From 7f59498d7097ca3905b4401463347e139bc905c5 Mon Sep 17 00:00:00 2001
From: Martin Kreichgauer <martinkr@google.com>
Date: Fri, 31 Jul 2026 14:20:44 -0700
Subject: [PATCH] webauthn: gate remoteDesktopClientOverride for all caller types

ValidateDomainAndRelyingPartyID returned early for callers whose
origin/RP-ID validation is delegated to the embedder (e.g.
chrome-extension:// origins) without first evaluating
OriginMayUseRemoteDesktopClientOverride against the caller. As a result,
such a caller could supply the remoteDesktopClientOverride extension and
have its origin written into the browser-generated clientDataJSON
regardless of whether the caller origin was on the device-level
allowlist.

In practice, OverrideCallerOriginAndRelyingPartyIdValidation severely
limits the set of origins an extension could claim by doing this, but
nevertheless it is a good idea to tighten this up.

Hoist the policy check to the start of the function so that it runs
before every early-return path, and replace the now redundant inline
check with a value_or() for the relying-party-origin assignment.

BUG=499217288
TAG=agy
CONV=b7e1564f-5289-478d-bba4-48195f9673f6

Change-Id: I4a423db7677e3abd875219621daec6ca9b95c884
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8140023
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Martin Kreichgauer <martinkr@google.com>
Cr-Commit-Position: refs/heads/main@{#1672106}
---

diff --git a/content/browser/webauth/authenticator_impl_unittest.cc b/content/browser/webauth/authenticator_impl_unittest.cc
index 5e9f2feb..6ef94c5 100644
--- a/content/browser/webauth/authenticator_impl_unittest.cc
+++ b/content/browser/webauth/authenticator_impl_unittest.cc
@@ -3249,6 +3249,40 @@
   }
 }
 
+// A Chrome extension should not be authorized to use the
+// remoteDesktopClientOverride request extension.
+TEST_F(AuthenticatorImplRemoteDesktopClientOverrideTest,
+       ExtensionCallerOrigin) {
+  static const std::string kExtensionOrigin =
+      base::StrCat({kExtensionScheme, "://abcdefg"});
+  test_client_.GetTestWebAuthenticationDelegate()->permit_extensions = true;
+
+  {
+    PublicKeyCredentialCreationOptionsPtr options =
+        GetTestPublicKeyCredentialCreationOptions();
+    options->relying_party.id = kExampleRpId;
+    options->remote_desktop_client_override = RemoteDesktopClientOverride::New(
+        url::Origin::Create(GURL(kExampleOrigin)), true);
+    EXPECT_EQ(
+        AuthenticatorMakeCredential(std::move(options)).status,
+        AuthenticatorStatus::REMOTE_DESKTOP_CLIENT_OVERRIDE_NOT_AUTHORIZED);
+  }
+
+  {
+    PublicKeyCredentialRequestOptionsPtr options =
+        GetTestPublicKeyCredentialRequestOptions();
+    options->relying_party_id = kExampleRpId;
+    options->extensions->remote_desktop_client_override =
+        RemoteDesktopClientOverride::New(
+            url::Origin::Create(GURL(kExampleOrigin)), true);
+    ASSERT_TRUE(virtual_device_factory_->mutable_state()->InjectRegistration(
+        options->allow_credentials[0].id, kExtensionOrigin));
+    EXPECT_EQ(
+        AuthenticatorGetAssertion(std::move(options)).status,
+        AuthenticatorStatus::REMOTE_DESKTOP_CLIENT_OVERRIDE_NOT_AUTHORIZED);
+  }
+}
+
 TEST_F(AuthenticatorImplRemoteDesktopClientOverrideTest,
        GetAssertionImmediateMediation) {
   // Verify that an authorized origin may not use the extension with immediate
diff --git a/content/browser/webauth/webauth_request_security_checker_impl.cc b/content/browser/webauth/webauth_request_security_checker_impl.cc
index 8e49065..a40d72b 100644
--- a/content/browser/webauth/webauth_request_security_checker_impl.cc
+++ b/content/browser/webauth/webauth_request_security_checker_impl.cc
@@ -159,6 +159,23 @@
     RequestType request_type,
     const std::optional<url::Origin>& remote_desktop_client_override_origin,
     base::OnceCallback<void(blink::mojom::AuthenticatorStatus)> callback) {
+  if (remote_desktop_client_override_origin.has_value()) {
+    // SECURITY: `remote_desktop_client_override_origin` comes from the renderer
+    // process and should not be trusted by default. We only allow its use when
+    // the `caller_origin` is explicitly allowlisted through device level
+    // enterprise policy.
+    if (!GetContentClient()
+             ->browser()
+             ->GetWebAuthenticationDelegate()
+             ->OriginMayUseRemoteDesktopClientOverride(
+                 render_frame_host_->GetBrowserContext(), caller_origin)) {
+      std::move(callback).Run(
+          blink::mojom::AuthenticatorStatus::
+              REMOTE_DESKTOP_CLIENT_OVERRIDE_NOT_AUTHORIZED);
+      return nullptr;
+    }
+  }
+
 #if !BUILDFLAG(IS_ANDROID)
   // Extensions are not supported on Android.
   if (GetContentClient()
@@ -188,24 +205,8 @@
     return nullptr;
   }
 
