security.c
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/* CacheFiles security management
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/fs.h>
#include <linux/cred.h>
#include "internal.h"
/*
* determine the security context within which we access the cache from within
* the kernel
*/
int cachefiles_get_security_ID(struct cachefiles_cache *cache)
{
struct cred *new;
int ret;
_enter("{%s}", cache->secctx);
new = prepare_kernel_cred(current);
if (!new) {
ret = -ENOMEM;
goto error;
}
if (cache->secctx) {
ret = set_security_override_from_ctx(new, cache->secctx);
if (ret < 0) {
put_cred(new);
pr_err("Security denies permission to nominate security context: error %d\n",
ret);
goto error;
}
}
cache->cache_cred = new;
ret = 0;
error:
_leave(" = %d", ret);
return ret;
}
/*
* see if mkdir and create can be performed in the root directory
*/
static int cachefiles_check_cache_dir(struct cachefiles_cache *cache,
struct dentry *root)
{
int ret;
ret = security_inode_mkdir(d_backing_inode(root), root, 0);
if (ret < 0) {
pr_err("Security denies permission to make dirs: error %d",
ret);
return ret;
}
ret = security_inode_create(d_backing_inode(root), root, 0);
if (ret < 0)
pr_err("Security denies permission to create files: error %d",
ret);
return ret;
}
/*
* check the security details of the on-disk cache
* - must be called with security override in force
* - must return with a security override in force - even in the case of an
* error
*/
int cachefiles_determine_cache_security(struct cachefiles_cache *cache,
struct dentry *root,
const struct cred **_saved_cred)
{
struct cred *new;
int ret;
_enter("");
/* duplicate the cache creds for COW (the override is currently in
* force, so we can use prepare_creds() to do this) */
new = prepare_creds();
if (!new)
return -ENOMEM;
cachefiles_end_secure(cache, *_saved_cred);
/* use the cache root dir's security context as the basis with
* which create files */
ret = set_create_files_as(new, d_backing_inode(root));
if (ret < 0) {
abort_creds(new);
cachefiles_begin_secure(cache, _saved_cred);
_leave(" = %d [cfa]", ret);
return ret;
}
put_cred(cache->cache_cred);
cache->cache_cred = new;
cachefiles_begin_secure(cache, _saved_cred);
ret = cachefiles_check_cache_dir(cache, root);
if (ret == -EOPNOTSUPP)
ret = 0;
_leave(" = %d", ret);
return ret;
}