blob: 31bbc0528b1173fcc56cd4e74863d8eb106d1f8a [file] [log] [blame]
David Howells9ae326a2009-04-03 16:42:41 +01001/* CacheFiles security management
2 *
3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#include <linux/fs.h>
13#include <linux/cred.h>
14#include "internal.h"
15
16/*
17 * determine the security context within which we access the cache from within
18 * the kernel
19 */
20int cachefiles_get_security_ID(struct cachefiles_cache *cache)
21{
22 struct cred *new;
23 int ret;
24
25 _enter("{%s}", cache->secctx);
26
27 new = prepare_kernel_cred(current);
28 if (!new) {
29 ret = -ENOMEM;
30 goto error;
31 }
32
33 if (cache->secctx) {
34 ret = set_security_override_from_ctx(new, cache->secctx);
35 if (ret < 0) {
36 put_cred(new);
Fabian Frederick0227d6ab2014-06-06 14:37:33 -070037 pr_err("Security denies permission to nominate security context: error %d\n",
David Howells9ae326a2009-04-03 16:42:41 +010038 ret);
39 goto error;
40 }
41 }
42
43 cache->cache_cred = new;
44 ret = 0;
45error:
46 _leave(" = %d", ret);
47 return ret;
48}
49
50/*
51 * see if mkdir and create can be performed in the root directory
52 */
53static int cachefiles_check_cache_dir(struct cachefiles_cache *cache,
54 struct dentry *root)
55{
56 int ret;
57
David Howells466b77b2015-03-17 22:26:21 +000058 ret = security_inode_mkdir(d_backing_inode(root), root, 0);
David Howells9ae326a2009-04-03 16:42:41 +010059 if (ret < 0) {
Fabian Frederick0227d6ab2014-06-06 14:37:33 -070060 pr_err("Security denies permission to make dirs: error %d",
David Howells9ae326a2009-04-03 16:42:41 +010061 ret);
62 return ret;
63 }
64
David Howells466b77b2015-03-17 22:26:21 +000065 ret = security_inode_create(d_backing_inode(root), root, 0);
David Howells9ae326a2009-04-03 16:42:41 +010066 if (ret < 0)
Fabian Frederick0227d6ab2014-06-06 14:37:33 -070067 pr_err("Security denies permission to create files: error %d",
David Howells9ae326a2009-04-03 16:42:41 +010068 ret);
69
70 return ret;
71}
72
73/*
74 * check the security details of the on-disk cache
75 * - must be called with security override in force
David Howells7ac512a2010-05-12 15:34:03 +010076 * - must return with a security override in force - even in the case of an
77 * error
David Howells9ae326a2009-04-03 16:42:41 +010078 */
79int cachefiles_determine_cache_security(struct cachefiles_cache *cache,
80 struct dentry *root,
81 const struct cred **_saved_cred)
82{
83 struct cred *new;
84 int ret;
85
86 _enter("");
87
88 /* duplicate the cache creds for COW (the override is currently in
89 * force, so we can use prepare_creds() to do this) */
90 new = prepare_creds();
91 if (!new)
92 return -ENOMEM;
93
94 cachefiles_end_secure(cache, *_saved_cred);
95
96 /* use the cache root dir's security context as the basis with
97 * which create files */
David Howells466b77b2015-03-17 22:26:21 +000098 ret = set_create_files_as(new, d_backing_inode(root));
David Howells9ae326a2009-04-03 16:42:41 +010099 if (ret < 0) {
David Howells7ac512a2010-05-12 15:34:03 +0100100 abort_creds(new);
101 cachefiles_begin_secure(cache, _saved_cred);
David Howells9ae326a2009-04-03 16:42:41 +0100102 _leave(" = %d [cfa]", ret);
103 return ret;
104 }
105
106 put_cred(cache->cache_cred);
107 cache->cache_cred = new;
108
109 cachefiles_begin_secure(cache, _saved_cred);
110 ret = cachefiles_check_cache_dir(cache, root);
111
112 if (ret == -EOPNOTSUPP)
113 ret = 0;
114 _leave(" = %d", ret);
115 return ret;
116}