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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* This file is part of libmount from util-linux project.
*
* Copyright (C) 2023 Karel Zak <kzak@redhat.com>
*
* libmount is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
*
* Please, see the comment in libmount/src/hooks.c to understand how hooks work.
*/
#ifdef HAVE_LIBSELINUX
#include <selinux/selinux.h>
#include <selinux/context.h>
#include "mountP.h"
#include "fileutils.h"
#include "linux_version.h"
static int hookset_deinit(struct libmnt_context *cxt, const struct libmnt_hookset *hs)
{
void *data = NULL;
DBG(HOOK, ul_debugobj(hs, "deinit '%s'", hs->name));
/* remove all our hooks and free hook data */
while (mnt_context_remove_hook(cxt, hs, 0, &data) == 0) {
if (data)
free(data);
data = NULL;
}
return 0;
}
static inline int is_option(const char *name, const char *const *names)
{
const char *const *p;
for (p = names; p && *p; p++) {
if (strcmp(name, *p) == 0)
return 1;
}
return 0;
}
/* Converts rootcontext=@target to the real selinxu context
*/
static int hook_selinux_target(
struct libmnt_context *cxt,
const struct libmnt_hookset *hs,
void *data __attribute__((__unused__)))
{
struct libmnt_optlist *ol;
struct libmnt_opt *opt;
const char *tgt, *val;
char *raw = NULL;
int rc = 0;
assert(cxt);
tgt = mnt_fs_get_target(cxt->fs);
if (!tgt)
return 0;
if (cxt->action != MNT_ACT_MOUNT)
return 0;
ol = mnt_context_get_optlist(cxt);
if (!ol)
return -EINVAL;
opt = mnt_optlist_get_named(ol, "rootcontext", NULL);
if (!opt)
return 0;
val = mnt_opt_get_value(opt);
if (!val || strcmp(val, "@target") != 0)
return 0;
rc = getfilecon_raw(tgt, &raw);
if (rc <= 0 || !raw) {
rc = errno ? -errno : -EINVAL;
DBG(HOOK, ul_debugobj(hs, " SELinux fix @target failed [rc=%d]", rc));
} else {
DBG(HOOK, ul_debugobj(hs, " SELinux fix @target to %s", raw));
rc = 0; /* getfilecon_raw(3) returns the size of the extended attribute value */
}
if (!rc)
rc = mnt_opt_set_quoted_value(opt, raw);
if (raw)
freecon(raw);
return rc != 0 ? -MNT_ERR_MOUNTOPT : 0;
}
static int hook_prepare_options(
struct libmnt_context *cxt,
const struct libmnt_hookset *hs,
void *data __attribute__((__unused__)))
{
int rc = 0, se_fix = 0, se_rem = 0;
struct libmnt_optlist *ol;
assert(cxt);
ol = mnt_context_get_optlist(cxt);
if (!ol)
return -EINVAL;
if (!is_selinux_enabled())
/* Always remove SELinux garbage if SELinux disabled */
se_rem = 1;
else if (mnt_optlist_is_remount(ol))
/*
* Linux kernel < 2.6.39 does not support remount operation
* with any selinux specific mount options.
*
* Kernel 2.6.39 commits: ff36fe2c845cab2102e4826c1ffa0a6ebf487c65
* 026eb167ae77244458fa4b4b9fc171209c079ba7
* fix this odd behavior, so we don't have to care about it in
* userspace.
*/
se_rem = get_linux_version() < KERNEL_VERSION(2, 6, 39);
else
/* For normal mount, contexts are translated */
se_fix = 1;
DBG(HOOK, ul_debugobj(hs, " SELinux fix options"));
/* Fix SELinux contexts */
if (se_rem || se_fix) {
static const char *const selinux_options[] = {
"context",
"fscontext",
"defcontext",
"rootcontext",
"seclabel",
NULL
};
struct libmnt_iter itr;
struct libmnt_opt *opt;
mnt_reset_iter(&itr, MNT_ITER_FORWARD);
while (mnt_optlist_next_opt(ol, &itr, &opt) == 0) {
const char *opt_name = mnt_opt_get_name(opt);
if (!is_option(opt_name, selinux_options))
continue;
if (se_rem)
rc = mnt_optlist_remove_opt(ol, opt);
else if (se_fix && mnt_opt_has_value(opt)) {
const char *val = mnt_opt_get_value(opt);
char *raw = NULL;
/* @target placeholder is replaced later when target
* is already avalable. The mountpoint does not have to exist
* yet (for example "-o X-mount.mkdir=" or --target-prefix).
*/
if (strcmp(opt_name, "rootcontext") == 0 &&
strcmp(val, "@target") == 0) {
rc = mnt_context_insert_hook(cxt, "__mkdir",
hs, MNT_STAGE_PREP_TARGET, NULL,
hook_selinux_target);
continue;
} else {
rc = selinux_trans_to_raw_context(val, &raw);
if (rc == -1 || !raw)
rc = -EINVAL;
}
if (!rc) {
DBG(HOOK, ul_debugobj(hs, " %s: %s to %s",
opt_name, val, raw));
rc = mnt_opt_set_quoted_value(opt, raw);
}
if (raw)
freecon(raw);
/* temporary for broken fsconfig() syscall */
cxt->has_selinux_opt = 1;
}
if (rc)
break;
}
}
return rc != 0 ? -MNT_ERR_MOUNTOPT : 0;
}
const struct libmnt_hookset hookset_selinux =
{
.name = "__selinux",
.firststage = MNT_STAGE_PREP_OPTIONS,
.firstcall = hook_prepare_options,
.deinit = hookset_deinit
};
#endif /* HAVE_LIBSELINUX */
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