blob: 3b264cf9e866bb75331ae30eeba5d8c16e86764a [file] [log] [blame]
Damien Millerd4a8b7e1999-10-27 13:42:43 +10001/*
Damien Miller95def091999-11-25 00:26:21 +11002 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 * All rights reserved
Damien Miller95def091999-11-25 00:26:21 +11005 * Code for uid-swapping.
Damien Millere4340be2000-09-16 13:29:08 +11006 *
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".
Damien Miller95def091999-11-25 00:26:21 +110012 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100013
14#include "includes.h"
Ben Lindstromee2786a2001-04-22 17:08:00 +000015RCSID("$OpenBSD: uidswap.c,v 1.16 2001/04/20 16:32:22 markus Exp $");
Damien Millerd4a8b7e1999-10-27 13:42:43 +100016
Ben Lindstrom226cfa02001-01-22 05:34:40 +000017#include "log.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100018#include "uidswap.h"
19
Damien Miller95def091999-11-25 00:26:21 +110020/*
21 * Note: all these functions must work in all of the following cases:
22 * 1. euid=0, ruid=0
23 * 2. euid=0, ruid!=0
24 * 3. euid!=0, ruid!=0
25 * Additionally, they must work regardless of whether the system has
26 * POSIX saved uids or not.
27 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100028
Ben Lindstrom4468b262001-04-26 23:03:37 +000029#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
Damien Millerd4a8b7e1999-10-27 13:42:43 +100030/* Lets assume that posix saved ids also work with seteuid, even though that
31 is not part of the posix specification. */
Ben Lindstrom4468b262001-04-26 23:03:37 +000032#define SAVED_IDS_WORK_WITH_SETEUID
33/* Saved effective uid. */
34static uid_t saved_euid = 0;
35static gid_t saved_egid = 0;
36#endif
Ben Lindstrom768f9752001-04-25 06:27:11 +000037
Damien Millerd4a8b7e1999-10-27 13:42:43 +100038/* Saved effective uid. */
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +000039static int privileged = 0;
40static int temporarily_use_uid_effective = 0;
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +000041static gid_t saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX];
42static int saved_egroupslen = -1, user_groupslen = -1;
Ben Lindstrom768f9752001-04-25 06:27:11 +000043
Damien Miller95def091999-11-25 00:26:21 +110044/*
45 * Temporarily changes to the given uid. If the effective user
46 * id is not root, this does nothing. This call cannot be nested.
47 */
Damien Miller4af51302000-04-16 11:18:38 +100048void
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +000049temporarily_use_uid(struct passwd *pw)
Damien Millerd4a8b7e1999-10-27 13:42:43 +100050{
Ben Lindstrom768f9752001-04-25 06:27:11 +000051 /* Save the current euid, and egroups. */
Ben Lindstrom4468b262001-04-26 23:03:37 +000052#ifdef SAVED_IDS_WORK_WITH_SETEUID
Ben Lindstrom768f9752001-04-25 06:27:11 +000053 saved_euid = geteuid();
Ben Lindstrom4468b262001-04-26 23:03:37 +000054 saved_egid = getegid();
Ben Lindstrom768f9752001-04-25 06:27:11 +000055 debug("temporarily_use_uid: %d/%d (e=%d)",
56 pw->pw_uid, pw->pw_gid, saved_euid);
57 if (saved_euid != 0) {
58 privileged = 0;
59 return;
60 }
Ben Lindstrom4468b262001-04-26 23:03:37 +000061#else
62 if (geteuid() != 0) {
63 privileged = 0;
64 return;
65 }
66#endif /* SAVED_IDS_WORK_WITH_SETEUID */
67
Ben Lindstrom768f9752001-04-25 06:27:11 +000068 privileged = 1;
69 temporarily_use_uid_effective = 1;
Ben Lindstrom768f9752001-04-25 06:27:11 +000070 saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
71 if (saved_egroupslen < 0)
72 fatal("getgroups: %.100s", strerror(errno));
73
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,
78 strerror(errno));
79 user_groupslen = getgroups(NGROUPS_MAX, user_groups);
80 if (user_groupslen < 0)
81 fatal("getgroups: %.100s", strerror(errno));
82 }
Ben Lindstrom0f853482001-04-27 02:10:15 +000083#ifndef HAVE_CYGWIN
