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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2005-2010 IBM Corporation
4 *
5 * Authors:
6 * Mimi Zohar <zohar@us.ibm.com>
7 * Kylene Hall <kjhall@us.ibm.com>
8 *
9 * File: evm_crypto.c
10 * Using root's kernel master key (kmk), calculate the HMAC
11 */
12
13#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15#include <linux/export.h>
16#include <linux/crypto.h>
17#include <linux/xattr.h>
18#include <linux/evm.h>
19#include <keys/encrypted-type.h>
20#include <crypto/hash.h>
21#include <crypto/hash_info.h>
22#include "evm.h"
23
24#define EVMKEY "evm-key"
25#define MAX_KEY_SIZE 128
26static unsigned char evmkey[MAX_KEY_SIZE];
27static const int evmkey_len = MAX_KEY_SIZE;
28
29struct crypto_shash *hmac_tfm;
30static struct crypto_shash *evm_tfm[HASH_ALGO__LAST];
31
32static DEFINE_MUTEX(mutex);
33
34#define EVM_SET_KEY_BUSY 0
35
36static unsigned long evm_set_key_flags;
37
38static const char evm_hmac[] = "hmac(sha1)";
39
40/**
41 * evm_set_key() - set EVM HMAC key from the kernel
42 * @key: pointer to a buffer with the key data
43 * @size: length of the key data
44 *
45 * This function allows setting the EVM HMAC key from the kernel
46 * without using the "encrypted" key subsystem keys. It can be used
47 * by the crypto HW kernel module which has its own way of managing
48 * keys.
49 *
50 * key length should be between 32 and 128 bytes long
51 */
52int evm_set_key(void *key, size_t keylen)
53{
54 int rc;
55
56 rc = -EBUSY;
57 if (test_and_set_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags))
58 goto busy;
59 rc = -EINVAL;
60 if (keylen > MAX_KEY_SIZE)
61 goto inval;
62 memcpy(evmkey, key, keylen);
63 evm_initialized |= EVM_INIT_HMAC;
64 pr_info("key initialized\n");
65 return 0;
66inval:
67 clear_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags);
68busy:
69 pr_err("key initialization failed\n");
70 return rc;
71}
72EXPORT_SYMBOL_GPL(evm_set_key);
73
74static struct shash_desc *init_desc(char type, uint8_t hash_algo)
75{
76 long rc;
77 const char *algo;
78 struct crypto_shash **tfm;
79 struct shash_desc *desc;
80
81 if (type == EVM_XATTR_HMAC) {
82 if (!(evm_initialized & EVM_INIT_HMAC)) {
83 pr_err_once("HMAC key is not set\n");
84 return ERR_PTR(-ENOKEY);
85 }
86 tfm = &hmac_tfm;
87 algo = evm_hmac;
88 } else {
89 if (hash_algo >= HASH_ALGO__LAST)
90 return ERR_PTR(-EINVAL);
91
92 tfm = &evm_tfm[hash_algo];
93 algo = hash_algo_name[hash_algo];
94 }
95
96 if (*tfm == NULL) {
97 mutex_lock(&mutex);
98 if (*tfm)
99 goto out;
100 *tfm = crypto_alloc_shash(algo, 0, CRYPTO_NOLOAD);
101 if (IS_ERR(*tfm)) {
102 rc = PTR_ERR(*tfm);
103 pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
104 *tfm = NULL;
105 mutex_unlock(&mutex);
106 return ERR_PTR(rc);
107 }
108 if (type == EVM_XATTR_HMAC) {
109 rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
110 if (rc) {
111 crypto_free_shash(*tfm);
112 *tfm = NULL;
113 mutex_unlock(&mutex);
114 return ERR_PTR(rc);
115 }
116 }
117out:
118 mutex_unlock(&mutex);
119 }
120
121 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
122 GFP_KERNEL);
123 if (!desc)
124 return ERR_PTR(-ENOMEM);
125
126 desc->tfm = *tfm;
127
128 rc = crypto_shash_init(desc);
129 if (rc) {
130 kfree(desc);
131 return ERR_PTR(rc);
132 }
133 return desc;
134}
135
136/* Protect against 'cutting & pasting' security.evm xattr, include inode
137 * specific info.
