398 lines
11 KiB
C
398 lines
11 KiB
C
/*
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* Copyright (c) 2000 Damien Miller. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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#ifdef USE_PAM
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#include "ssh.h"
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#include "xmalloc.h"
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#include "servconf.h"
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RCSID("$Id: auth-pam.c,v 1.19 2000/12/03 00:51:51 djm Exp $");
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#define NEW_AUTHTOK_MSG \
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"Warning: Your password has expired, please change it now"
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/* Callbacks */
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static int pamconv(int num_msg, const struct pam_message **msg,
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struct pam_response **resp, void *appdata_ptr);
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void pam_cleanup_proc(void *context);
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void pam_msg_cat(const char *msg);
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/* module-local variables */
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static struct pam_conv conv = {
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pamconv,
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NULL
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};
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static pam_handle_t *pamh = NULL;
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static const char *pampasswd = NULL;
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static char *pam_msg = NULL;
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/* states for pamconv() */
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enum { INITIAL_LOGIN, OTHER } pamstate = INITIAL_LOGIN;
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/* remember whether pam_acct_mgmt() returned PAM_NEWAUTHTOK_REQD */
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static int password_change_required = 0;
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/* remember whether the last pam_authenticate() succeeded or not */
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static int was_authenticated = 0;
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/* accessor which allows us to switch conversation structs according to
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* the authentication method being used */
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void pam_set_conv(struct pam_conv *conv)
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{
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pam_set_item(pamh, PAM_CONV, conv);
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}
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/* start an authentication run */
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int do_pam_authenticate(int flags)
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{
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int retval = pam_authenticate(pamh, flags);
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was_authenticated = (retval == PAM_SUCCESS);
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return retval;
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}
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/*
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* PAM conversation function.
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* There are two states this can run in.
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*
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* INITIAL_LOGIN mode simply feeds the password from the client into
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* PAM in response to PAM_PROMPT_ECHO_OFF, and collects output
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* messages with pam_msg_cat(). This is used during initial
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* authentication to bypass the normal PAM password prompt.
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*
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* OTHER mode handles PAM_PROMPT_ECHO_OFF with read_passphrase(prompt, 1)
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* and outputs messages to stderr. This mode is used if pam_chauthtok()
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* is called to update expired passwords.
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*/
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static int pamconv(int num_msg, const struct pam_message **msg,
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struct pam_response **resp, void *appdata_ptr)
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{
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struct pam_response *reply;
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int count;
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char buf[1024];
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/* PAM will free this later */
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reply = malloc(num_msg * sizeof(*reply));
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if (reply == NULL)
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return PAM_CONV_ERR;
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for (count = 0; count < num_msg; count++) {
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switch ((*msg)[count].msg_style) {
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case PAM_PROMPT_ECHO_ON:
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if (pamstate == INITIAL_LOGIN) {
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free(reply);
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return PAM_CONV_ERR;
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} else {
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fputs((*msg)[count].msg, stderr);
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fgets(buf, sizeof(buf), stdin);
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reply[count].resp = xstrdup(buf);
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reply[count].resp_retcode = PAM_SUCCESS;
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break;
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}
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case PAM_PROMPT_ECHO_OFF:
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if (pamstate == INITIAL_LOGIN) {
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if (pampasswd == NULL) {
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free(reply);
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return PAM_CONV_ERR;
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}
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reply[count].resp = xstrdup(pampasswd);
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} else {
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reply[count].resp =
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xstrdup(read_passphrase((*msg)[count].msg, 1));
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}
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reply[count].resp_retcode = PAM_SUCCESS;
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break;
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case PAM_ERROR_MSG:
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case PAM_TEXT_INFO:
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if ((*msg)[count].msg != NULL) {
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if (pamstate == INITIAL_LOGIN)
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pam_msg_cat((*msg)[count].msg);
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else {
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fputs((*msg)[count].msg, stderr);
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fputs("\n", stderr);
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}
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}
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reply[count].resp = xstrdup("");
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reply[count].resp_retcode = PAM_SUCCESS;
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break;
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default:
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free(reply);
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return PAM_CONV_ERR;
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}
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}
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*resp = reply;
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return PAM_SUCCESS;
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}
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/* Called at exit to cleanly shutdown PAM */
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void pam_cleanup_proc(void *context)
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{
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int pam_retval;
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if (pamh != NULL)
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{
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pam_retval = pam_close_session(pamh, 0);
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if (pam_retval != PAM_SUCCESS) {
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log("Cannot close PAM session[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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}
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pam_retval = pam_setcred(pamh, PAM_DELETE_CRED);
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if (pam_retval != PAM_SUCCESS) {
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debug("Cannot delete credentials[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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}
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pam_retval = pam_end(pamh, pam_retval);
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if (pam_retval != PAM_SUCCESS) {
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log("Cannot release PAM authentication[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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}
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}
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}
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/* Attempt password authentation using PAM */
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int auth_pam_password(struct passwd *pw, const char *password)
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{
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extern ServerOptions options;
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int pam_retval;
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pam_set_conv(&conv);
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/* deny if no user. */
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if (pw == NULL)
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return 0;
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if (pw->pw_uid == 0 && options.permit_root_login == 2)
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return 0;
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if (*password == '\0' && options.permit_empty_passwd == 0)
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return 0;
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pampasswd = password;
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pamstate = INITIAL_LOGIN;
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pam_retval = do_pam_authenticate(0);
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if (pam_retval == PAM_SUCCESS) {
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debug("PAM Password authentication accepted for user \"%.100s\"",
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pw->pw_name);
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return 1;
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} else {
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debug("PAM Password authentication for \"%.100s\" failed[%d]: %s",
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pw->pw_name, pam_retval, PAM_STRERROR(pamh, pam_retval));
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return 0;
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}
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}
