~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/security/integrity/evm/evm_crypto.c

Version: ~ [ linux-5.8 ] ~ [ linux-5.7.12 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.55 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.136 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.191 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.232 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.232 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.85 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  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
 26 static unsigned char evmkey[MAX_KEY_SIZE];
 27 static const int evmkey_len = MAX_KEY_SIZE;
 28 
 29 struct crypto_shash *hmac_tfm;
 30 static struct crypto_shash *evm_tfm[HASH_ALGO__LAST];
 31 
 32 static DEFINE_MUTEX(mutex);
 33 
 34 #define EVM_SET_KEY_BUSY 0
 35 
 36 static unsigned long evm_set_key_flags;
 37 
 38 static 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  */
 52 int 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;
 66 inval:
 67         clear_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags);
 68 busy:
 69         pr_err("key initialization failed\n");
 70         return rc;
 71 }
 72 EXPORT_SYMBOL_GPL(evm_set_key);
 73 
 74 static 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                 }
117 out:
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  */
142 static 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  */
186 static 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;
247 out:
248         kfree(xattr_value);
249         kfree(desc);
250         return error;
251 }
252 
253 int 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 
261 int 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 
269 static 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  */
302 int 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 
333 int 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  */
353 int 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 }
374 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp