2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * Code for uid-swapping.
7 * As far as I am concerned, the code I have written for this software
8 * can be used freely for any purpose. Any derived versions of this
9 * software must be clearly marked as such, and if the derived work is
10 * incompatible with the protocol description in the RFC file, it must be
11 * called by a name other than "ssh" or "Secure Shell".
15 RCSID("$OpenBSD: uidswap.c,v 1.22 2002/05/28 21:24:00 stevesk Exp $");
21 * Note: all these functions must work in all of the following cases:
25 * Additionally, they must work regardless of whether the system has
26 * POSIX saved uids or not.
29 #if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
30 /* Lets assume that posix saved ids also work with seteuid, even though that
31 is not part of the posix specification. */
32 #define SAVED_IDS_WORK_WITH_SETEUID
33 /* Saved effective uid. */
34 static uid_t saved_euid = 0;
35 static gid_t saved_egid = 0;
38 /* Saved effective uid. */
39 static int privileged = 0;
40 static int temporarily_use_uid_effective = 0;
41 static gid_t saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX];
42 static int saved_egroupslen = -1, user_groupslen = -1;
45 * Temporarily changes to the given uid. If the effective user
46 * id is not root, this does nothing. This call cannot be nested.
49 temporarily_use_uid(struct passwd *pw)
51 /* Save the current euid, and egroups. */
52 #ifdef SAVED_IDS_WORK_WITH_SETEUID
53 saved_euid = geteuid();
54 saved_egid = getegid();
55 debug("temporarily_use_uid: %u/%u (e=%u)",
56 (u_int)pw->pw_uid, (u_int)pw->pw_gid, (u_int)saved_euid);
57 if (saved_euid != 0) {
66 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
69 temporarily_use_uid_effective = 1;
70 saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
71 if (saved_egroupslen < 0)
72 fatal("getgroups: %.100s", strerror(errno));
74 /* set and save the user's groups */
75 if (user_groupslen == -1) {
76 if (initgroups(pw->pw_name, pw->pw_gid) < 0)
77 fatal("initgroups: %s: %.100s", pw->pw_name,
79 user_groupslen = getgroups(NGROUPS_MAX, user_groups);
80 if (user_groupslen < 0)
81 fatal("getgroups: %.100s", strerror(errno));
83 /* Set the effective uid to the given (unprivileged) uid. */
84 if (setgroups(user_groupslen, user_groups) < 0)
85 fatal("setgroups: %.100s", strerror(errno));
86 #ifndef SAVED_IDS_WORK_WITH_SETEUID
87 /* Propagate the privileged gid to all of our gids. */
88 if (setgid(getegid()) < 0)
89 debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
90 /* Propagate the privileged uid to all of our uids. */
91 if (setuid(geteuid()) < 0)
92 debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
93 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
94 if (setegid(pw->pw_gid) < 0)
95 fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
97 if (seteuid(pw->pw_uid) == -1)
98 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
103 * Restores to the original (privileged) uid.
108 debug("restore_uid");
109 /* it's a no-op unless privileged */
112 if (!temporarily_use_uid_effective)
113 fatal("restore_uid: temporarily_use_uid not effective");
115 #ifdef SAVED_IDS_WORK_WITH_SETEUID
116 /* Set the effective uid back to the saved privileged uid. */
117 if (seteuid(saved_euid) < 0)
118 fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
119 if (setegid(saved_egid) < 0)
120 fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
121 #else /* SAVED_IDS_WORK_WITH_SETEUID */
123 * We are unable to restore the real uid to its unprivileged value.
124 * Propagate the real uid (usually more privileged) to effective uid
129 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
131 if (setgroups(saved_egroupslen, saved_egroups) < 0)
132 fatal("setgroups: %.100s", strerror(errno));
133 temporarily_use_uid_effective = 0;
137 * Permanently sets all uids to the given uid. This cannot be
138 * called while temporarily_use_uid is effective.
141 permanently_set_uid(struct passwd *pw)
143 if (temporarily_use_uid_effective)
144 fatal("permanently_set_uid: temporarily_use_uid effective");
145 if (setgid(pw->pw_gid) < 0)
146 fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
147 if (setuid(pw->pw_uid) < 0)
148 fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));