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|
/*
* su(1) for Linux. Run a shell with substitute user and group IDs.
*
* Copyright (C) 1992-2006 Free Software Foundation, Inc.
* Copyright (C) 2012 SUSE Linux Products GmbH, Nuernberg
* Copyright (C) 2016-2017 Karel Zak <kzak@redhat.com>
*
* 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, 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.
*
*
* Based on an implementation by David MacKenzie <djm@gnu.ai.mit.edu>.
*/
#include <stdio.h>
#include <getopt.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
#include <security/pam_appl.h>
#ifdef HAVE_SECURITY_PAM_MISC_H
# include <security/pam_misc.h>
#elif defined(HAVE_SECURITY_OPENPAM_H)
# include <security/openpam.h>
#endif
#include <signal.h>
#include <sys/wait.h>
#include <syslog.h>
#include <utmpx.h>
#if defined(HAVE_LIBUTIL) && defined(HAVE_PTY_H) && defined(HAVE_SYS_SIGNALFD_H)
# include <pty.h>
# include <poll.h>
# include <sys/signalfd.h>
# include "all-io.h"
# define USE_PTY
#endif
#include "err.h"
#include <stdbool.h>
#include "c.h"
#include "xalloc.h"
#include "nls.h"
#include "pathnames.h"
#include "env.h"
#include "closestream.h"
#include "strv.h"
#include "strutils.h"
#include "ttyutils.h"
#include "pwdutils.h"
#include "optutils.h"
#include "logindefs.h"
#include "su-common.h"
#include "debug.h"
UL_DEBUG_DEFINE_MASK(su);
UL_DEBUG_DEFINE_MASKNAMES(su) = UL_DEBUG_EMPTY_MASKNAMES;
#define SU_DEBUG_INIT (1 << 1)
#define SU_DEBUG_PAM (1 << 2)
#define SU_DEBUG_PARENT (1 << 3)
#define SU_DEBUG_TTY (1 << 4)
#define SU_DEBUG_LOG (1 << 5)
#define SU_DEBUG_MISC (1 << 6)
#define SU_DEBUG_SIG (1 << 7)
#define SU_DEBUG_PTY (1 << 8)
#define SU_DEBUG_ALL 0xFFFF
#define DBG(m, x) __UL_DBG(su, SU_DEBUG_, m, x)
#define ON_DBG(m, x) __UL_DBG_CALL(su, SU_DEBUG_, m, x)
/* name of the pam configuration files. separate configs for su and su - */
#define PAM_SRVNAME_SU "su"
#define PAM_SRVNAME_SU_L "su-l"
#define PAM_SRVNAME_RUNUSER "runuser"
#define PAM_SRVNAME_RUNUSER_L "runuser-l"
#define _PATH_LOGINDEFS_SU "/etc/default/su"
#define _PATH_LOGINDEFS_RUNUSER "/etc/default/runuser"
#define is_pam_failure(_rc) ((_rc) != PAM_SUCCESS)
/* The shell to run if none is given in the user's passwd entry. */
#define DEFAULT_SHELL "/bin/sh"
/* The user to become if none is specified. */
#define DEFAULT_USER "root"
#ifndef HAVE_ENVIRON_DECL
extern char **environ;
#endif
enum {
SIGTERM_IDX = 0,
SIGINT_IDX,
SIGQUIT_IDX,
SIGNALS_IDX_COUNT
};
/*
* su/runuser control struct
*/
struct su_context {
pam_handle_t *pamh; /* PAM handler */
struct pam_conv conv; /* PAM conversation */
struct passwd *pwd; /* new user info */
char *pwdbuf; /* pwd strings */
const char *tty_name; /* tty_path without /dev prefix */
const char *tty_number; /* end of the tty_path */
char *new_user; /* wanted user */
char *old_user; /* original user */
pid_t child; /* fork() baby */
int childstatus; /* wait() status */
char **env_whitelist_names; /* environment whitelist */
char **env_whitelist_vals;
struct sigaction oldact[SIGNALS_IDX_COUNT]; /* original sigactions indexed by SIG*_IDX */
#ifdef USE_PTY
struct termios stdin_attrs; /* stdin and slave terminal runtime attributes */
int pty_master;
int pty_slave;
int pty_sigfd; /* signalfd() */
int poll_timeout;
struct winsize win; /* terminal window size */
sigset_t oldsig; /* original signal mask */
#endif
unsigned int runuser :1, /* flase=su, true=runuser */
runuser_uopt :1, /* runuser -u specified */
isterm :1, /* is stdin terminal? */
fast_startup :1, /* pass the `-f' option to the subshell. */
simulate_login :1, /* simulate a login instead of just starting a shell. */
change_environment :1, /* change some environment vars to indicate the user su'd to.*/
same_session :1, /* don't call setsid() with a command. */
suppress_pam_info:1, /* don't print PAM info messages (Last login, etc.). */
pam_has_session :1, /* PAM session opened */
pam_has_cred :1, /* PAM cred established */
pty :1, /* create pseudo-terminal */
restricted :1; /* false for root user */
};
static sig_atomic_t volatile caught_signal = false;
/* Signal handler for parent process. */
static void
su_catch_sig(int sig)
{
caught_signal = sig;
}
static void su_init_debug(void)
{
__UL_INIT_DEBUG_FROM_ENV(su, SU_DEBUG_, 0, SU_DEBUG);
}
static void init_tty(struct su_context *su)
{
su->isterm = isatty(STDIN_FILENO) ? 1 : 0;
DBG(TTY, ul_debug("initialize [is-term=%s]", su->isterm ? "true" : "false"));
if (su->isterm)
get_terminal_name(NULL, &su->tty_name, &su->tty_number);
}
/*
* Note, this function has to be possible call more than once. If the child is
* already dead than it returns saved result from the previous call.
