[openssh.git] / 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"

#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);
#ifndef HAVE_CYGWIN
	if (saved_euid != 0) {
		privileged = 0;
		return;
	}
#endif
#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

#ifndef HAVE_CYGWIN
	/* Try restoration of GID if changed (test clearing of saved gid) */
	if (old_gid != pw->pw_gid && pw->pw_uid != 0 &&
	    (setgid(old_gid) != -1 || setegid(old_gid) != -1))
		fatal("%s: was able to restore old [e]gid", __func__);
#endif

	/* 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
8efc0c15	1	/*
5260325f	2	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	3	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	4	* All rights reserved
5260325f	5	* Code for uid-swapping.
bcbf86ec	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".
5260325f	12	*/
8efc0c15	13
8efc0c15	14	#include "includes.h"
8efc0c15	15
42f11eb2	16	#include "log.h"
8efc0c15	17	#include "uidswap.h"
13dff404	18	#include "xmalloc.h"
8efc0c15	19
5260325f	20	/*
	21	* Note: all these functions must work in all of the following cases:
	22	* 1. euid=0, ruid=0
	23	* 2. euid=0, ruid!=0
	24	* 3. euid!=0, ruid!=0
	25	* Additionally, they must work regardless of whether the system has
	26	* POSIX saved uids or not.
	27	*/
8efc0c15	28
0096ac62	29	#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
8efc0c15	30	/* Lets assume that posix saved ids also work with seteuid, even though that
8efc0c15	31	is not part of the posix specification. */
0096ac62	32	#define SAVED_IDS_WORK_WITH_SETEUID
	33	/* Saved effective uid. */
	34	static uid_t saved_euid = 0;
	35	static gid_t saved_egid = 0;
	36	#endif
f8252c48	37
8efc0c15	38	/* Saved effective uid. */
63bd8c36	39	static int privileged = 0;
63bd8c36	40	static int temporarily_use_uid_effective = 0;
13dff404	41	static gid_t saved_egroups = NULL, user_groups = NULL;
63bd8c36	42	static int saved_egroupslen = -1, user_groupslen = -1;
f8252c48	43
5260325f	44	/*
	45	* Temporarily changes to the given uid. If the effective user
	46	* id is not root, this does nothing. This call cannot be nested.
	47	*/
6ae2364d	48	void
63bd8c36	49	temporarily_use_uid(struct passwd *pw)
8efc0c15	50	{
f8252c48	51	/* Save the current euid, and egroups. */
0096ac62	52	#ifdef SAVED_IDS_WORK_WITH_SETEUID
f8252c48	53	saved_euid = geteuid();
0096ac62	54	saved_egid = getegid();
0df3a240	55	debug("temporarily_use_uid: %u/%u (e=%u/%u)",
	56	(u_int)pw->pw_uid, (u_int)pw->pw_gid,
	57	(u_int)saved_euid, (u_int)saved_egid);
c2736f7f	58	#ifndef HAVE_CYGWIN
f8252c48	59	if (saved_euid != 0) {
	60	privileged = 0;
	61	return;
	62	}
c2736f7f	63	#endif
0096ac62	64	#else
	65	if (geteuid() != 0) {
	66	privileged = 0;
	67	return;
	68	}
	69	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
	70
f8252c48	71	privileged = 1;
f8252c48	72	temporarily_use_uid_effective = 1;
13dff404	73
13dff404	74	saved_egroupslen = getgroups(0, NULL);
f8252c48	75	if (saved_egroupslen < 0)
f8252c48	76	fatal("getgroups: %.100s", strerror(errno));
13dff404	77	if (saved_egroupslen > 0) {
	78	saved_egroups = xrealloc(saved_egroups,
	79	saved_egroupslen * sizeof(gid_t));
	80	if (getgroups(saved_egroupslen, saved_egroups) < 0)
	81	fatal("getgroups: %.100s", strerror(errno));
	82	} else { /* saved_egroupslen == 0 */
972fc531	83	if (saved_egroups != NULL)
13dff404	84	xfree(saved_egroups);
13dff404	85	}
f8252c48	86
	87	/* set and save the user's groups */
	88	if (user_groupslen == -1) {
	89	if (initgroups(pw->pw_name, pw->pw_gid) < 0)
	90	fatal("initgroups: %s: %.100s", pw->pw_name,
	91	strerror(errno));
13dff404	92
13dff404	93	user_groupslen = getgroups(0, NULL);
f8252c48	94	if (user_groupslen < 0)
f8252c48	95	fatal("getgroups: %.100s", strerror(errno));
13dff404	96	if (user_groupslen > 0) {
	97	user_groups = xrealloc(user_groups,
	98	user_groupslen * sizeof(gid_t));
	99	if (getgroups(user_groupslen, user_groups) < 0)
	100	fatal("getgroups: %.100s", strerror(errno));
	101	} else { /* user_groupslen == 0 */
	102	if (user_groups)
	103	xfree(user_groups);
	104	}
f8252c48	105	}
f8252c48	106	/* Set the effective uid to the given (unprivileged) uid. */
d98d029a	107	if (setgroups(user_groupslen, user_groups) < 0)
63bd8c36	108	fatal("setgroups: %.100s", strerror(errno));
0096ac62	109	#ifndef SAVED_IDS_WORK_WITH_SETEUID
	110	/* Propagate the privileged gid to all of our gids. */
	111	if (setgid(getegid()) < 0)
	112	debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
	113	/* Propagate the privileged uid to all of our uids. */
	114	if (setuid(geteuid()) < 0)
	115	debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
	116	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
d98d029a	117	if (setegid(pw->pw_gid) < 0)
caa49784	118	fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
