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rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable).  these days, people use source.  these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

/*	$OpenBSD: vacation.c,v 1.32 2009/10/27 23:59:46 deraadt Exp $	*/
/*	$NetBSD: vacation.c,v 1.7 1995/04/29 05:58:27 cgd Exp $	*/

/*
 * Copyright (c) 1983, 1987, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
**  Vacation
**  Copyright (c) 1983  Eric P. Allman
**  Berkeley, California
*/

#include <sys/param.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <pwd.h>
#include <db.h>
#include <time.h>
#include <syslog.h>
#include <tzfile.h>
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <paths.h>

/*
 *  VACATION -- return a message to the sender when on vacation.
 *
 *	This program is invoked as a message receiver.  It returns a
 *	message specified by the user to whomever sent the mail, taking
 *	care not to return a message too often to prevent "I am on
 *	vacation" loops.
 */

#define	MAXLINE	1024			/* max line from mail header */
#define	VDB	".vacation.db"		/* dbm's database */
#define	VMSG	".vacation.msg"		/* vacation message */

typedef struct alias {
	struct alias *next;
	char *name;
} ALIAS;
ALIAS *names;

DB *db;
char from[MAXLINE];
char subj[MAXLINE];

int junkmail(void);
int nsearch(char *, char *);
void readheaders(void);
int recent(void);
void sendmessage(char *);
void setinterval(time_t);
void setreply(void);
void usage(void);

int
main(int argc, char *argv[])
{
	int ch, iflag, flags;
	struct passwd *pw;
	time_t interval;
	struct stat sb;
	ALIAS *cur;

	opterr = iflag = 0;
	interval = -1;
	while ((ch = getopt(argc, argv, "a:Iir:")) != -1)
		switch ((char)ch) {
		case 'a':			/* alias */
			if (!(cur = (ALIAS *)malloc((u_int)sizeof(ALIAS))))
				break;
			cur->name = optarg;
			cur->next = names;
			names = cur;
			break;
		case 'I':			/* backward compatible */
		case 'i':			/* init the database */
			iflag = 1;
			break;
		case 'r':
			if (isdigit(*optarg)) {
				interval = atol(optarg) * SECSPERDAY;
				if (interval < 0)
					usage();
			} else
				interval = (time_t)LONG_MAX;	/* XXX */
			break;
		default:
			usage();
		}
	argc -= optind;
	argv += optind;

	if (argc != 1) {
		if (!iflag)
			usage();
		if (!(pw = getpwuid(getuid()))) {
			syslog(LOG_ERR,
			    "no such user uid %u.", getuid());
			exit(1);
		}
	} else if (!(pw = getpwnam(*argv))) {
		syslog(LOG_ERR, "no such user %s.", *argv);
		exit(1);
	}
	if (chdir(pw->pw_dir)) {
		syslog(LOG_NOTICE,
		    "no such directory %s.", pw->pw_dir);
		exit(1);
	}

	/*
	 * dbopen(3) can not deal with a zero-length file w/o O_TRUNC.
	 */
	if (iflag == 1 || (stat(VDB, &sb) == 0 && sb.st_size == (off_t)0))
		flags = O_CREAT|O_RDWR|O_TRUNC;
	else
		flags = O_CREAT|O_RDWR;

	db = dbopen(VDB, flags, S_IRUSR|S_IWUSR, DB_HASH, NULL);
	if (!db) {
		syslog(LOG_NOTICE, "%s: %m", VDB);
		exit(1);
	}

	if (interval != -1)
		setinterval(interval);

	if (iflag) {
		(void)(db->close)(db);
		exit(0);
	}

	if (!(cur = malloc((u_int)sizeof(ALIAS))))
		exit(1);
	cur->name = pw->pw_name;
	cur->next = names;
	names = cur;

	readheaders();
	if (!recent()) {
		setreply();
		(void)(db->close)(db);
		sendmessage(pw->pw_name);
	} else
		(void)(db->close)(db);
	exit(0);
	/* NOTREACHED */
}

