[gssapi-openssh.git] / openssh / uidswap.c

/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Code for uid-swapping.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 */

#include "includes.h"
RCSID("$OpenBSD: uidswap.c,v 1.24 2003/05/29 16:58:45 deraadt Exp $");

#include "log.h"
#include "uidswap.h"
#include "xmalloc.h"

/*
 * Note: all these functions must work in all of the following cases:
 *    1. euid=0, ruid=0
 *    2. euid=0, ruid!=0
 *    3. euid!=0, ruid!=0
 * Additionally, they must work regardless of whether the system has
 * POSIX saved uids or not.
 */

#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
/* Lets assume that posix saved ids also work with seteuid, even though that
   is not part of the posix specification. */
#define SAVED_IDS_WORK_WITH_SETEUID
/* Saved effective uid. */
static uid_t 	saved_euid = 0;
static gid_t	saved_egid = 0;
#endif

/* Saved effective uid. */
static int	privileged = 0;
static int	temporarily_use_uid_effective = 0;
static gid_t	*saved_egroups = NULL, *user_groups = NULL;
static int	saved_egroupslen = -1, user_groupslen = -1;

/*
 * Temporarily changes to the given uid.  If the effective user
 * id is not root, this does nothing.  This call cannot be nested.
 */
void
temporarily_use_uid(struct passwd *pw)
{
	/* Save the current euid, and egroups. */
#ifdef SAVED_IDS_WORK_WITH_SETEUID
	saved_euid = geteuid();
	saved_egid = getegid();
	debug("temporarily_use_uid: %u/%u (e=%u/%u)",
	    (u_int)pw->pw_uid, (u_int)pw->pw_gid,
	    (u_int)saved_euid, (u_int)saved_egid);
	if (saved_euid != 0) {
		privileged = 0;
		return;
	}
#else
	if (geteuid() != 0) {
		privileged = 0;
		return;
	}
#endif /* SAVED_IDS_WORK_WITH_SETEUID */

	privileged = 1;
	temporarily_use_uid_effective = 1;

	saved_egroupslen = getgroups(0, NULL);
	if (saved_egroupslen < 0)
		fatal("getgroups: %.100s", strerror(errno));
	if (saved_egroupslen > 0) {
		saved_egroups = xrealloc(saved_egroups,
		    saved_egroupslen * sizeof(gid_t));
		if (getgroups(saved_egroupslen, saved_egroups) < 0)
			fatal("getgroups: %.100s", strerror(errno));
	} else { /* saved_egroupslen == 0 */
		if (saved_egroups != NULL)
			xfree(saved_egroups);
	}

	/* set and save the user's groups */
	if (user_groupslen == -1) {
		if (initgroups(pw->pw_name, pw->pw_gid) < 0)
			fatal("initgroups: %s: %.100s", pw->pw_name,
			    strerror(errno));

		user_groupslen = getgroups(0, NULL);
		if (user_groupslen < 0)
			fatal("getgroups: %.100s", strerror(errno));
		if (user_groupslen > 0) {
			user_groups = xrealloc(user_groups,
			    user_groupslen * sizeof(gid_t));
			if (getgroups(user_groupslen, user_groups) < 0)
				fatal("getgroups: %.100s", strerror(errno));
		} else { /* user_groupslen == 0 */
			if (user_groups)
				xfree(user_groups);
		}
	}
	/* Set the effective uid to the given (unprivileged) uid. */
	if (setgroups(user_groupslen, user_groups) < 0)
		fatal("setgroups: %.100s", strerror(errno));
#ifndef SAVED_IDS_WORK_WITH_SETEUID
	/* Propagate the privileged gid to all of our gids. */
	if (setgid(getegid()) < 0)
		debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
	/* Propagate the privileged uid to all of our uids. */
	if (setuid(geteuid()) < 0)
		debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
#endif /* SAVED_IDS_WORK_WITH_SETEUID */
	if (setegid(pw->pw_gid) < 0)
		fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
		    strerror(errno));
	if (seteuid(pw->pw_uid) == -1)
		fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
		    strerror(errno));
}

