1 /*
2  * Copyright (c) 2020 Martijn van Duren <martijn@openbsd.org>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <ctype.h>
18 #include <errno.h>
19 #include <stddef.h>
20 #include <string.h>
21 #include <strings.h>
22 
23 #include "mheader.h"
24 
25 char *
26 osmtpd_mheader_skip_sp(char *ptr, int optional)
27 {
28 	if (ptr[0] == 0x20)
29 		return ptr + 1;
30 	return optional ? ptr : NULL;
31 }
32 
33 char *
34 osmtpd_mheader_skip_htab(char *ptr, int optional)
35 {
36 	if (ptr[0] == 0x9)
37 		return ptr + 1;
38 	return optional ? ptr : NULL;
39 }
40 
41 char *
42 osmtpd_mheader_skip_wsp(char *ptr, int optional)
43 {
44 	char *start = ptr;
45 
46 	if ((ptr = osmtpd_mheader_skip_sp(start, 0)) != NULL ||
47 	    (ptr = osmtpd_mheader_skip_htab(start, 0)) != NULL)
48 		return ptr;
49 	return optional ? ptr : NULL;
50 }
51 
52 char *
53 osmtpd_mheader_skip_crlf(char *ptr, int optional)
54 {
55 	if (ptr[0] == 13 && ptr[1] == 10)
56 		return ptr + 2;
57 	return optional ? ptr : NULL;
58 }
59 
60 char *
61 osmtpd_mheader_skip_vchar(char *ptr, int optional)
62 {
63 	if (ptr[0] >= 0x21 && ptr[0] <= 0x7e)
64 		return ptr + 1;
65 	return optional ? ptr : NULL;
66 }
67 
68 char *
69 osmtpd_mheader_skip_lf(char *ptr, int optional)
70 {
71 	if (ptr[0] == 0xa)
72 		return ptr + 1;
73 	return optional ? ptr : NULL;
74 }
75 
76 char *
77 osmtpd_mheader_skip_cr(char *ptr, int optional)
78 {
79 	if (ptr[0] == 0xd)
80 		return ptr + 1;
81 	return optional ? ptr : NULL;
82 }
83 
84 char *
85 osmtpd_mheader_skip_alpha(char *ptr, int optional)
86 {
87 	if ((ptr[0] >= 0x41 && ptr[0] <= 0x5a) ||
88 	    (ptr[0] >= 0x61 && ptr[0] <= 0x7a))
89 		return ptr + 1;
90 	return optional ? ptr : NULL;
91 }
92 
93 char *
94 osmtpd_mheader_skip_digit(char *ptr, int optional)
95 {
96 	if (ptr[0] >= 0x30 && ptr[0] <= 0x39)
97 		return ptr + 1;
98 	return optional ? ptr : NULL;
99 }
100 
101 char *
102 osmtpd_mheader_skip_dquote(char *ptr, int optional)
103 {
104 	if (ptr[0] == 0x22)
105 		return ptr + 1;
106 	return optional ? ptr : NULL;
107 }
108 
109 char *
110 osmtpd_mheader_skip_obs_fws(char *ptr, int optional)
111 {
112 	char *start = ptr, *prev;
113 
114 	if ((ptr = osmtpd_mheader_skip_wsp(ptr, 0)) == NULL)
115 		return optional ? start : NULL;
116 	prev = ptr;
117 	while ((ptr = osmtpd_mheader_skip_wsp(ptr, 0)) != NULL)
118 		prev = ptr;
119 
120 	ptr = prev;
121 	while (1) {
122 		if ((ptr = osmtpd_mheader_skip_crlf(ptr, 0)) == NULL)
123 			return prev;
124 		if ((ptr = osmtpd_mheader_skip_wsp(ptr, 0)) == NULL)
125 			return prev;
126 		prev = ptr;
127 		while ((ptr = osmtpd_mheader_skip_wsp(ptr, 0)) != NULL)
128 			prev = ptr;
129 		ptr = prev;
130 	}
131 }
132 
133 char *
134 osmtpd_mheader_skip_fws(char *ptr, int optional)
135 {
136 	char *start = ptr, *prev = ptr;
137 
138 	while ((ptr = osmtpd_mheader_skip_wsp(ptr, 0)) != NULL)
139 		prev = ptr;
140 	if ((ptr = osmtpd_mheader_skip_crlf(prev, 1)) == prev)
