c++ - 使用 OpenSSL 进行 Base64 编码和解码

Question

我一直在尝试找出用于 base64 解码和编码的 openssl 文档。我在下面找到了一些代码片段

#include <openssl/sha.h>
#include <openssl/hmac.h>
#include <openssl/evp.h>
#include <openssl/bio.h>
#include <openssl/buffer.h>

char *base64(const unsigned char *input, int length)
{
  BIO *bmem, *b64;
  BUF_MEM *bptr;

  b64 = BIO_new(BIO_f_base64());
  bmem = BIO_new(BIO_s_mem());
  b64 = BIO_push(b64, bmem);
  BIO_write(b64, input, length);
  BIO_flush(b64);
  BIO_get_mem_ptr(b64, &bptr);

  char *buff = (char *)malloc(bptr->length);
  memcpy(buff, bptr->data, bptr->length-1);
  buff[bptr->length-1] = 0;

  BIO_free_all(b64);

  return buff;
}

char *decode64(unsigned char *input, int length)
{
  BIO *b64, *bmem;

  char *buffer = (char *)malloc(length);
  memset(buffer, 0, length);

  b64 = BIO_new(BIO_f_base64());
  bmem = BIO_new_mem_buf(input, length);
  bmem = BIO_push(b64, bmem);

  BIO_read(bmem, buffer, length);

  BIO_free_all(bmem);

  return buffer;
}

这似乎只适用于单行字符串，例如“开始”，当我引入带有换行符和空格等的复杂字符串时，它会严重失败。

它甚至不必是 openssl，一个简单的类或一组函数做同样的事情就可以了，解决方案的构建过程非常复杂，我试图避免进入那里进行多项更改。我选择 openssl 的唯一原因是该解决方案已经与库一起编译。

Answer 1

就个人而言，我发现 OpenSSL API 使用起来非常痛苦，我会避免使用它，除非避免使用它的成本非常高。我觉得它已成为加密世界的标准 API 非常令人沮丧。

我觉得无聊，我用 C++ 给你写了一篇。这个甚至应该处理可能导致安全问题的边缘情况，例如，编码一个导致整数溢出的字符串，因为它太大了。

我已经对其进行了一些单元测试，所以它应该可以工作。

#include <string>
#include <cassert>
#include <limits>
#include <stdexcept>
#include <cctype>

static const char b64_table[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static const char reverse_table[128] = {
   64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
   64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
   64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 62, 64, 64, 64, 63,
   52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 64, 64, 64, 64, 64, 64,
   64,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
   15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 64, 64, 64, 64, 64,
   64, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
   41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 64, 64, 64, 64, 64
};

::std::string base64_encode(const ::std::string &bindata)
{
   using ::std::string;
   using ::std::numeric_limits;

   if (bindata.size() > (numeric_limits<string::size_type>::max() / 4u) * 3u) {
      throw ::std::length_error("Converting too large a string to base64.");
   }

   const ::std::size_t binlen = bindata.size();
   // Use = signs so the end is properly padded.
   string retval((((binlen + 2) / 3) * 4), '=');
   ::std::size_t outpos = 0;
   int bits_collected = 0;
   unsigned int accumulator = 0;
   const string::const_iterator binend = bindata.end();

   for (string::const_iterator i = bindata.begin(); i != binend; ++i) {
      accumulator = (accumulator << 8) | (*i & 0xffu);
      bits_collected += 8;
      while (bits_collected >= 6) {
         bits_collected -= 6;
         retval[outpos++] = b64_table[(accumulator >> bits_collected) & 0x3fu];
      }
   }
   if (bits_collected > 0) { // Any trailing bits that are missing.
      assert(bits_collected < 6);
      accumulator <<= 6 - bits_collected;
      retval[outpos++] = b64_table[accumulator & 0x3fu];
   }
   assert(outpos >= (retval.size() - 2));
   assert(outpos <= retval.size());
   return retval;
}

::std::string base64_decode(const ::std::string &ascdata)
{
   using ::std::string;
   string retval;
   const string::const_iterator last = ascdata.end();
   int bits_collected = 0;
   unsigned int accumulator = 0;

   for (string::const_iterator i = ascdata.begin(); i != last; ++i) {
      const int c = *i;
      if (::std::isspace(c) || c == '=') {
         // Skip whitespace and padding. Be liberal in what you accept.
         continue;
      }
      if ((c > 127) || (c < 0) || (reverse_table[c] > 63)) {
         throw ::std::invalid_argument("This contains characters not legal in a base64 encoded string.");
      }
      accumulator = (accumulator << 6) | reverse_table[c];
      bits_collected += 6;
      if (bits_collected >= 8) {
         bits_collected -= 8;
         retval += static_cast<char>((accumulator >> bits_collected) & 0xffu);
      }
   }
   return retval;
}