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 only by
 186                          * linear whitespace, then we ignore the whitespace.
 187                          * We will roll back the buffer the number of whitespace
 188                          * characters we've seen since last encoded word.
 189                          */
 190                         if (between_encodings) {
 191                                 q -= whitespace;
 192                                 dstlen += whitespace;
 193                         }
 194
 195 #ifdef HAVE_ICONV
 196                         /*
 197                          * empty encoded text. This ensures that we don't
 198                          * malloc 0 bytes but skip on to the end
 199                          */
 200                         if (endofmime == startofmime && use_iconv) {
 201                                 use_iconv = 0;
 202                                 iconv_close(cd);
 203                         }
 204
 205                         if (use_iconv) {
 206                                 saveq = q;
 207                                 savedstlen = dstlen;
 208                                 q = convbuf = (char *) mh_xmalloc(endofmime - startofmime);
 209                         }
 210 /* ADDCHR2 is for adding characters when q is or might be convbuf:
 211  * in this case on buffer-full we want to run iconv before returning.
 212  * I apologise for the dreadful name.
 213  */
 214 # define ADDCHR2(C) do { *q++ = (C); dstlen--; if (!dstlen) goto iconvbuffull; } while (0)
 215 #else
 216 # define ADDCHR2(C) ADDCHR(C)
 217 #endif
 218
 219                         /* Now decode the text */
 220                         if (quoted_printable) {
 221                                 for (pp = startofmime; pp < endofmime; pp++) {
 222                                         if (*pp == '=') {
 223                                                 c = unqp (pp[1], pp[2]);
 224                                                 if (c == -1)
 225                                                         continue;
 226                                                 if (c != 0)
 227                                                         *q++ = c;
 228                                                 pp += 2;
 229                                         } else if (*pp == '_') {
 230                                                 ADDCHR2(' ');
 231                                         } else {
 232                                                 ADDCHR2(*pp);
 233                                         }
 234                                 }
 235                         } else {
 236                                 /* base64 */
 237                                 int c1, c2, c3, c4;
 238                                 c1 = c2 = c3 = c4 = -1;
 239
 240                                 pp = startofmime;
 241                                 while (pp < endofmime) {
 242                                         /* 6 + 2 bits */
 243                                         while ((pp < endofmime) &&
 244                                                    ((c1 = char64(*pp)) == -1)) {
 245                                                 pp++;
 246                                         }
 247                                         if (pp < endofmime) {
 248                                                 pp++;
 249                                         }
 250                                         while ((pp < endofmime) &&
 251                                                    ((c2 = char64(*pp)) == -1)) {
 252                                                 pp++;
 253                                         }
 254                                         if (pp < endofmime && c1 != -1 && c2 != -1) {
 255                                                 ADDCHR2((c1 << 2) | (c2 >> 4));
 256                                                 pp++;
 257                                         }
 258                                         /* 4 + 4 bits */
 259                                         while ((pp < endofmime) &&
 260                                                    ((c3 = char64(*pp)) == -1)) {
 261                                                 pp++;
 262                                         }
 263                                         if (pp < endofmime && c2 != -1 && c3 != -1) {
 264                                                 ADDCHR2(((c2 & 0xF) << 4) | (c3 >> 2));
 265                                                 pp++;
 266                                         }
 267                                         /* 2 + 6 bits */
 268                                         while ((pp < endofmime) &&
 269                                                    ((c4 = char64(*pp)) == -1)) {
 270                                                 pp++;
 271                                         }
 272                                         if (pp < endofmime && c3 != -1 && c4 != -1) {
 273                                                 ADDCHR2(((c3 & 0x3) << 6) | (c4));
 274                                                 pp++;
 275                                         }
 276                                 }
 277                         }
 278
 279 #ifdef HAVE_ICONV
 280                 iconvbuffull:
 281                         /* NB that the string at convbuf is not necessarily
 282                          * NUL terminated here:
 283                          * q points to the first byte after the valid part.
 284                          */
 285                         /* Convert to native character set */
 286                         if (use_iconv) {
 287                                 size_t inbytes = q - convbuf;
 288                                 ICONV_CONST char *start = convbuf;
 289
 290                                 while (inbytes) {
 291                                         if (iconv(cd, &start, &inbytes, &saveq, &savedstlen) ==
 292                                                 (size_t)-1) {
 293                                                 if (errno != EILSEQ)
 294                                                         break;
 295                                                 /* character couldn't be converted. we output a `?'
 296                                                  * and try to carry on which won't work if
 297                                                  * either encoding was stateful */
 298                                                 iconv (cd, 0, 0, &saveq, &savedstlen);
 299                                                 if (!savedstlen)
 300                                                         break;
 301                                                 *saveq++ = '?';
 302                                                 savedstlen--;
 303                                                 if (!savedstlen)
 304                                                         break;
 305                                                 /* skip to next input character */
 306                                                 if (fromutf8) {
 307                                                         for (start++;(start < q) && ((*start & 192) == 128);start++)
 308                                                                 inbytes--;
 309                                                 } else
 310                                                         start++, inbytes--;
 311                                                 if (start >= q)
 312                                                         break;
 313                                         }
 314                                 }
 315                                 q = saveq;
 316                                 /* Stop now if (1) we hit the end of the buffer trying to do
 317                                  * MIME decoding and have just iconv-converted a partial string
 318                                  * or (2) our iconv-conversion hit the end of the buffer.
 319                                  */
 320                                 if (!dstlen || !savedstlen)
 321                                         goto buffull;
 322                                 dstlen = savedstlen;
 323                                 free(convbuf);
 324                         }
 325 #endif
 326
 327                         /*
 328                          * Now that we are done decoding this particular
 329                          * encoded word, advance string to trailing '='.
 330                          */
 331                         p = endofmime + 1;
 332
 333                         encoding_found = 1;  /* we found (at least 1) encoded word */
 334                         between_encodings = 1;  /* we have just decoded something */
 335                         whitespace = 0;  /* re-initialize amount of whitespace */
 336                 }
 337         }
 338 #ifdef HAVE_ICONV
 339         if (use_iconv) iconv_close(cd);
 340 #endif
 341
 342         /* If an equals was pending at end of string, add it now. */
 343         if (equals_pending)
 344                 ADDCHR('=');
 345         *q = '\0';
 346
 347         return encoding_found;
 348
 349   buffull:
 350         /* q is currently just off the end of the buffer, so rewind to NUL terminate */
 351         q--;
 352         *q = '\0';
 353         return encoding_found;
 354 }