From b735f1c6c3cf93c5856057477ece834a6a3a9790 Mon Sep 17 00:00:00 2001
From: Tzarial <zork@google.com>
Date: Mon, 29 Jun 2026 11:59:58 -0700
Subject: [PATCH] Block WebAuthn Authenticator in PDF renderers.

PDF processes are not permitted to access password or
passkey-class data. Refuse to bind the
blink.mojom.Authenticator interface for them, mirroring
the existing protection for PasswordManagerDriver.

Test: AuthenticatorImplTest.PdfProcessBlocked
Change-Id: Id281ea353bccb5c0a949d424cafcdaca98916e51
Fixed: 520018012
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7989199
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Commit-Queue: Tzarial <zork@chromium.org>
Reviewed-by: Caitlin Fischer <caitlinfischer@google.com>
Cr-Commit-Position: refs/heads/main@{#1654244}
---

diff --git a/content/browser/bad_message.h b/content/browser/bad_message.h
index 6304132..558608f 100644
--- a/content/browser/bad_message.h
+++ b/content/browser/bad_message.h
@@ -380,6 +380,7 @@
   RFH_DID_COMMIT_NAVIGATION_WHILE_BFCACHED = 352,
   BIBI_BIND_WEBNN_CONTEXT_PROVIDER_BLOCKED_BY_PERMISSIONS_POLICY = 353,
   BIBI_BIND_WEBNN_WEIGHTS_FILE_CREATOR_BLOCKED_BY_PERMISSIONS_POLICY = 354,
+  RFH_AUTHENTICATOR_PDF_PROCESS_BLOCKED = 355,
 
   // Please add new elements here. The naming convention is abbreviated class
   // name (e.g. RenderFrameHost becomes RFH) plus a unique description of the
diff --git a/content/browser/renderer_host/render_frame_host_impl.cc b/content/browser/renderer_host/render_frame_host_impl.cc
index d0874f2..d1a9233 100644
--- a/content/browser/renderer_host/render_frame_host_impl.cc
+++ b/content/browser/renderer_host/render_frame_host_impl.cc
@@ -15170,6 +15170,17 @@
     return;
   }
 
+  // PDF renderer processes are not permitted to access password/passkey-class
+  // data for any origin (see
+  // ChildProcessSecurityPolicyImpl::IsAccessAllowedForPdfProcess). Refuse to
+  // bind blink.mojom.Authenticator for them, mirroring the gate already present
+  // for blink.mojom.PasswordManagerDriver.
+  if (GetProcess()->IsPdf()) {
+    bad_message::ReceivedBadMessage(
+        GetProcess(), bad_message::RFH_AUTHENTICATOR_PDF_PROCESS_BLOCKED);
+    return;
+  }
+
 #if !BUILDFLAG(IS_ANDROID)
   AuthenticatorImpl::Create(this, std::move(receiver));
 #else
diff --git a/content/browser/webauth/authenticator_impl_unittest.cc b/content/browser/webauth/authenticator_impl_unittest.cc
index c3898b31..7b9d870 100644
--- a/content/browser/webauth/authenticator_impl_unittest.cc
+++ b/content/browser/webauth/authenticator_impl_unittest.cc
@@ -1003,6 +1003,16 @@
   }
 }
 
+TEST_F(AuthenticatorImplTest, PdfProcessBlocked) {
+  process()->SetIsPdf(true);
+
+  mojo::Remote<blink::mojom::Authenticator> authenticator;
+  static_cast<RenderFrameHostImpl*>(main_rfh())
+      ->GetWebAuthenticationService(authenticator.BindNewPipeAndPassReceiver());
+
+  EXPECT_EQ(1, process()->bad_msg_count());
+}
+
 constexpr auto kValidAppIdCases = std::to_array<OriginClaimedAuthorityPair>({
     {"https://example.com", "https://example.com",
      AuthenticatorStatus::SUCCESS},
diff --git a/content/public/test/mock_render_process_host.cc b/content/public/test/mock_render_process_host.cc
index 37a550a..384fe2e 100644
--- a/content/public/test/mock_render_process_host.cc
+++ b/content/public/test/mock_render_process_host.cc
@@ -220,7 +220,11 @@
 }
 
 bool MockRenderProcessHost::IsPdf() {
-  return false;
+  return is_pdf_;
+}
+
+void MockRenderProcessHost::SetIsPdf(bool is_pdf) {
+  is_pdf_ = is_pdf;
 }
 
