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Damien Millerd7834352006-08-05 12:39:39 +10001/* $OpenBSD: uidswap.c,v 1.35 2006/08/03 03:34:42 deraadt 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
Damien Miller8dbffe72006-08-05 11:02:17 +100017#include <sys/param.h>
Darren Tucker39972492006-07-12 22:22:46 +100018#include <errno.h>
Damien Miller9f2abc42006-07-10 20:53:08 +100019#include <pwd.h>
Damien Millere3476ed2006-07-24 14:13:33 +100020#include <string.h>
Damien Millere6b3b612006-07-24 14:01:23 +100021#include <unistd.h>
Damien Millerd7834352006-08-05 12:39:39 +100022#include <stdarg.h>
Damien Miller9f2abc42006-07-10 20:53:08 +100023
Damien Miller427a1d52006-07-10 20:20:33 +100024#include <grp.h>
25
Ben Lindstrom226cfa02001-01-22 05:34:40 +000026#include "log.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100027#include "uidswap.h"
Damien Millera811d9a2004-02-24 13:05:11 +110028#include "xmalloc.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100029
Damien Miller95def091999-11-25 00:26:21 +110030/*
31 * Note: all these functions must work in all of the following cases:
32 * 1. euid=0, ruid=0
33 * 2. euid=0, ruid!=0
34 * 3. euid!=0, ruid!=0
35 * Additionally, they must work regardless of whether the system has
36 * POSIX saved uids or not.
37 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100038
Ben Lindstrom4468b262001-04-26 23:03:37 +000039#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
Damien Millerd4a8b7e1999-10-27 13:42:43 +100040/* Lets assume that posix saved ids also work with seteuid, even though that
41 is not part of the posix specification. */
Ben Lindstrom4468b262001-04-26 23:03:37 +000042#define SAVED_IDS_WORK_WITH_SETEUID
43/* Saved effective uid. */
44static uid_t saved_euid = 0;
45static gid_t saved_egid = 0;
46#endif
Ben Lindstrom768f9752001-04-25 06:27:11 +000047
Damien Millerd4a8b7e1999-10-27 13:42:43 +100048/* Saved effective uid. */
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +000049static int privileged = 0;
50static int temporarily_use_uid_effective = 0;
Damien Millera811d9a2004-02-24 13:05:11 +110051static gid_t *saved_egroups = NULL, *user_groups = NULL;
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +000052static int saved_egroupslen = -1, user_groupslen = -1;
Ben Lindstrom768f9752001-04-25 06:27:11 +000053
Damien Miller95def091999-11-25 00:26:21 +110054/*
55 * Temporarily changes to the given uid. If the effective user
56 * id is not root, this does nothing. This call cannot be nested.
57 */
Damien Miller4af51302000-04-16 11:18:38 +100058void
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +000059temporarily_use_uid(struct passwd *pw)
Damien Millerd4a8b7e1999-10-27 13:42:43 +100060{
Ben Lindstrom768f9752001-04-25 06:27:11 +000061 /* Save the current euid, and egroups. */
Ben Lindstrom4468b262001-04-26 23:03:37 +000062#ifdef SAVED_IDS_WORK_WITH_SETEUID
Ben Lindstrom768f9752001-04-25 06:27:11 +000063 saved_euid = geteuid();
Ben Lindstrom4468b262001-04-26 23:03:37 +000064 saved_egid = getegid();
Ben Lindstrom1fa330c2002-07-23 21:29:49 +000065 debug("temporarily_use_uid: %u/%u (e=%u/%u)",
66 (u_int)pw->pw_uid, (u_int)pw->pw_gid,
67 (u_int)saved_euid, (u_int)saved_egid);
Darren Tucker2ea9b182005-02-22 17:57:13 +110068#ifndef HAVE_CYGWIN
Ben Lindstrom768f9752001-04-25 06:27:11 +000069 if (saved_euid != 0) {
70 privileged = 0;
71 return;
72 }
Darren Tucker2ea9b182005-02-22 17:57:13 +110073#endif
Ben Lindstrom4468b262001-04-26 23:03:37 +000074#else
75 if (geteuid() != 0) {
76 privileged = 0;
77 return;
78 }
79#endif /* SAVED_IDS_WORK_WITH_SETEUID */
80
Ben Lindstrom768f9752001-04-25 06:27:11 +000081 privileged = 1;
82 temporarily_use_uid_effective = 1;
Damien Millera811d9a2004-02-24 13:05:11 +110083
84 saved_egroupslen = getgroups(0, NULL);
Ben Lindstrom768f9752001-04-25 06:27:11 +000085 if (saved_egroupslen < 0)
86 fatal("getgroups: %.100s", strerror(errno));
Damien Millera811d9a2004-02-24 13:05:11 +110087 if (saved_egroupslen > 0) {
88 saved_egroups = xrealloc(saved_egroups,
