path: root/libexec/mail.local/mail.local.c

/*-
 * Copyright (c) 1990 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. 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.
 */

#ifndef lint
char copyright[] =
"@(#) Copyright (c) 1990 The Regents of the University of California.\n\
 All rights reserved.\n";
#endif /* not lint */

#ifndef lint
/*static char sccsid[] = "from: @(#)mail.local.c	5.6 (Berkeley) 6/19/91";*/
static char rcsid[] = "$Id: mail.local.c,v 1.16 1997/07/25 19:41:18 mickey Exp $";
#endif /* not lint */

#include <sys/param.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/signal.h>
#include <syslog.h>
#include <fcntl.h>
#include <netdb.h>
#include <pwd.h>
#include <time.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "pathnames.h"

#define	FATAL		1
#define	NOTFATAL	0

int	deliver __P((int, char *, int));
void	err __P((int, const char *, ...));
void	notifybiff __P((char *));
int	store __P((char *));
void	usage __P((void));
int	dohold __P((void));
int	getlock __P((char *, struct passwd *));
void	rellock __P((void));

int
main(argc, argv)
	int argc;
	char **argv;
{
	extern int optind;
	extern char *optarg;
	struct passwd *pw;
	int ch, fd, eval, lockfile=1, holdme=0;
	uid_t uid;
	char *from;

	openlog("mail.local", LOG_PERROR, LOG_MAIL);

	from = NULL;
	while ((ch = getopt(argc, argv, "lLdf:r:H")) != -1)
		switch(ch) {
		case 'd':		/* backward compatible */
			break;
		case 'f':
		case 'r':		/* backward compatible */
			if (from)
			    err(FATAL, "multiple -f options");
			from = optarg;
			break;
		case 'l':
			lockfile=1;
			break;
		case 'L':
			lockfile=0;
			break;
		case 'H':
			holdme=1;
			break;
		case '?':
		default:
			usage();
		}
	argc -= optind;
	argv += optind;

	if (!*argv && !holdme)
		usage();

	if (holdme)
		exit(dohold());

	/*
	 * If from not specified, use the name from getlogin() if the
	 * uid matches, otherwise, use the name from the password file
	 * corresponding to the uid.
	 */
	uid = getuid();
	if (!from && (!(from = getlogin()) ||
	    !(pw = getpwnam(from)) || pw->pw_uid != uid))
		from = (pw = getpwuid(uid)) ? pw->pw_name : "???";

	fd = store(from);
	for (eval = 0; *argv; ++argv)
		eval |= deliver(fd, *argv, lockfile);
	exit(eval);
}

void
unhold()
{
	rellock();
	exit(0);
}

int
dohold()
{
	struct passwd *pw;
	char *from, c;
	int holdfd;

	signal(SIGTERM, unhold);
	signal(SIGINT, unhold);
	signal(SIGHUP, unhold);

	from = getlogin();
	if (from) {
		pw = getpwnam(from);
		if (pw == NULL)
			return (1);
	} else {
		pw = getpwuid(getuid());
		if (pw)
			from = pw->pw_name;
		else
			return (1);
	}

	holdfd = getlock(from, pw);
	if (holdfd == -1) {
		write(STDOUT_FILENO, "0\n", 2);
		return (1);
	}
	write(STDOUT_FILENO, "1\n", 2);

	while (read(0, &c, 1) == -1 && errno == EINTR)
		;
	rellock();
	return (0);
}

int
store(from)
	char *from;
{
	FILE *fp;
	time_t tval;
	int fd, eline;
	char *tn, line[2048];

	if ((tn = strdup(_PATH_LOCTMP)) == NULL)
		err(FATAL, "unable to allocate memory");
	if ((fd = mkstemp(tn)) == -1 || !(fp = fdopen(fd, "w+")))
		err(FATAL, "unable to open temporary file");
	(void)unlink(tn);
	free(tn);

	(void)time(&tval);
	(void)fprintf(fp, "From %s %s", from, ctime(&tval));

	line[0] = '\0';
	for (eline = 1; fgets(line, sizeof(line), stdin);) {
		if (line[0] == '\n')
			eline = 1;
		else {
			if (eline && line[0] == 'F' && !bcmp(line, "From ", 5))
				(void)putc('>', fp);
			eline = 0;
		}
		(void)fprintf(fp, "%s", line);
		if (ferror(fp))
			break;
	}

	/* If message not newline terminated, need an extra. */
	if (!strchr(line, '\n'))
		(void)putc('\n', fp);
	/* Output a newline; note, empty messages are allowed. */
	(void)putc('\n', fp);

