path: root/source3/lib/util_sec.c

/*
   Unix SMB/CIFS implementation.
   Copyright (C) Jeremy Allison 1998.
   rewritten for version 2.0.6 by Tridge

   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 3 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, see <http://www.gnu.org/licenses/>.
*/

#ifndef AUTOCONF_TEST
#include "includes.h"
#include "system/passwd.h" /* uid_wrapper */
#include "../lib/util/setid.h"

#else
/* we are running this code in autoconf test mode to see which type of setuid
   function works */
#if defined(HAVE_UNISTD_H)
#include <unistd.h>
#endif
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <errno.h>

#ifdef HAVE_SYS_PRIV_H
#include <sys/priv.h>
#endif
#ifdef HAVE_SYS_ID_H
#include <sys/id.h>
#endif

#define DEBUG(x, y) printf y
#define smb_panic(x) exit(1)
#endif

/* are we running as non-root? This is used by the regression test code,
   and potentially also for sites that want non-root smbd */
static uid_t initial_uid;
static gid_t initial_gid;

/****************************************************************************
remember what uid we got started as - this allows us to run correctly
as non-root while catching trapdoor systems
****************************************************************************/

void sec_init(void)
{
	static int initialized;

	if (!initialized) {

#ifndef AUTOCONF_TEST
		if (uid_wrapper_enabled()) {
			setenv("UID_WRAPPER_MYUID", "1", 1);
		}
#endif

		initial_uid = geteuid();
		initial_gid = getegid();

#ifndef AUTOCONF_TEST
		if (uid_wrapper_enabled()) {
			unsetenv("UID_WRAPPER_MYUID");
		}
#endif

		initialized = 1;
	}
}

/****************************************************************************
some code (eg. winbindd) needs to know what uid we started as
****************************************************************************/
uid_t sec_initial_uid(void)
{
	return initial_uid;
}

/****************************************************************************
some code (eg. winbindd, profiling shm) needs to know what gid we started as
****************************************************************************/
gid_t sec_initial_gid(void)
{
	return initial_gid;
}

/**
 * @brief Check if we are running in root mode.
 *
 * @return Return whether Samba has root privileges
 */
bool root_mode(void)
{
	uid_t euid;

	euid = geteuid();

#ifndef AUTOCONF_TEST
	if (uid_wrapper_enabled()) {
		return (euid == initial_uid || euid == (uid_t)0);
	}
#endif

	return (initial_uid == euid);
}

/****************************************************************************
are we running in non-root mode?
****************************************************************************/
bool non_root_mode(void)
{
	return (initial_uid != (uid_t)0);
}

/****************************************************************************
abort if we haven't set the uid correctly
****************************************************************************/
static void assert_uid(uid_t ruid, uid_t euid)
{
	if ((euid != (uid_t)-1 && geteuid() != euid) ||
	    (ruid != (uid_t)-1 && getuid() != ruid)) {
		if (!non_root_mode()) {
			DEBUG(0,("Failed to set uid privileges to (%d,%d) now set to (%d,%d)\n",
				 (int)ruid, (int)euid,
				 (int)getuid(), (int)geteuid()));
			smb_panic("failed to set uid\n");
			exit(1);
		}
	}
}

/****************************************************************************
abort if we haven't set the gid correctly
****************************************************************************/
static void assert_gid(gid_t rgid, gid_t egid)
{
	if ((egid != (gid_t)-1 && getegid() != egid) ||
	    (rgid != (gid_t)-1 && getgid() != rgid)) {
		if (!non_root_mode()) {
			DEBUG(0,("Failed to set gid privileges to (%d,%d) now set to (%d,%d) uid=(%d,%d)\n",
				 (int)rgid, (int)egid,
				 (int)getgid(), (int)getegid(),
				 (int)getuid(), (int)geteuid()));
			smb_panic("failed to set gid\n");
			exit(1);
		}
	}
}

