tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 <keys/encrypted-type.h>
20#include <crypto/hash.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
28struct crypto_shash *hmac_tfm;
29struct crypto_shash *hash_tfm;
30
31static DEFINE_MUTEX(mutex);
32
33static struct shash_desc *init_desc(char type)
34{
35 long rc;
36 char *algo;
37 struct crypto_shash **tfm;
38 struct shash_desc *desc;
39
40 if (type == EVM_XATTR_HMAC) {
41 tfm = &hmac_tfm;
42 algo = evm_hmac;
43 } else {
44 tfm = &hash_tfm;
45 algo = evm_hash;
46 }
47
48 if (*tfm == NULL) {
49 mutex_lock(&mutex);
50 if (*tfm)
51 goto out;
52 *tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);
53 if (IS_ERR(*tfm)) {
54 rc = PTR_ERR(*tfm);
55 pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
56 *tfm = NULL;
57 mutex_unlock(&mutex);
58 return ERR_PTR(rc);
59 }
60 if (type == EVM_XATTR_HMAC) {
61 rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
62 if (rc) {
63 crypto_free_shash(*tfm);
64 *tfm = NULL;
65 mutex_unlock(&mutex);
66 return ERR_PTR(rc);
67 }
68 }
69out:
70 mutex_unlock(&mutex);
71 }
72
73 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
74 GFP_KERNEL);
75 if (!desc)
76 return ERR_PTR(-ENOMEM);
77
78 desc->tfm = *tfm;
79 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
80
81 rc = crypto_shash_init(desc);
82 if (rc) {
83 kfree(desc);
84 return ERR_PTR(rc);
85 }
86 return desc;
87}
88
89/* Protect against 'cutting & pasting' security.evm xattr, include inode
90 * specific info.
91 *
92 * (Additional directory/file metadata needs to be added for more complete
93 * protection.)
94 */
95static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
96 char *digest)
97{
98 struct h_misc {
99 unsigned long ino;
100 __u32 generation;
101 uid_t uid;
102 gid_t gid;
103 umode_t mode;
104 } hmac_misc;
105
106 memset(&hmac_misc, 0, sizeof hmac_misc);
107 hmac_misc.ino = inode->i_ino;
108 hmac_misc.generation = inode->i_generation;
109 hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
110 hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
111 hmac_misc.mode = inode->i_mode;
112 crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof hmac_misc);
113 if (evm_hmac_version > 1)
114 crypto_shash_update(desc, inode->i_sb->s_uuid,
115 sizeof(inode->i_sb->s_uuid));
116 crypto_shash_final(desc, digest);
117}
118
119/*
120 * Calculate the HMAC value across the set of protected security xattrs.
121 *
122 * Instead of retrieving the requested xattr, for performance, calculate
123 * the hmac using the requested xattr value. Don't alloc/free memory for
124 * each xattr, but attempt to re-use the previously allocated memory.
125 */
126static int evm_calc_hmac_or_hash(struct dentry *dentry,
127 const char *req_xattr_name,
128 const char *req_xattr_value,
129 size_t req_xattr_value_len,
130 char type, char *digest)
131{
132 struct inode *inode = dentry->d_inode;
133 struct shash_desc *desc;
134 char **xattrname;
135 size_t xattr_size = 0;
136 char *xattr_value = NULL;
137 int error;
138 int size;
139
140 if (!inode->i_op || !inode->i_op->getxattr)
141 return -EOPNOTSUPP;
142 desc = init_desc(type);
143 if (IS_ERR(desc))
144 return PTR_ERR(desc);
145
146 error = -ENODATA;
147 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
148 if ((req_xattr_name && req_xattr_value)
149 && !strcmp(*xattrname, req_xattr_name)) {
150 error = 0;
151 crypto_shash_update(desc, (const u8 *)req_xattr_value,
152 req_xattr_value_len);
153 continue;
154 }
155 size = vfs_getxattr_alloc(dentry, *xattrname,
156 &xattr_value, xattr_size, GFP_NOFS);
157 if (size == -ENOMEM) {
158 error = -ENOMEM;
159 goto out;
160 }
161 if (size < 0)
162 continue;
163
164 error = 0;
165 xattr_size = size;
166 crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
167 }
168 hmac_add_misc(desc, inode, digest);
169
170out:
171 kfree(xattr_value);
172 kfree(desc);
173 return error;
174}
175
176int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
177 const char *req_xattr_value, size_t req_xattr_value_len,
178 char *digest)
179{
180 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
181 req_xattr_value_len, EVM_XATTR_HMAC, digest);
182}
183
184int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
185 const char *req_xattr_value, size_t req_xattr_value_len,
186 char *digest)
187{
188 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
189 req_xattr_value_len, IMA_XATTR_DIGEST, digest);
190}
191
192/*
193 * Calculate the hmac and update security.evm xattr
194 *
195 * Expects to be called with i_mutex locked.
196 */
197int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
198 const char *xattr_value, size_t xattr_value_len)
199{
200 struct inode *inode = dentry->d_inode;
201 struct evm_ima_xattr_data xattr_data;
202 int rc = 0;
203
204 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
205 xattr_value_len, xattr_data.digest);
206 if (rc == 0) {
207 xattr_data.type = EVM_XATTR_HMAC;
208 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
209 &xattr_data,
210 sizeof(xattr_data), 0);
211 } else if (rc == -ENODATA && inode->i_op->removexattr) {
212 rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
213 }
214 return rc;
215}
216
217int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
218 char *hmac_val)
219{
220 struct shash_desc *desc;
221
222 desc = init_desc(EVM_XATTR_HMAC);
223 if (IS_ERR(desc)) {
224 printk(KERN_INFO "init_desc failed\n");
225 return PTR_ERR(desc);
226 }
227
228 crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
229 hmac_add_misc(desc, inode, hmac_val);
230 kfree(desc);
231 return 0;
232}
233
234/*
235 * Get the key from the TPM for the SHA1-HMAC
236 */
237int evm_init_key(void)
238{
239 struct key *evm_key;
240 struct encrypted_key_payload *ekp;
241 int rc = 0;
242
243 evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
244 if (IS_ERR(evm_key))
245 return -ENOENT;
246
247 down_read(&evm_key->sem);
248 ekp = evm_key->payload.data;
249 if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
250 rc = -EINVAL;
251 goto out;
252 }
253 memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
254out:
255 /* burn the original key contents */
256 memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
257 up_read(&evm_key->sem);
258 key_put(evm_key);
259 return rc;
260}