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
   8 #include <h/mh.h>
   9
  10 static signed char hexindex[] = {
  11     -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  12     -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  13     -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
  14      0, 1, 2, 3, 4, 5, 6, 7, 8, 9,-1,-1,-1,-1,-1,-1,
  15     -1,10,11,12,13,14,15,-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     -1,10,11,12,13,14,15,-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 };
  20
  21 static signed char index_64[128] = {
  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,-1,62, -1,-1,-1,63,
  25     52,53,54,55, 56,57,58,59, 60,61,-1,-1, -1,-1,-1,-1,
  26     -1, 0, 1, 2,  3, 4, 5, 6,  7, 8, 9,10, 11,12,13,14,
  27     15,16,17,18, 19,20,21,22, 23,24,25,-1, -1,-1,-1,-1,
  28     -1,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
  29     41,42,43,44, 45,46,47,48, 49,50,51,-1, -1,-1,-1,-1
  30 };
  31
  32 #define char64(c) (((unsigned char) (c) > 127) ? -1 : index_64[(unsigned char) (c)])
  33
  34 static int
  35 unqp (unsigned char byte1, unsigned char byte2)
  36 {
  37     if (hexindex[byte1] == -1 || hexindex[byte2] == -1)
  38         return -1;
  39     return (hexindex[byte1] << 4 | hexindex[byte2]);
  40 }
  41
  42 /* Check if character is linear whitespace */
  43 #define is_lws(c)  ((c) == ' ' || (c) == '\t' || (c) == '\n')
  44
  45
  46 /*
  47  * Decode the string as a RFC-2047 header field
  48  */
  49
  50 int
  51 decode_rfc2047 (char *str, char *dst)
  52 {
  53     char *p, *q, *pp;
  54     char *startofmime, *endofmime;
  55     int c, quoted_printable;
  56     int encoding_found = 0;     /* did we decode anything?                */
  57     int between_encodings = 0;  /* are we between two encodings?          */
  58     int equals_pending = 0;     /* is there a '=' pending?                */
  59     int whitespace = 0;         /* how much whitespace between encodings? */
  60
  61     if (!str)
  62         return 0;
  63
  64     /*
  65      * Do a quick and dirty check for the '=' character.
  66      * This should quickly eliminate many cases.
  67      */
  68     if (!strchr (str, '='))
  69         return 0;
  70
  71     for (p = str, q = dst; *p; p++) {
  72         /*
  73          * If we had an '=' character pending from
  74          * last iteration, then add it first.
  75          */
  76         if (equals_pending) {
  77             *q++ = '=';
  78             equals_pending = 0;
  79             between_encodings = 0;      /* we have added non-whitespace text */
  80         }
  81
  82         if (*p != '=') {
  83             /* count linear whitespace while between encodings */
  84             if (between_encodings && is_lws(*p))
  85                 whitespace++;
  86             else
  87                 between_encodings = 0;  /* we have added non-whitespace text */
  88             *q++ = *p;
  89             continue;
  90         }
  91
  92         equals_pending = 1;     /* we have a '=' pending */
  93
  94         /* Check for initial =? */
  95         if (*p == '=' && p[1] && p[1] == '?' && p[2]) {
  96             startofmime = p + 2;
  97
  98             /* Scan ahead for the next '?' character */
  99             for (pp = startofmime; *pp && *pp != '?'; pp++)
 100                 ;
 101
 102             if (!*pp)
 103                 continue;
 104
 105             /* Check if character set is OK */
 106             if (!check_charset(startofmime, pp - startofmime))
 107                 continue;
 108
 109             startofmime = pp + 1;
 110
 111             /* Check for valid encoding type */
 112             if (*startofmime != 'B' && *startofmime != 'b' &&
 113                 *startofmime != 'Q' && *startofmime != 'q')
 114                 continue;
 115
 116             /* Is encoding quoted printable or base64? */
 117             quoted_printable = (*startofmime == 'Q' || *startofmime == 'q');
 118             startofmime++;
 119
 120             /* Check for next '?' character */
 121             if (*startofmime != '?')
