From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jeremy Apthorp <nornagon@nornagon.net>
Date: Wed, 28 Nov 2018 13:20:27 -0800
Subject: support_mixed_sandbox_with_zygote.patch

On Linux, Chromium launches all new renderer processes via a "zygote"
process which has the sandbox pre-initialized (see
//docs/linux_zygote.md). In order to support mixed-sandbox mode, in
which some renderers are launched with the sandbox engaged and others
without it, we need the option to launch non-sandboxed renderers without
going through the zygote.

Chromium already supports a `--no-zygote` flag, but it turns off the
zygote completely, and thus also disables sandboxing. This patch allows
the `--no-zygote` flag to affect renderer processes on a case-by-case
basis, checking immediately prior to launch whether to go through the
zygote or not based on the command-line of the to-be-launched renderer.

This patch could conceivably be upstreamed, as it does not affect
production Chromium (which does not use the `--no-zygote` flag).
However, the patch would need to be reviewed by the security team, as it
does touch a security-sensitive class.

diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index fd695ec92ca4ff87aaa08c09aea4d1e2b36dddf9..e17653460749d455b4732d63195395fe3ea1d864 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -1698,9 +1698,15 @@ bool RenderProcessHostImpl::Init() {
     std::unique_ptr<SandboxedProcessLauncherDelegate> sandbox_delegate =
         std::make_unique<RendererSandboxedProcessLauncherDelegateWin>(
             *cmd_line, IsPdf(), /*is_jit_disabled=*/IsPdf());
+#else
+#if BUILDFLAG(USE_ZYGOTE)
+    bool use_zygote = !cmd_line->HasSwitch(switches::kNoZygote);
+    std::unique_ptr<SandboxedProcessLauncherDelegate> sandbox_delegate =
+        std::make_unique<RendererSandboxedProcessLauncherDelegate>(use_zygote);
 #else
     std::unique_ptr<SandboxedProcessLauncherDelegate> sandbox_delegate =
         std::make_unique<RendererSandboxedProcessLauncherDelegate>();
+#endif
 #endif
 
     auto tracing_config_memory_region =
diff --git a/content/browser/renderer_host/renderer_sandboxed_process_launcher_delegate.cc b/content/browser/renderer_host/renderer_sandboxed_process_launcher_delegate.cc
index 2c724b73a55fa21154ff8cedd41d3ca5738dfa76..b3f5973a4b686542d46d8338722f5fe42c86c529 100644
--- a/content/browser/renderer_host/renderer_sandboxed_process_launcher_delegate.cc
+++ b/content/browser/renderer_host/renderer_sandboxed_process_launcher_delegate.cc
@@ -35,6 +35,9 @@ namespace content {
 
 #if BUILDFLAG(USE_ZYGOTE)
 ZygoteCommunication* RendererSandboxedProcessLauncherDelegate::GetZygote() {
+  if (!use_zygote_) {
+    return nullptr;
+  }
   const base::CommandLine& browser_command_line =
       *base::CommandLine::ForCurrentProcess();
   base::CommandLine::StringType renderer_prefix =
@@ -70,6 +73,9 @@ RendererSandboxedProcessLauncherDelegateWin::
       is_pdf_renderer_(is_pdf_renderer) {
   // PDF renderers must be jitless.
   CHECK(!is_pdf_renderer || is_jit_disabled);
+#if BUILDFLAG(USE_ZYGOTE)
+  use_zygote_ = !cmd_line->HasSwitch(switches::kNoZygote);
+#endif
   if (is_jit_disabled) {
     dynamic_code_can_be_disabled_ = true;
     return;
diff --git a/content/browser/renderer_host/renderer_sandboxed_process_launcher_delegate.h b/content/browser/renderer_host/renderer_sandboxed_process_launcher_delegate.h
index 00038da2c15696b361aea1469ccf73307e44963e..7ccfbf11ecfd56fd165915baa85919eaf2e923b9 100644
--- a/content/browser/renderer_host/renderer_sandboxed_process_launcher_delegate.h
+++ b/content/browser/renderer_host/renderer_sandboxed_process_launcher_delegate.h
@@ -18,6 +18,11 @@ class CONTENT_EXPORT RendererSandboxedProcessLauncherDelegate
  public:
   RendererSandboxedProcessLauncherDelegate() = default;
 
+#if BUILDFLAG(USE_ZYGOTE)
+  RendererSandboxedProcessLauncherDelegate(bool use_zygote):
+    use_zygote_(use_zygote) {}
+#endif
+
   ~RendererSandboxedProcessLauncherDelegate() override = default;
 
 #if BUILDFLAG(USE_ZYGOTE)
@@ -30,6 +35,11 @@ class CONTENT_EXPORT RendererSandboxedProcessLauncherDelegate
 
   // sandbox::policy::SandboxDelegate:
   sandbox::mojom::Sandbox GetSandboxType() override;
+
+ private:
+#if BUILDFLAG(USE_ZYGOTE)
+  bool use_zygote_ = true;
+#endif
 };
 
 #if BUILDFLAG(IS_WIN)
