fix(auth): preserve shared signed-session challenge identity

go_backend/extension_signed_session.go

@@ -180,15 +180,17 @@ func (c *signedSessionCoordinator) clearChallenge() {
 	c.pendingExtensionIDs = nil
 }
 
-func (c *signedSessionCoordinator) rememberChallenge(extensionID, authURL, callbackURL, callbackState string) {
+func (c *signedSessionCoordinator) rememberChallenge(request *PendingAuthRequest) {
 	if c.pendingExtensionIDs == nil {
 		c.pendingExtensionIDs = make(map[string]struct{})
 	}
-	c.authURL = authURL
-	c.callbackURL = callbackURL
-	c.callbackState = callbackState
-	c.challengeCreatedAt = time.Now()
-	c.pendingExtensionIDs[extensionID] = struct{}{}
+	c.authURL = request.AuthURL
+	c.callbackURL = request.CallbackURL
+	c.callbackState = request.State
+	// Reusers must register the exact same challenge identity, including its
+	// original timestamp. A fresh time both breaks nonce sharing and extends TTL.
+	c.challengeCreatedAt = request.CreatedAt
+	c.pendingExtensionIDs[request.ExtensionID] = struct{}{}
 }
 
 func (c *signedSessionCoordinator) activeChallenge() bool {
@@ -1285,12 +1287,7 @@ func (r *extensionRuntime) startSignedSessionVerificationLocked(
 	if pending := GetPendingAuthRequest(r.extensionID); pending != nil {
 		if time.Since(pending.CreatedAt) < pendingAuthRequestTTL &&
 			strings.TrimSpace(pending.AuthURL) != "" {
-			coordinator.rememberChallenge(
-				r.extensionID,
-				pending.AuthURL,
-				pending.CallbackURL,
-				pending.State,
-			)
+			coordinator.rememberChallenge(pending)
 			return pending.AuthURL, nil
 		}
 		ClearPendingAuthRequest(r.extensionID)
@@ -1367,12 +1364,7 @@ func (r *extensionRuntime) startSignedSessionVerificationLocked(
 		if registerErr := registerPendingAuthRequest(request); registerErr != nil {
 			finalErr = registerErr
 		} else {
-			coordinator.rememberChallenge(
-				r.extensionID,
-				bootstrap.AuthURL,
-				bootstrap.CallbackURL,
-				bootstrap.CallbackState,
-			)
+			coordinator.rememberChallenge(request)
 			authURL = bootstrap.AuthURL
 		}
 	}

go_backend/extension_signed_session_test.go

@@ -437,6 +437,58 @@ func TestParallelSignedSessionPreflightSharesOneBootstrap(t *testing.T) {
 	if got := calls.Load(); got != 1 {
 		t.Fatalf("parallel preflight bootstrap calls = %d, want 1", got)
 	}
+	pendingA := GetPendingAuthRequest("provider-a")
+	pendingB := GetPendingAuthRequest("provider-b")
+	if pendingA == nil || pendingB == nil || pendingA.State != pendingB.State ||
+		!pendingA.CreatedAt.Equal(pendingB.CreatedAt) {
+		t.Fatal("shared bootstrap must preserve the same nonce and creation time")
+	}
+	if _, err := ConsumeExtensionCallbackState(pendingA.State); err != nil {
+		t.Fatalf("shared callback cannot be consumed: %v", err)
+	}
+	if GetPendingAuthRequest("provider-a") != nil || GetPendingAuthRequest("provider-b") != nil {
+		t.Fatal("consuming a shared callback must clear every alias")
+	}
+	if _, err := ConsumeExtensionCallbackState(pendingA.State); err == nil {
+		t.Fatal("shared callback replay was accepted")
+	}
+}
+
+func TestRememberSignedSessionChallengePreservesOriginalLifetime(t *testing.T) {
+	request := &PendingAuthRequest{
+		ExtensionID: "remember-original", AuthURL: "https://auth.example.com/challenge",
+		CallbackURL: "spotiflac://callback", State: "remember-original-state",
+		CreatedAt: time.Now().Add(-2 * time.Minute),
+	}
+	if err := registerPendingAuthRequest(request); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		ClearPendingAuthRequest("remember-original")
+		ClearPendingAuthRequest("remember-shared")
+	})
+	coordinator := &signedSessionCoordinator{}
+	coordinator.rememberChallenge(request)
+	if !coordinator.challengeCreatedAt.Equal(request.CreatedAt) {
+		t.Fatal("remembering an existing challenge reset its TTL")
+	}
+	runtime := &extensionRuntime{extensionID: "remember-shared"}
+	coordinator.mu.Lock()
+	_, err := runtime.startSignedSessionVerificationLocked(SignedSessionConfig{}, coordinator, "test")
+	coordinator.mu.Unlock()
+	if err != nil {
+		t.Fatalf("reusing a remembered challenge: %v", err)
+	}
+	shared := GetPendingAuthRequest("remember-shared")
+	if shared == nil || !shared.CreatedAt.Equal(request.CreatedAt) {
+		t.Fatal("shared request lost the original challenge timestamp")
+	}
+	expired := *request
+	expired.CreatedAt = time.Now().Add(-pendingAuthRequestTTL - time.Second)
+	coordinator.rememberChallenge(&expired)
+	if coordinator.activeChallenge() {
+		t.Fatal("remembering an expired challenge made it active again")
+	}
 }
 
 func TestParallelSignedSessionPreflightSharesBootstrapFailure(t *testing.T) {