src/src/pdkim/base64.c

   1 /*
   2  *  RFC 1521 base64 encoding/decoding
   3  *
   4  *  Copyright (C) 2006-2010, Brainspark B.V.
   5  *
   6  *  This file is part of PolarSSL (http://www.polarssl.org)
   7  *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
   8  *
   9  *  All rights reserved.
  10  *
  11  *  This program is free software; you can redistribute it and/or modify
  12  *  it under the terms of the GNU General Public License as published by
  13  *  the Free Software Foundation; either version 2 of the License, or
  14  *  (at your option) any later version.
  15  *
  16  *  This program is distributed in the hope that it will be useful,
  17  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  *  GNU General Public License for more details.
  20  *
  21  *  You should have received a copy of the GNU General Public License along
  22  *  with this program; if not, write to the Free Software Foundation, Inc.,
  23  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  24  */
  25
  26 /* $Cambridge: exim/src/src/pdkim/base64.c,v 1.3 2009/12/07 13:05:07 tom Exp $ */
  27
  28
  29 #include "base64.h"
  30
  31 static const unsigned char base64_enc_map[64] =
  32 {
  33     'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
  34     'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
  35     'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
  36     'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
  37     'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
  38     'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
  39     '8', '9', '+', '/'
  40 };
  41
  42 static const unsigned char base64_dec_map[128] =
  43 {
  44     127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
  45     127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
  46     127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
  47     127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
  48     127, 127, 127,  62, 127, 127, 127,  63,  52,  53,
  49      54,  55,  56,  57,  58,  59,  60,  61, 127, 127,
  50     127,  64, 127, 127, 127,   0,   1,   2,   3,   4,
  51       5,   6,   7,   8,   9,  10,  11,  12,  13,  14,
  52      15,  16,  17,  18,  19,  20,  21,  22,  23,  24,
  53      25, 127, 127, 127, 127, 127, 127,  26,  27,  28,
  54      29,  30,  31,  32,  33,  34,  35,  36,  37,  38,
  55      39,  40,  41,  42,  43,  44,  45,  46,  47,  48,
  56      49,  50,  51, 127, 127, 127, 127, 127
  57 };
  58
  59 /*
  60  * Encode a buffer into base64 format
  61  */
  62 int base64_encode( unsigned char *dst, int *dlen,
  63                    const unsigned char *src, int  slen )
  64 {
  65     int i, n;
  66     int C1, C2, C3;
  67     unsigned char *p;
  68
  69     if( slen == 0 )
  70         return( 0 );
  71
  72     n = (slen << 3) / 6;
  73
  74     switch( (slen << 3) - (n * 6) )
  75     {
  76         case  2: n += 3; break;
  77         case  4: n += 2; break;
  78         default: break;
  79     }
  80
  81     if( *dlen < n + 1 )
  82     {
  83         *dlen = n + 1;
  84         return( POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL );
  85     }
  86
  87     n = (slen / 3) * 3;
  88
  89     for( i = 0, p = dst; i < n; i += 3 )
  90     {
  91         C1 = *src++;
  92         C2 = *src++;
  93         C3 = *src++;
  94
  95         *p++ = base64_enc_map[(C1 >> 2) & 0x3F];
  96         *p++ = base64_enc_map[(((C1 &  3) << 4) + (C2 >> 4)) & 0x3F];
  97         *p++ = base64_enc_map[(((C2 & 15) << 2) + (C3 >> 6)) & 0x3F];
  98         *p++ = base64_enc_map[C3 & 0x3F];
  99     }
 100
 101     if( i < slen )
 102     {
 103         C1 = *src++;
 104         C2 = ((i + 1) < slen) ? *src++ : 0;
 105
 106         *p++ = base64_enc_map[(C1 >> 2) & 0x3F];
 107         *p++ = base64_enc_map[(((C1 & 3) << 4) + (C2 >> 4)) & 0x3F];
 108
 109         if( (i + 1) < slen )
 110              *p++ = base64_enc_map[((C2 & 15) << 2) & 0x3F];
 111         else *p++ = '=';
 112
 113         *p++ = '=';
 114     }
 115
 116     *dlen = p - dst;
 117     *p = 0;
 118
 119     return( 0 );
 120 }
 121
 122 /*
 123  * Decode a base64-formatted buffer
 124  */
 125 int base64_decode( unsigned char *dst, int *dlen,
 126                    const unsigned char *src, int  slen )
 127 {
 128     int i, j, n;
 129     unsigned long x;
 130     unsigned char *p;
 131
 132     for( i = j = n = 0; i < slen; i++ )
 133     {
 134         if( ( slen - i ) >= 2 &&
 135             src[i] == '\r' && src[i + 1] == '\n' )
 136             continue;
 137
 138         if( src[i] == '\n' )
 139             continue;
 140
 141         if( src[i] == '=' && ++j > 2 )
 142             return( POLARSSL_ERR_BASE64_INVALID_CHARACTER );
 143
 144         if( src[i] > 127 || base64_dec_map[src[i]] == 127 )
 145             return( POLARSSL_ERR_BASE64_INVALID_CHARACTER );
 146
 147         if( base64_dec_map[src[i]] < 64 && j != 0 )
 148             return( POLARSSL_ERR_BASE64_INVALID_CHARACTER );
 149
 150         n++;
 151     }
 152
 153     if( n == 0 )
 154         return( 0 );
 155
 156     n = ((n * 6) + 7) >> 3;
 157
 158     if( *dlen < n )
 159     {
 160         *dlen = n;
 161         return( POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL );
 162     }
 163
 164    for( j = 3, n = x = 0, p = dst; i > 0; i--, src++ )
 165    {
 166         if( *src == '\r' || *src == '\n' )
 167             continue;
 168
 169         j -= ( base64_dec_map[*src] == 64 );
 170         x  = (x << 6) | ( base64_dec_map[*src] & 0x3F );
 171
 172         if( ++n == 4 )
 173         {
 174             n = 0;
 175             if( j > 0 ) *p++ = (unsigned char)( x >> 16 );
 176             if( j > 1 ) *p++ = (unsigned char)( x >>  8 );
 177             if( j > 2 ) *p++ = (unsigned char)( x       );
 178         }
 179     }
 180
 181     *dlen = p - dst;
 182
 183     return( 0 );
 184 }