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8efc0c15 | 1 | /* |
2 | ||
3 | uidswap.c | |
4 | ||
5 | Author: Tatu Ylonen <ylo@cs.hut.fi> | |
6 | ||
7 | Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
8 | All rights reserved | |
9 | ||
10 | Created: Sat Sep 9 01:56:14 1995 ylo | |
11 | ||
12 | Code for uid-swapping. | |
13 | ||
14 | */ | |
15 | ||
16 | #include "includes.h" | |
17 | RCSID("$Id$"); | |
18 | ||
19 | #include "ssh.h" | |
20 | #include "uidswap.h" | |
21 | ||
22 | /* Note: all these functions must work in all of the following cases: | |
23 | ||
24 | 1. euid=0, ruid=0 | |
25 | 2. euid=0, ruid!=0 | |
26 | 3. euid!=0, ruid!=0 | |
27 | ||
28 | Additionally, they must work regardless of whether the system has | |
29 | POSIX saved uids or not. */ | |
30 | ||
31 | #ifdef _POSIX_SAVED_IDS | |
32 | /* Lets assume that posix saved ids also work with seteuid, even though that | |
33 | is not part of the posix specification. */ | |
34 | #define SAVED_IDS_WORK_WITH_SETEUID | |
35 | #endif /* _POSIX_SAVED_IDS */ | |
36 | ||
37 | /* Saved effective uid. */ | |
38 | static uid_t saved_euid = 0; | |
39 | ||
40 | /* Temporarily changes to the given uid. If the effective user id is not | |
41 | root, this does nothing. This call cannot be nested. */ | |
42 | ||
43 | void temporarily_use_uid(uid_t uid) | |
44 | { | |
45 | #ifdef SAVED_IDS_WORK_WITH_SETEUID | |
46 | ||
47 | /* Save the current euid. */ | |
48 | saved_euid = geteuid(); | |
49 | ||
50 | /* Set the effective uid to the given (unprivileged) uid. */ | |
51 | if (seteuid(uid) == -1) | |
52 | debug("seteuid %d: %.100s", (int)uid, strerror(errno)); | |
53 | ||
54 | #else /* SAVED_IDS_WORK_WITH_SETUID */ | |
55 | ||
56 | /* Propagate the privileged uid to all of our uids. */ | |
57 | if (setuid(geteuid()) < 0) | |
58 | debug("setuid %d: %.100s", (int)geteuid(), strerror(errno)); | |
59 | ||
60 | /* Set the effective uid to the given (unprivileged) uid. */ | |
61 | if (seteuid(uid) == -1) | |
62 | debug("seteuid %d: %.100s", (int)uid, strerror(errno)); | |
63 | ||
64 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ | |
65 | ||
66 | } | |
67 | ||
68 | /* Restores to the original uid. */ | |
69 | ||
70 | void restore_uid() | |
71 | { | |
72 | #ifdef SAVED_IDS_WORK_WITH_SETEUID | |
73 | ||
74 | /* Set the effective uid back to the saved uid. */ | |
75 | if (seteuid(saved_euid) < 0) | |
76 | debug("seteuid %d: %.100s", (int)saved_euid, strerror(errno)); | |
77 | ||
78 | #else /* SAVED_IDS_WORK_WITH_SETEUID */ | |
79 | ||
80 | /* We are unable to restore the real uid to its unprivileged value. */ | |
81 | /* Propagate the real uid (usually more privileged) to effective uid | |
82 | as well. */ | |
83 | setuid(getuid()); | |
84 | ||
85 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ | |
86 | } | |
87 | ||
88 | /* Permanently sets all uids to the given uid. This cannot be called while | |
89 | temporarily_use_uid is effective. */ | |
90 | ||
91 | void permanently_set_uid(uid_t uid) | |
92 | { | |
93 | if (setuid(uid) < 0) | |
94 | debug("setuid %d: %.100s", (int)uid, strerror(errno)); | |
95 | } |