freebsd-dev/usr.bin/su/su.c
Robert Watson c8fbd1ec9b If su(1) is run without an effective uid of 0, generate an error to
the user indicating that su is not running setuid, which may help
suggest to the user that it should be setuid, or should not be
running from a file system mounted nosuid.

Suggsted by:	Ivan Voras <ivoras at fer dot hr>
MFC after:	2 weeks
2005-01-17 19:57:59 +00:00

573 lines
15 KiB
C

/*
* Copyright (c) 2002, 2005 Networks Associates Technologies, Inc.
* All rights reserved.
*
* Portions of this software were developed for the FreeBSD Project by
* ThinkSec AS and NAI Labs, the Security Research Division of Network
* Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035
* ("CBOSS"), as part of the DARPA CHATS research program.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 THE AUTHOR 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.
*/
/*-
* Copyright (c) 1988, 1993, 1994
* The Regents of the University of California. 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University 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 THE REGENTS 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 THE REGENTS 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.
*/
#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1988, 1993, 1994\n\
The Regents of the University of California. All rights reserved.\n";
#endif /* not lint */
#if 0
#ifndef lint
static char sccsid[] = "@(#)su.c 8.3 (Berkeley) 4/2/94";
#endif /* not lint */
#endif
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/wait.h>
#include <err.h>
#include <errno.h>
#include <grp.h>
#include <login_cap.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <security/pam_appl.h>
#include <security/openpam.h>
#define PAM_END() do { \
int local_ret; \
if (pamh != NULL) { \
local_ret = pam_setcred(pamh, PAM_DELETE_CRED); \
if (local_ret != PAM_SUCCESS) \
syslog(LOG_ERR, "pam_setcred: %s", \
pam_strerror(pamh, local_ret)); \
if (asthem) { \
local_ret = pam_close_session(pamh, 0); \
if (local_ret != PAM_SUCCESS) \
syslog(LOG_ERR, "pam_close_session: %s",\
pam_strerror(pamh, local_ret)); \
} \
local_ret = pam_end(pamh, local_ret); \
if (local_ret != PAM_SUCCESS) \
syslog(LOG_ERR, "pam_end: %s", \
pam_strerror(pamh, local_ret)); \
} \
} while (0)
#define PAM_SET_ITEM(what, item) do { \
int local_ret; \
local_ret = pam_set_item(pamh, what, item); \
if (local_ret != PAM_SUCCESS) { \
syslog(LOG_ERR, "pam_set_item(" #what "): %s", \
pam_strerror(pamh, local_ret)); \
errx(1, "pam_set_item(" #what "): %s", \
pam_strerror(pamh, local_ret)); \
/* NOTREACHED */ \
} \
} while (0)
enum tristate { UNSET, YES, NO };
static pam_handle_t *pamh = NULL;
static char **environ_pam;
static char *ontty(void);
static int chshell(const char *);
static void usage(void) __dead2;
static void export_pam_environment(void);
static int ok_to_export(const char *);
extern char **environ;
int
main(int argc, char *argv[])
{
static char *cleanenv;
struct passwd *pwd;
struct pam_conv conv = { openpam_ttyconv, NULL };
enum tristate iscsh;
login_cap_t *lc;
union {
const char **a;
char * const *b;
} np;
uid_t ruid;
pid_t child_pid, child_pgrp, pid;
int asme, ch, asthem, fastlogin, prio, i, retcode,
statusp, setmaclabel;
u_int setwhat;
char *username, *class, shellbuf[MAXPATHLEN];
const char *p, *user, *shell, *mytty, **nargv;
struct sigaction sa, sa_int, sa_quit, sa_pipe;
int temp, fds[2];
shell = class = cleanenv = NULL;
asme = asthem = fastlogin = statusp = 0;
user = "root";
iscsh = UNSET;
setmaclabel = 0;
while ((ch = getopt(argc, argv, "-flmsc:")) != -1)
switch ((char)ch) {
case 'f':
fastlogin = 1;
break;
case '-':
case 'l':
asme = 0;
asthem = 1;
break;
case 'm':
asme = 1;
asthem = 0;
break;
case 's':
setmaclabel = 1;
break;
case 'c':
class = optarg;
break;
case '?':
default:
usage();
/* NOTREACHED */
}
if (optind < argc)
user = argv[optind++];
if (user == NULL)
usage();
/* NOTREACHED */
if (strlen(user) > MAXLOGNAME - 1)
errx(1, "username too long");
/*
* Try to provide more helpful debugging output if su(1) is running
* non-setuid, or was run from a file system not mounted setuid.
