blob: 44c4cb626c8a7d10cee86d0da45cb013316f8878 [file] [log] [blame]
Damien Millerd4a8b7e1999-10-27 13:42:43 +10001/*
Damien Miller95def091999-11-25 00:26:21 +11002 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 * All rights reserved
Damien Miller95def091999-11-25 00:26:21 +11005 * Code for uid-swapping.
Damien Millere4340be2000-09-16 13:29:08 +11006 *
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".
Damien Miller95def091999-11-25 00:26:21 +110012 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100013
14#include "includes.h"
Damien Miller61d36802003-06-02 19:09:48 +100015RCSID("$OpenBSD: uidswap.c,v 1.24 2003/05/29 16:58:45 deraadt Exp $");
Damien Millerd4a8b7e1999-10-27 13:42:43 +100016
Ben Lindstrom226cfa02001-01-22 05:34:40 +000017#include "log.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100018#include "uidswap.h"
Damien Millera811d9a2004-02-24 13:05:11 +110019#include "xmalloc.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100020
Damien Miller95def091999-11-25 00:26:21 +110021/*
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 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100029
Ben Lindstrom4468b262001-04-26 23:03:37 +000030#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
Damien Millerd4a8b7e1999-10-27 13:42:43 +100031/* Lets assume that posix saved ids also work with seteuid, even though that
32 is not part of the posix specification. */
Ben Lindstrom4468b262001-04-26 23:03:37 +000033#define SAVED_IDS_WORK_WITH_SETEUID
34/* Saved effective uid. */
35static uid_t saved_euid = 0;
36static gid_t saved_egid = 0;
37#endif
Ben Lindstrom768f9752001-04-25 06:27:11 +000038
Damien Millerd4a8b7e1999-10-27 13:42:43 +100039/* Saved effective uid. */
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +000040static int privileged = 0;
41static int temporarily_use_uid_effective = 0;
Damien Millera811d9a2004-02-24 13:05:11 +110042static gid_t *saved_egroups = NULL, *user_groups = NULL;
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +000043static int saved_egroupslen = -1, user_groupslen = -1;
Ben Lindstrom768f9752001-04-25 06:27:11 +000044
Damien Miller95def091999-11-25 00:26:21 +110045/*
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 */
Damien Miller4af51302000-04-16 11:18:38 +100049void
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +000050temporarily_use_uid(struct passwd *pw)
Damien Millerd4a8b7e1999-10-27 13:42:43 +100051{
Ben Lindstrom768f9752001-04-25 06:27:11 +000052 /* Save the current euid, and egroups. */
Ben Lindstrom4468b262001-04-26 23:03:37 +000053#ifdef SAVED_IDS_WORK_WITH_SETEUID
Ben Lindstrom768f9752001-04-25 06:27:11 +000054 saved_euid = geteuid();
Ben Lindstrom4468b262001-04-26 23:03:37 +000055 saved_egid = getegid();
Ben Lindstrom1fa330c2002-07-23 21:29:49 +000056 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);
Ben Lindstrom768f9752001-04-25 06:27:11 +000059 if (saved_euid != 0) {
60 privileged = 0;
61 return;
62 }
Ben Lindstrom4468b262001-04-26 23:03:37 +000063#else
64 if (geteuid() != 0) {
65 privileged = 0;
66 return;
67 }
68#endif /* SAVED_IDS_WORK_WITH_SETEUID */
69
Ben Lindstrom768f9752001-04-25 06:27:11 +000070 privileged = 1;
71 temporarily_use_uid_effective = 1;
Damien Millera811d9a2004-02-24 13:05:11 +110072
73 saved_egroupslen = getgroups(0, NULL);
Ben Lindstrom768f9752001-04-25 06:27:11 +000074 if (saved_egroupslen < 0)
75 fatal("getgroups: %.100s", strerror(errno));
Damien Millera811d9a2004-02-24 13:05:11 +110076 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 */
Darren Tucker2359aa92004-02-24 13:17:30 +110082 if (saved_egroups != NULL)
Damien Millera811d9a2004-02-24 13:05:11 +110083 xfree(saved_egroups);
84 }
Ben Lindstrom768f9752001-04-25 06:27:11 +000085
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));
Damien Millera811d9a2004-02-24 13:05:11 +110091
92 user_groupslen = getgroups(0, NULL);
Ben Lindstrom768f9752001-04-25 06:27:11 +000093 if (user_groupslen < 0)
94 fatal("getgroups: %.100s", strerror(errno));
Damien Millera811d9a2004-02-24 13:05:11 +110095 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 }
Ben Lindstrom768f9752001-04-25 06:27:11 +0000104 }
105 /* Set the effective uid to the given (unprivileged) uid. */
Ben Lindstromf52373f2001-04-08 18:38:04 +0000106 if (setgroups(user_groupslen, user_groups) < 0)
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000107 fatal("setgroups: %.100s", strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000108#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 */
Ben Lindstromf52373f2001-04-08 18:38:04 +0000116 if (setegid(pw->pw_gid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000117 fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
Ben Lindstrom768f9752001-04-25 06:27:11 +0000118 strerror(errno));
119 if (seteuid(pw->pw_uid) == -1)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000120 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
Ben Lindstrom768f9752001-04-25 06:27:11 +0000121 strerror(errno));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000122}
Ben Lindstrom768f9752001-04-25 06:27:11 +0000123
Damien Miller95def091999-11-25 00:26:21 +1100124/*
Ben Lindstromee2786a2001-04-22 17:08:00 +0000125 * Restores to the original (privileged) uid.
