Mac Archive Type Sniffing

chrome/browser/safe_browsing/disk_image_type_sniffer_mac.cc

Index: chrome/browser/safe_browsing/disk_image_type_sniffer_mac.cc
diff --git a/chrome/browser/safe_browsing/disk_image_type_sniffer_mac.cc b/chrome/browser/safe_browsing/disk_image_type_sniffer_mac.cc
new file mode 100644
index 0000000000000000000000000000000000000000..323e6f73f4a1de6107583dae010ecbfd5bf17908
--- /dev/null
+++ b/chrome/browser/safe_browsing/disk_image_type_sniffer_mac.cc
@@ -0,0 +1,44 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/safe_browsing/disk_image_type_sniffer_mac.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace safe_browsing {
+
+namespace {
+
+const int kSizeKolySignatureInBytes = 4;

[Robert Sesek, 2017/06/14 15:11:43]

This could now be declared as:

constexpr size_t kSizeKolySignatureInBytes = sizeof(kKolySignature);

[mortonm, 2017/06/14 17:13:15]

Done.

+const int kSizeKolyTrailerInBytes = 512;
+const uint8_t kKolySignature[4] = {'k', 'o', 'l', 'y'};
+
+}  // namespace
+
+DiskImageTypeSnifferMac::DiskImageTypeSnifferMac() {}
+
+// static
+bool DiskImageTypeSnifferMac::IsAppleDiskImage(const base::FilePath& dmg_file) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::FILE);
+
+  base::File file(dmg_file, base::File::FLAG_OPEN | base::File::FLAG_READ);
+  DCHECK(file.IsValid());
+  if (!file.IsValid())
+    return false;
+
+  char data[kSizeKolySignatureInBytes];
+
+  if (file.Seek(base::File::FROM_END, -1 * kSizeKolyTrailerInBytes) == -1)
+    return false;
+
+  if (file.ReadAtCurrentPos(data, kSizeKolySignatureInBytes) !=
+      kSizeKolySignatureInBytes)
+    return false;
+
+  // Compare 4 bytes at given position in file to 'koly' in ascii.

[Robert Sesek, 2017/06/14 15:11:43]

I'd remove this comment now that the signature is written in ASCII above, rather
than as the HEX byte sequence.

[mortonm, 2017/06/14 17:13:15]

Done.

+  return (memcmp(data, kKolySignature, kSizeKolySignatureInBytes) == 0);
+}
+
+DiskImageTypeSnifferMac::~DiskImageTypeSnifferMac() = default;
+
+}  // namespace safe_browsing