*/
static int wait_for_child(struct su_context *su)
{
pid_t pid = (pid_t) -1;;
int status = 0;
if (su->child == (pid_t) -1)
return su->childstatus;
if (su->child != (pid_t) -1) {
/*
* The "su" parent process spends all time here in waitpid(),
* but "su --pty" uses pty_proxy_master() and waitpid() is only
* called to pick up child status or to react to SIGSTOP.
*/
DBG(SIG, ul_debug("waiting for child [%d]...", su->child));
for (;;) {
pid = waitpid(su->child, &status, WUNTRACED);
if (pid != (pid_t) - 1 && WIFSTOPPED(status)) {
DBG(SIG, ul_debug(" child got SIGSTOP -- stop all session"));
kill(getpid(), SIGSTOP);
/* once we get here, we must have resumed */
kill(pid, SIGCONT);
DBG(SIG, ul_debug(" session resumed -- continue"));
#ifdef USE_PTY
/* Let's go back to pty_proxy_master() */
if (su->pty_sigfd != -1) {
DBG(SIG, ul_debug(" leaving on child SIGSTOP"));
return 0;
}
#endif
} else
break;
}
}
if (pid != (pid_t) -1) {
if (WIFSIGNALED(status)) {
fprintf(stderr, "%s%s\n",
strsignal(WTERMSIG(status)),
WCOREDUMP(status) ? _(" (core dumped)")
: "");
status = WTERMSIG(status) + 128;
} else
status = WEXITSTATUS(status);
DBG(SIG, ul_debug("child %d is dead", su->child));
su->child = (pid_t) -1; /* Don't use the PID anymore! */
su->childstatus = status;
} else if (caught_signal)
status = caught_signal + 128;
else
status = 1;
DBG(SIG, ul_debug("child status=%d", status));
return status;
}
#ifdef USE_PTY
static void pty_init_slave(struct su_context *su)
{
DBG(PTY, ul_debug("initialize slave"));
ioctl(su->pty_slave, TIOCSCTTY, 1);
close(su->pty_master);
dup2(su->pty_slave, STDIN_FILENO);
dup2(su->pty_slave, STDOUT_FILENO);
dup2(su->pty_slave, STDERR_FILENO);
close(su->pty_slave);
close(su->pty_sigfd);
su->pty_slave = -1;
su->pty_master = -1;
su->pty_sigfd = -1;
sigprocmask(SIG_SETMASK, &su->oldsig, NULL);
DBG(PTY, ul_debug("... initialize slave done"));
}
static void pty_create(struct su_context *su)
{
struct termios slave_attrs;
int rc;
if (su->isterm) {
DBG(PTY, ul_debug("create for terminal"));
/* original setting of the current terminal */
if (tcgetattr(STDIN_FILENO, &su->stdin_attrs) != 0)
err(EXIT_FAILURE, _("failed to get terminal attributes"));
ioctl(STDIN_FILENO, TIOCGWINSZ, (char *)&su->win);
/* create master+slave */
rc = openpty(&su->pty_master, &su->pty_slave, NULL, &su->stdin_attrs, &su->win);
/* set the current terminal to raw mode; pty_cleanup() reverses this change on exit */
slave_attrs = su->stdin_attrs;
cfmakeraw(&slave_attrs);
slave_attrs.c_lflag &= ~ECHO;
tcsetattr(STDIN_FILENO, TCSANOW, &slave_attrs);
} else {
DBG(PTY, ul_debug("create for non-terminal"));
rc = openpty(&su->pty_master, &su->pty_slave, NULL, NULL, NULL);
if (!rc) {
tcgetattr(su->pty_slave, &slave_attrs);
slave_attrs.c_lflag &= ~ECHO;
tcsetattr(su->pty_slave, TCSANOW, &slave_attrs);
}
}
if (rc < 0)
err(EXIT_FAILURE, _("failed to create pseudo-terminal"));
DBG(PTY, ul_debug("pty setup done [master=%d, slave=%d]", su->pty_master, su->pty_slave));
}
static void pty_cleanup(struct su_context *su)
{
struct termios rtt;
if (su->pty_master == -1 || !su->isterm)
return;
DBG(PTY, ul_debug("cleanup"));
rtt = su->stdin_attrs;
tcsetattr(STDIN_FILENO, TCSADRAIN, &rtt);
}
static int write_output(char *obuf, ssize_t bytes)
{
DBG(PTY, ul_debug(" writing output"));
if (write_all(STDOUT_FILENO, obuf, bytes)) {
DBG(PTY, ul_debug(" writing output *failed*"));
warn(_("write failed"));
return -errno;
}
return 0;
}
static int write_to_child(struct su_context *su,
char *buf, size_t bufsz)
{
return write_all(su->pty_master, buf, bufsz);
}
/*
* The su(1) is usually faster than shell, so it's a good idea to wait until
* the previous message has been already read by shell from slave before we
* write to master. This is necessary especially for EOF situation when we can
* send EOF to master before shell is fully initialized, to workaround this
* problem we wait until slave is empty. For example:
*
* echo "date" | su
*
* Unfortunately, the child (usually shell) can ignore stdin at all, so we
* don't wait forever to avoid dead locks...
*
* Note that su --pty is primarily designed for interactive sessions as it
* maintains master+slave tty stuff within the session. Use pipe to write to
* su(1) and assume non-interactive (tee-like) behavior is NOT well
* supported.
