[refactor] Use base::CheckedNumeric<> in place of manual checks.

content/child/webcrypto/nss/aes_kw_nss.cc

 // Copyright 2014 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 <secerr.h>
 
+#include "base/numerics/safe_math.h"
 #include "content/child/webcrypto/crypto_data.h"
 #include "content/child/webcrypto/nss/aes_key_nss.h"
 #include "content/child/webcrypto/nss/key_nss.h"
 #include "content/child/webcrypto/nss/sym_key_nss.h"
 #include "content/child/webcrypto/nss/util_nss.h"
 #include "content/child/webcrypto/status.h"
 #include "content/child/webcrypto/webcrypto_util.h"
 #include "crypto/scoped_nss_types.h"
 #include "third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h"
 #include "third_party/WebKit/public/platform/WebCryptoKeyAlgorithm.h"
@@ skipping 73 matching lines @@
                        PK11SymKey* wrapping_key,
                        std::vector<uint8_t>* buffer) {
   // The data size must be at least 16 bytes and a multiple of 8 bytes.
   // RFC 3394 does not specify a maximum allowed data length, but since only
   // keys are being wrapped in this application (which are small), a reasonable
   // max limit is whatever will fit into an unsigned. For the max size test,
   // note that AES Key Wrap always adds 8 bytes to the input data size.
   const unsigned int input_length = PK11_GetKeyLength(key);
   DCHECK_GE(input_length, 16u);
   DCHECK((input_length % 8) == 0);
-  if (input_length > UINT_MAX - 8)
-    return Status::ErrorDataTooLarge();
 
   SECItem iv_item = MakeSECItemForBuffer(CryptoData(kAesIv, sizeof(kAesIv)));
   crypto::ScopedSECItem param_item(
       PK11_ParamFromIV(CKM_NSS_AES_KEY_WRAP, &iv_item));
   if (!param_item)
     return Status::ErrorUnexpected();
 
-  const unsigned int output_length = input_length + 8;
-  buffer->resize(output_length);
+  base::CheckedNumeric<unsigned int> output_length = input_length;
+  output_length += 8;
+  if (!output_length.IsValid())
+    return Status::ErrorDataTooLarge();
+
+  buffer->resize(output_length.ValueOrDie());
   SECItem wrapped_key_item = MakeSECItemForBuffer(CryptoData(*buffer));
 
   if (SECSuccess != PK11_WrapSymKey(CKM_NSS_AES_KEY_WRAP,
                                     param_item.get(),
                                     wrapping_key,
                                     key,
                                     &wrapped_key_item)) {
     return Status::OperationError();
   }
-  if (output_length != wrapped_key_item.len)
+  if (output_length.ValueOrDie() != wrapped_key_item.len)
     return Status::ErrorUnexpected();
 
   return Status::Success();
 }
 
 class AesKwCryptoAlgorithmNss : public AesAlgorithm {
  public:
   AesKwCryptoAlgorithmNss()
       : AesAlgorithm(
             CKM_NSS_AES_KEY_WRAP,
@@ skipping 63 matching lines @@
 
 }  // namespace
 
 AlgorithmImplementation* CreatePlatformAesKwImplementation() {
   return new AesKwCryptoAlgorithmNss;
 }
 
 }  // namespace webcrypto
 
 }  // namespace content