1 /*
2 * rfc2047.c -- decode RFC-2047 header format
3 */
4
5 #ifndef lint
6 static char sccsi2[] = "%W% (Sun) %G%";
7 #endif
8
9 /*
10 * Copyright (c) 1997-1998 Richard Coleman
11 * All rights reserved.
12 *
13 * Permission is hereby granted, without written agreement and without
14 * license or royalty fees, to use, copy, modify, and distribute this
15 * software and to distribute modified versions of this software for any
16 * purpose, provided that the above copyright notice and the following two
17 * paragraphs appear in all copies of this software.
18 *
19 * In no event shall Richard Coleman be liable to any party for direct,
20 * indirect, special, incidental, or consequential damages arising out of
21 * the use of this software and its documentation, even if Richard Coleman
22 * has been advised of the possibility of such damage.
23 *
24 * Richard Coleman specifically disclaims any warranties, including, but
25 * not limited to, the implied warranties of merchantability and fitness
26 * for a particular purpose. The software provided hereunder is on an "as
27 * is" basis, and Richard Coleman has no obligation to provide maintenance,
28 * support, updates, enhancements, or modifications.
29 */
30
31 /*
32 * Parts of this code were derived from metamail, which is ...
33 *
34 * Copyright (c) 1991 Bell Communications Research, Inc. (Bellcore)
35 *
36 * Permission to use, copy, modify, and distribute this material
37 * for any purpose and without fee is hereby granted, provided
38 * that the above copyright notice and this permission notice
39 * appear in all copies, and that the name of Bellcore not be
40 * used in advertising or publicity pertaining to this
41 * material without the specific, prior written permission
42 * of an authorized representative of Bellcore. BELLCORE
43 * MAKES NO REPRESENTATIONS ABOUT THE ACCURACY OR SUITABILITY
44 * OF THIS MATERIAL FOR ANY PURPOSE. IT IS PROVIDED "AS IS",
45 * WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES.
46 */
47
48 /*
49 * Copyright (c) 1998, by Sun Microsystems, Inc.
50 * All rights reserved.
51 */
52
53 #include <string.h>
54
55 typedef int bool;
56
57 #define FALSE 0
58 #define TRUE 1
59
60 static signed char hexindex[] = {
61 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
62 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
63 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
64 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
65 -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
66 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
67 -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
68 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
69 };
70
71 static signed char index_64[128] = {
72 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
73 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
74 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
75 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
76 -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
77 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
78 -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
79 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1
80 };
81
82 #define char64(c) (((unsigned char) (c) > 127) ? -1 : \
83 index_64[(unsigned char) (c)])
84
85 static int
unqp(unsigned char byte1,unsigned char byte2)86 unqp(unsigned char byte1, unsigned char byte2)
87 {
88 if (hexindex[byte1] == -1 || hexindex[byte2] == -1)
89 return (-1);
90 return (hexindex[byte1] << 4 | hexindex[byte2]);
91 }
92
93 /* Check if character is linear whitespace */
94 #define is_lws(c) ((c) == ' ' || (c) == '\t' || (c) == '\n')
95
96 /*
97 * Decode the string as a RFC-2047 header field
98 */
99
100 bool
decode_rfc2047(char * str,char * dst,char * charset)101 decode_rfc2047(char *str, char *dst, char *charset)
102 {
103 char *p, *q, *pp;
104 char *startofmime, *endofmime;
105 int c, quoted_printable;
106 bool encoding_found = FALSE; /* did we decode anything? */
107 bool between_encodings = FALSE; /* are we between two encodings? */
108 bool equals_pending = FALSE; /* is there a '=' pending? */
109 int whitespace = 0; /* how much whitespace between encodings? */
110
111 if (str == NULL)
112 return (FALSE);
113
114 /*
115 * Do a quick and dirty check for the '=' character.
116 * This should quickly eliminate many cases.
117 */
118 if (!strchr(str, '='))
119 return (FALSE);
120
121 for (p = str, q = dst; *p; p++) {
122 /*
123 * If we had an '=' character pending from
124 * last iteration, then add it first.