-  url::Origin relying_party_origin = caller_origin;
-  if (remote_desktop_client_override_origin.has_value()) {
-    // SECURITY: `remote_desktop_client_override_origin` comes from the renderer
-    // process and should not be trusted by default. We only allow its use when
-    // the `caller_origin` is explicitly allowlisted through device level
-    // enterprise policy.
-    if (!GetContentClient()
-             ->browser()
-             ->GetWebAuthenticationDelegate()
-             ->OriginMayUseRemoteDesktopClientOverride(
-                 render_frame_host_->GetBrowserContext(), caller_origin)) {
-      std::move(callback).Run(
-          blink::mojom::AuthenticatorStatus::
-              REMOTE_DESKTOP_CLIENT_OVERRIDE_NOT_AUTHORIZED);
-      return nullptr;
-    }
-    relying_party_origin = remote_desktop_client_override_origin.value();
-  }
+  url::Origin relying_party_origin =
+      remote_desktop_client_override_origin.value_or(caller_origin);
 
   if (webauthn::OriginIsAllowedToClaimRelyingPartyId(relying_party_id,
                                                      relying_party_origin)) {

diff --git a/content/browser/webauth/authenticator_impl_unittest.cc b/content/browser/webauth/authenticator_impl_unittest.cc
index 5e9f2feb..6ef94c5 100644
--- a/content/browser/webauth/authenticator_impl_unittest.cc
+++ b/content/browser/webauth/authenticator_impl_unittest.cc
@@ -3249,6 +3249,40 @@
   }
 }
 
+// A Chrome extension should not be authorized to use the
+// remoteDesktopClientOverride request extension.
+TEST_F(AuthenticatorImplRemoteDesktopClientOverrideTest,
+       ExtensionCallerOrigin) {
+  static const std::string kExtensionOrigin =
+      base::StrCat({kExtensionScheme, "://abcdefg"});
+  test_client_.GetTestWebAuthenticationDelegate()->permit_extensions = true;
+
+  {
+    PublicKeyCredentialCreationOptionsPtr options =
+        GetTestPublicKeyCredentialCreationOptions();
+    options->relying_party.id = kExampleRpId;
+    options->remote_desktop_client_override = RemoteDesktopClientOverride::New(
+        url::Origin::Create(GURL(kExampleOrigin)), true);
+    EXPECT_EQ(
+        AuthenticatorMakeCredential(std::move(options)).status,
+        AuthenticatorStatus::REMOTE_DESKTOP_CLIENT_OVERRIDE_NOT_AUTHORIZED);
+  }
+
+  {
+    PublicKeyCredentialRequestOptionsPtr options =
+        GetTestPublicKeyCredentialRequestOptions();
+    options->relying_party_id = kExampleRpId;
+    options->extensions->remote_desktop_client_override =
+        RemoteDesktopClientOverride::New(
+            url::Origin::Create(GURL(kExampleOrigin)), true);
+    ASSERT_TRUE(virtual_device_factory_->mutable_state()->InjectRegistration(
+        options->allow_credentials[0].id, kExtensionOrigin));
+    EXPECT_EQ(
+        AuthenticatorGetAssertion(std::move(options)).status,
+        AuthenticatorStatus::REMOTE_DESKTOP_CLIENT_OVERRIDE_NOT_AUTHORIZED);
+  }
+}
+
 TEST_F(AuthenticatorImplRemoteDesktopClientOverrideTest,
        GetAssertionImmediateMediation) {
   // Verify that an authorized origin may not use the extension with immediate