Damien Miller36812092006-03-26 14:22:47 +110089 saved_egroupslen, sizeof(gid_t));
Damien Millera811d9a2004-02-24 13:05:11 +110090 if (getgroups(saved_egroupslen, saved_egroups) < 0)
91 fatal("getgroups: %.100s", strerror(errno));
92 } else { /* saved_egroupslen == 0 */
Darren Tucker2359aa92004-02-24 13:17:30 +110093 if (saved_egroups != NULL)
Damien Millera811d9a2004-02-24 13:05:11 +110094 xfree(saved_egroups);
95 }
Ben Lindstrom768f9752001-04-25 06:27:11 +000096
97 /* set and save the user's groups */
98 if (user_groupslen == -1) {
99 if (initgroups(pw->pw_name, pw->pw_gid) < 0)
100 fatal("initgroups: %s: %.100s", pw->pw_name,
101 strerror(errno));
Damien Millera811d9a2004-02-24 13:05:11 +1100102
103 user_groupslen = getgroups(0, NULL);
Ben Lindstrom768f9752001-04-25 06:27:11 +0000104 if (user_groupslen < 0)
105 fatal("getgroups: %.100s", strerror(errno));
Damien Millera811d9a2004-02-24 13:05:11 +1100106 if (user_groupslen > 0) {
107 user_groups = xrealloc(user_groups,
Damien Miller36812092006-03-26 14:22:47 +1100108 user_groupslen, sizeof(gid_t));
Damien Millera811d9a2004-02-24 13:05:11 +1100109 if (getgroups(user_groupslen, user_groups) < 0)
110 fatal("getgroups: %.100s", strerror(errno));
111 } else { /* user_groupslen == 0 */
112 if (user_groups)
113 xfree(user_groups);
114 }
Ben Lindstrom768f9752001-04-25 06:27:11 +0000115 }
116 /* Set the effective uid to the given (unprivileged) uid. */
Ben Lindstromf52373f2001-04-08 18:38:04 +0000117 if (setgroups(user_groupslen, user_groups) < 0)
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000118 fatal("setgroups: %.100s", strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000119#ifndef SAVED_IDS_WORK_WITH_SETEUID
120 /* Propagate the privileged gid to all of our gids. */
121 if (setgid(getegid()) < 0)
122 debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
123 /* Propagate the privileged uid to all of our uids. */
124 if (setuid(geteuid()) < 0)
125 debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
126#endif /* SAVED_IDS_WORK_WITH_SETEUID */
Ben Lindstromf52373f2001-04-08 18:38:04 +0000127 if (setegid(pw->pw_gid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000128 fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
Ben Lindstrom768f9752001-04-25 06:27:11 +0000129 strerror(errno));
130 if (seteuid(pw->pw_uid) == -1)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000131 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
Ben Lindstrom768f9752001-04-25 06:27:11 +0000132 strerror(errno));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000133}
Ben Lindstrom768f9752001-04-25 06:27:11 +0000134
Damien Miller2e5fe882006-06-13 13:10:00 +1000135void
136permanently_drop_suid(uid_t uid)
137{
138 uid_t old_uid = getuid();
139
140 debug("permanently_drop_suid: %u", (u_int)uid);
141#if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
142 if (setresuid(uid, uid, uid) < 0)
143 fatal("setresuid %u: %.100s", (u_int)uid, strerror(errno));
144#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
145 if (setreuid(uid, uid) < 0)
146 fatal("setreuid %u: %.100s", (u_int)uid, strerror(errno));
147#else
148# ifndef SETEUID_BREAKS_SETUID
149 if (seteuid(uid) < 0)
150 fatal("seteuid %u: %.100s", (u_int)uid, strerror(errno));
151# endif
152 if (setuid(uid) < 0)
153 fatal("setuid %u: %.100s", (u_int)uid, strerror(errno));
154#endif
155
156#ifndef HAVE_CYGWIN
157 /* Try restoration of UID if changed (test clearing of saved uid) */
158 if (old_uid != uid &&
159 (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
160 fatal("%s: was able to restore old [e]uid", __func__);
161#endif
162
163 /* Verify UID drop was successful */
164 if (getuid() != uid || geteuid() != uid) {
165 fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
166 __func__, (u_int)getuid(), (u_int)geteuid(), (u_int)uid);
167 }
168}
169
Damien Miller95def091999-11-25 00:26:21 +1100170/*
Ben Lindstromee2786a2001-04-22 17:08:00 +0000171 * Restores to the original (privileged) uid.
Damien Miller95def091999-11-25 00:26:21 +1100172 */
