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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" | |
0fff78ff | 15 | RCSID("$OpenBSD: uidswap.c,v 1.24 2003/05/29 16:58:45 deraadt Exp $"); |
3c0ef626 | 16 | |
17 | #include "log.h" | |
18 | #include "uidswap.h" | |
cdd66111 | 19 | #include "xmalloc.h" |
3c0ef626 | 20 | |
21 | /* | |
22 | * Note: all these functions must work in all of the following cases: | |
23 | * 1. euid=0, ruid=0 | |
24 | * 2. euid=0, ruid!=0 | |
25 | * 3. euid!=0, ruid!=0 | |
26 | * Additionally, they must work regardless of whether the system has | |
27 | * POSIX saved uids or not. | |
28 | */ | |
29 | ||
30 | #if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS) | |
31 | /* Lets assume that posix saved ids also work with seteuid, even though that | |
32 | is not part of the posix specification. */ | |
33 | #define SAVED_IDS_WORK_WITH_SETEUID | |
34 | /* Saved effective uid. */ | |
35 | static uid_t saved_euid = 0; | |
36 | static gid_t saved_egid = 0; | |
37 | #endif | |
38 | ||
39 | /* Saved effective uid. */ | |
40 | static int privileged = 0; | |
41 | static int temporarily_use_uid_effective = 0; | |
cdd66111 | 42 | static gid_t *saved_egroups = NULL, *user_groups = NULL; |
3c0ef626 | 43 | static int saved_egroupslen = -1, user_groupslen = -1; |
44 | ||
45 | /* | |
46 | * Temporarily changes to the given uid. If the effective user | |
47 | * id is not root, this does nothing. This call cannot be nested. | |
48 | */ | |
49 | void | |
50 | temporarily_use_uid(struct passwd *pw) | |
51 | { | |
52 | /* Save the current euid, and egroups. */ | |
53 | #ifdef SAVED_IDS_WORK_WITH_SETEUID | |
54 | saved_euid = geteuid(); | |
55 | saved_egid = getegid(); | |
41b2f314 | 56 | debug("temporarily_use_uid: %u/%u (e=%u/%u)", |
57 | (u_int)pw->pw_uid, (u_int)pw->pw_gid, | |
58 | (u_int)saved_euid, (u_int)saved_egid); | |
996d5e62 | 59 | #ifndef HAVE_CYGWIN |
3c0ef626 | 60 | if (saved_euid != 0) { |
61 | privileged = 0; | |
62 | return; | |
63 | } | |
996d5e62 | 64 | #endif |
3c0ef626 | 65 | #else |
66 | if (geteuid() != 0) { | |
67 | privileged = 0; | |
68 | return; | |
69 | } | |
70 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ | |
71 | ||
72 | privileged = 1; | |
73 | temporarily_use_uid_effective = 1; | |
cdd66111 | 74 | |
75 | saved_egroupslen = getgroups(0, NULL); | |
3c0ef626 | 76 | if (saved_egroupslen < 0) |
77 | fatal("getgroups: %.100s", strerror(errno)); | |
cdd66111 | 78 | if (saved_egroupslen > 0) { |
79 | saved_egroups = xrealloc(saved_egroups, | |
80 | saved_egroupslen * sizeof(gid_t)); | |
81 | if (getgroups(saved_egroupslen, saved_egroups) < 0) | |
82 | fatal("getgroups: %.100s", strerror(errno)); | |
83 | } else { /* saved_egroupslen == 0 */ | |
84 | if (saved_egroups != NULL) | |
85 | xfree(saved_egroups); | |
86 | } | |
3c0ef626 | 87 | |
88 | /* set and save the user's groups */ | |
89 | if (user_groupslen == -1) { | |
90 | if (initgroups(pw->pw_name, pw->pw_gid) < 0) | |
91 | fatal("initgroups: %s: %.100s", pw->pw_name, | |
92 | strerror(errno)); | |
cdd66111 | 93 | |
94 | user_groupslen = getgroups(0, NULL); | |
3c0ef626 | 95 | if (user_groupslen < 0) |
96 | fatal("getgroups: %.100s", strerror(errno)); | |
cdd66111 | 97 | if (user_groupslen > 0) { |
98 | user_groups = xrealloc(user_groups, | |
99 | user_groupslen * sizeof(gid_t)); | |
100 | if (getgroups(user_groupslen, user_groups) < 0) | |
101 | fatal("getgroups: %.100s", strerror(errno)); | |
102 | } else { /* user_groupslen == 0 */ | |
103 | if (user_groups) | |
104 | xfree(user_groups); | |
105 | } | |
3c0ef626 | 106 | } |
3c0ef626 | 107 | /* Set the effective uid to the given (unprivileged) uid. */ |
108 | if (setgroups(user_groupslen, user_groups) < 0) | |
109 | fatal("setgroups: %.100s", strerror(errno)); | |
3c0ef626 | 110 | #ifndef SAVED_IDS_WORK_WITH_SETEUID |
111 | /* Propagate the privileged gid to all of our gids. */ | |
112 | if (setgid(getegid()) < 0) | |
113 | debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno)); | |
114 | /* Propagate the privileged uid to all of our uids. */ | |
115 | if (setuid(geteuid()) < 0) | |
116 | debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno)); | |
117 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ | |
118 | if (setegid(pw->pw_gid) < 0) | |
f5799ae1 | 119 | fatal("setegid %u: %.100s", (u_int)pw->pw_gid, |
3c0ef626 | 120 | strerror(errno)); |
121 | if (seteuid(pw->pw_uid) == -1) | |
f5799ae1 | 122 | fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, |
3c0ef626 | 123 | strerror(errno)); |
124 | } | |
125 | ||
126 | /* | |
127 | * Restores to the original (privileged) uid. | |
128 | */ | |
129 | void | |
130 | restore_uid(void) | |
131 | { | |
3c0ef626 | 132 | /* it's a no-op unless privileged */ |
