diplodocus.org Git - nmh/blob - sbr/fmt_rfc2047.c

   1 /* fmt_rfc2047.c -- decode RFC-2047 header format
   2  *
   3  * This code is Copyright (c) 2002, by the authors of nmh.  See the
   4  * COPYRIGHT file in the root directory of the nmh distribution for
   5  * complete copyright information.
   6  */
   7
   8 #include <h/mh.h>
   9 #include <h/utils.h>
  10 #ifdef HAVE_ICONV
  11 #  include <iconv.h>
  12 #endif
  13
  14 static const signed char hexindex[] = {
  15     -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  16     -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  17     -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  18      0, 1, 2, 3, 4, 5, 6, 7, 8, 9,-1,-1,-1,-1,-1,-1,
  19     -1,10,11,12,13,14,15,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  20     -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-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,-1,-1,-1,-1,-1,-1,-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     -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  26     -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  27     -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  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,-1,-1,-1,-1,-1
  31 };
  32
  33 static const signed char index_64[128] = {
  34     -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
  35     -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
  36     -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,62, -1,-1,-1,63,
  37     52,53,54,55, 56,57,58,59, 60,61,-1,-1, -1,-1,-1,-1,
  38     -1, 0, 1, 2,  3, 4, 5, 6,  7, 8, 9,10, 11,12,13,14,
  39     15,16,17,18, 19,20,21,22, 23,24,25,-1, -1,-1,-1,-1,
  40     -1,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
  41     41,42,43,44, 45,46,47,48, 49,50,51,-1, -1,-1,-1,-1
  42 };
  43
  44 #define char64(c) (((unsigned char) (c) > 127) ? -1 : index_64[(unsigned char) (c)])
  45
  46 /*
  47  * Decode two quoted-pair characters
  48  */
  49
  50 int
  51 decode_qp (unsigned char byte1, unsigned char byte2)
  52 {
  53     if (hexindex[byte1] == -1 || hexindex[byte2] == -1)
  54         return -1;
  55     return hexindex[byte1] << 4 | hexindex[byte2];
  56 }
  57
  58 /* Check if character is linear whitespace */
  59 #define is_lws(c)  ((c) == ' ' || (c) == '\t' || (c) == '\n')
  60
  61
  62 /*
  63  * Decode the string as a RFC-2047 header field
  64  */
  65
  66 /* Add character to the destination buffer, and bomb out if it fills up */
  67 #define ADDCHR(C) do { *q++ = (C); dstlen--; if (!dstlen) goto buffull; } while (0)
  68
  69 int
  70 decode_rfc2047 (char *str, char *dst, size_t dstlen)
  71 {
  72     char *p, *q, *pp;
  73     char *startofmime, *endofmime, *endofcharset;
  74     int c, quoted_printable;
  75     int encoding_found = 0;     /* did we decode anything?                */
  76     int between_encodings = 0;  /* are we between two encodings?          */
  77     int equals_pending = 0;     /* is there a '=' pending?                */
  78     int whitespace = 0;         /* how much whitespace between encodings? */
  79 #ifdef HAVE_ICONV
  80     int use_iconv = 0;          /* are we converting encoding with iconv? */
  81     iconv_t cd = NULL;
  82     int fromutf8 = 0;
  83     char *saveq, *convbuf = NULL;
  84     size_t savedstlen;
  85 #endif
  86
  87     if (!str)
  88         return 0;
  89
  90     /*
  91      * Do a quick and dirty check for the '=' character.
  92      * This should quickly eliminate many cases.
  93      */
  94     if (!strchr (str, '='))
  95         return 0;
  96
  97     for (p = str, q = dst; *p; p++) {
  98
  99         /* reset iconv */
 100 #ifdef HAVE_ICONV
 101         if (use_iconv) {
 102             iconv_close(cd);
 103             use_iconv = 0;
 104         }
 105 #endif
 106         /*
 107          * If we had an '=' character pending from
 108          * last iteration, then add it first.
