[webcrypto] Simplify the AES-KW workaround for NSS and remove valgrind suppression

content/child/webcrypto/platform_crypto_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 "content/child/webcrypto/platform_crypto.h"
 
 #include <cryptohi.h>
 #include <pk11pub.h>
 #include <sechash.h>
 
@@ skipping 501 matching lines @@
                                                      &cipher_text,
                                                      mechanism,
                                                      flags,
                                                      plaintext_length));
   // TODO(padolph): Use NSS PORT_GetError() and friends to report a more
   // accurate error, providing if doesn't leak any information to web pages
   // about other web crypto users, key details, etc.
   if (!new_key)
     return Status::Error();
 
-// TODO(padolph): Change to "defined(USE_NSS)" once the NSS fix for
-// https://bugzilla.mozilla.org/show_bug.cgi?id=981170 rolls into chromium.
-#if 1
-  // ------- Start NSS bug workaround
-  // Workaround for https://code.google.com/p/chromium/issues/detail?id=349939
-  // If unwrap fails, NSS nevertheless returns a valid-looking PK11SymKey, with
-  // a reasonable length but with key data pointing to uninitialized memory.
-  // This workaround re-wraps the key and compares the result with the incoming
-  // data, and fails if there is a difference. This prevents returning a bad key
-  // to the caller.
-  const unsigned int output_length = wrapped_key_data.byte_length();
-  std::vector<unsigned char> buffer(output_length, 0);
-  SECItem wrapped_key_item = MakeSECItemForBuffer(CryptoData(buffer));
-  if (SECSuccess != PK11_WrapSymKey(CKM_NSS_AES_KEY_WRAP,
-                                    param_item.get(),
-                                    wrapping_key->key(),
-                                    new_key.get(),
-                                    &wrapped_key_item)) {
-    return Status::Error();
+#if defined(USE_NSS)
+  if (!NSS_VersionCheck("3.16")) {
+    // Workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=981170
+    // which was fixed in NSS 3.16.0.
+    // If unwrap fails, NSS nevertheless returns a valid-looking PK11SymKey,
+    // with a reasonable length but with key data pointing to uninitialized
+    // memory.
+    // This workaround re-wraps the key and compares the result with the

[wtc, 2014/03/25 00:03:25]

This workaround is quite heavyweight.

Since we know NSS calls PORT_SetError(SEC_ERROR_BAD_DATA) before returning
successfully, would it work to call PORT_SetError(0) before calling
PK11_WrapSymKey, and checks PORT_GetError() == SEC_ERROR_BAD_DATA if
PK11_WrapSymKey returns SECSuccess?

[eroman, 2014/03/25 00:18:25]

Excellent idea! Done.

Indeed it looks from https://hg.mozilla.org/projects/nss/rev/753bb69e543c that
should be sufficient.

Using your workaround I can now also remove the valgrind suppression.

+    // incoming data, and fails if there is a difference. This prevents
+    // returning a bad key to the caller.
+    const unsigned int output_length = wrapped_key_data.byte_length();
+    std::vector<unsigned char> buffer(output_length, 0);
+    SECItem wrapped_key_item = MakeSECItemForBuffer(CryptoData(buffer));
+    if (SECSuccess != PK11_WrapSymKey(CKM_NSS_AES_KEY_WRAP,
+                                      param_item.get(),
+                                      wrapping_key->key(),
+                                      new_key.get(),
+                                      &wrapped_key_item)) {
+      return Status::Error();
+    }
+    if (wrapped_key_item.len != wrapped_key_data.byte_length() ||
+        memcmp(wrapped_key_item.data,
+               wrapped_key_data.bytes(),
+               wrapped_key_item.len) != 0) {
+      return Status::Error();
+    }
   }
-  if (wrapped_key_item.len != wrapped_key_data.byte_length() ||
-      memcmp(wrapped_key_item.data,
-             wrapped_key_data.bytes(),
-             wrapped_key_item.len) != 0) {
-    return Status::Error();
-  }
-// ------- End NSS bug workaround
 #endif
 
   *unwrapped_key = new_key.Pass();
   return Status::Success();
 }
 
 }  // namespace
 
 Status ImportKeyRaw(const blink::WebCryptoAlgorithm& algorithm,
                     const CryptoData& key_data,
@@ skipping 764 matching lines @@
                                      key_algorithm,
                                      usage_mask);
   return Status::Success();
 }
 
 }  // namespace platform
 
 }  // namespace webcrypto
 
 }  // namespace content