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

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