src/src/base64.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) Tom Kistner <tom@duncanthrax.net> 2004, 2015 */
   6 /* License: GPL */
   7
   8 /* Copyright (c) University of Cambridge 1995 - 2015 */
   9 /* See the file NOTICE for conditions of use and distribution. */
  10
  11
  12 #include "exim.h"
  13 #ifdef WITH_CONTENT_SCAN        /* file-IO specific decode function */
  14 # include "mime.h"
  15
  16 /* BASE64 decoder matrix */
  17 static unsigned char mime_b64[256]={
  18 /*   0 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  19 /*  16 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  20 /*  32 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,   62,  128,  128,  128,   63,
  21 /*  48 */   52,   53,   54,   55,   56,   57,   58,   59,   60,   61,  128,  128,  128,  255,  128,  128,
  22 /*  64 */  128,    0,    1,    2,    3,    4,    5,    6,    7,    8,    9,   10,   11,   12,   13,   14,
  23 /*  80 */   15,   16,   17,   18,   19,   20,   21,   22,   23,   24,   25,  128,  128,  128,  128,  128,
  24 /*  96 */  128,   26,   27,   28,   29,   30,   31,   32,   33,   34,   35,   36,   37,   38,   39,   40,
  25 /* 112 */   41,   42,   43,   44,   45,   46,   47,   48,   49,   50,   51,  128,  128,  128,  128,  128,
  26 /* 128 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  27 /* 144 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  28 /* 160 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  29 /* 176 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  30 /* 192 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  31 /* 208 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  32 /* 224 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  33 /* 240 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128
  34 };
  35
  36 /* decode base64 MIME part */
  37 ssize_t
  38 mime_decode_base64(FILE * in, FILE * out, uschar * boundary)
  39 {
  40 uschar ibuf[MIME_MAX_LINE_LENGTH], obuf[MIME_MAX_LINE_LENGTH];
  41 uschar *ipos, *opos;
  42 ssize_t len, size = 0;
  43 int bytestate = 0;
  44
  45 opos = obuf;
  46
  47 while (Ufgets(ibuf, MIME_MAX_LINE_LENGTH, in) != NULL)
  48   {
  49   if (boundary != NULL
  50      && Ustrncmp(ibuf, "--", 2) == 0
  51      && Ustrncmp((ibuf+2), boundary, Ustrlen(boundary)) == 0
  52      )
  53     break;
  54
  55   for (ipos = ibuf ; *ipos != '\r' && *ipos != '\n' && *ipos != 0; ++ipos)
  56     if (*ipos == '=')                   /* skip padding */
  57       ++bytestate;
  58
  59     else if (mime_b64[*ipos] == 128)    /* skip bad characters */
  60       mime_set_anomaly(MIME_ANOMALY_BROKEN_BASE64);
  61
  62     /* simple state-machine */
  63     else switch((bytestate++) & 3)
  64       {
  65       case 0:
  66         *opos = mime_b64[*ipos] << 2; break;
  67       case 1:
  68         *opos++ |= mime_b64[*ipos] >> 4;
  69         *opos = mime_b64[*ipos] << 4; break;
  70       case 2:
  71         *opos++ |= mime_b64[*ipos] >> 2;
  72         *opos = mime_b64[*ipos] << 6; break;
  73       case 3:
  74         *opos++ |= mime_b64[*ipos]; break;
  75       }
  76
  77   /* something to write? */
  78   len = opos - obuf;
  79   if (len > 0)
  80     {
  81     if (fwrite(obuf, 1, len, out) != len) return -1; /* error */
  82     size += len;
  83     /* copy incomplete last byte to start of obuf, where we continue */
  84     if ((bytestate & 3) != 0)
  85       *obuf = *opos;
  86     opos = obuf;
  87     }
  88   } /* while */
  89
  90 /* write out last byte if it was incomplete */
  91 if (bytestate & 3)
  92   {
  93   if (fwrite(obuf, 1, 1, out) != 1) return -1;
  94   ++size;
  95   }
  96
  97 return size;
  98 }
  99
 100 #endif  /*WITH_CONTENT_SCAN*/
 101
 102 /*************************************************
 103 /*************************************************
 104 /*************************************************
 105 /*************************************************
 106 /*************************************************
 107 /*************************************************
 108 /*************************************************
 109 /*************************************************
 110 /*************************************************
 111 /*************************************************
 112 /*************************************************
 113 /*************************************************
 114 /*************************************************
 115 /*************************************************
 116 /*************************************************
 117 /*************************************************
 118
 119
 120 /*************************************************
 121 *          Decode byte-string in base 64         *
 122 *************************************************/
 123
 124 /* This function decodes a string in base 64 format as defined in RFC 2045
 125 (MIME) and required by the SMTP AUTH extension (RFC 2554). The decoding
 126 algorithm is written out in a straightforward way. Turning it into some kind of
 127 compact loop is messy and would probably run more slowly.
