shadow/src/su.c

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/*
* Copyright 1989 - 1994, Julianne Frances Haugh
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Julianne F. Haugh nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY JULIE HAUGH AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL JULIE HAUGH OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <config.h>
#include "rcsid.h"
RCSID (PKG_VER "$Id: su.c,v 1.34 2005/06/20 10:17:08 kloczek Exp $")
#include <sys/types.h>
#include <stdio.h>
#ifdef USE_PAM
#include "pam_defs.h"
static const struct pam_conv conv = {
misc_conv,
NULL
};
static pam_handle_t *pamh = NULL;
#endif
#include "prototypes.h"
#include "defines.h"
#include <grp.h>
#include <signal.h>
#include <pwd.h>
#include "pwauth.h"
#include "getdef.h"
/*
* Assorted #defines to control su's behavior
*/
/*
* Global variables
*/
/* not needed by sulog.c anymore */
static char name[BUFSIZ];
static char oldname[BUFSIZ];
static char *Prog;
extern struct passwd pwent;
/*
* External identifiers
*/
extern char **newenvp;
extern size_t newenvc;
extern char **environ;
/* local function prototypes */
#ifndef USE_PAM
static RETSIGTYPE die (int);
static int iswheel (const char *);
/*
* die - set or reset termio modes.
*
* die() is called before processing begins. signal() is then called
* with die() as the signal handler. If signal later calls die() with a
* signal number, the terminal modes are then reset.
*/
static RETSIGTYPE die (int killed)
{
static TERMIO sgtty;
if (killed)
STTY (0, &sgtty);
else
GTTY (0, &sgtty);
if (killed) {
closelog ();
exit (killed);
}
}
static int iswheel (const char *username)
{
struct group *grp;
grp = getgrnam ("wheel");;
if (!grp || !grp->gr_mem)
return 0;
return is_on_list (grp->gr_mem, username);
}
#endif /* !USE_PAM */
static void su_failure (const char *tty)
{
sulog (tty, 0, oldname, name); /* log failed attempt */
#ifdef USE_SYSLOG
if (getdef_bool ("SYSLOG_SU_ENAB"))
SYSLOG ((pwent.pw_uid ? LOG_INFO : LOG_NOTICE,
"- %s %s:%s", tty,
oldname[0] ? oldname : "???", name[0] ? name : "???"));
closelog ();
#endif
puts (_("Sorry."));
exit (1);
}
#ifdef USE_PAM
static int caught = 0;
/* Signal handler for parent process later */
static void su_catch_sig (int sig)
{
++caught;
}
/* This I ripped out of su.c from sh-utils after the Mandrake pam patch
* have been applied. Some work was needed to get it integrated into
* su.c from shadow.
*/
static void run_shell (const char *shellstr, char *args[], int doshell)
{
int child;
sigset_t ourset;
int status;
int ret;
child = fork ();
if (child == 0) { /* child shell */
pam_end (pamh, PAM_SUCCESS);
if (doshell)
shell (shellstr, (char *) args[0]);
else
(void) execv (shellstr, (char **) args);
{
int exit_status = (errno == ENOENT ? 127 : 126);
exit (exit_status);
}
} else if (child == -1) {
(void) fprintf (stderr, "%s: Cannot fork user shell\n", Prog);
SYSLOG ((LOG_WARN, "Cannot execute %s", pwent.pw_shell));
closelog ();
exit (1);
}
/* parent only */
sigfillset (&ourset);
if (sigprocmask (SIG_BLOCK, &ourset, NULL)) {
(void) fprintf (stderr, "%s: signal malfunction\n", Prog);
caught = 1;
}
if (!caught) {
struct sigaction action;
action.sa_handler = su_catch_sig;
sigemptyset (&action.sa_mask);
action.sa_flags = 0;
sigemptyset (&ourset);
if (sigaddset (&ourset, SIGTERM)
