hush/loginutils/login.c
Rob Landley d1f8c1c125 From Jan Kiszka: This patch fixes the security labelling of the login terminal
and process... There still remains some stuff to clean up (the whole
set_current_security_context() appears unnecessary complex to me), but this is
now at least working.
2006-03-27 23:04:42 +00:00

482 lines
11 KiB
C

/* vi: set sw=4 ts=4: */
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <termios.h>
#include <unistd.h>
#include <utmp.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <ctype.h>
#include <time.h>
#include "busybox.h"
#ifdef CONFIG_SELINUX
#include <selinux/selinux.h> /* for is_selinux_enabled() */
#include <selinux/get_context_list.h> /* for get_default_context() */
#include <selinux/flask.h> /* for security class definitions */
#include <errno.h>
#endif
#ifdef CONFIG_FEATURE_UTMP
// import from utmp.c
static void checkutmp(int picky);
static void setutmp(const char *name, const char *line);
/* Stuff global to this file */
static struct utmp utent;
#endif
// login defines
#define TIMEOUT 60
#define EMPTY_USERNAME_COUNT 10
#define USERNAME_SIZE 32
static int check_nologin ( int amroot );
#if defined CONFIG_FEATURE_SECURETTY
static int check_tty ( const char *tty );
#else
static inline int check_tty ( const char *tty ) { return 1; }
#endif
static int is_my_tty ( const char *tty );
static int login_prompt ( char *buf_name );
static void motd ( void );
static void alarm_handler ( int sig ATTRIBUTE_UNUSED)
{
fprintf (stderr, "\nLogin timed out after %d seconds.\n", TIMEOUT );
exit ( EXIT_SUCCESS );
}
int login_main(int argc, char **argv)
{
char tty[BUFSIZ];
char full_tty[200];
char fromhost[512];
char username[USERNAME_SIZE];
const char *tmp;
int amroot;
int flag;
int failed;
int count=0;
struct passwd *pw, pw_copy;
#ifdef CONFIG_WHEEL_GROUP
struct group *grp;
#endif
int opt_preserve = 0;
int opt_fflag = 0;
char *opt_host = 0;
int alarmstarted = 0;
#ifdef CONFIG_SELINUX
security_context_t user_sid = NULL;
#endif
username[0]=0;
amroot = ( getuid ( ) == 0 );
signal ( SIGALRM, alarm_handler );
alarm ( TIMEOUT );
alarmstarted = 1;
while (( flag = getopt(argc, argv, "f:h:p")) != EOF ) {
switch ( flag ) {
case 'p':
opt_preserve = 1;
break;
case 'f':
/*
* username must be a separate token
* (-f root, *NOT* -froot). --marekm
*/
if ( optarg != argv[optind-1] )
bb_show_usage( );
if ( !amroot ) /* Auth bypass only if real UID is zero */
bb_error_msg_and_die ( "-f permission denied" );
safe_strncpy(username, optarg, USERNAME_SIZE);
opt_fflag = 1;
break;
case 'h':
opt_host = optarg;
break;
default:
bb_show_usage( );
}
}
if (optind < argc) // user from command line (getty)
safe_strncpy(username, argv[optind], USERNAME_SIZE);
if ( !isatty ( 0 ) || !isatty ( 1 ) || !isatty ( 2 ))
return EXIT_FAILURE; /* Must be a terminal */
#ifdef CONFIG_FEATURE_UTMP
checkutmp ( !amroot );
#endif
tmp = ttyname ( 0 );
if ( tmp && ( strncmp ( tmp, "/dev/", 5 ) == 0 ))
safe_strncpy ( tty, tmp + 5, sizeof( tty ));
else if ( tmp && *tmp == '/' )
safe_strncpy ( tty, tmp, sizeof( tty ));
else
safe_strncpy ( tty, "UNKNOWN", sizeof( tty ));
#ifdef CONFIG_FEATURE_UTMP
if ( amroot )
memset ( utent.ut_host, 0, sizeof utent.ut_host );
#endif
if ( opt_host ) {
#ifdef CONFIG_FEATURE_UTMP
safe_strncpy ( utent.ut_host, opt_host, sizeof( utent. ut_host ));
#endif
snprintf ( fromhost, sizeof( fromhost ) - 1, " on `%.100s' from `%.200s'", tty, opt_host );
}
else
snprintf ( fromhost, sizeof( fromhost ) - 1, " on `%.100s'", tty );
