Base64 encoding and decoding with OpenSSL

Question

I\'ve been trying to figure out the openssl documentation for base64 decoding and encoding. I found some code snippets below

Answer 1

Rather than using the BIO_ interface it's much easier to use the EVP_ interface. For instance:

#include 
#include 
#include 

char *base64(const unsigned char *input, int length) {
  const auto pl = 4*((length+2)/3);
  auto output = reinterpret_cast(calloc(pl+1, 1)); //+1 for the terminating null that EVP_EncodeBlock adds on
  const auto ol = EVP_EncodeBlock(reinterpret_cast(output), input, length);
  if (pl != ol) { std::cerr << "Whoops, encode predicted " << pl << " but we got " << ol << "\n"; }
  return output;
}

unsigned char *decode64(const char *input, int length) {
  const auto pl = 3*length/4;
  auto output = reinterpret_cast(calloc(pl+1, 1));
  const auto ol = EVP_DecodeBlock(output, reinterpret_cast(input), length);
  if (pl != ol) { std::cerr << "Whoops, decode predicted " << pl << " but we got " << ol << "\n"; }
  return output;
}

The EVP functions include a streaming interface too, see the man page.