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 9629e90f7da0468d4bac1c3907a48115ea8673c7..f95b4ab0afe1ef3659777f61a7f5a96e7623a12b 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -1946,6 +1946,10 @@ bool RenderProcessHostImpl::Init() {
     std::unique_ptr<SandboxedProcessLauncherDelegate> sandbox_delegate =
         std::make_unique<RendererSandboxedProcessLauncherDelegateWin>(
             *cmd_line, IsPdf(), IsJitDisabled());
+#elif 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>();
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 0936beb23188f0d07cd5750f3a2e56dc560fdef2..996eab5dae4ffa6b7898cc070de8162ad2130d70 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 =
@@ -71,6 +74,9 @@ RendererSandboxedProcessLauncherDelegateWin::
                                  ->ShouldRestrictCoreSharingOnRenderer()) {
   // 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 b98b23a95003c3e3dd7b2da6a48b956cdbeb5251..0597eca8efa2bea2cb800c6919b59dfb64c87083 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)