*/
static void write_eof_to_child(struct su_context *su)
{
unsigned int tries = 0;
struct pollfd fds[] = {
{ .fd = su->pty_slave, .events = POLLIN }
};
char c = DEF_EOF;
DBG(PTY, ul_debug(" waiting for empty slave"));
while (poll(fds, 1, 10) == 1 && tries < 8) {
DBG(PTY, ul_debug(" slave is not empty"));
xusleep(250000);
tries++;
}
if (tries < 8)
DBG(PTY, ul_debug(" slave is empty now"));
DBG(PTY, ul_debug(" sending EOF to master"));
write_to_child(su, &c, sizeof(char));
}
static int pty_handle_io(struct su_context *su, int fd, int *eof)
{
char buf[BUFSIZ];
ssize_t bytes;
DBG(PTY, ul_debug("%d FD active", fd));
*eof = 0;
/* read from active FD */
bytes = read(fd, buf, sizeof(buf));
if (bytes < 0) {
if (errno == EAGAIN || errno == EINTR)
return 0;
return -errno;
}
if (bytes == 0) {
*eof = 1;
return 0;
}
/* from stdin (user) to command */
if (fd == STDIN_FILENO) {
DBG(PTY, ul_debug(" stdin --> master %zd bytes", bytes));
if (write_to_child(su, buf, bytes)) {
warn(_("write failed"));
return -errno;
}
/* without sync write_output() will write both input &
* shell output that looks like double echoing */
fdatasync(su->pty_master);
/* from command (master) to stdout */
} else if (fd == su->pty_master) {
DBG(PTY, ul_debug(" master --> stdout %zd bytes", bytes));
write_output(buf, bytes);
}
return 0;
}
static int pty_handle_signal(struct su_context *su, int fd)
{
struct signalfd_siginfo info;
ssize_t bytes;
DBG(SIG, ul_debug("signal FD %d active", fd));
bytes = read(fd, &info, sizeof(info));
if (bytes != sizeof(info)) {
if (bytes < 0 && (errno == EAGAIN || errno == EINTR))
return 0;
return -errno;
}
switch (info.ssi_signo) {
case SIGCHLD:
DBG(SIG, ul_debug(" get signal SIGCHLD"));
/* The child terminated or stopped. Note that we ignore SIGCONT
* here, because stop/cont semantic is handled by wait_for_child() */
if (info.ssi_code == CLD_EXITED
|| info.ssi_code == CLD_KILLED
|| info.ssi_code == CLD_DUMPED
|| info.ssi_status == SIGSTOP)
wait_for_child(su);
/* The child is dead, force poll() timeout. */
if (su->child == (pid_t) -1)
su->poll_timeout = 10;
return 0;
case SIGWINCH:
DBG(SIG, ul_debug(" get signal SIGWINCH"));
if (su->isterm) {
ioctl(STDIN_FILENO, TIOCGWINSZ, (char *)&su->win);
ioctl(su->pty_slave, TIOCSWINSZ, (char *)&su->win);
}
break;
case SIGTERM:
/* fallthrough */
case SIGINT:
/* fallthrough */
case SIGQUIT:
DBG(SIG, ul_debug(" get signal SIG{TERM,INT,QUIT}"));
caught_signal = info.ssi_signo;
/* Child termination is going to generate SIGCHILD (see above) */
kill(su->child, SIGTERM);
break;
default:
abort();
}
return 0;
}
static void pty_proxy_master(struct su_context *su)
{
sigset_t ourset;
int rc = 0, ret, eof = 0;
enum {
POLLFD_SIGNAL = 0,
POLLFD_MASTER,
POLLFD_STDIN
};
struct pollfd pfd[] = {
[POLLFD_SIGNAL] = { .fd = -1, .events = POLLIN | POLLERR | POLLHUP },
[POLLFD_MASTER] = { .fd = su->pty_master, .events = POLLIN | POLLERR | POLLHUP },
[POLLFD_STDIN] = { .fd = STDIN_FILENO, .events = POLLIN | POLLERR | POLLHUP }
};
/* for PTY mode we use signalfd
*
* TODO: script(1) initializes this FD before fork, good or bad idea?
*/
sigfillset(&ourset);
if (sigprocmask(SIG_BLOCK, &ourset, NULL)) {
warn(_("cannot block signals"));
caught_signal = true;
return;
}
sigemptyset(&ourset);
sigaddset(&ourset, SIGCHLD);
sigaddset(&ourset, SIGWINCH);
sigaddset(&ourset, SIGALRM);
sigaddset(&ourset, SIGTERM);
sigaddset(&ourset, SIGINT);
sigaddset(&ourset, SIGQUIT);
if ((su->pty_sigfd = signalfd(-1, &ourset, SFD_CLOEXEC)) < 0) {
warn(("cannot create signal file descriptor"));
caught_signal = true;
return;
}
pfd[POLLFD_SIGNAL].fd = su->pty_sigfd;
su->poll_timeout = -1;
while (!caught_signal) {
size_t i;
int errsv;
DBG(PTY, ul_debug("calling poll()"));
/* wait for input or signal */
ret = poll(pfd, ARRAY_SIZE(pfd), su->poll_timeout);
errsv = errno;
DBG(PTY, ul_debug("poll() rc=%d", ret));
if (ret < 0) {
if (errsv == EAGAIN)
continue;
warn(_("poll failed"));
break;
}
if (ret == 0) {
DBG(PTY, ul_debug("leaving poll() loop [timeout=%d]", su->poll_timeout));
break;