138 *
139 * (Additional directory/file metadata needs to be added for more complete
140 * protection.)
141 */
142static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
143 char type, char *digest)
144{
145 struct h_misc {
146 unsigned long ino;
147 __u32 generation;
148 uid_t uid;
149 gid_t gid;
150 umode_t mode;
151 } hmac_misc;
152
153 memset(&hmac_misc, 0, sizeof(hmac_misc));
154 /* Don't include the inode or generation number in portable
155 * signatures
156 */
157 if (type != EVM_XATTR_PORTABLE_DIGSIG) {
158 hmac_misc.ino = inode->i_ino;
159 hmac_misc.generation = inode->i_generation;
160 }
161 /* The hmac uid and gid must be encoded in the initial user
162 * namespace (not the filesystems user namespace) as encoding
163 * them in the filesystems user namespace allows an attack
164 * where first they are written in an unprivileged fuse mount
165 * of a filesystem and then the system is tricked to mount the
166 * filesystem for real on next boot and trust it because
167 * everything is signed.
168 */
169 hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
170 hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
171 hmac_misc.mode = inode->i_mode;
172 crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
173 if ((evm_hmac_attrs & EVM_ATTR_FSUUID) &&
174 type != EVM_XATTR_PORTABLE_DIGSIG)
175 crypto_shash_update(desc, (u8 *)&inode->i_sb->s_uuid, UUID_SIZE);
176 crypto_shash_final(desc, digest);
177}
178
179/*
180 * Calculate the HMAC value across the set of protected security xattrs.
181 *
182 * Instead of retrieving the requested xattr, for performance, calculate
183 * the hmac using the requested xattr value. Don't alloc/free memory for
184 * each xattr, but attempt to re-use the previously allocated memory.
185 */
186static int evm_calc_hmac_or_hash(struct dentry *dentry,
187 const char *req_xattr_name,
188 const char *req_xattr_value,
189 size_t req_xattr_value_len,
190 uint8_t type, struct evm_digest *data)
191{
192 struct inode *inode = d_backing_inode(dentry);
193 struct xattr_list *xattr;
194 struct shash_desc *desc;
195 size_t xattr_size = 0;
196 char *xattr_value = NULL;
197 int error;
198 int size;
199 bool ima_present = false;
200
201 if (!(inode->i_opflags & IOP_XATTR) ||
202 inode->i_sb->s_user_ns != &init_user_ns)
203 return -EOPNOTSUPP;
204
205 desc = init_desc(type, data->hdr.algo);
206 if (IS_ERR(desc))
207 return PTR_ERR(desc);
208
209 data->hdr.length = crypto_shash_digestsize(desc->tfm);
210
211 error = -ENODATA;
212 list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
213 bool is_ima = false;
214
215 if (strcmp(xattr->name, XATTR_NAME_IMA) == 0)
216 is_ima = true;
217
218 if ((req_xattr_name && req_xattr_value)
219 && !strcmp(xattr->name, req_xattr_name)) {
220 error = 0;
221 crypto_shash_update(desc, (const u8 *)req_xattr_value,
222 req_xattr_value_len);
223 if (is_ima)
224 ima_present = true;
225 continue;
226 }
227 size = vfs_getxattr_alloc(dentry, xattr->name,
228 &xattr_value, xattr_size, GFP_NOFS);
229 if (size == -ENOMEM) {
230 error = -ENOMEM;
231 goto out;
232 }
233 if (size < 0)
234 continue;
235
236 error = 0;
237 xattr_size = size;
238 crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
239 if (is_ima)
240 ima_present = true;
241 }
242 hmac_add_misc(desc, inode, type, data->digest);
243
244 /* Portable EVM signatures must include an IMA hash */
245 if (type == EVM_XATTR_PORTABLE_DIGSIG && !ima_present)
246 return -EPERM;
247out:
248 kfree(xattr_value);
249 kfree(desc);
250 return error;
251}
252
253int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
254 const char *req_xattr_value, size_t req_xattr_value_len,
255 struct evm_digest *data)
256{
257 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
258 req_xattr_value_len, EVM_XATTR_HMAC, data);
259}
260
261int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
262 const char *req_xattr_value, size_t req_xattr_value_len,
263 char type, struct evm_digest *data)
264{
265 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
266 req_xattr_value_len, type, data);
267}
268
269static int evm_is_immutable(struct dentry *dentry, struct inode *inode)
270{
271 const struct evm_ima_xattr_data *xattr_data = NULL;
272 struct integrity_iint_cache *iint;
273 int rc = 0;
274
275 iint = integrity_iint_find(inode);
276 if (iint && (iint->flags & EVM_IMMUTABLE_DIGSIG))
277 return 1;
278
279 /* Do this the hard way */
280 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
281 GFP_NOFS);
282 if (rc <= 0) {
283 if (rc == -ENODATA)
284 return 0;
285 return rc;
286 }
287 if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG)
288 rc = 1;
289 else
290 rc = 0;
291
292 kfree(xattr_data);
293 return rc;
294}
295
296
297/*
298 * Calculate the hmac and update security.evm xattr
299 *
300 * Expects to be called with i_mutex locked.
