[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..d3858b58e7302125a60e35137a708c77193e944e 100644
--- a/gin/isolate_holder.cc
+++ b/gin/isolate_holder.cc
@@ -12,6 +12,8 @@
 #include "base/message_loop/message_loop.h"
 #include "base/rand_util.h"
 #include "base/sys_info.h"
+#include "crypto/secure_hash.h"
+#include "crypto/sha2.h"
 #include "gin/array_buffer.h"
 #include "gin/debug_impl.h"
 #include "gin/function_template.h"
@@ -72,6 +74,20 @@ bool MapV8Files(base::FilePath* natives_path, base::FilePath* snapshot_path,
   return true;
 }
 
+bool VerifyV8SnapshotFile(base::MemoryMappedFile* snapshot_file,
+                          const unsigned char* fingerprint) {
+  scoped_ptr<crypto::SecureHash> hash(

[grt (UTC plus 2), 2015/01/07 19:27:19]

can you use crypto::SHA256HashString(base::StringPiece(snapshot_file->data(),
snapshot_file->length()), output, sizeof(output)); in place of lines 79-83?

[rmcilroy, 2015/01/08 15:05:35]

Done.

+      crypto::SecureHash::Create(crypto::SecureHash::SHA256));
+  hash->Update(snapshot_file->data(), snapshot_file->length());
+  unsigned char output[crypto::kSHA256Length];
+  hash->Finish(output, sizeof(output));
+  for (size_t i = 0; i < crypto::kSHA256Length; i++) {

[grt (UTC plus 2), 2015/01/07 19:27:19]

?
  return !memcmp(fingerprint, output, sizeof(output)); 

[rmcilroy, 2015/01/08 15:05:35]

Done.

+    if (fingerprint[i] != output[i])
+      return false;
+  }
+  return true;
+}
+
 #if !defined(OS_MACOSX)
 const int v8_snapshot_dir =
 #if defined(OS_ANDROID)
@@ -87,6 +103,11 @@ const int v8_snapshot_dir =
 
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
+
+// Declared in gen/gin/v8_snapshot_fingerprint.cc

[grt (UTC plus 2), 2015/01/07 19:27:19]

Declared -> Defined (these are declarations here)

[rmcilroy, 2015/01/08 15:05:35]

Done.

+extern const unsigned char g_natives_fingerprint[];
+extern const unsigned char g_snapshot_fingerprint[];
+
 // static
 bool IsolateHolder::LoadV8Snapshot() {
   if (g_mapped_natives && g_mapped_snapshot)
@@ -118,6 +139,15 @@ bool IsolateHolder::LoadV8SnapshotFD(int natives_fd, int snapshot_fd) {
 
   return MapV8Files(NULL, NULL, natives_fd, snapshot_fd);
 }
+
+// static
+bool IsolateHolder::LoadAndVerifyV8Snapshot() {
+  if (!LoadV8Snapshot())
+    return false;
+  return VerifyV8SnapshotFile(g_mapped_natives, g_natives_fingerprint) &&
+         VerifyV8SnapshotFile(g_mapped_snapshot, g_snapshot_fingerprint);
+}
+
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
 //static