|| sigaddset (&ourset, SIGALRM)
|| sigaction (SIGTERM, &action, NULL)
|| sigprocmask (SIG_UNBLOCK, &ourset, NULL)
) {
fprintf (stderr,
"%s: signal masking malfunction\n", Prog);
caught = 1;
}
}
if (!caught) {
do {
int pid;
pid = waitpid (-1, &status, WUNTRACED);
if (WIFSTOPPED (status)) {
kill (getpid (), SIGSTOP);
/* once we get here, we must have resumed */
kill (pid, SIGCONT);
}
} while (WIFSTOPPED (status));
}
if (caught) {
fprintf (stderr, "\nSession terminated, killing shell...");
kill (child, SIGTERM);
}
ret = pam_close_session (pamh, 0);
if (ret != PAM_SUCCESS) {
SYSLOG ((LOG_ERR, "pam_close_session: %s",
pam_strerror (pamh, ret)));
fprintf (stderr, "%s: %s\n", Prog, pam_strerror (pamh, ret));
pam_end (pamh, ret);
exit (1);
}
ret = pam_end (pamh, PAM_SUCCESS);
if (caught) {
sleep (2);
kill (child, SIGKILL);
fprintf (stderr, " ...killed.\n");
exit (-1);
}
exit (WEXITSTATUS (status));
}
#endif
/*
* su - switch user id
*
* su changes the user's ids to the values for the specified user. if
* no new user name is specified, "root" is used by default.
*
* The only valid option is a "-" character, which is interpreted as
* requiring a new login session to be simulated.
*
* Any additional arguments are passed to the user's shell. In
* particular, the argument "-c" will cause the next argument to be
* interpreted as a command by the common shell programs.
*/
int main (int argc, char **argv)
{
char *cp;
char **envcp;
const char *tty = 0; /* Name of tty SU is run from */
int doshell = 0;
int fakelogin = 0;
int amroot = 0;
uid_t my_uid;
struct passwd *pw = 0;
char **envp = environ;
#ifdef USE_PAM
int ret;
#else /* !USE_PAM */
RETSIGTYPE (*oldsig) ();
int is_console = 0;
struct spwd *spwd = 0;
#ifdef SU_ACCESS
char *oldpass;
#endif
#endif /* !USE_PAM */
sanitize_env ();
setlocale (LC_ALL, "");
bindtextdomain (PACKAGE, LOCALEDIR);
textdomain (PACKAGE);
/*
* Get the program name. The program name is used as a prefix to
* most error messages.
*/
Prog = Basename (argv[0]);
OPENLOG ("su");
initenv ();
my_uid = getuid ();
amroot = (my_uid == 0);
/*
* Get the tty name. Entries will be logged indicating that the user
* tried to change to the named new user from the current terminal.
*/
if (isatty (0) && (cp = ttyname (0))) {
if (strncmp (cp, "/dev/", 5) == 0)
tty = cp + 5;
else
tty = cp;
#ifndef USE_PAM
is_console = console (tty);
#endif
} else {
/*
* Be more paranoid, like su from SimplePAMApps. --marekm
*/
if (!amroot) {
fprintf (stderr,
_("%s: must be run from a terminal\n"), Prog);
exit (1);
}
tty = "???";
}
/*
* Process the command line arguments.
*/
argc--;
argv++; /* shift out command name */
if (argc > 0 && strcmp (argv[0], "-") == 0) {
fakelogin = 1;
argc--;
argv++; /* shift ... */
}
/*
* If a new login is being set up, the old environment will be
* ignored and a new one created later on.
*/
if (fakelogin) {
if ((cp = getdef_str ("ENV_TZ")))
addenv (*cp == '/' ? tz (cp) : cp, NULL);
/*
* The clock frequency will be reset to the login value if required
*/
if ((cp = getdef_str ("ENV_HZ")))
addenv (cp, NULL); /* set the default $HZ, if one */
/*
* The terminal type will be left alone if it is present in
* the environment already.
*/
if ((cp = getenv ("TERM")))
addenv ("TERM", cp);
#ifndef USE_PAM
/*
* Also leave DISPLAY and XAUTHORITY if present, else
* pam_xauth will not work.