141 		ptr = start;
142 	if ((ptr = osmtpd_mheader_skip_wsp(ptr, 0)) == NULL)
143 		return osmtpd_mheader_skip_obs_fws(start, optional);
144 	prev = ptr;
145 	while ((ptr = osmtpd_mheader_skip_wsp(ptr, 0)) != NULL)
146 		prev = ptr;
147 	return prev;
148 }
149 
150 char *
151 osmtpd_mheader_skip_obs_no_ws_ctl(char *ptr, int optional)
152 {
153 	if ((ptr[0] >= 1 && ptr[0] <= 8) || ptr[0] == 11 || ptr[0] == 12 ||
154 	    (ptr[0] >= 14 && ptr[0] <= 31) || ptr[0] == 127)
155 		return ptr + 1;
156 	return optional ? ptr : NULL;
157 }
158 
159 char *
160 osmtpd_mheader_skip_obs_ctext(char *ptr, int optional)
161 {
162 	return osmtpd_mheader_skip_obs_no_ws_ctl(ptr, optional);
163 }
164 
165 char *
166 osmtpd_mheader_skip_ctext(char *ptr, int optional)
167 {
168 	char *start = ptr;
169 
170 	if ((ptr[0] >= 33 && ptr[0] <= 39) || (ptr[0] >= 42 && ptr[0] <= 91) ||
171 	    (ptr[0] >= 93 && ptr[0] <= 126))
172 		return ptr + 1;
173 	if ((ptr = osmtpd_mheader_skip_obs_ctext(ptr, 0)) != NULL)
174 		return ptr;
175 	return optional ? start : NULL;
176 }
177 
178 char *
179 osmtpd_mheader_skip_obs_qp(char *ptr, int optional)
180 {
181 	char *start = ptr;
182 
183 	if (ptr[0] == '\\' && (
184 	    (ptr = osmtpd_mheader_skip_obs_no_ws_ctl(start + 1, 0)) != NULL ||
185 	    (ptr = osmtpd_mheader_skip_lf(start + 1, 0)) != NULL ||
186 	    (ptr = osmtpd_mheader_skip_cr(start + 1, 0)) != NULL))
187 		return ptr;
188 	return optional ? start : NULL;
189 }
190 
191 char *
192 osmtpd_mheader_skip_quoted_pair(char *ptr, int optional)
193 {
194 	char *start = ptr;
195 
196 	if (ptr[0] == '\\' && (
197 	    (ptr = osmtpd_mheader_skip_vchar(start + 1, 0)) != NULL ||
198 	    (ptr = osmtpd_mheader_skip_wsp(start + 1, 0)) != NULL))
199 		return ptr;
200 	return osmtpd_mheader_skip_obs_qp(start, optional);
201 }
202 
203 char *
204 osmtpd_mheader_skip_ccontent(char *ptr, int optional)
205 {
206 	char *start = ptr;
207 
208 	if ((ptr = osmtpd_mheader_skip_ctext(ptr, 0)) != NULL)
209 		return ptr;
210 	if ((ptr = osmtpd_mheader_skip_quoted_pair(start, 0)) != NULL)
211 		return ptr;
212 	if ((ptr = osmtpd_mheader_skip_comment(start, 0)) != NULL)
213 		return ptr;
214 	return optional ? start : NULL;
215 }
216 
217 char *
218 osmtpd_mheader_skip_comment(char *ptr, int optional)
219 {
220 	char *start = ptr;
221 
222 	if (ptr++[0] != '(')
223 		return optional ? start : NULL;
224 	while (1) {
225 		ptr = osmtpd_mheader_skip_fws(ptr, 1);
226 		if (ptr[0] == ')')
227 			return ptr + 1;
228 		if ((ptr = osmtpd_mheader_skip_ccontent(ptr, 0)) == NULL)
229 			return optional ? start : NULL;
230 	}
231 }
232 
233 char *
234 osmtpd_mheader_skip_cfws(char *ptr, int optional)
235 {
236 	char *start = ptr, *prev;
237 
238 	while (1) {
239 		ptr = osmtpd_mheader_skip_fws(ptr, 1);
240 		prev = ptr;
241 		if ((ptr = osmtpd_mheader_skip_comment(ptr, 0)) == NULL) {
242 			ptr = prev;
243 			break;
244 		}
245 	}
246 	return ptr == start && !optional ? NULL : ptr;