setpgrp();
openlog ( "login", LOG_PID | LOG_CONS | LOG_NOWAIT, LOG_AUTH );
while ( 1 ) {
failed = 0;
if ( !username[0] )
if(!login_prompt ( username ))
return EXIT_FAILURE;
if ( !alarmstarted && ( TIMEOUT > 0 )) {
alarm ( TIMEOUT );
alarmstarted = 1;
}
if (!( pw = getpwnam ( username ))) {
pw_copy.pw_name = "UNKNOWN";
pw_copy.pw_passwd = "!";
opt_fflag = 0;
failed = 1;
} else
pw_copy = *pw;
pw = &pw_copy;
if (( pw-> pw_passwd [0] == '!' ) || ( pw-> pw_passwd[0] == '*' ))
failed = 1;
if ( opt_fflag ) {
opt_fflag = 0;
goto auth_ok;
}
if (!failed && ( pw-> pw_uid == 0 ) && ( !check_tty ( tty )))
failed = 1;
/* Don't check the password if password entry is empty (!) */
if ( !pw-> pw_passwd[0] )
goto auth_ok;
/* authorization takes place here */
if ( correct_password ( pw ))
goto auth_ok;
failed = 1;
auth_ok:
if ( !failed)
break;
bb_do_delay(FAIL_DELAY);
puts("Login incorrect");
username[0] = 0;
if ( ++count == 3 ) {
syslog ( LOG_WARNING, "invalid password for `%s'%s\n", pw->pw_name, fromhost);
return EXIT_FAILURE;
}
}
alarm ( 0 );
if ( check_nologin ( pw-> pw_uid == 0 ))
return EXIT_FAILURE;
#ifdef CONFIG_FEATURE_UTMP
setutmp ( username, tty );
#endif
if ( *tty != '/' )
snprintf ( full_tty, sizeof( full_tty ) - 1, "/dev/%s", tty);
else
safe_strncpy ( full_tty, tty, sizeof( full_tty ) - 1 );
#ifdef CONFIG_SELINUX
if (is_selinux_enabled())
{
security_context_t old_tty_sid, new_tty_sid;
if (get_default_context(username, NULL, &user_sid))
{
fprintf(stderr, "Unable to get SID for %s\n", username);
exit(1);
}
if (getfilecon(full_tty, &old_tty_sid) < 0)
{
fprintf(stderr, "getfilecon(%.100s) failed: %.100s\n", full_tty, strerror(errno));
return EXIT_FAILURE;
}
if (security_compute_relabel(user_sid, old_tty_sid, SECCLASS_CHR_FILE, &new_tty_sid) != 0)
{
fprintf(stderr, "security_change_sid(%.100s) failed: %.100s\n", full_tty, strerror(errno));
return EXIT_FAILURE;
}
if(setfilecon(full_tty, new_tty_sid) != 0)
{
fprintf(stderr, "chsid(%.100s, %s) failed: %.100s\n", full_tty, new_tty_sid, strerror(errno));
return EXIT_FAILURE;
}
}
#endif
if ( !is_my_tty ( full_tty ))
syslog ( LOG_ERR, "unable to determine TTY name, got %s\n", full_tty );
/* Try these, but don't complain if they fail
* (for example when the root fs is read only) */
chown ( full_tty, pw-> pw_uid, pw-> pw_gid );
chmod ( full_tty, 0600 );
change_identity ( pw );
tmp = pw-> pw_shell;
if(!tmp || !*tmp)
tmp = DEFAULT_SHELL;
setup_environment ( tmp, 1, !opt_preserve, pw );
motd ( );
signal ( SIGALRM, SIG_DFL ); /* default alarm signal */
if ( pw-> pw_uid == 0 )
syslog ( LOG_INFO, "root login %s\n", fromhost );
#ifdef CONFIG_SELINUX
/* well, a simple setexeccon() here would do the job as well,
* but let's play the game for now */
set_current_security_context(user_sid);
#endif
run_shell ( tmp, 1, 0, 0); /* exec the shell finally. */
return EXIT_FAILURE;
}
static int login_prompt ( char *buf_name )
{
char buf [1024];
char *sp, *ep;
int i;
for(i=0; i<EMPTY_USERNAME_COUNT; i++) {
print_login_prompt();
if ( !fgets ( buf, sizeof( buf ) - 1, stdin ))
return 0;
if ( !strchr ( buf, '\n' ))
return 0;
for ( sp = buf; isspace ( *sp ); sp++ ) { }
for ( ep = sp; isgraph ( *ep ); ep++ ) { }
*ep = 0;
safe_strncpy(buf_name, sp, USERNAME_SIZE);
if(buf_name[0])
return 1;
}
return 0;
}
static int check_nologin ( int amroot )
{
if ( access ( bb_path_nologin_file, F_OK ) == 0 ) {
FILE *fp;
int c;
if (( fp = fopen ( bb_path_nologin_file, "r" ))) {
