src/src/pdkim/base64.c

   1 /*
   2  *  RFC 1521 base64 encoding/decoding
   3  *
   4  *  Based on XySSL: Copyright (C) 2006-2008  Christophe Devine
   5  *
   6  *  Copyright (C) 2009  Paul Bakker <polarssl_maintainer at polarssl dot org>
   7  *
   8  *  This program is free software; you can redistribute it and/or modify
   9  *  it under the terms of the GNU General Public License as published by
  10  *  the Free Software Foundation; either version 2 of the License, or
  11  *  (at your option) any later version.
  12  *
  13  *  This program is distributed in the hope that it will be useful,
  14  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  *  GNU General Public License for more details.
  17  *
  18  *  You should have received a copy of the GNU General Public License along
  19  *  with this program; if not, write to the Free Software Foundation, Inc.,
  20  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21  */
  22
  23 /* $Cambridge: exim/src/src/pdkim/base64.c,v 1.2 2009/06/10 07:34:05 tom Exp $ */
  24
  25 #include "base64.h"
  26
  27 static const unsigned char base64_enc_map[64] =
  28 {
  29     'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
  30     'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
  31     'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
  32     'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
  33     'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
  34     'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
  35     '8', '9', '+', '/'
  36 };
  37
  38 static const unsigned char base64_dec_map[128] =
  39 {
  40     127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
  41     127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
  42     127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
  43     127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
  44     127, 127, 127,  62, 127, 127, 127,  63,  52,  53,
  45      54,  55,  56,  57,  58,  59,  60,  61, 127, 127,
  46     127,  64, 127, 127, 127,   0,   1,   2,   3,   4,
  47       5,   6,   7,   8,   9,  10,  11,  12,  13,  14,
  48      15,  16,  17,  18,  19,  20,  21,  22,  23,  24,
  49      25, 127, 127, 127, 127, 127, 127,  26,  27,  28,
  50      29,  30,  31,  32,  33,  34,  35,  36,  37,  38,
  51      39,  40,  41,  42,  43,  44,  45,  46,  47,  48,
  52      49,  50,  51, 127, 127, 127, 127, 127
  53 };
  54
  55 /*
  56  * Encode a buffer into base64 format
  57  */
  58 int base64_encode( unsigned char *dst, int *dlen,
  59                    unsigned char *src, int  slen )
  60 {
  61     int i, n;
  62     int C1, C2, C3;
  63     unsigned char *p;
  64
  65     if( slen == 0 )
  66         return( 0 );
  67
  68     n = (slen << 3) / 6;
  69
  70     switch( (slen << 3) - (n * 6) )
  71     {
  72         case  2: n += 3; break;
  73         case  4: n += 2; break;
  74         default: break;
  75     }
  76
  77     if( *dlen < n + 1 )
  78     {
  79         *dlen = n + 1;
  80         return( POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL );
  81     }
  82
  83     n = (slen / 3) * 3;
  84
  85     for( i = 0, p = dst; i < n; i += 3 )
  86     {
  87         C1 = *src++;
  88         C2 = *src++;
  89         C3 = *src++;
  90
  91         *p++ = base64_enc_map[(C1 >> 2) & 0x3F];
  92         *p++ = base64_enc_map[(((C1 &  3) << 4) + (C2 >> 4)) & 0x3F];
  93         *p++ = base64_enc_map[(((C2 & 15) << 2) + (C3 >> 6)) & 0x3F];
  94         *p++ = base64_enc_map[C3 & 0x3F];
  95     }
  96
  97     if( i < slen )
  98     {
  99         C1 = *src++;
 100         C2 = ((i + 1) < slen) ? *src++ : 0;
 101
 102         *p++ = base64_enc_map[(C1 >> 2) & 0x3F];
 103         *p++ = base64_enc_map[(((C1 & 3) << 4) + (C2 >> 4)) & 0x3F];
 104
 105         if( (i + 1) < slen )
 106              *p++ = base64_enc_map[((C2 & 15) << 2) & 0x3F];
 107         else *p++ = '=';
 108
 109         *p++ = '=';
 110     }
 111
 112     *dlen = p - dst;
 113     *p = 0;
 114
 115     return( 0 );
 116 }
 117
 118 /*
 119  * Decode a base64-formatted buffer
 120  */
 121 int base64_decode( unsigned char *dst, int *dlen,
 122                    unsigned char *src, int  slen )
 123 {
 124     int i, j, n;
 125     unsigned long x;
 126     unsigned char *p;
 127
 128     for( i = j = n = 0; i < slen; i++ )
 129     {
 130         if( ( slen - i ) >= 2 &&
 131             src[i] == '\r' && src[i + 1] == '\n' )
 132             continue;
 133
 134         if( src[i] == '\n' )
 135             continue;
 136
 137         if( src[i] == '=' && ++j > 2 )
 138             return( POLARSSL_ERR_BASE64_INVALID_CHARACTER );
 139
 140         if( src[i] > 127 || base64_dec_map[src[i]] == 127 )
 141             return( POLARSSL_ERR_BASE64_INVALID_CHARACTER );
 142
 143         if( base64_dec_map[src[i]] < 64 && j != 0 )
 144             return( POLARSSL_ERR_BASE64_INVALID_CHARACTER );
 145
 146         n++;
 147     }
 148
 149     if( n == 0 )
 150         return( 0 );
 151
 152     n = ((n * 6) + 7) >> 3;
 153
 154     if( *dlen < n )
 155     {
 156         *dlen = n;
 157         return( POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL );
 158     }
 159
 160    for( j = 3, n = x = 0, p = dst; i > 0; i--, src++ )
 161    {
 162         if( *src == '\r' || *src == '\n' )
 163             continue;
 164
 165         j -= ( base64_dec_map[*src] == 64 );
 166         x  = (x << 6) | ( base64_dec_map[*src] & 0x3F );
 167
 168         if( ++n == 4 )
 169         {
 170             n = 0;
 171             if( j > 0 ) *p++ = (unsigned char)( x >> 16 );
 172             if( j > 1 ) *p++ = (unsigned char)( x >>  8 );
 173             if( j > 2 ) *p++ = (unsigned char)( x       );
 174         }
 175     }
 176
 177     *dlen = p - dst;
 178
 179     return( 0 );
 180 }