Certificate Transparency: Code for unpacking EV cert hashes whitelist

chrome/browser/net/packed_ct_ev_whitelist.h

+// 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.
+
+#ifndef CHROME_BROWSER_NET_PACKED_CT_EV_WHITELIST_H_
+#define CHROME_BROWSER_NET_PACKED_CT_EV_WHITELIST_H_
+
+#include <stdint.h>
+
+#include <string>
+#include <vector>
+
+#include "base/gtest_prod_util.h"
+#include "net/cert/ct_ev_whitelist.h"
+
+namespace base {
+class FilePath;
+}
+
+// An implementation of the EVCertsWhitelist that gets its data packed using
+// Golomb coding to encode the difference between subsequent hash values.
+// Format of the packed list:
+// * First 8 bytes: First hash
+// * Repeating Golomb-coded number which is the numeric difference of the
+//   previous hash value from this one
+//
+// The resulting, unpacked list is a sorted list of hash values that can be
+// efficiently searched.
+class PackedEVCertsWhitelist : public net::ct::EVCertsWhitelist {
+ public:
+  // Unpacks the given |compressed_whitelist|. See the class documentation
+  // for description of the |compressed_whitelist| format.
+  explicit PackedEVCertsWhitelist(const std::string& compressed_whitelist);
+
+  // Returns true if the |certificate_hash| appears in the EV certificate hashes
+  // whitelist. Must not be called if IsValid for this instance returned false.
+  bool ContainsCertificateHash(
+      const std::string& certificate_hash) const override;
+
+  // Returns true if the EV certificate hashes whitelist provided in the c'tor
+  // was valid, false otherwise.
+  bool IsValid() const override;
+
+ protected:
+  ~PackedEVCertsWhitelist() override;
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(PackedEVCertsWhitelistTest,
+                           UncompressFailsForTooShortList);
+  FRIEND_TEST_ALL_PREFIXES(PackedEVCertsWhitelistTest,
+                           UncompressFailsForTruncatedList);
+  FRIEND_TEST_ALL_PREFIXES(PackedEVCertsWhitelistTest,
+                           UncompressFailsForInvalidValuesInList);
+  FRIEND_TEST_ALL_PREFIXES(PackedEVCertsWhitelistTest,
+                           UncompressesWhitelistCorrectly);
+
+  // Given a Golomb-coded list of hashes in |compressed_whitelist|, unpack into
+  // |uncompressed_list|. Returns true if the format of the compressed whitelist
+  // is valid, false otherwise.
+  static bool UncompressEVWhitelist(const std::string& compressed_whitelist,
+                                    std::vector<uint64_t>* uncompressed_list);
+
+  bool is_whitelist_valid_;
+
+  // The whitelist is an array containing certificate hashes (truncated
+  // to a fixed size of 8 bytes), sorted.
+  // Binary search is used to locate hashes in the the array.
+  // Benchmarking bsearch vs std::set (with 120K entries, doing 1.2M lookups)
+  // shows that bsearch is about twice as fast as std::set lookups (and std::set
+  // has additional memory overhead).
+  std::vector<uint64_t> whitelist_;
+
+  DISALLOW_COPY_AND_ASSIGN(PackedEVCertsWhitelist);
+};
+
+// Sets the EV certificate hashes whitelist from |compressed_whitelist_file|
+// in |ssl_config_service|, after uncompressing it.
+// If the data in |compressed_whitelist_file| is not a valid compressed
+// whitelist, does nothing.
+// As this function performs file operations, it should be called from a
+// blocking pool worker or a file worker.
+// To set the new whitelist, this function dispatches a task to the IO thread.
+void SetEVWhitelistFromFile(const base::FilePath& compressed_whitelist_file);
+
+#endif  // CHROME_BROWSER_NET_PACKED_CT_EV_WHITELIST_H_