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sysvinit/src/sulogin.c

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/*
* sulogin This program gives Linux machines a reasonable
* secure way to boot single user. It forces the
* user to supply the root password before a
* shell is started.
*
* If there is a shadow password file and the
* encrypted root password is "x" the shadow
* password will be used.
*
* Version: @(#)sulogin 2.85-3 23-Apr-2003 miquels@cistron.nl
*
* Copyright (C) 1998-2003 Miquel van Smoorenburg.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <pwd.h>
#include <shadow.h>
#include <termios.h>
#include <sys/ttydefaults.h>
#include <errno.h>
#include <sys/ioctl.h>
#if defined(__GLIBC__)
# include <crypt.h>
#endif
#ifdef WITH_SELINUX
# include <selinux/selinux.h>
# include <selinux/get_context_list.h>
#endif
#define CHECK_DES 1
#define CHECK_MD5 1
#define F_PASSWD "/etc/passwd"
#define F_SHADOW "/etc/shadow"
#define BINSH "/bin/sh"
#define STATICSH "/bin/sash"
char *Version = "@(#)sulogin 2.85-3 23-Apr-2003 miquels@cistron.nl";
static int timeout;
static int profile;
static void (*saved_sigint) = SIG_DFL;
static void (*saved_sigtstp) = SIG_DFL;
static void (*saved_sigquit) = SIG_DFL;
#ifndef IUCLC
# define IUCLC 0
#endif
#if defined(SANE_TIO) && (SANE_TIO == 1)
/*
* Fix the tty modes and set reasonable defaults.
* (I'm not sure if this is needed under Linux, but..)
*/
static
void fixtty(void)
{
struct termios tty;
int serial;
/* Skip serial console */
if (ioctl (0, TIOCMGET, (char*)&serial) == 0)
goto out;
/* Expected error */
serial = errno = 0;
tcgetattr(0, &tty);
/* Use defaults of <sys/ttydefaults.h> for base settings */
tty.c_iflag |= TTYDEF_IFLAG;
tty.c_oflag |= TTYDEF_OFLAG;
tty.c_lflag |= TTYDEF_LFLAG;
tty.c_cflag |= (TTYDEF_SPEED | TTYDEF_CFLAG);
/* Sane setting, allow eight bit characters, no carriage return delay
* the same result as `stty sane cr0 pass8'
*/
tty.c_iflag |= (BRKINT | ICRNL | IMAXBEL);
#ifdef IUTF8 /* Not defined on FreeBSD */
tty.c_iflag |= IUTF8;
#endif /* IUTF8 */
tty.c_iflag &= ~(IGNBRK | INLCR | IGNCR | IXOFF | IUCLC | IXANY | ISTRIP);
tty.c_oflag |= (OPOST | ONLCR | NL0 | CR0 | TAB0 | BS0 | VT0 | FF0);
tty.c_oflag &= ~(OLCUC | OCRNL | ONOCR | ONLRET | OFILL | OFDEL |\
NLDLY|CRDLY|TABDLY|BSDLY|VTDLY|FFDLY);
tty.c_lflag |= (ISIG | ICANON | IEXTEN | ECHO|ECHOE|ECHOK|ECHOCTL|ECHOKE);
tty.c_lflag &= ~(ECHONL | NOFLSH | XCASE | TOSTOP | ECHOPRT);
tty.c_cflag |= (CREAD | CS8 | B9600);
tty.c_cflag &= ~(PARENB);
/* VTIME and VMIN can overlap with VEOF and VEOL since they are
* only used for non-canonical mode. We just set the at the
* beginning, so nothing bad should happen.
*/
tty.c_cc[VTIME] = 0;
tty.c_cc[VMIN] = 1;
tty.c_cc[VINTR] = CINTR;
tty.c_cc[VQUIT] = CQUIT;
tty.c_cc[VERASE] = CERASE; /* ASCII DEL (0177) */
tty.c_cc[VKILL] = CKILL;
tty.c_cc[VEOF] = CEOF;
tty.c_cc[VSWTC] = _POSIX_VDISABLE;
tty.c_cc[VSTART] = CSTART;
tty.c_cc[VSTOP] = CSTOP;
tty.c_cc[VSUSP] = CSUSP;
tty.c_cc[VEOL] = _POSIX_VDISABLE;
tty.c_cc[VREPRINT] = CREPRINT;
tty.c_cc[VDISCARD] = CDISCARD;
tty.c_cc[VWERASE] = CWERASE;
tty.c_cc[VLNEXT] = CLNEXT;
tty.c_cc[VEOL2] = _POSIX_VDISABLE;
tcsetattr(0, TCSANOW, &tty);
out:
return;
}
#endif
/*
* Called at timeout.