Damien Miller4af51302000-04-16 11:18:38 +1000173void
Ben Lindstrom46c16222000-12-22 01:43:59 +0000174restore_uid(void)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000175{
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000176 /* it's a no-op unless privileged */
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000177 if (!privileged) {
178 debug("restore_uid: (unprivileged)");
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000179 return;
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000180 }
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000181 if (!temporarily_use_uid_effective)
182 fatal("restore_uid: temporarily_use_uid not effective");
Ben Lindstrom4468b262001-04-26 23:03:37 +0000183
184#ifdef SAVED_IDS_WORK_WITH_SETEUID
Ben Lindstrom18d2b5d2002-07-30 19:32:07 +0000185 debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
Ben Lindstromee2786a2001-04-22 17:08:00 +0000186 /* Set the effective uid back to the saved privileged uid. */
Damien Miller95def091999-11-25 00:26:21 +1100187 if (seteuid(saved_euid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000188 fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000189 if (setegid(saved_egid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000190 fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000191#else /* SAVED_IDS_WORK_WITH_SETEUID */
192 /*
193 * We are unable to restore the real uid to its unprivileged value.
194 * Propagate the real uid (usually more privileged) to effective uid
195 * as well.
196 */
197 setuid(getuid());
198 setgid(getgid());
199#endif /* SAVED_IDS_WORK_WITH_SETEUID */
200
Ben Lindstromf52373f2001-04-08 18:38:04 +0000201 if (setgroups(saved_egroupslen, saved_egroups) < 0)
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000202 fatal("setgroups: %.100s", strerror(errno));
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000203 temporarily_use_uid_effective = 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000204}
205
Damien Miller95def091999-11-25 00:26:21 +1100206/*
207 * Permanently sets all uids to the given uid. This cannot be
208 * called while temporarily_use_uid is effective.
209 */
Damien Miller4af51302000-04-16 11:18:38 +1000210void
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000211permanently_set_uid(struct passwd *pw)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000212{
Damien Miller5fe46a42003-06-05 09:53:31 +1000213 uid_t old_uid = getuid();
214 gid_t old_gid = getgid();
215
Damien Miller6b4069a2006-06-13 13:05:15 +1000216 if (pw == NULL)
217 fatal("permanently_set_uid: no user given");
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000218 if (temporarily_use_uid_effective)
Ben Lindstromca8943e2002-06-06 20:42:04 +0000219 fatal("permanently_set_uid: temporarily_use_uid effective");
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000220 debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
221 (u_int)pw->pw_gid);
Damien Miller5fe46a42003-06-05 09:53:31 +1000222
Darren Tuckere937be32003-12-17 18:53:26 +1100223#if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID)
Damien Miller5fe46a42003-06-05 09:53:31 +1000224 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0)
225 fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
Darren Tucker9f18be62003-09-06 16:44:39 +1000226#elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
Damien Miller5fe46a42003-06-05 09:53:31 +1000227 if (setregid(pw->pw_gid, pw->pw_gid) < 0)
228 fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
229#else
Damien Miller61d36802003-06-02 19:09:48 +1000230 if (setegid(pw->pw_gid) < 0)
231 fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000232 if (setgid(pw->pw_gid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000233 fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000234#endif
235
Damien Miller1598d6b2009-01-21 16:04:24 +1100236#ifdef __APPLE__
237 /*
238 * OS X requires initgroups after setgid to opt back into
239 * memberd support for >16 supplemental groups.
