crypto/openssl_util.h

   1 // Copyright (c) 2011 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 #pragma once
   8
   9 #include "base/basictypes.h"
  10 #include "base/location.h"
  11 #include "crypto/crypto_export.h"
  12
  13 namespace crypto {
  14
  15 // A helper class that takes care of destroying OpenSSL objects when it goes out
  16 // of scope.
  17 template <typename T, void (*destructor)(T*)>
  18 class ScopedOpenSSL {
  19  public:
  20   ScopedOpenSSL() : ptr_(NULL) { }
  21   explicit ScopedOpenSSL(T* ptr) : ptr_(ptr) { }
  22   ~ScopedOpenSSL() {
  23     reset(NULL);
  24   }
  25
  26   T* get() const { return ptr_; }
  27   void reset(T* ptr) {
  28     if (ptr != ptr_) {
  29       if (ptr_) (*destructor)(ptr_);
  30       ptr_ = ptr;
  31     }
  32   }
  33
  34  private:
  35   T* ptr_;
  36
  37   DISALLOW_COPY_AND_ASSIGN(ScopedOpenSSL);
  38 };
  39
  40 // Provides a buffer of at least MIN_SIZE bytes, for use when calling OpenSSL's
  41 // SHA256, HMAC, etc functions, adapting the buffer sizing rules to meet those
  42 // of the our base wrapper APIs.
  43 // This allows the library to write directly to the caller's buffer if it is of
  44 // sufficient size, but if not it will write to temporary |min_sized_buffer_|
  45 // of required size and then its content is automatically copied out on
  46 // destruction, with truncation as appropriate.
  47 template<int MIN_SIZE>
  48 class ScopedOpenSSLSafeSizeBuffer {
  49  public:
  50   ScopedOpenSSLSafeSizeBuffer(unsigned char* output, size_t output_len)
  51       : output_(output),
  52         output_len_(output_len) {
  53   }
  54
  55   ~ScopedOpenSSLSafeSizeBuffer() {
  56     if (output_len_ < MIN_SIZE) {
  57       // Copy the temporary buffer out, truncating as needed.
  58       memcpy(output_, min_sized_buffer_, output_len_);
  59     }
  60     // else... any writing already happened directly into |output_|.
  61   }
  62
  63   unsigned char* safe_buffer() {
  64     return output_len_ < MIN_SIZE ? min_sized_buffer_ : output_;
  65   }
  66
  67  private:
  68   // Pointer to the caller's data area and it's associated size, where data
  69   // written via safe_buffer() will [eventually] end up.
  70   unsigned char* output_;
  71   size_t output_len_;
  72
  73   // Temporary buffer writen into in the case where the caller's
  74   // buffer is not of sufficient size.
  75   unsigned char min_sized_buffer_[MIN_SIZE];
  76
  77   DISALLOW_COPY_AND_ASSIGN(ScopedOpenSSLSafeSizeBuffer);
  78 };
  79
  80 // Initialize OpenSSL if it isn't already initialized. This must be called
  81 // before any other OpenSSL functions.
  82 // This function is thread-safe, and OpenSSL will only ever be initialized once.
  83 // OpenSSL will be properly shut down on program exit.
  84 void CRYPTO_EXPORT EnsureOpenSSLInit();
  85
  86 // Drains the OpenSSL ERR_get_error stack. On a debug build the error codes
  87 // are send to VLOG(1), on a release build they are disregarded. In most
  88 // cases you should pass FROM_HERE as the |location|.
  89 void ClearOpenSSLERRStack(const tracked_objects::Location& location);
  90
  91 // Place an instance of this class on the call stack to automatically clear
  92 // the OpenSSL error stack on function exit.
  93 class OpenSSLErrStackTracer {
  94  public:
  95   // Pass FROM_HERE as |location|, to help track the source of OpenSSL error
  96   // messages. Note any diagnostic emitted will be tagged with the location of
  97   // the constructor call as it's not possible to trace a destructor's callsite.
  98   explicit OpenSSLErrStackTracer(const tracked_objects::Location& location)
  99       : location_(location) {
 100     EnsureOpenSSLInit();
 101   }
 102   ~OpenSSLErrStackTracer() {
 103     ClearOpenSSLERRStack(location_);
 104   }
 105
 106  private:
 107   const tracked_objects::Location location_;
 108
 109   DISALLOW_IMPLICIT_CONSTRUCTORS(OpenSSLErrStackTracer);
 110 };
 111
 112 }  // namespace crypto
 113
 114 #endif  // CRYPTO_OPENSSL_UTIL_H_