1 /* $OpenBSD: uidswap.c,v 1.29 2006/06/08 14:45:49 markus Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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".
22 * Note: all these functions must work in all of the following cases:
26 * Additionally, they must work regardless of whether the system has
27 * POSIX saved uids or not.
30 #if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
31 /* Lets assume that posix saved ids also work with seteuid, even though that
32 is not part of the posix specification. */
33 #define SAVED_IDS_WORK_WITH_SETEUID
34 /* Saved effective uid. */
35 static uid_t saved_euid = 0;
36 static gid_t saved_egid = 0;
39 /* Saved effective uid. */
40 static int privileged = 0;
41 static int temporarily_use_uid_effective = 0;
42 static gid_t *saved_egroups = NULL, *user_groups = NULL;
43 static int saved_egroupslen = -1, user_groupslen = -1;
46 * Temporarily changes to the given uid. If the effective user
47 * id is not root, this does nothing. This call cannot be nested.
50 temporarily_use_uid(struct passwd *pw)
52 /* Save the current euid, and egroups. */
53 #ifdef SAVED_IDS_WORK_WITH_SETEUID
54 saved_euid = geteuid();
55 saved_egid = getegid();
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);
60 if (saved_euid != 0) {
70 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
73 temporarily_use_uid_effective = 1;
75 saved_egroupslen = getgroups(0, NULL);
76 if (saved_egroupslen < 0)
77 fatal("getgroups: %.100s", strerror(errno));
78 if (saved_egroupslen > 0) {
79 saved_egroups = xrealloc(saved_egroups,
80 saved_egroupslen, sizeof(gid_t));
81 if (getgroups(saved_egroupslen, saved_egroups) < 0)
82 fatal("getgroups: %.100s", strerror(errno));
83 } else { /* saved_egroupslen == 0 */
84 if (saved_egroups != NULL)
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,
94 user_groupslen = getgroups(0, NULL);
95 if (user_groupslen < 0)
96 fatal("getgroups: %.100s", strerror(errno));
97 if (user_groupslen > 0) {
98 user_groups = xrealloc(user_groups,
99 user_groupslen, sizeof(gid_t));
100 if (getgroups(user_groupslen, user_groups) < 0)
101 fatal("getgroups: %.100s", strerror(errno));
102 } else { /* user_groupslen == 0 */
107 /* Set the effective uid to the given (unprivileged) uid. */
108 if (setgroups(user_groupslen, user_groups) < 0)
109 fatal("setgroups: %.100s", strerror(errno));
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 */
118 if (setegid(pw->pw_gid) < 0)
119 fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
121 if (seteuid(pw->pw_uid) == -1)
122 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
127 permanently_drop_suid(uid_t uid)
129 uid_t old_uid = getuid();
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));
139 # ifndef SETEUID_BREAKS_SETUID
140 if (seteuid(uid) < 0)
141 fatal("seteuid %u: %.100s", (u_int)uid, strerror(errno));
144 fatal("setuid %u: %.100s", (u_int)uid, strerror(errno));
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__);
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);
162 * Restores to the original (privileged) uid.
167 /* it's a no-op unless privileged */
169 debug("restore_uid: (unprivileged)");
172 if (!temporarily_use_uid_effective)
173 fatal("restore_uid: temporarily_use_uid not effective");
175 #ifdef SAVED_IDS_WORK_WITH_SETEUID
176 debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
177 /* Set the effective uid back to the saved privileged uid. */
178 if (seteuid(saved_euid) < 0)
179 fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
180 if (setegid(saved_egid) < 0)
181 fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
182 #else /* SAVED_IDS_WORK_WITH_SETEUID */
184 * We are unable to restore the real uid to its unprivileged value.
185 * Propagate the real uid (usually more privileged) to effective uid
190 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
192 if (setgroups(saved_egroupslen, saved_egroups) < 0)
193 fatal("setgroups: %.100s", strerror(errno));
194 temporarily_use_uid_effective = 0;
198 * Permanently sets all uids to the given uid. This cannot be
199 * called while temporarily_use_uid is effective.
202 permanently_set_uid(struct passwd *pw)
204 uid_t old_uid = getuid();
205 gid_t old_gid = getgid();
208 fatal("permanently_set_uid: no user given");
209 if (temporarily_use_uid_effective)
210 fatal("permanently_set_uid: temporarily_use_uid effective");
211 debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
214 #if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID)
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));
217 #elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
218 if (setregid(pw->pw_gid, pw->pw_gid) < 0)
219 fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
221 if (setegid(pw->pw_gid) < 0)
222 fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
223 if (setgid(pw->pw_gid) < 0)
224 fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
227 #if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
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));
230 #elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
231 if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
232 fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
234 # ifndef SETEUID_BREAKS_SETUID
235 if (seteuid(pw->pw_uid) < 0)
236 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
238 if (setuid(pw->pw_uid) < 0)
239 fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
243 /* Try restoration of GID if changed (test clearing of saved gid) */
244 if (old_gid != pw->pw_gid && pw->pw_uid != 0 &&
245 (setgid(old_gid) != -1 || setegid(old_gid) != -1))
246 fatal("%s: was able to restore old [e]gid", __func__);
249 /* Verify GID drop was successful */
250 if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) {
251 fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
252 __func__, (u_int)getgid(), (u_int)getegid(),
257 /* Try restoration of UID if changed (test clearing of saved uid) */
258 if (old_uid != pw->pw_uid &&
259 (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
260 fatal("%s: was able to restore old [e]uid", __func__);
263 /* Verify UID drop was successful */
264 if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) {
265 fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
266 __func__, (u_int)getuid(), (u_int)geteuid(),