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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2010 IBM Corporation
4 *
5 * Authors:
6 * Mimi Zohar <zohar@us.ibm.com>
7 *
8 * File: evm_secfs.c
9 * - Used to signal when key is on keyring
10 * - Get the key and enable EVM
11 */
12
13#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15#include <linux/audit.h>
16#include <linux/uaccess.h>
17#include <linux/init.h>
18#include <linux/mutex.h>
19#include "evm.h"
20
21static struct dentry *evm_dir;
22static struct dentry *evm_init_tpm;
23static struct dentry *evm_symlink;
24
25#ifdef CONFIG_EVM_ADD_XATTRS
26static struct dentry *evm_xattrs;
27static DEFINE_MUTEX(xattr_list_mutex);
28static int evm_xattrs_locked;
29#endif
30
31/**
32 * evm_read_key - read() for <securityfs>/evm
33 *
34 * @filp: file pointer, not actually used
35 * @buf: where to put the result
36 * @count: maximum to send along
37 * @ppos: where to start
38 *
39 * Returns number of bytes read or error code, as appropriate
40 */
41static ssize_t evm_read_key(struct file *filp, char __user *buf,
42 size_t count, loff_t *ppos)
43{
44 char temp[80];
45 ssize_t rc;
46
47 if (*ppos != 0)
48 return 0;
49
50 sprintf(temp, "%d", (evm_initialized & ~EVM_SETUP_COMPLETE));
51 rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
52
53 return rc;
54}
55
56/**
57 * evm_write_key - write() for <securityfs>/evm
58 * @file: file pointer, not actually used
59 * @buf: where to get the data from
60 * @count: bytes sent
61 * @ppos: where to start
62 *
63 * Used to signal that key is on the kernel key ring.
64 * - get the integrity hmac key from the kernel key ring
65 * - create list of hmac protected extended attributes
66 * Returns number of bytes written or error code, as appropriate
67 */
68static ssize_t evm_write_key(struct file *file, const char __user *buf,
69 size_t count, loff_t *ppos)
70{
71 int i, ret;
72
73 if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP_COMPLETE))
74 return -EPERM;
75
76 ret = kstrtoint_from_user(buf, count, 0, &i);
77
78 if (ret)
79 return ret;
80
81 /* Reject invalid values */
82 if (!i || (i & ~EVM_INIT_MASK) != 0)
83 return -EINVAL;
84
85 /* Don't allow a request to freshly enable metadata writes if
86 * keys are loaded.
87 */
88 if ((i & EVM_ALLOW_METADATA_WRITES) &&
89 ((evm_initialized & EVM_KEY_MASK) != 0) &&
90 !(evm_initialized & EVM_ALLOW_METADATA_WRITES))
91 return -EPERM;
92
93 if (i & EVM_INIT_HMAC) {
94 ret = evm_init_key();
95 if (ret != 0)
96 return ret;
97 /* Forbid further writes after the symmetric key is loaded */
98 i |= EVM_SETUP_COMPLETE;
99 }
100
101 evm_initialized |= i;
102
103 /* Don't allow protected metadata modification if a symmetric key
104 * is loaded
105 */
106 if (evm_initialized & EVM_INIT_HMAC)
107 evm_initialized &= ~(EVM_ALLOW_METADATA_WRITES);
108
109 return count;
110}
111
112static const struct file_operations evm_key_ops = {
113 .read = evm_read_key,
114 .write = evm_write_key,
115};
116
117#ifdef CONFIG_EVM_ADD_XATTRS
118/**
119 * evm_read_xattrs - read() for <securityfs>/evm_xattrs
120 *
121 * @filp: file pointer, not actually used
122 * @buf: where to put the result
123 * @count: maximum to send along
124 * @ppos: where to start
125 *
126 * Returns number of bytes read or error code, as appropriate
127 */
