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Damien Miller2282c6e2006-04-23 12:11:57 +10001/* $OpenBSD: uidswap.c,v 1.27 2006/04/22 04:06:51 djm Exp $ */
Damien Millerd4a8b7e1999-10-27 13:42:43 +10002/*
Damien Miller95def091999-11-25 00:26:21 +11003 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
Damien Miller95def091999-11-25 00:26:21 +11006 * Code for uid-swapping.
Damien Millere4340be2000-09-16 13:29:08 +11007 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
Damien Miller95def091999-11-25 00:26:21 +110013 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100014
15#include "includes.h"
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);
Darren Tucker2ea9b182005-02-22 17:57:13 +110059#ifndef HAVE_CYGWIN
Ben Lindstrom768f9752001-04-25 06:27:11 +000060 if (saved_euid != 0) {
61 privileged = 0;
62 return;
63 }
Darren Tucker2ea9b182005-02-22 17:57:13 +110064#endif
Ben Lindstrom4468b262001-04-26 23:03:37 +000065#else
66 if (geteuid() != 0) {
67 privileged = 0;
68 return;
69 }
70#endif /* SAVED_IDS_WORK_WITH_SETEUID */
71
Ben Lindstrom768f9752001-04-25 06:27:11 +000072 privileged = 1;
73 temporarily_use_uid_effective = 1;
Damien Millera811d9a2004-02-24 13:05:11 +110074
75 saved_egroupslen = getgroups(0, NULL);
Ben Lindstrom768f9752001-04-25 06:27:11 +000076 if (saved_egroupslen < 0)
77 fatal("getgroups: %.100s", strerror(errno));
Damien Millera811d9a2004-02-24 13:05:11 +110078 if (saved_egroupslen > 0) {
79 saved_egroups = xrealloc(saved_egroups,
Damien Miller36812092006-03-26 14:22:47 +110080 saved_egroupslen, sizeof(gid_t));
Damien Millera811d9a2004-02-24 13:05:11 +110081 if (getgroups(saved_egroupslen, saved_egroups) < 0)
82 fatal("getgroups: %.100s", strerror(errno));
83 } else { /* saved_egroupslen == 0 */
Darren Tucker2359aa92004-02-24 13:17:30 +110084 if (saved_egroups != NULL)
Damien Millera811d9a2004-02-24 13:05:11 +110085 xfree(saved_egroups);
86 }
Ben Lindstrom768f9752001-04-25 06:27:11 +000087
88 /* set and save the user's groups */
89 if (user_groupslen == -1) {
90 if (initgroups(pw->pw_name, pw->pw_gid) < 0)
91 fatal("initgroups: %s: %.100s", pw->pw_name,
92 strerror(errno));
Damien Millera811d9a2004-02-24 13:05:11 +110093
94 user_groupslen = getgroups(0, NULL);
Ben Lindstrom768f9752001-04-25 06:27:11 +000095 if (user_groupslen < 0)
96 fatal("getgroups: %.100s", strerror(errno));
Damien Millera811d9a2004-02-24 13:05:11 +110097 if (user_groupslen > 0) {
98 user_groups = xrealloc(user_groups,
Damien Miller36812092006-03-26 14:22:47 +110099 user_groupslen, sizeof(gid_t));
Damien Millera811d9a2004-02-24 13:05:11 +1100100 if (getgroups(user_groupslen, user_groups) < 0)
101 fatal("getgroups: %.100s", strerror(errno));
102 } else { /* user_groupslen == 0 */
103 if (user_groups)
104 xfree(user_groups);
105 }
Ben Lindstrom768f9752001-04-25 06:27:11 +0000106 }
107 /* Set the effective uid to the given (unprivileged) uid. */
Ben Lindstromf52373f2001-04-08 18:38:04 +0000108 if (setgroups(user_groupslen, user_groups) < 0)
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000109 fatal("setgroups: %.100s", strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000110#ifndef SAVED_IDS_WORK_WITH_SETEUID
111 /* Propagate the privileged gid to all of our gids. */
112 if (setgid(getegid()) < 0)
113 debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
114 /* Propagate the privileged uid to all of our uids. */
115 if (setuid(geteuid()) < 0)
116 debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
117#endif /* SAVED_IDS_WORK_WITH_SETEUID */
Ben Lindstromf52373f2001-04-08 18:38:04 +0000118 if (setegid(pw->pw_gid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000119 fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
Ben Lindstrom768f9752001-04-25 06:27:11 +0000120 strerror(errno));
121 if (seteuid(pw->pw_uid) == -1)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000122 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
Ben Lindstrom768f9752001-04-25 06:27:11 +0000123 strerror(errno));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000124}
Ben Lindstrom768f9752001-04-25 06:27:11 +0000125
Damien Miller95def091999-11-25 00:26:21 +1100126/*
Ben Lindstromee2786a2001-04-22 17:08:00 +0000127 * Restores to the original (privileged) uid.
