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 if (evm_hmac_version > 1)
114 crypto_shash_update(desc, inode->i_sb->s_uuid,
115 sizeof(inode->i_sb->s_uuid));
116 crypto_shash_final(desc, digest);
120 * Calculate the HMAC value across the set of protected security xattrs.
122 * Instead of retrieving the requested xattr, for performance, calculate
123 * the hmac using the requested xattr value. Don't alloc/free memory for
124 * each xattr, but attempt to re-use the previously allocated memory.
126 static int evm_calc_hmac_or_hash(struct dentry *dentry,
127 const char *req_xattr_name,
128 const char *req_xattr_value,
129 size_t req_xattr_value_len,
130 char type, char *digest)
132 struct inode *inode = dentry->d_inode;
133 struct shash_desc *desc;
135 size_t xattr_size = 0;
136 char *xattr_value = NULL;
140 if (!inode->i_op || !inode->i_op->getxattr)
142 desc = init_desc(type);
144 return PTR_ERR(desc);
147 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
148 if ((req_xattr_name && req_xattr_value)
149 && !strcmp(*xattrname, req_xattr_name)) {
151 crypto_shash_update(desc, (const u8 *)req_xattr_value,
152 req_xattr_value_len);
155 size = vfs_getxattr_alloc(dentry, *xattrname,
156 &xattr_value, xattr_size, GFP_NOFS);
157 if (size == -ENOMEM) {
166 crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
168 hmac_add_misc(desc, inode, digest);
176 int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
177 const char *req_xattr_value, size_t req_xattr_value_len,
180 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
181 req_xattr_value_len, EVM_XATTR_HMAC, digest);
184 int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
185 const char *req_xattr_value, size_t req_xattr_value_len,
188 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
189 req_xattr_value_len, IMA_XATTR_DIGEST, digest);
193 * Calculate the hmac and update security.evm xattr
195 * Expects to be called with i_mutex locked.
197 int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
198 const char *xattr_value, size_t xattr_value_len)
200 struct inode *inode = dentry->d_inode;
201 struct evm_ima_xattr_data xattr_data;
204 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
205 xattr_value_len, xattr_data.digest);
207 xattr_data.type = EVM_XATTR_HMAC;
208 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
210 sizeof(xattr_data), 0);
211 } else if (rc == -ENODATA && inode->i_op->removexattr) {
212 rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
217 int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
220 struct shash_desc *desc;
222 desc = init_desc(EVM_XATTR_HMAC);
224 printk(KERN_INFO "init_desc failed\n");
225 return PTR_ERR(desc);
228 crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
229 hmac_add_misc(desc, inode, hmac_val);
235 * Get the key from the TPM for the SHA1-HMAC
237 int evm_init_key(void)
240 struct encrypted_key_payload *ekp;
243 evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
247 down_read(&evm_key->sem);
248 ekp = evm_key->payload.data;
249 if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
253 memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
255 /* burn the original key contents */
256 memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
257 up_read(&evm_key->sem);