247 }
248 
249 char *
250 osmtpd_mheader_skip_atext(char *ptr, int optional)
251 {
252 	char *start = ptr;
253 
254 	if ((ptr = osmtpd_mheader_skip_alpha(start, 0)) != NULL ||
255 	    (ptr = osmtpd_mheader_skip_digit(start, 0)) != NULL)
256 		return ptr;
257 	ptr = start;
258 	if (ptr[0] == '!' || ptr[0] == '#' || ptr[0] == '$' || ptr[0] == '%' ||
259 	    ptr[0] == '&' || ptr[0] == '\'' || ptr[0] == '*' || ptr[0] == '+' ||
260 	    ptr[0] == '-' || ptr[0] == '/' || ptr[0] == '=' || ptr[0] == '?' ||
261 	    ptr[0] == '^' || ptr[0] == '_' || ptr[0] == '`' || ptr[0] == '{' ||
262 	    ptr[0] == '|' || ptr[0] == '}' || ptr[0] == '~')
263 		return ptr + 1;
264 	return optional ? start : NULL;
265 }
266 
267 char *
268 osmtpd_mheader_skip_atom(char *ptr, int optional)
269 {
270 	char *start = ptr, *prev;
271 
272 	ptr = osmtpd_mheader_skip_cfws(ptr, 1);
273 	if ((ptr = osmtpd_mheader_skip_atext(ptr, 0)) == NULL)
274 		return optional ? start : NULL;
275 	do {
276 		prev = ptr;
277 		ptr = osmtpd_mheader_skip_atext(ptr, 1);
278 	} while (prev != ptr);
279 	return osmtpd_mheader_skip_cfws(ptr, 1);
280 }
281 
282 char *
283 osmtpd_mheader_skip_dot_atom_text(char *ptr, int optional)
284 {
285 	char *start = ptr, *prev;
286 
287 	if ((ptr = osmtpd_mheader_skip_atext(ptr, 0)) == NULL)
288 		return optional ? start : NULL;
289 	do {
290 		prev = ptr;
291 		ptr = osmtpd_mheader_skip_atext(ptr, 1);
292 	} while (ptr != prev);
293 
294 	while (ptr[0] == '.') {
295 		ptr++;
296 		if ((ptr = osmtpd_mheader_skip_atext(ptr, 0)) == NULL)
297 			return prev;
298 		do {
299 			prev = ptr;
300 			ptr = osmtpd_mheader_skip_atext(ptr, 1);
301 		} while (ptr != prev);
302 	}
303 	return ptr;
304 }
305 
306 char *
307 osmtpd_mheader_skip_dot_atom(char *ptr, int optional)
308 {
309 	char *start = ptr;
310 
311 	ptr = osmtpd_mheader_skip_cfws(ptr, 1);
312 	if ((ptr = osmtpd_mheader_skip_dot_atom_text(ptr, 0)) == NULL)
313 		return optional ? start : NULL;
314 	return osmtpd_mheader_skip_cfws(ptr, 1);
315 }
316 
317 
318 char *
319 osmtpd_mheader_skip_obs_qtext(char *ptr, int optional)
320 {
321 	return osmtpd_mheader_skip_obs_no_ws_ctl(ptr, optional);
322 }
323 
324 char *
325 osmtpd_mheader_skip_qtext(char *ptr, int optional)
326 {
327 	char *start = ptr;
328 
329 	if (ptr[0] == 33 || (ptr[0] >= 35 && ptr[0] <= 91) ||
330 	    (ptr[0] >= 93 && ptr[0] <= 126))
331 		return ptr + 1;
332 	if ((ptr = osmtpd_mheader_skip_obs_qtext(ptr, 0)) != NULL)
333 		return ptr;
334 	return optional ? start : NULL;
335 }
336 
337 char *
338 osmtpd_mheader_skip_qcontent(char *ptr, int optional)
339 {
340 	char *start = ptr;
341 
342 	if ((ptr = osmtpd_mheader_skip_qtext(ptr, 0)) != NULL)
343 		return ptr;
344 	return osmtpd_mheader_skip_quoted_pair(start, optional);
345 }
346 
347 char *
348 osmtpd_mheader_skip_quoted_string(char *ptr, int optional)
349 {
350 	char *start = ptr, *prev;
351 
352 	ptr = osmtpd_mheader_skip_cfws(ptr, 1);
