1 /*
2  * Copyright (c) 1983 Eric P. Allman
3  * Copyright (c) 1988 Regents of the University of California.
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms are permitted
7  * provided that the above copyright notice and this paragraph are
8  * duplicated in all such forms and that any documentation,
9  * advertising materials, and other materials related to such
10  * distribution and use acknowledge that the software was developed
11  * by the University of California, Berkeley.  The name of the
12  * University may not be used to endorse or promote products derived
13  * from this software without specific prior written permission.
14  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
15  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
16  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
17  */
18 
19 #ifndef lint
20 static char sccsid[] = "@(#)headers.c	5.13 (Berkeley) 01/01/89";
21 #endif /* not lint */
22 
23 # include <errno.h>
24 # include "sendmail.h"
25 
26 /*
27 **  CHOMPHEADER -- process and save a header line.
28 **
29 **	Called by collect and by readcf to deal with header lines.
30 **
31 **	Parameters:
32 **		line -- header as a text line.
33 **		def -- if set, this is a default value.
34 **
35 **	Returns:
36 **		flags for this header.
37 **
38 **	Side Effects:
39 **		The header is saved on the header list.
40 **		Contents of 'line' are destroyed.
41 */
42 
43 chompheader(line, def)
44 	char *line;
45 	bool def;
46 {
47 	register char *p;
48 	register HDR *h;
49 	HDR **hp;
50 	char *fname;
51 	char *fvalue;
52 	struct hdrinfo *hi;
53 	bool cond = FALSE;
54 	BITMAP mopts;
55 	extern char *crackaddr();
56 
57 	if (tTd(31, 6))
58 		printf("chompheader: %s\n", line);
59 
60 	/* strip off options */
61 	clrbitmap(mopts);
62 	p = line;
63 	if (*p == '?')
64 	{
65 		/* have some */
66 		register char *q = index(p + 1, *p);
67 
68 		if (q != NULL)
69 		{
70 			*q++ = '\0';
71 			while (*++p != '\0')
72 				setbitn(*p, mopts);
73 			p = q;
74 		}
75 		else
76 			usrerr("chompheader: syntax error, line \"%s\"", line);
77 		cond = TRUE;
78 	}
79 
80 	/* find canonical name */
81 	fname = p;
82 	p = index(p, ':');
83 	if (p == NULL)
84 	{
85 		syserr("chompheader: syntax error, line \"%s\"", line);
86 		return (0);
87 	}
88 	fvalue = &p[1];
89 	while (isspace(*--p))
90 		continue;
91 	*++p = '\0';
92 	makelower(fname);
93 
94 	/* strip field value on front */
95 	if (*fvalue == ' ')
96 		fvalue++;
97 
98 	/* see if it is a known type */
99 	for (hi = HdrInfo; hi->hi_field != NULL; hi++)
100 	{
101 		if (strcmp(hi->hi_field, fname) == 0)
102 			break;
103 	}
104 
105 	/* see if this is a resent message */
106 	if (!def && bitset(H_RESENT, hi->hi_flags))
107 		CurEnv->e_flags |= EF_RESENT;
108 
109 	/* if this means "end of header" quit now */
110 	if (bitset(H_EOH, hi->hi_flags))
111 		return (hi->hi_flags);
112 
113 	/* drop explicit From: if same as what we would generate -- for MH */
114 	p = "resent-from";
115 	if (!bitset(EF_RESENT, CurEnv->e_flags))
116 		p += 7;
117 	if (!def && !QueueRun && strcmp(fname, p) == 0)
118 	{
119 		if (CurEnv->e_from.q_paddr != NULL &&
120 		    strcmp(fvalue, CurEnv->e_from.q_paddr) == 0)
121 			return (hi->hi_flags);
122 	}
123 
124 	/* delete default value for this header */
125 	for (hp = &CurEnv->e_header; (h = *hp) != NULL; hp = &h->h_link)
126 	{
127 		if (strcmp(fname, h->h_field) == 0 &&
128 		    bitset(H_DEFAULT, h->h_flags) &&
129 		    !bitset(H_FORCE, h->h_flags))
130 			h->h_value = NULL;
131 	}
132 
133 	/* create a new node */
134 	h = (HDR *) xalloc(sizeof *h);
135 	h->h_field = newstr(fname);
136 	h->h_value = NULL;
137 	h->h_link = NULL;
138 	bcopy((char *) mopts, (char *) h->h_mflags, sizeof mopts);
139 	*hp = h;
140 	h->h_flags = hi->hi_flags;
141 	if (def)
142 		h->h_flags |= H_DEFAULT;
143 	if (cond)
144 		h->h_flags |= H_CHECK;
145 	if (h->h_value != NULL)
146 		free((char *) h->h_value);
147 	h->h_value = newstr(fvalue);
148 
149 	/* hack to see if this is a new format message */
150 	if (!def && bitset(H_RCPT|H_FROM, h->h_flags) &&
151 	    (index(fvalue, ',') != NULL || index(fvalue, '(') != NULL ||
152 	     index(fvalue, '<') != NULL || index(fvalue, ';') != NULL))
153 	{
154 		CurEnv->e_flags &= ~EF_OLDSTYLE;
155 	}
156 
157 	return (h->h_flags);
158 }
159 /*
160 **  ADDHEADER -- add a header entry to the end of the queue.
