auth-pam.c - security/openssh-library - Rivoreo Source Code Repositories

 /*
  * Copyright (c) 2000 Damien Miller.  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"

 #ifdef USE_PAM
 #include "ssh.h"
 #include "xmalloc.h"
 #include "servconf.h"

 RCSID("$Id: auth-pam.c,v 1.19 2000/12/03 00:51:51 djm Exp $");

 #define NEW_AUTHTOK_MSG \
 	"Warning: Your password has expired, please change it now"

 /* Callbacks */
 static int pamconv(int num_msg, const struct pam_message **msg,
 	  struct pam_response **resp, void *appdata_ptr);
 void pam_cleanup_proc(void *context);
 void pam_msg_cat(const char *msg);

 /* module-local variables */
 static struct pam_conv conv = {
 	pamconv,
 	NULL
 };
 static pam_handle_t *pamh = NULL;
 static const char *pampasswd = NULL;
 static char *pam_msg = NULL;

 /* states for pamconv() */
 enum { INITIAL_LOGIN, OTHER } pamstate = INITIAL_LOGIN;
 /* remember whether pam_acct_mgmt() returned PAM_NEWAUTHTOK_REQD */
 static int password_change_required = 0;
 /* remember whether the last pam_authenticate() succeeded or not */
 static int was_authenticated = 0;

 /* accessor which allows us to switch conversation structs according to
  * the authentication method being used */
 void pam_set_conv(struct pam_conv *conv)
 {
 	pam_set_item(pamh, PAM_CONV, conv);
 }

 /* start an authentication run */
 int do_pam_authenticate(int flags)
 {
 	int retval = pam_authenticate(pamh, flags);
 	was_authenticated = (retval == PAM_SUCCESS);
 	return retval;
 }

 /*
  * PAM conversation function.
  * There are two states this can run in.
  *
  * INITIAL_LOGIN mode simply feeds the password from the client into
  * PAM in response to PAM_PROMPT_ECHO_OFF, and collects output
  * messages with pam_msg_cat().  This is used during initial
  * authentication to bypass the normal PAM password prompt.
  *
  * OTHER mode handles PAM_PROMPT_ECHO_OFF with read_passphrase(prompt, 1)
  * and outputs messages to stderr. This mode is used if pam_chauthtok()
  * is called to update expired passwords.
  */
 static int pamconv(int num_msg, const struct pam_message **msg,
 	struct pam_response **resp, void *appdata_ptr)
 {
 	struct pam_response *reply;
 	int count;
 	char buf[1024];

 	/* PAM will free this later */
 	reply = malloc(num_msg * sizeof(*reply));
 	if (reply == NULL)
 		return PAM_CONV_ERR;

 	for (count = 0; count < num_msg; count++) {
 		switch ((*msg)[count].msg_style) {
 			case PAM_PROMPT_ECHO_ON:
 				if (pamstate == INITIAL_LOGIN) {
 					free(reply);
 					return PAM_CONV_ERR;
 				} else {
 					fputs((*msg)[count].msg, stderr);
 					fgets(buf, sizeof(buf), stdin);
 					reply[count].resp = xstrdup(buf);
 					reply[count].resp_retcode = PAM_SUCCESS;
 					break;
 				}
 			case PAM_PROMPT_ECHO_OFF:
 				if (pamstate == INITIAL_LOGIN) {
 					if (pampasswd == NULL) {
 						free(reply);
 						return PAM_CONV_ERR;
 					}
 					reply[count].resp = xstrdup(pampasswd);
 				} else {
 					reply[count].resp =
 						xstrdup(read_passphrase((*msg)[count].msg, 1));
 				}
 				reply[count].resp_retcode = PAM_SUCCESS;
 				break;
 			case PAM_ERROR_MSG:
 			case PAM_TEXT_INFO:
 				if ((*msg)[count].msg != NULL) {
 					if (pamstate == INITIAL_LOGIN)
 						pam_msg_cat((*msg)[count].msg);
 					else {
 						fputs((*msg)[count].msg, stderr);
 						fputs("\n", stderr);
 					}
 				}
 				reply[count].resp = xstrdup("");
 				reply[count].resp_retcode = PAM_SUCCESS;
 				break;
 			default:
 				free(reply);
 				return PAM_CONV_ERR;
 		}
 	}

