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For open/openat, if the flags parameter does not contain O_CREAT, the
3rd (variadic) mode_t parameter is irrelevant.  Many developers in the past
have passed mode_t (0, 044, 0644, or such), which might lead future people
to copy this broken idiom, and perhaps even believe this parameter has some
meaning or implication or application. Delete them all.
This comes out of a conversation where tb@ noticed that a strange (but
intentional) pledge behaviour is to always knock-out high-bits from
mode_t on a number of system calls as a safety factor, and his bewilderment
that this appeared to be happening against valid modes (at least visually),
but no sorry, they are all irrelevant junk.  They could all be 0xdeafbeef.
ok millert

/*	$OpenBSD: last.c,v 1.54 2021/10/24 21:24:16 deraadt Exp $	*/
/*	$NetBSD: last.c,v 1.6 1994/12/24 16:49:02 cgd Exp $	*/

/*
 * Copyright (c) 1987, 1993, 1994
 *	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.
 */

#include <sys/stat.h>

#include <ctype.h>
#include <err.h>
#include <fcntl.h>
#include <libgen.h>
#include <paths.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <limits.h>
#include <utmp.h>

#define	NO	0				/* false/no */
#define	YES	1				/* true/yes */
#define ATOI2(ar)	((ar)[0] - '0') * 10 + ((ar)[1] - '0'); (ar) += 2;

static struct utmp	buf[1024];		/* utmp read buffer */

struct arg {
	char	*name;				/* argument */
#define	HOST_TYPE	-2
#define	TTY_TYPE	-3
#define	USER_TYPE	-4
	int	type;				/* type of arg */
	struct	arg *next;			/* linked list pointer */
} *arglist;

struct ttytab {
	time_t	logout;				/* log out time */
	char	tty[UT_LINESIZE + 1];		/* terminal name */
	struct	ttytab*next;			/* linked list pointer */
} *ttylist;

static time_t	currentout;			/* current logout value */
static long	maxrec = -1;			/* records to display */
static char	*file = _PATH_WTMP;		/* wtmp file */
static int	fulltime = 0;			/* Display seconds? */
static time_t	snaptime = 0;			/* report only at this time */
static int	calculate = 0;
static int	seconds = 0;

void	 addarg(int, char *);
struct ttytab	*addtty(char *);
void	 hostconv(char *);
void	 onintr(int);
char	*ttyconv(char *);
time_t	 dateconv(char *);
int	 want(struct utmp *, int);
void	 wtmp(void);
void	 checkargs(void);
void	 print_entry(const struct utmp *);
void	 usage(void);

#define NAME_WIDTH	9
#define HOST_WIDTH	24

#define SECSPERDAY	(24 * 60 * 60)

int
main(int argc, char *argv[])
{
	const char *errstr;
	int ch, lastch = '\0', newarg = 1, prevoptind = 1;

	while ((ch = getopt(argc, argv, "0123456789cf:h:n:st:d:T")) != -1) {
		switch (ch) {
		case '0': case '1': case '2': case '3': case '4':
		case '5': case '6': case '7': case '8': case '9':
			/*
			 * kludge: last was originally designed to take
			 * a number after a dash.
			 */
			if (newarg || !isdigit(lastch))
				maxrec = 0;
			else if (maxrec > INT_MAX / 10)
				usage();
			maxrec = (maxrec * 10) + (ch - '0');
			break;
		case 'c':
			calculate = 1;
			break;
		case 'f':
			file = optarg;
			break;
		case 'h':
			hostconv(optarg);
			addarg(HOST_TYPE, optarg);
			break;
		case 'n':
			maxrec = strtonum(optarg, 0, LONG_MAX, &errstr);
			if (errstr != NULL)
				errx(1, "number of lines is %s: %s", errstr,
				    optarg);
			if (maxrec == 0)
				exit(0);
			break;
		case 's':
			seconds = 1;
			break;
		case 't':
			addarg(TTY_TYPE, ttyconv(optarg));
			break;
		case 'd':
			snaptime = dateconv(optarg);
			break;
		case 'T':
			fulltime = 1;
			break;
		default:
			usage();
		}
		lastch = ch;
		newarg = optind != prevoptind;
		prevoptind = optind;
	}
	if (maxrec == 0)
		exit(0);

	if (unveil(file, "r") == -1)
		err(1, "unveil %s", file);
	if (pledge("stdio rpath", NULL) == -1)
		err(1, "pledge");