/****************************************************************************
 Gain root privilege before doing something. 
 We want to end up with ruid==euid==0
****************************************************************************/
void gain_root_privilege(void)
{	
#if defined(USE_SETRESUID) || defined(HAVE_LINUX_THREAD_CREDENTIALS)
	samba_setresuid(0,0,0);
#endif
    
#if USE_SETEUID
	samba_seteuid(0);
#endif

#if USE_SETREUID
	samba_setreuid(0, 0);
#endif

#if USE_SETUIDX
	samba_setuidx(ID_EFFECTIVE, 0);
	samba_setuidx(ID_REAL, 0);
#endif

	/* this is needed on some systems */
	samba_setuid(0);

	assert_uid(0, 0);
}


/****************************************************************************
 Ensure our real and effective groups are zero.
 we want to end up with rgid==egid==0
****************************************************************************/
void gain_root_group_privilege(void)
{
#if defined(USE_SETRESUID) || defined(HAVE_LINUX_THREAD_CREDENTIALS)
	samba_setresgid(0,0,0);
#endif

#if USE_SETREUID
	samba_setregid(0,0);
#endif

#if USE_SETEUID
	samba_setegid(0);
#endif

#if USE_SETUIDX
	samba_setgidx(ID_EFFECTIVE, 0);
	samba_setgidx(ID_REAL, 0);
#endif

	samba_setgid(0);

	assert_gid(0, 0);
}


/****************************************************************************
 Set effective uid, and possibly the real uid too.
 We want to end up with either:
  
   ruid==uid and euid==uid

 or

   ruid==0 and euid==uid

 depending on what the local OS will allow us to regain root from.
****************************************************************************/
void set_effective_uid(uid_t uid)
{
#if defined(USE_SETRESUID) || defined(HAVE_LINUX_THREAD_CREDENTIALS)
        /* Set the effective as well as the real uid. */
	if (samba_setresuid(uid,uid,-1) == -1) {
		if (errno == EAGAIN) {
			DEBUG(0, ("samba_setresuid failed with EAGAIN. uid(%d) "
				  "might be over its NPROC limit\n",
				  (int)uid));
		}
	}
#endif

#if USE_SETREUID
	samba_setreuid(-1,uid);
#endif

#if USE_SETEUID
	samba_seteuid(uid);
#endif

#if USE_SETUIDX
	samba_setuidx(ID_EFFECTIVE, uid);
#endif

	assert_uid(-1, uid);
}

/****************************************************************************
 Set *only* the effective gid.
 we want to end up with rgid==0 and egid==gid
****************************************************************************/
void set_effective_gid(gid_t gid)
{
#if defined(USE_SETRESUID) || defined(HAVE_LINUX_THREAD_CREDENTIALS)
	samba_setresgid(-1,gid,-1);
#endif

#if USE_SETREUID
	samba_setregid(-1,gid);
#endif

#if USE_SETEUID
	samba_setegid(gid);
#endif

#if USE_SETUIDX
	samba_setgidx(ID_EFFECTIVE, gid);
#endif

	assert_gid(-1, gid);
}

static uid_t saved_euid, saved_ruid;
static gid_t saved_egid, saved_rgid;

/****************************************************************************
 save the real and effective uid for later restoration. Used by the quotas
 code
****************************************************************************/
void save_re_uid(void)
{
	saved_ruid = getuid();
	saved_euid = geteuid();
}


