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|
/* pam_securetty module */
#define SECURETTY_FILE "/etc/securetty"
#define TTY_PREFIX "/dev/"
/*
* by Elliot Lee <sopwith@redhat.com>, Red Hat Software.
* July 25, 1996.
* This code shamelessly ripped from the pam_rootok module.
* Slight modifications AGM. 1996/12/3
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <syslog.h>
#include <stdarg.h>
#include <pwd.h>
#include <string.h>
#define PAM_SM_AUTH
/*
* here, we make a definition for the externally accessible function
* in this file (this definition is required for static a module
* but strongly encouraged generally) it is used to instruct the
* modules include file to define the function prototypes.
*/
#define PAM_SM_AUTH
#include <security/pam_modules.h>
/* some syslogging */
static void _pam_log(int err, const char *format, ...)
{
va_list args;
va_start(args, format);
openlog("PAM-securetty", LOG_CONS|LOG_PID, LOG_AUTH);
vsyslog(err, format, args);
va_end(args);
closelog();
}
/* argument parsing */
#define PAM_DEBUG_ARG 0x0001
static int _pam_parse(int argc, const char **argv)
{
int ctrl=0;
/* step through arguments */
for (ctrl=0; argc-- > 0; ++argv) {
/* generic options */
if (!strcmp(*argv,"debug"))
ctrl |= PAM_DEBUG_ARG;
else {
_pam_log(LOG_ERR,"pam_parse: unknown option; %s",*argv);
}
}
return ctrl;
}
/* --- authentication management functions (only) --- */
PAM_EXTERN
int pam_sm_authenticate(pam_handle_t *pamh,int flags,int argc
,const char **argv)
{
int retval = PAM_AUTH_ERR;
const char *username;
char *uttyname;
char ttyfileline[256];
struct stat ttyfileinfo;
struct passwd *user_pwd;
FILE *ttyfile;
int ctrl;
/* parse the arguments */
ctrl = _pam_parse(argc, argv);
retval = pam_get_user(pamh, &username, NULL);
if (retval != PAM_SUCCESS || username == NULL) {
if (ctrl & PAM_DEBUG_ARG) {
_pam_log(LOG_WARNING, "cannot determine username");
}
return (retval == PAM_CONV_AGAIN
? PAM_INCOMPLETE:PAM_SERVICE_ERR);
}
retval = pam_get_item(pamh, PAM_TTY, (const void **)&uttyname);
if (retval != PAM_SUCCESS || uttyname == NULL) {
if (ctrl & PAM_DEBUG_ARG) {
_pam_log(LOG_WARNING, "cannot determine user's tty");
}
return PAM_SERVICE_ERR;
}
/* The PAM_TTY item may be prefixed with "/dev/" - skip that */
if (strncmp(TTY_PREFIX, uttyname, sizeof(TTY_PREFIX)-1) == 0)
uttyname += sizeof(TTY_PREFIX)-1;
user_pwd = getpwnam(username);
if (user_pwd == NULL) {
return PAM_IGNORE;
} else if (user_pwd->pw_uid != 0) { /* If the user is not root,
securetty's does not apply
to them */
return PAM_SUCCESS;
}
if (stat(SECURETTY_FILE, &ttyfileinfo)) {
_pam_log(LOG_NOTICE, "Couldn't open " SECURETTY_FILE);
return PAM_SUCCESS; /* for compatibility with old securetty handling,
this needs to succeed. But we still log the
error. */
}
if ((ttyfileinfo.st_mode & S_IWOTH)
|| !S_ISREG(ttyfileinfo.st_mode)) {
/* If the file is world writable or is not a
normal file, return error */
_pam_log(LOG_ERR, SECURETTY_FILE
" is either world writable or not a normal file");
return PAM_AUTH_ERR;
}
ttyfile = fopen(SECURETTY_FILE,"r");
if(ttyfile == NULL) { /* Check that we opened it successfully */
_pam_log(LOG_ERR,
"Error opening " SECURETTY_FILE);
return PAM_SERVICE_ERR;
}
/* There should be no more errors from here on */
retval=PAM_AUTH_ERR;
/* This loop assumes that PAM_SUCCESS == 0
and PAM_AUTH_ERR != 0 */
while((fgets(ttyfileline,sizeof(ttyfileline)-1, ttyfile) != NULL)
&& retval) {
if(ttyfileline[strlen(ttyfileline) - 1] == '\n')
ttyfileline[strlen(ttyfileline) - 1] = '\0';
retval = strcmp(ttyfileline,uttyname);
}
fclose(ttyfile);
if(retval) {
if (ctrl & PAM_DEBUG_ARG)
_pam_log(LOG_WARNING, "access denied: tty '%s' is not secure !",
uttyname);
retval = PAM_AUTH_ERR;
}
if ((retval == PAM_SUCCESS) && (ctrl & PAM_DEBUG_ARG))
_pam_log(LOG_DEBUG, "access allowed for '%s' on '%s'",
username, uttyname);
return retval;
}
PAM_EXTERN
int pam_sm_setcred(pam_handle_t *pamh,int flags,int argc
,const char **argv)
{
return PAM_SUCCESS;
}
#ifdef PAM_STATIC
/* static module data */
struct pam_module _pam_securetty_modstruct = {
"pam_securetty",
pam_sm_authenticate,
pam_sm_setcred,
NULL,
NULL,
NULL,
NULL,
};
#endif
/* end of module definition */
|