*/
static
# ifdef __GNUC__
void alrm_handler(int sig __attribute__((unused)))
# else
void alrm_handler(int sig)
# endif
{
}
/*
* See if an encrypted password is valid. The encrypted
* password is checked for traditional-style DES and
* FreeBSD-style MD5 encryption.
*/
static
int valid(const char *pass)
{
const char *s;
char id[5];
size_t len;
off_t off;
if (pass[0] == 0) return 1;
#if CHECK_MD5
if (pass[0] != '$') goto check_des;
/*
* up to 4 bytes for the signature e.g. $1$
*/
for(s = pass+1; *s && *s != '$'; s++)
;
if (*s++ != '$') return 0;
if ((off = (off_t)(s-pass)) > 4 || off < 3) return 0;
memset(id, '\0', sizeof(id));
strncpy(id, pass, off);
/*
* up to 16 bytes for the salt
*/
for(; *s && *s != '$'; s++)
;
if (*s++ != '$') return 0;
if ((off_t)(s-pass) > 16) return 0;
len = strlen(s);
/*
* the MD5 hash (128 bits or 16 bytes) encoded in base64 = 22 bytes
*/
if ((strcmp(id, "$1$") == 0) && (len < 22 || len > 24)) return 0;
/*
* the SHA-256 hash 43 bytes
*/
if ((strcmp(id, "$5$") == 0) && (len < 42 || len > 44)) return 0;
/*
* the SHA-512 hash 86 bytes
*/
if ((strcmp(id, "$6$") == 0) && (len < 85 || len > 87)) return 0;
/*
* e.g. Blowfish hash
*/
return 1;
check_des:
#endif
#if CHECK_DES
if (strlen(pass) != 13) return 0;
for (s = pass; *s; s++) {
if ((*s < '0' || *s > '9') &&
(*s < 'a' || *s > 'z') &&
(*s < 'A' || *s > 'Z') &&
*s != '.' && *s != '/') return 0;
}
#endif
return 1;
}
/*
* Set a variable if the value is not NULL.
*/
static
void set(char **var, char *val)
{
if (val) *var = val;
}
/*
* Get the root password entry.
*/
static
struct passwd *getrootpwent(int try_manually)
{
static struct passwd pwd;
struct passwd *pw;
struct spwd *spw;
FILE *fp;
static char line[256];
static char sline[256];
char *p;
/*
* First, we try to get the password the standard
* way using normal library calls.
*/
if ((pw = getpwnam("root")) &&
!strcmp(pw->pw_passwd, "x") &&
(spw = getspnam("root")))
pw->pw_passwd = spw->sp_pwdp;
if (pw || !try_manually) return pw;
/*
* If we come here, we could not retrieve the root
* password through library calls and we try to
* read the password and shadow files manually.
*/
pwd.pw_name = "root";
pwd.pw_passwd = "";
pwd.pw_gecos = "Super User";
pwd.pw_dir = "/";
pwd.pw_shell = "";
pwd.pw_uid = 0;
pwd.pw_gid = 0;
if ((fp = fopen(F_PASSWD, "r")) == NULL) {
perror(F_PASSWD);
return &pwd;
}
/*
* Find root in the password file.
*/
while((p = fgets(line, 256, fp)) != NULL) {
if (strncmp(line, "root:", 5) != 0)
continue;
p += 5;
set(&pwd.pw_passwd, strsep(&p, ":"));
(void)strsep(&p, ":");
(void)strsep(&p, ":");
set(&pwd.pw_gecos, strsep(&p, ":"));
set(&pwd.pw_dir, strsep(&p, ":"));
set(&pwd.pw_shell, strsep(&p, "\n"));
p = line;
break;
}
fclose(fp);
/*
* If the encrypted password is valid
* or not found, return.