 109          */
 110         if (equals_pending) {
 111             ADDCHR('=');
 112             equals_pending = 0;
 113             between_encodings = 0;      /* we have added non-whitespace text */
 114         }
 115
 116         if (*p != '=') {
 117             /* count linear whitespace while between encodings */
 118             if (between_encodings && is_lws(*p))
 119                 whitespace++;
 120             else
 121                 between_encodings = 0;  /* we have added non-whitespace text */
 122             ADDCHR(*p);
 123             continue;
 124         }
 125
 126         equals_pending = 1;     /* we have a '=' pending */
 127
 128         /* Check for initial =? */
 129         if (*p == '=' && p[1] == '?' && p[2]) {
 130             startofmime = p + 2;
 131
 132             /* Scan ahead for the next '?' character */
 133             for (pp = startofmime; *pp && *pp != '?'; pp++)
 134                 ;
 135
 136             if (!*pp)
 137                 continue;
 138
 139             /*
 140              * RFC 2231 specifies that language information can appear
 141              * in a charset specification like so:
 142              *
 143              * =?us-ascii*en?Q?Foo?=
 144              *
 145              * Right now we don't use language information, so ignore it.
 146              */
 147
 148             for (endofcharset = startofmime;
 149                         *endofcharset != '*' && endofcharset < pp;
 150                                                         endofcharset++)
 151                 ;
 152
 153             /* Check if character set can be handled natively */
 154             if (!check_charset(startofmime, endofcharset - startofmime)) {
 155 #ifdef HAVE_ICONV
 156                 /* .. it can't. We'll use iconv then. */
 157                 *endofcharset = '\0';
 158                 cd = iconv_open(get_charset(), startofmime);
 159                 fromutf8 = !strcasecmp(startofmime, "UTF-8");
 160                 *pp = '?';
 161                 if (cd == (iconv_t)-1) continue;
 162                 use_iconv = 1;
 163 #else
 164                 continue;
 165 #endif
 166             }
 167
 168             startofmime = pp + 1;
 169
 170             /* Check for valid encoding type */
 171             if (*startofmime != 'B' && *startofmime != 'b' &&
 172                 *startofmime != 'Q' && *startofmime != 'q')
 173                 continue;
 174
 175             /* Is encoding quoted printable or base64? */
 176             quoted_printable = (*startofmime == 'Q' || *startofmime == 'q');
 177             startofmime++;
 178
 179             /* Check for next '?' character */
 180             if (*startofmime != '?')
 181                 continue;
 182             startofmime++;
 183
 184             /*
 185              * Scan ahead for the ending ?=
 186              *
 187              * While doing this, we will also check if encoded
 188              * word has any embedded linear whitespace.
 189              */
 190             endofmime = NULL;
 191             for (pp = startofmime; *pp && *(pp+1); pp++) {
 192                 if (is_lws(*pp))
 193                     break;
 194                 if (*pp == '?' && pp[1] == '=') {
 195                     endofmime = pp;
 196                     break;
 197                 }
 198             }
 199             if (is_lws(*pp) || endofmime == NULL)
 200                 continue;
 201
 202             /*
 203              * We've found an encoded word, so we can drop
 204              * the '=' that was pending
 205              */
 206             equals_pending = 0;
 207
 208             /*
 209              * If we are between two encoded words separated only by
 210              * linear whitespace, then we ignore the whitespace.
 211              * We will roll back the buffer the number of whitespace
 212              * characters we've seen since last encoded word.
 213              */
 214             if (between_encodings) {
 215                 q -= whitespace;
 216                 dstlen += whitespace;
 217             }
 218
 219 #ifdef HAVE_ICONV
 220             /*
 221              * empty encoded text. This ensures that we don't
 222              * malloc 0 bytes but skip on to the end
 223              */
 224             if (endofmime == startofmime && use_iconv) {
 225                 use_iconv = 0;
 226                 iconv_close(cd);
 227             }
 228
 229             if (use_iconv) {
 230                 saveq = q;
 231                 savedstlen = dstlen;
 232                 q = convbuf = mh_xmalloc(endofmime - startofmime);
 233             }
 234 /* ADDCHR2 is for adding characters when q is or might be convbuf:
 235  * in this case on buffer-full we want to run iconv before returning.
 236  * I apologise for the dreadful name.
