lib/base64.c

   1 /* base64.c     base64 encoding and decoding functions
   2  * Copyright (C) 2002  Simon Josefsson
   3  *
   4  * This file is part of Shishi.
   5  *
   6  * Shishi is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * Shishi is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with Shishi; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  *
  20  */
  21
  22 /*
  23  * This code is heavily modified from fetchmail (also GPL'd, of
  24  * course) by Brendan Cully <brendan@kublai.com>, via Mutt.
  25  *
  26  * Original copyright notice:
  27  *
  28  * The code in the fetchmail distribution is Copyright 1997 by Eric
  29  * S. Raymond.  Portions are also copyrighted by Carl Harris, 1993
  30  * and 1995.  Copyright retained for the purpose of protecting free
  31  * redistribution of source.
  32  *
  33  */
  34
  35 #include "internal.h"
  36
  37 static char B64Chars[64] = {
  38   'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
  39   'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
  40   'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
  41   't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
  42   '8', '9', '+', '/'
  43 };
  44
  45 #define BAD     -1
  46
  47 static const char base64val[] = {
  48   BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
  49   BAD,
  50   BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD,
  51   BAD,
  52   BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, 62, BAD, BAD, BAD,
  53   63,
  54   52, 53, 54, 55, 56, 57, 58, 59, 60, 61, BAD, BAD, BAD, BAD, BAD, BAD,
  55   BAD, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
  56   15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, BAD, BAD, BAD, BAD, BAD,
  57   BAD, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
  58   41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, BAD, BAD, BAD, BAD, BAD
  59 };
  60
  61 #define base64val(c) B64Chars[(unsigned int)(c)]
  62
  63 #define DECODE64(c)  (isascii(c) ? base64val[c] : BAD)
  64
  65 /* raw bytes to null-terminated base 64 string */
  66 void
  67 shishi_to_base64 (unsigned char *out, const unsigned char *in, int len,
  68                   int olen)
  69 {
  70   while (len >= 3 && olen > 10)
  71     {
  72       *out++ = B64Chars[in[0] >> 2];
  73       *out++ = B64Chars[((in[0] << 4) & 0x30) | (in[1] >> 4)];
  74       *out++ = B64Chars[((in[1] << 2) & 0x3c) | (in[2] >> 6)];
  75       *out++ = B64Chars[in[2] & 0x3f];
  76       olen -= 4;
  77       len -= 3;
  78       in += 3;
  79     }
  80
  81   /* clean up remainder */
  82   if (len > 0 && olen > 4)
  83     {
  84       unsigned char fragment;
  85
  86       *out++ = B64Chars[in[0] >> 2];
  87       fragment = (in[0] << 4) & 0x30;
  88       if (len > 1)
  89         fragment |= in[1] >> 4;
  90       *out++ = B64Chars[fragment];
  91       *out++ = (len < 2) ? '=' : B64Chars[(in[1] << 2) & 0x3c];
  92       *out++ = '=';
  93     }
  94   *out = '\0';
  95 }
  96
  97 /* Convert '\0'-terminated base 64 string to raw bytes.
  98  * Returns length of returned buffer, or -1 on error */
  99 int
 100 shishi_from_base64 (unsigned char *out, const unsigned char *in)
 101 {
 102   int len = 0;
 103   register unsigned char digit1, digit2, digit3, digit4;
 104
 105   do
 106     {
 107       digit1 = in[0];
 108       if (digit1 > 127 || DECODE64 (digit1) == BAD)
 109         return -1;
 110       digit2 = in[1];
 111       if (digit2 > 127 || DECODE64 (digit2) == BAD)
 112         return -1;
 113       digit3 = in[2];
 114       if (digit3 > 127 || ((digit3 != '=') && (DECODE64 (digit3) == BAD)))
 115         return -1;
 116       digit4 = in[3];
 117       if (digit4 > 127 || ((digit4 != '=') && (DECODE64 (digit4) == BAD)))
 118         return -1;
 119       in += 4;
 120
 121       /* digits are already sanity-checked */
 122       *out++ = (DECODE64 (digit1) << 2) | (DECODE64 (digit2) >> 4);
 123       len++;
 124       if (digit3 != '=')
 125         {
 126           *out++ =
 127             ((DECODE64 (digit2) << 4) & 0xf0) | (DECODE64 (digit3) >> 2);
 128           len++;
 129           if (digit4 != '=')
 130             {
 131               *out++ = ((DECODE64 (digit3) << 6) & 0xc0) | DECODE64 (digit4);
 132               len++;
 133             }
 134         }
 135     }
 136   while (*in && digit4 != '=');
 137
 138   return len;
 139 }