git.marmaro.de Git - mmh/blob - sbr/fmt_rfc2047.c

   1 /*
   2 ** fmt_rfc2047.c -- decode RFC-2047 header format
   3 **
   4 ** This code is Copyright (c) 2002, by the authors of nmh.  See the
   5 ** COPYRIGHT file in the root directory of the nmh distribution for
   6 ** complete copyright information.
   7 */
   8
   9 #include <h/mh.h>
  10 #include <h/utils.h>
  11 #ifdef HAVE_ICONV
  12 #  include <iconv.h>
  13 #  include <errno.h>
  14 #endif
  15
  16 static signed char hexindex[] = {
  17         -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  18         -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  19         -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  20          0, 1, 2, 3, 4, 5, 6, 7, 8, 9,-1,-1,-1,-1,-1,-1,
  21         -1,10,11,12,13,14,15,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  22         -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  23         -1,10,11,12,13,14,15,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  24         -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
  25 };
  26
  27 static signed char index_64[128] = {
  28         -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
  29         -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
  30         -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,62, -1,-1,-1,63,
  31         52,53,54,55, 56,57,58,59, 60,61,-1,-1, -1,-1,-1,-1,
  32         -1, 0, 1, 2,  3, 4, 5, 6,  7, 8, 9,10, 11,12,13,14,
  33         15,16,17,18, 19,20,21,22, 23,24,25,-1, -1,-1,-1,-1,
  34         -1,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
  35         41,42,43,44, 45,46,47,48, 49,50,51,-1, -1,-1,-1,-1
  36 };
  37
  38 #define char64(c) (((unsigned char) (c) > 127) ? -1 : index_64[(unsigned char) (c)])
  39
  40 static int
  41 unqp(unsigned char byte1, unsigned char byte2)
  42 {
  43         if (hexindex[byte1] == -1 || hexindex[byte2] == -1)
  44                 return -1;
  45         return (hexindex[byte1] << 4 | hexindex[byte2]);
  46 }
  47
  48 /* Check if character is linear whitespace */
  49 #define is_lws(c)  ((c) == ' ' || (c) == '\t' || (c) == '\n')
  50
  51
  52 /*
  53 ** Decode the string as a RFC-2047 header field
  54 */
  55
  56 /* Add character to the destination buffer, and bomb out if it fills up */
  57 #define ADDCHR(C) do { *q++ = (C); dstlen--; if (!dstlen) goto buffull; } while (0)
  58
  59 int
  60 decode_rfc2047(char *str, char *dst, size_t dstlen)
  61 {
  62         char *p, *q, *pp;
  63         char *startofmime, *endofmime;
  64         int c, quoted_printable;
  65         int encoding_found = 0;  /* did we decode anything? */
  66         int between_encodings = 0;  /* are we between two encodings? */
  67         int equals_pending = 0;  /* is there a '=' pending?  */
  68         int whitespace = 0;  /* how much whitespace between encodings? */
  69 #ifdef HAVE_ICONV
  70         int use_iconv = 0;  /* are we converting encoding with iconv? */
  71         iconv_t cd = NULL;
  72         int fromutf8 = 0;
  73         char *saveq, *convbuf = NULL;
  74         size_t savedstlen;
  75 #endif
  76
  77         if (!str)
  78                 return 0;
  79
  80         /*
  81         ** Do a quick and dirty check for the '=' character.
  82         ** This should quickly eliminate many cases.
  83         */
  84         if (!strchr(str, '='))
  85                 return 0;
  86
  87         for (p = str, q = dst; *p; p++) {
  88
  89                 /* reset iconv */
  90 #ifdef HAVE_ICONV
  91                 if (use_iconv) {
  92                         iconv_close(cd);
  93                         use_iconv = 0;
  94                 }
  95 #endif
  96                 /*
  97                 ** If we had an '=' character pending from
  98                 ** last iteration, then add it first.