 	*resp = reply;

 	return PAM_SUCCESS;
 }

 /* Called at exit to cleanly shutdown PAM */
 void pam_cleanup_proc(void *context)
 {
 	int pam_retval;

 	if (pamh != NULL)
 	{
 		pam_retval = pam_close_session(pamh, 0);
 		if (pam_retval != PAM_SUCCESS) {
 			log("Cannot close PAM session[%d]: %.200s",
 				pam_retval, PAM_STRERROR(pamh, pam_retval));
 		}

 		pam_retval = pam_setcred(pamh, PAM_DELETE_CRED);
 		if (pam_retval != PAM_SUCCESS) {
 			debug("Cannot delete credentials[%d]: %.200s",
 				pam_retval, PAM_STRERROR(pamh, pam_retval));
 		}

 		pam_retval = pam_end(pamh, pam_retval);
 		if (pam_retval != PAM_SUCCESS) {
 			log("Cannot release PAM authentication[%d]: %.200s",
 				pam_retval, PAM_STRERROR(pamh, pam_retval));
 		}
 	}
 }

 /* Attempt password authentation using PAM */
 int auth_pam_password(struct passwd *pw, const char *password)
 {
 	extern ServerOptions options;
 	int pam_retval;

 	pam_set_conv(&conv);

 	/* deny if no user. */
 	if (pw == NULL)
 		return 0;
 	if (pw->pw_uid == 0 && options.permit_root_login == 2)
 		return 0;
 	if (*password == '\0' && options.permit_empty_passwd == 0)
 		return 0;

 	pampasswd = password;

 	pamstate = INITIAL_LOGIN;
 	pam_retval = do_pam_authenticate(0);
 	if (pam_retval == PAM_SUCCESS) {
 		debug("PAM Password authentication accepted for user \"%.100s\"",
 			pw->pw_name);
 		return 1;
 	} else {
 		debug("PAM Password authentication for \"%.100s\" failed[%d]: %s",
 			pw->pw_name, pam_retval, PAM_STRERROR(pamh, pam_retval));
 		return 0;
 	}
 }

 /* Do account management using PAM */
 int do_pam_account(char *username, char *remote_user)
 {
 	int pam_retval;

 	debug("PAM setting rhost to \"%.200s\"", get_canonical_hostname());
 	pam_retval = pam_set_item(pamh, PAM_RHOST,
 		get_canonical_hostname());
 	if (pam_retval != PAM_SUCCESS) {
 		fatal("PAM set rhost failed[%d]: %.200s",
 			pam_retval, PAM_STRERROR(pamh, pam_retval));
 	}

 	if (remote_user != NULL) {
 		debug("PAM setting ruser to \"%.200s\"", remote_user);
 		pam_retval = pam_set_item(pamh, PAM_RUSER, remote_user);
 		if (pam_retval != PAM_SUCCESS) {
 			fatal("PAM set ruser failed[%d]: %.200s",
 				pam_retval, PAM_STRERROR(pamh, pam_retval));
 		}
 	}

 	pam_retval = pam_acct_mgmt(pamh, 0);
 	switch (pam_retval) {
 		case PAM_SUCCESS:
 			/* This is what we want */
 			break;
 		case PAM_NEW_AUTHTOK_REQD:
 			pam_msg_cat(NEW_AUTHTOK_MSG);
 			/* flag that password change is necessary */
 			password_change_required = 1;
 			break;
 		default:
 			log("PAM rejected by account configuration[%d]: %.200s",
 				pam_retval, PAM_STRERROR(pamh, pam_retval));
 			return(0);
 	}

 	return(1);
 }

 /* Do PAM-specific session initialisation */
 void do_pam_session(char *username, const char *ttyname)
 {
 	int pam_retval;

