Refactor CRX verification in preparation to support CRX₃ files.

components/crx_file/crx2_file.cc

Index: components/crx_file/crx2_file.cc
diff --git a/components/crx_file/crx2_file.cc b/components/crx_file/crx2_file.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2c37bfe797934c96e38efb86e139d4d3050e91a6
--- /dev/null
+++ b/components/crx_file/crx2_file.cc
@@ -0,0 +1,79 @@
+// 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 "components/crx_file/crx2_file.h"
+
+#include "base/base64.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/files/scoped_file.h"
+#include "base/macros.h"
+#include "base/memory/ptr_util.h"
+#include "base/numerics/safe_math.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+#include "components/crx_file/id_util.h"
+#include "crypto/secure_hash.h"
+#include "crypto/sha2.h"
+#include "crypto/signature_verifier.h"
+
+namespace crx_file {
+
+namespace {
+
+// The current version of the crx format.
+static const uint32_t kCurrentVersion = 2;
+
+// The current version of the crx diff format.
+static const uint32_t kCurrentDiffVersion = 0;
+
+// The maximum size the crx parser will tolerate for a public key.
+static const uint32_t kMaxPublicKeySize = 1 << 16;
+
+// The maximum size the crx parser will tolerate for a signature.
+static const uint32_t kMaxSignatureSize = 1 << 16;
+
+}  // namespace
+
+std::unique_ptr<Crx2File> Crx2File::Create(const uint32_t key_size,
+                                           const uint32_t signature_size,
+                                           Crx2File::Error* error) {
+  Crx2File::Header header;
+  memcpy(&header.magic, kCrx2FileHeaderMagic, kCrx2FileHeaderMagicSize);
+  header.version = kCurrentVersion;
+  header.key_size = key_size;
+  header.signature_size = signature_size;
+  if (HeaderIsValid(header, error))
+    return base::WrapUnique(new Crx2File(header));
+  return nullptr;
+}
+
+Crx2File::Crx2File(const Header& header) : header_(header) {}
+
+bool Crx2File::HeaderIsValid(const Crx2File::Header& header,
+                             Crx2File::Error* error) {
+  bool valid = false;
+  bool diffCrx = false;
+  if (!strncmp(kCrxDiffFileHeaderMagic, header.magic, sizeof(header.magic)))
+    diffCrx = true;
+  if (strncmp(kCrx2FileHeaderMagic, header.magic, sizeof(header.magic)) &&
+      !diffCrx)
+    *error = kWrongMagic;
+  else if (header.version != kCurrentVersion &&
+           !(diffCrx && header.version == kCurrentDiffVersion))
+    *error = kInvalidVersion;
+  else if (header.key_size > kMaxPublicKeySize)
+    *error = kInvalidKeyTooLarge;
+  else if (header.key_size == 0)
+    *error = kInvalidKeyTooSmall;
+  else if (header.signature_size > kMaxSignatureSize)
+    *error = kInvalidSignatureTooLarge;
+  else if (header.signature_size == 0)
+    *error = kInvalidSignatureTooSmall;
+  else
+    valid = true;
+  return valid;
+}
+
+}  // namespace crx_file