 void MockRenderProcessHost::OnMediaStreamAdded() {}
diff --git a/content/public/test/mock_render_process_host.h b/content/public/test/mock_render_process_host.h
index 79612bbc..a52cee776 100644
--- a/content/public/test/mock_render_process_host.h
+++ b/content/public/test/mock_render_process_host.h
@@ -99,6 +99,7 @@
   bool AreV8OptimizationsDisabled() override;
   bool DisallowV8FeatureFlagOverrides() override;
   bool IsPdf() override;
+  void SetIsPdf(bool is_pdf);
   void OnMediaStreamAdded() override;
   void OnMediaStreamRemoved() override;
   void OnForegroundServiceWorkerAdded() override;
@@ -349,6 +350,7 @@
   bool delayed_cleanup_ = false;
   bool deletion_callback_called_;
   bool is_for_guests_only_;
+  bool is_pdf_ = false;
   base::Process::Priority priority_;
   bool is_unused_;
   bool is_for_top_chrome_web_ui_ = false;
diff --git a/tools/metrics/histograms/metadata/stability/enums.xml b/tools/metrics/histograms/metadata/stability/enums.xml
index d7d669f..07ba3d9df 100644
--- a/tools/metrics/histograms/metadata/stability/enums.xml
+++ b/tools/metrics/histograms/metadata/stability/enums.xml
@@ -526,6 +526,7 @@
       label="BIBI_BIND_WEBNN_CONTEXT_PROVIDER_BLOCKED_BY_PERMISSIONS_POLICY"/>
   <int value="354"
       label="BIBI_BIND_WEBNN_WEIGHTS_FILE_CREATOR_BLOCKED_BY_PERMISSIONS_POLICY"/>
+  <int value="355" label="RFH_AUTHENTICATOR_PDF_PROCESS_BLOCKED"/>
 </enum>
 
 <enum name="BadMessageReasonExtensions">

diff --git a/content/browser/webauth/authenticator_impl_unittest.cc b/content/browser/webauth/authenticator_impl_unittest.cc
index c3898b31..7b9d870 100644
--- a/content/browser/webauth/authenticator_impl_unittest.cc
+++ b/content/browser/webauth/authenticator_impl_unittest.cc
@@ -1003,6 +1003,16 @@
   }
 }
 
+TEST_F(AuthenticatorImplTest, PdfProcessBlocked) {
+  process()->SetIsPdf(true);
+
+  mojo::Remote<blink::mojom::Authenticator> authenticator;
+  static_cast<RenderFrameHostImpl*>(main_rfh())
+      ->GetWebAuthenticationService(authenticator.BindNewPipeAndPassReceiver());
+
+  EXPECT_EQ(1, process()->bad_msg_count());
+}
+
 constexpr auto kValidAppIdCases = std::to_array<OriginClaimedAuthorityPair>({
     {"https://example.com", "https://example.com",
      AuthenticatorStatus::SUCCESS},
diff --git a/content/public/test/mock_render_process_host.cc b/content/public/test/mock_render_process_host.cc
index 37a550a..384fe2e 100644
--- a/content/public/test/mock_render_process_host.cc
+++ b/content/public/test/mock_render_process_host.cc
@@ -220,7 +220,11 @@
 }
 
 bool MockRenderProcessHost::IsPdf() {
-  return false;
+  return is_pdf_;
+}
+
+void MockRenderProcessHost::SetIsPdf(bool is_pdf) {
+  is_pdf_ = is_pdf;
 }
 
 void MockRenderProcessHost::OnMediaStreamAdded() {}
diff --git a/content/public/test/mock_render_process_host.h b/content/public/test/mock_render_process_host.h
index 79612bbc..a52cee776 100644
--- a/content/public/test/mock_render_process_host.h
+++ b/content/public/test/mock_render_process_host.h
@@ -99,6 +99,7 @@
   bool AreV8OptimizationsDisabled() override;
   bool DisallowV8FeatureFlagOverrides() override;
   bool IsPdf() override;
+  void SetIsPdf(bool is_pdf);
   void OnMediaStreamAdded() override;
   void OnMediaStreamRemoved() override;
   void OnForegroundServiceWorkerAdded() override;
@@ -349,6 +350,7 @@
   bool delayed_cleanup_ = false;
   bool deletion_callback_called_;
   bool is_for_guests_only_;
+  bool is_pdf_ = false;
   base::Process::Priority priority_;
   bool is_unused_;
   bool is_for_top_chrome_web_ui_ = false;