161 **
162 **	This bypasses the special checking of chompheader.
163 **
164 **	Parameters:
165 **		field -- the name of the header field.
166 **		value -- the value of the field.  It must be lower-cased.
167 **		e -- the envelope to add them to.
168 **
169 **	Returns:
170 **		none.
171 **
172 **	Side Effects:
173 **		adds the field on the list of headers for this envelope.
174 */
175 
176 addheader(field, value, e)
177 	char *field;
178 	char *value;
179 	ENVELOPE *e;
180 {
181 	register HDR *h;
182 	register struct hdrinfo *hi;
183 	HDR **hp;
184 
185 	/* find info struct */
186 	for (hi = HdrInfo; hi->hi_field != NULL; hi++)
187 	{
188 		if (strcmp(field, hi->hi_field) == 0)
189 			break;
190 	}
191 
192 	/* find current place in list -- keep back pointer? */
193 	for (hp = &e->e_header; (h = *hp) != NULL; hp = &h->h_link)
194 	{
195 		if (strcmp(field, h->h_field) == 0)
196 			break;
197 	}
198 
199 	/* allocate space for new header */
200 	h = (HDR *) xalloc(sizeof *h);
201 	h->h_field = field;
202 	h->h_value = newstr(value);
203 	h->h_link = *hp;
204 	h->h_flags = hi->hi_flags | H_DEFAULT;
205 	clrbitmap(h->h_mflags);
206 	*hp = h;
207 }
208 /*
209 **  HVALUE -- return value of a header.
210 **
211 **	Only "real" fields (i.e., ones that have not been supplied
212 **	as a default) are used.
213 **
214 **	Parameters:
215 **		field -- the field name.
216 **
217 **	Returns:
218 **		pointer to the value part.
219 **		NULL if not found.
220 **
221 **	Side Effects:
222 **		none.
223 */
224 
225 char *
226 hvalue(field)
227 	char *field;
228 {
229 	register HDR *h;
230 
231 	for (h = CurEnv->e_header; h != NULL; h = h->h_link)
232 	{
233 		if (!bitset(H_DEFAULT, h->h_flags) && strcmp(h->h_field, field) == 0)
234 			return (h->h_value);
235 	}
236 	return (NULL);
237 }
238 /*
239 **  ISHEADER -- predicate telling if argument is a header.
240 **
241 **	A line is a header if it has a single word followed by
242 **	optional white space followed by a colon.
243 **
244 **	Parameters:
245 **		s -- string to check for possible headerness.
246 **
247 **	Returns:
248 **		TRUE if s is a header.
249 **		FALSE otherwise.
250 **
251 **	Side Effects:
252 **		none.
253 */
254 
255 bool
256 isheader(s)
257 	register char *s;
258 {
259 	while (*s > ' ' && *s != ':' && *s != '\0')
260 		s++;
261 
262 	/* following technically violates RFC822 */
263 	while (isspace(*s))
264 		s++;
265 
266 	return (*s == ':');
267 }
268 /*
269 **  EATHEADER -- run through the stored header and extract info.
270 **
271 **	Parameters:
272 **		e -- the envelope to process.
273 **
274 **	Returns:
275 **		none.
276 **
277 **	Side Effects:
278 **		Sets a bunch of global variables from information
279 **			in the collected header.
