path: root/auth-pam.c

/*
 * 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 "xmalloc.h"
#include "log.h"
#include "auth.h"
#include "auth-options.h"
#include "auth-pam.h"
#include "servconf.h"
#include "canohost.h"
#include "readpass.h"

extern char *__progname;

extern int use_privsep;

RCSID("$Id: auth-pam.c,v 1.56 2003/04/09 10:59:48 djm Exp $");

#define NEW_AUTHTOK_MSG \
	"Warning: Your password has expired, please change it now."
#define NEW_AUTHTOK_MSG_PRIVSEP \
	"Your password has expired, the session cannot proceed."

static int do_pam_conversation(int num_msg, const struct pam_message **msg,
	struct pam_response **resp, void *appdata_ptr);

/* module-local variables */
static struct pam_conv conv = {
	(int (*)())do_pam_conversation,
	NULL
};
static char *__pam_msg = NULL;
static pam_handle_t *__pamh = NULL;
static const char *__pampasswd = NULL;

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

/* Remember what has been initialised */
static int session_opened = 0;
static int creds_set = 0;

/* accessor which allows us to switch conversation structs according to
 * the authentication method being used */
void do_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 into __pam_msg.  This is used during initial
 * authentication to bypass the normal PAM password prompt.
 *
 * OTHER mode handles PAM_PROMPT_ECHO_OFF with read_passphrase()
 * and outputs messages to stderr. This mode is used if pam_chauthtok()
 * is called to update expired passwords.
 */
static int do_pam_conversation(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 = xmalloc(num_msg * sizeof(*reply));

	for (count = 0; count < num_msg; count++) {
		if (pamstate == INITIAL_LOGIN) {
			/*
			 * We can't use stdio yet, queue messages for 
			 * printing later
			 */
			switch(PAM_MSG_MEMBER(msg, count, msg_style)) {
			case PAM_PROMPT_ECHO_ON:
				xfree(reply);
				return PAM_CONV_ERR;
			case PAM_PROMPT_ECHO_OFF:
				if (__pampasswd == NULL) {
					xfree(reply);
					return PAM_CONV_ERR;
				}
				reply[count].resp = xstrdup(__pampasswd);
				reply[count].resp_retcode = PAM_SUCCESS;
				break;
			case PAM_ERROR_MSG:
			case PAM_TEXT_INFO:
				if (PAM_MSG_MEMBER(msg, count, msg) != NULL) {
					message_cat(&__pam_msg, 
					    PAM_MSG_MEMBER(msg, count, msg));
				}
				reply[count].resp = xstrdup("");
				reply[count].resp_retcode = PAM_SUCCESS;
				break;
			default:
				xfree(reply);
				return PAM_CONV_ERR;
			}
		} else {
			/*
			 * stdio is connected, so interact directly
			 */
			switch(PAM_MSG_MEMBER(msg, count, msg_style)) {
			case PAM_PROMPT_ECHO_ON:
				fputs(PAM_MSG_MEMBER(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:
				reply[count].resp = 
				    read_passphrase(PAM_MSG_MEMBER(msg, count,
					msg), RP_ALLOW_STDIN);
				reply[count].resp_retcode = PAM_SUCCESS;
				break;
			case PAM_ERROR_MSG:
			case PAM_TEXT_INFO:
				if (PAM_MSG_MEMBER(msg, count, msg) != NULL)
					fprintf(stderr, "%s\n", 
					    PAM_MSG_MEMBER(msg, count, msg));
				reply[count].resp = xstrdup("");
				reply[count].resp_retcode = PAM_SUCCESS;
				break;
			default:
				xfree(reply);
				return PAM_CONV_ERR;
			}
		}
	}

	*resp = reply;

	return PAM_SUCCESS;
}

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

	if (__pamh && session_opened) {
		pam_retval = pam_close_session(__pamh, 0);
		if (pam_retval != PAM_SUCCESS)
			logit("Cannot close PAM session[%d]: %.200s",
			    pam_retval, PAM_STRERROR(__pamh, pam_retval));
	}

	if (__pamh && creds_set) {
		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));
	}

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

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

	do_pam_set_conv(&conv);

	__pampasswd = password;

	pamstate = INITIAL_LOGIN;
	pam_retval = do_pam_authenticate(
	    options.permit_empty_passwd == 0 ? PAM_DISALLOW_NULL_AUTHTOK : 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;

	do_pam_set_conv(&conv);

	if (remote_user) {
		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);
	debug2("pam_acct_mgmt() = %d", pam_retval);
	switch (pam_retval) {
		case PAM_SUCCESS:
			/* This is what we want */
			break;
#if 0
		case PAM_NEW_AUTHTOK_REQD:
			message_cat(&__pam_msg, use_privsep ?
			    NEW_AUTHTOK_MSG_PRIVSEP : NEW_AUTHTOK_MSG);
			/* flag that password change is necessary */
			password_change_required = 1;
			/* disallow other functionality for now */
			no_port_forwarding_flag |= 2;
			no_agent_forwarding_flag |= 2;
			no_x11_forwarding_flag |= 2;
			break;
#endif
		default:
			logit("PAM rejected by account configuration[%d]: "
			    "%.200s", pam_retval, PAM_STRERROR(__pam