  99                 */
 100                 if (equals_pending) {
 101                         ADDCHR('=');
 102                         equals_pending = 0;
 103                         between_encodings = 0;  /* we have added non-whitespace text */
 104                 }
 105
 106                 if (*p != '=') {
 107                         /* count linear whitespace while between encodings */
 108                         if (between_encodings && is_lws(*p))
 109                                 whitespace++;
 110                         else
 111                                 between_encodings = 0;  /* we have added non-whitespace text */
 112                         ADDCHR(*p);
 113                         continue;
 114                 }
 115
 116                 equals_pending = 1;  /* we have a '=' pending */
 117
 118                 /* Check for initial =? */
 119                 if (*p == '=' && p[1] && p[1] == '?' && p[2]) {
 120                         startofmime = p + 2;
 121
 122                         /* Scan ahead for the next '?' character */
 123                         for (pp = startofmime; *pp && *pp != '?'; pp++)
 124                                 ;
 125
 126                         if (!*pp)
 127                                 continue;
 128
 129                         /* Check if character set can be handled natively */
 130                         if (!check_charset(startofmime, pp - startofmime)) {
 131 #ifdef HAVE_ICONV
 132                                 /* .. it can't. We'll use iconv then. */
 133                                 *pp = '\0';
 134                                 cd = iconv_open(get_charset(), startofmime);
 135                                 fromutf8 = !mh_strcasecmp(startofmime, "UTF-8");
 136                                 *pp = '?';
 137                                 if (cd == (iconv_t)-1) continue;
 138                                 use_iconv = 1;
 139 #else
 140                                 continue;
 141 #endif
 142                         }
 143
 144                         startofmime = pp + 1;
 145
 146                         /* Check for valid encoding type */
 147                         if (*startofmime != 'B' && *startofmime != 'b' &&
 148                                 *startofmime != 'Q' && *startofmime != 'q')
 149                                 continue;
 150
 151                         /* Is encoding quoted printable or base64? */
 152                         quoted_printable = (*startofmime == 'Q' || *startofmime == 'q');
 153                         startofmime++;
 154
 155                         /* Check for next '?' character */
 156                         if (*startofmime != '?')
 157                                 continue;
 158                         startofmime++;
 159
 160                         /*
 161                         ** Scan ahead for the ending ?=
 162                         **
 163                         ** While doing this, we will also check if encoded
 164                         ** word has any embedded linear whitespace.
 165                         */
 166                         endofmime = NULL;
 167                         for (pp = startofmime; *pp && *(pp+1); pp++) {
 168                                 if (is_lws(*pp)) {
 169                                         break;
 170                                 } else if (*pp == '?' && pp[1] == '=') {
 171                                         endofmime = pp;
 172                                         break;
 173                                 }
 174                         }
 175                         if (is_lws(*pp) || endofmime == NULL)
 176                                 continue;
 177
 178                         /*
 179                         ** We've found an encoded word, so we can drop
 180                         ** the '=' that was pending
 181                         */
 182                         equals_pending = 0;
 183
 184                         /*
 185                         ** If we are between two encoded words separated
 186                         ** only by linear whitespace, then we ignore
 187                         ** the whitespace.  We will roll back the buffer
 188                         ** the number of whitespace characters we've seen
 189                         ** since last encoded word.
 190                         */
 191                         if (between_encodings) {
 192                                 q -= whitespace;
 193                                 dstlen += whitespace;
 194                         }
 195
 196 #ifdef HAVE_ICONV
 197                         /*
 198                         ** empty encoded text. This ensures that we don't
 199                         ** malloc 0 bytes but skip on to the end
 200                         */
 201                         if (endofmime == startofmime && use_iconv) {
 202                                 use_iconv = 0;
 203                                 iconv_close(cd);
 204                         }
 205
 206                         if (use_iconv) {
 207                                 saveq = q;
 208                                 savedstlen = dstlen;
 209                                 q = convbuf = (char *) mh_xmalloc(endofmime - startofmime);
 210                         }
 211 /*
 212 ** ADDCHR2 is for adding characters when q is or might be convbuf:
 213 ** in this case on buffer-full we want to run iconv before returning.
 214 ** I apologise for the dreadful name.