	if (argc) {
		setvbuf(stdout, NULL, _IOLBF, 0);
		for (argv += optind; *argv; ++argv) {
#define	COMPATIBILITY
#ifdef	COMPATIBILITY
			/* code to allow "last p5" to work */
			addarg(TTY_TYPE, ttyconv(*argv));
#endif
			addarg(USER_TYPE, *argv);
		}
	}

	checkargs();
	wtmp();
	exit(0);
}

/*
 * if snaptime is set, print warning if usernames, or -t or -h
 * flags are also provided
 */
void
checkargs(void)
{
	int	ttyflag = 0;
	struct arg *step;

	if (!snaptime || !arglist)
		return;

	for (step = arglist; step; step = step->next)
		switch (step->type) {
		case HOST_TYPE:
			(void)fprintf(stderr,
			    "Warning: Ignoring hostname flag\n");
			break;
		case TTY_TYPE:
			if (!ttyflag) { /* don't print this twice */
				(void)fprintf(stderr,
				    "Warning: Ignoring tty flag\n");
				ttyflag = 1;
			}
			break;
		case USER_TYPE:
			(void)fprintf(stderr,
			    "Warning: Ignoring username[s]\n");
			break;
		default:
			break;
			/* PRINT NOTHING */
		}
}

void
print_entry(const struct utmp *bp)
{
	printf("%-*.*s %-*.*s %-*.*s ",
	    NAME_WIDTH, UT_NAMESIZE, bp->ut_name,
	    UT_LINESIZE, UT_LINESIZE, bp->ut_line,
	    HOST_WIDTH, UT_HOSTSIZE, bp->ut_host);

	if (seconds)
		printf("%lld", (long long)bp->ut_time);
	else {
		struct tm *tm;

		tm = localtime(&bp->ut_time);
		if (tm == NULL) {
			/* bogus entry?  format as epoch time... */
			printf("%lld", (long long)bp->ut_time);
		} else {
			char	tim[40];

			strftime(tim, sizeof tim,
			    fulltime ? "%a %b %d %H:%M:%S" : "%a %b %d %H:%M",
			    tm);
			printf("%s", tim);
		}
	}
}


/*
 * read through the wtmp file
 */
void
wtmp(void)
{
	time_t	delta, total = 0;
	int	timesize, wfd, snapfound = 0;
	char	*ct, *crmsg = "invalid";
	struct utmp	*bp;
	struct stat	stb;
	ssize_t	bytes;
	off_t	bl;
	struct ttytab	*T;

	if ((wfd = open(file, O_RDONLY)) == -1 || fstat(wfd, &stb) == -1)
		err(1, "%s", file);
	bl = (stb.st_size + sizeof(buf) - 1) / sizeof(buf);

	if (fulltime)
		timesize = 8;	/* HH:MM:SS */
	else
		timesize = 5;	/* HH:MM */

	(void)time(&buf[0].ut_time);
	(void)signal(SIGINT, onintr);
	(void)signal(SIGQUIT, onintr);

	while (--bl >= 0) {
		if (lseek(wfd, bl * sizeof(buf), SEEK_SET) == -1 ||
		    (bytes = read(wfd, buf, sizeof(buf))) == -1)
			err(1, "%s", file);
		for (bp = &buf[bytes / sizeof(buf[0]) - 1]; bp >= buf; --bp) {
			/*
			 * if the terminal line is '~', the machine stopped.
			 * see utmp(5) for more info.
			 */
			if (bp->ut_line[0] == '~' && !bp->ut_line[1]) {
				/* everybody just logged out */
				for (T = ttylist; T; T = T->next)
					T->logout = -bp->ut_time;
				currentout = -bp->ut_time;
				crmsg = strncmp(bp->ut_name, "shutdown",
				    UT_NAMESIZE) ? "crash" : "shutdown";

				/*
				 * if we're in snapshot mode, we want to
				 * exit if this shutdown/reboot appears
				 * while we we are tracking the active
				 * range
				 */
				if (snaptime && snapfound) {
					close(wfd);
					return;
				}

				/*
				 * don't print shutdown/reboot entries
				 * unless flagged for
				 */
				if (want(bp, NO)) {
					print_entry(bp);
					printf("\n");
					if (maxrec != -1 && !--maxrec) {
						close(wfd);
						return;
					}
				}
				continue;
			}

			/*
			 * if the line is '{' or '|', date got set; see
			 * utmp(5) for more info.
			 */
			if ((bp->ut_line[0] == '{' || bp->ut_line[0] == '|') &&
			    !bp->ut_line[1]) {
				if (want(bp, NO)) {
					print_entry(bp);
					printf("\n");
					if (maxrec && !--maxrec) {
						close(wfd);
						return;
					}
				}
				continue;
			}