/*
 * Restores to the original (privileged) uid.
 */
void
restore_uid(void)
{
	/* it's a no-op unless privileged */
	if (!privileged) {
		debug("restore_uid: (unprivileged)");
		return;
	}
	if (!temporarily_use_uid_effective)
		fatal("restore_uid: temporarily_use_uid not effective");

#ifdef SAVED_IDS_WORK_WITH_SETEUID
	debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
	/* Set the effective uid back to the saved privileged uid. */
	if (seteuid(saved_euid) < 0)
		fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
	if (setegid(saved_egid) < 0)
		fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
#else /* SAVED_IDS_WORK_WITH_SETEUID */
	/*
	 * We are unable to restore the real uid to its unprivileged value.
	 * Propagate the real uid (usually more privileged) to effective uid
	 * as well.
	 */
	setuid(getuid());
	setgid(getgid());
#endif /* SAVED_IDS_WORK_WITH_SETEUID */

	if (setgroups(saved_egroupslen, saved_egroups) < 0)
		fatal("setgroups: %.100s", strerror(errno));
	temporarily_use_uid_effective = 0;
}

/*
 * Permanently sets all uids to the given uid.  This cannot be
 * called while temporarily_use_uid is effective.
 */
void
permanently_set_uid(struct passwd *pw)
{
	uid_t old_uid = getuid();
	gid_t old_gid = getgid();

	if (temporarily_use_uid_effective)
		fatal("permanently_set_uid: temporarily_use_uid effective");
	debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
	    (u_int)pw->pw_gid);

#if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID)
	if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0)
		fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
#elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
	if (setregid(pw->pw_gid, pw->pw_gid) < 0)
		fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
#else
	if (setegid(pw->pw_gid) < 0)
		fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
	if (setgid(pw->pw_gid) < 0)
		fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
#endif

#if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
	if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0)
		fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
	if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
		fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
#else
# ifndef SETEUID_BREAKS_SETUID
	if (seteuid(pw->pw_uid) < 0)
		fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
# endif
	if (setuid(pw->pw_uid) < 0)
		fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
#endif

	/* Try restoration of GID if changed (test clearing of saved gid) */
	if (old_gid != pw->pw_gid &&
	    (setgid(old_gid) != -1 || setegid(old_gid) != -1))
		fatal("%s: was able to restore old [e]gid", __func__);

	/* Verify GID drop was successful */
	if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) {
		fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
		    __func__, (u_int)getgid(), (u_int)getegid(),
		    (u_int)pw->pw_gid);
	}

#ifndef HAVE_CYGWIN
	/* Try restoration of UID if changed (test clearing of saved uid) */
	if (old_uid != pw->pw_uid &&
	    (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
		fatal("%s: was able to restore old [e]uid", __func__);
#endif

