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);
93 if (IS_ERR_OR_NULL(*tfm)) {
97 *tfm = crypto_alloc_shash(algo, 0,
98 CRYPTO_ALG_ASYNC | CRYPTO_NOLOAD);
101 pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
103 mutex_unlock(&mutex);
106 if (type == EVM_XATTR_HMAC) {
107 rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
109 crypto_free_shash(*tfm);
111 mutex_unlock(&mutex);
116 mutex_unlock(&mutex);
119 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
122 return ERR_PTR(-ENOMEM);
125 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
127 rc = crypto_shash_init(desc);
135 /* Protect against 'cutting & pasting' security.evm xattr, include inode
138 * (Additional directory/file metadata needs to be added for more complete
141 static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
142 char type, char *digest)
152 memset(&hmac_misc, 0, sizeof(hmac_misc));
153 /* Don't include the inode or generation number in portable
156 if (type != EVM_XATTR_PORTABLE_DIGSIG) {
157 hmac_misc.ino = inode->i_ino;
158 hmac_misc.generation = inode->i_generation;
160 /* The hmac uid and gid must be encoded in the initial user
161 * namespace (not the filesystems user namespace) as encoding
162 * them in the filesystems user namespace allows an attack
163 * where first they are written in an unprivileged fuse mount
164 * of a filesystem and then the system is tricked to mount the
165 * filesystem for real on next boot and trust it because
166 * everything is signed.
168 hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
169 hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
170 hmac_misc.mode = inode->i_mode;
171 crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
172 if ((evm_hmac_attrs & EVM_ATTR_FSUUID) &&
173 type != EVM_XATTR_PORTABLE_DIGSIG)
174 crypto_shash_update(desc, &inode->i_sb->s_uuid.b[0],
175 sizeof(inode->i_sb->s_uuid));
176 crypto_shash_final(desc, digest);
180 * Calculate the HMAC value across the set of protected security xattrs.
182 * Instead of retrieving the requested xattr, for performance, calculate
183 * the hmac using the requested xattr value. Don't alloc/free memory for
184 * each xattr, but attempt to re-use the previously allocated memory.
186 static int evm_calc_hmac_or_hash(struct dentry *dentry,
187 const char *req_xattr_name,
188 const char *req_xattr_value,
189 size_t req_xattr_value_len,
190 char type, char *digest)
192 struct inode *inode = d_backing_inode(dentry);
193 struct shash_desc *desc;
195 size_t xattr_size = 0;
196 char *xattr_value = NULL;
199 bool ima_present = false;
201 if (!(inode->i_opflags & IOP_XATTR))
204 desc = init_desc(type);
206 return PTR_ERR(desc);
209 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
212 if (strcmp(*xattrname, XATTR_NAME_IMA) == 0)
215 if ((req_xattr_name && req_xattr_value)
216 && !strcmp(*xattrname, req_xattr_name)) {
218 crypto_shash_update(desc, (const u8 *)req_xattr_value,
219 req_xattr_value_len);
224 size = vfs_getxattr_alloc(dentry, *xattrname,
225 &xattr_value, xattr_size, GFP_NOFS);
226 if (size == -ENOMEM) {
235 crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
239 hmac_add_misc(desc, inode, type, digest);
241 /* Portable EVM signatures must include an IMA hash */
242 if (type == EVM_XATTR_PORTABLE_DIGSIG && !ima_present)
250 int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
251 const char *req_xattr_value, size_t req_xattr_value_len,
254 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
255 req_xattr_value_len, EVM_XATTR_HMAC, digest);
258 int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
259 const char *req_xattr_value, size_t req_xattr_value_len,
260 char type, char *digest)
262 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
263 req_xattr_value_len, type, digest);
266 static int evm_is_immutable(struct dentry *dentry, struct inode *inode)
268 const struct evm_ima_xattr_data *xattr_data = NULL;
269 struct integrity_iint_cache *iint;
272 iint = integrity_iint_find(inode);
273 if (iint && (iint->flags & EVM_IMMUTABLE_DIGSIG))
276 /* Do this the hard way */
277 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
284 if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG)
295 * Calculate the hmac and update security.evm xattr
297 * Expects to be called with i_mutex locked.
299 int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
300 const char *xattr_value, size_t xattr_value_len)
302 struct inode *inode = d_backing_inode(dentry);
303 struct evm_ima_xattr_data xattr_data;
307 * Don't permit any transformation of the EVM xattr if the signature
308 * is of an immutable type
310 rc = evm_is_immutable(dentry, inode);
316 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
317 xattr_value_len, xattr_data.digest);
319 xattr_data.type = EVM_XATTR_HMAC;
320 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
322 sizeof(xattr_data), 0);
323 } else if (rc == -ENODATA && (inode->i_opflags & IOP_XATTR)) {
324 rc = __vfs_removexattr(dentry, XATTR_NAME_EVM);
329 int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
332 struct shash_desc *desc;
334 desc = init_desc(EVM_XATTR_HMAC);
336 pr_info("init_desc failed\n");
337 return PTR_ERR(desc);
340 crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
341 hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val);
347 * Get the key from the TPM for the SHA1-HMAC
349 int evm_init_key(void)
352 struct encrypted_key_payload *ekp;
355 evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
359 down_read(&evm_key->sem);
360 ekp = evm_key->payload.data[0];
362 rc = evm_set_key(ekp->decrypted_data, ekp->decrypted_datalen);
364 /* burn the original key contents */
365 memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
366 up_read(&evm_key->sem);