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3c0ef626 | 1 | /* |
2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
5 | * Code for uid-swapping. | |
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". | |
12 | */ | |
13 | ||
14 | #include "includes.h" | |
15 | RCSID("$OpenBSD: uidswap.c,v 1.18 2001/08/08 21:34:19 markus Exp $"); | |
16 | ||
17 | #include "log.h" | |
18 | #include "uidswap.h" | |
19 | ||
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 | */ | |
28 | ||
29 | #if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS) | |
30 | /* Lets assume that posix saved ids also work with seteuid, even though that | |
31 | is not part of the posix specification. */ | |
32 | #define SAVED_IDS_WORK_WITH_SETEUID | |
33 | /* Saved effective uid. */ | |
34 | static uid_t saved_euid = 0; | |
35 | static gid_t saved_egid = 0; | |
36 | #endif | |
37 | ||
38 | /* Saved effective uid. */ | |
39 | static int privileged = 0; | |
40 | static int temporarily_use_uid_effective = 0; | |
41 | static gid_t saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX]; | |
42 | static int saved_egroupslen = -1, user_groupslen = -1; | |
43 | ||
44 | /* | |
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 | */ | |
48 | void | |
49 | temporarily_use_uid(struct passwd *pw) | |
50 | { | |
51 | /* Save the current euid, and egroups. */ | |
52 | #ifdef SAVED_IDS_WORK_WITH_SETEUID | |
53 | saved_euid = geteuid(); | |
54 | saved_egid = getegid(); | |
55 | 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 | } | |
61 | #else | |
62 | if (geteuid() != 0) { | |
63 | privileged = 0; | |
64 | return; | |
65 | } | |
66 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ | |
67 | ||
68 | privileged = 1; | |
69 | temporarily_use_uid_effective = 1; | |
70 | 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 | } | |
83 | #ifndef HAVE_CYGWIN | |
84 | /* Set the effective uid to the given (unprivileged) uid. */ | |
85 | if (setgroups(user_groupslen, user_groups) < 0) | |
86 | fatal("setgroups: %.100s", strerror(errno)); | |
87 | #endif /* !HAVE_CYWIN */ | |
88 | #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 */ | |
96 | if (setegid(pw->pw_gid) < 0) | |
97 | 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)); | |
102 | } | |
103 | ||
104 | /* | |
105 | * Restores to the original (privileged) uid. | |
106 | */ | |
107 | void | |
108 | restore_uid(void) | |
109 | { | |
110 | 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"); | |
116 | ||
117 | #ifdef SAVED_IDS_WORK_WITH_SETEUID | |
118 | /* Set the effective uid back to the saved privileged uid. */ | |
119 | if (seteuid(saved_euid) < 0) | |
120 | fatal("seteuid %u: %.100s", (u_int) saved_euid, strerror(errno)); | |
121 | if (setegid(saved_egid) < 0) | |
122 | fatal("setegid %u: %.100s", (u_int) saved_egid, | |
123 | strerror(errno)); | |
124 | #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 | ||
134 | #ifndef HAVE_CYGWIN | |
135 | if (setgroups(saved_egroupslen, saved_egroups) < 0) | |
136 | fatal("setgroups: %.100s", strerror(errno)); | |
137 | #endif /* !HAVE_CYGWIN */ | |
138 | temporarily_use_uid_effective = 0; | |
139 | } | |
140 | ||
141 | /* | |
142 | * Permanently sets all uids to the given uid. This cannot be | |
143 | * called while temporarily_use_uid is effective. | |
144 | */ | |
145 | void | |
146 | permanently_set_uid(struct passwd *pw) | |
147 | { | |
148 | if (temporarily_use_uid_effective) | |
149 | fatal("restore_uid: temporarily_use_uid effective"); | |
150 | if (setgid(pw->pw_gid) < 0) | |
151 | fatal("setgid %u: %.100s", (u_int) pw->pw_gid, strerror(errno)); | |
152 | if (setuid(pw->pw_uid) < 0) | |
153 | fatal("setuid %u: %.100s", (u_int) pw->pw_uid, strerror(errno)); | |
154 | } |