 	if (ttyname != NULL) {
 		debug("PAM setting tty to \"%.200s\"", ttyname);
 		pam_retval = pam_set_item(pamh, PAM_TTY, ttyname);
 		if (pam_retval != PAM_SUCCESS) {
 			fatal("PAM set tty failed[%d]: %.200s",
 				pam_retval, PAM_STRERROR(pamh, pam_retval));
 		}
 	}

 	pam_retval = pam_open_session(pamh, 0);
 	if (pam_retval != PAM_SUCCESS) {
 		fatal("PAM session setup failed[%d]: %.200s",
 			pam_retval, PAM_STRERROR(pamh, pam_retval));
 	}
 }

 /* Set PAM credentials */
 void do_pam_setcred(void)
 {
 	int pam_retval;

 	debug("PAM establishing creds");
 	pam_retval = pam_setcred(pamh, PAM_ESTABLISH_CRED);
 	if (pam_retval != PAM_SUCCESS) {
 		if(was_authenticated) {
 			fatal("PAM setcred failed[%d]: %.200s",
 				pam_retval, PAM_STRERROR(pamh, pam_retval));
 		} else {
 			debug("PAM setcred failed[%d]: %.200s",
 				pam_retval, PAM_STRERROR(pamh, pam_retval));
 		}
 	}
 }

 /* accessor function for file scope static variable */
 int pam_password_change_required(void)
 {
 	return password_change_required;
 }

 /*
  * Have user change authentication token if pam_acct_mgmt() indicated
  * it was expired.  This needs to be called after an interactive
  * session is established and the user's pty is connected to
  * stdin/stout/stderr.
  */
 void do_pam_chauthtok(void)
 {
 	int pam_retval;

 	if (password_change_required) {
 		pamstate = OTHER;
 		/*
 		 * XXX: should we really loop forever?
 		 */
 		do {
 			pam_retval = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
 			if (pam_retval != PAM_SUCCESS) {
 				log("PAM pam_chauthtok failed[%d]: %.200s",
 					pam_retval, PAM_STRERROR(pamh, pam_retval));
 			}
 		} while (pam_retval != PAM_SUCCESS);
 	}
 }

 /* Cleanly shutdown PAM */
 void finish_pam(void)
 {
 	pam_cleanup_proc(NULL);
 	fatal_remove_cleanup(&pam_cleanup_proc, NULL);
 }

 /* Start PAM authentication for specified account */
 void start_pam(struct passwd *pw)
 {
 	int pam_retval;

 	debug("Starting up PAM with username \"%.200s\"", pw->pw_name);

 	pam_retval = pam_start(SSHD_PAM_SERVICE, pw->pw_name, &conv, &pamh);

 	if (pam_retval != PAM_SUCCESS) {
 		fatal("PAM initialisation failed[%d]: %.200s",
 			pam_retval, PAM_STRERROR(pamh, pam_retval));
 	}

 #ifdef PAM_TTY_KLUDGE
 	/*
 	 * Some PAM modules (e.g. pam_time) require a TTY to operate,
 	 * and will fail in various stupid ways if they don't get one.
 	 * sshd doesn't set the tty until too late in the auth process and may
 	 * not even need one (for tty-less connections)
 	 * Kludge: Set a fake PAM_TTY
 	 */
 	pam_retval = pam_set_item(pamh, PAM_TTY, "ssh");
 	if (pam_retval != PAM_SUCCESS) {
 		fatal("PAM set tty failed[%d]: %.200s",
 			pam_retval, PAM_STRERROR(pamh, pam_retval));
 	}
 #endif /* PAM_TTY_KLUDGE */

 	fatal_add_cleanup(&pam_cleanup_proc, NULL);
 }

 /* Return list of PAM enviornment strings */
 char **fetch_pam_environment(void)
 {
 #ifdef HAVE_PAM_GETENVLIST
 	return(pam_getenvlist(pamh));
 #else /* HAVE_PAM_GETENVLIST */
 	return(NULL);
 #endif /* HAVE_PAM_GETENVLIST */
 }

