aboutsummaryrefslogtreecommitdiffstats
path: root/security/integrity/evm/evm_crypto.c
diff options
context:
space:
mode:
Diffstat (limited to 'security/integrity/evm/evm_crypto.c')
-rw-r--r--security/integrity/evm/evm_crypto.c183
1 files changed, 183 insertions, 0 deletions
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
new file mode 100644
index 000000000000..d49bb002f3da
--- /dev/null
+++ b/security/integrity/evm/evm_crypto.c
@@ -0,0 +1,183 @@
1/*
2 * Copyright (C) 2005-2010 IBM Corporation
3 *
4 * Authors:
5 * Mimi Zohar <zohar@us.ibm.com>
6 * Kylene Hall <kjhall@us.ibm.com>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation, version 2 of the License.
11 *
12 * File: evm_crypto.c
13 * Using root's kernel master key (kmk), calculate the HMAC
14 */
15
16#include <linux/module.h>
17#include <linux/crypto.h>
18#include <linux/xattr.h>
19#include <linux/scatterlist.h>
20#include <keys/encrypted-type.h>
21#include "evm.h"
22
23#define EVMKEY "evm-key"
24#define MAX_KEY_SIZE 128
25static unsigned char evmkey[MAX_KEY_SIZE];
26static int evmkey_len = MAX_KEY_SIZE;
27
28static int init_desc(struct hash_desc *desc)
29{
30 int rc;
31
32 desc->tfm = crypto_alloc_hash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
33 if (IS_ERR(desc->tfm)) {
34 pr_info("Can not allocate %s (reason: %ld)\n",
35 evm_hmac, PTR_ERR(desc->tfm));
36 rc = PTR_ERR(desc->tfm);
37 return rc;
38 }
39 desc->flags = 0;
40 rc = crypto_hash_setkey(desc->tfm, evmkey, evmkey_len);
41 if (rc)
42 goto out;
43 rc = crypto_hash_init(desc);
44out:
45 if (rc)
46 crypto_free_hash(desc->tfm);
47 return rc;
48}
49
50/* Protect against 'cutting & pasting' security.evm xattr, include inode
51 * specific info.
52 *
53 * (Additional directory/file metadata needs to be added for more complete
54 * protection.)
55 */
56static void hmac_add_misc(struct hash_desc *desc, struct inode *inode,
57 char *digest)
58{
59 struct h_misc {
60 unsigned long ino;
61 __u32 generation;
62 uid_t uid;
63 gid_t gid;
64 umode_t mode;
65 } hmac_misc;
66 struct scatterlist sg[1];
67
68 memset(&hmac_misc, 0, sizeof hmac_misc);
69 hmac_misc.ino = inode->i_ino;
70 hmac_misc.generation = inode->i_generation;
71 hmac_misc.uid = inode->i_uid;
72 hmac_misc.gid = inode->i_gid;
73 hmac_misc.mode = inode->i_mode;
74 sg_init_one(sg, &hmac_misc, sizeof hmac_misc);
75 crypto_hash_update(desc, sg, sizeof hmac_misc);
76 crypto_hash_final(desc, digest);
77}
78
79/*
80 * Calculate the HMAC value across the set of protected security xattrs.
81 *
82 * Instead of retrieving the requested xattr, for performance, calculate
83 * the hmac using the requested xattr value. Don't alloc/free memory for
84 * each xattr, but attempt to re-use the previously allocated memory.
85 */
86int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
87 const char *req_xattr_value, size_t req_xattr_value_len,
88 char *digest)
89{
90 struct inode *inode = dentry->d_inode;
91 struct hash_desc desc;
92 struct scatterlist sg[1];
93 char **xattrname;
94 size_t xattr_size = 0;
95 char *xattr_value = NULL;
96 int error;
97 int size;
98
99 if (!inode->i_op || !inode->i_op->getxattr)
100 return -EOPNOTSUPP;
101 error = init_desc(&desc);
102 if (error)
103 return error;
104
105 error = -ENODATA;
106 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
107 if ((req_xattr_name && req_xattr_value)
108 && !strcmp(*xattrname, req_xattr_name)) {
109 error = 0;
110 sg_init_one(sg, req_xattr_value, req_xattr_value_len);
111 crypto_hash_update(&desc, sg, req_xattr_value_len);
112 continue;
113 }
114 size = vfs_getxattr_alloc(dentry, *xattrname,
115 &xattr_value, xattr_size, GFP_NOFS);
116 if (size == -ENOMEM) {
117 error = -ENOMEM;
118 goto out;
119 }
120 if (size < 0)
121 continue;
122
123 error = 0;
124 xattr_size = size;
125 sg_init_one(sg, xattr_value, xattr_size);
126 crypto_hash_update(&desc, sg, xattr_size);
127 }
128 hmac_add_misc(&desc, inode, digest);
129 kfree(xattr_value);
130out:
131 crypto_free_hash(desc.tfm);
132 return error;
133}
134
135/*
136 * Calculate the hmac and update security.evm xattr
137 *
138 * Expects to be called with i_mutex locked.
139 */
140int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
141 const char *xattr_value, size_t xattr_value_len)
142{
143 struct inode *inode = dentry->d_inode;
144 u8 hmac[SHA1_DIGEST_SIZE];
145 int rc = 0;
146
147 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
148 xattr_value_len, hmac);
149 if (rc == 0)
150 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
151 hmac, SHA1_DIGEST_SIZE, 0);
152 else if (rc == -ENODATA)
153 rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
154 return rc;
155}
156
157/*
158 * Get the key from the TPM for the SHA1-HMAC
159 */
160int evm_init_key(void)
161{
162 struct key *evm_key;
163 struct encrypted_key_payload *ekp;
164 int rc = 0;
165
166 evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
167 if (IS_ERR(evm_key))
168 return -ENOENT;
169
170 down_read(&evm_key->sem);
171 ekp = evm_key->payload.data;
172 if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
173 rc = -EINVAL;
174 goto out;
175 }
176 memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
177out:
178 /* burn the original key contents */
179 memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
180 up_read(&evm_key->sem);
181 key_put(evm_key);
182 return rc;
183}
generated by cgit v1.2.2 (git 2.25.0) at 2025-04-25 03:47:06 -0400