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 - 2018 */
   9 /* Copyright (c) The Exim Maintainers 2020 */
  10 /* See the file NOTICE for conditions of use and distribution. */
  11
  12
  13 #include "exim.h"
  14 #ifdef WITH_CONTENT_SCAN        /* file-IO specific decode function */
  15 # include "mime.h"
  16
  17 /* BASE64 decoder matrix */
  18 static unsigned char mime_b64[256]={
  19 /*   0 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  20 /*  16 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  21 /*  32 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,   62,  128,  128,  128,   63,
  22 /*  48 */   52,   53,   54,   55,   56,   57,   58,   59,   60,   61,  128,  128,  128,  255,  128,  128,
  23 /*  64 */  128,    0,    1,    2,    3,    4,    5,    6,    7,    8,    9,   10,   11,   12,   13,   14,
  24 /*  80 */   15,   16,   17,   18,   19,   20,   21,   22,   23,   24,   25,  128,  128,  128,  128,  128,
  25 /*  96 */  128,   26,   27,   28,   29,   30,   31,   32,   33,   34,   35,   36,   37,   38,   39,   40,
  26 /* 112 */   41,   42,   43,   44,   45,   46,   47,   48,   49,   50,   51,  128,  128,  128,  128,  128,
  27 /* 128 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  28 /* 144 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  29 /* 160 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  30 /* 176 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  31 /* 192 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  32 /* 208 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  33 /* 224 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,
  34 /* 240 */  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128,  128
  35 };
  36
  37 /* decode base64 MIME part */
  38 ssize_t
  39 mime_decode_base64(FILE * in, FILE * out, uschar * boundary)
  40 {
  41 uschar ibuf[MIME_MAX_LINE_LENGTH], obuf[MIME_MAX_LINE_LENGTH];
  42 uschar *opos;
  43 ssize_t len, size = 0;
  44 int bytestate = 0;
  45
  46 opos = obuf;
  47
  48 while (Ufgets(ibuf, MIME_MAX_LINE_LENGTH, in) != NULL)
  49   {
  50   if (boundary != NULL
  51      && Ustrncmp(ibuf, "--", 2) == 0
  52      && Ustrncmp((ibuf+2), boundary, Ustrlen(boundary)) == 0
  53      )
  54     break;
  55
  56   for (uschar * ipos = ibuf ; *ipos != '\r' && *ipos != '\n' && *ipos; ++ipos)
  57     if (*ipos == '=')                   /* skip padding */
  58       ++bytestate;
  59
  60     else if (mime_b64[*ipos] == 128)    /* skip bad characters */
  61       mime_set_anomaly(MIME_ANOMALY_BROKEN_BASE64);
  62
  63     /* simple state-machine */
  64     else switch((bytestate++) & 3)
  65       {
  66       case 0:
  67         *opos = mime_b64[*ipos] << 2; break;
  68       case 1:
  69         *opos++ |= mime_b64[*ipos] >> 4;
  70         *opos = mime_b64[*ipos] << 4; break;
  71       case 2:
  72         *opos++ |= mime_b64[*ipos] >> 2;
  73         *opos = mime_b64[*ipos] << 6; break;
  74       case 3:
  75         *opos++ |= mime_b64[*ipos]; break;
  76       }
  77
  78   /* something to write? */
  79   len = opos - obuf;
  80   if (len > 0)
  81     {
  82     if (fwrite(obuf, 1, len, out) != len) return -1; /* error */
  83     size += len;
  84     /* copy incomplete last byte to start of obuf, where we continue */
  85     if ((bytestate & 3) != 0)
  86       *obuf = *opos;
  87     opos = obuf;
  88     }
  89   } /* while */
  90
  91 /* write out last byte if it was incomplete */
  92 if (bytestate & 3)
  93   {
  94   if (fwrite(obuf, 1, 1, out) != 1) return -1;
  95   ++size;
  96   }
  97
  98 return size;
  99 }
 100
 101 #endif  /*WITH_CONTENT_SCAN*/
 102
 103 /*************************************************
 104  *************************************************
 105  *************************************************
 106  *************************************************
 107  *************************************************
 108  *************************************************
 109  *************************************************
 110  *************************************************
 111  *************************************************
 112  *************************************************
 113  *************************************************
 114  *************************************************
 115  *************************************************
 116  *************************************************
 117  *************************************************
 118  *************************************************/
 119
 120
 121 /*************************************************
 122 *          Decode byte-string in base 64         *
 123 *************************************************/
 124
 125 /* This function decodes a string in base 64 format as defined in RFC 2045
 126 (MIME) and required by the SMTP AUTH extension (RFC 2554). The decoding
 127 algorithm is written out in a straightforward way. Turning it into some kind of
 128 compact loop is messy and would probably run more slowly.
