2 * Copyright (C) 2005-2010 IBM Corporation
5 * Mimi Zohar <zohar@us.ibm.com>
6 * Kylene Hall <kjhall@us.ibm.com>
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.
13 * Using root's kernel master key (kmk), calculate the HMAC
16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18 #include <linux/module.h>
19 #include <linux/crypto.h>
20 #include <linux/xattr.h>
21 #include <linux/evm.h>
22 #include <keys/encrypted-type.h>
23 #include <crypto/hash.h>
26 #define EVMKEY "evm-key"
27 #define MAX_KEY_SIZE 128
28 static unsigned char evmkey[MAX_KEY_SIZE];
29 static int evmkey_len = MAX_KEY_SIZE;
31 struct crypto_shash *hmac_tfm;
32 struct crypto_shash *hash_tfm;
34 static DEFINE_MUTEX(mutex);
36 #define EVM_SET_KEY_BUSY 0
38 static unsigned long evm_set_key_flags;
41 * evm_set_key() - set EVM HMAC key from the kernel
42 * @key: pointer to a buffer with the key data
43 * @size: length of the key data
45 * This function allows setting the EVM HMAC key from the kernel
46 * without using the "encrypted" key subsystem keys. It can be used
47 * by the crypto HW kernel module which has its own way of managing
50 * key length should be between 32 and 128 bytes long
52 int evm_set_key(void *key, size_t keylen)
57 if (test_and_set_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags))
60 if (keylen > MAX_KEY_SIZE)
62 memcpy(evmkey, key, keylen);
63 evm_initialized |= EVM_INIT_HMAC;
64 pr_info("key initialized\n");
67 clear_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags);
69 pr_err("key initialization failed\n");
72 EXPORT_SYMBOL_GPL(evm_set_key);
74 static struct shash_desc *init_desc(char type)
78 struct crypto_shash **tfm;
79 struct shash_desc *desc;
81 if (type == EVM_XATTR_HMAC) {
82 if (!(evm_initialized & EVM_INIT_HMAC)) {
83 pr_err("HMAC key is not set\n");
84 return ERR_PTR(-ENOKEY);
97 *tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);
100 pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
102 mutex_unlock(&mutex);
105 if (type == EVM_XATTR_HMAC) {
106 rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
108 crypto_free_shash(*tfm);
110 mutex_unlock(&mutex);
115 mutex_unlock(&mutex);
118 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
121 return ERR_PTR(-ENOMEM);
124 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
126 rc = crypto_shash_init(desc);
134 /* Protect against 'cutting & pasting' security.evm xattr, include inode
137 * (Additional directory/file metadata needs to be added for more complete
140 static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
151 memset(&hmac_misc, 0, sizeof(hmac_misc));
152 hmac_misc.ino = inode->i_ino;
153 hmac_misc.generation = inode->i_generation;
154 hmac_misc.uid = from_kuid(inode->i_sb->s_user_ns, inode->i_uid);
155 hmac_misc.gid = from_kgid(inode->i_sb->s_user_ns, inode->i_gid);
156 hmac_misc.mode = inode->i_mode;
157 crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
158 if (evm_hmac_attrs & EVM_ATTR_FSUUID)
159 crypto_shash_update(desc, inode->i_sb->s_uuid,
160 sizeof(inode->i_sb->s_uuid));
161 crypto_shash_final(desc, digest);
165 * Calculate the HMAC value across the set of protected security xattrs.
167 * Instead of retrieving the requested xattr, for performance, calculate
168 * the hmac using the requested xattr value. Don't alloc/free memory for
169 * each xattr, but attempt to re-use the previously allocated memory.
171 static int evm_calc_hmac_or_hash(struct dentry *dentry,
172 const char *req_xattr_name,
173 const char *req_xattr_value,
174 size_t req_xattr_value_len,
175 char type, char *digest)
177 struct inode *inode = d_backing_inode(dentry);
178 struct shash_desc *desc;
180 size_t xattr_size = 0;
181 char *xattr_value = NULL;
185 if (!inode->i_op->getxattr)
187 desc = init_desc(type);
189 return PTR_ERR(desc);
192 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
193 if ((req_xattr_name && req_xattr_value)
194 && !strcmp(*xattrname, req_xattr_name)) {
196 crypto_shash_update(desc, (const u8 *)req_xattr_value,
197 req_xattr_value_len);
200 size = vfs_getxattr_alloc(dentry, *xattrname,
201 &xattr_value, xattr_size, GFP_NOFS);
202 if (size == -ENOMEM) {
211 crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
213 hmac_add_misc(desc, inode, digest);
221 int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
222 const char *req_xattr_value, size_t req_xattr_value_len,
225 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
226 req_xattr_value_len, EVM_XATTR_HMAC, digest);
229 int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
230 const char *req_xattr_value, size_t req_xattr_value_len,
233 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
234 req_xattr_value_len, IMA_XATTR_DIGEST, digest);
238 * Calculate the hmac and update security.evm xattr
240 * Expects to be called with i_mutex locked.
242 int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
243 const char *xattr_value, size_t xattr_value_len)
245 struct inode *inode = d_backing_inode(dentry);
246 struct evm_ima_xattr_data xattr_data;
249 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
250 xattr_value_len, xattr_data.digest);
252 xattr_data.type = EVM_XATTR_HMAC;
253 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
255 sizeof(xattr_data), 0);
256 } else if (rc == -ENODATA && inode->i_op->removexattr) {
257 rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
262 int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
265 struct shash_desc *desc;
267 desc = init_desc(EVM_XATTR_HMAC);
269 pr_info("init_desc failed\n");
270 return PTR_ERR(desc);
273 crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
274 hmac_add_misc(desc, inode, hmac_val);
280 * Get the key from the TPM for the SHA1-HMAC
282 int evm_init_key(void)
285 struct encrypted_key_payload *ekp;
288 evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
292 down_read(&evm_key->sem);
293 ekp = evm_key->payload.data[0];
295 rc = evm_set_key(ekp->decrypted_data, ekp->decrypted_datalen);
297 /* burn the original key contents */
298 memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
299 up_read(&evm_key->sem);