280 **		Aborts the message if the hop count is exceeded.
281 */
282 
283 eatheader(e)
284 	register ENVELOPE *e;
285 {
286 	register HDR *h;
287 	register char *p;
288 	int hopcnt = 0;
289 
290 	if (tTd(32, 1))
291 		printf("----- collected header -----\n");
292 	for (h = e->e_header; h != NULL; h = h->h_link)
293 	{
294 		extern char *capitalize();
295 
296 		if (tTd(32, 1))
297 			printf("%s: %s\n", capitalize(h->h_field), h->h_value);
298 		/* count the number of times it has been processed */
299 		if (bitset(H_TRACE, h->h_flags))
300 			hopcnt++;
301 
302 		/* send to this person if we so desire */
303 		if (GrabTo && bitset(H_RCPT, h->h_flags) &&
304 		    !bitset(H_DEFAULT, h->h_flags) &&
305 		    (!bitset(EF_RESENT, CurEnv->e_flags) || bitset(H_RESENT, h->h_flags)))
306 		{
307 			sendtolist(h->h_value, (ADDRESS *) NULL, &CurEnv->e_sendqueue);
308 		}
309 
310 		/* log the message-id */
311 #ifdef LOG
312 		if (!QueueRun && LogLevel > 8 && h->h_value != NULL &&
313 		    strcmp(h->h_field, "message-id") == 0)
314 		{
315 			char buf[MAXNAME];
316 
317 			p = h->h_value;
318 			if (bitset(H_DEFAULT, h->h_flags))
319 			{
320 				expand(p, buf, &buf[sizeof buf], e);
321 				p = buf;
322 			}
323 			syslog(LOG_INFO, "%s: message-id=%s", e->e_id, p);
324 		}
325 #endif LOG
326 	}
327 	if (tTd(32, 1))
328 		printf("----------------------------\n");
329 
330 	/* store hop count */
331 	if (hopcnt > e->e_hopcount)
332 		e->e_hopcount = hopcnt;
333 
334 	/* message priority */
335 	p = hvalue("precedence");
336 	if (p != NULL)
337 		e->e_class = priencode(p);
338 	if (!QueueRun)
339 		e->e_msgpriority = e->e_msgsize
340 				 - e->e_class * WkClassFact
341 				 + e->e_nrcpts * WkRecipFact;
342 
343 	/* return receipt to */
344 	p = hvalue("return-receipt-to");
345 	if (p != NULL)
346 		e->e_receiptto = p;
347 
348 	/* errors to */
349 	p = hvalue("errors-to");
350 	if (p != NULL)
351 		sendtolist(p, (ADDRESS *) NULL, &e->e_errorqueue);
352 
353 	/* from person */
354 	if (OpMode == MD_ARPAFTP)
355 	{
356 		register struct hdrinfo *hi = HdrInfo;
357 
358 		for (p = NULL; p == NULL && hi->hi_field != NULL; hi++)
359 		{
360 			if (bitset(H_FROM, hi->hi_flags))
361 				p = hvalue(hi->hi_field);
362 		}
363 		if (p != NULL)
364 			setsender(p);
365 	}
366 
367 	/* full name of from person */
368 	p = hvalue("full-name");
369 	if (p != NULL)
370 		define('x', p, e);
371 
372 	/* date message originated */
373 	p = hvalue("posted-date");
374 	if (p == NULL)
375 		p = hvalue("date");
376 	if (p != NULL)
377 	{
378 		define('a', p, e);
379 		/* we don't have a good way to do canonical conversion ....
380 		define('d', newstr(arpatounix(p)), e);
381 		.... so we will ignore the problem for the time being */
382 	}
383 
384 	/*
385 	**  Log collection information.
386 	*/
387 
388 # ifdef LOG
389 	if (!QueueRun && LogLevel > 1)
390 	{
391 		char hbuf[100], *name = hbuf;
392 
393 		if (RealHostName == NULL)
394 			name = "local";
395 		else if (RealHostName[0] == '[')
396 			name = RealHostName;
397 		else
398 			(void)sprintf(hbuf, "%.90s (%s)",
399 			    RealHostName, inet_ntoa(RealHostAddr.sin_addr));
400 		syslog(LOG_INFO,
401 		    "%s: from=%s, size=%ld, class=%d, received from %s\n",
402 		    CurEnv->e_id, CurEnv->e_from.q_paddr, CurEnv->e_msgsize,
403 		    CurEnv->e_class, name);
404 	}
405 # endif LOG
406 }
407 /*
408 **  PRIENCODE -- encode external priority names into internal values.