 129
 130 Arguments:
 131   code        points to the coded string, zero-terminated
 132   ptr         where to put the pointer to the result, which is in
 133               allocated store, and zero-terminated
 134
 135 Returns:      the number of bytes in the result,
 136               or -1 if the input was malformed
 137
 138 Whitespace in the input is ignored.
 139 A zero is added on to the end to make it easy in cases where the result is to
 140 be interpreted as text. This is not included in the count. */
 141
 142 static uschar dec64table[] = {
 143   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /*  0-15 */
 144   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 16-31 */
 145   255,255,255,255,255,255,255,255,255,255,255, 62,255,255,255, 63, /* 32-47 */
 146    52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255,255,255,255, /* 48-63 */
 147   255,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, /* 64-79 */
 148    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,255,255,255,255,255, /* 80-95 */
 149   255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, /* 96-111 */
 150    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,255,255,255,255,255  /* 112-127*/
 151 };
 152
 153 int
 154 b64decode(const uschar *code, uschar **ptr)
 155 {
 156
 157 int x, y;
 158 uschar *result;
 159
 160 {
 161   int l = Ustrlen(code);
 162   *ptr = result = store_get(1 + l/4 * 3 + l%4, is_tainted(code));
 163 }
 164
 165 /* Each cycle of the loop handles a quantum of 4 input bytes. For the last
 166 quantum this may decode to 1, 2, or 3 output bytes. */
 167
 168 while ((x = *code++) != 0)
 169   {
 170   if (isspace(x)) continue;
 171   /* debug_printf("b64d: '%c'\n", x); */
 172
 173   if (x > 127 || (x = dec64table[x]) == 255) return -1;
 174
 175   while (isspace(y = *code++)) ;
 176   /* debug_printf("b64d: '%c'\n", y); */
 177   if (y > 127 || (y = dec64table[y]) == 255)
 178     return -1;
 179
 180   *result++ = (x << 2) | (y >> 4);
 181   /* debug_printf("b64d:      -> %02x\n", result[-1]); */
 182
 183   while (isspace(x = *code++)) ;
 184   /* debug_printf("b64d: '%c'\n", x); */
 185   if (x == '=')         /* endmarker, but there should be another */
 186     {
 187     while (isspace(x = *code++)) ;
 188     /* debug_printf("b64d: '%c'\n", x); */
 189     if (x != '=') return -1;
 190     while (isspace(y = *code++)) ;
 191     if (y != 0) return -1;
 192     /* debug_printf("b64d: DONE\n"); */
 193     break;
 194     }
 195   else
 196     {
 197     if (x > 127 || (x = dec64table[x]) == 255) return -1;
 198     *result++ = (y << 4) | (x >> 2);
 199     /* debug_printf("b64d:      -> %02x\n", result[-1]); */
 200
 201     while (isspace(y = *code++)) ;
 202     /* debug_printf("b64d: '%c'\n", y); */
 203     if (y == '=')
 204       {
 205       while (isspace(y = *code++)) ;
 206       if (y != 0) return -1;
 207       /* debug_printf("b64d: DONE\n"); */
 208       break;
 209       }
 210     else
 211       {
 212       if (y > 127 || (y = dec64table[y]) == 255) return -1;
 213       *result++ = (x << 6) | y;
 214       /* debug_printf("b64d:      -> %02x\n", result[-1]); */
 215       }
 216     }
 217   }
 218
 219 *result = 0;
 220 return result - *ptr;
 221 }
 222
 223
 224 /*************************************************
 225 *          Encode byte-string in base 64         *
 226 *************************************************/
 227
 228 /* This function encodes a string of bytes, containing any values whatsoever,
 229 in base 64 as defined in RFC 2045 (MIME) and required by the SMTP AUTH
 230 extension (RFC 2554). The encoding algorithm is written out in a
 231 straightforward way. Turning it into some kind of compact loop is messy and
 232 would probably run more slowly.
 233
 234 Arguments:
 235   clear       points to the clear text bytes
 236   len         the number of bytes to encode
 237
 238 Returns:      a pointer to the zero-terminated base 64 string, which
 239               is in working store
 240 */
 241
 242 static uschar *enc64table =
 243   US"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 244
 245 uschar *
 246 b64encode_taint(const uschar * clear, int len, BOOL tainted)
 247 {
 248 uschar *code = store_get(4*((len+2)/3) + 1, tainted);
 249 uschar *p = code;
 250
 251 while (len-- >0)
 252   {
 253   int x, y;
 254
 255   x = *clear++;
 256   *p++ = enc64table[(x >> 2) & 63];
 257
 258   if (len-- <= 0)
 259     {
 260     *p++ = enc64table[(x << 4) & 63];
 261     *p++ = '=';
 262     *p++ = '=';
 263     break;
 264     }
 265
 266   y = *clear++;
 267   *p++ = enc64table[((x << 4) | ((y >> 4) & 15)) & 63];
 268
 269   if (len-- <= 0)
 270     {
 271     *p++ = enc64table[(y << 2) & 63];
 272     *p++ = '=';
 273     break;
 274     }
 275
 276   x = *clear++;
 277   *p++ = enc64table[((y << 2) | ((x >> 6) & 3)) & 63];
 278
 279   *p++ = enc64table[x & 63];
 280   }
 281
 282 *p = 0;
 283
 284 return code;
 285 }
 286
 287 uschar *
 288 b64encode(const uschar * clear, int len)
 289 {
 290 return b64encode_taint(clear, len, is_tainted(clear));
 291 }
 292
 293
 294 /* End of base64.c */
 295 /* vi: sw ai sw=2
 296 */