}
for (i = 0; i < ARRAY_SIZE(pfd); i++) {
rc = 0;
if (pfd[i].revents == 0)
continue;
DBG(PTY, ul_debug(" active pfd[%s].fd=%d %s %s %s",
i == POLLFD_STDIN ? "stdin" :
i == POLLFD_MASTER ? "master" :
i == POLLFD_SIGNAL ? "signal" : "???",
pfd[i].fd,
pfd[i].revents & POLLIN ? "POLLIN" : "",
pfd[i].revents & POLLHUP ? "POLLHUP" : "",
pfd[i].revents & POLLERR ? "POLLERR" : ""));
switch (i) {
case POLLFD_STDIN:
case POLLFD_MASTER:
/* data */
if (pfd[i].revents & POLLIN)
rc = pty_handle_io(su, pfd[i].fd, &eof);
/* EOF maybe detected by two ways:
* A) poll() return POLLHUP event after close()
* B) read() returns 0 (no data) */
if ((pfd[i].revents & POLLHUP) || eof) {
DBG(PTY, ul_debug(" ignore FD"));
pfd[i].fd = -1;
if (i == POLLFD_STDIN) {
write_eof_to_child(su);
DBG(PTY, ul_debug(" ignore STDIN"));
}
}
continue;
case POLLFD_SIGNAL:
rc = pty_handle_signal(su, pfd[i].fd);
break;
}
if (rc)
break;
}
}
close(su->pty_sigfd);
su->pty_sigfd = -1;
DBG(PTY, ul_debug("poll() done [signal=%d, rc=%d]", caught_signal, rc));
}
#endif /* USE_PTY */
/* Log the fact that someone has run su to the user given by PW;
if SUCCESSFUL is true, they gave the correct password, etc. */
static void log_syslog(struct su_context *su, bool successful)
{
DBG(LOG, ul_debug("syslog logging"));
openlog(program_invocation_short_name, 0, LOG_AUTH);
syslog(LOG_NOTICE, "%s(to %s) %s on %s",
successful ? "" :
su->runuser ? "FAILED RUNUSER " : "FAILED SU ",
su->new_user, su->old_user ? : "",
su->tty_name ? : "none");
closelog();
}
/*
* Log failed login attempts in _PATH_BTMP if that exists.
*/
static void log_btmp(struct su_context *su)
{
struct utmpx ut;
struct timeval tv;
DBG(LOG, ul_debug("btmp logging"));
memset(&ut, 0, sizeof(ut));
str2memcpy(ut.ut_user,
su->pwd && su->pwd->pw_name ? su->pwd->pw_name : "(unknown)",
sizeof(ut.ut_user));
if (su->tty_number)
str2memcpy(ut.ut_id, su->tty_number, sizeof(ut.ut_id));
if (su->tty_name)
str2memcpy(ut.ut_line, su->tty_name, sizeof(ut.ut_line));
gettimeofday(&tv, NULL);
ut.ut_tv.tv_sec = tv.tv_sec;
ut.ut_tv.tv_usec = tv.tv_usec;
ut.ut_type = LOGIN_PROCESS; /* XXX doesn't matter */
ut.ut_pid = getpid();
updwtmpx(_PATH_BTMP, &ut);
}
static int supam_conv( int num_msg,
const struct pam_message **msg,
struct pam_response **resp,
void *data)
{
struct su_context *su = (struct su_context *) data;
if (su->suppress_pam_info
&& num_msg == 1
&& msg && msg[0]->msg_style == PAM_TEXT_INFO)
return PAM_SUCCESS;
#ifdef HAVE_SECURITY_PAM_MISC_H
return misc_conv(num_msg, msg, resp, data);
#elif defined(HAVE_SECURITY_OPENPAM_H)
return openpam_ttyconv(num_msg, msg, resp, data);
#endif
}
static void supam_cleanup(struct su_context *su, int retcode)
{
const int errsv = errno;
DBG(PAM, ul_debug("cleanup"));
if (su->pam_has_session)
pam_close_session(su->pamh, 0);
if (su->pam_has_cred)
pam_setcred(su->pamh, PAM_DELETE_CRED | PAM_SILENT);
pam_end(su->pamh, retcode);
errno = errsv;
}
static void supam_export_environment(struct su_context *su)
{
char **env;
DBG(PAM, ul_debug("init environ[]"));
/* This is a copy but don't care to free as we exec later anyways. */
env = pam_getenvlist(su->pamh);
while (env && *env) {
if (putenv(*env) != 0)
err(EXIT_FAILURE, _("failed to modify environment"));
env++;
}
}
static void supam_authenticate(struct su_context *su)
{
const char *srvname = NULL;
int rc;
srvname = su->runuser ?
(su->simulate_login ? PAM_SRVNAME_RUNUSER_L : PAM_SRVNAME_RUNUSER) :
(su->simulate_login ? PAM_SRVNAME_SU_L : PAM_SRVNAME_SU);
DBG(PAM, ul_debug("start [name: %s]", srvname));
rc = pam_start(srvname, su->pwd->pw_name, &su->conv, &su->pamh);
if (is_pam_failure(rc))
goto done;
if (su->tty_name) {
rc = pam_set_item(su->pamh, PAM_TTY, su->tty_name);
if (is_pam_failure(rc))
goto done;
}
if (su->old_user) {
rc = pam_set_item(su->pamh, PAM_RUSER, (const void *) su->old_user);
if (is_pam_failure(rc))
goto done;
}
if (su->runuser) {
/*
* This is the only difference between runuser(1) and su(1). The command
* runuser(1) does not required authentication, because user is root.