409 **
410 **	Parameters:
411 **		p -- priority in ascii.
412 **
413 **	Returns:
414 **		priority as a numeric level.
415 **
416 **	Side Effects:
417 **		none.
418 */
419 
420 priencode(p)
421 	char *p;
422 {
423 	register int i;
424 
425 	for (i = 0; i < NumPriorities; i++)
426 	{
427 		if (!strcasecmp(p, Priorities[i].pri_name))
428 			return (Priorities[i].pri_val);
429 	}
430 
431 	/* unknown priority */
432 	return (0);
433 }
434 /*
435 **  CRACKADDR -- parse an address and turn it into a macro
436 **
437 **	This doesn't actually parse the address -- it just extracts
438 **	it and replaces it with "$g".  The parse is totally ad hoc
439 **	and isn't even guaranteed to leave something syntactically
440 **	identical to what it started with.  However, it does leave
441 **	something semantically identical.
442 **
443 **	The process is kind of strange.  There are a number of
444 **	interesting cases:
445 **		1.  comment <address> comment	==> comment <$g> comment
446 **		2.  address			==> address
447 **		3.  address (comment)		==> $g (comment)
448 **		4.  (comment) address		==> (comment) $g
449 **	And then there are the hard cases....
450 **		5.  add (comment) ress		==> $g (comment)
451 **		6.  comment <address (comment)>	==> comment <$g (comment)>
452 **		7.    .... etc ....
453 **
454 **	Parameters:
455 **		addr -- the address to be cracked.
456 **
457 **	Returns:
458 **		a pointer to the new version.
459 **
460 **	Side Effects:
461 **		none.
462 **
463 **	Warning:
464 **		The return value is saved in local storage and should
465 **		be copied if it is to be reused.
466 */
467 
468 char *
469 crackaddr(addr)
470 	register char *addr;
471 {
472 	register char *p;
473 	register int i;
474 	static char buf[MAXNAME];
475 	char *rhs;
476 	bool gotaddr;
477 	register char *bp;
478 
479 	if (tTd(33, 1))
480 		printf("crackaddr(%s)\n", addr);
481 
482 	(void) strcpy(buf, "");
483 	rhs = NULL;
484 
485 	/* strip leading spaces */
486 	while (*addr != '\0' && isspace(*addr))
487 		addr++;
488 
489 	/*
490 	**  See if we have anything in angle brackets.  If so, that is
491 	**  the address part, and the rest is the comment.
492 	*/
493 
494 	p = index(addr, '<');
495 	if (p != NULL)
496 	{
497 		/* copy the beginning of the addr field to the buffer */
498 		*p = '\0';
499 		(void) strcpy(buf, addr);
500 		(void) strcat(buf, "<");
501 		*p++ = '<';
502 
503 		/* skip spaces */
504 		while (isspace(*p))
505 			p++;
506 
507 		/* find the matching right angle bracket */
508 		addr = p;
509 		for (i = 0; *p != '\0'; p++)
510 		{
511 			switch (*p)
512 			{
513 			  case '<':
514 				i++;
515 				break;
516 
517 			  case '>':
518 				i--;
519 				break;
520 			}
521 			if (i < 0)
522 				break;
523 		}
524 
525 		/* p now points to the closing quote (or a null byte) */
526 		if (*p != '\0')
527 		{
528 			/* make rhs point to the extra stuff at the end */
529 			rhs = p;
530 			*p++ = '\0';
531 		}
532 	}
533 
534 	/*
535 	**  Now parse the real address part.  "addr" points to the (null
536 	**  terminated) version of what we are inerested in; rhs points
537 	**  to the extra stuff at the end of the line, if any.