 /* Print any messages that have been generated during authentication */
 /* or account checking to stderr */
 void print_pam_messages(void)
 {
 	if (pam_msg != NULL)
 		fputs(pam_msg, stderr);
 }

 /* Append a message to the PAM message buffer */
 void pam_msg_cat(const char *msg)
 {
 	char *p;
 	size_t new_msg_len;
 	size_t pam_msg_len;

 	new_msg_len = strlen(msg);

 	if (pam_msg) {
 		pam_msg_len = strlen(pam_msg);
 		pam_msg = xrealloc(pam_msg, new_msg_len + pam_msg_len + 2);
 		p = pam_msg + pam_msg_len;
 	} else {
 		pam_msg = p = xmalloc(new_msg_len + 2);
 	}

 	memcpy(p, msg, new_msg_len);
 	p[new_msg_len] = '\n';
 	p[new_msg_len + 1] = '\0';
 }

 #endif /* USE_PAM */
	/*
	* Copyright (c) 2000 Damien Miller. 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"

	#ifdef USE_PAM
	#include "ssh.h"
	#include "xmalloc.h"
	#include "servconf.h"

	RCSID("$Id: auth-pam.c,v 1.19 2000/12/03 00:51:51 djm Exp $");

	#define NEW_AUTHTOK_MSG \
	"Warning: Your password has expired, please change it now"

	/* Callbacks */
	static int pamconv(int num_msg, const struct pam_message **msg,
	struct pam_response *resp, void appdata_ptr);
	void pam_cleanup_proc(void *context);
	void pam_msg_cat(const char *msg);

	/* module-local variables */
	static struct pam_conv conv = {
	pamconv,
	NULL
	};
	static pam_handle_t *pamh = NULL;
	static const char *pampasswd = NULL;
	static char *pam_msg = NULL;

	/* states for pamconv() */
	enum { INITIAL_LOGIN, OTHER } pamstate = INITIAL_LOGIN;
	/* remember whether pam_acct_mgmt() returned PAM_NEWAUTHTOK_REQD */
	static int password_change_required = 0;
	/* remember whether the last pam_authenticate() succeeded or not */
	static int was_authenticated = 0;

	/* accessor which allows us to switch conversation structs according to
	* the authentication method being used */
	void pam_set_conv(struct pam_conv *conv)
	{
	pam_set_item(pamh, PAM_CONV, conv);
	}

	/* start an authentication run */
	int do_pam_authenticate(int flags)
	{
	int retval = pam_authenticate(pamh, flags);
	was_authenticated = (retval == PAM_SUCCESS);
	return retval;
	}

	/*
	* PAM conversation function.
	* There are two states this can run in.
	*
	* INITIAL_LOGIN mode simply feeds the password from the client into
	* PAM in response to PAM_PROMPT_ECHO_OFF, and collects output
	* messages with pam_msg_cat(). This is used during initial
	* authentication to bypass the normal PAM password prompt.
	*
	* OTHER mode handles PAM_PROMPT_ECHO_OFF with read_passphrase(prompt, 1)
	* and outputs messages to stderr. This mode is used if pam_chauthtok()
	* is called to update expired passwords.
	*/
	static int pamconv(int num_msg, const struct pam_message **msg,
	struct pam_response *resp, void appdata_ptr)
	{
	struct pam_response *reply;
	int count;
	char buf[1024];

	/* PAM will free this later */
	reply = malloc(num_msg * sizeof(*reply));
	if (reply == NULL)
	return PAM_CONV_ERR;