 237  */
 238 #define ADDCHR2(C) do { *q++ = (C); dstlen--; if (!dstlen) goto iconvbuffull; } while (0)
 239 #else
 240 #define ADDCHR2(C) ADDCHR(C)
 241 #endif
 242
 243             /* Now decode the text */
 244             if (quoted_printable) {
 245                 for (pp = startofmime; pp < endofmime; pp++) {
 246                     if (*pp == '=') {
 247                         c = decode_qp (pp[1], pp[2]);
 248                         if (c == -1)
 249                             continue;
 250                         if (c != 0)
 251                             *q++ = c;
 252                         pp += 2;
 253                     } else if (*pp == '_') {
 254                         ADDCHR2(' ');
 255                     } else {
 256                         ADDCHR2(*pp);
 257                     }
 258                 }
 259             } else {
 260                 /* base64 */
 261                 int c1, c2, c3, c4;
 262                 c1 = c2 = c3 = c4 = -1;
 263
 264                 pp = startofmime;
 265                 while (pp < endofmime) {
 266                     /* 6 + 2 bits */
 267                     while ((pp < endofmime) &&
 268                            ((c1 = char64(*pp)) == -1)) {
 269                         pp++;
 270                     }
 271                     if (pp < endofmime) {
 272                         pp++;
 273                     }
 274                     while ((pp < endofmime) &&
 275                            ((c2 = char64(*pp)) == -1)) {
 276                         pp++;
 277                     }
 278                     if (pp < endofmime && c1 != -1 && c2 != -1) {
 279                         ADDCHR2((c1 << 2) | (c2 >> 4));
 280                         pp++;
 281                     }
 282                     /* 4 + 4 bits */
 283                     while ((pp < endofmime) &&
 284                            ((c3 = char64(*pp)) == -1)) {
 285                         pp++;
 286                     }
 287                     if (pp < endofmime && c2 != -1 && c3 != -1) {
 288                         ADDCHR2(((c2 & 0xF) << 4) | (c3 >> 2));
 289                         pp++;
 290                     }
 291                     /* 2 + 6 bits */
 292                     while ((pp < endofmime) &&
 293                            ((c4 = char64(*pp)) == -1)) {
 294                         pp++;
 295                     }
 296                     if (pp < endofmime && c3 != -1 && c4 != -1) {
 297                         ADDCHR2(((c3 & 0x3) << 6) | (c4));
 298                         pp++;
 299                     }
 300                 }
 301             }
 302
 303 #ifdef HAVE_ICONV
 304         iconvbuffull:
 305             /* NB that the string at convbuf is not necessarily NUL terminated here:
 306              * q points to the first byte after the valid part.
 307              */
 308             /* Convert to native character set */
 309             if (use_iconv) {
 310                 size_t inbytes = q - convbuf;
 311                 ICONV_CONST char *start = convbuf;
 312
 313                 while (inbytes) {
 314                     if (iconv(cd, &start, &inbytes, &saveq, &savedstlen) ==
 315                             (size_t)-1) {
 316                         if (errno != EILSEQ) break;
 317                         /* character couldn't be converted. we output a `?'
 318                          * and try to carry on which won't work if
 319                          * either encoding was stateful */
 320                         iconv (cd, 0, 0, &saveq, &savedstlen);
 321                         if (!savedstlen)
 322                             break;
 323                         *saveq++ = '?';
 324                         savedstlen--;
 325                         if (!savedstlen)
 326                             break;
 327                         /* skip to next input character */
 328                         if (fromutf8) {
 329                             for (++start, --inbytes;
 330                                  start < q  &&  (*start & 192) == 128;
 331                                  ++start, --inbytes)
 332                                 continue;
 333                         } else
 334                             start++, inbytes--;
 335                         if (start >= q)
 336                             break;
 337                     }
 338                 }
 339                 q = saveq;
 340                 /* Stop now if (1) we hit the end of the buffer trying to do
 341                  * MIME decoding and have just iconv-converted a partial string
 342                  * or (2) our iconv-conversion hit the end of the buffer.
 343                  */
 344                 if (!dstlen || !savedstlen)
 345                     goto buffull;
 346                 dstlen = savedstlen;
 347                 free(convbuf);
 348             }
 349 #endif
 350
 351             /*
 352              * Now that we are done decoding this particular
 353              * encoded word, advance string to trailing '='.
 354              */
 355             p = endofmime + 1;
 356
 357             encoding_found = 1;         /* we found (at least 1) encoded word */
 358             between_encodings = 1;      /* we have just decoded something     */
 359             whitespace = 0;             /* re-initialize amount of whitespace */
 360         }
 361     }
 362 #ifdef HAVE_ICONV
 363     if (use_iconv) iconv_close(cd);
 364 #endif
 365
 366     /* If an equals was pending at end of string, add it now. */
 367     if (equals_pending)
 368         ADDCHR('=');
 369     *q = '\0';
 370
 371     return encoding_found;
 372
 373   buffull:
 374     /* q is currently just off the end of the buffer, so rewind to NUL terminate */
 375     q--;
 376     *q = '\0';
 377     return encoding_found;
 378 }