353 	if ((ptr = osmtpd_mheader_skip_dquote(ptr, 0)) == NULL)
354 		return optional ? start : NULL;
355 	prev = ptr;
356 	while (1) {
357 		ptr = osmtpd_mheader_skip_fws(ptr, 1);
358 		if ((ptr = osmtpd_mheader_skip_qcontent(ptr, 0)) == NULL)
359 			break;
360 		prev = ptr;
361 	}
362 	if ((ptr = osmtpd_mheader_skip_dquote(prev, 0)) == NULL)
363 		return optional ? start : NULL;
364 	return osmtpd_mheader_skip_cfws(ptr, 1);
365 }
366 
367 char *
368 osmtpd_mheader_skip_word(char *ptr, int optional)
369 {
370 	char *start = ptr;
371 
372 	if ((ptr = osmtpd_mheader_skip_atom(ptr, 0)) != NULL)
373 		return ptr;
374 	return osmtpd_mheader_skip_quoted_string(start, optional);
375 }
376 
377 char *
378 osmtpd_mheader_skip_obs_phrase(char *ptr, int optional)
379 {
380 	char *start = ptr, *prev;
381 
382 	if ((ptr = osmtpd_mheader_skip_word(ptr, 0)) == NULL)
383 		return optional ? start : NULL;
384 	while (1) {
385 		prev = ptr;
386 		if ((ptr = osmtpd_mheader_skip_word(ptr, 0)) != NULL)
387 			continue;
388 		ptr = prev;
389 		if (ptr[0] == '.') {
390 			ptr++;
391 			continue;
392 		}
393 		if ((ptr = osmtpd_mheader_skip_cfws(ptr, 0)) != NULL)
394 			continue;
395 		return prev;
396 	}
397 }
398 
399 char *
400 osmtpd_mheader_skip_phrase(char *ptr, int optional)
401 {
402 	/* obs-phrase is a superset of phrae */
403 	return osmtpd_mheader_skip_obs_phrase(ptr, optional);
404 #if 0
405 	char *start = ptr, *prev;
406 
407 	if ((ptr = osmtpd_mheader_skip_word(ptr, 0)) == NULL)
408 		return optional ? start : NULL;
409 	while (1) {
410 		prev = ptr;
411 		if ((ptr = osmtpd_mheader_skip_word(ptr, 0)) == NULL)
412 			return prev;
413 	}
414 #endif
415 }
416 
417 char *
418 osmtpd_mheader_skip_obs_local_part(char *ptr, int optional)
419 {
420 	char *start = ptr, *prev;
421 
422 	if ((ptr = osmtpd_mheader_skip_word(ptr, 0)) == NULL)
423 		return optional ? start : NULL;
424 	prev = ptr;
425 	while (ptr[0] == '.') {
426 		ptr++;
427 		if ((ptr = osmtpd_mheader_skip_word(ptr, 0)) == NULL)
428 			return prev;
429 		prev = ptr;
430 	}
431 	return ptr;
432 }
433 
434 char *
435 osmtpd_mheader_skip_local_part(char *ptr, int optional)
436 {
437 	char *start = ptr;
438 
439 	if ((ptr = osmtpd_mheader_skip_dot_atom(ptr, 0)) != NULL)
440 		return ptr;
441 	ptr = start;
442 	if ((ptr = osmtpd_mheader_skip_quoted_string(ptr, 0)) != NULL)
443 		return ptr;
444 	return osmtpd_mheader_skip_obs_local_part(start, optional);
445 }
446 
447 char *
448 osmtpd_mheader_skip_obs_dtext(char *ptr, int optional)
449 {
450 	char *start = ptr;
451 
452 	if ((ptr = osmtpd_mheader_skip_obs_no_ws_ctl(ptr, 0)) != NULL)
453 		return ptr;
454 	return osmtpd_mheader_skip_quoted_pair(start, optional);
455 }
456 
457 char *
458 osmtpd_mheader_skip_dtext(char *ptr, int optional)
459 {
460 	if ((ptr[0] >= 33 && ptr[0] <= 90) || (ptr[0] >= 94 && ptr[0] <= 126))
461 		return ptr + 1;
462 	return osmtpd_mheader_skip_obs_dtext(ptr, optional);
