[gin] Fingerprint the V8 snapshot files on Windows and verify before loading the snapshot.

gin/isolate_holder.cc

Index: gin/isolate_holder.cc
diff --git a/gin/isolate_holder.cc b/gin/isolate_holder.cc
index 2b6d64b35c042b2e183e6cc0c963c2f2ab96d392..149bc10eb86b0eb43add0098ce904d614388fc41 100644
--- a/gin/isolate_holder.cc
+++ b/gin/isolate_holder.cc
@@ -12,6 +12,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/rand_util.h"
 #include "base/sys_info.h"
+#include "crypto/sha2.h"
 #include "gin/array_buffer.h"
 #include "gin/debug_impl.h"
 #include "gin/function_template.h"
@@ -19,12 +20,12 @@
 #include "gin/public/v8_platform.h"
 #include "gin/run_microtasks_observer.h"
 
-#ifdef V8_USE_EXTERNAL_STARTUP_DATA
-#ifdef OS_MACOSX
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+#if defined(OS_MACOSX)
 #include "base/mac/foundation_util.h"
-#endif  // OS_MACOSX
+#endif  // defined(OS_MACOSX)
 #include "base/path_service.h"
-#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+#endif  // defined(V8_USE_EXTERNAL_STARTUP_DATA)
 
 namespace gin {
 
@@ -40,7 +41,7 @@ bool GenerateEntropy(unsigned char* buffer, size_t amount) {
 base::MemoryMappedFile* g_mapped_natives = NULL;
 base::MemoryMappedFile* g_mapped_snapshot = NULL;
 
-#ifdef V8_USE_EXTERNAL_STARTUP_DATA
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
 bool MapV8Files(base::FilePath* natives_path, base::FilePath* snapshot_path,
                 int natives_fd = -1, int snapshot_fd = -1) {
   int flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
@@ -72,6 +73,18 @@ bool MapV8Files(base::FilePath* natives_path, base::FilePath* snapshot_path,
   return true;
 }
 
+#if defined(OS_WIN)

[grt (UTC plus 2), 2015/01/08 17:46:35]

i can imagine other platforms eventually wanting the verified path as well (why
not on OSX?). how about switching from OS_WIN to something like
V8_VERIFY_EXTERNAL_STARTUP_DATA that is currently only set for OS_WIN?

[rmcilroy, 2015/01/08 18:54:14]

Done.

+bool VerifyV8SnapshotFile(base::MemoryMappedFile* snapshot_file,
+                          const unsigned char* fingerprint) {
+  unsigned char output[crypto::kSHA256Length];
+  crypto::SHA256HashString(
+      base::StringPiece(reinterpret_cast<const char*>(snapshot_file->data()),
+                        snapshot_file->length()),
+      output, sizeof(output));
+  return !memcmp(fingerprint, output, sizeof(output));
+}
+#endif  // defined(OS_WIN)
+
 #if !defined(OS_MACOSX)
 const int v8_snapshot_dir =
 #if defined(OS_ANDROID)
@@ -85,10 +98,16 @@ const int v8_snapshot_dir =
 
 }  // namespace
 
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+
+#if defined(OS_WIN)
+// Declared in gen/gin/v8_snapshot_fingerprint.cc

[grt (UTC plus 2), 2015/01/08 17:46:35]

ping: Declared -> Defined

[rmcilroy, 2015/01/08 18:54:14]

Oops, sorry missed this. Done.

+extern const unsigned char g_natives_fingerprint[];
+extern const unsigned char g_snapshot_fingerprint[];
+#endif  // defined(OS_WIN)
 
-#ifdef V8_USE_EXTERNAL_STARTUP_DATA
 // static
-bool IsolateHolder::LoadV8Snapshot() {
+bool IsolateHolder::LoadV8SnapshotCommon() {
   if (g_mapped_natives && g_mapped_snapshot)
     return true;
 
@@ -118,7 +137,23 @@ bool IsolateHolder::LoadV8SnapshotFD(int natives_fd, int snapshot_fd) {
 
   return MapV8Files(NULL, NULL, natives_fd, snapshot_fd);
 }
-#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+
+#if defined(OS_WIN)
+// static
+bool IsolateHolder::LoadAndVerifyV8Snapshot() {
+  if (!LoadV8SnapshotCommon())
+    return false;
+  return VerifyV8SnapshotFile(g_mapped_natives, g_natives_fingerprint) &&
+         VerifyV8SnapshotFile(g_mapped_snapshot, g_snapshot_fingerprint);
+}
+#else
+// static
+bool IsolateHolder::LoadV8Snapshot() {
+  return LoadV8SnapshotCommon();
+}
+#endif  // defined(OS_WIN)
+
+#endif  // defined(V8_USE_EXTERNAL_STARTUP_DATA)
 
 //static
 void IsolateHolder::GetV8ExternalSnapshotData(const char** natives_data_out,
@@ -193,7 +228,7 @@ void IsolateHolder::Initialize(ScriptMode mode,
     v8::V8::SetFlagsFromString(v8_flags, sizeof(v8_flags) - 1);
   }
   v8::V8::SetEntropySource(&GenerateEntropy);
-#ifdef V8_USE_EXTERNAL_STARTUP_DATA
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
   v8::StartupData natives;
   natives.data = reinterpret_cast<const char*>(g_mapped_natives->data());
   natives.raw_size = static_cast<int>(g_mapped_natives->length());
@@ -203,7 +238,7 @@ void IsolateHolder::Initialize(ScriptMode mode,
   snapshot.data = reinterpret_cast<const char*>(g_mapped_snapshot->data());
   snapshot.raw_size = static_cast<int>(g_mapped_snapshot->length());
   v8::V8::SetSnapshotDataBlob(&snapshot);
-#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+#endif  // defined(V8_USE_EXTERNAL_STARTUP_DATA)
   v8::V8::Initialize();
   v8_is_initialized = true;
 }