128static ssize_t evm_read_xattrs(struct file *filp, char __user *buf,
129 size_t count, loff_t *ppos)
130{
131 char *temp;
132 int offset = 0;
133 ssize_t rc, size = 0;
134 struct xattr_list *xattr;
135
136 if (*ppos != 0)
137 return 0;
138
139 rc = mutex_lock_interruptible(&xattr_list_mutex);
140 if (rc)
141 return -ERESTARTSYS;
142
143 list_for_each_entry(xattr, &evm_config_xattrnames, list)
144 size += strlen(xattr->name) + 1;
145
146 temp = kmalloc(size + 1, GFP_KERNEL);
147 if (!temp) {
148 mutex_unlock(&xattr_list_mutex);
149 return -ENOMEM;
150 }
151
152 list_for_each_entry(xattr, &evm_config_xattrnames, list) {
153 sprintf(temp + offset, "%s\n", xattr->name);
154 offset += strlen(xattr->name) + 1;
155 }
156
157 mutex_unlock(&xattr_list_mutex);
158 rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
159
160 kfree(temp);
161
162 return rc;
163}
164
165/**
166 * evm_write_xattrs - write() for <securityfs>/evm_xattrs
167 * @file: file pointer, not actually used
168 * @buf: where to get the data from
169 * @count: bytes sent
170 * @ppos: where to start
171 *
172 * Returns number of bytes written or error code, as appropriate
173 */
174static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
175 size_t count, loff_t *ppos)
176{
177 int len, err;
178 struct xattr_list *xattr, *tmp;
179 struct audit_buffer *ab;
180 struct iattr newattrs;
181 struct inode *inode;
182
183 if (!capable(CAP_SYS_ADMIN) || evm_xattrs_locked)
184 return -EPERM;
185
186 if (*ppos != 0)
187 return -EINVAL;
188
189 if (count > XATTR_NAME_MAX)
190 return -E2BIG;
191
192 ab = audit_log_start(audit_context(), GFP_KERNEL,
193 AUDIT_INTEGRITY_EVM_XATTR);
194 if (!ab)
195 return -ENOMEM;
196
197 xattr = kmalloc(sizeof(struct xattr_list), GFP_KERNEL);
198 if (!xattr) {
199 err = -ENOMEM;
200 goto out;
201 }
202
203 xattr->name = memdup_user_nul(buf, count);
204 if (IS_ERR(xattr->name)) {
205 err = PTR_ERR(xattr->name);
206 xattr->name = NULL;
207 goto out;
208 }
209
210 /* Remove any trailing newline */
211 len = strlen(xattr->name);
212 if (len && xattr->name[len-1] == '\n')
213 xattr->name[len-1] = '\0';
214
215 audit_log_format(ab, "xattr=");
216 audit_log_untrustedstring(ab, xattr->name);
217
218 if (strcmp(xattr->name, ".") == 0) {
219 evm_xattrs_locked = 1;
220 newattrs.ia_mode = S_IFREG | 0440;
221 newattrs.ia_valid = ATTR_MODE;
222 inode = evm_xattrs->d_inode;
223 inode_lock(inode);
224 err = simple_setattr(evm_xattrs, &newattrs);
225 inode_unlock(inode);
226 if (!err)
227 err = count;
228 goto out;
229 }
230
231 if (strncmp(xattr->name, XATTR_SECURITY_PREFIX,
232 XATTR_SECURITY_PREFIX_LEN) != 0) {
233 err = -EINVAL;
234 goto out;
235 }
236
237 /* Guard against races in evm_read_xattrs */
238 mutex_lock(&xattr_list_mutex);
239 list_for_each_entry(tmp, &evm_config_xattrnames, list) {
240 if (strcmp(xattr->name, tmp->name) == 0) {
241 err = -EEXIST;
242 mutex_unlock(&xattr_list_mutex);
243 goto out;
244 }
245 }
246 list_add_tail_rcu(&xattr->list, &evm_config_xattrnames);
247 mutex_unlock(&xattr_list_mutex);
248
249 audit_log_format(ab, " res=0");
250 audit_log_end(ab);
251 return count;
252out:
253 audit_log_format(ab, " res=%d", err);
254 audit_log_end(ab);
255 if (xattr) {
256 kfree(xattr->name);
257 kfree(xattr);
258 }
259 return err;
260}
261
262static const struct file_operations evm_xattr_ops = {
