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

content/child/webcrypto/nss/aes_cbc_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 <cryptohi.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/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"
 
 namespace content {
@@ skipping 26 matching lines @@
     return Status::OperationError();
 
   crypto::ScopedPK11Context context(PK11_CreateContextBySymKey(
       CKM_AES_CBC_PAD, operation, sym_key, param.get()));
 
   if (!context.get())
     return Status::OperationError();
 
   // Oddly PK11_CipherOp takes input and output lengths as "int" rather than
   // "unsigned int". Do some checks now to avoid integer overflowing.
-  if (data.byte_length() >= INT_MAX - AES_BLOCK_SIZE) {
+  base::CheckedNumeric<int> output_max_len = data.byte_length();
+  output_max_len += AES_BLOCK_SIZE;
+  if (!output_max_len.IsValid()) {
     // TODO(eroman): Handle this by chunking the input fed into NSS. Right now
     // it doesn't make much difference since the one-shot API would end up
     // blowing out the memory and crashing anyway.
     return Status::ErrorDataTooLarge();
   }
 
   // PK11_CipherOp does an invalid memory access when given empty decryption
   // input, or input which is not a multiple of the block size. See also
   // https://bugzilla.mozilla.com/show_bug.cgi?id=921687.
   if (operation == CKA_DECRYPT &&
       (data.byte_length() == 0 || (data.byte_length() % AES_BLOCK_SIZE != 0))) {
     return Status::OperationError();
   }
 
   // TODO(eroman): Refine the output buffer size. It can be computed exactly for
   //               encryption, and can be smaller for decryption.
-  unsigned int output_max_len = data.byte_length() + AES_BLOCK_SIZE;
-  CHECK_GT(output_max_len, data.byte_length());
-
-  buffer->resize(output_max_len);
+  buffer->resize(output_max_len.ValueOrDie());
 
   unsigned char* buffer_data = Uint8VectorStart(buffer);
 
   int output_len;
   if (SECSuccess != PK11_CipherOp(context.get(),
                                   buffer_data,
                                   &output_len,
                                   buffer->size(),
                                   data.bytes(),
                                   data.byte_length())) {
     return Status::OperationError();
   }
 
   unsigned int final_output_chunk_len;
-  if (SECSuccess != PK11_DigestFinal(context.get(),
-                                     buffer_data + output_len,
-                                     &final_output_chunk_len,
-                                     output_max_len - output_len)) {
+  if (SECSuccess !=
+      PK11_DigestFinal(context.get(),
+                       buffer_data + output_len,
+                       &final_output_chunk_len,
+                       (output_max_len - output_len).ValueOrDie())) {
     return Status::OperationError();
   }
 
   buffer->resize(final_output_chunk_len + output_len);
   return Status::Success();
 }
 
 class AesCbcImplementation : public AesAlgorithm {
  public:
   AesCbcImplementation() : AesAlgorithm(CKM_AES_CBC, "CBC") {}
@@ skipping 15 matching lines @@
 
 }  // namespace
 
 AlgorithmImplementation* CreatePlatformAesCbcImplementation() {
   return new AesCbcImplementation;
 }
 
 }  // namespace webcrypto
 
 }  // namespace content