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 <keys/encrypted-type.h>
22 #include <crypto/hash.h>
25 #define EVMKEY "evm-key"
26 #define MAX_KEY_SIZE 128
27 static unsigned char evmkey[MAX_KEY_SIZE];
28 static int evmkey_len = MAX_KEY_SIZE;
30 struct crypto_shash *hmac_tfm;
31 struct crypto_shash *hash_tfm;
33 static DEFINE_MUTEX(mutex);
35 static struct shash_desc *init_desc(char type)
39 struct crypto_shash **tfm;
40 struct shash_desc *desc;
42 if (type == EVM_XATTR_HMAC) {
54 *tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);
57 pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
62 if (type == EVM_XATTR_HMAC) {
63 rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
65 crypto_free_shash(*tfm);
75 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
78 return ERR_PTR(-ENOMEM);
81 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
83 rc = crypto_shash_init(desc);
91 /* Protect against 'cutting & pasting' security.evm xattr, include inode
94 * (Additional directory/file metadata needs to be added for more complete
97 static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
108 memset(&hmac_misc, 0, sizeof(hmac_misc));
109 hmac_misc.ino = inode->i_ino;
110 hmac_misc.generation = inode->i_generation;
111 hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
112 hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
113 hmac_misc.mode = inode->i_mode;
114 crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
115 if (evm_hmac_attrs & EVM_ATTR_FSUUID)
116 crypto_shash_update(desc, inode->i_sb->s_uuid,
117 sizeof(inode->i_sb->s_uuid));
118 crypto_shash_final(desc, digest);
122 * Calculate the HMAC value across the set of protected security xattrs.
124 * Instead of retrieving the requested xattr, for performance, calculate
125 * the hmac using the requested xattr value. Don't alloc/free memory for
126 * each xattr, but attempt to re-use the previously allocated memory.
128 static int evm_calc_hmac_or_hash(struct dentry *dentry,
129 const char *req_xattr_name,
130 const char *req_xattr_value,
131 size_t req_xattr_value_len,
132 char type, char *digest)
134 struct inode *inode = d_backing_inode(dentry);
135 struct shash_desc *desc;
137 size_t xattr_size = 0;
138 char *xattr_value = NULL;
142 if (!inode->i_op->getxattr)
144 desc = init_desc(type);
146 return PTR_ERR(desc);
149 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
150 if ((req_xattr_name && req_xattr_value)
151 && !strcmp(*xattrname, req_xattr_name)) {
153 crypto_shash_update(desc, (const u8 *)req_xattr_value,
154 req_xattr_value_len);
157 size = vfs_getxattr_alloc(dentry, *xattrname,
158 &xattr_value, xattr_size, GFP_NOFS);
159 if (size == -ENOMEM) {
168 crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
170 hmac_add_misc(desc, inode, digest);
178 int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
179 const char *req_xattr_value, size_t req_xattr_value_len,
182 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
183 req_xattr_value_len, EVM_XATTR_HMAC, digest);
186 int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
187 const char *req_xattr_value, size_t req_xattr_value_len,
190 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
191 req_xattr_value_len, IMA_XATTR_DIGEST, digest);
195 * Calculate the hmac and update security.evm xattr
197 * Expects to be called with i_mutex locked.
199 int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
200 const char *xattr_value, size_t xattr_value_len)
202 struct inode *inode = d_backing_inode(dentry);
203 struct evm_ima_xattr_data xattr_data;
206 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
207 xattr_value_len, xattr_data.digest);
209 xattr_data.type = EVM_XATTR_HMAC;
210 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
212 sizeof(xattr_data), 0);
213 } else if (rc == -ENODATA && inode->i_op->removexattr) {
214 rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
219 int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
222 struct shash_desc *desc;
224 desc = init_desc(EVM_XATTR_HMAC);
226 pr_info("init_desc failed\n");
227 return PTR_ERR(desc);
230 crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
231 hmac_add_misc(desc, inode, hmac_val);
237 * Get the key from the TPM for the SHA1-HMAC
239 int evm_init_key(void)
242 struct encrypted_key_payload *ekp;
245 evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
249 down_read(&evm_key->sem);
250 ekp = evm_key->payload.data;
251 if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
255 memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
257 /* burn the original key contents */
258 memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
259 up_read(&evm_key->sem);