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3c33c1b6 | 1 | /* $OpenBSD: uidswap.c,v 1.29 2006/06/08 14:45:49 markus Exp $ */ |
8efc0c15 | 2 | /* |
5260325f | 3 | * Author: Tatu Ylonen <ylo@cs.hut.fi> |
4 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
5 | * All rights reserved | |
5260325f | 6 | * Code for uid-swapping. |
bcbf86ec | 7 | * |
8 | * As far as I am concerned, the code I have written for this software | |
9 | * can be used freely for any purpose. Any derived versions of this | |
10 | * software must be clearly marked as such, and if the derived work is | |
11 | * incompatible with the protocol description in the RFC file, it must be | |
12 | * called by a name other than "ssh" or "Secure Shell". | |
5260325f | 13 | */ |
8efc0c15 | 14 | |
15 | #include "includes.h" | |
8efc0c15 | 16 | |
42f11eb2 | 17 | #include "log.h" |
8efc0c15 | 18 | #include "uidswap.h" |
13dff404 | 19 | #include "xmalloc.h" |
8efc0c15 | 20 | |
5260325f | 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 | */ | |
8efc0c15 | 29 | |
0096ac62 | 30 | #if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS) |
8efc0c15 | 31 | /* Lets assume that posix saved ids also work with seteuid, even though that |
32 | is not part of the posix specification. */ | |
0096ac62 | 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 | |
f8252c48 | 38 | |
8efc0c15 | 39 | /* Saved effective uid. */ |
63bd8c36 | 40 | static int privileged = 0; |
41 | static int temporarily_use_uid_effective = 0; | |
13dff404 | 42 | static gid_t *saved_egroups = NULL, *user_groups = NULL; |
63bd8c36 | 43 | static int saved_egroupslen = -1, user_groupslen = -1; |
f8252c48 | 44 | |
5260325f | 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 | */ | |
6ae2364d | 49 | void |
63bd8c36 | 50 | temporarily_use_uid(struct passwd *pw) |
8efc0c15 | 51 | { |
f8252c48 | 52 | /* Save the current euid, and egroups. */ |
0096ac62 | 53 | #ifdef SAVED_IDS_WORK_WITH_SETEUID |
f8252c48 | 54 | saved_euid = geteuid(); |
0096ac62 | 55 | saved_egid = getegid(); |
0df3a240 | 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); | |
c2736f7f | 59 | #ifndef HAVE_CYGWIN |
f8252c48 | 60 | if (saved_euid != 0) { |
61 | privileged = 0; | |
62 | return; | |
63 | } | |
c2736f7f | 64 | #endif |
0096ac62 | 65 | #else |
66 | if (geteuid() != 0) { | |
67 | privileged = 0; | |
68 | return; | |
69 | } | |
70 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ | |
71 | ||
f8252c48 | 72 | privileged = 1; |
73 | temporarily_use_uid_effective = 1; | |
13dff404 | 74 | |
75 | saved_egroupslen = getgroups(0, NULL); | |
f8252c48 | 76 | if (saved_egroupslen < 0) |
77 | fatal("getgroups: %.100s", strerror(errno)); | |
13dff404 | 78 | if (saved_egroupslen > 0) { |
79 | saved_egroups = xrealloc(saved_egroups, | |
c5d10563 | 80 | saved_egroupslen, sizeof(gid_t)); |
13dff404 | 81 | if (getgroups(saved_egroupslen, saved_egroups) < 0) |
82 | fatal("getgroups: %.100s", strerror(errno)); | |
83 | } else { /* saved_egroupslen == 0 */ | |
972fc531 | 84 | if (saved_egroups != NULL) |
13dff404 | 85 | xfree(saved_egroups); |
86 | } | |
f8252c48 | 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)); | |
13dff404 | 93 | |
94 | user_groupslen = getgroups(0, NULL); | |
f8252c48 | 95 | if (user_groupslen < 0) |
96 | fatal("getgroups: %.100s", strerror(errno)); | |
13dff404 | 97 | if (user_groupslen > 0) { |
98 | user_groups = xrealloc(user_groups, | |
c5d10563 | 99 | user_groupslen, sizeof(gid_t)); |
13dff404 | 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 | } | |
f8252c48 | 106 | } |
