- deraadt@cvs.openbsd.org 2006/08/03 03:34:42
[openssh-git.git] / uidswap.c
blob91d878c30e1b34b308b46aa6430233e84a89192e
1 /* $OpenBSD: uidswap.c,v 1.35 2006/08/03 03:34:42 deraadt Exp $ */
2 /*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
6 * Code for uid-swapping.
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".
15 #include "includes.h"
17 #include <sys/param.h>
18 #include <errno.h>
19 #include <pwd.h>
20 #include <string.h>
21 #include <unistd.h>
22 #include <stdarg.h>
24 #include <grp.h>
26 #include "log.h"
27 #include "uidswap.h"
28 #include "xmalloc.h"
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.
39 #if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
40 /* Lets assume that posix saved ids also work with seteuid, even though that
41 is not part of the posix specification. */
42 #define SAVED_IDS_WORK_WITH_SETEUID
43 /* Saved effective uid. */
44 static uid_t saved_euid = 0;
45 static gid_t saved_egid = 0;
46 #endif
48 /* Saved effective uid. */
49 static int privileged = 0;
50 static int temporarily_use_uid_effective = 0;
51 static gid_t *saved_egroups = NULL, *user_groups = NULL;
52 static int saved_egroupslen = -1, user_groupslen = -1;
55 * Temporarily changes to the given uid. If the effective user
56 * id is not root, this does nothing. This call cannot be nested.
58 void
59 temporarily_use_uid(struct passwd *pw)
61 /* Save the current euid, and egroups. */
62 #ifdef SAVED_IDS_WORK_WITH_SETEUID
63 saved_euid = geteuid();
64 saved_egid = getegid();
65 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);
68 #ifndef HAVE_CYGWIN
69 if (saved_euid != 0) {
70 privileged = 0;
71 return;
73 #endif
74 #else
75 if (geteuid() != 0) {
76 privileged = 0;
77 return;
79 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
81 privileged = 1;
82 temporarily_use_uid_effective = 1;
84 saved_egroupslen = getgroups(0, NULL);
85 if (saved_egroupslen < 0)
86 fatal("getgroups: %.100s", strerror(errno));
87 if (saved_egroupslen > 0) {
88 saved_egroups = xrealloc(saved_egroups,
89 saved_egroupslen, sizeof(gid_t));
90 if (getgroups(saved_egroupslen, saved_egroups) < 0)
91 fatal("getgroups: %.100s", strerror(errno));
92 } else { /* saved_egroupslen == 0 */
93 if (saved_egroups != NULL)
94 xfree(saved_egroups);
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));
103 user_groupslen = getgroups(0, NULL);
104 if (user_groupslen < 0)
105 fatal("getgroups: %.100s", strerror(errno));
106 if (user_groupslen > 0) {
107 user_groups = xrealloc(user_groups,
108 user_groupslen, sizeof(gid_t));
109 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);
116 /* Set the effective uid to the given (unprivileged) uid. */
117 if (setgroups(user_groupslen, user_groups) < 0)
118 fatal("setgroups: %.100s", strerror(errno));
119 #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 */
127 if (setegid(pw->pw_gid) < 0)
128 fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
129 strerror(errno));
130 if (seteuid(pw->pw_uid) == -1)
131 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
132 strerror(errno));
135 void
136 permanently_drop_suid(uid_t uid)
138 uid_t old_uid = getuid();
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
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
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);
171 * Restores to the original (privileged) uid.
173 void
174 restore_uid(void)
176 /* it's a no-op unless privileged */
177 if (!privileged) {
178 debug("restore_uid: (unprivileged)");
179 return;
181 if (!temporarily_use_uid_effective)
182 fatal("restore_uid: temporarily_use_uid not effective");
184 #ifdef SAVED_IDS_WORK_WITH_SETEUID
185 debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
186 /* Set the effective uid back to the saved privileged uid. */
187 if (seteuid(saved_euid) < 0)
188 fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
189 if (setegid(saved_egid) < 0)
190 fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
191 #else /* SAVED_IDS_WORK_WITH_SETEUID */
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.
197 setuid(getuid());
198 setgid(getgid());
199 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
201 if (setgroups(saved_egroupslen, saved_egroups) < 0)
202 fatal("setgroups: %.100s", strerror(errno));
203 temporarily_use_uid_effective = 0;
207 * Permanently sets all uids to the given uid. This cannot be
208 * called while temporarily_use_uid is effective.
210 void
211 permanently_set_uid(struct passwd *pw)
213 uid_t old_uid = getuid();
214 gid_t old_gid = getgid();
216 if (pw == NULL)
217 fatal("permanently_set_uid: no user given");
218 if (temporarily_use_uid_effective)
219 fatal("permanently_set_uid: temporarily_use_uid effective");
220 debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
221 (u_int)pw->pw_gid);
223 #if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID)
224 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0)
225 fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
226 #elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
227 if (setregid(pw->pw_gid, pw->pw_gid) < 0)
228 fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
229 #else
230 if (setegid(pw->pw_gid) < 0)
231 fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
232 if (setgid(pw->pw_gid) < 0)
233 fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
234 #endif
236 #if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
237 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0)
238 fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
239 #elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
240 if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
241 fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
242 #else
243 # ifndef SETEUID_BREAKS_SETUID
244 if (seteuid(pw->pw_uid) < 0)
245 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
246 # endif
247 if (setuid(pw->pw_uid) < 0)
248 fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
249 #endif
251 #ifndef HAVE_CYGWIN
252 /* Try restoration of GID if changed (test clearing of saved gid) */
253 if (old_gid != pw->pw_gid && pw->pw_uid != 0 &&
254 (setgid(old_gid) != -1 || setegid(old_gid) != -1))
255 fatal("%s: was able to restore old [e]gid", __func__);
256 #endif
258 /* Verify GID drop was successful */
259 if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) {
260 fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
261 __func__, (u_int)getgid(), (u_int)getegid(),
262 (u_int)pw->pw_gid);
265 #ifndef HAVE_CYGWIN
266 /* Try restoration of UID if changed (test clearing of saved uid) */
267 if (old_uid != pw->pw_uid &&
268 (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
269 fatal("%s: was able to restore old [e]uid", __func__);
270 #endif
272 /* Verify UID drop was successful */
273 if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) {
274 fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
275 __func__, (u_int)getuid(), (u_int)geteuid(),
276 (u_int)pw->pw_uid);