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 - 2016 */
   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               allocated 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   /* debug_printf("b64d: '%c'\n", x); */
 167
 168   if (x > 127 || (x = dec64table[x]) == 255) return -1;
 169
 170   while (isspace(y = *code++)) ;
 171   /* debug_printf("b64d: '%c'\n", y); */
 172   if (y == 0 || (y = dec64table[y]) == 255)
 173     return -1;
 174
 175   *result++ = (x << 2) | (y >> 4);
 176   /* debug_printf("b64d:      -> %02x\n", result[-1]); */
 177
 178   while (isspace(x = *code++)) ;
 179   /* debug_printf("b64d: '%c'\n", x); */
 180   if (x == '=')         /* endmarker, but there should be another */
 181     {
 182     while (isspace(x = *code++)) ;
 183     /* debug_printf("b64d: '%c'\n", x); */
 184     if (x != '=') return -1;
 185     while (isspace(y = *code++)) ;
 186     if (y != 0) return -1;
 187     /* debug_printf("b64d: DONE\n"); */
 188     break;
 189     }
 190   else
 191     {
 192     if (x > 127 || (x = dec64table[x]) == 255) return -1;
 193     *result++ = (y << 4) | (x >> 2);
 194     /* debug_printf("b64d:      -> %02x\n", result[-1]); */
 195
 196     while (isspace(y = *code++)) ;
 197     /* debug_printf("b64d: '%c'\n", y); */
 198     if (y == '=')
 199       {
 200       while (isspace(y = *code++)) ;
 201       if (y != 0) return -1;
 202       /* debug_printf("b64d: DONE\n"); */
 203       break;
 204       }
 205     else
 206       {
 207       if (y > 127 || (y = dec64table[y]) == 255) return -1;
 208       *result++ = (x << 6) | y;
 209       /* debug_printf("b64d:      -> %02x\n", result[-1]); */
 210       }
 211     }
 212   }
 213
 214 *result = 0;
 215 return result - *ptr;
 216 }
 217
 218
 219 /*************************************************
 220 *          Encode byte-string in base 64         *
 221 *************************************************/
 222
 223 /* This function encodes a string of bytes, containing any values whatsoever,
 224 in base 64 as defined in RFC 2045 (MIME) and required by the SMTP AUTH
 225 extension (RFC 2554). The encoding algorithm is written out in a
 226 straightforward way. Turning it into some kind of compact loop is messy and
 227 would probably run more slowly.
 228
 229 Arguments:
 230   clear       points to the clear text bytes
 231   len         the number of bytes to encode
 232
 233 Returns:      a pointer to the zero-terminated base 64 string, which
 234               is in working store
 235 */
 236
 237 static uschar *enc64table =
 238   US"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 239
 240 uschar *
 241 b64encode(uschar *clear, int len)
 242 {
 243 uschar *code = store_get(4*((len+2)/3) + 1);
 244 uschar *p = code;
 245
 246 while (len-- >0)
 247   {
 248   register int x, y;
 249
 250   x = *clear++;
 251   *p++ = enc64table[(x >> 2) & 63];
 252
 253   if (len-- <= 0)
 254     {
 255     *p++ = enc64table[(x << 4) & 63];
 256     *p++ = '=';
 257     *p++ = '=';
 258     break;
 259     }
 260
 261   y = *clear++;
 262   *p++ = enc64table[((x << 4) | ((y >> 4) & 15)) & 63];
 263
 264   if (len-- <= 0)
 265     {
 266     *p++ = enc64table[(y << 2) & 63];
 267     *p++ = '=';
 268     break;
 269     }
 270
 271   x = *clear++;
 272   *p++ = enc64table[((y << 2) | ((x >> 6) & 3)) & 63];
 273
 274   *p++ = enc64table[x & 63];
 275   }
 276
 277 *p = 0;
 278
 279 return code;
 280 }
 281
 282
 283 /* End of base64.c */
 284 /* vi: sw ai sw=2
 285 */