107 | /* Set the effective uid to the given (unprivileged) uid. */ | |
d98d029a | 108 | if (setgroups(user_groupslen, user_groups) < 0) |
63bd8c36 | 109 | fatal("setgroups: %.100s", strerror(errno)); |
0096ac62 | 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 */ | |
d98d029a | 118 | if (setegid(pw->pw_gid) < 0) |
caa49784 | 119 | fatal("setegid %u: %.100s", (u_int)pw->pw_gid, |
f8252c48 | 120 | strerror(errno)); |
121 | if (seteuid(pw->pw_uid) == -1) | |
caa49784 | 122 | fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, |
f8252c48 | 123 | strerror(errno)); |
8efc0c15 | 124 | } |
f8252c48 | 125 | |
3c33c1b6 | 126 | void |
127 | permanently_drop_suid(uid_t uid) | |
128 | { | |
129 | uid_t old_uid = getuid(); | |
130 | ||
131 | debug("permanently_drop_suid: %u", (u_int)uid); | |
132 | #if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID) | |
133 | if (setresuid(uid, uid, uid) < 0) | |
134 | fatal("setresuid %u: %.100s", (u_int)uid, strerror(errno)); | |
135 | #elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID) | |
136 | if (setreuid(uid, uid) < 0) | |
137 | fatal("setreuid %u: %.100s", (u_int)uid, strerror(errno)); | |
138 | #else | |
139 | # ifndef SETEUID_BREAKS_SETUID | |
140 | if (seteuid(uid) < 0) | |
141 | fatal("seteuid %u: %.100s", (u_int)uid, strerror(errno)); | |
142 | # endif | |
143 | if (setuid(uid) < 0) | |
144 | fatal("setuid %u: %.100s", (u_int)uid, strerror(errno)); | |
145 | #endif | |
146 | ||
147 | #ifndef HAVE_CYGWIN | |
148 | /* Try restoration of UID if changed (test clearing of saved uid) */ | |
149 | if (old_uid != uid && | |
150 | (setuid(old_uid) != -1 || seteuid(old_uid) != -1)) | |
151 | fatal("%s: was able to restore old [e]uid", __func__); | |
152 | #endif | |
153 | ||
154 | /* Verify UID drop was successful */ | |
155 | if (getuid() != uid || geteuid() != uid) { | |
156 | fatal("%s: euid incorrect uid:%u euid:%u (should be %u)", | |
157 | __func__, (u_int)getuid(), (u_int)geteuid(), (u_int)uid); | |
158 | } | |
159 | } | |
160 | ||
5260325f | 161 | /* |
a3626e12 | 162 | * Restores to the original (privileged) uid. |
5260325f | 163 | */ |
6ae2364d | 164 | void |
1e3b8b07 | 165 | restore_uid(void) |
8efc0c15 | 166 | { |
63bd8c36 | 167 | /* it's a no-op unless privileged */ |
0df3a240 | 168 | if (!privileged) { |
169 | debug("restore_uid: (unprivileged)"); | |
63bd8c36 | 170 | return; |
0df3a240 | 171 | } |
63bd8c36 | 172 | if (!temporarily_use_uid_effective) |
173 | fatal("restore_uid: temporarily_use_uid not effective"); | |
0096ac62 | 174 | |
175 | #ifdef SAVED_IDS_WORK_WITH_SETEUID | |
13979d47 | 176 | debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid); |
a3626e12 | 177 | /* Set the effective uid back to the saved privileged uid. */ |
5260325f | 178 | if (seteuid(saved_euid) < 0) |
caa49784 | 179 | fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno)); |
0096ac62 | 180 | if (setegid(saved_egid) < 0) |
caa49784 | 181 | fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno)); |
0096ac62 | 182 | #else /* SAVED_IDS_WORK_WITH_SETEUID */ |
183 | /* | |
184 | * We are unable to restore the real uid to its unprivileged value. | |
185 | * Propagate the real uid (usually more privileged) to effective uid | |
186 | * as well. | |
187 | */ | |
188 | setuid(getuid()); | |
189 | setgid(getgid()); | |
190 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ | |
191 | ||
d98d029a | 192 | if (setgroups(saved_egroupslen, saved_egroups) < 0) |
63bd8c36 | 193 | fatal("setgroups: %.100s", strerror(errno)); |
63bd8c36 | 194 | temporarily_use_uid_effective = 0; |
8efc0c15 | 195 | } |
196 | ||
5260325f | 197 | /* |
