Check for integer overflow when HMAC key length as bits cannot fit in an unsigned int.

content/child/webcrypto/nss/hmac_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 <pk11pub.h>
 #include <secerr.h>
 #include <sechash.h>
 
 #include "base/logging.h"
+#include "base/numerics/safe_math.h"
 #include "base/stl_util.h"
 #include "content/child/webcrypto/algorithm_implementation.h"
 #include "content/child/webcrypto/crypto_data.h"
 #include "content/child/webcrypto/jwk.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/secure_util.h"
@@ skipping 81 matching lines @@
                               bool extractable,
                               blink::WebCryptoKeyUsageMask usage_mask,
                               blink::WebCryptoKey* key) const OVERRIDE {
     const blink::WebCryptoAlgorithm& hash =
         algorithm.hmacImportParams()->hash();
 
     CK_MECHANISM_TYPE mechanism = CKM_INVALID_MECHANISM;
     if (!WebCryptoHashToHMACMechanism(hash, &mechanism))
       return Status::ErrorUnsupported();
 
-    // TODO(eroman): check for overflow.
-    unsigned int keylen_bits = key_data.byte_length() * 8;
-    return ImportKeyRawNss(
-        key_data,
-        blink::WebCryptoKeyAlgorithm::createHmac(hash.id(), keylen_bits),
-        extractable,
-        usage_mask,
-        mechanism,
-        CKF_SIGN | CKF_VERIFY,
-        key);
+    base::CheckedNumeric<unsigned int> keylen_bits(key_data.byte_length());
+    keylen_bits *= 8;
+
+    if (!keylen_bits.IsValid())
+      return Status::ErrorDataTooLarge();
+
+    return ImportKeyRawNss(key_data,
+                           blink::WebCryptoKeyAlgorithm::createHmac(
+                               hash.id(), keylen_bits.ValueOrDie()),
+                           extractable,
+                           usage_mask,
+                           mechanism,
+                           CKF_SIGN | CKF_VERIFY,
+                           key);
   }
 
   virtual Status ImportKeyJwk(const CryptoData& key_data,
                               const blink::WebCryptoAlgorithm& algorithm,
                               bool extractable,
                               blink::WebCryptoKeyUsageMask usage_mask,
                               blink::WebCryptoKey* key) const OVERRIDE {
     const char* algorithm_name =
         GetJwkHmacAlgorithmName(algorithm.hmacImportParams()->hash().id());
     if (!algorithm_name)
@@ skipping 95 matching lines @@
 
 }  // namespace
 
 AlgorithmImplementation* CreatePlatformHmacImplementation() {
   return new HmacImplementation;
 }
 
 }  // namespace webcrypto
 
 }  // namespace content