*/
if (geteuid() != 0)
errx(1, "not running setuid");
nargv = malloc(sizeof(char *) * (size_t)(argc + 4));
if (nargv == NULL)
errx(1, "malloc failure");
nargv[argc + 3] = NULL;
for (i = argc; i >= optind; i--)
nargv[i + 3] = argv[i];
np.a = &nargv[i + 3];
argv += optind;
errno = 0;
prio = getpriority(PRIO_PROCESS, 0);
if (errno)
prio = 0;
setpriority(PRIO_PROCESS, 0, -2);
openlog("su", LOG_CONS, LOG_AUTH);
/* get current login name, real uid and shell */
ruid = getuid();
username = getlogin();
pwd = getpwnam(username);
if (username == NULL || pwd == NULL || pwd->pw_uid != ruid)
pwd = getpwuid(ruid);
if (pwd == NULL)
errx(1, "who are you?");
username = strdup(pwd->pw_name);
if (username == NULL)
err(1, "strdup failure");
if (asme) {
if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') {
/* must copy - pwd memory is recycled */
shell = strncpy(shellbuf, pwd->pw_shell,
sizeof(shellbuf));
shellbuf[sizeof(shellbuf) - 1] = '\0';
}
else {
shell = _PATH_BSHELL;
iscsh = NO;
}
}
/* Do the whole PAM startup thing */
retcode = pam_start("su", user, &conv, &pamh);
if (retcode != PAM_SUCCESS) {
syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, retcode));
errx(1, "pam_start: %s", pam_strerror(pamh, retcode));
}
PAM_SET_ITEM(PAM_RUSER, username);
mytty = ttyname(STDERR_FILENO);
if (!mytty)
mytty = "tty";
PAM_SET_ITEM(PAM_TTY, mytty);
retcode = pam_authenticate(pamh, 0);
if (retcode != PAM_SUCCESS) {
syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s on %s",
username, user, mytty);
errx(1, "Sorry");
}
retcode = pam_get_item(pamh, PAM_USER, (const void **)&p);
if (retcode == PAM_SUCCESS)
user = p;
else
syslog(LOG_ERR, "pam_get_item(PAM_USER): %s",
pam_strerror(pamh, retcode));
pwd = getpwnam(user);
if (pwd == NULL)
errx(1, "unknown login: %s", user);
retcode = pam_acct_mgmt(pamh, 0);
if (retcode == PAM_NEW_AUTHTOK_REQD) {
retcode = pam_chauthtok(pamh,
PAM_CHANGE_EXPIRED_AUTHTOK);
if (retcode != PAM_SUCCESS) {
syslog(LOG_ERR, "pam_chauthtok: %s",
pam_strerror(pamh, retcode));
errx(1, "Sorry");
}
}
if (retcode != PAM_SUCCESS) {
syslog(LOG_ERR, "pam_acct_mgmt: %s",
pam_strerror(pamh, retcode));
errx(1, "Sorry");
}
/* get target login information */
if (class == NULL)
lc = login_getpwclass(pwd);
else {
if (ruid != 0)
errx(1, "only root may use -c");
lc = login_getclass(class);
if (lc == NULL)
errx(1, "unknown class: %s", class);
}
/* if asme and non-standard target shell, must be root */
if (asme) {
if (ruid != 0 && !chshell(pwd->pw_shell))
errx(1, "permission denied (shell)");
}
else if (pwd->pw_shell && *pwd->pw_shell) {
shell = pwd->pw_shell;
iscsh = UNSET;
}
else {
shell = _PATH_BSHELL;
iscsh = NO;
}
/* if we're forking a csh, we want to slightly muck the args */
if (iscsh == UNSET) {
p = strrchr(shell, '/');
if (p)
++p;
else
p = shell;
iscsh = strcmp(p, "csh") ? (strcmp(p, "tcsh") ? NO : YES) : YES;
}
setpriority(PRIO_PROCESS, 0, prio);
/* Switch to home directory */
if (asthem) {
if (chdir(pwd->pw_dir) < 0)
errx(1, "no directory");
}
/*
* PAM modules might add supplementary groups in pam_setcred(), so
* initialize them first.
*/
if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) < 0)
err(1, "setusercontext");
retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED);
if (retcode != PAM_SUCCESS) {
syslog(LOG_ERR, "pam_setcred: %s",
pam_strerror(pamh, retcode));
errx(1, "failed to establish credentials.");
}
if (asthem) {
retcode = pam_open_session(pamh, 0);
if (retcode != PAM_SUCCESS) {
syslog(LOG_ERR, "pam_open_session: %s",
pam_strerror(pamh, retcode));
errx(1, "failed to open session.");
}
}
/*
* We must fork() before setuid() because we need to call
* pam_setcred(pamh, PAM_DELETE_CRED) as root.
