auth-passwd.c revision 323129 
1/* $OpenBSD: auth-passwd.c,v 1.45 2016/07/21 01:39:35 dtucker 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 * Password authentication.  This file contains the functions to check whether
7 * the password is valid for the user.
8 *
9 * As far as I am concerned, the code I have written for this software
10 * can be used freely for any purpose.  Any derived versions of this
11 * software must be clearly marked as such, and if the derived work is
12 * incompatible with the protocol description in the RFC file, it must be
13 * called by a name other than "ssh" or "Secure Shell".
14 *
15 * Copyright (c) 1999 Dug Song.  All rights reserved.
16 * Copyright (c) 2000 Markus Friedl.  All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions
20 * are met:
21 * 1. Redistributions of source code must retain the above copyright
22 *    notice, this list of conditions and the following disclaimer.
23 * 2. Redistributions in binary form must reproduce the above copyright
24 *    notice, this list of conditions and the following disclaimer in the
25 *    documentation and/or other materials provided with the distribution.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 */
38
39#include "includes.h"
40
41#include <sys/types.h>
42
43#include <pwd.h>
44#include <stdio.h>
45#include <string.h>
46#include <stdarg.h>
47
48#include "packet.h"
49#include "buffer.h"
50#include "log.h"
51#include "misc.h"
52#include "servconf.h"
53#include "key.h"
54#include "hostfile.h"
55#include "auth.h"
56#include "auth-options.h"
57
58extern Buffer loginmsg;
59extern ServerOptions options;
60
61#ifdef HAVE_LOGIN_CAP
62extern login_cap_t *lc;
63#endif
64
65
66#define DAY		(24L * 60 * 60) /* 1 day in seconds */
67#define TWO_WEEKS	(2L * 7 * DAY)	/* 2 weeks in seconds */
68
69#define MAX_PASSWORD_LEN	1024
70
71void
72disable_forwarding(void)
73{
74	no_port_forwarding_flag = 1;
75	no_agent_forwarding_flag = 1;
76	no_x11_forwarding_flag = 1;
77}
78
79/*
80 * Tries to authenticate the user using password.  Returns true if
81 * authentication succeeds.
82 */
83int
84auth_password(Authctxt *authctxt, const char *password)
85{
86	struct passwd * pw = authctxt->pw;
87	int result, ok = authctxt->valid;
88#if defined(USE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
89	static int expire_checked = 0;
90#endif
91
92	if (strlen(password) > MAX_PASSWORD_LEN)
93		return 0;
94
95#ifndef HAVE_CYGWIN
96	if (pw->pw_uid == 0 && options.permit_root_login != PERMIT_YES)
97		ok = 0;
98#endif
99	if (*password == '\0' && options.permit_empty_passwd == 0)
100		return 0;
101
102#ifdef KRB5
103	if (options.kerberos_authentication == 1) {
104		int ret = auth_krb5_password(authctxt, password);
105		if (ret == 1 || ret == 0)
106			return ret && ok;
107		/* Fall back to ordinary passwd authentication. */
108	}
109#endif
110#ifdef HAVE_CYGWIN
111	{
112		HANDLE hToken = cygwin_logon_user(pw, password);
113
114		if (hToken == INVALID_HANDLE_VALUE)
115			return 0;
116		cygwin_set_impersonation_token(hToken);
117		return ok;
118	}
119#endif
120#ifdef USE_PAM
121	if (options.use_pam)
122		return (sshpam_auth_passwd(authctxt, password) && ok);
123#endif
124#if defined(USE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
125	if (!expire_checked) {
126		expire_checked = 1;
127		if (auth_shadow_pwexpired(authctxt))
128			authctxt->force_pwchange = 1;
129	}
130#endif
131	result = sys_auth_passwd(authctxt, password);
132	if (authctxt->force_pwchange)
133		disable_forwarding();
134	return (result && ok);
135}
136
137#ifdef BSD_AUTH
138static void
139warn_expiry(Authctxt *authctxt, auth_session_t *as)
140{
141	char buf[256];
142	quad_t pwtimeleft, actimeleft, daysleft, pwwarntime, acwarntime;
143
144	pwwarntime = acwarntime = TWO_WEEKS;
145
146	pwtimeleft = auth_check_change(as);
147	actimeleft = auth_check_expire(as);
148#ifdef HAVE_LOGIN_CAP
149	if (authctxt->valid) {
150		pwwarntime = login_getcaptime(lc, "password-warn", TWO_WEEKS,
151		    TWO_WEEKS);
152		acwarntime = login_getcaptime(lc, "expire-warn", TWO_WEEKS,
153		    TWO_WEEKS);
154	}
155#endif
156	if (pwtimeleft != 0 && pwtimeleft < pwwarntime) {
157		daysleft = pwtimeleft / DAY + 1;
158		snprintf(buf, sizeof(buf),
159		    "Your password will expire in %lld day%s.\n",
160		    daysleft, daysleft == 1 ? "" : "s");
161		buffer_append(&loginmsg, buf, strlen(buf));
162	}
163	if (actimeleft != 0 && actimeleft < acwarntime) {
164		daysleft = actimeleft / DAY + 1;
165		snprintf(buf, sizeof(buf),
166		    "Your account will expire in %lld day%s.\n",
167		    daysleft, daysleft == 1 ? "" : "s");
168		buffer_append(&loginmsg, buf, strlen(buf));
169	}
170}
171
172int
173sys_auth_passwd(Authctxt *authctxt, const char *password)
174{
175	struct passwd *pw = authctxt->pw;
176	auth_session_t *as;
177	static int expire_checked = 0;
178
179	as = auth_usercheck(pw->pw_name, authctxt->style, "auth-ssh",
180	    (char *)password);
181	if (as == NULL)
182		return (0);
183	if (auth_getstate(as) & AUTH_PWEXPIRED) {
184		auth_close(as);
185		disable_forwarding();
186		authctxt->force_pwchange = 1;
187		return (1);
188	} else {
189		if (!expire_checked) {
190			expire_checked = 1;
191			warn_expiry(authctxt, as);
192		}
193		return (auth_close(as));
194	}
195}
196#elif !defined(CUSTOM_SYS_AUTH_PASSWD)
197int
198sys_auth_passwd(Authctxt *authctxt, const char *password)
199{
200	struct passwd *pw = authctxt->pw;
201	char *encrypted_password, *salt = NULL;
202
203	/* Just use the supplied fake password if authctxt is invalid */
204	char *pw_password = authctxt->valid ? shadow_pw(pw) : pw->pw_passwd;
205
206	/* Check for users with no password. */
207	if (strcmp(pw_password, "") == 0 && strcmp(password, "") == 0)
208		return (1);
209
210	/*
211	 * Encrypt the candidate password using the proper salt, or pass a
212	 * NULL and let xcrypt pick one.
213	 */
214	if (authctxt->valid && pw_password[0] && pw_password[1])
215		salt = pw_password;
216	encrypted_password = xcrypt(password, salt);
217
218	/*
219	 * Authentication is accepted if the encrypted passwords
220	 * are identical.
221	 */
222	return encrypted_password != NULL &&
223	    strcmp(encrypted_password, pw_password) == 0;
224}
225#endif
226