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 1.18 2001/08/08 21:34:19 markus 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: %d/%d (e=%d)",
56 pw->pw_uid, pw->pw_gid, 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));
84 /* Set the effective uid to the given (unprivileged) uid. */
85 if (setgroups(user_groupslen, user_groups) < 0)
86 fatal("setgroups: %.100s", strerror(errno));
87 #endif /* !HAVE_CYWIN */
88 #ifndef SAVED_IDS_WORK_WITH_SETEUID
89 /* Propagate the privileged gid to all of our gids. */
90 if (setgid(getegid()) < 0)
91 debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
92 /* Propagate the privileged uid to all of our uids. */
93 if (setuid(geteuid()) < 0)
94 debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
95 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
96 if (setegid(pw->pw_gid) < 0)
97 fatal("setegid %u: %.100s", (u_int) pw->pw_gid,
99 if (seteuid(pw->pw_uid) == -1)
100 fatal("seteuid %u: %.100s", (u_int) pw->pw_uid,
105 * Restores to the original (privileged) uid.
110 debug("restore_uid");
111 /* it's a no-op unless privileged */
114 if (!temporarily_use_uid_effective)
115 fatal("restore_uid: temporarily_use_uid not effective");
117 #ifdef SAVED_IDS_WORK_WITH_SETEUID
118 /* Set the effective uid back to the saved privileged uid. */
119 if (seteuid(saved_euid) < 0)
120 fatal("seteuid %u: %.100s", (u_int) saved_euid, strerror(errno));
121 if (setegid(saved_egid) < 0)
122 fatal("setegid %u: %.100s", (u_int) saved_egid,
124 #else /* SAVED_IDS_WORK_WITH_SETEUID */
126 * We are unable to restore the real uid to its unprivileged value.
127 * Propagate the real uid (usually more privileged) to effective uid
132 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
135 if (setgroups(saved_egroupslen, saved_egroups) < 0)
136 fatal("setgroups: %.100s", strerror(errno));
137 #endif /* !HAVE_CYGWIN */
138 temporarily_use_uid_effective = 0;
142 * Permanently sets all uids to the given uid. This cannot be
143 * called while temporarily_use_uid is effective.
146 permanently_set_uid(struct passwd *pw)
148 if (temporarily_use_uid_effective)
149 fatal("restore_uid: temporarily_use_uid effective");
150 if (setgid(pw->pw_gid) < 0)
151 fatal("setgid %u: %.100s", (u_int) pw->pw_gid, strerror(errno));
152 if (setuid(pw->pw_uid) < 0)
153 fatal("setuid %u: %.100s", (u_int) pw->pw_uid, strerror(errno));