*/
if (p == NULL) {
fprintf(stderr, "%s: no entry for root\n", F_PASSWD);
return &pwd;
}
if (valid(pwd.pw_passwd)) return &pwd;
/*
* The password is invalid. If there is a
* shadow password, try it.
*/
strcpy(pwd.pw_passwd, "");
if ((fp = fopen(F_SHADOW, "r")) == NULL) {
fprintf(stderr, "%s: root password garbled\n", F_PASSWD);
return &pwd;
}
while((p = fgets(sline, 256, fp)) != NULL) {
if (strncmp(sline, "root:", 5) != 0)
continue;
p += 5;
set(&pwd.pw_passwd, strsep(&p, ":"));
break;
}
fclose(fp);
/*
* If the password is still invalid,
* NULL it, and return.
*/
if (p == NULL) {
fprintf(stderr, "%s: no entry for root\n", F_SHADOW);
strcpy(pwd.pw_passwd, "");
}
if (!valid(pwd.pw_passwd)) {
fprintf(stderr, "%s: root password garbled\n", F_SHADOW);
strcpy(pwd.pw_passwd, ""); }
return &pwd;
}
/*
* Ask for the password. Note that there is no
* default timeout as we normally skip this during boot.
*/
static
char *getpasswd(char *crypted)
{
struct sigaction sa;
struct termios old, tty;
static char pass[128];
char *ret = pass;
int i;
#if defined(USE_ONELINE)
if (crypted[0])
printf("Give root password for login: ");
else
printf("Press enter for login: ");
#else
if (crypted[0])
printf("Give root password for maintenance\n");
else
printf("Press enter for maintenance");
printf("(or type Control-D to continue): ");
#endif
fflush(stdout);
tcgetattr(0, &old);
tcgetattr(0, &tty);
tty.c_iflag &= ~(IUCLC|IXON|IXOFF|IXANY);
tty.c_lflag &= ~(ECHO|ECHOE|ECHOK|ECHONL|TOSTOP);
tcsetattr(0, TCSANOW, &tty);
pass[sizeof(pass) - 1] = 0;
sa.sa_handler = alrm_handler;
sa.sa_flags = 0;
sigaction(SIGALRM, &sa, NULL);
if (timeout) alarm(timeout);
if (read(0, pass, sizeof(pass) - 1) <= 0)
ret = NULL;
else {
for(i = 0; i < (int)sizeof(pass) && pass[i]; i++)
if (pass[i] == '\r' || pass[i] == '\n') {
pass[i] = 0;
break;
}
}
alarm(0);
tcsetattr(0, TCSANOW, &old);
printf("\n");
return ret;
}
/*
* Password was OK, execute a shell.
*/
static
void sushell(struct passwd *pwd)
{
char shell[128];
char home[128];
char *p;
char *sushell;
/*
* Set directory and shell.
*/
(void)chdir(pwd->pw_dir);
if ((p = getenv("SUSHELL")) != NULL)
sushell = p;
else if ((p = getenv("sushell")) != NULL)
sushell = p;
else {
if (pwd->pw_shell[0])
sushell = pwd->pw_shell;
else
sushell = BINSH;
}
if ((p = strrchr(sushell, '/')) == NULL)
p = sushell;
else
p++;
snprintf(shell, sizeof(shell), profile ? "-%s" : "%s", p);
/*
* Set some important environment variables.
*/
getcwd(home, sizeof(home));
setenv("HOME", home, 1);
setenv("LOGNAME", "root", 1);
setenv("USER", "root", 1);
if (!profile)
setenv("SHLVL","0",1);
/*
* Try to execute a shell.
