userprivs.c
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/* GNU Mailutils -- a suite of utilities for electronic mail
Copyright (C) 2008, 2010 Free Software Foundation, Inc.
GNU Mailutils is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GNU Mailutils is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Mailutils; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301 USA */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <pwd.h>
#include <grp.h>
#include <unistd.h>
#include <mailutils/assoc.h>
#include <mailutils/errno.h>
#include <mailutils/error.h>
#include <mailutils/errno.h>
#include <mailutils/nls.h>
#include <mailutils/list.h>
#include <mailutils/iterator.h>
#include <xalloc.h>
/* Switch to the given UID/GID */
int
mu_switch_to_privs (uid_t uid, gid_t gid, mu_list_t retain_groups)
{
int rc = 0;
gid_t *emptygidset;
size_t size = 1, j = 1;
mu_iterator_t itr;
if (uid == 0)
return 0;
/* Create a list of supplementary groups */
mu_list_count (retain_groups, &size);
size++;
emptygidset = xmalloc (size * sizeof emptygidset[0]);
emptygidset[0] = gid ? gid : getegid ();
if (mu_list_get_iterator (retain_groups, &itr) == 0)
{
for (mu_iterator_first (itr);
!mu_iterator_is_done (itr); mu_iterator_next (itr))
mu_iterator_current (itr,
(void **)(emptygidset + j++));
mu_iterator_destroy (&itr);
}
/* Reset group permissions */
if (geteuid () == 0 && setgroups (j, emptygidset))
{
mu_error(_("setgroups(1, %lu) failed: %s"),
(unsigned long) emptygidset[0], mu_strerror (errno));
rc = 1;
}
free (emptygidset);
/* Switch to the user's gid. On some OSes the effective gid must
be reset first */
#if defined(HAVE_SETEGID)
if ((rc = setegid (gid)) < 0)
mu_error (_("setegid(%lu) failed: %s"),
(unsigned long) gid, mu_strerror (errno));
#elif defined(HAVE_SETREGID)
if ((rc = setregid (gid, gid)) < 0)
mu_error (_("setregid(%lu,%lu) failed: %s"),
(unsigned long) gid, (unsigned long) gid,
mu_strerror (errno));
#elif defined(HAVE_SETRESGID)
if ((rc = setresgid (gid, gid, gid)) < 0)
mu_error (_("setresgid(%lu,%lu,%lu) failed: %s"),
(unsigned long) gid,
(unsigned long) gid,
(unsigned long) gid,
mu_strerror (errno));
#endif
if (rc == 0 && gid != 0)
{
if ((rc = setgid (gid)) < 0 && getegid () != gid)
mu_error (_("setgid(%lu) failed: %s"),
(unsigned long) gid, mu_strerror (errno));
if (rc == 0 && getegid () != gid)
{
mu_error (_("Cannot set effective gid to %lu"),
(unsigned long) gid);
rc = 1;
}
}
/* Now reset uid */
if (rc == 0 && uid != 0)
{
uid_t euid;
if (setuid (uid) || geteuid () != uid
|| (getuid () != uid && (geteuid () == 0 || getuid () == 0)))
{
#if defined(HAVE_SETREUID)
if (geteuid () != uid)
{
if (setreuid (uid, -1) < 0)
{
mu_error (_("setreuid(%lu,-1) failed: %s"),
(unsigned long) uid,
mu_strerror (errno));
rc = 1;
}
if (setuid (uid) < 0)
{
mu_error (_("second setuid(%lu) failed: %s"),
(unsigned long) uid, mu_strerror (errno));
rc = 1;
}
} else
#endif
{
mu_error (_("setuid(%lu) failed: %s"),
(unsigned long) uid,
mu_strerror (errno));
rc = 1;
}
}
euid = geteuid ();
if (uid != 0 && setuid (0) == 0)
{
mu_error (_("seteuid(0) succeeded when it should not"));
rc = 1;
}
else if (uid != euid && setuid (euid) == 0)
{
mu_error (_("Cannot drop non-root setuid privileges"));
rc = 1;
}
}
return rc;
}