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- stevesk@cvs.openbsd.org 2006/07/02 18:36:47
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3c33c1b6 1/* $OpenBSD: uidswap.c,v 1.29 2006/06/08 14:45:49 markus Exp $ */
8efc0c15 2/*
5260325f 3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
5260325f 6 * Code for uid-swapping.
bcbf86ec 7 *
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".
5260325f 13 */
8efc0c15 14
15#include "includes.h"
8efc0c15 16
42f11eb2 17#include "log.h"
8efc0c15 18#include "uidswap.h"
13dff404 19#include "xmalloc.h"
8efc0c15 20
5260325f 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 */
8efc0c15 29
0096ac62 30#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
8efc0c15 31/* Lets assume that posix saved ids also work with seteuid, even though that
32 is not part of the posix specification. */
0096ac62 33#define SAVED_IDS_WORK_WITH_SETEUID
34/* Saved effective uid. */
35static uid_t saved_euid = 0;
36static gid_t saved_egid = 0;
37#endif
f8252c48 38
8efc0c15 39/* Saved effective uid. */
63bd8c36 40static int privileged = 0;
41static int temporarily_use_uid_effective = 0;
13dff404 42static gid_t *saved_egroups = NULL, *user_groups = NULL;
63bd8c36 43static int saved_egroupslen = -1, user_groupslen = -1;
f8252c48 44
5260325f 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 */
6ae2364d 49void
63bd8c36 50temporarily_use_uid(struct passwd *pw)
8efc0c15 51{
f8252c48 52 /* Save the current euid, and egroups. */
0096ac62 53#ifdef SAVED_IDS_WORK_WITH_SETEUID
f8252c48 54 saved_euid = geteuid();
0096ac62 55 saved_egid = getegid();
0df3a240 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);
c2736f7f 59#ifndef HAVE_CYGWIN
f8252c48 60 if (saved_euid != 0) {
61 privileged = 0;
62 return;
63 }
c2736f7f 64#endif
0096ac62 65#else
66 if (geteuid() != 0) {
67 privileged = 0;
68 return;
69 }
70#endif /* SAVED_IDS_WORK_WITH_SETEUID */
71
f8252c48 72 privileged = 1;
73 temporarily_use_uid_effective = 1;
13dff404 74
75 saved_egroupslen = getgroups(0, NULL);
f8252c48 76 if (saved_egroupslen < 0)
77 fatal("getgroups: %.100s", strerror(errno));
13dff404 78 if (saved_egroupslen > 0) {
79 saved_egroups = xrealloc(saved_egroups,
c5d10563 80 saved_egroupslen, sizeof(gid_t));
13dff404 81 if (getgroups(saved_egroupslen, saved_egroups) < 0)
82 fatal("getgroups: %.100s", strerror(errno));
83 } else { /* saved_egroupslen == 0 */
972fc531 84 if (saved_egroups != NULL)
13dff404 85 xfree(saved_egroups);
86 }
f8252c48 87
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));
13dff404 93
94 user_groupslen = getgroups(0, NULL);
f8252c48 95 if (user_groupslen < 0)
96 fatal("getgroups: %.100s", strerror(errno));
13dff404 97 if (user_groupslen > 0) {
98 user_groups = xrealloc(user_groups,
c5d10563 99 user_groupslen, sizeof(gid_t));
13dff404 100 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 }
f8252c48 106 }
107 /* Set the effective uid to the given (unprivileged) uid. */
d98d029a 108 if (setgroups(user_groupslen, user_groups) < 0)
63bd8c36 109 fatal("setgroups: %.100s", strerror(errno));
0096ac62 110#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 */
d98d029a 118 if (setegid(pw->pw_gid) < 0)
caa49784 119 fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
f8252c48 120 strerror(errno));
121 if (seteuid(pw->pw_uid) == -1)
caa49784 122 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
f8252c48 123 strerror(errno));
8efc0c15 124}
f8252c48 125
3c33c1b6 126void
127permanently_drop_suid(uid_t uid)
128{
129 uid_t old_uid = getuid();
130
131 debug("permanently_drop_suid: %u", (u_int)uid);
132#if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
133 if (setresuid(uid, uid, uid) < 0)
134 fatal("setresuid %u: %.100s", (u_int)uid, strerror(errno));
135#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
136 if (setreuid(uid, uid) < 0)
137 fatal("setreuid %u: %.100s", (u_int)uid, strerror(errno));
138#else
139# ifndef SETEUID_BREAKS_SETUID
140 if (seteuid(uid) < 0)
141 fatal("seteuid %u: %.100s", (u_int)uid, strerror(errno));
142# endif
143 if (setuid(uid) < 0)
144 fatal("setuid %u: %.100s", (u_int)uid, strerror(errno));
145#endif
146
147#ifndef HAVE_CYGWIN
148 /* Try restoration of UID if changed (test clearing of saved uid) */
149 if (old_uid != uid &&
150 (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
151 fatal("%s: was able to restore old [e]uid", __func__);
152#endif
153
154 /* Verify UID drop was successful */
155 if (getuid() != uid || geteuid() != uid) {
156 fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
157 __func__, (u_int)getuid(), (u_int)geteuid(), (u_int)uid);
158 }
159}
160
5260325f 161/*
a3626e12 162 * Restores to the original (privileged) uid.
