Fix bug in history salt computation

chrome/common/visitedlink_common.cc

 // Copyright (c) 2006-2008 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 "chrome/common/visitedlink_common.h"
 
 #include <string.h>  // for memset()
 
 #include "base/logging.h"
 #include "base/md5.h"
@@ skipping 63 matching lines @@
 
 // static
 VisitedLinkCommon::Fingerprint VisitedLinkCommon::ComputeURLFingerprint(
     const char* canonical_url,
     size_t url_len,
     const uint8 salt[LINK_SALT_LENGTH]) {
   DCHECK(url_len > 0) << "Canonical URLs should not be empty";
 
   MD5Context ctx;
   MD5Init(&ctx);
-  MD5Update(&ctx, salt, sizeof(salt));
+
+  // This should really be
+  //    MD5Update(&ctx, salt, sizeof(salt) * LINK_SALT_LENGTH);
+  // but fixing this requires regenerating local databases. 4 bytes of salt
+  // should be enough for everyone.
+  MD5Update(&ctx, salt, sizeof(uint8*));

[brettw, 2011/05/25 22:39:01]

Hm, it sucks that this is different on 64 and 32 bit systems. This means the
file will be corrupted if you change bitedness, which isn't true for any other
file :(

Maybe we should just regenerate everybody's database file? I'm kind of depressed
about both of these options.

[Nico, 2011/05/25 22:41:56]

Tell me what you want (and if it's 2, a three-sentence summary on how to do
that), and I'll make it happen.

2 seems like the Right Thing, and that's usually better in the long run.

+
   MD5Update(&ctx, canonical_url, url_len * sizeof(char));
 
   MD5Digest digest;
   MD5Final(&digest, &ctx);
 
   // This is the same as "return *(Fingerprint*)&digest.a;" but if we do that
   // direct cast the alignment could be wrong, and we can't access a 64-bit int
   // on arbitrary alignment on some processors. This reinterpret_casts it
   // down to a char array of the same size as fingerprint, and then does the
   // bit cast, which amounts to a memcpy. This does not handle endian issues.
   return bit_cast<Fingerprint, uint8[8]>(
       *reinterpret_cast<uint8(*)[8]>(&digest.a));
 }