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;
30 static struct shash_desc *init_desc(void)
33 struct shash_desc *desc;
35 if (hmac_tfm == NULL) {
36 hmac_tfm = crypto_alloc_shash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
37 if (IS_ERR(hmac_tfm)) {
38 pr_err("Can not allocate %s (reason: %ld)\n",
39 evm_hmac, PTR_ERR(hmac_tfm));
40 rc = PTR_ERR(hmac_tfm);
46 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(hmac_tfm),
49 return ERR_PTR(-ENOMEM);
52 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
54 rc = crypto_shash_setkey(hmac_tfm, evmkey, evmkey_len);
57 rc = crypto_shash_init(desc);
66 /* Protect against 'cutting & pasting' security.evm xattr, include inode
69 * (Additional directory/file metadata needs to be added for more complete
72 static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
83 memset(&hmac_misc, 0, sizeof hmac_misc);
84 hmac_misc.ino = inode->i_ino;
85 hmac_misc.generation = inode->i_generation;
86 hmac_misc.uid = inode->i_uid;
87 hmac_misc.gid = inode->i_gid;
88 hmac_misc.mode = inode->i_mode;
89 crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof hmac_misc);
90 crypto_shash_final(desc, digest);
94 * Calculate the HMAC value across the set of protected security xattrs.
96 * Instead of retrieving the requested xattr, for performance, calculate
97 * the hmac using the requested xattr value. Don't alloc/free memory for
98 * each xattr, but attempt to re-use the previously allocated memory.
100 int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
101 const char *req_xattr_value, size_t req_xattr_value_len,
104 struct inode *inode = dentry->d_inode;
105 struct shash_desc *desc;
107 size_t xattr_size = 0;
108 char *xattr_value = NULL;
112 if (!inode->i_op || !inode->i_op->getxattr)
116 return PTR_ERR(desc);
119 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
120 if ((req_xattr_name && req_xattr_value)
121 && !strcmp(*xattrname, req_xattr_name)) {
123 crypto_shash_update(desc, (const u8 *)req_xattr_value,
124 req_xattr_value_len);
127 size = vfs_getxattr_alloc(dentry, *xattrname,
128 &xattr_value, xattr_size, GFP_NOFS);
129 if (size == -ENOMEM) {
138 crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
140 hmac_add_misc(desc, inode, digest);
149 * Calculate the hmac and update security.evm xattr
151 * Expects to be called with i_mutex locked.
153 int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
154 const char *xattr_value, size_t xattr_value_len)
156 struct inode *inode = dentry->d_inode;
157 struct evm_ima_xattr_data xattr_data;
160 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
161 xattr_value_len, xattr_data.digest);
163 xattr_data.type = EVM_XATTR_HMAC;
164 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
166 sizeof(xattr_data), 0);
168 else if (rc == -ENODATA)
169 rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
173 int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
176 struct shash_desc *desc;
180 printk(KERN_INFO "init_desc failed\n");
181 return PTR_ERR(desc);
184 crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
185 hmac_add_misc(desc, inode, hmac_val);
191 * Get the key from the TPM for the SHA1-HMAC
193 int evm_init_key(void)
196 struct encrypted_key_payload *ekp;
199 evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
203 down_read(&evm_key->sem);
204 ekp = evm_key->payload.data;
205 if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
209 memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
211 /* burn the original key contents */
212 memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
213 up_read(&evm_key->sem);