301 */
302int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
303 const char *xattr_value, size_t xattr_value_len)
304{
305 struct inode *inode = d_backing_inode(dentry);
306 struct evm_digest data;
307 int rc = 0;
308
309 /*
310 * Don't permit any transformation of the EVM xattr if the signature
311 * is of an immutable type
312 */
313 rc = evm_is_immutable(dentry, inode);
314 if (rc < 0)
315 return rc;
316 if (rc)
317 return -EPERM;
318
319 data.hdr.algo = HASH_ALGO_SHA1;
320 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
321 xattr_value_len, &data);
322 if (rc == 0) {
323 data.hdr.xattr.sha1.type = EVM_XATTR_HMAC;
324 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
325 &data.hdr.xattr.data[1],
326 SHA1_DIGEST_SIZE + 1, 0);
327 } else if (rc == -ENODATA && (inode->i_opflags & IOP_XATTR)) {
328 rc = __vfs_removexattr(dentry, XATTR_NAME_EVM);
329 }
330 return rc;
331}
332
333int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
334 char *hmac_val)
335{
336 struct shash_desc *desc;
337
338 desc = init_desc(EVM_XATTR_HMAC, HASH_ALGO_SHA1);
339 if (IS_ERR(desc)) {
340 pr_info("init_desc failed\n");
341 return PTR_ERR(desc);
342 }
343
344 crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
345 hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val);
346 kfree(desc);
347 return 0;
348}
349
350/*
351 * Get the key from the TPM for the SHA1-HMAC
352 */
353int evm_init_key(void)
354{
355 struct key *evm_key;
356 struct encrypted_key_payload *ekp;
357 int rc;
358
359 evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
360 if (IS_ERR(evm_key))
361 return -ENOENT;
362
363 down_read(&evm_key->sem);
364 ekp = evm_key->payload.data[0];
365
366 rc = evm_set_key(ekp->decrypted_data, ekp->decrypted_datalen);
367
368 /* burn the original key contents */
369 memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
370 up_read(&evm_key->sem);
371 key_put(evm_key);
372 return rc;
373}
1/*
2 * Copyright (C) 2005-2010 IBM Corporation
3 *
4 * Authors:
5 * Mimi Zohar <zohar@us.ibm.com>
6 * Kylene Hall <kjhall@us.ibm.com>
7 *
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.
11 *
12 * File: evm_crypto.c
13 * Using root's kernel master key (kmk), calculate the HMAC
14 */
15
16#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17
18#include <linux/module.h>
19#include <linux/crypto.h>
20#include <linux/xattr.h>
21#include <linux/evm.h>
22#include <keys/encrypted-type.h>
23#include <crypto/hash.h>
24#include "evm.h"
25
26#define EVMKEY "evm-key"
27#define MAX_KEY_SIZE 128
28static unsigned char evmkey[MAX_KEY_SIZE];
29static int evmkey_len = MAX_KEY_SIZE;
30
31struct crypto_shash *hmac_tfm;
32struct crypto_shash *hash_tfm;
33
34static DEFINE_MUTEX(mutex);
35
36#define EVM_SET_KEY_BUSY 0
37
38static unsigned long evm_set_key_flags;
39
40/**
41 * evm_set_key() - set EVM HMAC key from the kernel
42 * @key: pointer to a buffer with the key data
43 * @size: length of the key data
44 *
45 * This function allows setting the EVM HMAC key from the kernel
46 * without using the "encrypted" key subsystem keys. It can be used
47 * by the crypto HW kernel module which has its own way of managing
48 * keys.
