Send the public origin on the in-cluster Authelia token request.

The token POST stays on tokenBaseURL. When that origin is not the browser-facing HTTPS origin, the request sets X-Forwarded-Proto and X-Forwarded-Host from that origin. Browser redirects are unchanged.

Assistant: grok
Assistant-Session: 01a0e29c-2e57-7342-a500-8f3b43b5fefd

src/internal/adapters/authelia/adapter.go

@@ -155,21 +155,11 @@ type tokenResponse struct {
 
 // exchangeCode sends a POST to Authelia's token endpoint and returns the
 // parsed token response. On any HTTP or status error it returns a non-nil error.
-func (a *AutheliaAdapter) exchangeCode(_ context.Context, code string) (*tokenResponse, error) {
+func (a *AutheliaAdapter) exchangeCode(ctx context.Context, code string) (*tokenResponse, error) {
-	tokenURL := strings.TrimRight(a.tokenBaseURL(), "/") + "/api/oidc/token"
+	req, err := a.newTokenRequest(ctx, code)
-
-	body := url.Values{}
-	body.Set("grant_type", "authorization_code")
-	body.Set("code", code)
-	body.Set("redirect_uri", a.cfg.RedirectURI)
-	body.Set("client_id", a.cfg.ClientID)
-
-	req, err := http.NewRequest(http.MethodPost, tokenURL, strings.NewReader(body.Encode()))
 	if err != nil {
-		return nil, fmt.Errorf("authelia: build token request: %w", err)
+		return nil, err
 	}
-	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
-	req.SetBasicAuth(a.cfg.ClientID, a.cfg.ClientSecret)
 
 	resp, err := a.client.Do(req)
 	if err != nil {
@@ -232,6 +222,49 @@ func (a *AutheliaAdapter) tokenBaseURL() string {
 	return a.cfg.BaseURL
 }
 
+// newTokenRequest is the back-channel authorization-code exchange. The URL
+// stays on tokenBaseURL. When that origin is not the browser-facing HTTPS
+// origin, the request carries that origin in X-Forwarded-Proto and
+// X-Forwarded-Host so Authelia can derive the public issuer. Authelia 4.39
+// rejects a plain-http scheme. Browser redirects are unchanged.
+func (a *AutheliaAdapter) newTokenRequest(ctx context.Context, code string) (*http.Request, error) {
+	tokenURL := strings.TrimRight(a.tokenBaseURL(), "/") + "/api/oidc/token"
+
+	body := url.Values{}
+	body.Set("grant_type", "authorization_code")
+	body.Set("code", code)
+	body.Set("redirect_uri", a.cfg.RedirectURI)
+	body.Set("client_id", a.cfg.ClientID)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, tokenURL, strings.NewReader(body.Encode()))
+	if err != nil {
+		return nil, fmt.Errorf("authelia: build token request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.SetBasicAuth(a.cfg.ClientID, a.cfg.ClientSecret)
+	a.setPublicOriginHeaders(req)
+	return req, nil
+}
+
+// setPublicOriginHeaders annotates a split-horizon token request. A public
+// origin that is not HTTPS is left unset: sending X-Forwarded-Proto: http is
+// the value Authelia 4.39 refuses. Same-origin calls are left unset too.
+func (a *AutheliaAdapter) setPublicOriginHeaders(req *http.Request) {
+	public, err := url.Parse(a.authorizeBaseURL())
+	if err != nil || public.Scheme != "https" || public.Host == "" {
+		return
+	}
+	token, err := url.Parse(req.URL.String())
+	if err != nil || token.Host == "" {
+		return
+	}
+	if token.Scheme == public.Scheme && strings.EqualFold(token.Host, public.Host) {
+		return
+	}
+	req.Header.Set("X-Forwarded-Proto", public.Scheme)
+	req.Header.Set("X-Forwarded-Host", public.Host)
+}
+
 // parseIDTokenClaims extracts the JWT payload claims without verifying
 // anything. It is NOT part of the authentication path: HandleCallback verifies
 // through idTokenVerifier. Kept for tests and diagnostics that need to read a

src/internal/adapters/authelia/adapter_test.go

@@ -295,24 +295,91 @@ func TestHandleCallback_UsesTokenBaseURLWhenConfigured(t *testing.T) {
 		"sub":                "user-uuid-123",
 		"preferred_username": "alice",
 	})
-	var tokenURL string
+	var tokenReq *http.Request
 	client := &mockHTTPClient{
 		doFn: func(req *http.Request) (*http.Response, error) {
-			tokenURL = req.URL.String()
+			if req.URL.Path == "/api/oidc/token" {
+				tokenReq = req
+			}
 			return jsonResponse(tokenBody), nil
 		},
 	}
 
 	cfg := testConfig()
-	cfg.BaseURL = "https://auth.coulomb.social"
+	cfg.BaseURL = "http://authelia.sso.svc.cluster.local:9091"
+	cfg.BrowserBaseURL = "https://auth.coulomb.social"
 	cfg.TokenBaseURL = "http://authelia.sso.svc.cluster.local:9091"
 
