/*

  ** Copyright (C) 2013-2019 Cisco Systems, Inc. and/or its affiliates. All rights reserved.

  ** Copyright (C) 1998-2013 Sourcefire, Inc.
  **
  ** Written by Patrick Mullen <pmullen@sourcefire.com>
  ** 9/11/2013 - Changed uint32_t to size_t
  **
  ** This program is free software; you can redistribute it and/or modify
  ** it under the terms of the GNU General Public License Version 2 as
  ** published by the Free Software Foundation.  You may not use, modify or
  ** distribute this program under any other version of the GNU General
  ** Public License.
  **
  ** This program is distributed in the hope that it will be useful,
  ** but WITHOUT ANY WARRANTY; without even the implied warranty of
  ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  ** GNU General Public License for more details.
  **
  ** You should have received a copy of the GNU General Public License
  ** along with this program; if not, write to the Free Software
  ** Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
 
 #ifdef HAVE_CONFIG_H
 #include "clamav-config.h"
 #endif
 
 #include "sf_base64decode.h"
 

 // clang-format off

 uint8_t sf_decode64tab[256] = {
         100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,
         100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,
         100,100,100,100,100,100,100,100,100,100,100,62 ,100,100,100, 63,
          52, 53, 54, 55, 56, 57, 58, 59, 60, 61,100,100,100, 99,100,100,
         100,  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, 25,100,100,100,100,100,
         100, 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, 51,100,100,100,100,100,
         100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,
         100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,
         100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,
         100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,
         100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,
         100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,
         100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,
         100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100};

 // clang-format on

 
 /* base64decode assumes the input data terminates with '=' and/or at the end of the input buffer
  * at inbuf_size.  If extra characters exist within inbuf before inbuf_size is reached, it will
  * happily decode what it can and skip over what it can't.  This is consistent with other decoders
  * out there.  So, either terminate the string, set inbuf_size correctly, or at least be sure the
  * data is valid up until the point you care about.  Note base64 data does NOT have to end with
  * '=' and won't if the number of bytes of input data is evenly divisible by 3.
 */
 int sf_base64decode(uint8_t *inbuf, size_t inbuf_size, uint8_t *outbuf, size_t outbuf_size, size_t *bytes_written)
 {

     uint8_t *cursor, *endofinbuf;
     uint8_t *outbuf_ptr;
     uint8_t base64data[4], *base64data_ptr; /* temporary holder for current base64 chunk */
     uint8_t tableval_a, tableval_b, tableval_c, tableval_d;

     size_t n;
     size_t max_base64_chars; /* The max number of decoded base64 chars that fit into outbuf */

     int error = 0;

     /* This algorithm will waste up to 4 bytes but we really don't care.

       At the end we're going to copy the exact number of bytes requested. */

     max_base64_chars = (outbuf_size / 3) * 4 + 4; /* 4 base64 bytes gives 3 data bytes, plus

                                                     an extra 4 to take care of any rounding */
 

     base64data_ptr = base64data;
     endofinbuf     = inbuf + inbuf_size;
 
     /* Strip non-base64 chars from inbuf and decode */
     n              = 0;
     *bytes_written = 0;
     cursor         = inbuf;
     outbuf_ptr     = outbuf;
     while ((cursor < endofinbuf) && (n < max_base64_chars)) {
         if (sf_decode64tab[*cursor] != 100) {
             *base64data_ptr++ = *cursor;
             n++; /* Number of base64 bytes we've stored */
             if (!(n % 4)) {
                 /* We have four databytes upon which to operate */
 
                 if ((base64data[0] == '=') || (base64data[1] == '=')) {
                     /* Error in input data */
                     error = 1;
                     break;
                 }
 
                 /* retrieve values from lookup table */
                 tableval_a = sf_decode64tab[base64data[0]];
                 tableval_b = sf_decode64tab[base64data[1]];
                 tableval_c = sf_decode64tab[base64data[2]];
                 tableval_d = sf_decode64tab[base64data[3]];
 
                 if (*bytes_written < outbuf_size) {
                     *outbuf_ptr++ = (tableval_a << 2) | (tableval_b >> 4);
                     (*bytes_written)++;
                 }
 
                 if ((base64data[2] != '=') && (*bytes_written < outbuf_size)) {
                     *outbuf_ptr++ = (tableval_b << 4) | (tableval_c >> 2);
                     (*bytes_written)++;
                 } else {
                     break;
                 }
 
                 if ((base64data[3] != '=') && (*bytes_written < outbuf_size)) {
                     *outbuf_ptr++ = (tableval_c << 6) | tableval_d;
                     (*bytes_written)++;
                 } else {
                     break;
                 }
 
                 /* Reset our decode pointer for the next group of four */
                 base64data_ptr = base64data;

             }

         }
         cursor++;
     }
 
     if (error)
         return (-1);
     else
         return (0);

 }