240 */
241 if (initgroups(pw->pw_name, pw->pw_gid) < 0)
242 fatal("initgroups %.100s %u: %.100s",
243 pw->pw_name, (u_int)pw->pw_gid, strerror(errno));
244#endif
245
Darren Tuckere937be32003-12-17 18:53:26 +1100246#if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
Damien Miller5fe46a42003-06-05 09:53:31 +1000247 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0)
248 fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Darren Tucker9f18be62003-09-06 16:44:39 +1000249#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
Darren Tucker400b8782003-06-06 10:46:04 +1000250 if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
251 fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000252#else
253# ifndef SETEUID_BREAKS_SETUID
Damien Miller61d36802003-06-02 19:09:48 +1000254 if (seteuid(pw->pw_uid) < 0)
255 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000256# endif
Ben Lindstromee2786a2001-04-22 17:08:00 +0000257 if (setuid(pw->pw_uid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000258 fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Damien Miller5fe46a42003-06-05 09:53:31 +1000259#endif
260
Darren Tucker35beadd2004-10-19 16:33:33 +1000261#ifndef HAVE_CYGWIN
Damien Miller5fe46a42003-06-05 09:53:31 +1000262 /* Try restoration of GID if changed (test clearing of saved gid) */
Darren Tucker35beadd2004-10-19 16:33:33 +1000263 if (old_gid != pw->pw_gid && pw->pw_uid != 0 &&
Damien Miller5fe46a42003-06-05 09:53:31 +1000264 (setgid(old_gid) != -1 || setegid(old_gid) != -1))
Darren Tucker400b8782003-06-06 10:46:04 +1000265 fatal("%s: was able to restore old [e]gid", __func__);
Darren Tucker35beadd2004-10-19 16:33:33 +1000266#endif
Damien Miller5fe46a42003-06-05 09:53:31 +1000267
268 /* Verify GID drop was successful */
269 if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) {
Damien Millera8e06ce2003-11-21 23:48:55 +1100270 fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
271 __func__, (u_int)getgid(), (u_int)getegid(),
Damien Miller5fe46a42003-06-05 09:53:31 +1000272 (u_int)pw->pw_gid);
273 }
274
Darren Tuckerfbe3b362003-09-22 12:54:37 +1000275#ifndef HAVE_CYGWIN
Damien Miller5fe46a42003-06-05 09:53:31 +1000276 /* Try restoration of UID if changed (test clearing of saved uid) */
Damien Millera8e06ce2003-11-21 23:48:55 +1100277 if (old_uid != pw->pw_uid &&
Damien Miller5fe46a42003-06-05 09:53:31 +1000278 (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
Darren Tucker400b8782003-06-06 10:46:04 +1000279 fatal("%s: was able to restore old [e]uid", __func__);
Darren Tuckerfbe3b362003-09-22 12:54:37 +1000280#endif
Damien Miller5fe46a42003-06-05 09:53:31 +1000281
282 /* Verify UID drop was successful */
283 if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) {
Damien Millera8e06ce2003-11-21 23:48:55 +1100284 fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
285 __func__, (u_int)getuid(), (u_int)geteuid(),
Damien Miller5fe46a42003-06-05 09:53:31 +1000286 (u_int)pw->pw_uid);
287 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000288}