 128
 129 Arguments:
 130   code        points to the coded string, zero-terminated
 131   ptr         where to put the pointer to the result, which is in
 132               dynamic store, and zero-terminated
 133
 134 Returns:      the number of bytes in the result,
 135               or -1 if the input was malformed
 136
 137 Whitespace in the input is ignored.
 138 A zero is added on to the end to make it easy in cases where the result is to
 139 be interpreted as text. This is not included in the count. */
 140
 141 static uschar dec64table[] = {
 142   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /*  0-15 */
 143   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 16-31 */
 144   255,255,255,255,255,255,255,255,255,255,255, 62,255,255,255, 63, /* 32-47 */
 145    52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255,255,255,255, /* 48-63 */
 146   255,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, /* 64-79 */
 147    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,255,255,255,255,255, /* 80-95 */
 148   255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, /* 96-111 */
 149    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,255,255,255,255,255  /* 112-127*/
 150 };
 151
 152 int
 153 b64decode(uschar *code, uschar **ptr)
 154 {
 155 int x, y;
 156 uschar *result = store_get(3*(Ustrlen(code)/4) + 1);
 157
 158 *ptr = result;
 159
 160 /* Each cycle of the loop handles a quantum of 4 input bytes. For the last
 161 quantum this may decode to 1, 2, or 3 output bytes. */
 162
 163 while ((x = *code++) != 0)
 164   {
 165   if (isspace(x)) continue;
 166
 167   if (x > 127 || (x = dec64table[x]) == 255) return -1;
 168
 169   while (isspace(y = *code++)) ;
 170   if (y == 0 || (y = dec64table[y]) == 255)
 171     return -1;
 172
 173   *result++ = (x << 2) | (y >> 4);
 174
 175   while (isspace(x = *code++)) ;
 176   if (x == '=')
 177     {
 178     while (isspace(x = *code++)) ;
 179     if (x != '=' || *code != 0) return -1;
 180     }
 181   else
 182     {
 183     if (x > 127 || (x = dec64table[x]) == 255) return -1;
 184     *result++ = (y << 4) | (x >> 2);
 185
 186     while (isspace(y = *code++)) ;
 187     if (y == '=')
 188       {
 189       if (*code != 0) return -1;
 190       }
 191     else
 192       {
 193       if (y > 127 || (y = dec64table[y]) == 255) return -1;
 194       *result++ = (x << 6) | y;
 195       }
 196     }
 197   }
 198
 199 *result = 0;
 200 return result - *ptr;
 201 }
 202
 203
 204 /*************************************************
 205 /*************************************************
 206 /*************************************************
 207 /*************************************************
 208 /*************************************************
 209 /*************************************************
 210 /*************************************************
 211 /*************************************************
 212 /*************************************************
 213 /*************************************************
 214 /*************************************************
 215 /*************************************************
 216 /*************************************************
 217 /*************************************************
 218 /*************************************************
 219 /*************************************************
 220
 221 /*************************************************
 222 *          Encode byte-string in base 64         *
 223 *************************************************/
 224
 225 /* This function encodes a string of bytes, containing any values whatsoever,
 226 in base 64 as defined in RFC 2045 (MIME) and required by the SMTP AUTH
 227 extension (RFC 2554). The encoding algorithm is written out in a
 228 straightforward way. Turning it into some kind of compact loop is messy and
 229 would probably run more slowly.
 230
 231 Arguments:
 232   clear       points to the clear text bytes
 233   len         the number of bytes to encode
 234
 235 Returns:      a pointer to the zero-terminated base 64 string, which
 236               is in working store
 237 */
 238
 239 static uschar *enc64table =
 240   US"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 241
 242 uschar *
 243 b64encode(uschar *clear, int len)
 244 {
 245 uschar *code = store_get(4*((len+2)/3) + 1);
 246 uschar *p = code;
 247
 248 while (len-- >0)
 249   {
 250   register int x, y;
 251
 252   x = *clear++;
 253   *p++ = enc64table[(x >> 2) & 63];
 254
 255   if (len-- <= 0)
 256     {
 257     *p++ = enc64table[(x << 4) & 63];
 258     *p++ = '=';
 259     *p++ = '=';
 260     break;
 261     }
 262
 263   y = *clear++;
 264   *p++ = enc64table[((x << 4) | ((y >> 4) & 15)) & 63];
 265
 266   if (len-- <= 0)
 267     {
 268     *p++ = enc64table[(y << 2) & 63];
 269     *p++ = '=';
 270     break;
 271     }
 272
 273   x = *clear++;
 274   *p++ = enc64table[((y << 2) | ((x >> 6) & 3)) & 63];
 275
 276   *p++ = enc64table[x & 63];
 277   }
 278
 279 *p = 0;
 280
 281 return code;
 282 }
 283
 284
 285 /* End of base64.c */
 286 /* vi: sw ai sw=2
 287 */