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// Copyright (c) 2009 The Chromium OS 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 <string>
#include <unistd.h>
#include <vector>
#include <openssl/sha.h>
#include <base/basictypes.h>
#include <base/logging.h>
// Omaha uses base64 encoded SHA-256 as the hash. This class provides a simple
// wrapper around OpenSSL providing such a formatted hash of data passed in.
// The methods of this class must be called in a very specific order: First the
// ctor (of course), then 0 or more calls to Update(), then Finalize(), then 0
// or more calls to hash().
namespace chromeos_update_engine {
class OmahaHashCalculator {
// Update is called with all of the data that should be hashed in order.
// Update will read |length| bytes of |data|.
// Returns true on success.
bool Update(const char* data, size_t length);
// Updates the hash with up to |length| bytes of data from |file|. If |length|
// is negative, reads in and updates with the whole file. Returns the number
// of bytes that the hash was updated with, or -1 on error.
off_t UpdateFile(const std::string& name, off_t length);
// Call Finalize() when all data has been passed in. This method tells
// OpenSSl that no more data will come in and base64 encodes the resulting
// hash.
// Returns true on success.
bool Finalize();
// Gets the hash. Finalize() must have been called.
const std::string& hash() const {
DCHECK(!hash_.empty()) << "Call Finalize() first";
return hash_;
const std::vector<char>& raw_hash() const {
DCHECK(!raw_hash_.empty()) << "Call Finalize() first";
return raw_hash_;
// Gets the current hash context. Note that the string will contain binary
// data (including \0 characters).
std::string GetContext() const;
// Sets the current hash context. |context| must the string returned by a
// previous OmahaHashCalculator::GetContext method call. Returns true on
// success, and false otherwise.
bool SetContext(const std::string& context);
static bool RawHashOfBytes(const char* data,
size_t length,
std::vector<char>* out_hash);
static bool RawHashOfData(const std::vector<char>& data,
std::vector<char>* out_hash);
static off_t RawHashOfFile(const std::string& name, off_t length,
std::vector<char>* out_hash);
// Used by tests
static std::string OmahaHashOfBytes(const void* data, size_t length);
static std::string OmahaHashOfString(const std::string& str);
static std::string OmahaHashOfData(const std::vector<char>& data);
static bool Base64Encode(const void* data, size_t size, std::string* out);
// If non-empty, the final base64 encoded hash and the raw hash. Will only be
// set to non-empty when Finalize is called.
std::string hash_;
std::vector<char> raw_hash_;
// Init success
bool valid_;
// The hash state used by OpenSSL
SHA256_CTX ctx_;
} // namespace chromeos_update_engine