*/
if (su->restricted)
errx(EXIT_FAILURE, _("may not be used by non-root users"));
return;
}
rc = pam_authenticate(su->pamh, 0);
if (is_pam_failure(rc))
goto done;
/* Check password expiration and offer option to change it. */
rc = pam_acct_mgmt(su->pamh, 0);
if (rc == PAM_NEW_AUTHTOK_REQD)
rc = pam_chauthtok(su->pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
done:
log_syslog(su, !is_pam_failure(rc));
if (is_pam_failure(rc)) {
const char *msg;
DBG(PAM, ul_debug("authentication failed"));
log_btmp(su);
msg = pam_strerror(su->pamh, rc);
pam_end(su->pamh, rc);
sleep(getlogindefs_num("FAIL_DELAY", 1));
errx(EXIT_FAILURE, "%s", msg ? msg : _("authentication failed"));
}
}
static void supam_open_session(struct su_context *su)
{
int rc;
DBG(PAM, ul_debug("opening session"));
rc = pam_open_session(su->pamh, 0);
if (is_pam_failure(rc)) {
supam_cleanup(su, rc);
errx(EXIT_FAILURE, _("cannot open session: %s"),
pam_strerror(su->pamh, rc));
} else
su->pam_has_session = 1;
}
static void parent_setup_signals(struct su_context *su)
{
sigset_t ourset;
/*
* Signals setup
*
* 1) block all signals
*/
DBG(SIG, ul_debug("initialize signals"));
sigfillset(&ourset);
if (sigprocmask(SIG_BLOCK, &ourset, NULL)) {
warn(_("cannot block signals"));
caught_signal = true;
}
if (!caught_signal) {
struct sigaction action;
action.sa_handler = su_catch_sig;
sigemptyset(&action.sa_mask);
action.sa_flags = 0;
sigemptyset(&ourset);
/* 2a) add wanted signals to the mask (for session) */
if (!su->same_session
&& (sigaddset(&ourset, SIGINT)
|| sigaddset(&ourset, SIGQUIT))) {
warn(_("cannot initialize signal mask for session"));
caught_signal = true;
}
/* 2b) add wanted generic signals to the mask */
if (!caught_signal
&& (sigaddset(&ourset, SIGTERM)
|| sigaddset(&ourset, SIGALRM))) {
warn(_("cannot initialize signal mask"));
caught_signal = true;
}
/* 3a) set signal handlers (for session) */
if (!caught_signal
&& !su->same_session
&& (sigaction(SIGINT, &action, &su->oldact[SIGINT_IDX])
|| sigaction(SIGQUIT, &action, &su->oldact[SIGQUIT_IDX]))) {
warn(_("cannot set signal handler for session"));
caught_signal = true;
}
/* 3b) set signal handlers */
if (!caught_signal
&& sigaction(SIGTERM, &action, &su->oldact[SIGTERM_IDX])) {
warn(_("cannot set signal handler"));
caught_signal = true;
}
/* 4) unblock wanted signals */
if (!caught_signal
&& sigprocmask(SIG_UNBLOCK, &ourset, NULL)) {
warn(_("cannot set signal mask"));
caught_signal = true;
}
}
}
static void create_watching_parent(struct su_context *su)
{
int status;
DBG(MISC, ul_debug("forking..."));
#ifdef USE_PTY
/* no-op, just save original signal mask to oldsig */
sigprocmask(SIG_BLOCK, NULL, &su->oldsig);
if (su->pty)
pty_create(su);
#endif
fflush(stdout); /* ??? */
switch ((int) (su->child = fork())) {
case -1: /* error */
supam_cleanup(su, PAM_ABORT);
#ifdef USE_PTY
if (su->pty)
pty_cleanup(su);
#endif
err(EXIT_FAILURE, _("cannot create child process"));
break;
case 0: /* child */
return;
default: /* parent */
DBG(MISC, ul_debug("child [pid=%d]", (int) su->child));
break;
}
/* free unnecessary stuff */
free_getlogindefs_data();
/* In the parent watch the child. */
/* su without pam support does not have a helper that keeps
sitting on any directory so let's go to /. */
if (chdir("/") != 0)
warn(_("cannot change directory to %s"), "/");
#ifdef USE_PTY
if (su->pty)
pty_proxy_master(su);
else
#endif
parent_setup_signals(su);
/*
* Wait for child
*/
if (!caught_signal)
status = wait_for_child(su);
else
status = 1;
DBG(SIG, ul_debug("final child status=%d", status));
if (caught_signal && su->child != (pid_t)-1) {
fprintf(stderr, _("\nSession terminated, killing shell..."));
kill(su->child, SIGTERM);
}
supam_cleanup(su, PAM_SUCCESS);
if (caught_signal) {
if (su->child != (pid_t)-1) {
DBG(SIG, ul_debug("killing child"));
sleep(2);
kill(su->child, SIGKILL);
fprintf(stderr, _(" ...killed.\n"));
}
/* Let's terminate itself with the received signal.
*
* It seems that shells use WIFSIGNALED() rather than our exit status
* value to detect situations when is necessary to cleanup (reset)
* terminal settings (kzak -- Jun 2013).
*/
DBG(SIG, ul_debug("restore signals setting"));
switch (caught_signal) {
case SIGTERM:
sigaction(SIGTERM, &su->oldact[SIGTERM_IDX], NULL);
break;
case SIGINT:
sigaction(SIGINT, &su->oldact[SIGINT_IDX], NULL);
break;
case SIGQUIT:
sigaction(SIGQUIT, &su->oldact[SIGQUIT_IDX], NULL);
break;
default:
/* just in case that signal stuff initialization failed and
* caught_signal = true */
caught_signal = SIGKILL;
break;
}
DBG(SIG, ul_debug("self-send %d signal", caught_signal));
kill(getpid(), caught_signal);
}
#ifdef USE_PTY
if (su->pty)
pty_cleanup(su);
#endif
DBG(MISC, ul_debug("exiting [rc=%d]", status));
exit(status);
}
/* Adds @name from the current environment to the whitelist. If @name is not
* set then nothing is added to the whitelist and returns 1.
