/*
* 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 1.1.1.4 2000/12/06 21:56:10 wsanchez 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() */
typedef enum { INITIAL_LOGIN, OTHER } pamstates;
static pamstates pamstate = INITIAL_LOGIN;
/* remember whether pam_acct_mgmt() returned PAM_NEWAUTHTOK_REQD */
static int password_change_required = 0;
/*
* 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;
/* 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 = pam_authenticate(pamh, 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) {
fatal("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 */
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