463 
464 }
465 
466 char *
467 osmtpd_mheader_skip_domain_literal(char *ptr, int optional)
468 {
469 	char *start = ptr, *prev;
470 
471 	ptr = osmtpd_mheader_skip_cfws(ptr, 1);
472 	if (ptr++[0] != '[')
473 		return optional ? start : NULL;
474 	while (1) {
475 		ptr = osmtpd_mheader_skip_fws(ptr, 1);
476 		prev = ptr;
477 		if ((ptr = osmtpd_mheader_skip_dtext(ptr, 0)) == NULL) {
478 			ptr = prev;
479 			break;
480 		}
481 	}
482 	if (ptr[0] != ']')
483 		return optional ? start : NULL;
484 	return osmtpd_mheader_skip_cfws(ptr, 1);
485 }
486 
487 char *
488 osmtpd_mheader_skip_obs_domain(char *ptr, int optional)
489 {
490 	char *start = ptr, *prev;
491 
492 	if ((ptr = osmtpd_mheader_skip_atom(ptr, 0)) == NULL)
493 		return optional ? start : NULL;
494 	prev = ptr;
495 	while (1) {
496 		if (ptr++[0] != '.')
497 			return prev;
498 		if ((ptr = osmtpd_mheader_skip_atom(ptr, 0)) == NULL)
499 			return prev;
500 		prev = ptr;
501 	}
502 }
503 
504 char *
505 osmtpd_mheader_skip_domain(char *ptr, int optional)
506 {
507 	char *start = ptr;
508 
509 	if ((ptr = osmtpd_mheader_skip_dot_atom(start, 0)) != NULL)
510 		return ptr;
511 	if ((ptr = osmtpd_mheader_skip_domain_literal(start, 0)) != NULL)
512 		return ptr;
513 	return osmtpd_mheader_skip_obs_domain(start, optional);
514 }
515 
516 char *
517 osmtpd_mheader_skip_display_name(char *ptr, int optional)
518 {
519 	return osmtpd_mheader_skip_phrase(ptr, optional);
520 }
521 
522 char *
523 osmtpd_mheader_skip_obs_domain_list(char *ptr, int optional)
524 {
525 	char *start = ptr, *prev = ptr;
526 
527 	while (1) {
528 		if (ptr[0] == ',') {
529 			ptr++;
530 			prev = ptr;
531 			continue;
532 		} else if ((ptr = osmtpd_mheader_skip_cfws(ptr, 0)) != NULL) {
533 			prev = ptr;
534 			continue;
535 		}
536 		break;
537 	}
538 	ptr = prev;
539 
540 	if (ptr++[0] != '@')
541 		return optional ? start : NULL;
542 	if ((ptr = osmtpd_mheader_skip_domain(ptr, 0)) == NULL)
543 		return optional ? start : NULL;
544 	while (1) {
545 		if (ptr[0] != ',')
546 			break;
547 		ptr++;
548 		ptr = osmtpd_mheader_skip_cfws(ptr, 1);
549 		if (ptr[0] != '@')
550 			continue;
551 		prev = ptr;
552 		if ((ptr = osmtpd_mheader_skip_domain(ptr + 1, 0)) == NULL) {
553 			ptr = prev;
554 			break;
555 		}
556 	}
557 	return ptr;
558 }
559 
560 char *
561 osmtpd_mheader_skip_obs_route(char *ptr, int optional)
562 {
563 	char *start = ptr;
564 
565 	if ((ptr = osmtpd_mheader_skip_obs_domain_list(ptr, 0)) == NULL)
566 		return optional ? start : NULL;
567 	if (ptr++[0] != ':')
568 		return optional ? start : NULL;
569 	return ptr;
570 }
571 
572 char *
573 osmtpd_mheader_skip_addr_spec(char *ptr, int optional)
574 {
575 	char *start = ptr;
576 
577 	if ((ptr = osmtpd_mheader_skip_local_part(ptr, 0)) == NULL)
578 		return optional ? start : NULL;
579 	if (ptr++[0] != '@')
580 		return optional ? start : NULL;
581 	if ((ptr = osmtpd_mheader_skip_domain(ptr, 0)) == NULL)