*/
if ((cp = getenv ("DISPLAY")))
addenv ("DISPLAY", cp);
if ((cp = getenv ("XAUTHORITY")))
addenv ("XAUTHORITY", cp);
#endif /* !USE_PAM */
} else {
while (*envp)
addenv (*envp++, NULL);
}
/*
* The next argument must be either a user ID, or some flag to a
* subshell. Pretty sticky since you can't have an argument which
* doesn't start with a "-" unless you specify the new user name.
* Any remaining arguments will be passed to the user's login shell.
*/
if (argc > 0 && argv[0][0] != '-') {
STRFCPY (name, argv[0]); /* use this login id */
argc--;
argv++; /* shift ... */
}
if (!name[0]) /* use default user ID */
(void) strcpy (name, "root");
doshell = argc == 0; /* any arguments remaining? */
/*
* Get the user's real name. The current UID is used to determine
* who has executed su. That user ID must exist.
*/
pw = get_my_pwent ();
if (!pw) {
SYSLOG ((LOG_CRIT, "Unknown UID: %u", my_uid));
su_failure (tty);
}
STRFCPY (oldname, pw->pw_name);
#ifndef USE_PAM
#ifdef SU_ACCESS
/*
* Sort out the password of user calling su, in case needed later
* -- chris
*/
if ((spwd = getspnam (oldname)))
pw->pw_passwd = spwd->sp_pwdp;
oldpass = xstrdup (pw->pw_passwd);
#endif /* SU_ACCESS */
#else /* USE_PAM */
ret = pam_start ("su", name, &conv, &pamh);
if (ret != PAM_SUCCESS) {
SYSLOG ((LOG_ERR, "pam_start: error %d", ret);
fprintf (stderr, _("%s: pam_start: error %d\n"),
Prog, ret));
exit (1);
}
ret = pam_set_item (pamh, PAM_TTY, (const void *) tty);
if (ret == PAM_SUCCESS)
ret = pam_set_item (pamh, PAM_RUSER, (const void *) oldname);
if (ret != PAM_SUCCESS) {
SYSLOG ((LOG_ERR, "pam_set_item: %s",
pam_strerror (pamh, ret)));
fprintf (stderr, "%s: %s\n", Prog, pam_strerror (pamh, ret));
pam_end (pamh, ret);
exit (1);
}
#endif /* USE_PAM */
top:
/*
* This is the common point for validating a user whose name is
* known. It will be reached either by normal processing, or if the
* user is to be logged into a subsystem root.
*
* The password file entries for the user is gotten and the account
* validated.
*/
if (!(pw = getpwnam (name))) {
(void) fprintf (stderr, _("Unknown id: %s\n"), name);
closelog ();
exit (1);
}
#ifndef USE_PAM
spwd = NULL;
if (strcmp (pw->pw_passwd, SHADOW_PASSWD_STRING) == 0
&& (spwd = getspnam (name)))
pw->pw_passwd = spwd->sp_pwdp;
#endif /* !USE_PAM */
pwent = *pw;
#ifndef USE_PAM
/*
* BSD systems only allow "wheel" to SU to root. USG systems don't,
* so we make this a configurable option.
*/
/* The original Shadow 3.3.2 did this differently. Do it like BSD:
*
* - check for UID 0 instead of name "root" - there are systems with
* several root accounts under different names,
*
* - check the contents of /etc/group instead of the current group
* set (you must be listed as a member, GID 0 is not sufficient).
*
* In addition to this traditional feature, we now have complete su
* access control (allow, deny, no password, own password). Thanks
* to Chris Evans <lady0110@sable.ox.ac.uk>.