49 *
50 * key length should be between 32 and 128 bytes long
51 */
52int evm_set_key(void *key, size_t keylen)
53{
54 int rc;
55
56 rc = -EBUSY;
57 if (test_and_set_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags))
58 goto busy;
59 rc = -EINVAL;
60 if (keylen > MAX_KEY_SIZE)
61 goto inval;
62 memcpy(evmkey, key, keylen);
63 evm_initialized |= EVM_INIT_HMAC;
64 pr_info("key initialized\n");
65 return 0;
66inval:
67 clear_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags);
68busy:
69 pr_err("key initialization failed\n");
70 return rc;
71}
72EXPORT_SYMBOL_GPL(evm_set_key);
73
74static struct shash_desc *init_desc(char type)
75{
76 long rc;
77 char *algo;
78 struct crypto_shash **tfm;
79 struct shash_desc *desc;
80
81 if (type == EVM_XATTR_HMAC) {
82 if (!(evm_initialized & EVM_INIT_HMAC)) {
83 pr_err("HMAC key is not set\n");
84 return ERR_PTR(-ENOKEY);
85 }
86 tfm = &hmac_tfm;
87 algo = evm_hmac;
88 } else {
89 tfm = &hash_tfm;
90 algo = evm_hash;
91 }
92
93 if (*tfm == NULL) {
94 mutex_lock(&mutex);
95 if (*tfm)
96 goto out;
97 *tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);
98 if (IS_ERR(*tfm)) {
99 rc = PTR_ERR(*tfm);
100 pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
101 *tfm = NULL;
102 mutex_unlock(&mutex);
103 return ERR_PTR(rc);
104 }
105 if (type == EVM_XATTR_HMAC) {
106 rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
107 if (rc) {
108 crypto_free_shash(*tfm);
109 *tfm = NULL;
110 mutex_unlock(&mutex);
111 return ERR_PTR(rc);
112 }
113 }
114out:
115 mutex_unlock(&mutex);
116 }
117
118 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
119 GFP_KERNEL);
120 if (!desc)
121 return ERR_PTR(-ENOMEM);
122
123 desc->tfm = *tfm;
124 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
125
126 rc = crypto_shash_init(desc);
127 if (rc) {
128 kfree(desc);
129 return ERR_PTR(rc);
130 }
131 return desc;
132}
133
134/* Protect against 'cutting & pasting' security.evm xattr, include inode
135 * specific info.
136 *
137 * (Additional directory/file metadata needs to be added for more complete
138 * protection.)
139 */
140static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
141 char *digest)
142{
143 struct h_misc {
144 unsigned long ino;
145 __u32 generation;
146 uid_t uid;
147 gid_t gid;
148 umode_t mode;
149 } hmac_misc;
150
151 memset(&hmac_misc, 0, sizeof(hmac_misc));
152 hmac_misc.ino = inode->i_ino;
153 hmac_misc.generation = inode->i_generation;
154 /* The hmac uid and gid must be encoded in the initial user
155 * namespace (not the filesystems user namespace) as encoding
156 * them in the filesystems user namespace allows an attack
157 * where first they are written in an unprivileged fuse mount
158 * of a filesystem and then the system is tricked to mount the
159 * filesystem for real on next boot and trust it because
160 * everything is signed.
161 */
162 hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
163 hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
164 hmac_misc.mode = inode->i_mode;
165 crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
166 if (evm_hmac_attrs & EVM_ATTR_FSUUID)
167 crypto_shash_update(desc, inode->i_sb->s_uuid,
168 sizeof(inode->i_sb->s_uuid));
169 crypto_shash_final(desc, digest);
170}
171
172/*
173 * Calculate the HMAC value across the set of protected security xattrs.
