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// Copyright (c) 2012 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/basictypes.h"
#include "base/location.h"
#include "crypto/crypto_export.h"
namespace crypto {
// Provides a buffer of at least MIN_SIZE bytes, for use when calling OpenSSL's
// SHA256, HMAC, etc functions, adapting the buffer sizing rules to meet those
// of the our base wrapper APIs.
// This allows the library to write directly to the caller's buffer if it is of
// sufficient size, but if not it will write to temporary |min_sized_buffer_|
// of required size and then its content is automatically copied out on
// destruction, with truncation as appropriate.
template<int MIN_SIZE>
class ScopedOpenSSLSafeSizeBuffer {
ScopedOpenSSLSafeSizeBuffer(unsigned char* output, size_t output_len)
: output_(output),
output_len_(output_len) {
~ScopedOpenSSLSafeSizeBuffer() {
if (output_len_ < MIN_SIZE) {
// Copy the temporary buffer out, truncating as needed.
memcpy(output_, min_sized_buffer_, output_len_);
// else... any writing already happened directly into |output_|.
unsigned char* safe_buffer() {
return output_len_ < MIN_SIZE ? min_sized_buffer_ : output_;
// Pointer to the caller's data area and its associated size, where data
// written via safe_buffer() will [eventually] end up.
unsigned char* output_;
size_t output_len_;
// Temporary buffer writen into in the case where the caller's
// buffer is not of sufficient size.
unsigned char min_sized_buffer_[MIN_SIZE];
// Initialize OpenSSL if it isn't already initialized. This must be called
// before any other OpenSSL functions though it is safe and cheap to call this
// multiple times.
// This function is thread-safe, and OpenSSL will only ever be initialized once.
// OpenSSL will be properly shut down on program exit.
void CRYPTO_EXPORT EnsureOpenSSLInit();
// Drains the OpenSSL ERR_get_error stack. On a debug build the error codes
// are send to VLOG(1), on a release build they are disregarded. In most
// cases you should pass FROM_HERE as the |location|.
const tracked_objects::Location& location);
// Place an instance of this class on the call stack to automatically clear
// the OpenSSL error stack on function exit.
class OpenSSLErrStackTracer {
// Pass FROM_HERE as |location|, to help track the source of OpenSSL error
// messages. Note any diagnostic emitted will be tagged with the location of
// the constructor call as it's not possible to trace a destructor's callsite.
explicit OpenSSLErrStackTracer(const tracked_objects::Location& location)
: location_(location) {
~OpenSSLErrStackTracer() {
const tracked_objects::Location location_;
} // namespace crypto