/*
 * readheaders --
 *	read mail headers
 */
void
readheaders(void)
{
	char buf[MAXLINE], *p;
	int tome, cont;
	ALIAS *cur;

	cont = tome = 0;
	while (fgets(buf, sizeof(buf), stdin) && *buf != '\n')
		switch (*buf) {
		case 'A':		/* "Auto-Submitted:" */
		case 'a':
			cont = 0;
			if (strncasecmp(buf, "Auto-Submitted:", 15))
				break;
			for (p = buf + 15; isspace(*p); ++p)
				;
			/*
			 * RFC 3834 section 2:
			 * Automatic responses SHOULD NOT be issued in response
			 * to any message which contains an Auto-Submitted
			 * header where the field has any value other than "no".
			 */
			if ((p[0] == 'n' || p[0] == 'N') &&
			    (p[1] == 'o' || p[1] == 'O')) {
				for (p += 2; isspace(*p); ++p)
					;
				if (*p == '\0')
					break;	/* Auto-Submitted: no */
			}
			exit(0);
		case 'F':		/* "From " */
		case 'f':
			cont = 0;
			if (!strncasecmp(buf, "From ", 5)) {
				for (p = buf + 5; *p && *p != ' '; ++p)
					;
				*p = '\0';
				(void)strlcpy(from, buf + 5, sizeof(from));
				from[strcspn(from, "\n")] = '\0';
				if (junkmail())
					exit(0);
			}
			break;
		case 'L':		/* "List-Id:" */
		case 'l':
			cont = 0;
			/*
			 * If present (with any value), message is coming from a
			 * mailing list, cf. RFC2919.
			 */
			if (strncasecmp(buf, "List-Id:", 8) == 0)
				exit(0);
			break;
		case 'R':		/* "Return-Path:" */
		case 'r':
			cont = 0;
			if (strncasecmp(buf, "Return-Path:",
			    sizeof("Return-Path:")-1) ||
			    (buf[12] != ' ' && buf[12] != '\t'))
				break;
			for (p = buf + 12; isspace(*p); ++p)
				;
			if (strlcpy(from, p, sizeof(from)) >= sizeof(from)) {
				syslog(LOG_NOTICE,
				    "Return-Path %s exceeds limits", p);
				exit(1);
			}
			from[strcspn(from, "\n")] = '\0';
			if (junkmail())
				exit(0);
			break;
		case 'P':		/* "Precedence:" */
		case 'p':
			cont = 0;
			if (strncasecmp(buf, "Precedence:", 11))
				break;
			for (p = buf + 11; isspace(*p); ++p)
				;
			if (!strncasecmp(p, "junk", 4) ||
			    !strncasecmp(p, "bulk", 4) ||
			    !strncasecmp(p, "list", 4))
				exit(0);
			break;
		case 'S':		/* Subject: */
		case 's':
			cont = 0;
			if (strncasecmp(buf, "Subject:",
			    sizeof("Subject:")-1) ||
			    (buf[8] != ' ' && buf[8] != '\t'))
				break;
			for (p = buf + 8; isspace(*p); ++p)
				;
			if (strlcpy(subj, p, sizeof(subj)) >= sizeof(subj)) {
				syslog(LOG_NOTICE,
				    "Subject %s exceeds limits", p);
				exit(1);
			}
			subj[strcspn(subj, "\n")] = '\0';
			break;
		case 'C':		/* "Cc:" */
		case 'c':
			if (strncasecmp(buf, "Cc:", 3))
				break;
			cont = 1;
			goto findme;
		case 'T':		/* "To:" */
		case 't':
			if (strncasecmp(buf, "To:", 3))
				break;
			cont = 1;
			goto findme;
		default:
			if (!isspace(*buf) || !cont || tome) {
				cont = 0;
				break;
			}
findme:			for (cur = names; !tome && cur; cur = cur->next)
				tome += nsearch(cur->name, buf);
		}
	if (!tome)
		exit(0);
	if (!*from) {
		syslog(LOG_NOTICE,
		    "no initial \"From\" or \"Return-Path\"line.");
		exit(1);
	}
}

/*
 * nsearch --
 *	do a nice, slow, search of a string for a substring.
 */
int
nsearch(char *name, char *str)
{
	int len;

	for (len = strlen(name); *str; ++str)
		if (!strncasecmp(name, str, len))
			return(1);
	return(0);
}

/*
 * junkmail --
 *	read the header and return if automagic/junk/bulk/list mail
 */
int
junkmail(void)
{
	static struct ignore {
		char	*name;
		int	len;
	} ignore[] = {
		{ "-request", 8 },
		{ "postmaster", 10 },
		{ "uucp", 4 },
		{ "mailer-daemon", 13 },
		{ "mailer", 6 },
		{ "-relay", 6 },
		{ NULL, 0 }
	};
	struct ignore *cur;
	int len;
	char *p;

