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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 Lindstrom1fa330c2002-07-23 21:29:49 +000015RCSID("$OpenBSD: uidswap.c,v 1.23 2002/07/15 17:15:31 stevesk 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 Lindstrom1fa330c2002-07-23 21:29:49 +000055 debug("temporarily_use_uid: %u/%u (e=%u/%u)",
56 (u_int)pw->pw_uid, (u_int)pw->pw_gid,
57 (u_int)saved_euid, (u_int)saved_egid);
Ben Lindstrom768f9752001-04-25 06:27:11 +000058 if (saved_euid != 0) {
59 privileged = 0;
60 return;
61 }
Ben Lindstrom4468b262001-04-26 23:03:37 +000062#else
63 if (geteuid() != 0) {
64 privileged = 0;
65 return;
66 }
67#endif /* SAVED_IDS_WORK_WITH_SETEUID */
68
Ben Lindstrom768f9752001-04-25 06:27:11 +000069 privileged = 1;
70 temporarily_use_uid_effective = 1;
Damien Miller9f0f5c62001-12-21 14:45:46 +110071 saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
Ben Lindstrom768f9752001-04-25 06:27:11 +000072 if (saved_egroupslen < 0)
73 fatal("getgroups: %.100s", strerror(errno));
74
75 /* set and save the user's groups */
76 if (user_groupslen == -1) {
77 if (initgroups(pw->pw_name, pw->pw_gid) < 0)
78 fatal("initgroups: %s: %.100s", pw->pw_name,
79 strerror(errno));
Damien Miller9f0f5c62001-12-21 14:45:46 +110080 user_groupslen = getgroups(NGROUPS_MAX, user_groups);
Ben Lindstrom768f9752001-04-25 06:27:11 +000081 if (user_groupslen < 0)
82 fatal("getgroups: %.100s", strerror(errno));
83 }
84 /* 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 Lindstrom4468b262001-04-26 23:03:37 +000087#ifndef SAVED_IDS_WORK_WITH_SETEUID
88 /* Propagate the privileged gid to all of our gids. */
89 if (setgid(getegid()) < 0)
90 debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
91 /* Propagate the privileged uid to all of our uids. */
92 if (setuid(geteuid()) < 0)
93 debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
94#endif /* SAVED_IDS_WORK_WITH_SETEUID */
Ben Lindstromf52373f2001-04-08 18:38:04 +000095 if (setegid(pw->pw_gid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +000096 fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
Ben Lindstrom768f9752001-04-25 06:27:11 +000097 strerror(errno));
98 if (seteuid(pw->pw_uid) == -1)
Ben Lindstromabff1dd2002-06-06 20:38:49 +000099 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
Ben Lindstrom768f9752001-04-25 06:27:11 +0000100 strerror(errno));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000101}
Ben Lindstrom768f9752001-04-25 06:27:11 +0000102
Damien Miller95def091999-11-25 00:26:21 +1100103/*
Ben Lindstromee2786a2001-04-22 17:08:00 +0000104 * Restores to the original (privileged) uid.
Damien Miller95def091999-11-25 00:26:21 +1100105 */
Damien Miller4af51302000-04-16 11:18:38 +1000106void
Ben Lindstrom46c16222000-12-22 01:43:59 +0000107restore_uid(void)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000108{
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000109 /* it's a no-op unless privileged */
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000110 if (!privileged) {
111 debug("restore_uid: (unprivileged)");
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000112 return;
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000113 }
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000114 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 Lindstrom18d2b5d2002-07-30 19:32:07 +0000118 debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
Ben Lindstromee2786a2001-04-22 17:08:00 +0000119 /* Set the effective uid back to the saved privileged uid. */
Damien Miller95def091999-11-25 00:26:21 +1100120 if (seteuid(saved_euid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000121 fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000122 if (setegid(saved_egid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000123 fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000124#else /* SAVED_IDS_WORK_WITH_SETEUID */
125 /*
126 * We are unable to restore the real uid to its unprivileged value.
127 * Propagate the real uid (usually more privileged) to effective uid
128 * as well.
129 */
130 setuid(getuid());
131 setgid(getgid());
132#endif /* SAVED_IDS_WORK_WITH_SETEUID */
133
Ben Lindstromf52373f2001-04-08 18:38:04 +0000134 if (setgroups(saved_egroupslen, saved_egroups) < 0)
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000135 fatal("setgroups: %.100s", strerror(errno));
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000136 temporarily_use_uid_effective = 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000137}
138
Damien Miller95def091999-11-25 00:26:21 +1100139/*
140 * Permanently sets all uids to the given uid. This cannot be
141 * called while temporarily_use_uid is effective.
142 */
Damien Miller4af51302000-04-16 11:18:38 +1000143void
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000144permanently_set_uid(struct passwd *pw)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000145{
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000146 if (temporarily_use_uid_effective)
Ben Lindstromca8943e2002-06-06 20:42:04 +0000147 fatal("permanently_set_uid: temporarily_use_uid effective");
Ben Lindstrom1fa330c2002-07-23 21:29:49 +0000148 debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
149 (u_int)pw->pw_gid);
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000150 if (setgid(pw->pw_gid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000151 fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
Ben Lindstromee2786a2001-04-22 17:08:00 +0000152 if (setuid(pw->pw_uid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000153 fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000154}