			/* find associated tty */
			for (T = ttylist;; T = T->next) {
				if (!T) {
					/* add new one */
					T = addtty(bp->ut_line);
					break;
				}
				if (!strncmp(T->tty, bp->ut_line, UT_LINESIZE))
					break;
			}

			/*
			 * print record if not in snapshot mode and wanted
			 * or in snapshot mode and in snapshot range
			 */
			if (bp->ut_name[0] &&
			    ((want(bp, YES)) || (bp->ut_time < snaptime &&
			    (T->logout > snaptime || !T->logout ||
			    T->logout < 0)))) {
				snapfound = 1;
				print_entry(bp);
				printf(" ");

				if (!T->logout)
					puts("  still logged in");
				else {
					if (T->logout < 0) {
						T->logout = -T->logout;
						printf("- %s", crmsg);
					} else {
						if (seconds)
							printf("- %lld",
							    (long long)T->logout);
						else
							printf("- %*.*s",
							    timesize, timesize,
							    ctime(&T->logout)+11);
					}
					delta = T->logout - bp->ut_time;
					if (seconds)
						printf("  (%lld)\n",
						    (long long)delta);
					else {
						if (delta < SECSPERDAY)
							printf("  (%*.*s)\n",
							    timesize, timesize,
							    asctime(gmtime(&delta))+11);
						else
							printf(" (%lld+%*.*s)\n",
							    (long long)delta / SECSPERDAY,
							    timesize, timesize,
							    asctime(gmtime(&delta))+11);
					}
					if (calculate)
						total += delta;
				}
				if (maxrec != -1 && !--maxrec) {
					close(wfd);
					return;
				}
			}
			T->logout = bp->ut_time;
		}
	}
	close(wfd);
	if (calculate) {
		if ((total / SECSPERDAY) > 0) {
			int days = (total / SECSPERDAY);
			total -= (days * SECSPERDAY);

			printf("\nTotal time: %d days, %*.*s\n",
			    days, timesize, timesize,
			    asctime(gmtime(&total))+11);
		} else
			printf("\nTotal time: %*.*s\n",
			    timesize, timesize,
			    asctime(gmtime(&total))+11);
	}
	ct = ctime(&buf[0].ut_time);
	printf("\n%s begins %10.10s %*.*s %4.4s\n", basename(file), ct,
	    timesize, timesize, ct + 11, ct + 20);
}

/*
 * see if want this entry
 */
int
want(struct utmp *bp, int check)
{
	struct arg *step;

	if (check) {
		/*
		 * some entries, such as ftp and uucp, will 
		 * include process name plus id; exclude entries
		 * that start with 'console' and 'tty' from
		 * having the process id stripped.
		 */
		if ((strncmp(bp->ut_line, "console", strlen("console")) != 0) &&
		    (strncmp(bp->ut_line, "tty", strlen("tty")) != 0)) {
			char *s;
			for (s = bp->ut_line;
			     *s != '\0' && !isdigit((unsigned char)*s); s++)
				;
			*s = '\0';
		}
	}

	if (snaptime)		/* if snaptime is set, return NO */
		return (NO);

	if (!arglist)
		return (YES);

	for (step = arglist; step; step = step->next)
		switch (step->type) {
		case HOST_TYPE:
			if (!strncasecmp(step->name, bp->ut_host, UT_HOSTSIZE))
				return (YES);
			break;
		case TTY_TYPE:
			if (!strncmp(step->name, bp->ut_line, UT_LINESIZE))
				return (YES);
			break;
		case USER_TYPE:
			if (!strncmp(step->name, bp->ut_name, UT_NAMESIZE))
				return (YES);
			break;
		}

	return (NO);
}

/*
 * add an entry to a linked list of arguments
 */
void
addarg(int type, char *arg)
{
	struct arg *cur;

	if (!(cur = malloc((u_int)sizeof(struct arg))))
		err(1, "malloc failure");
	cur->next = arglist;
	cur->type = type;
	cur->name = arg;
	arglist = cur;
}

/*
 * add an entry to a linked list of ttys
 */
struct ttytab *
addtty(char *ttyname)
{
	struct ttytab *cur;

	if (!(cur = malloc((u_int)sizeof(struct ttytab))))
		err(1, "malloc failure");
	cur->next = ttylist;
	cur->logout = currentout;
	memmove(cur->tty, ttyname, UT_LINESIZE);
	return (ttylist = cur);
}

