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/* This file is part of GNU Dico.
Copyright (C) 2007-2024 Sergey Poznyakoff
GNU Dico 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 Dico 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 Dico. If not, see <http://www.gnu.org/licenses/>. */
#include <config.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <grp.h>
#include <errno.h>
#include <xdico.h>
#include <libi18n.h>
/* Switch to the given UID/GID */
int
switch_to_privs (uid_t uid, gid_t gid, dico_list_t retain_groups)
{
int rc = 0;
gid_t *emptygidset;
size_t size = 1, j = 1;
dico_iterator_t itr;
void *gp;
_dico_libi18n_init();
if (uid == 0) {
dico_log(L_ERR, 0, _("Refusing to run as root"));
return 1;
}
/* Create a list of supplementary groups */
size = dico_list_count(retain_groups);
size++;
emptygidset = xcalloc(size, sizeof emptygidset[0]);
emptygidset[0] = gid ? gid : getegid();
itr = dico_list_iterator(retain_groups);
for (gp = dico_iterator_first(itr); gp;
gp = dico_iterator_next(itr))
emptygidset[j++] = *(gid_t*) gp;
dico_iterator_destroy(&itr);
/* Reset group permissions */
if (geteuid() == 0 && setgroups(j, emptygidset)) {
dico_log(L_ERR, errno, _("setgroups(1, %lu) failed"),
(unsigned long) emptygidset[0]);
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)
dico_log(L_ERR, errno, _("setegid(%lu) failed"),
(unsigned long) gid);
#elif defined(HAVE_SETREGID)
if ((rc = setregid(gid, gid)) < 0)
dico_log(L_ERR, errno, _("setregid(%lu,%lu) failed"),
(unsigned long) gid, (unsigned long) gid);
#elif defined(HAVE_SETRESGID)
if ((rc = setresgid(gid, gid, gid)) < 0)
dico_log(L_ERR, errno, _("setresgid(%lu,%lu,%lu) failed"),
(unsigned long) gid,
(unsigned long) gid,
(unsigned long) gid);
#endif
if (rc == 0 && gid != 0) {
if ((rc = setgid(gid)) < 0 && getegid() != gid)
dico_log(L_ERR, errno, _("setgid(%lu) failed"),
(unsigned long) gid);
if (rc == 0 && getegid() != gid) {
dico_log(L_ERR, errno, _("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) {
dico_log(L_ERR, errno, _("setreuid(%lu,-1) failed"),
(unsigned long) uid);
rc = 1;
}
if (setuid(uid) < 0) {
dico_log(L_ERR, errno, _("second setuid(%lu) failed"),
(unsigned long) uid);
rc = 1;
}
} else
#endif
{
dico_log(L_ERR, errno, _("setuid(%lu) failed"),
(unsigned long) uid);
rc = 1;
}
}
euid = geteuid();
if (uid != 0 && setuid(0) == 0) {
dico_log(L_ERR, 0, _("seteuid(0) succeeded when it should not"));
rc = 1;
} else if (uid != euid && setuid(euid) == 0) {
dico_log(L_ERR, 0, _("Cannot drop non-root setuid privileges"));
rc = 1;
}
}
return rc;
}
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