 215 */
 216 # define ADDCHR2(C) do { *q++ = (C); dstlen--; if (!dstlen) goto iconvbuffull; } while (0)
 217 #else
 218 # define ADDCHR2(C) ADDCHR(C)
 219 #endif
 220
 221                         /* Now decode the text */
 222                         if (quoted_printable) {
 223                                 for (pp = startofmime; pp < endofmime; pp++) {
 224                                         if (*pp == '=') {
 225                                                 c = unqp(pp[1], pp[2]);
 226                                                 if (c == -1)
 227                                                         continue;
 228                                                 if (c != 0)
 229                                                         *q++ = c;
 230                                                 pp += 2;
 231                                         } else if (*pp == '_') {
 232                                                 ADDCHR2(' ');
 233                                         } else {
 234                                                 ADDCHR2(*pp);
 235                                         }
 236                                 }
 237                         } else {
 238                                 /* base64 */
 239                                 int c1, c2, c3, c4;
 240                                 c1 = c2 = c3 = c4 = -1;
 241
 242                                 pp = startofmime;
 243                                 while (pp < endofmime) {
 244                                         /* 6 + 2 bits */
 245                                         while ((pp < endofmime) &&
 246                                                    ((c1 = char64(*pp)) == -1)) {
 247                                                 pp++;
 248                                         }
 249                                         if (pp < endofmime) {
 250                                                 pp++;
 251                                         }
 252                                         while ((pp < endofmime) &&
 253                                                    ((c2 = char64(*pp)) == -1)) {
 254                                                 pp++;
 255                                         }
 256                                         if (pp < endofmime && c1 != -1 && c2 != -1) {
 257                                                 ADDCHR2((c1 << 2) | (c2 >> 4));
 258                                                 pp++;
 259                                         }
 260                                         /* 4 + 4 bits */
 261                                         while ((pp < endofmime) &&
 262                                                    ((c3 = char64(*pp)) == -1)) {
 263                                                 pp++;
 264                                         }
 265                                         if (pp < endofmime && c2 != -1 && c3 != -1) {
 266                                                 ADDCHR2(((c2 & 0xF) << 4) | (c3 >> 2));
 267                                                 pp++;
 268                                         }
 269                                         /* 2 + 6 bits */
 270                                         while ((pp < endofmime) &&
 271                                                    ((c4 = char64(*pp)) == -1)) {
 272                                                 pp++;
 273                                         }
 274                                         if (pp < endofmime && c3 != -1 && c4 != -1) {
 275                                                 ADDCHR2(((c3 & 0x3) << 6) | (c4));
 276                                                 pp++;
 277                                         }
 278                                 }
 279                         }
 280
 281 #ifdef HAVE_ICONV
 282                 iconvbuffull:
 283                         /*
 284                         ** NB that the string at convbuf is not necessarily
 285                         ** NUL terminated here:
 286                         ** q points to the first byte after the valid part.
 287                         */
 288                         /* Convert to native character set */
 289                         if (use_iconv) {
 290                                 size_t inbytes = q - convbuf;
 291                                 ICONV_CONST char *start = convbuf;
 292
 293                                 while (inbytes) {
 294                                         if (iconv(cd, &start, &inbytes, &saveq, &savedstlen) ==
 295                                                 (size_t)-1) {
 296                                                 if (errno != EILSEQ)
 297                                                         break;
 298                                                 /*
 299                                                 ** character couldn't be
 300                                                 ** converted. we output a
 301                                                 ** `?'  and try to carry on
 302                                                 ** which won't work if either
 303                                                 ** encoding was stateful
 304                                                 */
 305                                                 iconv(cd, 0, 0, &saveq, &savedstlen);
 306                                                 if (!savedstlen)
 307                                                         break;
 308                                                 *saveq++ = '?';
 309                                                 savedstlen--;
 310                                                 if (!savedstlen)
 311                                                         break;
 312                                                 /* skip to next input character */
 313                                                 if (fromutf8) {
 314                                                         for (start++;(start < q) && ((*start & 192) == 128);start++)
 315                                                                 inbytes--;
 316                                                 } else
 317                                                         start++, inbytes--;
 318                                                 if (start >= q)
 319                                                         break;
 320                                         }
 321                                 }
 322                                 q = saveq;
 323                                 /*
 324                                 ** Stop now if (1) we hit the end of the
 325                                 ** buffer trying to do MIME decoding and
 326                                 ** have just iconv-converted a partial
 327                                 ** string or (2) our iconv-conversion hit
 328                                 ** the end of the buffer.
 329                                 */
 330                                 if (!dstlen || !savedstlen)
 331                                         goto buffull;
 332                                 dstlen = savedstlen;
 333                                 free(convbuf);
 334                         }
 335 #endif
 336
 337                         /*
 338                         ** Now that we are done decoding this particular
 339                         ** encoded word, advance string to trailing '='.
 340                         */
 341                         p = endofmime + 1;
 342
 343                         encoding_found = 1;  /* we found (at least 1) encoded word */
 344                         between_encodings = 1;  /* we have just decoded something */
 345                         whitespace = 0;  /* re-initialize amount of whitespace */
 346                 }
 347         }
 348 #ifdef HAVE_ICONV
 349         if (use_iconv) iconv_close(cd);
 350 #endif
 351
 352         /* If an equals was pending at end of string, add it now. */
 353         if (equals_pending)
 354                 ADDCHR('=');
 355         *q = '\0';
 356
 357         return encoding_found;
 358
 359   buffull:
 360         /*
 361         ** q is currently just off the end of the buffer,
 362         ** so rewind to NUL terminate
 363         */
 364         q--;
 365         *q = '\0';
 366         return encoding_found;
 367 }