError(t, err)
 
-		_, err = oauth.Parse(tokenStr, cfg, "wrong")
+		_, err = oauth.Parse(tokenStr, key.Key, cfg.AuthNURL.String(), "wrong")
 		assert.Error(t, err)
 	})
 
@@ -52,11 +56,16 @@ func TestOAuthToken(t *testing.T) {
 			AuthNURL:        cfg.AuthNURL,
 			OAuthSigningKey: []byte("old-a-reno"),
 		}
+		oldKey := jose.SigningKey{Algorithm: jose.HS256, Key: oldCfg.OAuthSigningKey}
+
 		token, err := oauth.New(cfg, nonce, "https://app.example.com/return")
 		require.NoError(t, err)
-		tokenStr, err := token.Sign(jose.SigningKey{Algorithm: jose.HS256, Key: oldCfg.OAuthSigningKey})
+
+		tokenStr, err := token.Sign(oldKey)
 		require.NoError(t, err)
-		_, err = oauth.Parse(tokenStr, cfg, nonce)
+
+		key := jose.SigningKey{Algorithm: jose.HS256, Key: cfg.OAuthSigningKey}
+		_, err = oauth.Parse(tokenStr, key.Key, cfg.AuthNURL.String(), nonce)
 		assert.Error(t, err)
 	})
 
@@ -67,9 +76,12 @@ func TestOAuthToken(t *testing.T) {
 		}
 		token, err := oauth.New(&oldCfg, nonce, "https://app.example.com/return")
 		require.NoError(t, err)
-		tokenStr, err := token.Sign(jose.SigningKey{Algorithm: jose.HS256, Key: cfg.OAuthSigningKey})
+
+		key := jose.SigningKey{Algorithm: jose.HS256, Key: cfg.OAuthSigningKey}
+
+		tokenStr, err := token.Sign(key)
 		require.NoError(t, err)
-		_, err = oauth.Parse(tokenStr, cfg, nonce)
+		_, err = oauth.Parse(tokenStr, key.Key, cfg.AuthNURL.String(), nonce)
 		assert.Error(t, err)
 	})
 }

server/handlers/get_oauth_return.go

@@ -16,8 +16,8 @@ func GetOauthReturn(app *app.App, providerName string) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		provider := app.OauthProviders[providerName]
 
-		// verify the state and nonce
-		state, err := getState(app.Config, r)
+		// verify the state and nonce using the key associated with the provider's signing key.
+		state, err := getState(app.Config, r, provider.SigningKey().Key)
 		if err != nil {
 			app.Reporter.ReportRequestError(errors.Wrap(err, "getState"), r)
 			failsafe := app.Config.ApplicationDomains[0].URL()

server/handlers/util.go

@@ -31,12 +31,12 @@ func nonceCookie(cfg *app.Config, val string) *http.Cookie {
 }
 
 // getState returns a verified state token using the nonce cookie
-func getState(cfg *app.Config, r *http.Request) (*oauth.Claims, error) {
+func getState(cfg *app.Config, r *http.Request, verificationKey interface{}) (*oauth.Claims, error) {
 	nonce, err := r.Cookie(cfg.OAuthCookieName)
 	if err != nil {
 		return nil, errors.Wrap(err, "Cookie")
 	}
-	state, err := oauth.Parse(r.FormValue("state"), cfg, nonce.Value)
+	state, err := oauth.Parse(r.FormValue("state"), verificationKey, cfg.AuthNURL.String(), nonce.Value)
 	if err != nil {
 		return nil, errors.Wrap(err, "Parse")
 	}