263 .read = evm_read_xattrs,
264 .write = evm_write_xattrs,
265};
266
267static int evm_init_xattrs(void)
268{
269 evm_xattrs = securityfs_create_file("evm_xattrs", 0660, evm_dir, NULL,
270 &evm_xattr_ops);
271 if (!evm_xattrs || IS_ERR(evm_xattrs))
272 return -EFAULT;
273
274 return 0;
275}
276#else
277static int evm_init_xattrs(void)
278{
279 return 0;
280}
281#endif
282
283int __init evm_init_secfs(void)
284{
285 int error = 0;
286
287 evm_dir = securityfs_create_dir("evm", integrity_dir);
288 if (!evm_dir || IS_ERR(evm_dir))
289 return -EFAULT;
290
291 evm_init_tpm = securityfs_create_file("evm", 0660,
292 evm_dir, NULL, &evm_key_ops);
293 if (!evm_init_tpm || IS_ERR(evm_init_tpm)) {
294 error = -EFAULT;
295 goto out;
296 }
297
298 evm_symlink = securityfs_create_symlink("evm", NULL,
299 "integrity/evm/evm", NULL);
300 if (!evm_symlink || IS_ERR(evm_symlink)) {
301 error = -EFAULT;
302 goto out;
303 }
304
305 if (evm_init_xattrs() != 0) {
306 error = -EFAULT;
307 goto out;
308 }
309
310 return 0;
311out:
312 securityfs_remove(evm_symlink);
313 securityfs_remove(evm_init_tpm);
314 securityfs_remove(evm_dir);
315 return error;
316}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2010 IBM Corporation
4 *
5 * Authors:
6 * Mimi Zohar <zohar@us.ibm.com>
7 *
8 * File: evm_secfs.c
9 * - Used to signal when key is on keyring
10 * - Get the key and enable EVM
11 */
12
13#include <linux/audit.h>
14#include <linux/uaccess.h>
15#include <linux/init.h>
16#include <linux/mutex.h>
17#include "evm.h"
18
19static struct dentry *evm_dir;
20static struct dentry *evm_init_tpm;
21static struct dentry *evm_symlink;
22
23#ifdef CONFIG_EVM_ADD_XATTRS
24static struct dentry *evm_xattrs;
25static DEFINE_MUTEX(xattr_list_mutex);
26static int evm_xattrs_locked;
27#endif
28
29/**
30 * evm_read_key - read() for <securityfs>/evm
31 *
32 * @filp: file pointer, not actually used
33 * @buf: where to put the result
34 * @count: maximum to send along
35 * @ppos: where to start
36 *
37 * Returns number of bytes read or error code, as appropriate
38 */
39static ssize_t evm_read_key(struct file *filp, char __user *buf,
40 size_t count, loff_t *ppos)
41{
42 char temp[80];
43 ssize_t rc;
44
45 if (*ppos != 0)
46 return 0;
47
48 sprintf(temp, "%d", (evm_initialized & ~EVM_SETUP_COMPLETE));
49 rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
50
51 return rc;
52}
53
54/**
55 * evm_write_key - write() for <securityfs>/evm
56 * @file: file pointer, not actually used
57 * @buf: where to get the data from
58 * @count: bytes sent
59 * @ppos: where to start
60 *
61 * Used to signal that key is on the kernel key ring.
62 * - get the integrity hmac key from the kernel key ring
63 * - create list of hmac protected extended attributes
64 * Returns number of bytes written or error code, as appropriate
65 */
66static ssize_t evm_write_key(struct file *file, const char __user *buf,
67 size_t count, loff_t *ppos)
68{
69 unsigned int i;
70 int ret;
71
72 if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP_COMPLETE))
73 return -EPERM;
74
75 ret = kstrtouint_from_user(buf, count, 0, &i);
76
77 if (ret)
78 return ret;
79
80 /* Reject invalid values */
81 if (!i || (i & ~EVM_INIT_MASK) != 0)
82 return -EINVAL;
83
84 /*
85 * Don't allow a request to enable metadata writes if
86 * an HMAC key is loaded.