538 	*/
539 
540 	p = addr;
541 
542 	/* now strip out comments */
543 	bp = &buf[strlen(buf)];
544 	gotaddr = FALSE;
545 	for (; *p != '\0'; p++)
546 	{
547 		if (*p == '(')
548 		{
549 			/* copy to matching close paren */
550 			*bp++ = *p++;
551 			for (i = 0; *p != '\0'; p++)
552 			{
553 				*bp++ = *p;
554 				switch (*p)
555 				{
556 				  case '(':
557 					i++;
558 					break;
559 
560 				  case ')':
561 					i--;
562 					break;
563 				}
564 				if (i < 0)
565 					break;
566 			}
567 			continue;
568 		}
569 
570 		/*
571 		**  If this is the first "real" character we have seen,
572 		**  then we put the "$g" in the buffer now.
573 		*/
574 
575 		if (isspace(*p))
576 			*bp++ = *p;
577 		else if (!gotaddr)
578 		{
579 			(void) strcpy(bp, "\001g");
580 			bp += 2;
581 			gotaddr = TRUE;
582 		}
583 	}
584 
585 	/* hack, hack.... strip trailing blanks */
586 	do
587 	{
588 		*bp-- = '\0';
589 	} while (isspace(*bp));
590 	bp++;
591 
592 	/* put any right hand side back on */
593 	if (rhs != NULL)
594 	{
595 		*rhs = '>';
596 		(void) strcpy(bp, rhs);
597 	}
598 
599 	if (tTd(33, 1))
600 		printf("crackaddr=>`%s'\n", buf);
601 
602 	return (buf);
603 }
604 /*
605 **  PUTHEADER -- put the header part of a message from the in-core copy
606 **
607 **	Parameters:
608 **		fp -- file to put it on.
609 **		m -- mailer to use.
610 **		e -- envelope to use.
611 **
612 **	Returns:
613 **		none.
614 **
615 **	Side Effects:
616 **		none.
617 */
618 
619 putheader(fp, m, e)
620 	register FILE *fp;
621 	register MAILER *m;
622 	register ENVELOPE *e;
623 {
624 	char buf[BUFSIZ];
625 	register HDR *h;
626 	extern char *arpadate();
627 	extern char *capitalize();
628 	char obuf[MAXLINE];
629 
630 	for (h = e->e_header; h != NULL; h = h->h_link)
631 	{
632 		register char *p;
633 		extern bool bitintersect();
634 
635 		if (bitset(H_CHECK|H_ACHECK, h->h_flags) &&
636 		    !bitintersect(h->h_mflags, m->m_flags))
637 			continue;
638 
639 		/* handle Resent-... headers specially */
640 		if (bitset(H_RESENT, h->h_flags) && !bitset(EF_RESENT, e->e_flags))
641 			continue;
642 
643 		p = h->h_value;
644 		if (bitset(H_DEFAULT, h->h_flags))
645 		{
646 			/* macro expand value if generated internally */
647 			expand(p, buf, &buf[sizeof buf], e);
648 			p = buf;
649 			if (p == NULL || *p == '\0')
650 				continue;
651 		}
652 
653 		if (bitset(H_FROM|H_RCPT, h->h_flags))
654 		{
655 			/* address field */
656 			bool oldstyle = bitset(EF_OLDSTYLE, e->e_flags);
657 
658 			if (bitset(H_FROM, h->h_flags))
659 				oldstyle = FALSE;
660 			commaize(h, p, fp, oldstyle, m);
661 		}
662 		else
663 		{
664 			/* vanilla header line */
665 			register char *nlp;
666 
667 			(void) sprintf(obuf, "%s: ", capitalize(h->h_field));
668 			while ((nlp = index(p, '\n')) != NULL)
669 			{
670 				*nlp = '\0';
671 				(void) strcat(obuf, p);
672 				*nlp = '\n';
673 				putline(obuf, fp, m);
674 				p = ++nlp;
675 				obuf[0] = '\0';
676 			}
677 			(void) strcat(obuf, p);
678 			putline(obuf, fp, m);
679 		}
680 	}
681 }
682 /*
683 **  COMMAIZE -- output a header field, making a comma-translated list.
684 **
685 **	Parameters:
686 **		h -- the header field to output.
687 **		p -- the value to put in it.
688 **		fp -- file to put it to.
689 **		oldstyle -- TRUE if this is an old style header.
690 **		m -- a pointer to the mailer descriptor.  If NULL,
691 **			don't transform the name at all.
692 **
693 **	Returns:
694 **		none.
695 **
696 **	Side Effects:
697 **		outputs "p" to file "fp".
