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1/* $OpenBSD: sshlogin.c,v 1.37 2026/02/16 23:47:06 jsg Exp $ */
2/*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
6 * This file performs some of the things login(1) normally does. We cannot
7 * easily use something like login -p -h host -f user, because there are
8 * several different logins around, and it is hard to determined what kind of
9 * login the current system has. Also, we want to be able to execute commands
10 * on a tty.
11 *
12 * As far as I am concerned, the code I have written for this software
13 * can be used freely for any purpose. Any derived versions of this
14 * software must be clearly marked as such, and if the derived work is
15 * incompatible with the protocol description in the RFC file, it must be
16 * called by a name other than "ssh" or "Secure Shell".
17 *
18 * Copyright (c) 1999 Theo de Raadt. All rights reserved.
19 * Copyright (c) 1999 Markus Friedl. All rights reserved.
20 *
21 * Redistribution and use in source and binary forms, with or without
22 * modification, are permitted provided that the following conditions
23 * are met:
24 * 1. Redistributions of source code must retain the above copyright
25 * notice, this list of conditions and the following disclaimer.
26 * 2. Redistributions in binary form must reproduce the above copyright
27 * notice, this list of conditions and the following disclaimer in the
28 * documentation and/or other materials provided with the distribution.
29 *
30 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
31 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
33 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
34 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
35 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
39 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
40 */
41
42#include <sys/types.h>
43#include <sys/socket.h>
44
45#include <errno.h>
46#include <fcntl.h>
47#include <stdarg.h>
48#include <stdio.h>
49#include <stdlib.h>
50#include <string.h>
51#include <time.h>
52#include <unistd.h>
53#include <util.h>
54#include <utmp.h>
55#include <limits.h>
56
57#include "sshlogin.h"
58#include "ssherr.h"
59#include "log.h"
60#include "sshbuf.h"
61#include "misc.h"
62#include "servconf.h"
63
64extern struct sshbuf *loginmsg;
65extern ServerOptions options;
66
67/*
68 * Returns the time when the user last logged in. Returns 0 if the
69 * information is not available. This must be called before record_login.
70 * The host the user logged in from will be returned in buf.
71 */
72time_t
73get_last_login_time(uid_t uid, const char *logname,
74 char *buf, size_t bufsize)
75{
76 struct lastlog ll;
77 char *lastlog;
78 int fd;
79 off_t pos, r;
80
81 lastlog = _PATH_LASTLOG;
82 buf[0] = '\0';
83
84 fd = open(lastlog, O_RDONLY);
85 if (fd == -1)
86 return 0;
87
88 pos = (off_t)uid * sizeof(ll);
89 r = lseek(fd, pos, SEEK_SET);
90 if (r == -1) {
91 error_f("lseek: %s", strerror(errno));
92 close(fd);
93 return (0);
94 }
95 if (r != pos) {
96 debug_f("truncated lastlog");
97 close(fd);
98 return (0);
99 }
100 if (read(fd, &ll, sizeof(ll)) != sizeof(ll)) {
101 close(fd);
102 return 0;
103 }
104 close(fd);
105 if (bufsize > sizeof(ll.ll_host) + 1)
106 bufsize = sizeof(ll.ll_host) + 1;
107 strncpy(buf, ll.ll_host, bufsize - 1);
108 buf[bufsize - 1] = '\0';
109 return (time_t)ll.ll_time;
110}
111
112/*
113 * Generate and store last login message. This must be done before
114 * login_login() is called and lastlog is updated.
115 */
116static void
117store_lastlog_message(const char *user, uid_t uid)
118{
119 char *time_string, hostname[HOST_NAME_MAX+1] = "";
120 time_t last_login_time;
121 int r;
122
123 if (!options.print_lastlog)
124 return;
125
126 last_login_time = get_last_login_time(uid, user, hostname,
127 sizeof(hostname));
128
129 if (last_login_time != 0) {
130 time_string = ctime(&last_login_time);
131 time_string[strcspn(time_string, "\n")] = '\0';
132 if (strcmp(hostname, "") == 0)
133 r = sshbuf_putf(loginmsg, "Last login: %s\r\n",
134 time_string);
135 else
136 r = sshbuf_putf(loginmsg, "Last login: %s from %s\r\n",
137 time_string, hostname);
138 if (r != 0)
139 fatal_fr(r, "sshbuf_putf");
140 }
141}
142
143/*
144 * Records that the user has logged in. I wish these parts of operating
145 * systems were more standardized.
146 */
147void
148record_login(pid_t pid, const char *tty, const char *user, uid_t uid,
149 const char *host, struct sockaddr *addr, socklen_t addrlen)
150{
151 int fd;
152 struct lastlog ll;
153 char *lastlog;
154 struct utmp u;
155
156 /* save previous login details before writing new */
157 store_lastlog_message(user, uid);
158
159 /* Construct an utmp/wtmp entry. */
160 memset(&u, 0, sizeof(u));
161 strncpy(u.ut_line, tty + 5, sizeof(u.ut_line));
162 u.ut_time = time(NULL);
163 strncpy(u.ut_name, user, sizeof(u.ut_name));
164 strncpy(u.ut_host, host, sizeof(u.ut_host));
165
166 login(&u);
167 lastlog = _PATH_LASTLOG;
168
169 /* Update lastlog unless actually recording a logout. */
170 if (strcmp(user, "") != 0) {
171 /*
172 * It is safer to memset the lastlog structure first because
173 * some systems might have some extra fields in it (e.g. SGI)
174 */
175 memset(&ll, 0, sizeof(ll));
176
177 /* Update lastlog. */
178 ll.ll_time = time(NULL);
179 strncpy(ll.ll_line, tty + 5, sizeof(ll.ll_line));
180 strncpy(ll.ll_host, host, sizeof(ll.ll_host));
181 fd = open(lastlog, O_RDWR);
182 if (fd >= 0) {
183 lseek(fd, (off_t)uid * sizeof(ll), SEEK_SET);
184 if (write(fd, &ll, sizeof(ll)) != sizeof(ll))
185 logit("Could not write %.100s: %.100s", lastlog, strerror(errno));
186 close(fd);
187 }
188 }
189}
190
191/* Records that the user has logged out. */
192void
193record_logout(pid_t pid, const char *tty)
194{
195 const char *line = tty + 5; /* /dev/ttyq8 -> ttyq8 */
196 if (logout(line))
197 logwtmp(line, "", "");
198}