87 */
88 if ((i & EVM_ALLOW_METADATA_WRITES) &&
89 (evm_initialized & EVM_INIT_HMAC) != 0)
90 return -EPERM;
91
92 if (i & EVM_INIT_HMAC) {
93 ret = evm_init_key();
94 if (ret != 0)
95 return ret;
96 /* Forbid further writes after the symmetric key is loaded */
97 i |= EVM_SETUP_COMPLETE;
98 }
99
100 evm_initialized |= i;
101
102 /* Don't allow protected metadata modification if a symmetric key
103 * is loaded
104 */
105 if (evm_initialized & EVM_INIT_HMAC)
106 evm_initialized &= ~(EVM_ALLOW_METADATA_WRITES);
107
108 return count;
109}
110
111static const struct file_operations evm_key_ops = {
112 .read = evm_read_key,
113 .write = evm_write_key,
114};
115
116#ifdef CONFIG_EVM_ADD_XATTRS
117/**
118 * evm_read_xattrs - read() for <securityfs>/evm_xattrs
119 *
120 * @filp: file pointer, not actually used
121 * @buf: where to put the result
122 * @count: maximum to send along
123 * @ppos: where to start
124 *
125 * Returns number of bytes read or error code, as appropriate
126 */
127static ssize_t evm_read_xattrs(struct file *filp, char __user *buf,
128 size_t count, loff_t *ppos)
129{
130 char *temp;
131 int offset = 0;
132 ssize_t rc, size = 0;
133 struct xattr_list *xattr;
134
135 if (*ppos != 0)
136 return 0;
137
138 rc = mutex_lock_interruptible(&xattr_list_mutex);
139 if (rc)
140 return -ERESTARTSYS;
141
142 list_for_each_entry(xattr, &evm_config_xattrnames, list) {
143 if (!xattr->enabled)
144 continue;
145
146 size += strlen(xattr->name) + 1;
147 }
148
149 temp = kmalloc(size + 1, GFP_KERNEL);
150 if (!temp) {
151 mutex_unlock(&xattr_list_mutex);
152 return -ENOMEM;
153 }
154
155 list_for_each_entry(xattr, &evm_config_xattrnames, list) {
156 if (!xattr->enabled)
157 continue;
158
159 sprintf(temp + offset, "%s\n", xattr->name);
160 offset += strlen(xattr->name) + 1;
161 }
162
163 mutex_unlock(&xattr_list_mutex);
164 rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
165
166 kfree(temp);
167
168 return rc;
169}
170
171/**
172 * evm_write_xattrs - write() for <securityfs>/evm_xattrs
173 * @file: file pointer, not actually used
174 * @buf: where to get the data from
175 * @count: bytes sent
176 * @ppos: where to start
177 *
178 * Returns number of bytes written or error code, as appropriate
179 */
180static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
181 size_t count, loff_t *ppos)
182{
183 int len, err;
184 struct xattr_list *xattr, *tmp;
185 struct audit_buffer *ab;
186 struct iattr newattrs;
187 struct inode *inode;
188
189 if (!capable(CAP_SYS_ADMIN) || evm_xattrs_locked)
190 return -EPERM;
191
192 if (*ppos != 0)
193 return -EINVAL;
194
195 if (count > XATTR_NAME_MAX)
196 return -E2BIG;
197
198 ab = audit_log_start(audit_context(), GFP_KERNEL,
199 AUDIT_INTEGRITY_EVM_XATTR);
200 if (!ab && IS_ENABLED(CONFIG_AUDIT))
201 return -ENOMEM;
202
203 xattr = kmalloc(sizeof(struct xattr_list), GFP_KERNEL);
204 if (!xattr) {
205 err = -ENOMEM;
206 goto out;
207 }
208
209 xattr->enabled = true;
210 xattr->name = memdup_user_nul(buf, count);
211 if (IS_ERR(xattr->name)) {
212 err = PTR_ERR(xattr->name);
213 xattr->name = NULL;
214 goto out;
215 }
216
217 /* Remove any trailing newline */
218 len = strlen(xattr->name);
219 if (len && xattr->name[len-1] == '\n')
220 xattr->name[len-1] = '\0';
221
222 audit_log_format(ab, "xattr=");
223 audit_log_untrustedstring(ab, xattr->name);
224
225 if (strcmp(xattr->name, ".") == 0) {
226 evm_xattrs_locked = 1;
227 newattrs.ia_mode = S_IFREG | 0440;
228 newattrs.ia_valid = ATTR_MODE;
229 inode = evm_xattrs->d_inode;
230 inode_lock(inode);
231 err = simple_setattr(&nop_mnt_idmap, evm_xattrs, &newattrs);
232 inode_unlock(inode);
233 if (!err)
234 err = count;
235 goto out;
236 }
237
238 if (strncmp(xattr->name, XATTR_SECURITY_PREFIX,
239 XATTR_SECURITY_PREFIX_LEN) != 0) {
240 err = -EINVAL;
241 goto out;
242 }
243
244 /*
245 * xattr_list_mutex guards against races in evm_read_xattrs().
