1// Copyright (c) 2012 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5#ifndef CRYPTO_OPENSSL_UTIL_H_ 6#define CRYPTO_OPENSSL_UTIL_H_ 7 8#include <stddef.h> 9 10#include "base/location.h" 11#include "base/macros.h" 12#include "crypto/crypto_export.h" 13 14namespace crypto { 15 16// Provides a buffer of at least MIN_SIZE bytes, for use when calling OpenSSL's 17// SHA256, HMAC, etc functions, adapting the buffer sizing rules to meet those 18// of our base wrapper APIs. 19// This allows the library to write directly to the caller's buffer if it is of 20// sufficient size, but if not it will write to temporary |min_sized_buffer_| 21// of required size and then its content is automatically copied out on 22// destruction, with truncation as appropriate. 23template<int MIN_SIZE> 24class ScopedOpenSSLSafeSizeBuffer { 25 public: 26 ScopedOpenSSLSafeSizeBuffer(unsigned char* output, size_t output_len) 27 : output_(output), 28 output_len_(output_len) { 29 } 30 31 ~ScopedOpenSSLSafeSizeBuffer() { 32 if (output_len_ < MIN_SIZE) { 33 // Copy the temporary buffer out, truncating as needed. 34 memcpy(output_, min_sized_buffer_, output_len_); 35 } 36 // else... any writing already happened directly into |output_|. 37 } 38 39 unsigned char* safe_buffer() { 40 return output_len_ < MIN_SIZE ? min_sized_buffer_ : output_; 41 } 42 43 private: 44 // Pointer to the caller's data area and its associated size, where data 45 // written via safe_buffer() will [eventually] end up. 46 unsigned char* output_; 47 size_t output_len_; 48 49 // Temporary buffer writen into in the case where the caller's 50 // buffer is not of sufficient size. 51 unsigned char min_sized_buffer_[MIN_SIZE]; 52 53 DISALLOW_COPY_AND_ASSIGN(ScopedOpenSSLSafeSizeBuffer); 54}; 55 56// Initialize OpenSSL if it isn't already initialized. This must be called 57// before any other OpenSSL functions though it is safe and cheap to call this 58// multiple times. 59// This function is thread-safe, and OpenSSL will only ever be initialized once. 60// OpenSSL will be properly shut down on program exit. 61CRYPTO_EXPORT void EnsureOpenSSLInit(); 62 63// Drains the OpenSSL ERR_get_error stack. On a debug build the error codes 64// are send to VLOG(1), on a release build they are disregarded. In most 65// cases you should pass FROM_HERE as the |location|. 66CRYPTO_EXPORT void ClearOpenSSLERRStack( 67 const tracked_objects::Location& location); 68 69// Place an instance of this class on the call stack to automatically clear 70// the OpenSSL error stack on function exit. 71class OpenSSLErrStackTracer { 72 public: 73 // Pass FROM_HERE as |location|, to help track the source of OpenSSL error 74 // messages. Note any diagnostic emitted will be tagged with the location of 75 // the constructor call as it's not possible to trace a destructor's callsite. 76 explicit OpenSSLErrStackTracer(const tracked_objects::Location& location) 77 : location_(location) { 78 EnsureOpenSSLInit(); 79 } 80 ~OpenSSLErrStackTracer() { 81 ClearOpenSSLERRStack(location_); 82 } 83 84 private: 85 const tracked_objects::Location location_; 86 87 DISALLOW_IMPLICIT_CONSTRUCTORS(OpenSSLErrStackTracer); 88}; 89 90} // namespace crypto 91 92#endif // CRYPTO_OPENSSL_UTIL_H_ 93