41b2f314 | 133 | if (!privileged) { |
134 | debug("restore_uid: (unprivileged)"); | |
3c0ef626 | 135 | return; |
41b2f314 | 136 | } |
3c0ef626 | 137 | if (!temporarily_use_uid_effective) |
138 | fatal("restore_uid: temporarily_use_uid not effective"); | |
139 | ||
140 | #ifdef SAVED_IDS_WORK_WITH_SETEUID | |
41b2f314 | 141 | debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid); |
3c0ef626 | 142 | /* Set the effective uid back to the saved privileged uid. */ |
143 | if (seteuid(saved_euid) < 0) | |
f5799ae1 | 144 | fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno)); |
3c0ef626 | 145 | if (setegid(saved_egid) < 0) |
f5799ae1 | 146 | fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno)); |
3c0ef626 | 147 | #else /* SAVED_IDS_WORK_WITH_SETEUID */ |
148 | /* | |
149 | * We are unable to restore the real uid to its unprivileged value. | |
150 | * Propagate the real uid (usually more privileged) to effective uid | |
151 | * as well. | |
152 | */ | |
153 | setuid(getuid()); | |
154 | setgid(getgid()); | |
155 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ | |
156 | ||
3c0ef626 | 157 | if (setgroups(saved_egroupslen, saved_egroups) < 0) |
158 | fatal("setgroups: %.100s", strerror(errno)); | |
3c0ef626 | 159 | temporarily_use_uid_effective = 0; |
160 | } | |
161 | ||
162 | /* | |
163 | * Permanently sets all uids to the given uid. This cannot be | |
164 | * called while temporarily_use_uid is effective. | |
165 | */ | |
166 | void | |
167 | permanently_set_uid(struct passwd *pw) | |
168 | { | |
0fff78ff | 169 | uid_t old_uid = getuid(); |
170 | gid_t old_gid = getgid(); | |
171 | ||
3c0ef626 | 172 | if (temporarily_use_uid_effective) |
f5799ae1 | 173 | fatal("permanently_set_uid: temporarily_use_uid effective"); |
41b2f314 | 174 | debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid, |
175 | (u_int)pw->pw_gid); | |
0fff78ff | 176 | |
cdd66111 | 177 | #if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID) |
0fff78ff | 178 | if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0) |
179 | fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno)); | |
180 | #elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID) | |
181 | if (setregid(pw->pw_gid, pw->pw_gid) < 0) | |
182 | fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno)); | |
183 | #else | |
184 | if (setegid(pw->pw_gid) < 0) | |
185 | fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno)); | |
3c0ef626 | 186 | if (setgid(pw->pw_gid) < 0) |
f5799ae1 | 187 | fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno)); |
0fff78ff | 188 | #endif |
189 | ||
cdd66111 | 190 | #if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID) |
0fff78ff | 191 | if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0) |
192 | fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno)); | |
193 | #elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID) | |
194 | if (setreuid(pw->pw_uid, pw->pw_uid) < 0) | |
195 | fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno)); | |
196 | #else | |
197 | # ifndef SETEUID_BREAKS_SETUID | |
198 | if (seteuid(pw->pw_uid) < 0) | |
199 | fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno)); | |
200 | # endif | |
3c0ef626 | 201 | if (setuid(pw->pw_uid) < 0) |
f5799ae1 | 202 | fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno)); |
0fff78ff | 203 | #endif |
204 | ||
996d5e62 | 205 | #ifndef HAVE_CYGWIN |
0fff78ff | 206 | /* Try restoration of GID if changed (test clearing of saved gid) */ |
996d5e62 | 207 | if (old_gid != pw->pw_gid && pw->pw_uid != 0 && |
0fff78ff | 208 | (setgid(old_gid) != -1 || setegid(old_gid) != -1)) |
209 | fatal("%s: was able to restore old [e]gid", __func__); | |
996d5e62 | 210 | #endif |
0fff78ff | 211 | |
212 | /* Verify GID drop was successful */ | |
213 | if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) { | |
cdd66111 | 214 | fatal("%s: egid incorrect gid:%u egid:%u (should be %u)", |
215 | __func__, (u_int)getgid(), (u_int)getegid(), | |
0fff78ff | 216 | (u_int)pw->pw_gid); |
217 | } | |
218 | ||
acc3d05e | 219 | #ifndef HAVE_CYGWIN |
0fff78ff | 220 | /* Try restoration of UID if changed (test clearing of saved uid) */ |
cdd66111 | 221 | if (old_uid != pw->pw_uid && |
0fff78ff | 222 | (setuid(old_uid) != -1 || seteuid(old_uid) != -1)) |
223 | fatal("%s: was able to restore old [e]uid", __func__); | |
acc3d05e | 224 | #endif |
0fff78ff | 225 | |
226 | /* Verify UID drop was successful */ | |
227 | if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) { | |
cdd66111 | 228 | fatal("%s: euid incorrect uid:%u euid:%u (should be %u)", |
229 | __func__, (u_int)getuid(), (u_int)geteuid(), | |
0fff78ff | 230 | (u_int)pw->pw_uid); |
231 | } | |
3c0ef626 | 232 | } |