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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 1.2 1999/09/30 08:34:25 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 _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));
}
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