/*
 * convert the hostname to search pattern; if the supplied host name
 * has a domain attached that is the same as the current domain, rip
 * off the domain suffix since that's what login(1) does.
 */
void
hostconv(char *arg)
{
	static char *hostdot, name[HOST_NAME_MAX+1];
	static int first = 1;
	char *argdot;

	if (!(argdot = strchr(arg, '.')))
		return;
	if (first) {
		first = 0;
		if (gethostname(name, sizeof(name)))
			err(1, "gethostname");
		hostdot = strchr(name, '.');
	}
	if (hostdot && !strcasecmp(hostdot, argdot))
		*argdot = '\0';
}

/*
 * convert tty to correct name.
 */
char *
ttyconv(char *arg)
{
	size_t len = 8;
	char *mval;

	/*
	 * kludge -- we assume that all tty's end with
	 * a two character suffix.
	 */
	if (strlen(arg) == 2) {
		/* either 6 for "ttyxx" or 8 for "console" */
		if (!(mval = malloc(len)))
			err(1, "malloc failure");
		if (!strcmp(arg, "co"))
			(void)strlcpy(mval, "console", len);
		else
			snprintf(mval, len, "tty%s", arg);
		return (mval);
	}
	if (!strncmp(arg, _PATH_DEV, sizeof(_PATH_DEV) - 1))
		return (arg + 5);
	return (arg);
}

/*
 * Convert the snapshot time in command line given in the format
 *	[[[CC]YY]MMDD]hhmm[.SS]] to a time_t.
 *	Derived from atime_arg1() in usr.bin/touch/touch.c
 */
time_t
dateconv(char *arg)
{
	time_t timet;
	struct tm *t;
	int yearset;
	char *p;

	/* Start with the current time. */
	if (time(&timet) == -1)
		err(1, "time");
	if ((t = localtime(&timet)) == NULL)
		err(1, "localtime");

	/* [[[CC]YY]MMDD]hhmm[.SS] */
	if ((p = strchr(arg, '.')) == NULL)
		t->tm_sec = 0;		/* Seconds defaults to 0. */
	else {
		if (strlen(p + 1) != 2)
			goto terr;
		*p++ = '\0';
		t->tm_sec = ATOI2(p);
	}

	yearset = 0;
	switch (strlen(arg)) {
	case 12:			/* CCYYMMDDhhmm */
		t->tm_year = ATOI2(arg);
		t->tm_year *= 100;
		yearset = 1;
		/* FALLTHROUGH */
	case 10:			/* YYMMDDhhmm */
		if (yearset) {
			yearset = ATOI2(arg);
			t->tm_year += yearset;
		} else {
			yearset = ATOI2(arg);
			if (yearset < 69)
				t->tm_year = yearset + 2000;
			else
				t->tm_year = yearset + 1900;
		}
		t->tm_year -= 1900;	/* Convert to UNIX time. */
		/* FALLTHROUGH */
	case 8:				/* MMDDhhmm */
		t->tm_mon = ATOI2(arg);
		--t->tm_mon;		/* Convert from 01-12 to 00-11 */
		t->tm_mday = ATOI2(arg);
		t->tm_hour = ATOI2(arg);
		t->tm_min = ATOI2(arg);
		break;
	case 4:				/* hhmm */
		t->tm_hour = ATOI2(arg);
		t->tm_min = ATOI2(arg);
		break;
	default:
		goto terr;
	}
	t->tm_isdst = -1;		/* Figure out DST. */
	timet = mktime(t);
	if (timet == -1)
terr:		errx(1, "out of range or illegal time specification: "
		    "[[[CC]YY]MMDD]hhmm[.SS]");
	return (timet);
}


/*
 * on interrupt, we inform the user how far we've gotten
 */
void
onintr(int signo)
{
	char str[1024], *ct, ctbuf[26];

	ct = ctime_r(&buf[0].ut_time, ctbuf);
	snprintf(str, sizeof str, "\ninterrupted %10.10s %8.8s \n",
	    ct, ct + 11);
	write(STDOUT_FILENO, str, strlen(str));
	if (signo == SIGINT)
		_exit(1);
}

void
usage(void)
{
	extern char *__progname;

	fprintf(stderr,
	    "usage: %s [-csT] [-d date] [-f file] [-h host]"
	    " [-n number] [-t tty] [user ...]\n", __progname);
	exit(1);
}