Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 1 | /* |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> |
| 3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| 4 | * All rights reserved |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 5 | * Code for uid-swapping. |
Damien Miller | e4340be | 2000-09-16 13:29:08 +1100 | [diff] [blame] | 6 | * |
| 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 Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 12 | */ |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 13 | |
| 14 | #include "includes.h" |
Ben Lindstrom | f52373f | 2001-04-08 18:38:04 +0000 | [diff] [blame] | 15 | RCSID("$OpenBSD: uidswap.c,v 1.15 2001/04/08 11:24:33 markus Exp $"); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 16 | |
Ben Lindstrom | 226cfa0 | 2001-01-22 05:34:40 +0000 | [diff] [blame] | 17 | #include "log.h" |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 18 | #include "uidswap.h" |
| 19 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 20 | /* |
| 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 Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 28 | |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 29 | /* Lets assume that posix saved ids also work with seteuid, even though that |
| 30 | is not part of the posix specification. */ |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 31 | |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 32 | /* Saved effective uid. */ |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 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; |
| 39 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 40 | /* |
| 41 | * Temporarily changes to the given uid. If the effective user |
| 42 | * id is not root, this does nothing. This call cannot be nested. |
| 43 | */ |
Damien Miller | 4af5130 | 2000-04-16 11:18:38 +1000 | [diff] [blame] | 44 | void |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 45 | temporarily_use_uid(struct passwd *pw) |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 46 | { |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 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) { |
| 52 | privileged = 0; |
| 53 | return; |
| 54 | } |
| 55 | privileged = 1; |
| 56 | temporarily_use_uid_effective = 1; |
Ben Lindstrom | f52373f | 2001-04-08 18:38:04 +0000 | [diff] [blame] | 57 | saved_egid = getegid(); |
| 58 | saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups); |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 59 | if (saved_egroupslen < 0) |
| 60 | fatal("getgroups: %.100s", strerror(errno)); |
| 61 | |
| 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, |
| 66 | strerror(errno)); |
| 67 | user_groupslen = getgroups(NGROUPS_MAX, user_groups); |
| 68 | if (user_groupslen < 0) |
| 69 | fatal("getgroups: %.100s", strerror(errno)); |
| 70 | } |
| 71 | /* Set the effective uid to the given (unprivileged) uid. */ |
Ben Lindstrom | f52373f | 2001-04-08 18:38:04 +0000 | [diff] [blame] | 72 | if (setgroups(user_groupslen, user_groups) < 0) |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 73 | fatal("setgroups: %.100s", strerror(errno)); |
Ben Lindstrom | f52373f | 2001-04-08 18:38:04 +0000 | [diff] [blame] | 74 | pw->pw_gid = pw->pw_gid; |
| 75 | if (setegid(pw->pw_gid) < 0) |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 76 | fatal("setegid %u: %.100s", (u_int) pw->pw_gid, |
| 77 | strerror(errno)); |
| 78 | if (seteuid(pw->pw_uid) == -1) |
| 79 | fatal("seteuid %u: %.100s", (u_int) pw->pw_uid, |
| 80 | strerror(errno)); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 81 | } |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 82 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 83 | /* |
| 84 | * Restores to the original uid. |
| 85 | */ |
Damien Miller | 4af5130 | 2000-04-16 11:18:38 +1000 | [diff] [blame] | 86 | void |
Ben Lindstrom | 46c1622 | 2000-12-22 01:43:59 +0000 | [diff] [blame] | 87 | restore_uid(void) |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 88 | { |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 89 | debug("restore_uid"); |
| 90 | /* it's a no-op unless privileged */ |
| 91 | if (!privileged) |
| 92 | return; |
| 93 | if (!temporarily_use_uid_effective) |
| 94 | fatal("restore_uid: temporarily_use_uid not effective"); |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 95 | /* Set the effective uid back to the saved uid. */ |
| 96 | if (seteuid(saved_euid) < 0) |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 97 | fatal("seteuid %u: %.100s", (u_int) saved_euid, strerror(errno)); |
Ben Lindstrom | f52373f | 2001-04-08 18:38:04 +0000 | [diff] [blame] | 98 | if (setgroups(saved_egroupslen, saved_egroups) < 0) |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 99 | fatal("setgroups: %.100s", strerror(errno)); |
Ben Lindstrom | f52373f | 2001-04-08 18:38:04 +0000 | [diff] [blame] | 100 | if (setegid(saved_egid) < 0) |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 101 | fatal("setegid %u: %.100s", (u_int) saved_egid, strerror(errno)); |
| 102 | temporarily_use_uid_effective = 0; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 103 | } |
| 104 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 105 | /* |
| 106 | * Permanently sets all uids to the given uid. This cannot be |
| 107 | * called while temporarily_use_uid is effective. |
| 108 | */ |
Damien Miller | 4af5130 | 2000-04-16 11:18:38 +1000 | [diff] [blame] | 109 | void |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 110 | permanently_set_uid(struct passwd *pw) |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 111 | { |
Ben Lindstrom | 3fcf1a2 | 2001-04-08 18:26:59 +0000 | [diff] [blame] | 112 | if (temporarily_use_uid_effective) |
| 113 | fatal("restore_uid: temporarily_use_uid effective"); |
| 114 | if (setuid(pw->pw_uid) < 0) |
| 115 | fatal("setuid %u: %.100s", (u_int) pw->pw_uid, strerror(errno)); |
| 116 | if (setgid(pw->pw_gid) < 0) |
| 117 | fatal("setgid %u: %.100s", (u_int) pw->pw_gid, strerror(errno)); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 118 | } |