	/* Verify UID drop was successful */
	if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) {
		fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
		    __func__, (u_int)getuid(), (u_int)geteuid(),
		    (u_int)pw->pw_uid);
	}
}
Commit	Line	Data
3c0ef626	1	/*
	2	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	3	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	4	* All rights reserved
	5	* Code for uid-swapping.
	6	*
	7	* As far as I am concerned, the code I have written for this software
	8	* can be used freely for any purpose. Any derived versions of this
	9	* software must be clearly marked as such, and if the derived work is
	10	* incompatible with the protocol description in the RFC file, it must be
	11	* called by a name other than "ssh" or "Secure Shell".
	12	*/
	13
	14	#include "includes.h"
70791e56	15	RCSID("$OpenBSD: uidswap.c,v 1.24 2003/05/29 16:58:45 deraadt Exp $");
3c0ef626	16
	17	#include "log.h"
	18	#include "uidswap.h"
416fd2a8	19	#include "xmalloc.h"
3c0ef626	20
	21	/*
	22	* Note: all these functions must work in all of the following cases:
	23	* 1. euid=0, ruid=0
	24	* 2. euid=0, ruid!=0
	25	* 3. euid!=0, ruid!=0
	26	* Additionally, they must work regardless of whether the system has
	27	* POSIX saved uids or not.
	28	*/
	29
	30	#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
	31	/* Lets assume that posix saved ids also work with seteuid, even though that
	32	is not part of the posix specification. */
	33	#define SAVED_IDS_WORK_WITH_SETEUID
	34	/* Saved effective uid. */
	35	static uid_t saved_euid = 0;
	36	static gid_t saved_egid = 0;
	37	#endif
	38
	39	/* Saved effective uid. */
	40	static int privileged = 0;
	41	static int temporarily_use_uid_effective = 0;
416fd2a8	42	static gid_t saved_egroups = NULL, user_groups = NULL;
3c0ef626	43	static int saved_egroupslen = -1, user_groupslen = -1;
	44
	45	/*
	46	* Temporarily changes to the given uid. If the effective user
	47	* id is not root, this does nothing. This call cannot be nested.
	48	*/
	49	void
	50	temporarily_use_uid(struct passwd *pw)
	51	{
	52	/* Save the current euid, and egroups. */
	53	#ifdef SAVED_IDS_WORK_WITH_SETEUID
	54	saved_euid = geteuid();
	55	saved_egid = getegid();
e54b3d7c	56	debug("temporarily_use_uid: %u/%u (e=%u/%u)",
	57	(u_int)pw->pw_uid, (u_int)pw->pw_gid,
	58	(u_int)saved_euid, (u_int)saved_egid);
3c0ef626	59	if (saved_euid != 0) {
	60	privileged = 0;
	61	return;
	62	}
	63	#else
	64	if (geteuid() != 0) {
	65	privileged = 0;
	66	return;
	67	}
	68	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
	69
	70	privileged = 1;
	71	temporarily_use_uid_effective = 1;
416fd2a8	72
416fd2a8	73	saved_egroupslen = getgroups(0, NULL);
3c0ef626	74	if (saved_egroupslen < 0)
3c0ef626	75	fatal("getgroups: %.100s", strerror(errno));
416fd2a8	76	if (saved_egroupslen > 0) {
	77	saved_egroups = xrealloc(saved_egroups,
	78	saved_egroupslen * sizeof(gid_t));
	79	if (getgroups(saved_egroupslen, saved_egroups) < 0)
	80	fatal("getgroups: %.100s", strerror(errno));
	81	} else { /* saved_egroupslen == 0 */
	82	if (saved_egroups != NULL)
	83	xfree(saved_egroups);
	84	}
3c0ef626	85
	86	/* set and save the user's groups */
	87	if (user_groupslen == -1) {
	88	if (initgroups(pw->pw_name, pw->pw_gid) < 0)
	89	fatal("initgroups: %s: %.100s", pw->pw_name,
	90	strerror(errno));
416fd2a8	91
416fd2a8	92	user_groupslen = getgroups(0, NULL);
3c0ef626	93	if (user_groupslen < 0)
3c0ef626	94	fatal("getgroups: %.100s", strerror(errno));
416fd2a8	95	if (user_groupslen > 0) {
	96	user_groups = xrealloc(user_groups,
	97	user_groupslen * sizeof(gid_t));
	98	if (getgroups(user_groupslen, user_groups) < 0)
	99	fatal("getgroups: %.100s", strerror(errno));
	100	} else { /* user_groupslen == 0 */
	101	if (user_groups)
	102	xfree(user_groups);
	103	}
3c0ef626	104	}
3c0ef626	105	/* Set the effective uid to the given (unprivileged) uid. */
	106	if (setgroups(user_groupslen, user_groups) < 0)
	107	fatal("setgroups: %.100s", strerror(errno));
3c0ef626	108	#ifndef SAVED_IDS_WORK_WITH_SETEUID
	109	/* Propagate the privileged gid to all of our gids. */
	110	if (setgid(getegid()) < 0)
	111	debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
	112	/* Propagate the privileged uid to all of our uids. */
	113	if (setuid(geteuid()) < 0)
	114	debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
	115	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
	116	if (setegid(pw->pw_gid) < 0)
