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 DEFINE_MUTEX(mutex);
33 static struct shash_desc *init_desc(char type)
37 struct crypto_shash **tfm;
38 struct shash_desc *desc;
40 if (type == EVM_XATTR_HMAC) {
52 *tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);
55 pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
60 if (type == EVM_XATTR_HMAC) {
61 rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
63 crypto_free_shash(*tfm);
73 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
76 return ERR_PTR(-ENOMEM);
79 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
81 rc = crypto_shash_init(desc);
89 /* Protect against 'cutting & pasting' security.evm xattr, include inode
92 * (Additional directory/file metadata needs to be added for more complete
95 static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
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 crypto_shash_final(desc, digest);
117 * Calculate the HMAC value across the set of protected security xattrs.
119 * Instead of retrieving the requested xattr, for performance, calculate
120 * the hmac using the requested xattr value. Don't alloc/free memory for
121 * each xattr, but attempt to re-use the previously allocated memory.
123 static int evm_calc_hmac_or_hash(struct dentry *dentry,
124 const char *req_xattr_name,
125 const char *req_xattr_value,
126 size_t req_xattr_value_len,
127 char type, char *digest)
129 struct inode *inode = dentry->d_inode;
130 struct shash_desc *desc;
132 size_t xattr_size = 0;
133 char *xattr_value = NULL;
137 if (!inode->i_op || !inode->i_op->getxattr)
139 desc = init_desc(type);
141 return PTR_ERR(desc);
144 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
145 if ((req_xattr_name && req_xattr_value)
146 && !strcmp(*xattrname, req_xattr_name)) {
148 crypto_shash_update(desc, (const u8 *)req_xattr_value,
149 req_xattr_value_len);
152 size = vfs_getxattr_alloc(dentry, *xattrname,
153 &xattr_value, xattr_size, GFP_NOFS);
154 if (size == -ENOMEM) {
163 crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
165 hmac_add_misc(desc, inode, digest);
173 int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
174 const char *req_xattr_value, size_t req_xattr_value_len,
177 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
178 req_xattr_value_len, EVM_XATTR_HMAC, digest);
181 int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
182 const char *req_xattr_value, size_t req_xattr_value_len,
185 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
186 req_xattr_value_len, IMA_XATTR_DIGEST, digest);
190 * Calculate the hmac and update security.evm xattr
192 * Expects to be called with i_mutex locked.
194 int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
195 const char *xattr_value, size_t xattr_value_len)
197 struct inode *inode = dentry->d_inode;
198 struct evm_ima_xattr_data xattr_data;
201 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
202 xattr_value_len, xattr_data.digest);
204 xattr_data.type = EVM_XATTR_HMAC;
205 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
207 sizeof(xattr_data), 0);
208 } else if (rc == -ENODATA && inode->i_op->removexattr) {
209 rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
214 int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
217 struct shash_desc *desc;
219 desc = init_desc(EVM_XATTR_HMAC);
221 printk(KERN_INFO "init_desc failed\n");
222 return PTR_ERR(desc);
225 crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
226 hmac_add_misc(desc, inode, hmac_val);
232 * Get the key from the TPM for the SHA1-HMAC
234 int evm_init_key(void)
237 struct encrypted_key_payload *ekp;
240 evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
244 down_read(&evm_key->sem);
245 ekp = evm_key->payload.data;
246 if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
250 memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
252 /* burn the original key contents */
253 memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
254 up_read(&evm_key->sem);