 122                 continue;
 123             startofmime++;
 124
 125             /*
 126              * Scan ahead for the ending ?=
 127              *
 128              * While doing this, we will also check if encoded
 129              * word has any embedded linear whitespace.
 130              */
 131             endofmime = NULL;
 132             for (pp = startofmime; *pp && *(pp+1); pp++) {
 133                 if (is_lws(*pp)) {
 134                     break;
 135                 } else if (*pp == '?' && pp[1] == '=') {
 136                     endofmime = pp;
 137                     break;
 138                 }
 139             }
 140             if (is_lws(*pp) || endofmime == NULL)
 141                 continue;
 142
 143             /*
 144              * We've found an encoded word, so we can drop
 145              * the '=' that was pending
 146              */
 147             equals_pending = 0;
 148
 149             /*
 150              * If we are between two encoded words separated only by
 151              * linear whitespace, then we ignore the whitespace.
 152              * We will roll back the buffer the number of whitespace
 153              * characters we've seen since last encoded word.
 154              */
 155             if (between_encodings)
 156                 q -= whitespace;
 157
 158             /* Now decode the text */
 159             if (quoted_printable) {
 160                 for (pp = startofmime; pp < endofmime; pp++) {
 161                     if (*pp == '=') {
 162                         c = unqp (pp[1], pp[2]);
 163                         if (c == -1)
 164                             continue;
 165                         if (c != 0)
 166                             *q++ = c;
 167                         pp += 2;
 168                     } else if (*pp == '_') {
 169                         *q++ = ' ';
 170                     } else {
 171                         *q++ = *pp;
 172                     }
 173                 }
 174             } else {
 175                 /* base64 */
 176                 int c1, c2, c3, c4;
 177
 178                 pp = startofmime;
 179                 while (pp < endofmime) {
 180                     /* 6 + 2 bits */
 181                     while ((pp < endofmime) &&
 182                            ((c1 = char64(*pp)) == -1)) {
 183                         pp++;
 184                     }
 185                     if (pp < endofmime) {
 186                         pp++;
 187                     }
 188                     while ((pp < endofmime) &&
 189                            ((c2 = char64(*pp)) == -1)) {
 190                         pp++;
 191                     }
 192                     if (pp < endofmime && c1 != -1 && c2 != -1) {
 193                         *q++ = (c1 << 2) | (c2 >> 4);
 194                         pp++;
 195                     }
 196                     /* 4 + 4 bits */
 197                     while ((pp < endofmime) &&
 198                            ((c3 = char64(*pp)) == -1)) {
 199                         pp++;
 200                     }
 201                     if (pp < endofmime && c2 != -1 && c3 != -1) {
 202                         *q++ = ((c2 & 0xF) << 4) | (c3 >> 2);
 203                         pp++;
 204                     }
 205                     /* 2 + 6 bits */
 206                     while ((pp < endofmime) &&
 207                            ((c4 = char64(*pp)) == -1)) {
 208                         pp++;
 209                     }
 210                     if (pp < endofmime && c3 != -1 && c4 != -1) {
 211                         *q++ = ((c3 & 0x3) << 6) | (c4);
 212                         pp++;
 213                     }
 214                 }
 215             }
 216
 217             /*
 218              * Now that we are done decoding this particular
 219              * encoded word, advance string to trailing '='.
 220              */
 221             p = endofmime + 1;
 222
 223             encoding_found = 1;         /* we found (at least 1) encoded word */
 224             between_encodings = 1;      /* we have just decoded something     */
 225             whitespace = 0;             /* re-initialize amount of whitespace */
 226         }
 227     }
 228
 229     /* If an equals was pending at end of string, add it now. */
 230     if (equals_pending)
 231         *q++ = '=';
 232     *q = '\0';
 233
 234     return encoding_found;
 235 }