DCHECK that full hash must be 21 bytes or 32 bytes long.

components/safe_browsing_db/v4_store.cc

 // Copyright 2016 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 "base/base64.h"
 #include "base/bind.h"
 #include "base/files/file_util.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
@@ skipping 746 matching lines @@
   // Update |file_size_| now because we wrote the file correctly.
   file_size_ = static_cast<int64_t>(written);
 
   return WRITE_SUCCESS;
 }
 
 HashPrefix V4Store::GetMatchingHashPrefix(const FullHash& full_hash) {
   // It should never be the case that more than one hash prefixes match a given
   // full hash. However, if that happens, this method returns any one of them.
   // It does not guarantee which one of those will be returned.
-  DCHECK_EQ(32u, full_hash.size());
   for (const auto& pair : hash_prefix_map_) {

[Nathan Parker, 2017/01/04 18:58:46]

Why isn't this causing crashes all the time? Do we have tests that would hit
this?

One idea: Since we're only expecting 32 and 21 byte strings here, we could check
for those.  That'd prevent a new Check*() method from incorrectly passing the
wrong string here, I think.

[vakh (use Gerrit instead), 2017/01/10 03:47:56]

Because it is executed only for MatchMalwareIP and that wasn't getting executed
yet.
We have tests for MatchMalwareIP but they were replacing the V4Store with a fake
class so they never this this code. Added one in v4_store_unittest.cc now
Done.

     const PrefixSize& prefix_size = pair.first;
     const HashPrefixes& hash_prefixes = pair.second;
     HashPrefix hash_prefix = full_hash.substr(0, prefix_size);
     if (HashPrefixMatches(hash_prefix, hash_prefixes.begin(),
                           hash_prefixes.end())) {
       return hash_prefix;
     }
   }
   return HashPrefix();
 }
@@ skipping 82 matching lines @@
       base_metric + suffix, 1, 1000000, 50,
       base::HistogramBase::kUmaTargetedHistogramFlag);
   if (histogram) {
     const int64_t file_size_kilobytes = file_size_ / 1024;
     histogram->Add(file_size_kilobytes);
   }
   return file_size_;
 }
 
 }  // namespace safe_browsing