174 *
175 * Instead of retrieving the requested xattr, for performance, calculate
176 * the hmac using the requested xattr value. Don't alloc/free memory for
177 * each xattr, but attempt to re-use the previously allocated memory.
178 */
179static int evm_calc_hmac_or_hash(struct dentry *dentry,
180 const char *req_xattr_name,
181 const char *req_xattr_value,
182 size_t req_xattr_value_len,
183 char type, char *digest)
184{
185 struct inode *inode = d_backing_inode(dentry);
186 struct shash_desc *desc;
187 char **xattrname;
188 size_t xattr_size = 0;
189 char *xattr_value = NULL;
190 int error;
191 int size;
192
193 if (!(inode->i_opflags & IOP_XATTR))
194 return -EOPNOTSUPP;
195
196 desc = init_desc(type);
197 if (IS_ERR(desc))
198 return PTR_ERR(desc);
199
200 error = -ENODATA;
201 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
202 if ((req_xattr_name && req_xattr_value)
203 && !strcmp(*xattrname, req_xattr_name)) {
204 error = 0;
205 crypto_shash_update(desc, (const u8 *)req_xattr_value,
206 req_xattr_value_len);
207 continue;
208 }
209 size = vfs_getxattr_alloc(dentry, *xattrname,
210 &xattr_value, xattr_size, GFP_NOFS);
211 if (size == -ENOMEM) {
212 error = -ENOMEM;
213 goto out;
214 }
215 if (size < 0)
216 continue;
217
218 error = 0;
219 xattr_size = size;
220 crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
221 }
222 hmac_add_misc(desc, inode, digest);
223
224out:
225 kfree(xattr_value);
226 kfree(desc);
227 return error;
228}
229
230int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
231 const char *req_xattr_value, size_t req_xattr_value_len,
232 char *digest)
233{
234 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
235 req_xattr_value_len, EVM_XATTR_HMAC, digest);
236}
237
238int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
239 const char *req_xattr_value, size_t req_xattr_value_len,
240 char *digest)
241{
242 return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
243 req_xattr_value_len, IMA_XATTR_DIGEST, digest);
244}
245
246/*
247 * Calculate the hmac and update security.evm xattr
248 *
249 * Expects to be called with i_mutex locked.
250 */
251int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
252 const char *xattr_value, size_t xattr_value_len)
253{
254 struct inode *inode = d_backing_inode(dentry);
255 struct evm_ima_xattr_data xattr_data;
256 int rc = 0;
257
258 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
259 xattr_value_len, xattr_data.digest);
260 if (rc == 0) {
261 xattr_data.type = EVM_XATTR_HMAC;
262 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
263 &xattr_data,
264 sizeof(xattr_data), 0);
265 } else if (rc == -ENODATA && (inode->i_opflags & IOP_XATTR)) {
266 rc = __vfs_removexattr(dentry, XATTR_NAME_EVM);
267 }
268 return rc;
269}
270
271int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
272 char *hmac_val)
273{
274 struct shash_desc *desc;
275
276 desc = init_desc(EVM_XATTR_HMAC);
277 if (IS_ERR(desc)) {
278 pr_info("init_desc failed\n");
279 return PTR_ERR(desc);
280 }
281
282 crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
283 hmac_add_misc(desc, inode, hmac_val);
284 kfree(desc);
285 return 0;
286}
287
288/*
289 * Get the key from the TPM for the SHA1-HMAC
290 */
291int evm_init_key(void)
292{
293 struct key *evm_key;
294 struct encrypted_key_payload *ekp;
295 int rc;
296
297 evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
298 if (IS_ERR(evm_key))
299 return -ENOENT;
300
301 down_read(&evm_key->sem);
302 ekp = evm_key->payload.data[0];
303
304 rc = evm_set_key(ekp->decrypted_data, ekp->decrypted_datalen);
305
306 /* burn the original key contents */
307 memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
308 up_read(&evm_key->sem);
309 key_put(evm_key);
310 return rc;
311}