*/
static int env_whitelist_add(struct su_context *su, const char *name)
{
const char *env = getenv(name);
if (!env)
return 1;
if (strv_extend(&su->env_whitelist_names, name))
err_oom();
if (strv_extend(&su->env_whitelist_vals, env))
err_oom();
return 0;
}
static int env_whitelist_setenv(struct su_context *su, int overwrite)
{
char **one;
size_t i = 0;
int rc;
STRV_FOREACH(one, su->env_whitelist_names) {
rc = setenv(*one, su->env_whitelist_vals[i], overwrite);
if (rc)
return rc;
i++;
}
return 0;
}
/* Creates (add to) whitelist from comma delimited string */
static int env_whitelist_from_string(struct su_context *su, const char *str)
{
char **all = strv_split(str, ",");
char **one;
if (!all) {
if (errno == ENOMEM)
err_oom();
return -EINVAL;
}
STRV_FOREACH(one, all)
env_whitelist_add(su, *one);
strv_free(all);
return 0;
}
static void setenv_path(const struct passwd *pw)
{
int rc;
DBG(MISC, ul_debug("setting PATH"));
if (pw->pw_uid)
rc = logindefs_setenv("PATH", "ENV_PATH", _PATH_DEFPATH);
else if ((rc = logindefs_setenv("PATH", "ENV_SUPATH", NULL)) != 0)
rc = logindefs_setenv("PATH", "ENV_ROOTPATH", _PATH_DEFPATH_ROOT);
if (rc)
err(EXIT_FAILURE, _("failed to set the PATH environment variable"));
}
static void modify_environment(struct su_context *su, const char *shell)
{
const struct passwd *pw = su->pwd;
DBG(MISC, ul_debug("modify environ[]"));
/* Leave TERM unchanged. Set HOME, SHELL, USER, LOGNAME, PATH.
*
* Unset all other environment variables, but follow
* --whitelist-environment if specified.
*/
if (su->simulate_login) {
/* leave TERM unchanged */
env_whitelist_add(su, "TERM");
/* Note that original su(1) has allocated environ[] by malloc
* to the number of expected variables. This seems unnecessary
* optimization as libc later re-alloc(current_size+2) and for
* empty environ[] the curren_size is zero. It seems better to
* keep all logic around environment in glibc's hands.
* --kzak [Aug 2018]
*/
#ifdef HAVE_CLEARENV
clearenv();
#else
environ = NULL;
#endif
/* always reset */
if (shell)
xsetenv("SHELL", shell, 1);
setenv_path(pw);
xsetenv("HOME", pw->pw_dir, 1);
xsetenv("USER", pw->pw_name, 1);
xsetenv("LOGNAME", pw->pw_name, 1);
/* apply all from whitelist, but no overwrite */
env_whitelist_setenv(su, 0);
/* Set HOME, SHELL, and (if not becoming a superuser) USER and LOGNAME.
*/
} else if (su->change_environment) {
xsetenv("HOME", pw->pw_dir, 1);
if (shell)
xsetenv("SHELL", shell, 1);
if (getlogindefs_bool("ALWAYS_SET_PATH", 0))
setenv_path(pw);
if (pw->pw_uid) {
xsetenv("USER", pw->pw_name, 1);
xsetenv("LOGNAME", pw->pw_name, 1);
}
}
supam_export_environment(su);
}
static void init_groups(struct su_context *su, gid_t *groups, size_t ngroups)
{
int rc;
DBG(MISC, ul_debug("initialize groups"));
errno = 0;
if (ngroups)
rc = setgroups(ngroups, groups);
else
rc = initgroups(su->pwd->pw_name, su->pwd->pw_gid);
if (rc == -1) {
supam_cleanup(su, PAM_ABORT);
err(EXIT_FAILURE, _("cannot set groups"));
}
endgrent();
rc = pam_setcred(su->pamh, PAM_ESTABLISH_CRED);
if (is_pam_failure(rc))
errx(EXIT_FAILURE, _("failed to user credentials: %s"),
pam_strerror(su->pamh, rc));
su->pam_has_cred = 1;
}
static void change_identity(const struct passwd *pw)
{
DBG(MISC, ul_debug("changing identity [GID=%d, UID=%d]", pw->pw_gid, pw->pw_uid));
if (setgid(pw->pw_gid))
err(EXIT_FAILURE, _("cannot set group id"));
if (setuid(pw->pw_uid))
err(EXIT_FAILURE, _("cannot set user id"));
}
/* Run SHELL, if COMMAND is nonzero, pass it to the shell with the -c option.
* Pass ADDITIONAL_ARGS to the shell as more arguments; there are
* N_ADDITIONAL_ARGS extra arguments.
*/
static void run_shell(
struct su_context *su,
char const *shell, char const *command, char **additional_args,
size_t n_additional_args)
{
size_t n_args = 1 + su->fast_startup + 2 * ! !command + n_additional_args + 1;
const char **args = xcalloc(n_args, sizeof *args);
size_t argno = 1;
DBG(MISC, ul_debug("starting shell [shell=%s, command=\"%s\"%s%s]",
shell, command,
su->simulate_login ? " login" : "",
su->fast_startup ? " fast-start" : ""));
if (su->simulate_login) {
char *arg0;
char *shell_basename;
shell_basename = basename(shell);
arg0 = xmalloc(strlen(shell_basename) + 2);
arg0[0] = '-';
strcpy(arg0 + 1, shell_basename);
args[0] = arg0;
} else
args[0] = basename(shell);
if (su->fast_startup)
args[argno++] = "-f";
if (command) {
args[argno++] = "-c";
args[argno++] = command;
}
memcpy(args + argno, additional_args, n_additional_args * sizeof *args);
args[argno + n_additional_args] = NULL;
execv(shell, (char **)args);
errexec(shell);
}
/* Return true if SHELL is a restricted shell (one not returned by
* getusershell), else false, meaning it is a standard shell.