*/
setenv("SHELL", sushell, 1);
signal(SIGINT, saved_sigint);
signal(SIGTSTP, saved_sigtstp);
signal(SIGQUIT, saved_sigquit);
#ifdef WITH_SELINUX
if (is_selinux_enabled() > 0) {
security_context_t scon=NULL;
char *seuser=NULL;
char *level=NULL;
if (getseuserbyname("root", &seuser, &level) == 0)
if (get_default_context_with_level(seuser, level, 0, &scon) == 0) {
if (setexeccon(scon) != 0)
fprintf(stderr, "setexeccon faile\n");
freecon(scon);
}
free(seuser);
free(level);
}
#endif
execl(sushell, shell, NULL);
perror(sushell);
setenv("SHELL", BINSH, 1);
execl(BINSH, profile ? "-sh" : "sh", NULL);
perror(BINSH);
/* Fall back to staticly linked shell if both the users shell
and /bin/sh failed to execute. */
setenv("SHELL", STATICSH, 1);
execl(STATICSH, STATICSH, NULL);
perror(STATICSH);
}
static
void usage(void)
{
fprintf(stderr, "Usage: sulogin [-e] [-p] [-t timeout] [tty device]\n");
}
int main(int argc, char **argv)
{
char *tty = NULL;
char *p;
struct passwd *pwd;
int c, fd = -1;
int opt_e = 0;
pid_t pid, pgrp, ppgrp, ttypgrp;
/*
* See if we have a timeout flag.
*/
opterr = 0;
while((c = getopt(argc, argv, "ept:")) != EOF) switch(c) {
case 't':
timeout = atoi(optarg);
break;
case 'p':
profile = 1;
break;
case 'e':
opt_e = 1;
break;
default:
usage();
/* Do not exit! */
break;
}
if (geteuid() != 0) {
fprintf(stderr, "sulogin: only root can run sulogin.\n");
exit(1);
}
/*
* See if we need to open an other tty device.
*/
saved_sigint = signal(SIGINT, SIG_IGN);
saved_sigtstp = signal(SIGQUIT, SIG_IGN);
saved_sigquit = signal(SIGTSTP, SIG_IGN);
if (optind < argc) tty = argv[optind];
if (tty || (tty = getenv("CONSOLE"))) {
if ((fd = open(tty, O_RDWR)) < 0) {
perror(tty);
fd = dup(0);
}
if (!isatty(fd)) {
fprintf(stderr, "%s: not a tty\n", tty);
close(fd);
} else {
/*
* Only go through this trouble if the new
* tty doesn't fall in this process group.
*/
pid = getpid();
pgrp = getpgid(0);
ppgrp = getpgid(getppid());
ttypgrp = tcgetpgrp(fd);
if (pgrp != ttypgrp && ppgrp != ttypgrp) {
if (pid != getsid(0)) {
if (pid == getpgid(0))
setpgid(0, getpgid(getppid()));
setsid();
}
signal(SIGHUP, SIG_IGN);
if (ttypgrp > 0)
ioctl(0, TIOCNOTTY, (char *)1);
signal(SIGHUP, SIG_DFL);
close(0);
close(1);
close(2);
if (fd > 2)
close(fd);
if ((fd = open(tty, O_RDWR|O_NOCTTY)) < 0) {
perror(tty);
} else {
ioctl(0, TIOCSCTTY, (char *)1);
tcsetpgrp(fd, ppgrp);
dup2(fd, 0);
dup2(fd, 1);
dup2(fd, 2);
if (fd > 2)
close(fd);
}
} else
if (fd > 2)
close(fd);
}
} else if (getpid() == 1) {
/* We are init. We hence need to set a session anyway */
setsid();
if (ioctl(0, TIOCSCTTY, (char *)1))
perror("ioctl(TIOCSCTTY)");
}
#if defined(SANE_TIO) && (SANE_TIO == 1)
fixtty();
#endif
/*
* Get the root password.
*/
if ((pwd = getrootpwent(opt_e)) == NULL) {
fprintf(stderr, "sulogin: cannot open password database!\n");
sleep(2);
}
/*
* Ask for the password.
*/
while(pwd) {
if ((p = getpasswd(pwd->pw_passwd)) == NULL) break;
if (pwd->pw_passwd[0] == 0 ||
strcmp(crypt(p, pwd->pw_passwd), pwd->pw_passwd) == 0)
sushell(pwd);
saved_sigquit = signal(SIGQUIT, SIG_IGN);
saved_sigtstp = signal(SIGTSTP, SIG_IGN);
saved_sigint = signal(SIGINT, SIG_IGN);
printf("Login incorrect.\n");
}
/*
* User pressed Control-D.
*/
return 0;
}
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