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8efc0c15 | 1 | /* |
5260325f | 2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
5260325f | 5 | * Code for uid-swapping. |
bcbf86ec | 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". | |
5260325f | 12 | */ |
8efc0c15 | 13 | |
14 | #include "includes.h" | |
63bd8c36 | 15 | RCSID("$OpenBSD: uidswap.c,v 1.14 2001/04/06 21:00:16 markus Exp $"); |
8efc0c15 | 16 | |
42f11eb2 | 17 | #include "log.h" |
8efc0c15 | 18 | #include "uidswap.h" |
19 | ||
5260325f | 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 | */ | |
8efc0c15 | 28 | |
8efc0c15 | 29 | /* Lets assume that posix saved ids also work with seteuid, even though that |
30 | is not part of the posix specification. */ | |
63bd8c36 | 31 | |
8efc0c15 | 32 | /* Saved effective uid. */ |
63bd8c36 | 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 | ||
5260325f | 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 | */ | |
6ae2364d | 44 | void |
63bd8c36 | 45 | temporarily_use_uid(struct passwd *pw) |
8efc0c15 | 46 | { |
63bd8c36 | 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; | |
57 | saved_egid = getegid(); | |
58 | saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups); | |
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. */ | |
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, | |
77 | strerror(errno)); | |
78 | if (seteuid(pw->pw_uid) == -1) | |
79 | fatal("seteuid %u: %.100s", (u_int) pw->pw_uid, | |
80 | strerror(errno)); | |
8efc0c15 | 81 | } |
63bd8c36 | 82 | |
5260325f | 83 | /* |
84 | * Restores to the original uid. | |
85 | */ | |
6ae2364d | 86 | void |
1e3b8b07 | 87 | restore_uid(void) |
8efc0c15 | 88 | { |
63bd8c36 | 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"); | |
5260325f | 95 | /* Set the effective uid back to the saved uid. */ |
96 | if (seteuid(saved_euid) < 0) | |
63bd8c36 | 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; | |
8efc0c15 | 103 | } |
104 | ||
5260325f | 105 | /* |
106 | * Permanently sets all uids to the given uid. This cannot be | |
107 | * called while temporarily_use_uid is effective. | |
108 | */ | |
6ae2364d | 109 | void |
63bd8c36 | 110 | permanently_set_uid(struct passwd *pw) |
8efc0c15 | 111 | { |
63bd8c36 | 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)); | |
8efc0c15 | 118 | } |