/****************************************************************************
 and restore them!
****************************************************************************/

void restore_re_uid_fromroot(void)
{
#if defined(USE_SETRESUID) || defined(HAVE_LINUX_THREAD_CREDENTIALS)
	samba_setresuid(saved_ruid, saved_euid, -1);
#elif USE_SETREUID
	samba_setreuid(saved_ruid, -1);
	samba_setreuid(-1,saved_euid);
#elif USE_SETUIDX
	samba_setuidx(ID_REAL, saved_ruid);
	samba_setuidx(ID_EFFECTIVE, saved_euid);
#else
	set_effective_uid(saved_euid);
	if (getuid() != saved_ruid)
		samba_setuid(saved_ruid);
	set_effective_uid(saved_euid);
#endif

	assert_uid(saved_ruid, saved_euid);
}

void restore_re_uid(void)
{
	set_effective_uid(0);
	restore_re_uid_fromroot();
}

/****************************************************************************
 save the real and effective gid for later restoration. Used by the 
 getgroups code
****************************************************************************/
void save_re_gid(void)
{
	saved_rgid = getgid();
	saved_egid = getegid();
}

/****************************************************************************
 and restore them!
****************************************************************************/
void restore_re_gid(void)
{
#if defined(USE_SETRESUID) || defined(HAVE_LINUX_THREAD_CREDENTIALS)
	samba_setresgid(saved_rgid, saved_egid, -1);
#elif USE_SETREUID
	samba_setregid(saved_rgid, -1);
	samba_setregid(-1,saved_egid);
#elif USE_SETUIDX
	samba_setgidx(ID_REAL, saved_rgid);
	samba_setgidx(ID_EFFECTIVE, saved_egid);
#else
	set_effective_gid(saved_egid);
	if (getgid() != saved_rgid)
		samba_setgid(saved_rgid);
	set_effective_gid(saved_egid);
#endif

	assert_gid(saved_rgid, saved_egid);
}


/****************************************************************************
 set the real AND effective uid to the current effective uid in a way that
 allows root to be regained.
 This is only possible on some platforms.
****************************************************************************/
int set_re_uid(void)
{
	uid_t uid = geteuid();

#if defined(USE_SETRESUID) || defined(HAVE_LINUX_THREAD_CREDENTIALS)
	samba_setresuid(uid, uid, -1);
#endif

#if USE_SETREUID
	samba_setreuid(0, 0);
	samba_setreuid(uid, -1);
	samba_setreuid(-1, uid);
#endif

#if USE_SETEUID
	/* can't be done */
	return -1;
#endif

#if USE_SETUIDX
	/* can't be done */
	return -1;
#endif

	assert_uid(uid, uid);
	return 0;
}


/****************************************************************************
 Become the specified uid and gid - permanently !
 there should be no way back if possible
****************************************************************************/
void become_user_permanently(uid_t uid, gid_t gid)
{
	/*
	 * First - gain root privilege. We do this to ensure
	 * we can lose it again.
	 */

	gain_root_privilege();
	gain_root_group_privilege();

#if defined(USE_SETRESUID) || defined(HAVE_LINUX_THREAD_CREDENTIALS)
	samba_setresgid(gid,gid,gid);
	samba_setgid(gid);
	samba_setresuid(uid,uid,uid);
	samba_setuid(uid);
#endif

#if USE_SETREUID
	samba_setregid(gid,gid);
	samba_setgid(gid);
	samba_setreuid(uid,uid);
	samba_setuid(uid);
#endif

#if USE_SETEUID
	samba_setegid(gid);
	samba_setgid(gid);
	samba_setuid(uid);
	samba_seteuid(uid);
	samba_setuid(uid);
#endif

#if USE_SETUIDX
	samba_setgidx(ID_REAL, gid);
	samba_setgidx(ID_EFFECTIVE, gid);
	samba_setgid(gid);
	samba_setuidx(ID_REAL, uid);
	samba_setuidx(ID_EFFECTIVE, uid);
	samba_setuid(uid);
#endif
	
	assert_uid(uid, uid);
	assert_gid(gid, gid);
}

#if defined(HAVE_LINUX_THREAD_CREDENTIALS) && defined(HAVE___THREAD)
	struct set_thread_credentials_cache {
		bool active;
		uid_t uid;
		gid_t gid;
		size_t setlen;
		uintptr_t gidset;
	};
static __thread struct set_thread_credentials_cache cache;
#endif