5260325f 163 */
6ae2364d 164void
1e3b8b07 165restore_uid(void)
8efc0c15 166{
63bd8c36 167 /* it's a no-op unless privileged */
0df3a240 168 if (!privileged) {
169 debug("restore_uid: (unprivileged)");
63bd8c36 170 return;
0df3a240 171 }
63bd8c36 172 if (!temporarily_use_uid_effective)
173 fatal("restore_uid: temporarily_use_uid not effective");
0096ac62 174
175#ifdef SAVED_IDS_WORK_WITH_SETEUID
13979d47 176 debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
a3626e12 177 /* Set the effective uid back to the saved privileged uid. */
5260325f 178 if (seteuid(saved_euid) < 0)
caa49784 179 fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
0096ac62 180 if (setegid(saved_egid) < 0)
caa49784 181 fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
0096ac62 182#else /* SAVED_IDS_WORK_WITH_SETEUID */
183 /*
184 * We are unable to restore the real uid to its unprivileged value.
185 * Propagate the real uid (usually more privileged) to effective uid
186 * as well.
187 */
188 setuid(getuid());
189 setgid(getgid());
190#endif /* SAVED_IDS_WORK_WITH_SETEUID */
191
d98d029a 192 if (setgroups(saved_egroupslen, saved_egroups) < 0)
63bd8c36 193 fatal("setgroups: %.100s", strerror(errno));
63bd8c36 194 temporarily_use_uid_effective = 0;
8efc0c15 195}
196
5260325f 197/*
198 * Permanently sets all uids to the given uid. This cannot be
199 * called while temporarily_use_uid is effective.
200 */
6ae2364d 201void
63bd8c36 202permanently_set_uid(struct passwd *pw)
8efc0c15 203{
688eed4a 204 uid_t old_uid = getuid();
205 gid_t old_gid = getgid();
206
82aeee5d 207 if (pw == NULL)
208 fatal("permanently_set_uid: no user given");
63bd8c36 209 if (temporarily_use_uid_effective)
95f20fe8 210 fatal("permanently_set_uid: temporarily_use_uid effective");
0df3a240 211 debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
212 (u_int)pw->pw_gid);
688eed4a 213
9a3fe0e2 214#if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID)
688eed4a 215 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0)
216 fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
3b8dff69 217#elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
688eed4a 218 if (setregid(pw->pw_gid, pw->pw_gid) < 0)
219 fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
220#else
fa5120a0 221 if (setegid(pw->pw_gid) < 0)
222 fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
63bd8c36 223 if (setgid(pw->pw_gid) < 0)
caa49784 224 fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
688eed4a 225#endif
226
9a3fe0e2 227#if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
688eed4a 228 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0)
229 fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
3b8dff69 230#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
f5db6a03 231 if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
232 fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a 233#else
234# ifndef SETEUID_BREAKS_SETUID
fa5120a0 235 if (seteuid(pw->pw_uid) < 0)
236 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a 237# endif
a3626e12 238 if (setuid(pw->pw_uid) < 0)
caa49784 239 fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a 240#endif
241
8f817407 242#ifndef HAVE_CYGWIN
688eed4a 243 /* Try restoration of GID if changed (test clearing of saved gid) */
8f817407 244 if (old_gid != pw->pw_gid && pw->pw_uid != 0 &&
688eed4a 245 (setgid(old_gid) != -1 || setegid(old_gid) != -1))
f5db6a03 246 fatal("%s: was able to restore old [e]gid", __func__);
8f817407 247#endif
688eed4a 248
249 /* Verify GID drop was successful */
250 if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) {
aff51935 251 fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
252 __func__, (u_int)getgid(), (u_int)getegid(),
688eed4a 253 (u_int)pw->pw_gid);
254 }
255
51e7d820 256#ifndef HAVE_CYGWIN
688eed4a 257 /* Try restoration of UID if changed (test clearing of saved uid) */
aff51935 258 if (old_uid != pw->pw_uid &&
688eed4a 259 (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
f5db6a03 260 fatal("%s: was able to restore old [e]uid", __func__);
51e7d820 261#endif
688eed4a 262
263 /* Verify UID drop was successful */
264 if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) {
aff51935 265 fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
266 __func__, (u_int)getuid(), (u_int)geteuid(),
688eed4a 267 (u_int)pw->pw_uid);
268 }
8efc0c15 269}
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