2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * Created: Sat Sep 9 01:56:14 1995 ylo
6 * Code for uid-swapping.
16 * Note: all these functions must work in all of the following cases:
20 * Additionally, they must work regardless of whether the system has
21 * POSIX saved uids or not.
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 */
30 /* Saved effective uid. */
31 static uid_t saved_euid = 0;
34 * Temporarily changes to the given uid. If the effective user
35 * id is not root, this does nothing. This call cannot be nested.
38 temporarily_use_uid(uid_t uid)
40 #ifdef SAVED_IDS_WORK_WITH_SETEUID
41 /* Save the current euid. */
42 saved_euid = geteuid();
44 /* Set the effective uid to the given (unprivileged) uid. */
45 if (seteuid(uid) == -1)
46 debug("seteuid %d: %.100s", (int) uid, strerror(errno));
47 #else /* SAVED_IDS_WORK_WITH_SETUID */
48 /* Propagate the privileged uid to all of our uids. */
49 if (setuid(geteuid()) < 0)
50 debug("setuid %d: %.100s", (int) geteuid(), strerror(errno));
52 /* Set the effective uid to the given (unprivileged) uid. */
53 if (seteuid(uid) == -1)
54 debug("seteuid %d: %.100s", (int) uid, strerror(errno));
55 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
59 * Restores to the original uid.
64 #ifdef SAVED_IDS_WORK_WITH_SETEUID
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));
68 #else /* SAVED_IDS_WORK_WITH_SETEUID */
70 * We are unable to restore the real uid to its unprivileged value.
71 * Propagate the real uid (usually more privileged) to effective uid
75 #endif /* SAVED_IDS_WORK_WITH_SETEUID */
79 * Permanently sets all uids to the given uid. This cannot be
80 * called while temporarily_use_uid is effective.
83 permanently_set_uid(uid_t uid)
86 debug("setuid %d: %.100s", (int) uid, strerror(errno));