246 * Entries are only added to the evm_config_xattrnames list
247 * and never deleted. Therefore, the list is traversed
248 * using list_for_each_entry_lockless() without holding
249 * the mutex in evm_calc_hmac_or_hash(), evm_find_protected_xattrs()
250 * and evm_protected_xattr().
251 */
252 mutex_lock(&xattr_list_mutex);
253 list_for_each_entry(tmp, &evm_config_xattrnames, list) {
254 if (strcmp(xattr->name, tmp->name) == 0) {
255 err = -EEXIST;
256 if (!tmp->enabled) {
257 tmp->enabled = true;
258 err = count;
259 }
260 mutex_unlock(&xattr_list_mutex);
261 goto out;
262 }
263 }
264 list_add_tail_rcu(&xattr->list, &evm_config_xattrnames);
265 mutex_unlock(&xattr_list_mutex);
266
267 audit_log_format(ab, " res=0");
268 audit_log_end(ab);
269 return count;
270out:
271 audit_log_format(ab, " res=%d", (err < 0) ? err : 0);
272 audit_log_end(ab);
273 if (xattr) {
274 kfree(xattr->name);
275 kfree(xattr);
276 }
277 return err;
278}
279
280static const struct file_operations evm_xattr_ops = {
281 .read = evm_read_xattrs,
282 .write = evm_write_xattrs,
283};
284
285static int evm_init_xattrs(void)
286{
287 evm_xattrs = securityfs_create_file("evm_xattrs", 0660, evm_dir, NULL,
288 &evm_xattr_ops);
289 if (!evm_xattrs || IS_ERR(evm_xattrs))
290 return -EFAULT;
291
292 return 0;
293}
294#else
295static int evm_init_xattrs(void)
296{
297 return 0;
298}
299#endif
300
301int __init evm_init_secfs(void)
302{
303 int error = 0;
304
305 evm_dir = securityfs_create_dir("evm", integrity_dir);
306 if (!evm_dir || IS_ERR(evm_dir))
307 return -EFAULT;
308
309 evm_init_tpm = securityfs_create_file("evm", 0660,
310 evm_dir, NULL, &evm_key_ops);
311 if (!evm_init_tpm || IS_ERR(evm_init_tpm)) {
312 error = -EFAULT;
313 goto out;
314 }
315
316 evm_symlink = securityfs_create_symlink("evm", NULL,
317 "integrity/evm/evm", NULL);
318 if (!evm_symlink || IS_ERR(evm_symlink)) {
319 error = -EFAULT;
320 goto out;
321 }
322
323 if (evm_init_xattrs() != 0) {
324 error = -EFAULT;
325 goto out;
326 }
327
328 return 0;
329out:
330 securityfs_remove(evm_symlink);
331 securityfs_remove(evm_init_tpm);
332 securityfs_remove(evm_dir);
333 return error;
334}