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 #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>
23 #define EVMKEY "evm-key"
24 #define MAX_KEY_SIZE 128
25 static unsigned char evmkey[MAX_KEY_SIZE];
26 static int evmkey_len = MAX_KEY_SIZE;
28 struct crypto_shash *hmac_tfm;
29 struct crypto_shash *hash_tfm;
31 static struct shash_desc *init_desc(const char type)
35 struct crypto_shash **tfm;
36 struct shash_desc *desc;
38 if (type == EVM_XATTR_HMAC) {
47 *tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);
49 pr_err("Can not allocate %s (reason: %ld)\n",
57 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
60 return ERR_PTR(-ENOMEM);
63 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
65 if (type == EVM_XATTR_HMAC) {
66 rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
71 rc = crypto_shash_init(desc);
80 /* Protect against 'cutting & pasting' security.evm xattr, include inode
83 * (Additional directory/file metadata needs to be added for more complete
86 static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
97 memset(&hmac_misc, 0, sizeof hmac_misc);
98 hmac_misc.ino = inode->i_ino;
99 hmac_misc.generation = inode->i_generation;
100 hmac_misc.uid = inode->i_uid;
101 hmac_misc.gid = inode->i_gid;
102 hmac_misc.mode = inode->i_mode;
103 crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof hmac_misc);
104 crypto_shash_final(desc, digest);
108 * Calculate the HMAC value across the set of protected security xattrs.
110 * Instead of retrieving the requested xattr, for performance, calculate
111 * the hmac using the requested xattr value. Don't alloc/free memory for
112 * each xattr, but attempt to re-use the previously allocated memory.
114 static int evm_calc_hmac_or_hash(struct dentry *dentry,
115 const char *req_xattr_name,
116 const char *req_xattr_value,
117 size_t req_xattr_value_len,
118 char type, char *digest)
120 struct inode *inode = dentry->d_inode;
121 struct shash_desc *desc;
123 size_t xattr_size = 0;
124 char *xattr_value = NULL;
128 if (!inode->i_op || !inode->i_op->getxattr)
130 desc = init_desc(type);
132 return PTR_ERR(desc);
135 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
136 if ((req_xattr_name && req_xattr_value)
137 && !strcmp(*xattrname, req_xattr_name)) {
139 crypto_shash_update(desc, (const u8 *)req_xattr_value,
140 req_xattr_value_len);
143 size = vfs_getxattr_alloc(dentry, *xattrname,
144 &xattr_value, xattr_size, GFP_NOFS);
145 if (size == -ENOMEM) {
154 crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
156 hmac_add_misc(desc, inode, digest);
164 int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
165 const char *req_xattr_value, size_t req_xattr_value_len,
168 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
169 req_xattr_value_len, EVM_XATTR_HMAC, digest);
172 int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
173 const char *req_xattr_value, size_t req_xattr_value_len,
176 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
177 req_xattr_value_len, IMA_XATTR_DIGEST, digest);
181 * Calculate the hmac and update security.evm xattr
183 * Expects to be called with i_mutex locked.
185 int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
186 const char *xattr_value, size_t xattr_value_len)
188 struct inode *inode = dentry->d_inode;
189 struct evm_ima_xattr_data xattr_data;
192 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
193 xattr_value_len, xattr_data.digest);
195 xattr_data.type = EVM_XATTR_HMAC;
196 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
198 sizeof(xattr_data), 0);
200 else if (rc == -ENODATA)
201 rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
205 int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
208 struct shash_desc *desc;
210 desc = init_desc(EVM_XATTR_HMAC);
212 printk(KERN_INFO "init_desc failed\n");
213 return PTR_ERR(desc);
216 crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
217 hmac_add_misc(desc, inode, hmac_val);
223 * Get the key from the TPM for the SHA1-HMAC
225 int evm_init_key(void)
228 struct encrypted_key_payload *ekp;
231 evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
235 down_read(&evm_key->sem);
236 ekp = evm_key->payload.data;
237 if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
241 memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
243 /* burn the original key contents */
244 memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
245 up_read(&evm_key->sem);