auth-passwd.c

/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Password authentication.  This file contains the functions to check whether
 * the password is valid for the user.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 * Copyright (c) 1999 Dug Song.  All rights reserved.
 * Copyright (c) 2000 Markus Friedl.  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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 "includes.h"
RCSID("$OpenBSD: auth-passwd.c,v 1.31 2004/01/30 09:48:57 markus Exp $");

#include "packet.h"
#include "log.h"
#include "servconf.h"
#include "auth.h"
#include "auth-options.h"

extern ServerOptions options;
int sys_auth_passwd(Authctxt *, const char *);

void
disable_forwarding(void)
{
	no_port_forwarding_flag = 1;
	no_agent_forwarding_flag = 1;
	no_x11_forwarding_flag = 1;
}

/*
 * Tries to authenticate the user using password.  Returns true if
 * authentication succeeds.
 */
int
auth_password(Authctxt *authctxt, const char *password)
{
	struct passwd * pw = authctxt->pw;
	int ok = authctxt->valid;
#if defined(USE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
	static int expire_checked = 0;
#endif

#ifndef HAVE_CYGWIN
	if (pw->pw_uid == 0 && options.permit_root_login != PERMIT_YES)
		ok = 0;
#endif
	if (*password == '\0' && options.permit_empty_passwd == 0)
		return 0;

#ifdef KRB5
	if (options.kerberos_authentication == 1) {
		int ret = auth_krb5_password(authctxt, password);
		if (ret == 1 || ret == 0)
			return ret && ok;
		/* Fall back to ordinary passwd authentication. */
	}
#endif
#ifdef HAVE_CYGWIN
	if (is_winnt) {
		HANDLE hToken = cygwin_logon_user(pw, password);

		if (hToken == INVALID_HANDLE_VALUE)
			return 0;
		cygwin_set_impersonation_token(hToken);
		return ok;
	}
#endif
#ifdef USE_PAM
	if (options.use_pam)
		return (sshpam_auth_passwd(authctxt, password) && ok);
#endif
#if defined(USE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
	if (!expire_checked) {
		expire_checked = 1;
		if (auth_shadow_pwexpired(authctxt)) {
			disable_forwarding();
			authctxt->force_pwchange = 1;
		}
	}
#endif
		
	return (sys_auth_passwd(authctxt, password) && ok);
}

#ifdef BSD_AUTH
int
sys_auth_passwd(Authctxt *authctxt, const char *password)
{
	struct passwd *pw = authctxt->pw;
	auth_session_t *as;

	as = auth_usercheck(pw->pw_name, authctxt->style, "auth-ssh",
	    (char *)password);
	if (auth_getstate(as) & AUTH_PWEXPIRED) {
		auth_close(as);
		disable_forwarding();
		authctxt->force_pwchange = 1;
		return (1);
	} else {
		return (auth_close(as));
	}
}
#elif !defined(CUSTOM_SYS_AUTH_PASSWD)
int
sys_auth_passwd(Authctxt *authctxt, const char *password)
{
	struct passwd *pw = authctxt->pw;
	char *encrypted_password;

	/* Just use the supplied fake password if authctxt is invalid */
	char *pw_password = authctxt->valid ? shadow_pw(pw) : pw->pw_passwd;

	/* Check for users with no password. */
	if (strcmp(pw_password, "") == 0 && strcmp(password, "") == 0)
		return (1);

	/* Encrypt the candidate password using the proper salt. */
	encrypted_password = xcrypt(password,
	    (pw_password[0] && pw_password[1]) ? pw_password : "xx");

	/*
	 * Authentication is accepted if the encrypted passwords
	 * are identical.
	 */
	return (strcmp(encrypted_password, pw_password) == 0);
}
#endif