125 */
126 if (equals_pending) {
127 *q++ = '=';
128 equals_pending = FALSE;
129 between_encodings = FALSE; /* we added non-WS text */
130 }
131
132 if (*p != '=') {
133 /* count linear whitespace while between encodings */
134 if (between_encodings && is_lws(*p))
135 whitespace++;
136 else
137 between_encodings = FALSE; /* non-WS added */
138 *q++ = *p;
139 continue;
140 }
141
142 equals_pending = TRUE; /* we have a '=' pending */
143
144 /* Check for initial =? */
145 if (*p == '=' && p[1] && p[1] == '?' && p[2]) {
146 startofmime = p + 2;
147
148 /* Scan ahead for the next '?' character */
149 for (pp = startofmime; *pp && *pp != '?'; pp++)
150 ;
151
152 if (!*pp)
153 continue;
154
155 strncpy(charset, startofmime, pp - startofmime);
156 charset[pp - startofmime] = '\0';
157
158 startofmime = pp + 1;
159
160 /* Check for valid encoding type */
161 if (*startofmime != 'B' && *startofmime != 'b' &&
162 *startofmime != 'Q' && *startofmime != 'q')
163 continue;
164
165 /* Is encoding quoted printable or base64? */
166 quoted_printable = (*startofmime == 'Q' ||
167 *startofmime == 'q');
168 startofmime++;
169
170 /* Check for next '?' character */
171 if (*startofmime != '?')
172 continue;
173 startofmime++;
174
175 /*
176 * Scan ahead for the ending ?=
177 *
178 * While doing this, we will also check if encoded
179 * word has any embedded linear whitespace.
180 */
181 endofmime = NULL;
182 for (pp = startofmime; *pp && *(pp+1); pp++) {
183 if (is_lws(*pp))
184 break;
185 else if (*pp == '?' && pp[1] == '=') {
186 endofmime = pp;
187 break;
188 }
189 }
190 if (is_lws(*pp) || endofmime == NULL)
191 continue;
192
193 /*
194 * We've found an encoded word, so we can drop
195 * the '=' that was pending
196 */
197 equals_pending = FALSE;
198
199 /*
200 * If we are between two encoded words separated only
201 * by linear whitespace, then we ignore the whitespace.
202 * We will roll back the buffer the number of whitespace
203 * characters we've seen since last encoded word.
204 */
205 if (between_encodings)
206 q -= whitespace;
207
208 /* Now decode the text */
209 if (quoted_printable) {
210 for (pp = startofmime; pp < endofmime; pp++) {
211 if (*pp == '=') {
212 c = unqp(pp[1], pp[2]);
213 if (c == -1)
214 continue;
215 if (c != 0)
216 *q++ = c;
217 pp += 2;
218 } else if (*pp == '_')
219 *q++ = ' ';
220 else
221 *q++ = *pp;
222 }
223 } else {
224 /* base64 */
225 int c1, c2, c3, c4;
226
227 pp = startofmime;
228 while (pp < endofmime) {
229 /* 6 + 2 bits */
230 while ((pp < endofmime) &&
231 ((c1 = char64(*pp)) == -1)) {
232 pp++;
233 }
234 if (pp < endofmime)
235 pp++;
236 while ((pp < endofmime) &&
237 ((c2 = char64(*pp)) == -1)) {
238 pp++;
239 }
240 if (pp < endofmime && c1 != -1 &&
241 c2 != -1) {
242 *q++ = (c1 << 2) | (c2 >> 4);
243 pp++;
244 }
245 /* 4 + 4 bits */
246 while ((pp < endofmime) &&
247 ((c3 = char64(*pp)) == -1)) {
248 pp++;
249 }
250 if (pp < endofmime && c2 != -1 &&
251 c3 != -1) {
252 *q++ = ((c2 & 0xF) << 4) |
253 (c3 >> 2);
254 pp++;
255 }
256 /* 2 + 6 bits */
257 while ((pp < endofmime) &&
258 ((c4 = char64(*pp)) == -1)) {
259 pp++;
260 }
261 if (pp < endofmime && c3 != -1 &&
262 c4 != -1) {
263 *q++ = ((c3 & 0x3) << 6) | (c4);
264 pp++;
265 }
266 }
267 }
268
269 /*
270 * Now that we are done decoding this particular
271 * encoded word, advance string to trailing '='.
272 */
273 p = endofmime + 1;
274
275 encoding_found = TRUE; /* found (>= 1) encoded word */
276 between_encodings = TRUE; /* just decoded something */
277 whitespace = 0; /* re-initialize amount of whitespace */
278 }
279 }
280
281 /* If an equals was pending at end of string, add it now. */
282 if (equals_pending)
283 *q++ = '=';
284 *q = '\0';
285
286 return (encoding_found);
287 }
288