base64.cpp

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/*
* Base64 Encoding and Decoding
* (C) 2010,2015 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/base64.h>
#include <botan/exceptn.h>
#include <botan/mem_ops.h>
#include <botan/internal/rounding.h>

namespace Botan {

namespace {

static const uint8_t BIN_TO_BASE64[64] = {
   'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
   'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
   'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
   'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
   '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
};

void do_base64_encode(char out[4], const uint8_t in[3])
   {
   out[0] = BIN_TO_BASE64[(in[0] & 0xFC) >> 2];
   out[1] = BIN_TO_BASE64[((in[0] & 0x03) << 4) | (in[1] >> 4)];
   out[2] = BIN_TO_BASE64[((in[1] & 0x0F) << 2) | (in[2] >> 6)];
   out[3] = BIN_TO_BASE64[in[2] & 0x3F];
   }

}

size_t base64_encode(char out[],
                     const uint8_t in[],
                     size_t input_length,
                     size_t& input_consumed,
                     bool final_inputs)
   {
   input_consumed = 0;

   size_t input_remaining = input_length;
   size_t output_produced = 0;

   while(input_remaining >= 3)
      {
      do_base64_encode(out + output_produced, in + input_consumed);

      input_consumed += 3;
      output_produced += 4;
      input_remaining -= 3;
      }

   if(final_inputs && input_remaining)
      {
      uint8_t remainder[3] = { 0 };
      for(size_t i = 0; i != input_remaining; ++i)
         remainder[i] = in[input_consumed + i];

      do_base64_encode(out + output_produced, remainder);

      size_t empty_bits = 8 * (3 - input_remaining);
      size_t index = output_produced + 4 - 1;
      while(empty_bits >= 8)
         {
         out[index--] = '=';
         empty_bits -= 6;
         }

      input_consumed += input_remaining;
      output_produced += 4;
      }

   return output_produced;
   }

std::string base64_encode(const uint8_t input[],
                          size_t input_length)
   {
   const size_t output_length = base64_encode_max_output(input_length);
   std::string output(output_length, 0);

   size_t consumed = 0;
   size_t produced = 0;
   
   if (output_length > 0)
   {
      produced = base64_encode(&output.front(),
                               input, input_length,
                               consumed, true);
   }

   BOTAN_ASSERT_EQUAL(consumed, input_length, "Consumed the entire input");
   BOTAN_ASSERT_EQUAL(produced, output.size(), "Produced expected size");

   return output;
   }

size_t base64_decode(uint8_t output[],
                     const char input[],
                     size_t input_length,
                     size_t& input_consumed,
                     bool final_inputs,
                     bool ignore_ws)
   {
   /*
   * Base64 Decoder Lookup Table
   * Warning: assumes ASCII encodings
   */
   static const uint8_t BASE64_TO_BIN[256] = {
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x80,
      0x80, 0xFF, 0xFF, 0x80, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0x80, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0x3E, 0xFF, 0xFF, 0xFF, 0x3F, 0x34, 0x35,
      0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0xFF, 0xFF,
      0xFF, 0x81, 0xFF, 0xFF, 0xFF, 0x00, 0x01, 0x02, 0x03, 0x04,
      0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E,
      0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
      0x19, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x1A, 0x1B, 0x1C,
      0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26,
      0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30,
      0x31, 0x32, 0x33, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

   uint8_t* out_ptr = output;
   uint8_t decode_buf[4];
   size_t decode_buf_pos = 0;
   size_t final_truncate = 0;

   clear_mem(output, input_length * 3 / 4);

   for(size_t i = 0; i != input_length; ++i)
      {
      const uint8_t bin = BASE64_TO_BIN[static_cast<uint8_t>(input[i])];

      if(bin <= 0x3F)
         {
         decode_buf[decode_buf_pos] = bin;
         decode_buf_pos += 1;
         }
      else if(!(bin == 0x81 || (bin == 0x80 && ignore_ws)))
         {
         std::string bad_char(1, input[i]);
         if(bad_char == "\t")
           bad_char = "\\t";
         else if(bad_char == "\n")
           bad_char = "\\n";
         else if(bad_char == "\r")
           bad_char = "\\r";

         throw Invalid_Argument(
           std::string("base64_decode: invalid base64 character '") +
           bad_char + "'");
         }

      /*
      * If we're at the end of the input, pad with 0s and truncate
      */
      if(final_inputs && (i == input_length - 1))
         {
         if(decode_buf_pos)
            {
            for(size_t j = decode_buf_pos; j != 4; ++j)
               decode_buf[j] = 0;
            final_truncate = (4 - decode_buf_pos);
            decode_buf_pos = 4;
            }
         }

      if(decode_buf_pos == 4)
         {
         out_ptr[0] = (decode_buf[0] << 2) | (decode_buf[1] >> 4);
         out_ptr[1] = (decode_buf[1] << 4) | (decode_buf[2] >> 2);
         out_ptr[2] = (decode_buf[2] << 6) | decode_buf[3];

         out_ptr += 3;
         decode_buf_pos = 0;
         input_consumed = i+1;
         }
      }

   while(input_consumed < input_length &&
         BASE64_TO_BIN[static_cast<uint8_t>(input[input_consumed])] == 0x80)
      {
      ++input_consumed;
      }

   size_t written = (out_ptr - output) - final_truncate;

   return written;
   }

size_t base64_decode(uint8_t output[],
                     const char input[],
                     size_t input_length,
                     bool ignore_ws)
   {
   size_t consumed = 0;
   size_t written = base64_decode(output, input, input_length,
                                  consumed, true, ignore_ws);

   if(consumed != input_length)
      throw Invalid_Argument("base64_decode: input did not have full bytes");

   return written;
   }

size_t base64_decode(uint8_t output[],
                     const std::string& input,
                     bool ignore_ws)
   {
   return base64_decode(output, input.data(), input.length(), ignore_ws);
   }

secure_vector<uint8_t> base64_decode(const char input[],
                                 size_t input_length,
                                 bool ignore_ws)
   {
   const size_t output_length = base64_decode_max_output(input_length);
   secure_vector<uint8_t> bin(output_length);

   size_t written = base64_decode(bin.data(),
                                  input,
                                  input_length,
                                  ignore_ws);

   bin.resize(written);
   return bin;
   }

secure_vector<uint8_t> base64_decode(const std::string& input,
                                 bool ignore_ws)
   {
   return base64_decode(input.data(), input.size(), ignore_ws);
   }

size_t base64_encode_max_output(size_t input_length)
   {
   return (round_up(input_length, 3) / 3) * 4;
   }

size_t base64_decode_max_output(size_t input_length)
   {
   return (round_up(input_length, 4) * 3) / 4;
   }

}