Ben Lindstrom768f9752001-04-25 06:27:11 +000084 /* Set the effective uid to the given (unprivileged) uid. */
Ben Lindstromf52373f2001-04-08 18:38:04 +000085 if (setgroups(user_groupslen, user_groups) < 0)
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +000086 fatal("setgroups: %.100s", strerror(errno));
Ben Lindstrom0f853482001-04-27 02:10:15 +000087#endif /* !HAVE_CYWIN */
Ben Lindstrom4468b262001-04-26 23:03:37 +000088#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 */
Ben Lindstromf52373f2001-04-08 18:38:04 +000096 if (setegid(pw->pw_gid) < 0)
Ben Lindstrom768f9752001-04-25 06:27:11 +000097 fatal("setegid %u: %.100s", (u_int) pw->pw_gid,
98 strerror(errno));
99 if (seteuid(pw->pw_uid) == -1)
100 fatal("seteuid %u: %.100s", (u_int) pw->pw_uid,
101 strerror(errno));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000102}
Ben Lindstrom768f9752001-04-25 06:27:11 +0000103
Damien Miller95def091999-11-25 00:26:21 +1100104/*
Ben Lindstromee2786a2001-04-22 17:08:00 +0000105 * Restores to the original (privileged) uid.
Damien Miller95def091999-11-25 00:26:21 +1100106 */
Damien Miller4af51302000-04-16 11:18:38 +1000107void
Ben Lindstrom46c16222000-12-22 01:43:59 +0000108restore_uid(void)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000109{
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000110 debug("restore_uid");
111 /* it's a no-op unless privileged */
112 if (!privileged)
113 return;
114 if (!temporarily_use_uid_effective)
115 fatal("restore_uid: temporarily_use_uid not effective");
Ben Lindstrom4468b262001-04-26 23:03:37 +0000116
117#ifdef SAVED_IDS_WORK_WITH_SETEUID
Ben Lindstromee2786a2001-04-22 17:08:00 +0000118 /* Set the effective uid back to the saved privileged uid. */
Damien Miller95def091999-11-25 00:26:21 +1100119 if (seteuid(saved_euid) < 0)
Ben Lindstrom4468b262001-04-26 23:03:37 +0000120 fatal("seteuid %u: %.100s", (u_int) saved_euid,
121 strerror(errno));
122 if (setegid(saved_egid) < 0)
123 fatal("setegid %u: %.100s", (u_int) saved_egid,
124 strerror(errno));
125#else /* SAVED_IDS_WORK_WITH_SETEUID */
126 /*
127 * We are unable to restore the real uid to its unprivileged value.
128 * Propagate the real uid (usually more privileged) to effective uid
129 * as well.
130 */
131 setuid(getuid());
132 setgid(getgid());
133#endif /* SAVED_IDS_WORK_WITH_SETEUID */
134
Ben Lindstrom0f853482001-04-27 02:10:15 +0000135#ifndef HAVE_CYGWIN
Ben Lindstromf52373f2001-04-08 18:38:04 +0000136 if (setgroups(saved_egroupslen, saved_egroups) < 0)
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000137 fatal("setgroups: %.100s", strerror(errno));
Ben Lindstrom0f853482001-04-27 02:10:15 +0000138#endif /* !HAVE_CYGWIN */
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000139 temporarily_use_uid_effective = 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000140}
141
Damien Miller95def091999-11-25 00:26:21 +1100142/*
143 * Permanently sets all uids to the given uid. This cannot be
144 * called while temporarily_use_uid is effective.
145 */
Damien Miller4af51302000-04-16 11:18:38 +1000146void
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000147permanently_set_uid(struct passwd *pw)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000148{
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000149 if (temporarily_use_uid_effective)
150 fatal("restore_uid: temporarily_use_uid effective");
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000151 if (setgid(pw->pw_gid) < 0)
152 fatal("setgid %u: %.100s", (u_int) pw->pw_gid, strerror(errno));
Ben Lindstromee2786a2001-04-22 17:08:00 +0000153 if (setuid(pw->pw_uid) < 0)
154 fatal("setuid %u: %.100s", (u_int) pw->pw_uid, strerror(errno));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000155}