*/
if (!amroot) {
if (pwent.pw_uid == 0 && getdef_bool ("SU_WHEEL_ONLY")
&& !iswheel (oldname)) {
fprintf (stderr,
_("You are not authorized to su %s\n"), name);
exit (1);
}
#ifdef SU_ACCESS
switch (check_su_auth (oldname, name)) {
case 0: /* normal su, require target user's password */
break;
case 1: /* require no password */
pwent.pw_passwd = ""; /* XXX warning: const */
break;
case 2: /* require own password */
puts (_("(Enter your own password.)"));
pwent.pw_passwd = oldpass;
break;
default: /* access denied (-1) or unexpected value */
fprintf (stderr,
_("You are not authorized to su %s\n"), name);
exit (1);
}
#endif /* SU_ACCESS */
}
#endif /* !USE_PAM */
/*
* Set the default shell.
*/
if (pwent.pw_shell[0] == '\0')
pwent.pw_shell = "/bin/sh"; /* XXX warning: const */
#ifdef USE_PAM
ret = pam_authenticate (pamh, 0);
if (ret != PAM_SUCCESS) {
SYSLOG ((LOG_ERR, "pam_authenticate: %s",
pam_strerror (pamh, ret)));
fprintf (stderr, "%s: %s\n", Prog, pam_strerror (pamh, ret));
pam_end (pamh, ret);
su_failure (tty);
}
ret = pam_acct_mgmt (pamh, 0);
if (ret != PAM_SUCCESS) {
if (amroot) {
fprintf (stderr, _("%s: %s\n(Ignored)\n"), Prog,
pam_strerror (pamh, ret));
} else {
SYSLOG ((LOG_ERR, "pam_acct_mgmt: %s",
pam_strerror (pamh, ret)));
fprintf (stderr, "%s: %s\n", Prog,
pam_strerror (pamh, ret));
pam_end (pamh, ret);
su_failure (tty);
}
}
#else /* !USE_PAM */
/*
* Set up a signal handler in case the user types QUIT.
*/
die (0);
oldsig = signal (SIGQUIT, die);
/*
* See if the system defined authentication method is being used.
* The first character of an administrator defined method is an '@'
* character.
*/
if (!amroot && pw_auth (pwent.pw_passwd, name, PW_SU, (char *) 0)) {
SYSLOG ((pwent.pw_uid ? LOG_NOTICE : LOG_WARN,
"Authentication failed for %s", name));
su_failure (tty);
}
signal (SIGQUIT, oldsig);
/*
* Check to see if the account is expired. root gets to ignore any
* expired accounts, but normal users can't become a user with an
* expired password.
*/
if (!amroot) {
if (!spwd)
spwd = pwd_to_spwd (&pwent);
if (isexpired (&pwent, spwd)) {
SYSLOG ((pwent.pw_uid ? LOG_WARN : LOG_CRIT,
"Expired account %s", name));
su_failure (tty);
}
}
/*
* Check to see if the account permits "su". root gets to ignore any
* restricted accounts, but normal users can't become a user if
* there is a "SU" entry in the /etc/porttime file denying access to
* the account.