582 		return optional ? start : NULL;
583 	return ptr;
584 }
585 
586 char *
587 osmtpd_mheader_skip_obs_angle_addr(char *ptr, int optional)
588 {
589 	char *start = ptr;
590 
591 	ptr = osmtpd_mheader_skip_cfws(ptr, 1);
592 	if (ptr++[0] != '<')
593 		return optional ? start : NULL;
594 	if ((ptr = osmtpd_mheader_skip_obs_route(ptr, 0)) == NULL)
595 		return optional ? start : NULL;
596 	if ((ptr = osmtpd_mheader_skip_addr_spec(ptr, 0)) == NULL)
597 		return optional ? start : NULL;
598 	if (ptr++[0] != '>')
599 		return optional ? start : NULL;
600 	return osmtpd_mheader_skip_cfws(ptr, 1);
601 }
602 
603 char *
604 osmtpd_mheader_skip_angle_addr(char *ptr, int optional)
605 {
606 	char *start = ptr;
607 
608 	ptr = osmtpd_mheader_skip_cfws(ptr, 1);
609 	if (ptr++[0] != '<')
610 		return osmtpd_mheader_skip_obs_angle_addr(start, optional);
611 	if ((ptr = osmtpd_mheader_skip_addr_spec(ptr, 0)) == NULL)
612 		return osmtpd_mheader_skip_obs_angle_addr(start, optional);
613 	if (ptr++[0] != '>')
614 		return osmtpd_mheader_skip_obs_angle_addr(start, optional);
615 	return osmtpd_mheader_skip_cfws(ptr, 1);
616 }
617 
618 char *
619 osmtpd_mheader_skip_name_addr(char *ptr, int optional)
620 {
621 	char *start = ptr;
622 
623 	ptr = osmtpd_mheader_skip_display_name(ptr, 1);
624 	if ((ptr = osmtpd_mheader_skip_angle_addr(ptr, 0)) == NULL)
625 		return optional ? start : NULL;
626 	return ptr;
627 }
628 
629 /* Return the domain component of the first mailbox */
630 char *
631 osmtpd_mheader_from_domain(char *ptr)
632 {
633 	char *tmp;
634 
635 	/* from */
636 	if (strncasecmp(ptr, "from:", 5) == 0) {
637 		ptr += 5;
638 	/* obs-from */
639 	} else if (strncasecmp(ptr, "from", 4) == 0) {
640 		ptr += 4;
641 		do {
642 			tmp = ptr;
643 		} while ((ptr = osmtpd_mheader_skip_wsp(ptr, 0)) != NULL);
644 		ptr = tmp;
645 		if (ptr++[0] != ':')
646 			return NULL;
647 	} else {
648 		errno = EINVAL;
649 		return NULL;
650 	}
651 
652 	/* Both from and obs-from use Mailbox-list CRLF */
653 	/* obs-mbox-list has just a prefix compared to mailbox-list */
654 	while (1) {
655 		tmp = ptr;
656 		ptr = osmtpd_mheader_skip_cfws(ptr, 1);
657 		if (ptr++[0] != ',') {
658 			ptr = tmp;
659 			break;
660 		}
661 	}
662 	/* We're only interested in the first mailbox */
663 	if (osmtpd_mheader_skip_name_addr(ptr, 0) != NULL) {
664 		ptr = osmtpd_mheader_skip_display_name(ptr, 1);
665 		ptr = osmtpd_mheader_skip_cfws(ptr, 1);
666 		/* < */
667 		ptr++;
668 		/* addr-spec */
669 		ptr = osmtpd_mheader_skip_local_part(ptr, 0);
670 		/* @ */
671 		ptr++;
672 		tmp = osmtpd_mheader_skip_domain(ptr, 0);
673 		return strndup(ptr, tmp - ptr);
674 	}
675 	if (osmtpd_mheader_skip_addr_spec(ptr, 0) != NULL) {
676 		ptr = osmtpd_mheader_skip_local_part(ptr, 0);
677 		/* @ */
678 		ptr++;
679 		tmp = osmtpd_mheader_skip_domain(ptr, 0);
680 		return strndup(ptr, tmp - ptr);
681 	}
682 	errno = EINVAL;
683 	return NULL;
684 }