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 1.16 2001/04/20 16:32:22 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 /* Lets assume that posix saved ids also work with seteuid, even though that
30 is not part of the posix specification. */
32 /* Saved effective uid. */
33 static int privileged = 0;
34 static int temporarily_use_uid_effective = 0;
35 static uid_t saved_euid = 0;
36 static gid_t saved_egid;
37 static gid_t saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX];
38 static int saved_egroupslen = -1, user_groupslen = -1;
41 * Temporarily changes to the given uid. If the effective user
42 * id is not root, this does nothing. This call cannot be nested.
45 temporarily_use_uid(struct passwd *pw)
47 /* Save the current euid, and egroups. */
48 saved_euid = geteuid();
49 debug("temporarily_use_uid: %d/%d (e=%d)",
50 pw->pw_uid, pw->pw_gid, saved_euid);
51 if (saved_euid != 0) {
56 temporarily_use_uid_effective = 1;
57 saved_egid = getegid();
58 saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
59 if (saved_egroupslen < 0)
60 fatal("getgroups: %.100s", strerror(errno));
62 /* set and save the user's groups */
63 if (user_groupslen == -1) {
64 if (initgroups(pw->pw_name, pw->pw_gid) < 0)
65 fatal("initgroups: %s: %.100s", pw->pw_name,
67 user_groupslen = getgroups(NGROUPS_MAX, user_groups);
68 if (user_groupslen < 0)
69 fatal("getgroups: %.100s", strerror(errno));
71 /* Set the effective uid to the given (unprivileged) uid. */
72 if (setgroups(user_groupslen, user_groups) < 0)
73 fatal("setgroups: %.100s", strerror(errno));
74 pw->pw_gid = pw->pw_gid;
75 if (setegid(pw->pw_gid) < 0)
76 fatal("setegid %u: %.100s", (u_int) pw->pw_gid,
78 if (seteuid(pw->pw_uid) == -1)
79 fatal("seteuid %u: %.100s", (u_int) pw->pw_uid,
84 * Restores to the original (privileged) uid.
90 /* it's a no-op unless privileged */
93 if (!temporarily_use_uid_effective)
94 fatal("restore_uid: temporarily_use_uid not effective");
95 /* Set the effective uid back to the saved privileged uid. */
96 if (seteuid(saved_euid) < 0)
97 fatal("seteuid %u: %.100s", (u_int) saved_euid, strerror(errno));
98 if (setgroups(saved_egroupslen, saved_egroups) < 0)
99 fatal("setgroups: %.100s", strerror(errno));
100 if (setegid(saved_egid) < 0)
101 fatal("setegid %u: %.100s", (u_int) saved_egid, strerror(errno));
102 temporarily_use_uid_effective = 0;
106 * Permanently sets all uids to the given uid. This cannot be
107 * called while temporarily_use_uid is effective.
110 permanently_set_uid(struct passwd *pw)
112 if (temporarily_use_uid_effective)
113 fatal("restore_uid: temporarily_use_uid effective");
114 if (setgid(pw->pw_gid) < 0)
115 fatal("setgid %u: %.100s", (u_int) pw->pw_gid, strerror(errno));
116 if (setuid(pw->pw_uid) < 0)
117 fatal("setuid %u: %.100s", (u_int) pw->pw_uid, strerror(errno));