 	adapter := authelia.New(cfg, client)
 	if _, err := adapter.HandleCallback(context.Background(), domain.CallbackParams{Code: "code"}); err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
-	if !strings.HasPrefix(tokenURL, "http://authelia.sso.svc.cluster.local:9091") {
+	if tokenReq == nil {
-		t.Errorf("expected token exchange to use TokenBaseURL, got: %s", tokenURL)
+		t.Fatal("token endpoint was not called")
+	}
+	if tokenReq.URL.String() != "http://authelia.sso.svc.cluster.local:9091/api/oidc/token" {
+		t.Errorf("token exchange URL: got %s", tokenReq.URL.String())
+	}
+	if tokenReq.Host != "authelia.sso.svc.cluster.local:9091" {
+		t.Errorf("token request host: got %s", tokenReq.Host)
+	}
+	if tokenReq.Header.Get("X-Forwarded-Proto") != "https" {
+		t.Errorf("X-Forwarded-Proto: got %q", tokenReq.Header.Get("X-Forwarded-Proto"))
+	}
+	if tokenReq.Header.Get("X-Forwarded-Host") != "auth.coulomb.social" {
+		t.Errorf("X-Forwarded-Host: got %q", tokenReq.Header.Get("X-Forwarded-Host"))
+	}
+	redirect, err := adapter.AuthorizeURL(context.Background(), domain.AuthRequest{
+		State: "s",
+	})
+	if err != nil {
+		t.Fatalf("AuthorizeURL: %v", err)
+	}
+	if !strings.HasPrefix(redirect, "https://auth.coulomb.social/api/oidc/authorization?") {
+		t.Errorf("browser redirect: got %s", redirect)
+	}
+	if strings.Contains(redirect, "authelia.sso.svc.cluster.local") {
+		t.Errorf("browser redirect must stay on the public origin, got %s", redirect)
+	}
+}
+
+func TestTokenRequestOmitsForwardedHeadersForSameOriginAndPlainHTTP(t *testing.T) {
+	cases := []authelia.Config{
+		testConfig(),
+		{
+			BaseURL:        "http://authelia:9091",
+			BrowserBaseURL: "http://localhost:9091",
+			TokenBaseURL:   "http://authelia:9091",
+			ClientID:       "keycape",
+			ClientSecret:   "test-secret",
+			RedirectURI:    "http://localhost:8080/authorize/callback",
+		},
+	}
+	for _, cfg := range cases {
+		t.Run(cfg.BrowserBaseURL+" "+cfg.BaseURL, func(t *testing.T) {
+			var tokenReq *http.Request
+			client := &mockHTTPClient{
+				doFn: func(req *http.Request) (*http.Response, error) {
+					if req.URL.Path == "/api/oidc/token" {
+						tokenReq = req
+					}
+					return jsonResponse(buildTokenResponse(map[string]interface{}{
+						"sub":                "user-uuid-123",
+						"preferred_username": "alice",
+					})), nil
+				},
+			}
+			adapter := authelia.New(cfg, client)
+			if _, err := adapter.HandleCallback(context.Background(), domain.CallbackParams{Code: "code"}); err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			if tokenReq == nil {
+				t.Fatal("token endpoint was not called")
+			}
+			if proto, host := tokenReq.Header.Get("X-Forwarded-Proto"), tokenReq.Header.Get("X-Forwarded-Host"); proto != "" || host != "" {
+				t.Fatalf("forwarded headers set on %s: proto %q host %q", tokenReq.URL.String(), proto, host)
+			}
+		})
 	}
 }
 

src/internal/adapters/authelia/issuer_probe.go

@@ -166,16 +166,13 @@ func (p *IssuerProbe) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 }
 
 func (p *IssuerProbe) verifyCode(ctx context.Context, code string) (string, string) {
-	// Exchange under the same tokenBaseURL/client/redirect as the production
+	// Exchange under the same token request as the production adapter, including
-	// adapter. Use a bounded reader and cancellation; never relay error bodies.
+	// the public-origin headers. Use a bounded reader and cancellation; never
-	tokenURL := strings.TrimRight(p.adapter.tokenBaseURL(), "/") + "/api/oidc/token"
+	// relay error bodies.
-	form := url.Values{"grant_type": {"authorization_code"}, "code": {code}, "redirect_uri": {p.adapter.cfg.RedirectURI}, "client_id": {p.adapter.cfg.ClientID}}
+	req, err := p.adapter.newTokenRequest(ctx, code)
-	req, err := http.NewRequestWithContext(ctx, http.MethodPost, tokenURL, strings.NewReader(form.Encode()))
 	if err != nil {
 		return "", "token_exchange_error"
 	}
-	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
-	req.SetBasicAuth(p.adapter.cfg.ClientID, p.adapter.cfg.ClientSecret)
 	response, err := p.adapter.client.Do(req)
 	if err != nil {
 		return "", "token_exchange_error"

src/internal/adapters/authelia/issuer_probe_test.go

@@ -34,6 +34,9 @@ type probeProvider struct {
 func (p *probeProvider) Do(r *http.Request) (*http.Response, error) {
 	if r.URL.Path == "/api/oidc/token" {
 		p.calls++
+		if r.Header.Get("X-Forwarded-Proto") != "https" || r.Header.Get("X-Forwarded-Host") != "auth.example.com" {
+			p.t.Fatalf("token forwarded headers: proto %q host %q", r.Header.Get("X-Forwarded-Proto"), r.Header.Get("X-Forwarded-Host"))
+		}
 		user, pass, ok := r.BasicAuth()
 		if !ok || user != testConfig().ClientID || pass != testConfig().ClientSecret {
 			p.t.Fatal("wrong client authentication")