	for (count = 0; count < num_msg; count++) {
	switch ((*msg)[count].msg_style) {
	case PAM_PROMPT_ECHO_ON:
	if (pamstate == INITIAL_LOGIN) {
	free(reply);
	return PAM_CONV_ERR;
	} else {
	fputs((*msg)[count].msg, stderr);
	fgets(buf, sizeof(buf), stdin);
	reply[count].resp = xstrdup(buf);
	reply[count].resp_retcode = PAM_SUCCESS;
	break;
	}
	case PAM_PROMPT_ECHO_OFF:
	if (pamstate == INITIAL_LOGIN) {
	if (pampasswd == NULL) {
	free(reply);
	return PAM_CONV_ERR;
	}
	reply[count].resp = xstrdup(pampasswd);
	} else {
	reply[count].resp =
	xstrdup(read_passphrase((*msg)[count].msg, 1));
	}
	reply[count].resp_retcode = PAM_SUCCESS;
	break;
	case PAM_ERROR_MSG:
	case PAM_TEXT_INFO:
	if ((*msg)[count].msg != NULL) {
	if (pamstate == INITIAL_LOGIN)
	pam_msg_cat((*msg)[count].msg);
	else {
	fputs((*msg)[count].msg, stderr);
	fputs("\n", stderr);
	}
	}
	reply[count].resp = xstrdup("");
	reply[count].resp_retcode = PAM_SUCCESS;
	break;
	default:
	free(reply);
	return PAM_CONV_ERR;
	}
	}

	*resp = reply;

	return PAM_SUCCESS;
	}

	/* Called at exit to cleanly shutdown PAM */
	void pam_cleanup_proc(void *context)
	{
	int pam_retval;

	if (pamh != NULL)
	{
	pam_retval = pam_close_session(pamh, 0);
	if (pam_retval != PAM_SUCCESS) {
	log("Cannot close PAM session[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	}

	pam_retval = pam_setcred(pamh, PAM_DELETE_CRED);
	if (pam_retval != PAM_SUCCESS) {
	debug("Cannot delete credentials[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	}

	pam_retval = pam_end(pamh, pam_retval);
	if (pam_retval != PAM_SUCCESS) {
	log("Cannot release PAM authentication[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	}
	}
	}

	/* Attempt password authentation using PAM */
	int auth_pam_password(struct passwd pw, const char password)
	{
	extern ServerOptions options;
	int pam_retval;

	pam_set_conv(&conv);

	/* deny if no user. */
	if (pw == NULL)
	return 0;
	if (pw->pw_uid == 0 && options.permit_root_login == 2)
	return 0;
	if (*password == '\0' && options.permit_empty_passwd == 0)
	return 0;

	pampasswd = password;

	pamstate = INITIAL_LOGIN;
	pam_retval = do_pam_authenticate(0);
	if (pam_retval == PAM_SUCCESS) {
	debug("PAM Password authentication accepted for user \"%.100s\"",
	pw->pw_name);
	return 1;
	} else {
	debug("PAM Password authentication for \"%.100s\" failed[%d]: %s",
	pw->pw_name, pam_retval, PAM_STRERROR(pamh, pam_retval));
	return 0;
	}
	}

	/* Do account management using PAM */
	int do_pam_account(char username, char remote_user)
	{
	int pam_retval;

	debug("PAM setting rhost to \"%.200s\"", get_canonical_hostname());
	pam_retval = pam_set_item(pamh, PAM_RHOST,
	get_canonical_hostname());
	if (pam_retval != PAM_SUCCESS) {
	fatal("PAM set rhost failed[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	}

	if (remote_user != NULL) {
	debug("PAM setting ruser to \"%.200s\"", remote_user);
	pam_retval = pam_set_item(pamh, PAM_RUSER, remote_user);
	if (pam_retval != PAM_SUCCESS) {
	fatal("PAM set ruser failed[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	}
	}

	pam_retval = pam_acct_mgmt(pamh, 0);
	switch (pam_retval) {
	case PAM_SUCCESS:
	/* This is what we want */
	break;
	case PAM_NEW_AUTHTOK_REQD:
	pam_msg_cat(NEW_AUTHTOK_MSG);
	/* flag that password change is necessary */
	password_change_required = 1;
	break;
	default:
	log("PAM rejected by account configuration[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	return(0);
	}

	return(1);
	}

	/* Do PAM-specific session initialisation */
	void do_pam_session(char username, const char ttyname)
	{
	int pam_retval;

	if (ttyname != NULL) {
	debug("PAM setting tty to \"%.200s\"", ttyname);
	pam_retval = pam_set_item(pamh, PAM_TTY, ttyname);
	if (pam_retval != PAM_SUCCESS) {
	fatal("PAM set tty failed[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	}
	}

	pam_retval = pam_open_session(pamh, 0);
	if (pam_retval != PAM_SUCCESS) {
	fatal("PAM session setup failed[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	}
	}

