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/*
uidswap.c
Author: Tatu Ylonen <ylo@cs.hut.fi>
Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
All rights reserved
Created: Sat Sep 9 01:56:14 1995 ylo
Code for uid-swapping.
*/
#include "includes.h"
RCSID("$Id: uidswap.c,v 1.1 1999/09/26 20:53:38 deraadt Exp $");
#include "ssh.h"
#include "uidswap.h"
/* Note: all these functions must work in all of the following cases:
1. euid=0, ruid=0
2. euid=0, ruid!=0
3. euid!=0, ruid!=0
Additionally, they must work regardless of whether the system has
POSIX saved uids or not. */
#ifdef HAVE_SETEUID
#ifdef _POSIX_SAVED_IDS
/* Lets assume that posix saved ids also work with seteuid, even though that
is not part of the posix specification. */
#define SAVED_IDS_WORK_WITH_SETEUID
#endif /* _POSIX_SAVED_IDS */
/* Saved effective uid. */
static uid_t saved_euid = 0;
/* Temporarily changes to the given uid. If the effective user id is not
root, this does nothing. This call cannot be nested. */
void temporarily_use_uid(uid_t uid)
{
#ifdef SAVED_IDS_WORK_WITH_SETEUID
/* Save the current euid. */
saved_euid = geteuid();
/* Set the effective uid to the given (unprivileged) uid. */
if (seteuid(uid) == -1)
debug("seteuid %d: %.100s", (int)uid, strerror(errno));
#else /* SAVED_IDS_WORK_WITH_SETUID */
/* Propagate the privileged uid to all of our uids. */
if (setuid(geteuid()) < 0)
debug("setuid %d: %.100s", (int)geteuid(), strerror(errno));
/* Set the effective uid to the given (unprivileged) uid. */
if (seteuid(uid) == -1)
debug("seteuid %d: %.100s", (int)uid, strerror(errno));
#endif /* SAVED_IDS_WORK_WITH_SETEUID */
}
/* Restores to the original uid. */
void restore_uid()
{
#ifdef SAVED_IDS_WORK_WITH_SETEUID
/* Set the effective uid back to the saved uid. */
if (seteuid(saved_euid) < 0)
debug("seteuid %d: %.100s", (int)saved_euid, strerror(errno));
#else /* SAVED_IDS_WORK_WITH_SETEUID */
/* We are unable to restore the real uid to its unprivileged value. */
/* Propagate the real uid (usually more privileged) to effective uid
as well. */
setuid(getuid());
#endif /* SAVED_IDS_WORK_WITH_SETEUID */
}
/* Permanently sets all uids to the given uid. This cannot be called while
temporarily_use_uid is effective. */
void permanently_set_uid(uid_t uid)
{
if (setuid(uid) < 0)
debug("setuid %d: %.100s", (int)uid, strerror(errno));
}
#else /* HAVE_SETEUID */
YOUR_SYSTEM_DOES_NOT_PERMIT_UID_SWAPPING_READ_AND_EDIT_UIDSWAP_C;
/* If we ever come here, if means that your system does not support any of
the uid swapping methods we are aware of. Tough. This means that
ssh will have to read certain files as root, which causes some security
problems. Unless your are very concerned about security, you can
comment out the above line. The effect is that local users on your
machine might be able to read each other's files. Also, you may encounter
problems if home directories are on a NFS volume. You may also
encounter other problems; please don't complain unless you have some idea
how to fix it. */
void temporarily_use_uid(uid_t uid)
{
}
void restore_uid()
{
}
void permanently_set_uid(uid_t uid)
{
if (setuid(uid) < 0)
debug("setuid %d: %.100s", (int)uid, strerror(errno));
}
#endif /* HAVE_SETEUID */
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