while (( c = getc ( fp )) != EOF )
putchar (( c == '\n' ) ? '\r' : c );
fflush ( stdout );
fclose ( fp );
} else {
puts ( "\r\nSystem closed for routine maintenance.\r" );
}
if ( !amroot )
return 1;
puts ( "\r\n[Disconnect bypassed -- root login allowed.]\r" );
}
return 0;
}
#ifdef CONFIG_FEATURE_SECURETTY
static int check_tty ( const char *tty )
{
FILE *fp;
int i;
char buf[BUFSIZ];
if (( fp = fopen ( bb_path_securetty_file, "r" ))) {
while ( fgets ( buf, sizeof( buf ) - 1, fp )) {
for ( i = bb_strlen( buf ) - 1; i >= 0; --i ) {
if ( !isspace ( buf[i] ))
break;
}
buf[++i] = '\0';
if (( buf [0] == '\0' ) || ( buf [0] == '#' ))
continue;
if ( strcmp ( buf, tty ) == 0 ) {
fclose ( fp );
return 1;
}
}
fclose(fp);
return 0;
}
/* A missing securetty file is not an error. */
return 1;
}
#endif
/* returns 1 if true */
static int is_my_tty ( const char *tty )
{
struct stat by_name, by_fd;
if ( stat ( tty, &by_name ) || fstat ( 0, &by_fd ))
return 0;
if ( by_name. st_rdev != by_fd. st_rdev )
return 0;
else
return 1;
}
static void motd (void)
{
FILE *fp;
register int c;
if (( fp = fopen ( bb_path_motd_file, "r" ))) {
while (( c = getc ( fp )) != EOF )
putchar ( c );
fclose ( fp );
}
}
#ifdef CONFIG_FEATURE_UTMP
// vv Taken from tinylogin utmp.c vv
#define NO_UTENT \
"No utmp entry. You must exec \"login\" from the lowest level \"sh\""
#define NO_TTY \
"Unable to determine your tty name."
/*
* checkutmp - see if utmp file is correct for this process
*
* System V is very picky about the contents of the utmp file
* and requires that a slot for the current process exist.
* The utmp file is scanned for an entry with the same process
* ID. If no entry exists the process exits with a message.
*
* The "picky" flag is for network and other logins that may
* use special flags. It allows the pid checks to be overridden.
* This means that getty should never invoke login with any
* command line flags.
*/
static void checkutmp(int picky)
{
char *line;
struct utmp *ut;
pid_t pid = getpid();
setutent();
/* First, try to find a valid utmp entry for this process. */
while ((ut = getutent()))
if (ut->ut_pid == pid && ut->ut_line[0] && ut->ut_id[0] &&
(ut->ut_type == LOGIN_PROCESS || ut->ut_type == USER_PROCESS))
break;
/* If there is one, just use it, otherwise create a new one. */
if (ut) {
utent = *ut;
} else {
time_t t_tmp;
if (picky) {
puts(NO_UTENT);
exit(1);
}
line = ttyname(0);
if (!line) {
puts(NO_TTY);
exit(1);
}
if (strncmp(line, "/dev/", 5) == 0)
line += 5;
memset((void *) &utent, 0, sizeof utent);
utent.ut_type = LOGIN_PROCESS;
utent.ut_pid = pid;
strncpy(utent.ut_line, line, sizeof utent.ut_line);
/* XXX - assumes /dev/tty?? */
strncpy(utent.ut_id, utent.ut_line + 3, sizeof utent.ut_id);
strncpy(utent.ut_user, "LOGIN", sizeof utent.ut_user);
t_tmp = (time_t)utent.ut_time;
time(&t_tmp);
}
}
/*
* setutmp - put a USER_PROCESS entry in the utmp file
*
* setutmp changes the type of the current utmp entry to
* USER_PROCESS. the wtmp file will be updated as well.
*/
static void setutmp(const char *name, const char *line ATTRIBUTE_UNUSED)
{
time_t t_tmp = (time_t)utent.ut_time;
utent.ut_type = USER_PROCESS;
strncpy(utent.ut_user, name, sizeof utent.ut_user);
time(&t_tmp);
/* other fields already filled in by checkutmp above */
setutent();
pututline(&utent);
endutent();
#ifdef CONFIG_FEATURE_WTMP
if (access(_PATH_WTMP, R_OK|W_OK) == -1) {
close(creat(_PATH_WTMP, 0664));
}
updwtmp(_PATH_WTMP, &utent);
#endif
}
#endif /* CONFIG_FEATURE_UTMP */