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sulogin: initial import from sysvinit 

Import the source and manpage of sulogin. Only the selinux #ifdef is
changed to match our autotool setup.

Signed-off-by: Dave Reisner <dreisner@archlinux.org>
This commit is contained in:
Dave Reisner 2012-02-28 11:45:10 -05:00 committed by Karel Zak
parent 208848ef27
commit 7d8a8d2cd9
3 changed files with 697 additions and 1 deletions
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6
login-utils/Makefile.am
View File

@ -14,6 +14,7 @@ endif
if BUILD_LOGIN_UTILS
bin_PROGRAMS += login
sbin_PROGRAMS += sulogin
usrbin_exec_PROGRAMS += \
chfn \
chsh \
@ -26,7 +27,8 @@ dist_man_MANS += \
login.1 \
newgrp.1 \
vigr.8 \
vipw.8
vipw.8 \
sulogin.8
# login, chfn and chsh libs
login_ldadd_common =
@ -57,6 +59,7 @@ chsh_LDADD = $(login_ldadd_common)
login_LDADD = $(login_ldadd_common)
newgrp_LDADD =
vipw_LDADD =
sulogin_LDADD =
chfn_CFLAGS = $(SUID_CFLAGS) $(AM_CFLAGS)
chsh_CFLAGS = $(SUID_CFLAGS) $(AM_CFLAGS)
@ -70,6 +73,7 @@ login_ldadd_common += -lpam -lpam_misc
if HAVE_LIBCRYPT
newgrp_LDADD += -lcrypt
sulogin_LDADD += -lcrypt
endif
if HAVE_AUDIT

87
login-utils/sulogin.8 Normal file
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@ -0,0 +1,87 @@
'\" -*- coding: UTF-8 -*-
.\" Copyright (C) 1998-2006 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
.\"
.TH SULOGIN 8 "17 Jan 2006" "" "Linux System Administrator's Manual"
.SH NAME
sulogin \- Single-user login
.SH SYNOPSIS
.B sulogin
[ \fB\-e\fP ]
[ \fB\-p\fP ]
[ \fB\-t\fP \fISECONDS\fP ]
[ \fITTY\fP ]
.SH DESCRIPTION
.I sulogin
is invoked by \fBinit(8)\fP when the system goes into single user mode.
(This is done through an entry in \fIinittab(5)\fP.)
\fBInit\fP also
tries to execute \fIsulogin\fP when
the boot loader (e.g., \fBgrub\fP(8))
passes it the \fB\-b\fP option.
.PP
The user is prompted
.IP "" .5i
Give root password for system maintenance
.br
(or type Control\-D for normal startup):
.PP
\fIsulogin\fP will be connected to the current terminal, or to the
optional device that can be specified on the command line
(typically \fB/dev/console\fP).
.PP
If the \fB\-t\fP option is used then the program only waits
the given number of seconds for user input.
.PP
If the \fB\-p\fP option is used then the single-user shell is invoked
with a \fIdash\fP as the first character in \fIargv[0]\fP.
This causes the shell process to behave as a login shell.
The default is \fInot\fP to do this,
so that the shell will \fInot\fP read \fB/etc/profile\fP
or \fB$HOME/.profile\fP at startup.
.PP
After the user exits the single-user shell,
or presses control\-D at the prompt,
the system will (continue to) boot to the default runlevel.
.SH ENVIRONMENT VARIABLES
\fIsulogin\fP looks for the environment variable \fBSUSHELL\fP or
\fBsushell\fP to determine what shell to start. If the environment variable
is not set, it will try to execute root's shell from /etc/passwd. If that
fails it will fall back to \fB/bin/sh\fP.
.PP
This is very valuable together with the \fB\-b\fP option to init. To boot
the system into single user mode, with the root file system mounted read/write,
using a special "fail safe" shell that is statically linked (this example
is valid for the LILO bootprompt)
.PP
boot: linux \-b rw sushell=/sbin/sash
.SH FALLBACK METHODS
\fIsulogin\fP checks the root password using the standard method (getpwnam)
first.
Then, if the \fB\-e\fP option was specified,
\fIsulogin\fP examines these files directly to find the root password:
.PP
/etc/passwd,
.br
/etc/shadow (if present)
.PP
If they are damaged or nonexistent, sulogin will start a root shell
without asking for a password. Only use the \fB\-e\fP option if you
are sure the console is physically protected against unauthorized access.
.SH AUTHOR
Miquel van Smoorenburg <miquels@cistron.nl>
.SH SEE ALSO
init(8), inittab(5).

605
login-utils/sulogin.c Normal file
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@ -0,0 +1,605 @@
/*
* 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 HAVE_LIBSELINUX
# 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"
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;
}