	/* Set PAM credentials */
	void do_pam_setcred(void)
	{
	int pam_retval;

	debug("PAM establishing creds");
	pam_retval = pam_setcred(pamh, PAM_ESTABLISH_CRED);
	if (pam_retval != PAM_SUCCESS) {
	if(was_authenticated) {
	fatal("PAM setcred failed[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	} else {
	debug("PAM setcred failed[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	}
	}
	}

	/* accessor function for file scope static variable */
	int pam_password_change_required(void)
	{
	return password_change_required;
	}

	/*
	* Have user change authentication token if pam_acct_mgmt() indicated
	* it was expired. This needs to be called after an interactive
	* session is established and the user's pty is connected to
	* stdin/stout/stderr.
	*/
	void do_pam_chauthtok(void)
	{
	int pam_retval;

	if (password_change_required) {
	pamstate = OTHER;
	/*
	* XXX: should we really loop forever?
	*/
	do {
	pam_retval = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
	if (pam_retval != PAM_SUCCESS) {
	log("PAM pam_chauthtok failed[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	}
	} while (pam_retval != PAM_SUCCESS);
	}
	}

	/* Cleanly shutdown PAM */
	void finish_pam(void)
	{
	pam_cleanup_proc(NULL);
	fatal_remove_cleanup(&pam_cleanup_proc, NULL);
	}

	/* Start PAM authentication for specified account */
	void start_pam(struct passwd *pw)
	{
	int pam_retval;

	debug("Starting up PAM with username \"%.200s\"", pw->pw_name);

	pam_retval = pam_start(SSHD_PAM_SERVICE, pw->pw_name, &conv, &pamh);

	if (pam_retval != PAM_SUCCESS) {
	fatal("PAM initialisation failed[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	}

	#ifdef PAM_TTY_KLUDGE
	/*
	* Some PAM modules (e.g. pam_time) require a TTY to operate,
	* and will fail in various stupid ways if they don't get one.
	* sshd doesn't set the tty until too late in the auth process and may
	* not even need one (for tty-less connections)
	* Kludge: Set a fake PAM_TTY
	*/
	pam_retval = pam_set_item(pamh, PAM_TTY, "ssh");
	if (pam_retval != PAM_SUCCESS) {
	fatal("PAM set tty failed[%d]: %.200s",
	pam_retval, PAM_STRERROR(pamh, pam_retval));
	}
	#endif /* PAM_TTY_KLUDGE */

	fatal_add_cleanup(&pam_cleanup_proc, NULL);
	}

	/* Return list of PAM enviornment strings */
	char **fetch_pam_environment(void)
	{
	#ifdef HAVE_PAM_GETENVLIST
	return(pam_getenvlist(pamh));
	#else /* HAVE_PAM_GETENVLIST */
	return(NULL);
	#endif /* HAVE_PAM_GETENVLIST */
	}

	/* Print any messages that have been generated during authentication */
	/* or account checking to stderr */
	void print_pam_messages(void)
	{
	if (pam_msg != NULL)
	fputs(pam_msg, stderr);
	}

	/* Append a message to the PAM message buffer */
	void pam_msg_cat(const char *msg)
	{
	char *p;
	size_t new_msg_len;
	size_t pam_msg_len;

	new_msg_len = strlen(msg);

	if (pam_msg) {
	pam_msg_len = strlen(pam_msg);
	pam_msg = xrealloc(pam_msg, new_msg_len + pam_msg_len + 2);
	p = pam_msg + pam_msg_len;
	} else {
	pam_msg = p = xmalloc(new_msg_len + 2);
	}

	memcpy(p, msg, new_msg_len);
	p[new_msg_len] = '\n';
	p[new_msg_len + 1] = '\0';
	}

	#endif /* USE_PAM */