*/
sa.sa_flags = SA_RESTART;
sa.sa_handler = SIG_IGN;
sigemptyset(&sa.sa_mask);
sigaction(SIGINT, &sa, &sa_int);
sigaction(SIGQUIT, &sa, &sa_quit);
sigaction(SIGPIPE, &sa, &sa_pipe);
sa.sa_handler = SIG_DFL;
sigaction(SIGTSTP, &sa, NULL);
statusp = 1;
if (pipe(fds) == -1) {
PAM_END();
err(1, "pipe");
}
child_pid = fork();
switch (child_pid) {
default:
sa.sa_handler = SIG_IGN;
sigaction(SIGTTOU, &sa, NULL);
close(fds[0]);
setpgid(child_pid, child_pid);
tcsetpgrp(STDERR_FILENO, child_pid);
close(fds[1]);
sigaction(SIGPIPE, &sa_pipe, NULL);
while ((pid = waitpid(child_pid, &statusp, WUNTRACED)) != -1) {
if (WIFSTOPPED(statusp)) {
kill(getpid(), SIGSTOP);
child_pgrp = getpgid(child_pid);
tcsetpgrp(1, child_pgrp);
kill(child_pid, SIGCONT);
statusp = 1;
continue;
}
break;
}
tcsetpgrp(STDERR_FILENO, getpgrp());
if (pid == -1)
err(1, "waitpid");
PAM_END();
exit(WEXITSTATUS(statusp));
case -1:
PAM_END();
err(1, "fork");
case 0:
close(fds[1]);
read(fds[0], &temp, 1);
close(fds[0]);
sigaction(SIGPIPE, &sa_pipe, NULL);
sigaction(SIGINT, &sa_int, NULL);
sigaction(SIGQUIT, &sa_quit, NULL);
/*
* Set all user context except for: Environmental variables
* Umask Login records (wtmp, etc) Path
*/
setwhat = LOGIN_SETALL & ~(LOGIN_SETENV | LOGIN_SETUMASK |
LOGIN_SETLOGIN | LOGIN_SETPATH | LOGIN_SETGROUP |
LOGIN_SETMAC);
/*
* If -s is present, also set the MAC label.
*/
if (setmaclabel)
setwhat |= LOGIN_SETMAC;
/*
* Don't touch resource/priority settings if -m has been used
* or -l and -c hasn't, and we're not su'ing to root.
*/
if ((asme || (!asthem && class == NULL)) && pwd->pw_uid)
setwhat &= ~(LOGIN_SETPRIORITY | LOGIN_SETRESOURCES);
if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0)
err(1, "setusercontext");
if (!asme) {
if (asthem) {
p = getenv("TERM");
environ = &cleanenv;
}
if (asthem || pwd->pw_uid)
setenv("USER", pwd->pw_name, 1);
setenv("HOME", pwd->pw_dir, 1);
setenv("SHELL", shell, 1);
if (asthem) {
/*
* Add any environmental variables that the
* PAM modules may have set.
*/
environ_pam = pam_getenvlist(pamh);
if (environ_pam)
export_pam_environment();
/* set the su'd user's environment & umask */
setusercontext(lc, pwd, pwd->pw_uid,
LOGIN_SETPATH | LOGIN_SETUMASK |
LOGIN_SETENV);
if (p)
setenv("TERM", p, 1);
}
}
login_close(lc);
if (iscsh == YES) {
if (fastlogin)
*np.a-- = "-f";
if (asme)
*np.a-- = "-m";
}
/* csh strips the first character... */
*np.a = asthem ? "-su" : iscsh == YES ? "_su" : "su";
if (ruid != 0)
syslog(LOG_NOTICE, "%s to %s%s", username, user,
ontty());
execv(shell, np.b);
err(1, "%s", shell);
}
}
static void
export_pam_environment(void)
{
char **pp;
for (pp = environ_pam; *pp != NULL; pp++) {
if (ok_to_export(*pp))
putenv(*pp);
free(*pp);
}
}
/*
* Sanity checks on PAM environmental variables:
* - Make sure there is an '=' in the string.
* - Make sure the string doesn't run on too long.
* - Do not export certain variables. This list was taken from the
* Solaris pam_putenv(3) man page.
* Note that if the user is chrooted, PAM may have a better idea than we
* do of where her home directory is.
*/
static int
ok_to_export(const char *s)
{
static const char *noexport[] = {
"SHELL", /* "HOME", */ "LOGNAME", "MAIL", "CDPATH",
"IFS", "PATH", NULL
};
const char **pp;
size_t n;
if (strlen(s) > 1024 || strchr(s, '=') == NULL)
return 0;
if (strncmp(s, "LD_", 3) == 0)
return 0;
for (pp = noexport; *pp != NULL; pp++) {
n = strlen(*pp);
if (s[n] == '=' && strncmp(s, *pp, n) == 0)
return 0;
}
return 1;
}
static void
usage(void)
{
fprintf(stderr, "usage: su [-] [-flms] [-c class] [login [args]]\n");
exit(1);
/* NOTREACHED */
}
static int
chshell(const char *sh)
{
int r;
char *cp;
r = 0;
setusershell();
while ((cp = getusershell()) != NULL && !r)
r = (strcmp(cp, sh) == 0);
endusershell();
return r;
}
static char *
ontty(void)
{
char *p;
static char buf[MAXPATHLEN + 4];
buf[0] = 0;
p = ttyname(STDERR_FILENO);
if (p)
snprintf(buf, sizeof(buf), " on %s", p);
return buf;
}