Adds a VerifyAuditProof method to CTLogVerifier

net/cert/merkle_audit_proof.h

 // 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.
 
 #ifndef NET_CERT_MERKLE_AUDIT_PROOF_H_
 #define NET_CERT_MERKLE_AUDIT_PROOF_H_
 
 #include <stdint.h>
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "net/base/net_export.h"
 
 namespace net {
 namespace ct {
 
 // Returns the length of the audit path for a leaf at |leaf_index| in a Merkle
 // tree containing |tree_size| leaves.
 // The |leaf_index| must be less than the |tree_size|.
 NET_EXPORT uint64_t CalculateAuditPathLength(uint64_t leaf_index,
                                              uint64_t tree_size);
 
 // Audit proof for a Merkle tree leaf, as defined in section 2.1.1. of RFC6962.
 struct NET_EXPORT MerkleAuditProof {
   MerkleAuditProof();

[Ryan Sleevi, 2016/08/25 18:56:24]

FUTURE CL: Should we still have this ctor? Would it make more sense to remove
it, given that we want to ensure all parameters are sanely initialized?

[Rob Percival, 2016/10/03 17:39:26]

LogDnsClient currently makes use of it, as it populates the proof incrementally.
It wouldn't be unreasonable to use the other constructor for that case though,
and just pass in zeros and an empty vector.

   MerkleAuditProof(uint64_t leaf_index,
+                   uint64_t tree_size,
                    const std::vector<std::string>& audit_path);
   ~MerkleAuditProof();
 
   // Index of the tree leaf in the log.
   uint64_t leaf_index = 0;
 
+  // Number of leaves in the log's tree.
+  uint64_t tree_size = 0;
+
   // Audit path nodes.
   std::vector<std::string> nodes;
 };
 
 }  // namespace ct
 }  // namespace net
 
 #endif  // NET_CERT_MERKLE_AUDIT_PROOF_H_