blob: 0a772c7b33a8388063cd6c324b556459720b7069 [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 Lindstrom10d99362002-06-06 20:44:06 +000015RCSID("$OpenBSD: uidswap.c,v 1.22 2002/05/28 21:24:00 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 Lindstromabff1dd2002-06-06 20:38:49 +000055 debug("temporarily_use_uid: %u/%u (e=%u)",
56 (u_int)pw->pw_uid, (u_int)pw->pw_gid, (u_int)saved_euid);
Ben Lindstrom768f9752001-04-25 06:27:11 +000057 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;
Damien Miller9f0f5c62001-12-21 14:45:46 +110070 saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
Ben Lindstrom768f9752001-04-25 06:27:11 +000071 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));
Damien Miller9f0f5c62001-12-21 14:45:46 +110079 user_groupslen = getgroups(NGROUPS_MAX, user_groups);
Ben Lindstrom768f9752001-04-25 06:27:11 +000080 if (user_groupslen < 0)
81 fatal("getgroups: %.100s", strerror(errno));
82 }
83 /* Set the effective uid to the given (unprivileged) uid. */
Ben Lindstromf52373f2001-04-08 18:38:04 +000084 if (setgroups(user_groupslen, user_groups) < 0)
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +000085 fatal("setgroups: %.100s", strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +000086#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 */
Ben Lindstromf52373f2001-04-08 18:38:04 +000094 if (setegid(pw->pw_gid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +000095 fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
Ben Lindstrom768f9752001-04-25 06:27:11 +000096 strerror(errno));
97 if (seteuid(pw->pw_uid) == -1)
Ben Lindstromabff1dd2002-06-06 20:38:49 +000098 fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
Ben Lindstrom768f9752001-04-25 06:27:11 +000099 strerror(errno));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000100}
Ben Lindstrom768f9752001-04-25 06:27:11 +0000101
Damien Miller95def091999-11-25 00:26:21 +1100102/*
Ben Lindstromee2786a2001-04-22 17:08:00 +0000103 * Restores to the original (privileged) uid.
Damien Miller95def091999-11-25 00:26:21 +1100104 */
Damien Miller4af51302000-04-16 11:18:38 +1000105void
Ben Lindstrom46c16222000-12-22 01:43:59 +0000106restore_uid(void)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000107{
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000108 debug("restore_uid");
109 /* it's a no-op unless privileged */
110 if (!privileged)
111 return;
112 if (!temporarily_use_uid_effective)
113 fatal("restore_uid: temporarily_use_uid not effective");
Ben Lindstrom4468b262001-04-26 23:03:37 +0000114
115#ifdef SAVED_IDS_WORK_WITH_SETEUID
Ben Lindstromee2786a2001-04-22 17:08:00 +0000116 /* Set the effective uid back to the saved privileged uid. */
Damien Miller95def091999-11-25 00:26:21 +1100117 if (seteuid(saved_euid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000118 fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000119 if (setegid(saved_egid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000120 fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
Ben Lindstrom4468b262001-04-26 23:03:37 +0000121#else /* SAVED_IDS_WORK_WITH_SETEUID */
122 /*
123 * We are unable to restore the real uid to its unprivileged value.
124 * Propagate the real uid (usually more privileged) to effective uid
125 * as well.
126 */
127 setuid(getuid());
128 setgid(getgid());
129#endif /* SAVED_IDS_WORK_WITH_SETEUID */
130
Ben Lindstromf52373f2001-04-08 18:38:04 +0000131 if (setgroups(saved_egroupslen, saved_egroups) < 0)
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000132 fatal("setgroups: %.100s", strerror(errno));
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000133 temporarily_use_uid_effective = 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000134}
135
Damien Miller95def091999-11-25 00:26:21 +1100136/*
137 * Permanently sets all uids to the given uid. This cannot be
138 * called while temporarily_use_uid is effective.
139 */
Damien Miller4af51302000-04-16 11:18:38 +1000140void
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000141permanently_set_uid(struct passwd *pw)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000142{
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000143 if (temporarily_use_uid_effective)
Ben Lindstromca8943e2002-06-06 20:42:04 +0000144 fatal("permanently_set_uid: temporarily_use_uid effective");
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000145 if (setgid(pw->pw_gid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000146 fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
Ben Lindstromee2786a2001-04-22 17:08:00 +0000147 if (setuid(pw->pw_uid) < 0)
Ben Lindstromabff1dd2002-06-06 20:38:49 +0000148 fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000149}