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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 | |
5 | * Created: Sat Sep 9 01:56:14 1995 ylo | |
6 | * Code for uid-swapping. | |
7 | */ | |
8efc0c15 | 8 | |
9 | #include "includes.h" | |
10 | RCSID("$Id$"); | |
11 | ||
12 | #include "ssh.h" | |
13 | #include "uidswap.h" | |
14 | ||
5260325f | 15 | /* |
16 | * Note: all these functions must work in all of the following cases: | |
17 | * 1. euid=0, ruid=0 | |
18 | * 2. euid=0, ruid!=0 | |
19 | * 3. euid!=0, ruid!=0 | |
20 | * Additionally, they must work regardless of whether the system has | |
21 | * POSIX saved uids or not. | |
22 | */ | |
8efc0c15 | 23 | |
24 | #ifdef _POSIX_SAVED_IDS | |
25 | /* Lets assume that posix saved ids also work with seteuid, even though that | |
26 | is not part of the posix specification. */ | |
27 | #define SAVED_IDS_WORK_WITH_SETEUID | |
28 | #endif /* _POSIX_SAVED_IDS */ | |
29 | ||
30 | /* Saved effective uid. */ | |
31 | static uid_t saved_euid = 0; | |
32 | ||
5260325f | 33 | /* |
34 | * Temporarily changes to the given uid. If the effective user | |
35 | * id is not root, this does nothing. This call cannot be nested. | |
36 | */ | |
37 | void | |
38 | temporarily_use_uid(uid_t uid) | |
8efc0c15 | 39 | { |
40 | #ifdef SAVED_IDS_WORK_WITH_SETEUID | |
5260325f | 41 | /* Save the current euid. */ |
42 | saved_euid = geteuid(); | |
8efc0c15 | 43 | |
5260325f | 44 | /* Set the effective uid to the given (unprivileged) uid. */ |
45 | if (seteuid(uid) == -1) | |
46 | debug("seteuid %d: %.100s", (int) uid, strerror(errno)); | |
8efc0c15 | 47 | #else /* SAVED_IDS_WORK_WITH_SETUID */ |
5260325f | 48 | /* Propagate the privileged uid to all of our uids. */ |
49 | if (setuid(geteuid()) < 0) | |
50 | debug("setuid %d: %.100s", (int) geteuid(), strerror(errno)); | |
8efc0c15 | 51 | |
5260325f | 52 | /* Set the effective uid to the given (unprivileged) uid. */ |
53 | if (seteuid(uid) == -1) | |
54 | debug("seteuid %d: %.100s", (int) uid, strerror(errno)); | |
8efc0c15 | 55 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ |
8efc0c15 | 56 | } |
57 | ||
5260325f | 58 | /* |
59 | * Restores to the original uid. | |
60 | */ | |
61 | void | |
62 | restore_uid() | |
8efc0c15 | 63 | { |
64 | #ifdef SAVED_IDS_WORK_WITH_SETEUID | |
5260325f | 65 | /* Set the effective uid back to the saved uid. */ |
66 | if (seteuid(saved_euid) < 0) | |
67 | debug("seteuid %d: %.100s", (int) saved_euid, strerror(errno)); | |
8efc0c15 | 68 | #else /* SAVED_IDS_WORK_WITH_SETEUID */ |
aa3378df | 69 | /* |
70 | * We are unable to restore the real uid to its unprivileged value. | |
71 | * Propagate the real uid (usually more privileged) to effective uid | |
72 | * as well. | |
73 | */ | |
5260325f | 74 | setuid(getuid()); |
8efc0c15 | 75 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ |
76 | } | |
77 | ||
5260325f | 78 | /* |
79 | * Permanently sets all uids to the given uid. This cannot be | |
80 | * called while temporarily_use_uid is effective. | |
81 | */ | |
82 | void | |
83 | permanently_set_uid(uid_t uid) | |
8efc0c15 | 84 | { |
5260325f | 85 | if (setuid(uid) < 0) |
86 | debug("setuid %d: %.100s", (int) uid, strerror(errno)); | |
8efc0c15 | 87 | } |