	/*
	 * This is mildly amusing, and I'm not positive it's right; trying
	 * to find the "real" name of the sender, assuming that addresses
	 * will be some variant of:
	 *
	 * From site!site!SENDER%site.domain%site.domain@site.domain
	 */
	if (!(p = strchr(from, '%'))) {
		if (!(p = strchr(from, '@'))) {
			if ((p = strrchr(from, '!')))
				++p;
			else
				p = from;
			for (; *p; ++p)
				;
		}
	}
	len = p - from;
	for (cur = ignore; cur->name; ++cur)
		if (len >= cur->len &&
		    !strncasecmp(cur->name, p - cur->len, cur->len))
			return(1);
	return(0);
}

#define	VIT	"__VACATION__INTERVAL__TIMER__"

/*
 * recent --
 *	find out if user has gotten a vacation message recently.
 *	use bcopy for machines with alignment restrictions
 */
int
recent(void)
{
	time_t then, next;
	DBT key, data;

	/* get interval time */
	key.data = VIT;
	key.size = sizeof(VIT);
	if ((db->get)(db, &key, &data, 0))
		next = SECSPERDAY * DAYSPERWEEK;
	else
		bcopy(data.data, &next, sizeof(next));

	/* get record for this address */
	key.data = from;
	key.size = strlen(from);
	if (!(db->get)(db, &key, &data, 0)) {
		bcopy(data.data, &then, sizeof(then));
		if (next == (time_t)LONG_MAX ||			/* XXX */
		    then + next > time(NULL))
			return(1);
	}
	return(0);
}

/*
 * setinterval --
 *	store the reply interval
 */
void
setinterval(time_t interval)
{
	DBT key, data;

	key.data = VIT;
	key.size = sizeof(VIT);
	data.data = &interval;
	data.size = sizeof(interval);
	(void)(db->put)(db, &key, &data, 0);
}

/*
 * setreply --
 *	store that this user knows about the vacation.
 */
void
setreply(void)
{
	DBT key, data;
	time_t now;

	key.data = from;
	key.size = strlen(from);
	(void)time(&now);
	data.data = &now;
	data.size = sizeof(now);
	(void)(db->put)(db, &key, &data, 0);
}

/*
 * sendmessage --
 *	exec sendmail to send the vacation file to sender
 */
void
sendmessage(char *myname)
{
	char buf[MAXLINE];
	FILE *mfp, *sfp;
	int pvect[2], i;

	mfp = fopen(VMSG, "r");
	if (mfp == NULL) {
		syslog(LOG_NOTICE, "no ~%s/%s file.", myname, VMSG);
		exit(1);
	}
	if (pipe(pvect) < 0) {
		syslog(LOG_ERR, "pipe: %m");
		exit(1);
	}
	i = vfork();
	if (i < 0) {
		syslog(LOG_ERR, "fork: %m");
		exit(1);
	}
	if (i == 0) {
		dup2(pvect[0], 0);
		close(pvect[0]);
		close(pvect[1]);
		close(fileno(mfp));
		execl(_PATH_SENDMAIL, "sendmail", "-f", myname, "--",
		    from, (char *)NULL);
		syslog(LOG_ERR, "can't exec %s: %m", _PATH_SENDMAIL);
		_exit(1);
	}
	close(pvect[0]);
	sfp = fdopen(pvect[1], "w");
	if (sfp == NULL) {
		/* XXX could not fdopen; likely out of memory */
		fclose(mfp);
		close(pvect[1]);
		return;
	}
	fprintf(sfp, "To: %s\n", from);
	fputs("Auto-Submitted: auto-replied\n", sfp);
	while (fgets(buf, sizeof buf, mfp)) {
		char *s = strstr(buf, "$SUBJECT");

		if (s) {
			*s = 0;
			fputs(buf, sfp);
			fputs(subj, sfp);
			fputs(s+8, sfp);
		} else {
			fputs(buf, sfp);
		}
	}
	fclose(mfp);
	fclose(sfp);
}

void
usage(void)
{
	syslog(LOG_NOTICE, "uid %u: usage: vacation [-i] [-a alias] login",
	    getuid());
	exit(1);
}