ff2d7a98	117	fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
3c0ef626	118	strerror(errno));
3c0ef626	119	if (seteuid(pw->pw_uid) == -1)
ff2d7a98	120	fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
3c0ef626	121	strerror(errno));
	122	}
	123
	124	/*
	125	* Restores to the original (privileged) uid.
	126	*/
	127	void
	128	restore_uid(void)
	129	{
3c0ef626	130	/* it's a no-op unless privileged */
e54b3d7c	131	if (!privileged) {
e54b3d7c	132	debug("restore_uid: (unprivileged)");
3c0ef626	133	return;
e54b3d7c	134	}
3c0ef626	135	if (!temporarily_use_uid_effective)
	136	fatal("restore_uid: temporarily_use_uid not effective");
	137
	138	#ifdef SAVED_IDS_WORK_WITH_SETEUID
e54b3d7c	139	debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
3c0ef626	140	/* Set the effective uid back to the saved privileged uid. */
3c0ef626	141	if (seteuid(saved_euid) < 0)
ff2d7a98	142	fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
3c0ef626	143	if (setegid(saved_egid) < 0)
ff2d7a98	144	fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
3c0ef626	145	#else /* SAVED_IDS_WORK_WITH_SETEUID */
	146	/*
	147	* We are unable to restore the real uid to its unprivileged value.
	148	* Propagate the real uid (usually more privileged) to effective uid
	149	* as well.
	150	*/
	151	setuid(getuid());
	152	setgid(getgid());
	153	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
	154
3c0ef626	155	if (setgroups(saved_egroupslen, saved_egroups) < 0)
3c0ef626	156	fatal("setgroups: %.100s", strerror(errno));
3c0ef626	157	temporarily_use_uid_effective = 0;
	158	}
	159
	160	/*
	161	* Permanently sets all uids to the given uid. This cannot be
	162	* called while temporarily_use_uid is effective.
	163	*/
	164	void
	165	permanently_set_uid(struct passwd *pw)
	166	{
70791e56	167	uid_t old_uid = getuid();
	168	gid_t old_gid = getgid();
	169
3c0ef626	170	if (temporarily_use_uid_effective)
ff2d7a98	171	fatal("permanently_set_uid: temporarily_use_uid effective");
e54b3d7c	172	debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
e54b3d7c	173	(u_int)pw->pw_gid);
70791e56	174
416fd2a8	175	#if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID)
70791e56	176	if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0)
	177	fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
	178	#elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
	179	if (setregid(pw->pw_gid, pw->pw_gid) < 0)
	180	fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
	181	#else
	182	if (setegid(pw->pw_gid) < 0)
	183	fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
3c0ef626	184	if (setgid(pw->pw_gid) < 0)
ff2d7a98	185	fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
70791e56	186	#endif
70791e56	187
416fd2a8	188	#if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
70791e56	189	if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0)
	190	fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
	191	#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
	192	if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
	193	fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
	194	#else
	195	# ifndef SETEUID_BREAKS_SETUID
	196	if (seteuid(pw->pw_uid) < 0)
	197	fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
	198	# endif
3c0ef626	199	if (setuid(pw->pw_uid) < 0)
ff2d7a98	200	fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
70791e56	201	#endif
	202
	203	/* Try restoration of GID if changed (test clearing of saved gid) */
416fd2a8	204	if (old_gid != pw->pw_gid &&
70791e56	205	(setgid(old_gid) != -1 \|\| setegid(old_gid) != -1))
	206	fatal("%s: was able to restore old [e]gid", __func__);
	207
	208	/* Verify GID drop was successful */
	209	if (getgid() != pw->pw_gid \|\| getegid() != pw->pw_gid) {
416fd2a8	210	fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
416fd2a8	211	__func__, (u_int)getgid(), (u_int)getegid(),
70791e56	212	(u_int)pw->pw_gid);
	213	}
	214
	215	#ifndef HAVE_CYGWIN
	216	/* Try restoration of UID if changed (test clearing of saved uid) */
416fd2a8	217	if (old_uid != pw->pw_uid &&
70791e56	218	(setuid(old_uid) != -1 \|\| seteuid(old_uid) != -1))
	219	fatal("%s: was able to restore old [e]uid", __func__);
	220	#endif
	221
	222	/* Verify UID drop was successful */
	223	if (getuid() != pw->pw_uid \|\| geteuid() != pw->pw_uid) {
416fd2a8	224	fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
416fd2a8	225	__func__, (u_int)getuid(), (u_int)geteuid(),
70791e56	226	(u_int)pw->pw_uid);
70791e56	227	}
3c0ef626	228	}