Damien Miller95def091999-11-25 00:26:21 +1100128 */
Damien Miller4af51302000-04-16 11:18:38 +1000129void
Ben Lindstrom46c16222000-12-22 01:43:59 +0000130restore_uid(void)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000131{
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000132 /* it's a no-op unless privileged */
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000133 if (!privileged) {
134 debug("restore_uid: (unprivileged)");
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000135 return;
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000136 }
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000137 if (!temporarily_use_uid_effective)
138 fatal("restore_uid: temporarily_use_uid not effective");
Ben Lindstrom4468b262001-04-26 23:03:37 +0000139
140#ifdef SAVED_IDS_WORK_WITH_SETEUID
Ben Lindstrom18d2b5d2002-07-30 19:32:07 +0000141 debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
Ben Lindstromee2786a2001-04-22 17:08:00 +0000142 /* Set the effective uid back to the saved privileged uid. */
Damien Miller95def091999-11-25 00:26:21 +1100143 if (seteuid(saved_euid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000144 fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000145 if (setegid(saved_egid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000146 fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000147#else /* SAVED_IDS_WORK_WITH_SETEUID */
148 /*
149 * We are unable to restore the real uid to its unprivileged value.
150 * Propagate the real uid (usually more privileged) to effective uid
151 * as well.
152 */
153 setuid(getuid());
154 setgid(getgid());
155#endif /* SAVED_IDS_WORK_WITH_SETEUID */
156
Ben Lindstromf52373f2001-04-08 18:38:04 +0000157 if (setgroups(saved_egroupslen, saved_egroups) < 0)
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000158 fatal("setgroups: %.100s", strerror(errno));
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000159 temporarily_use_uid_effective = 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000160}
161
Damien Miller95def091999-11-25 00:26:21 +1100162/*
163 * Permanently sets all uids to the given uid. This cannot be
164 * called while temporarily_use_uid is effective.
165 */
Damien Miller4af51302000-04-16 11:18:38 +1000166void
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000167permanently_set_uid(struct passwd *pw)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000168{
Damien Miller5fe46a42003-06-05 09:53:31 +1000169 uid_t old_uid = getuid();
170 gid_t old_gid = getgid();
171
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000172 if (temporarily_use_uid_effective)
Ben Lindstromca8943e2002-06-06 20:42:04 +0000173 fatal("permanently_set_uid: temporarily_use_uid effective");
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000174 debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
175 (u_int)pw->pw_gid);
Damien Miller5fe46a42003-06-05 09:53:31 +1000176
Darren Tuckere937be32003-12-17 18:53:26 +1100177#if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID)
Damien Miller5fe46a42003-06-05 09:53:31 +1000178 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0)
179 fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
Darren Tucker9f18be62003-09-06 16:44:39 +1000180#elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
Damien Miller5fe46a42003-06-05 09:53:31 +1000181 if (setregid(pw->pw_gid, pw->pw_gid) < 0)
182 fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
183#else
Damien Miller61d36802003-06-02 19:09:48 +1000184 if (setegid(pw->pw_gid) < 0)
185 fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000186 if (setgid(pw->pw_gid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000187 fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000188#endif
189
Darren Tuckere937be32003-12-17 18:53:26 +1100190#if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
Damien Miller5fe46a42003-06-05 09:53:31 +1000191 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0)
192 fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Darren Tucker9f18be62003-09-06 16:44:39 +1000193#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
Darren Tucker400b8782003-06-06 10:46:04 +1000194 if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
195 fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000196#else
197# ifndef SETEUID_BREAKS_SETUID
Damien Miller61d36802003-06-02 19:09:48 +1000198 if (seteuid(pw->pw_uid) < 0)
199 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000200# endif
Ben Lindstromee2786a2001-04-22 17:08:00 +0000201 if (setuid(pw->pw_uid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000202 fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000203#endif
204
Darren Tucker35beadd2004-10-19 16:33:33 +1000205#ifndef HAVE_CYGWIN
Damien Miller5fe46a42003-06-05 09:53:31 +1000206 /* Try restoration of GID if changed (test clearing of saved gid) */
Darren Tucker35beadd2004-10-19 16:33:33 +1000207 if (old_gid != pw->pw_gid && pw->pw_uid != 0 &&
Damien Miller5fe46a42003-06-05 09:53:31 +1000208 (setgid(old_gid) != -1 || setegid(old_gid) != -1))
Darren Tucker400b8782003-06-06 10:46:04 +1000209 fatal("%s: was able to restore old [e]gid", __func__);
Darren Tucker35beadd2004-10-19 16:33:33 +1000210#endif
Damien Miller5fe46a42003-06-05 09:53:31 +1000211
212 /* Verify GID drop was successful */
213 if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) {
Damien Millera8e06ce2003-11-21 23:48:55 +1100214 fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
215 __func__, (u_int)getgid(), (u_int)getegid(),
Damien Miller5fe46a42003-06-05 09:53:31 +1000216 (u_int)pw->pw_gid);
217 }
218
Darren Tuckerfbe3b362003-09-22 12:54:37 +1000219#ifndef HAVE_CYGWIN
Damien Miller5fe46a42003-06-05 09:53:31 +1000220 /* Try restoration of UID if changed (test clearing of saved uid) */
Damien Millera8e06ce2003-11-21 23:48:55 +1100221 if (old_uid != pw->pw_uid &&
Damien Miller5fe46a42003-06-05 09:53:31 +1000222 (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
Darren Tucker400b8782003-06-06 10:46:04 +1000223 fatal("%s: was able to restore old [e]uid", __func__);
Darren Tuckerfbe3b362003-09-22 12:54:37 +1000224#endif
Damien Miller5fe46a42003-06-05 09:53:31 +1000225
226 /* Verify UID drop was successful */
227 if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) {
Damien Millera8e06ce2003-11-21 23:48:55 +1100228 fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
229 __func__, (u_int)getuid(), (u_int)geteuid(),
Damien Miller5fe46a42003-06-05 09:53:31 +1000230 (u_int)pw->pw_uid);
231 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000232}