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 14 namespace 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. 23 template<int MIN_SIZE> 24 class ScopedOpenSSLSafeSizeBuffer { 25 public: ScopedOpenSSLSafeSizeBuffer(unsigned char * output,size_t output_len)26 ScopedOpenSSLSafeSizeBuffer(unsigned char* output, size_t output_len) 27 : output_(output), 28 output_len_(output_len) { 29 } 30 ~ScopedOpenSSLSafeSizeBuffer()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 safe_buffer()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. 61 CRYPTO_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|. 66 CRYPTO_EXPORT void ClearOpenSSLERRStack(const base::Location& location); 67 68 // Place an instance of this class on the call stack to automatically clear 69 // the OpenSSL error stack on function exit. 70 class OpenSSLErrStackTracer { 71 public: 72 // Pass FROM_HERE as |location|, to help track the source of OpenSSL error 73 // messages. Note any diagnostic emitted will be tagged with the location of 74 // the constructor call as it's not possible to trace a destructor's callsite. OpenSSLErrStackTracer(const base::Location & location)75 explicit OpenSSLErrStackTracer(const base::Location& location) 76 : location_(location) { 77 EnsureOpenSSLInit(); 78 } ~OpenSSLErrStackTracer()79 ~OpenSSLErrStackTracer() { 80 ClearOpenSSLERRStack(location_); 81 } 82 83 private: 84 const base::Location location_; 85 86 DISALLOW_IMPLICIT_CONSTRUCTORS(OpenSSLErrStackTracer); 87 }; 88 89 } // namespace crypto 90 91 #endif // CRYPTO_OPENSSL_UTIL_H_ 92