*/
static bool is_restricted_shell(const char *shell)
{
char *line;
setusershell();
while ((line = getusershell()) != NULL) {
if (*line != '#' && !strcmp(line, shell)) {
endusershell();
return false;
}
}
endusershell();
DBG(MISC, ul_debug("%s is restricted shell (not in /etc/shells)", shell));
return true;
}
static void usage_common(void)
{
fputs(_(" -m, -p, --preserve-environment do not reset environment variables\n"), stdout);
fputs(_(" -w, --whitelist-environment <list> don't reset specified variables\n"), stdout);
fputs(USAGE_SEPARATOR, stdout);
fputs(_(" -g, --group <group> specify the primary group\n"), stdout);
fputs(_(" -G, --supp-group <group> specify a supplemental group\n"), stdout);
fputs(USAGE_SEPARATOR, stdout);
fputs(_(" -, -l, --login make the shell a login shell\n"), stdout);
fputs(_(" -c, --command <command> pass a single command to the shell with -c\n"), stdout);
fputs(_(" --session-command <command> pass a single command to the shell with -c\n"
" and do not create a new session\n"), stdout);
fputs(_(" -f, --fast pass -f to the shell (for csh or tcsh)\n"), stdout);
fputs(_(" -s, --shell <shell> run <shell> if /etc/shells allows it\n"), stdout);
fputs(_(" -P, --pty create a new pseudo-terminal\n"), stdout);
fputs(USAGE_SEPARATOR, stdout);
printf(USAGE_HELP_OPTIONS(33));
}
static void usage_runuser(void)
{
fputs(USAGE_HEADER, stdout);
fprintf(stdout,
_(" %1$s [options] -u <user> [[--] <command>]\n"
" %1$s [options] [-] [<user> [<argument>...]]\n"),
program_invocation_short_name);
fputs(USAGE_SEPARATOR, stdout);
fputs(_("Run <command> with the effective user ID and group ID of <user>. If -u is\n"
"not given, fall back to su(1)-compatible semantics and execute standard shell.\n"
"The options -c, -f, -l, and -s are mutually exclusive with -u.\n"), stdout);
fputs(USAGE_OPTIONS, stdout);
fputs(_(" -u, --user <user> username\n"), stdout);
usage_common();
fputs(USAGE_SEPARATOR, stdout);
fprintf(stdout, USAGE_MAN_TAIL("runuser(1)"));
}
static void usage_su(void)
{
fputs(USAGE_HEADER, stdout);
fprintf(stdout,
_(" %s [options] [-] [<user> [<argument>...]]\n"),
program_invocation_short_name);
fputs(USAGE_SEPARATOR, stdout);
fputs(_("Change the effective user ID and group ID to that of <user>.\n"
"A mere - implies -l. If <user> is not given, root is assumed.\n"), stdout);
fputs(USAGE_OPTIONS, stdout);
usage_common();
fprintf(stdout, USAGE_MAN_TAIL("su(1)"));
}
static void __attribute__((__noreturn__)) usage(int mode)
{
if (mode == SU_MODE)
usage_su();
else
usage_runuser();
exit(EXIT_SUCCESS);
}
static void load_config(void *data)
{
struct su_context *su = (struct su_context *) data;
DBG(MISC, ul_debug("loading logindefs"));
logindefs_load_file(_PATH_LOGINDEFS);
logindefs_load_file(su->runuser ? _PATH_LOGINDEFS_RUNUSER : _PATH_LOGINDEFS_SU);
}
/*
* Returns 1 if the current user is not root
*/
static int is_not_root(void)
{
const uid_t ruid = getuid();
const uid_t euid = geteuid();
/* if we're really root and aren't running setuid */
return (uid_t) 0 == ruid && ruid == euid ? 0 : 1;
}
static gid_t add_supp_group(const char *name, gid_t **groups, size_t *ngroups)
{
struct group *gr;
if (*ngroups >= NGROUPS_MAX)
errx(EXIT_FAILURE,
P_("specifying more than %d supplemental group is not possible",
"specifying more than %d supplemental groups is not possible",
NGROUPS_MAX - 1), NGROUPS_MAX - 1);
gr = getgrnam(name);
if (!gr)
errx(EXIT_FAILURE, _("group %s does not exist"), name);
DBG(MISC, ul_debug("add %s group [name=%s, GID=%d]", name, gr->gr_name, (int) gr->gr_gid));
*groups = xrealloc(*groups, sizeof(gid_t) * (*ngroups + 1));
(*groups)[*ngroups] = gr->gr_gid;
(*ngroups)++;
return gr->gr_gid;
}
int su_main(int argc, char **argv, int mode)
{
struct su_context _su = {
.conv = { supam_conv, NULL },
.runuser = (mode == RUNUSER_MODE ? 1 : 0),
.change_environment = 1,
.new_user = DEFAULT_USER,
#ifdef USE_PTY
.pty_master = -1,
.pty_slave = -1,
.pty_sigfd = -1,
#endif
}, *su = &_su;
int optc;
char *command = NULL;
int request_same_session = 0;
char *shell = NULL;
gid_t *groups = NULL;
size_t ngroups = 0;
bool use_supp = false;
bool use_gid = false;
gid_t gid = 0;
static const struct option longopts[] = {
{"command", required_argument, NULL, 'c'},
{"session-command", required_argument, NULL, 'C'},
{"fast", no_argument, NULL, 'f'},
{"login", no_argument, NULL, 'l'},
{"preserve-environment", no_argument, NULL, 'p'},
{"pty", no_argument, NULL, 'P'},
{"shell", required_argument, NULL, 's'},
{"group", required_argument, NULL, 'g'},
{"supp-group", required_argument, NULL, 'G'},
{"user", required_argument, NULL, 'u'}, /* runuser only */