/**********************************************************
 Function to set thread specific credentials. Leave
 saved-set uid/gid alone.Must be thread-safe code.
**********************************************************/

int set_thread_credentials(uid_t uid,
			gid_t gid,
			size_t setlen,
			const gid_t *gidset)
{
#if defined(HAVE_LINUX_THREAD_CREDENTIALS)
	/*
	 * With Linux thread-specific credentials
	 * we know we have setresuid/setresgid
	 * available.
	 */
#ifdef HAVE___THREAD
	if (cache.active &&
	    cache.uid == uid &&
	    cache.gid == gid &&
	    cache.setlen == setlen &&
	    (const gid_t *)cache.gidset == gidset)
	{
		return 0;
	}
#endif /* HAVE___THREAD */

	/* Become root. */
	/* Set ru=0, eu=0 */
	if (samba_setresuid(0, 0, -1) != 0) {
		return -1;
	}
	/* Set our primary gid. */
	/* Set rg=gid, eg=gid */
	if (samba_setresgid(gid, gid, -1) != 0) {
		return -1;
	}
	/* Set extra groups list. */
	if (samba_setgroups(setlen, gidset) != 0) {
		return -1;
	}
	/* Become the requested user. */
	/* Set ru=uid, eu=uid */
	if (samba_setresuid(uid, uid, -1) != 0) {
		return -1;
	}
	if (geteuid() != uid || getuid() != uid ||
			getegid() != gid || getgid() != gid) {
		smb_panic("set_thread_credentials failed\n");
		return -1;
	}

#ifdef HAVE___THREAD
	cache.active = true;
	cache.uid = uid;
	cache.gid = gid;
	cache.setlen = setlen;
	cache.gidset = (uintptr_t)gidset;
#endif /* HAVE___THREAD */

	return 0;
#else
	errno = ENOSYS;
	return -1;
#endif
}

#ifdef AUTOCONF_TEST

/****************************************************************************
this function just checks that we don't get ENOSYS back
****************************************************************************/
static int have_syscall(void)
{
	errno = 0;

#if defined(USE_SETRESUID) || defined(HAVE_LINUX_THREAD_CREDENTIALS)
	samba_setresuid(-1,-1,-1);
#endif

#if USE_SETREUID
	samba_setreuid(-1,-1);
#endif

#if USE_SETEUID
	samba_seteuid(-1);
#endif

#if USE_SETUIDX
	samba_setuidx(ID_EFFECTIVE, -1);
#endif

	if (errno == ENOSYS) {
		return -1;
	}
	return 0;
}

int main(void)
{
        if (getuid() != 0) {
#if (defined(AIX) && defined(USE_SETREUID))
		/* setreuid is badly broken on AIX 4.1, we avoid it completely */
                fprintf(stderr,"avoiding possibly broken setreuid\n");
		exit(1);
#endif

		/* if not running as root then at least check to see if we get ENOSYS - this 
		   handles Linux 2.0.x with glibc 2.1 */
                fprintf(stderr,"not running as root: checking for ENOSYS\n");
		exit(have_syscall());
	}

	gain_root_privilege();
	gain_root_group_privilege();
	set_effective_gid(1);
	set_effective_uid(1);
	save_re_uid();
	restore_re_uid();
	gain_root_privilege();
	gain_root_group_privilege();
	become_user_permanently(1, 1);
	samba_setuid(0);
	if (getuid() == 0) {
		fprintf(stderr,"uid not set permanently\n");
		exit(1);
	}

	printf("OK\n");

	exit(0);
}
#endif

/****************************************************************************
Check if we are setuid root.  Used in libsmb and smbpasswd paranoia checks.
****************************************************************************/
bool is_setuid_root(void) 
{
	return (geteuid() == (uid_t)0) && (getuid() != (uid_t)0);
}