	(void)fflush(fp);
	if (ferror(fp))
		err(FATAL, "temporary file write error");
	return(fd);
}

void
baditem(path)
	char *path;
{
	char npath[MAXPATHLEN];

	if (unlink(path) == 0)
		return;
	snprintf(npath, sizeof npath, "%s/mailXXXXXXXXXX", _PATH_MAILDIR);
	if (mktemp(npath) == NULL)
		return;
	if (rename(path, npath) != -1)
		err(NOTFATAL, "nasty spool item %s renamed to %s",
		    path, npath);
	/* XXX if we fail to rename, another attempt will happen later */
}

char lpath[MAXPATHLEN];

void
rellock()
{
	if (lpath[0])
		unlink(lpath);
}

int
getlock(name, pw)
	char *name;
	struct passwd *pw;
{
	struct stat sb, fsb;
	int lfd=-1;
	char buf[8*1024];
	int tries = 0;

	(void)snprintf(lpath, sizeof lpath, "%s/%s.lock",
	    _PATH_MAILDIR, name);

	if (stat(_PATH_MAILDIR, &sb) != -1 &&
	    (sb.st_mode & S_IWOTH) == S_IWOTH) {
		/*
		 * We have a writeable spool, deal with it as
		 * securely as possible.
		 */
		time_t ctim = -1;

		seteuid(pw->pw_uid);
		if (lstat(lpath, &sb) != -1)
			ctim = sb.st_ctime;
		while (1) {
			/*
			 * Deal with existing user.lock files
			 * or directories or symbolic links that
			 * should not be here.
			 */
			if (readlink(lpath, buf, sizeof buf) != -1) {
				if (lstat(lpath, &sb) != -1 &&
				    S_ISLNK(fsb.st_mode)) {
					seteuid(sb.st_uid);
					unlink(lpath);
					seteuid(pw->pw_uid);
				}
				goto again;
			}
			if ((lfd = open(lpath, O_CREAT|O_WRONLY|O_EXCL|O_EXLOCK,
			    S_IRUSR|S_IWUSR)) != -1)
				break;
again:
			if (tries > 10) {
				err(NOTFATAL, "%s: %s", lpath,
				    strerror(errno));
				seteuid(0);
				return(-1);
			}
			if (tries > 9 &&
			    (lfd = open(lpath, O_WRONLY|O_EXLOCK, 0)) != -1) {
				if (fstat(lfd, &fsb) != -1 &&
				    lstat(lpath, &sb) != -1) {
					if (fsb.st_dev == sb.st_dev &&
					    fsb.st_ino == sb.st_ino &&
					    ctim == fsb.st_ctime ) {
						seteuid(fsb.st_uid);
						baditem(lpath);
						seteuid(pw->pw_uid);
					}
				}
			}
			sleep(1 << tries);
			tries++;
			continue;
		}
		seteuid(0);
	} else {
		/*
		 * Only root can write the spool directory.
		 */
		while (1) {
			if ((lfd = open(lpath, O_CREAT|O_WRONLY|O_EXCL,
			    S_IRUSR|S_IWUSR)) != -1)
				break;
			if (tries > 9) {
				err(NOTFATAL, "%s: %s", lpath, strerror(errno));
				return(-1);
			}
			sleep(1 << tries);
			tries++;
		}
	}
	return (lfd);
}

int
deliver(fd, name, lockfile)
	int fd;
	char *name;
	int lockfile;
{
	struct stat sb, fsb;
	struct passwd *pw;
	int mbfd=-1, nr, nw, off, rval=1, lfd=-1;
	char biffmsg[100], buf[8*1024], path[MAXPATHLEN];
	off_t curoff;

	/*
	 * Disallow delivery to unknown names -- special mailboxes can be
	 * handled in the sendmail aliases file.
	 */
	if (!(pw = getpwnam(name))) {
		err(NOTFATAL, "unknown name: %s", name);
		return(1);
	}