f8252c48	119	strerror(errno));
f8252c48	120	if (seteuid(pw->pw_uid) == -1)
caa49784	121	fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
f8252c48	122	strerror(errno));
8efc0c15	123	}
f8252c48	124
5260325f	125	/*
a3626e12	126	* Restores to the original (privileged) uid.
5260325f	127	*/
6ae2364d	128	void
1e3b8b07	129	restore_uid(void)
8efc0c15	130	{
63bd8c36	131	/* it's a no-op unless privileged */
0df3a240	132	if (!privileged) {
0df3a240	133	debug("restore_uid: (unprivileged)");
63bd8c36	134	return;
0df3a240	135	}
63bd8c36	136	if (!temporarily_use_uid_effective)
63bd8c36	137	fatal("restore_uid: temporarily_use_uid not effective");
0096ac62	138
0096ac62	139	#ifdef SAVED_IDS_WORK_WITH_SETEUID
13979d47	140	debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
a3626e12	141	/* Set the effective uid back to the saved privileged uid. */
5260325f	142	if (seteuid(saved_euid) < 0)
caa49784	143	fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
0096ac62	144	if (setegid(saved_egid) < 0)
caa49784	145	fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
0096ac62	146	#else /* SAVED_IDS_WORK_WITH_SETEUID */
	147	/*
	148	* We are unable to restore the real uid to its unprivileged value.
	149	* Propagate the real uid (usually more privileged) to effective uid
	150	* as well.
	151	*/
	152	setuid(getuid());
	153	setgid(getgid());
	154	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
	155
d98d029a	156	if (setgroups(saved_egroupslen, saved_egroups) < 0)
63bd8c36	157	fatal("setgroups: %.100s", strerror(errno));
63bd8c36	158	temporarily_use_uid_effective = 0;
8efc0c15	159	}
8efc0c15	160
5260325f	161	/*
	162	* Permanently sets all uids to the given uid. This cannot be
	163	* called while temporarily_use_uid is effective.
	164	*/
6ae2364d	165	void
63bd8c36	166	permanently_set_uid(struct passwd *pw)
8efc0c15	167	{
688eed4a	168	uid_t old_uid = getuid();
	169	gid_t old_gid = getgid();
	170
63bd8c36	171	if (temporarily_use_uid_effective)
95f20fe8	172	fatal("permanently_set_uid: temporarily_use_uid effective");
0df3a240	173	debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
0df3a240	174	(u_int)pw->pw_gid);
688eed4a	175
9a3fe0e2	176	#if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID)
688eed4a	177	if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0)
688eed4a	178	fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
3b8dff69	179	#elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
688eed4a	180	if (setregid(pw->pw_gid, pw->pw_gid) < 0)
	181	fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
	182	#else
fa5120a0	183	if (setegid(pw->pw_gid) < 0)
fa5120a0	184	fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
63bd8c36	185	if (setgid(pw->pw_gid) < 0)
caa49784	186	fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
688eed4a	187	#endif
688eed4a	188
9a3fe0e2	189	#if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
688eed4a	190	if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0)
688eed4a	191	fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
3b8dff69	192	#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
f5db6a03	193	if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
f5db6a03	194	fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a	195	#else
688eed4a	196	# ifndef SETEUID_BREAKS_SETUID
fa5120a0	197	if (seteuid(pw->pw_uid) < 0)
fa5120a0	198	fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a	199	# endif
a3626e12	200	if (setuid(pw->pw_uid) < 0)
caa49784	201	fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a	202	#endif
688eed4a	203
8f817407	204	#ifndef HAVE_CYGWIN
688eed4a	205	/* Try restoration of GID if changed (test clearing of saved gid) */
8f817407	206	if (old_gid != pw->pw_gid && pw->pw_uid != 0 &&
688eed4a	207	(setgid(old_gid) != -1 \|\| setegid(old_gid) != -1))
f5db6a03	208	fatal("%s: was able to restore old [e]gid", __func__);
8f817407	209	#endif
688eed4a	210
	211	/* Verify GID drop was successful */
	212	if (getgid() != pw->pw_gid \|\| getegid() != pw->pw_gid) {
aff51935	213	fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
aff51935	214	__func__, (u_int)getgid(), (u_int)getegid(),
688eed4a	215	(u_int)pw->pw_gid);
	216	}
	217
51e7d820	218	#ifndef HAVE_CYGWIN
688eed4a	219	/* Try restoration of UID if changed (test clearing of saved uid) */
aff51935	220	if (old_uid != pw->pw_uid &&
688eed4a	221	(setuid(old_uid) != -1 \|\| seteuid(old_uid) != -1))
f5db6a03	222	fatal("%s: was able to restore old [e]uid", __func__);
51e7d820	223	#endif
688eed4a	224
	225	/* Verify UID drop was successful */
	226	if (getuid() != pw->pw_uid \|\| geteuid() != pw->pw_uid) {
aff51935	227	fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
aff51935	228	__func__, (u_int)getuid(), (u_int)geteuid(),
688eed4a	229	(u_int)pw->pw_uid);
688eed4a	230	}
8efc0c15	231	}