src/utils/rfc2047.c

   1
   2 #include <stdio.h>
   3 #include <string.h>
   4
   5 #include "string_utils.h"
   6
   7 /*
   8  * Index_hex and Index_64 imported from Mutt:handler.c
   9  * decode_quotedprintable() and decode_base64() as well
  10  */
  11 static const int index_hex[128] = {
  12 /*       0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F */
  13         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  14         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  15         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  16          0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -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         -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 };
  22
  23 static const int index_64[128] = {
  24 /*       0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F */
  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, 62, -1, -1, -1, 63,
  28         52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
  29         -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
  30         15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
  31         -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
  32         41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1
  33 };
  34
  35 #define HEX_VAL(c) index_hex[(unsigned int)(c)]
  36 #define BASE64_VAL(c) index_64[(unsigned int)(c)]
  37
  38 /* Decode a string from base64 */
  39 void rfc2047_decode_base64(char *dest, const char *src, size_t n)
  40 {
  41         const char *end;
  42
  43         int c;
  44         int b = 0;
  45         int k = 0;
  46
  47         if (!dest || !src || (n == 0)) {
  48                 return;
  49         }
  50
  51         end = src + n;
  52
  53         for ( ; src < end; src++) {
  54                 if (*src == '=')
  55                         break;
  56                 if ((*src & 0x80) || (c = BASE64_VAL(*src)) == -1)
  57                         continue;
  58                 if (k + 6 >= 8) {
  59                         k -= 2;
  60                         *(dest++) = b | (c >> k);
  61                         b = c << (8 - k);
  62                 } else {
  63                         b |= c << (k + 2);
  64                         k += 6;
  65                 }
  66                 *dest = '\0';
  67         }
  68 }
  69
  70 void rfc2047_decode_quoted_printable(char *dest, const char *src, size_t n)
  71 {
  72         const char *end;
  73
  74         if (!dest || !src || (n == 0)) {
  75                 return;
  76         }
  77
  78         end = src + n;
  79
  80         while (src < end) {
  81                 if (*src == '_') {
  82                         *dest = ' ';
  83                 } else if ((*src == '=') && (src + 2 < end) &&
  84                           (!(*(src + 1) & 0x80) && HEX_VAL(*(src + 1)) != -1) &&
  85                           (!(*(src + 2) & 0x80) && HEX_VAL(*(src + 2)) != -1))
  86                 {
  87                         *dest = (HEX_VAL(*(src + 1)) << 4) |
  88                                  HEX_VAL(*(src + 2));
  89                         src += 2;
  90                 } else {
  91                         *dest = *src;
  92                 }
  93                 src++;
  94                 dest++;
  95         }
  96
  97         *dest = '\0';
  98 }
  99
 100 /*
 101  * encoded-word = "=?" charset "?" encoding "?" encoded-text "?="
 102 */
 103 void rfc2047_decode_word(char *dest, const char *src, size_t n)
 104 {
 105         char *start = NULL;
 106         char *end = NULL;
 107
 108         char *encoding;
 109         char *charset;
 110
 111         start = strstr(src, "=?");
 112         end = strstr(src, "?=");
 113
 114         if (!start || !end) {
 115                 strncpy(dest, src, n);
 116                 return;
 117         }
 118
 119         /* Adjust pointers */
 120         start += 2;
 121
 122         charset = start;
 123 #if 0
 124         printf("charset @%d\n", charset - src);
 125 #endif
 126
 127         encoding = strchr(start, '?');
 128         if (encoding == end) {
 129                 /* Something wrong */
 130         }
 131         encoding++;
 132
 133 #if 0
 134         printf("encoding @%d\n", encoding - src);
 135 #endif
 136
 137         start = encoding + 2;
 138
 139         if (*encoding == 'Q') {
 140                 rfc2047_decode_quoted_printable(dest, start, end - start);
 141         } else if (*encoding == 'B') {
 142                 rfc2047_decode_base64(dest, start, end - start);
 143         } else {
 144                 fprintf(stderr, "Unkonwn encoding '%c'\n", *encoding);
 145         }
 146 }