*/
if (!amroot) {
if (!isttytime (pwent.pw_name, "SU", time ((time_t *) 0))) {
SYSLOG ((pwent.pw_uid ? LOG_WARN : LOG_CRIT,
"SU by %s to restricted account %s",
oldname, name));
su_failure (tty);
}
}
#endif /* !USE_PAM */
signal (SIGINT, SIG_DFL);
cp = getdef_str ((pwent.pw_uid == 0) ? "ENV_SUPATH" : "ENV_PATH");
/* XXX very similar code duplicated in libmisc/setupenv.c */
if (!cp) {
addenv ("PATH=/bin:/usr/bin", NULL);
} else if (strchr (cp, '=')) {
addenv (cp, NULL);
} else {
addenv ("PATH", cp);
}
/* setup the environment for pam later on, else we run into auth problems */
#ifndef USE_PAM
environ = newenvp; /* make new environment active */
#endif
if (getenv ("IFS")) /* don't export user IFS ... */
addenv ("IFS= \t\n", NULL); /* ... instead, set a safe IFS */
if (pwent.pw_shell[0] == '*') { /* subsystem root required */
pwent.pw_shell++; /* skip the '*' */
subsystem (&pwent); /* figure out what to execute */
endpwent ();
endspent ();
goto top;
}
sulog (tty, 1, oldname, name); /* save SU information */
endpwent ();
endspent ();
#ifdef USE_SYSLOG
if (getdef_bool ("SYSLOG_SU_ENAB"))
SYSLOG ((LOG_INFO, "+ %s %s:%s", tty,
oldname[0] ? oldname : "???", name[0] ? name : "???"));
#endif
#ifdef USE_PAM
/* set primary group id and supplementary groups */
if (setup_groups (&pwent)) {
pam_end (pamh, PAM_ABORT);
exit (1);
}
/*
* pam_setcred() may do things like resource limits, console groups,
* and much more, depending on the configured modules
*/
ret = pam_setcred (pamh, PAM_ESTABLISH_CRED);
if (ret != PAM_SUCCESS) {
SYSLOG ((LOG_ERR, "pam_setcred: %s", pam_strerror (pamh, ret)));
fprintf (stderr, "%s: %s\n", Prog, pam_strerror (pamh, ret));
pam_end (pamh, ret);
exit (1);
}
ret = pam_open_session (pamh, 0);
if (ret != PAM_SUCCESS) {
SYSLOG ((LOG_ERR, "pam_open_session: %s",
pam_strerror (pamh, ret)));
fprintf (stderr, "%s: %s\n", Prog, pam_strerror (pamh, ret));
pam_end (pamh, ret);
exit (1);
}
/* we need to setup the environment *after* pam_open_session(),
* else the UID is changed before stuff like pam_xauth could
* run, and we cannot access /etc/shadow and co
*/
environ = newenvp; /* make new environment active */
/* update environment with all pam set variables */
envcp = pam_getenvlist (pamh);
if (envcp) {
while (*envcp) {
addenv (*envcp, NULL);
envcp++;
}
}
/* become the new user */
if (change_uid (&pwent)) {
pam_setcred (pamh, PAM_DELETE_CRED);
pam_end (pamh, PAM_ABORT);
exit (1);
}
#else /* !USE_PAM */
if (!amroot) /* no limits if su from root */
setup_limits (&pwent);
if (setup_uid_gid (&pwent, is_console))
exit (1);
#endif /* !USE_PAM */
if (fakelogin)
setup_env (&pwent);
#if 1 /* Suggested by Joey Hess. XXX - is this right? */
else
addenv ("HOME", pwent.pw_dir);
#endif
/*
* This is a workaround for Linux libc bug/feature (?) - the
* /dev/log file descriptor is open without the close-on-exec flag
* and used to be passed to the new shell. There is "fcntl(LogFile,
* F_SETFD, 1)" in libc/misc/syslog.c, but it is commented out (at
* least in 5.4.33). Why? --marekm
*/
closelog ();
/*
* See if the user has extra arguments on the command line. In that
* case they will be provided to the new user's shell as arguments.
*/
if (fakelogin) {
char *arg0;
cp = getdef_str ("SU_NAME");
if (!cp)
cp = Basename (pwent.pw_shell);
arg0 = xmalloc (strlen (cp) + 2);
arg0[0] = '-';
strcpy (arg0 + 1, cp);
cp = arg0;
} else
cp = Basename (pwent.pw_shell);
if (!doshell) {
/*
* Use new user's shell from /etc/passwd and create an argv
* with the rest of the command line included.
*/
argv[-1] = pwent.pw_shell;
#ifndef USE_PAM
(void) execv (pwent.pw_shell, &argv[-1]);
#else
run_shell (pwent.pw_shell, &argv[-1], 0);
#endif
(void) fprintf (stderr, _("No shell\n"));
SYSLOG ((LOG_WARN, "Cannot execute %s", pwent.pw_shell));
closelog ();
exit (1);
}
#ifndef USE_PAM
shell (pwent.pw_shell, cp);
#else
run_shell (pwent.pw_shell, &cp, 1);
#endif
/* NOT REACHED */
exit (1);
}