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/* pam_securetty module */
#define SECURETTY_FILE "/etc/securetty"
#define TTY_PREFIX "/dev/"
#define CMDLINE_FILE "/proc/cmdline"
#define CONSOLEACTIVE_FILE "/sys/class/tty/console/active"
/*
* 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
*/
#include "config.h"
#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>
#include <ctype.h>
#include <limits.h>
/*
* 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
#define PAM_SM_ACCOUNT
#include <security/pam_modules.h>
#include <security/pam_modutil.h>
#include <security/pam_ext.h>
#define PAM_DEBUG_ARG 0x0001
#define PAM_NOCONSOLE_ARG 0x0002
static int
_pam_parse (const pam_handle_t *pamh, 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 if (!strcmp(*argv, "noconsole"))
ctrl |= PAM_NOCONSOLE_ARG;
else {
pam_syslog(pamh, LOG_ERR, "unknown option: %s", *argv);
}
}
return ctrl;
}
static int
securetty_perform_check (pam_handle_t *pamh, int ctrl,
const char *function_name)
{
int retval = PAM_AUTH_ERR;
const char *username;
const char *uttyname;
const void *void_uttyname;
char ttyfileline[256];
char ptname[256];
struct stat ttyfileinfo;
struct passwd *user_pwd;
FILE *ttyfile;
/* log a trail for debugging */
if (ctrl & PAM_DEBUG_ARG) {
pam_syslog(pamh, LOG_DEBUG, "pam_securetty called via %s function",
function_name);
}
retval = pam_get_user(pamh, &username, NULL);
if (retval != PAM_SUCCESS || username == NULL) {
pam_syslog(pamh, LOG_WARNING, "cannot determine username");
return (retval == PAM_CONV_AGAIN ? PAM_INCOMPLETE:PAM_SERVICE_ERR);
}
user_pwd = pam_modutil_getpwnam(pamh, username);
if (user_pwd != NULL && user_pwd->pw_uid != 0) {
/* If the user is not root, securetty's does not apply to them */
return PAM_SUCCESS;
}
/* The user is now either root or an invalid / mistyped username */
retval = pam_get_item(pamh, PAM_TTY, &void_uttyname);
uttyname = void_uttyname;
if (retval != PAM_SUCCESS || uttyname == NULL) {
pam_syslog (pamh, LOG_ERR, "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;
}
if (stat(SECURETTY_FILE, &ttyfileinfo)) {
pam_syslog(pamh, LOG_NOTICE, "Couldn't open %s: %m", 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_syslog(pamh, LOG_ERR,
"%s is either world writable or not a normal file",
SECURETTY_FILE);
return PAM_AUTH_ERR;
}
ttyfile = fopen(SECURETTY_FILE,"r");
if (ttyfile == NULL) { /* Check that we opened it successfully */
pam_syslog(pamh, LOG_ERR, "Error opening %s: %m", SECURETTY_FILE);
return PAM_SERVICE_ERR;
}
if (isdigit(uttyname[0])) {
snprintf(ptname, sizeof(ptname), "pts/%s", uttyname);
} else {
ptname[0] = '\0';
}
retval = 1;
while ((fgets(ttyfileline, sizeof(ttyfileline)-1, ttyfile) != NULL)
&& retval) {
if (ttyfileline[strlen(ttyfileline) - 1] == '\n')
ttyfileline[strlen(ttyfileline) - 1] = '\0';
retval = ( strcmp(ttyfileline, uttyname)
&& (!ptname[0] || strcmp(ptname, uttyname)) );
}
fclose(ttyfile);
if (retval && !(ctrl & PAM_NOCONSOLE_ARG)) {
FILE *cmdlinefile;
/* Allow access from the kernel console, if enabled */
cmdlinefile = fopen(CMDLINE_FILE, "r");
if (cmdlinefile != NULL) {
char line[LINE_MAX], *p;
p = fgets(line, sizeof(line), cmdlinefile);
fclose(cmdlinefile);
for (; p; p = strstr(p+1, "console=")) {
char *e;
/* Test whether this is a beginning of a word? */
if (p > line && p[-1] != ' ')
continue;
/* Is this our console? */
if (strncmp(p + 8, uttyname, strlen(uttyname)))
continue;
/* Is there any garbage after the TTY name? */
e = p + 8 + strlen(uttyname);
if (*e == ',' || *e == ' ' || *e == '\n' || *e == 0) {
retval = 0;
break;
}
}
}
}
if (retval && !(ctrl & PAM_NOCONSOLE_ARG)) {
FILE *consoleactivefile;
/* Allow access from the active console */
consoleactivefile = fopen(CONSOLEACTIVE_FILE, "r");
if (consoleactivefile != NULL) {
char line[LINE_MAX], *p, *n;
line[0] = 0;
p = fgets(line, sizeof(line), consoleactivefile);
fclose(consoleactivefile);
if (p) {
/* remove the newline character at end */
if (line[strlen(line)-1] == '\n')
line[strlen(line)-1] = 0;
for (n = p; n != NULL; p = n+1) {
if ((n = strchr(p, ' ')) != NULL)
*n = '\0';
if (strcmp(p, uttyname) == 0) {
retval = 0;
break;
}
}
}
}
}
if (retval) {
pam_syslog(pamh, LOG_NOTICE, "access denied: tty '%s' is not secure !",
uttyname);
retval = PAM_AUTH_ERR;
if (user_pwd == NULL) {
retval = PAM_USER_UNKNOWN;
}
} else {
if (ctrl & PAM_DEBUG_ARG) {
pam_syslog(pamh, LOG_DEBUG, "access allowed for '%s' on '%s'",
username, uttyname);
}
retval = PAM_SUCCESS;
}
return retval;
}
/* --- authentication management functions --- */
int pam_sm_authenticate(pam_handle_t *pamh, int flags UNUSED, int argc,
const char **argv)
{
int ctrl;
/* parse the arguments */
ctrl = _pam_parse (pamh, argc, argv);
return securetty_perform_check(pamh, ctrl, __FUNCTION__);
}
int
pam_sm_setcred (pam_handle_t *pamh UNUSED, int flags UNUSED,
int argc UNUSED, const char **argv UNUSED)
{
return PAM_SUCCESS;
}
/* --- account management functions --- */
int
pam_sm_acct_mgmt (pam_handle_t *pamh, int flags UNUSED,
int argc, const char **argv)
{
int ctrl;
/* parse the arguments */
ctrl = _pam_parse (pamh, argc, argv);
/* take the easy route */
return securetty_perform_check(pamh, ctrl, __FUNCTION__);
}
/* end of module definition */
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