198 | * Permanently sets all uids to the given uid. This cannot be | |
199 | * called while temporarily_use_uid is effective. | |
200 | */ | |
6ae2364d | 201 | void |
63bd8c36 | 202 | permanently_set_uid(struct passwd *pw) |
8efc0c15 | 203 | { |
688eed4a | 204 | uid_t old_uid = getuid(); |
205 | gid_t old_gid = getgid(); | |
206 | ||
82aeee5d | 207 | if (pw == NULL) |
208 | fatal("permanently_set_uid: no user given"); | |
63bd8c36 | 209 | if (temporarily_use_uid_effective) |
95f20fe8 | 210 | fatal("permanently_set_uid: temporarily_use_uid effective"); |
0df3a240 | 211 | debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid, |
212 | (u_int)pw->pw_gid); | |
688eed4a | 213 | |
9a3fe0e2 | 214 | #if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID) |
688eed4a | 215 | if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0) |
216 | fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno)); | |
3b8dff69 | 217 | #elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID) |
688eed4a | 218 | if (setregid(pw->pw_gid, pw->pw_gid) < 0) |
219 | fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno)); | |
220 | #else | |
fa5120a0 | 221 | if (setegid(pw->pw_gid) < 0) |
222 | fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno)); | |
63bd8c36 | 223 | if (setgid(pw->pw_gid) < 0) |
caa49784 | 224 | fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno)); |
688eed4a | 225 | #endif |
226 | ||
9a3fe0e2 | 227 | #if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID) |
688eed4a | 228 | if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0) |
229 | fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno)); | |
3b8dff69 | 230 | #elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID) |
f5db6a03 | 231 | if (setreuid(pw->pw_uid, pw->pw_uid) < 0) |
232 | fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno)); | |
688eed4a | 233 | #else |
234 | # ifndef SETEUID_BREAKS_SETUID | |
fa5120a0 | 235 | if (seteuid(pw->pw_uid) < 0) |
236 | fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno)); | |
688eed4a | 237 | # endif |
a3626e12 | 238 | if (setuid(pw->pw_uid) < 0) |
caa49784 | 239 | fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno)); |
688eed4a | 240 | #endif |
241 | ||
8f817407 | 242 | #ifndef HAVE_CYGWIN |
688eed4a | 243 | /* Try restoration of GID if changed (test clearing of saved gid) */ |
8f817407 | 244 | if (old_gid != pw->pw_gid && pw->pw_uid != 0 && |
688eed4a | 245 | (setgid(old_gid) != -1 || setegid(old_gid) != -1)) |
f5db6a03 | 246 | fatal("%s: was able to restore old [e]gid", __func__); |
8f817407 | 247 | #endif |
688eed4a | 248 | |
249 | /* Verify GID drop was successful */ | |
250 | if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) { | |
aff51935 | 251 | fatal("%s: egid incorrect gid:%u egid:%u (should be %u)", |
252 | __func__, (u_int)getgid(), (u_int)getegid(), | |
688eed4a | 253 | (u_int)pw->pw_gid); |
254 | } | |
255 | ||
51e7d820 | 256 | #ifndef HAVE_CYGWIN |
688eed4a | 257 | /* Try restoration of UID if changed (test clearing of saved uid) */ |
aff51935 | 258 | if (old_uid != pw->pw_uid && |
688eed4a | 259 | (setuid(old_uid) != -1 || seteuid(old_uid) != -1)) |
f5db6a03 | 260 | fatal("%s: was able to restore old [e]uid", __func__); |
51e7d820 | 261 | #endif |
688eed4a | 262 | |
263 | /* Verify UID drop was successful */ | |
264 | if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) { | |
aff51935 | 265 | fatal("%s: euid incorrect uid:%u euid:%u (should be %u)", |
266 | __func__, (u_int)getuid(), (u_int)geteuid(), | |
688eed4a | 267 | (u_int)pw->pw_uid); |
268 | } | |
8efc0c15 | 269 | } |