Damien Miller95def091999-11-25 00:26:21 +1100126 */
Damien Miller4af51302000-04-16 11:18:38 +1000127void
Ben Lindstrom46c16222000-12-22 01:43:59 +0000128restore_uid(void)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000129{
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000130 /* it's a no-op unless privileged */
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000131 if (!privileged) {
132 debug("restore_uid: (unprivileged)");
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000133 return;
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000134 }
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000135 if (!temporarily_use_uid_effective)
136 fatal("restore_uid: temporarily_use_uid not effective");
Ben Lindstrom4468b262001-04-26 23:03:37 +0000137
138#ifdef SAVED_IDS_WORK_WITH_SETEUID
Ben Lindstrom18d2b5d2002-07-30 19:32:07 +0000139 debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
Ben Lindstromee2786a2001-04-22 17:08:00 +0000140 /* Set the effective uid back to the saved privileged uid. */
Damien Miller95def091999-11-25 00:26:21 +1100141 if (seteuid(saved_euid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000142 fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000143 if (setegid(saved_egid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000144 fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000145#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
Ben Lindstromf52373f2001-04-08 18:38:04 +0000155 if (setgroups(saved_egroupslen, saved_egroups) < 0)
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000156 fatal("setgroups: %.100s", strerror(errno));
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000157 temporarily_use_uid_effective = 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000158}
159
Damien Miller95def091999-11-25 00:26:21 +1100160/*
161 * Permanently sets all uids to the given uid. This cannot be
162 * called while temporarily_use_uid is effective.
163 */
Damien Miller4af51302000-04-16 11:18:38 +1000164void
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000165permanently_set_uid(struct passwd *pw)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000166{
Damien Miller5fe46a42003-06-05 09:53:31 +1000167 uid_t old_uid = getuid();
168 gid_t old_gid = getgid();
169
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000170 if (temporarily_use_uid_effective)
Ben Lindstromca8943e2002-06-06 20:42:04 +0000171 fatal("permanently_set_uid: temporarily_use_uid effective");
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000172 debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
173 (u_int)pw->pw_gid);
Damien Miller5fe46a42003-06-05 09:53:31 +1000174
Darren Tuckere937be32003-12-17 18:53:26 +1100175#if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID)
Damien Miller5fe46a42003-06-05 09:53:31 +1000176 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0)
177 fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
Darren Tucker9f18be62003-09-06 16:44:39 +1000178#elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
Damien Miller5fe46a42003-06-05 09:53:31 +1000179 if (setregid(pw->pw_gid, pw->pw_gid) < 0)
180 fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
181#else
Damien Miller61d36802003-06-02 19:09:48 +1000182 if (setegid(pw->pw_gid) < 0)
183 fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000184 if (setgid(pw->pw_gid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000185 fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000186#endif
187
Darren Tuckere937be32003-12-17 18:53:26 +1100188#if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
Damien Miller5fe46a42003-06-05 09:53:31 +1000189 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0)
190 fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Darren Tucker9f18be62003-09-06 16:44:39 +1000191#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
Darren Tucker400b8782003-06-06 10:46:04 +1000192 if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
193 fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000194#else
195# ifndef SETEUID_BREAKS_SETUID
Damien Miller61d36802003-06-02 19:09:48 +1000196 if (seteuid(pw->pw_uid) < 0)
197 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000198# endif
Ben Lindstromee2786a2001-04-22 17:08:00 +0000199 if (setuid(pw->pw_uid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000200 fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000201#endif
202
203 /* Try restoration of GID if changed (test clearing of saved gid) */
Damien Millera8e06ce2003-11-21 23:48:55 +1100204 if (old_gid != pw->pw_gid &&
Damien Miller5fe46a42003-06-05 09:53:31 +1000205 (setgid(old_gid) != -1 || setegid(old_gid) != -1))
Darren Tucker400b8782003-06-06 10:46:04 +1000206 fatal("%s: was able to restore old [e]gid", __func__);
Damien Miller5fe46a42003-06-05 09:53:31 +1000207
208 /* Verify GID drop was successful */
209 if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) {
Damien Millera8e06ce2003-11-21 23:48:55 +1100210 fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
211 __func__, (u_int)getgid(), (u_int)getegid(),
Damien Miller5fe46a42003-06-05 09:53:31 +1000212 (u_int)pw->pw_gid);
213 }
214
Darren Tuckerfbe3b362003-09-22 12:54:37 +1000215#ifndef HAVE_CYGWIN
Damien Miller5fe46a42003-06-05 09:53:31 +1000216 /* Try restoration of UID if changed (test clearing of saved uid) */
Damien Millera8e06ce2003-11-21 23:48:55 +1100217 if (old_uid != pw->pw_uid &&
Damien Miller5fe46a42003-06-05 09:53:31 +1000218 (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
Darren Tucker400b8782003-06-06 10:46:04 +1000219 fatal("%s: was able to restore old [e]uid", __func__);
Darren Tuckerfbe3b362003-09-22 12:54:37 +1000220#endif
Damien Miller5fe46a42003-06-05 09:53:31 +1000221
222 /* Verify UID drop was successful */
223 if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) {
Damien Millera8e06ce2003-11-21 23:48:55 +1100224 fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
225 __func__, (u_int)getuid(), (u_int)geteuid(),
Damien Miller5fe46a42003-06-05 09:53:31 +1000226 (u_int)pw->pw_uid);
227 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000228}