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/* Do account management using PAM */
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int do_pam_account(char *username, char *remote_user)
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{
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int pam_retval;
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debug("PAM setting rhost to \"%.200s\"", get_canonical_hostname());
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pam_retval = pam_set_item(pamh, PAM_RHOST,
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get_canonical_hostname());
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if (pam_retval != PAM_SUCCESS) {
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fatal("PAM set rhost failed[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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}
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if (remote_user != NULL) {
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debug("PAM setting ruser to \"%.200s\"", remote_user);
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pam_retval = pam_set_item(pamh, PAM_RUSER, remote_user);
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if (pam_retval != PAM_SUCCESS) {
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fatal("PAM set ruser failed[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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}
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}
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pam_retval = pam_acct_mgmt(pamh, 0);
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switch (pam_retval) {
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case PAM_SUCCESS:
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/* This is what we want */
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break;
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case PAM_NEW_AUTHTOK_REQD:
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pam_msg_cat(NEW_AUTHTOK_MSG);
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/* flag that password change is necessary */
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password_change_required = 1;
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break;
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default:
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log("PAM rejected by account configuration[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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return(0);
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}
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return(1);
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}
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/* Do PAM-specific session initialisation */
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void do_pam_session(char *username, const char *ttyname)
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{
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int pam_retval;
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if (ttyname != NULL) {
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debug("PAM setting tty to \"%.200s\"", ttyname);
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pam_retval = pam_set_item(pamh, PAM_TTY, ttyname);
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if (pam_retval != PAM_SUCCESS) {
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fatal("PAM set tty failed[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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}
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}
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pam_retval = pam_open_session(pamh, 0);
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if (pam_retval != PAM_SUCCESS) {
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fatal("PAM session setup failed[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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}
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}
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/* Set PAM credentials */
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void do_pam_setcred(void)
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{
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int pam_retval;
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debug("PAM establishing creds");
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pam_retval = pam_setcred(pamh, PAM_ESTABLISH_CRED);
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if (pam_retval != PAM_SUCCESS) {
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if(was_authenticated) {
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fatal("PAM setcred failed[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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} else {
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debug("PAM setcred failed[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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}
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}
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}
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/* accessor function for file scope static variable */
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int pam_password_change_required(void)
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{
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return password_change_required;
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}
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/*
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* Have user change authentication token if pam_acct_mgmt() indicated
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* it was expired. This needs to be called after an interactive
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* session is established and the user's pty is connected to
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* stdin/stout/stderr.
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*/
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void do_pam_chauthtok(void)
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{
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int pam_retval;
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if (password_change_required) {
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pamstate = OTHER;
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/*
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* XXX: should we really loop forever?
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*/
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do {
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pam_retval = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
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if (pam_retval != PAM_SUCCESS) {
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log("PAM pam_chauthtok failed[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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}
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} while (pam_retval != PAM_SUCCESS);
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}
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}
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/* Cleanly shutdown PAM */
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void finish_pam(void)
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{
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pam_cleanup_proc(NULL);
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fatal_remove_cleanup(&pam_cleanup_proc, NULL);
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}
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/* Start PAM authentication for specified account */
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void start_pam(struct passwd *pw)
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{
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int pam_retval;
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debug("Starting up PAM with username \"%.200s\"", pw->pw_name);
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pam_retval = pam_start(SSHD_PAM_SERVICE, pw->pw_name, &conv, &pamh);
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if (pam_retval != PAM_SUCCESS) {
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fatal("PAM initialisation failed[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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}
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#ifdef PAM_TTY_KLUDGE
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/*
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* Some PAM modules (e.g. pam_time) require a TTY to operate,
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* and will fail in various stupid ways if they don't get one.
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* sshd doesn't set the tty until too late in the auth process and may
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* not even need one (for tty-less connections)
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* Kludge: Set a fake PAM_TTY
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*/
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pam_retval = pam_set_item(pamh, PAM_TTY, "ssh");
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if (pam_retval != PAM_SUCCESS) {
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fatal("PAM set tty failed[%d]: %.200s",
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pam_retval, PAM_STRERROR(pamh, pam_retval));
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}
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#endif /* PAM_TTY_KLUDGE */
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fatal_add_cleanup(&pam_cleanup_proc, NULL);
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}
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/* Return list of PAM enviornment strings */
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char **fetch_pam_environment(void)
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{
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#ifdef HAVE_PAM_GETENVLIST
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return(pam_getenvlist(pamh));
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#else /* HAVE_PAM_GETENVLIST */
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return(NULL);
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#endif /* HAVE_PAM_GETENVLIST */
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}
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/* Print any messages that have been generated during authentication */
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/* or account checking to stderr */
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void print_pam_messages(void)
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{
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if (pam_msg != NULL)
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fputs(pam_msg, stderr);
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}
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/* Append a message to the PAM message buffer */
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void pam_msg_cat(const char *msg)
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{
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char *p;
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size_t new_msg_len;
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size_t pam_msg_len;
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new_msg_len = strlen(msg);
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if (pam_msg) {
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pam_msg_len = strlen(pam_msg);
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pam_msg = xrealloc(pam_msg, new_msg_len + pam_msg_len + 2);
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p = pam_msg + pam_msg_len;
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} else {
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pam_msg = p = xmalloc(new_msg_len + 2);
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}
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memcpy(p, msg, new_msg_len);
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p[new_msg_len] = '\n';
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p[new_msg_len + 1] = '\0';
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}
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#endif /* USE_PAM */
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