698 */
699 
700 commaize(h, p, fp, oldstyle, m)
701 	register HDR *h;
702 	register char *p;
703 	FILE *fp;
704 	bool oldstyle;
705 	register MAILER *m;
706 {
707 	register char *obp;
708 	int opos;
709 	bool firstone = TRUE;
710 	char obuf[MAXLINE + 3];
711 
712 	/*
713 	**  Output the address list translated by the
714 	**  mailer and with commas.
715 	*/
716 
717 	if (tTd(14, 2))
718 		printf("commaize(%s: %s)\n", h->h_field, p);
719 
720 	obp = obuf;
721 	(void) sprintf(obp, "%s: ", capitalize(h->h_field));
722 	opos = strlen(h->h_field) + 2;
723 	obp += opos;
724 
725 	/*
726 	**  Run through the list of values.
727 	*/
728 
729 	while (*p != '\0')
730 	{
731 		register char *name;
732 		char savechar;
733 		extern char *remotename();
734 		extern char *DelimChar;		/* defined in prescan */
735 
736 		/*
737 		**  Find the end of the name.  New style names
738 		**  end with a comma, old style names end with
739 		**  a space character.  However, spaces do not
740 		**  necessarily delimit an old-style name -- at
741 		**  signs mean keep going.
742 		*/
743 
744 		/* find end of name */
745 		while (isspace(*p) || *p == ',')
746 			p++;
747 		name = p;
748 		for (;;)
749 		{
750 			char *oldp;
751 			char pvpbuf[PSBUFSIZE];
752 			extern bool isatword();
753 			extern char **prescan();
754 
755 			(void) prescan(p, oldstyle ? ' ' : ',', pvpbuf);
756 			p = DelimChar;
757 
758 			/* look to see if we have an at sign */
759 			oldp = p;
760 			while (*p != '\0' && isspace(*p))
761 				p++;
762 
763 			if (*p != '@' && !isatword(p))
764 			{
765 				p = oldp;
766 				break;
767 			}
768 			p += *p == '@' ? 1 : 2;
769 			while (*p != '\0' && isspace(*p))
770 				p++;
771 		}
772 		/* at the end of one complete name */
773 
774 		/* strip off trailing white space */
775 		while (p >= name && (isspace(*p) || *p == ',' || *p == '\0'))
776 			p--;
777 		if (++p == name)
778 			continue;
779 		savechar = *p;
780 		*p = '\0';
781 
782 		/* translate the name to be relative */
783 		name = remotename(name, m, bitset(H_FROM, h->h_flags), FALSE);
784 		if (*name == '\0')
785 		{
786 			*p = savechar;
787 			continue;
788 		}
789 
790 		/* output the name with nice formatting */
791 		opos += qstrlen(name);
792 		if (!firstone)
793 			opos += 2;
794 		if (opos > 78 && !firstone)
795 		{
796 			(void) strcpy(obp, ",\n");
797 			putline(obuf, fp, m);
798 			obp = obuf;
799 			(void) sprintf(obp, "        ");
800 			opos = strlen(obp);
801 			obp += opos;
802 			opos += qstrlen(name);
803 		}
804 		else if (!firstone)
805 		{
806 			(void) sprintf(obp, ", ");
807 			obp += 2;
808 		}
809 
810 		/* strip off quote bits as we output */
811 		while (*name != '\0' && obp < &obuf[MAXLINE])
812 		{
813 			if (bitset(0200, *name))
814 				*obp++ = '\\';
815 			*obp++ = *name++ & ~0200;
816 		}
817 		firstone = FALSE;
818 		*p = savechar;
819 	}
820 	(void) strcpy(obp, "\n");
821 	putline(obuf, fp, m);
822 }
823 /*
824 **  ISATWORD -- tell if the word we are pointing to is "at".
825 **
826 **	Parameters:
827 **		p -- word to check.
828 **
829 **	Returns:
830 **		TRUE -- if p is the word at.
831 **		FALSE -- otherwise.
832 **
833 **	Side Effects:
834 **		none.
835 */
836 
837 bool
838 isatword(p)
839 	register char *p;
840 {
841 	extern char lower();
842 
843 	if (lower(p[0]) == 'a' && lower(p[1]) == 't' &&
844 	    p[2] != '\0' && isspace(p[2]))
845 		return (TRUE);
846 	return (FALSE);
847 }
848