	(void)snprintf(path, sizeof path, "%s/%s", _PATH_MAILDIR, name);

	if (lockfile) {
		lfd = getlock(name, pw);
		if (lfd == -1)
			return (1);
	}

	/* after this point, always exit via bad to remove lockfile */
retry:
	if (lstat(path, &sb)) {
		if (errno != ENOENT) {
			err(NOTFATAL, "%s: %s", path, strerror(errno));
			goto bad;
		}
		if ((mbfd = open(path, O_APPEND|O_CREAT|O_EXCL|O_WRONLY|O_EXLOCK,
		     S_IRUSR|S_IWUSR)) < 0) {
			if (errno == EEXIST) {
				/* file appeared since lstat */
				goto retry;
			} else {
				err(NOTFATAL, "%s: %s", path, strerror(errno));
				goto bad;
			}
		}
		/*
		 * Set the owner and group.  Historically, binmail repeated
		 * this at each mail delivery.  We no longer do this, assuming
		 * that if the ownership or permissions were changed there
		 * was a reason for doing so.
		 */
		if (fchown(mbfd, pw->pw_uid, pw->pw_gid) < 0) {
			err(NOTFATAL, "chown %u:%u: %s",
			    pw->pw_uid, pw->pw_gid, name);
			goto bad;
		}
	} else {
		if (sb.st_nlink != 1 || S_ISLNK(sb.st_mode)) {
			err(NOTFATAL, "%s: linked file", path);
			goto bad;
		}
		if ((mbfd = open(path, O_APPEND|O_WRONLY|O_EXLOCK,
		    S_IRUSR|S_IWUSR)) < 0) {
			err(NOTFATAL, "%s: %s", path, strerror(errno));
			goto bad;
		}
		if (fstat(mbfd, &fsb)) {
			/* relating error to path may be bad style */
			err(NOTFATAL, "%s: %s", path, strerror(errno));
			goto bad;
		}
		if (sb.st_dev != fsb.st_dev || sb.st_ino != fsb.st_ino) {
			err(NOTFATAL, "%s: changed after open", path);
			goto bad;
		}
		/* paranoia? */
		if (fsb.st_nlink != 1 || S_ISLNK(fsb.st_mode)) {
			err(NOTFATAL, "%s: linked file", path);
			goto bad;
		}
	}

	curoff = lseek(mbfd, 0, SEEK_END);
	(void)snprintf(biffmsg, sizeof biffmsg, "%s@%qd\n", name, curoff);
	if (lseek(fd, 0, SEEK_SET) == (off_t)-1) {
		err(FATAL, "temporary file: %s", strerror(errno));
		goto bad;
	}

	while ((nr = read(fd, buf, sizeof(buf))) > 0)
		for (off = 0; off < nr;  off += nw)
			if ((nw = write(mbfd, buf + off, nr - off)) < 0) {
				err(NOTFATAL, "%s: %s", path, strerror(errno));
				(void)ftruncate(mbfd, curoff);
				goto bad;
			}

	if (nr == 0) {
		rval = 0;
	} else {
		err(FATAL, "temporary file: %s", strerror(errno));
		(void)ftruncate(mbfd, curoff);
	}

bad:
	if (lfd != -1) {
		rellock();
		close(lfd);
	}

	if (mbfd != -1) {
		(void)fsync(mbfd);		/* Don't wait for update. */
		(void)close(mbfd);		/* Implicit unlock. */
	}

	if (!rval)
		notifybiff(biffmsg);
	return(rval);
}

void
notifybiff(msg)
	char *msg;
{
	static struct sockaddr_in addr;
	static int f = -1;
	struct hostent *hp;
	struct servent *sp;
	int len;

	if (!addr.sin_family) {
		/* Be silent if biff service not available. */
		if (!(sp = getservbyname("biff", "udp")))
			return;
		if (!(hp = gethostbyname("localhost"))) {
			err(NOTFATAL, "localhost: %s", strerror(errno));
			return;
		}
		addr.sin_len = sizeof(struct sockaddr_in);
		addr.sin_family = hp->h_addrtype;
		addr.sin_port = sp->s_port;
		bcopy(hp->h_addr, &addr.sin_addr, hp->h_length);
	}
	if (f < 0 && (f = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
		err(NOTFATAL, "socket: %s", strerror(errno));
		return;
	}
	len = strlen(msg) + 1;
	if (sendto(f, msg, len, 0, (struct sockaddr *)&addr, sizeof(addr))
	    != len)
		err(NOTFATAL, "sendto biff: %s", strerror(errno));
}

void
usage()
{
	err(FATAL, "usage: mail.local [-lLH] [-f from] user ...");
}

#ifdef __STDC__
#include <stdarg.h>
#else
#include <varargs.h>
#endif

void
#ifdef __STDC__
err(int isfatal, const char *fmt, ...)
#else
err(isfatal, fmt)
	int isfatal;
	char *fmt;
	va_dcl
#endif
{
	va_list ap;
#ifdef __STDC__
	va_start(ap, fmt);
#else
	va_start(ap);
#endif
	vsyslog(LOG_ERR, fmt, ap);
	va_end(ap);
	if (isfatal)
		exit(1);
}