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/*
* This program is designed to run setuid(root) or with sufficient
* privilege to read the cached password database. It is designed
* to provide a mechanism for the current user (defined by this
* process' uid) to verify their own password.
*
* The password is read from the standard input. The exit status of
* this program indicates whether the user is authenticated or not.
*
* Copyright information is located at the end of the file.
*
*/
#ifdef MEMORY_DEBUG
# undef exit
# undef strdup
# undef free
#endif /* MEMORY_DEBUG */
#include <stdarg.h>
#include <signal.h>
#include <sys/types.h>
#include <pwd.h>
#include <syslog.h>
#include "cc_private.h"
#define MAXPASS 200 /* the maximum length of a password */
#define CCREDS_PASSED 0
#define CCREDS_FAILED 1
/* syslogging function for errors and other information */
static void _log_err(int err, const char *format,...)
{
va_list args;
va_start(args, format);
openlog("ccreds_chkpwd", LOG_CONS | LOG_PID, LOG_AUTH);
vsyslog(err, format, args);
va_end(args);
closelog();
}
static void su_sighandler(int sig)
{
#ifndef SA_RESETHAND
/* emulate the behaviour of the SA_RESETHAND flag */
if ( sig == SIGILL || sig == SIGTRAP || sig == SIGBUS || sig = SIGSERV )
signal(sig, SIG_DFL);
#endif
if (sig > 0) {
_log_err(LOG_NOTICE, "caught signal %d.", sig);
exit(sig);
}
}
static void setup_signals(void)
{
struct sigaction action; /* posix signal structure */
/*
* Setup signal handlers
*/
(void) memset((void *) &action, 0, sizeof(action));
action.sa_handler = su_sighandler;
#ifdef SA_RESETHAND
action.sa_flags = SA_RESETHAND;
#endif
(void) sigaction(SIGILL, &action, NULL);
(void) sigaction(SIGTRAP, &action, NULL);
(void) sigaction(SIGBUS, &action, NULL);
(void) sigaction(SIGSEGV, &action, NULL);
action.sa_handler = SIG_IGN;
action.sa_flags = 0;
(void) sigaction(SIGTERM, &action, NULL);
(void) sigaction(SIGHUP, &action, NULL);
(void) sigaction(SIGINT, &action, NULL);
(void) sigaction(SIGQUIT, &action, NULL);
}
static int _ccreds_verify_password(const char *service, const char *name,
const char *ccredsfile, const char *p)
{
int rc, retval = CCREDS_FAILED;
pam_cc_handle_t *pamcch;
rc = pam_cc_start(service, name, ccredsfile, CC_FLAGS_READ_ONLY,
&pamcch);
if (rc != PAM_SUCCESS) {
_log_err(LOG_DEBUG, "error initializing");
retval = CCREDS_FAILED;
goto _return;
}
rc = pam_cc_validate_credentials(pamcch, PAM_CC_TYPE_DEFAULT, p,
strlen(p));
if (rc != PAM_SUCCESS) {
_log_err(LOG_DEBUG, "error reading cached credentials");
retval = CCREDS_FAILED;
goto _return;
}
retval = CCREDS_PASSED;
pam_cc_end(&pamcch);
_return:
return retval;
}
static char *getuidname(uid_t uid)
{
struct passwd *pw;
static char username[32];
pw = getpwuid(uid);
if (pw == NULL)
return NULL;
strncpy(username, pw->pw_name, sizeof(username));
username[sizeof(username) - 1] = '\0';
return username;
}
int main(int argc, char *argv[])
{
char pass[MAXPASS + 1];
int npass;
int force_failure = 0;
int retval = CCREDS_FAILED;
char *user;
char *user_arg;
char *service;
/*
* Catch or ignore as many signal as possible.
*/
setup_signals();
/*
* we establish that this program is running with non-tty stdin.
* this is to discourage casual use. It does *NOT* prevent an
* intruder from repeatadly running this program to determine the
* password of the current user (brute force attack, but one for
* which the attacker must already have gained access to the user's
* account).
*/
if (isatty(STDIN_FILENO)) {
_log_err(LOG_NOTICE
,"inappropriate use of ccreds helper binary [UID=%d,tty]"
,getuid());
fprintf(stderr
,"This binary is not designed for running in this way\n"
"-- the system administrator has been informed\n");
sleep(10); /* this should discourage/annoy the user */
return CCREDS_FAILED;
}
/*
* determine the current user's name is
*/
user = getuidname(getuid());
if (argc < 2 || argc > 3) {
_log_err(LOG_NOTICE
,"inappropriate use of ccreds helper binary [UID=%d,bad argv]"
,getuid());
fprintf(stderr
,"This binary is not designed for running in this way\n"
"-- the system administrator has been informed\n");
sleep(10); /* this should discourage/annoy the user */
return CCREDS_FAILED;
}
user_arg = argv[1];
service = (argc > 2) ? argv[2] : NULL;
/* Verify that user matches */
if (strcmp(user, user_arg)) {
force_failure = 1;
}
/* read the password from stdin (a pipe from the pam_ccreds module) */
npass = read(STDIN_FILENO, pass, MAXPASS);
if (npass < 0) { /* is it a valid password? */
_log_err(LOG_DEBUG, "no password supplied");
} else if (npass >= MAXPASS) {
_log_err(LOG_DEBUG, "password too long");
} else {
if (npass == 0) {
/* the password is blank */
retval = _ccreds_verify_password(service, user, NULL, "");
} else {
/* does pass agree with the official one? */
pass[npass] = '\0'; /* NUL terminate */
retval = _ccreds_verify_password(service, user, NULL, pass);
}
}
memset(pass, '\0', MAXPASS); /* clear memory of the password */
/* return pass or fail */
if ((retval != CCREDS_PASSED) || force_failure) {
return CCREDS_FAILED;
} else {
return CCREDS_PASSED;
}
}
/*
* This program is based on unix_chkpwd by Andrew G. Morgan.
*
* The modifications are Copyright (c) W. Michael Petullo, 2005.
* All rights reserved.
*
* See below for the original unix_chkpwd copyright notice.
*
* Copyright (c) Andrew G. Morgan, 1996. 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, and the entire permission notice in its entirety,
* including the disclaimer of warranties.
* 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.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* ALTERNATIVELY, this product may be distributed under the terms of
* the GNU Public License, in which case the provisions of the GPL are
* required INSTEAD OF the above restrictions. (This clause is
* necessary due to a potential bad interaction between the GPL and
* the restrictions contained in a BSD-style copyright.)
*
* THIS SOFTWARE IS PROVIDED ``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.
*/
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