{"whitelist-environment", required_argument, NULL, 'w'},
{"help", no_argument, 0, 'h'},
{"version", no_argument, 0, 'V'},
{NULL, 0, NULL, 0}
};
static const ul_excl_t excl[] = { /* rows and cols in ASCII order */
{ 'm', 'w' }, /* preserve-environment, whitelist-environment */
{ 'p', 'w' }, /* preserve-environment, whitelist-environment */
{ 0 }
};
int excl_st[ARRAY_SIZE(excl)] = UL_EXCL_STATUS_INIT;
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
close_stdout_atexit();
su_init_debug();
su->conv.appdata_ptr = (void *) su;
while ((optc =
getopt_long(argc, argv, "c:fg:G:lmpPs:u:hVw:", longopts,
NULL)) != -1) {
err_exclusive_options(optc, longopts, excl, excl_st);
switch (optc) {
case 'c':
command = optarg;
break;
case 'C':
command = optarg;
request_same_session = 1;
break;
case 'f':
su->fast_startup = true;
break;
case 'g':
use_gid = true;
gid = add_supp_group(optarg, &groups, &ngroups);
break;
case 'G':
use_supp = true;
add_supp_group(optarg, &groups, &ngroups);
break;
case 'l':
su->simulate_login = true;
break;
case 'm':
case 'p':
su->change_environment = false;
break;
case 'w':
env_whitelist_from_string(su, optarg);
break;
case 'P':
#ifdef USE_PTY
su->pty = 1;
#else
errx(EXIT_FAILURE, _("--pty is not supported for your system"));
#endif
break;
case 's':
shell = optarg;
break;
case 'u':
if (!su->runuser)
errtryhelp(EXIT_FAILURE);
su->runuser_uopt = 1;
su->new_user = optarg;
break;
case 'h':
usage(mode);
case 'V':
print_version(EXIT_SUCCESS);
default:
errtryhelp(EXIT_FAILURE);
}
}
su->restricted = is_not_root();
if (optind < argc && !strcmp(argv[optind], "-")) {
su->simulate_login = true;
++optind;
}
if (su->simulate_login && !su->change_environment) {
warnx(_
("ignoring --preserve-environment, it's mutually exclusive with --login"));
su->change_environment = true;
}
switch (mode) {
case RUNUSER_MODE:
/* runuser -u <user> <command>
*
* If -u <user> is not specified, then follow traditional su(1) behavior and
* fallthrough
*/
if (su->runuser_uopt) {
if (shell || su->fast_startup || command || su->simulate_login)
errx(EXIT_FAILURE,
_("options --{shell,fast,command,session-command,login} and "
"--user are mutually exclusive"));
if (optind == argc)
errx(EXIT_FAILURE, _("no command was specified"));
break;
}
/* fallthrough */
case SU_MODE:
if (optind < argc)
su->new_user = argv[optind++];
break;
}
if ((use_supp || use_gid) && su->restricted)
errx(EXIT_FAILURE,
_("only root can specify alternative groups"));
logindefs_set_loader(load_config, (void *) su);
init_tty(su);
su->pwd = xgetpwnam(su->new_user, &su->pwdbuf);
if (!su->pwd
|| !su->pwd->pw_passwd
|| !su->pwd->pw_name || !*su->pwd->pw_name
|| !su->pwd->pw_dir || !*su->pwd->pw_dir)
errx(EXIT_FAILURE,
_("user %s does not exist or the user entry does not "
"contain all the required fields"), su->new_user);
su->new_user = su->pwd->pw_name;
su->old_user = xgetlogin();
if (!su->pwd->pw_shell || !*su->pwd->pw_shell)
su->pwd->pw_shell = DEFAULT_SHELL;
if (use_supp && !use_gid)
su->pwd->pw_gid = groups[0];
else if (use_gid)
su->pwd->pw_gid = gid;
supam_authenticate(su);
if (request_same_session || !command || !su->pwd->pw_uid)
su->same_session = 1;
/* initialize shell variable only if "-u <user>" not specified */
if (su->runuser_uopt) {
shell = NULL;
} else {
if (!shell && !su->change_environment)
shell = getenv("SHELL");
if (shell
&& getuid() != 0
&& is_restricted_shell(su->pwd->pw_shell)) {
/* The user being su'd to has a nonstandard shell, and
* so is probably a uucp account or has restricted
* access. Don't compromise the account by allowing
* access with a standard shell.
*/
warnx(_("using restricted shell %s"), su->pwd->pw_shell);
shell = NULL;
}
shell = xstrdup(shell ? shell : su->pwd->pw_shell);
}
init_groups(su, groups, ngroups);
if (!su->simulate_login || command)
su->suppress_pam_info = 1; /* don't print PAM info messages */
supam_open_session(su);
create_watching_parent(su);
/* Now we're in the child. */
change_identity(su->pwd);
if (!su->same_session || su->pty) {
DBG(MISC, ul_debug("call setsid()"));
setsid();
}
#ifdef USE_PTY
if (su->pty)
pty_init_slave(su);
#endif
/* Set environment after pam_open_session, which may put KRB5CCNAME
into the pam_env, etc. */
modify_environment(su, shell);
if (su->simulate_login && chdir(su->pwd->pw_dir) != 0)
warn(_("warning: cannot change directory to %s"), su->pwd->pw_dir);
if (shell)
run_shell(su, shell, command, argv + optind, max(0, argc - optind));
execvp(argv[optind], &argv[optind]);
err(EXIT_FAILURE, _("failed to execute %s"), argv[optind]);
}
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