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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/*
2 * Copyright (C) 2010 IBM Corporation
3 *
4 * Authors:
5 * Mimi Zohar <zohar@us.ibm.com>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, version 2 of the License.
10 *
11 * File: evm_secfs.c
12 * - Used to signal when key is on keyring
13 * - Get the key and enable EVM
14 */
15
16#include <linux/uaccess.h>
17#include <linux/module.h>
18#include "evm.h"
19
20static struct dentry *evm_init_tpm;
21
22/**
23 * evm_read_key - read() for <securityfs>/evm
24 *
25 * @filp: file pointer, not actually used
26 * @buf: where to put the result
27 * @count: maximum to send along
28 * @ppos: where to start
29 *
30 * Returns number of bytes read or error code, as appropriate
31 */
32static ssize_t evm_read_key(struct file *filp, char __user *buf,
33 size_t count, loff_t *ppos)
34{
35 char temp[80];
36 ssize_t rc;
37
38 if (*ppos != 0)
39 return 0;
40
41 sprintf(temp, "%d", evm_initialized);
42 rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
43
44 return rc;
45}
46
47/**
48 * evm_write_key - write() for <securityfs>/evm
49 * @file: file pointer, not actually used
50 * @buf: where to get the data from
51 * @count: bytes sent
52 * @ppos: where to start
53 *
54 * Used to signal that key is on the kernel key ring.
55 * - get the integrity hmac key from the kernel key ring
56 * - create list of hmac protected extended attributes
57 * Returns number of bytes written or error code, as appropriate
58 */
59static ssize_t evm_write_key(struct file *file, const char __user *buf,
60 size_t count, loff_t *ppos)
61{
62 char temp[80];
63 int i, error;
64
65 if (!capable(CAP_SYS_ADMIN) || evm_initialized)
66 return -EPERM;
67
68 if (count >= sizeof(temp) || count == 0)
69 return -EINVAL;
70
71 if (copy_from_user(temp, buf, count) != 0)
72 return -EFAULT;
73
74 temp[count] = '\0';
75
76 if ((sscanf(temp, "%d", &i) != 1) || (i != 1))
77 return -EINVAL;
78
79 error = evm_init_key();
80 if (!error) {
81 evm_initialized = 1;
82 pr_info("EVM: initialized\n");
83 } else
84 pr_err("EVM: initialization failed\n");
85 return count;
86}
87
88static const struct file_operations evm_key_ops = {
89 .read = evm_read_key,
90 .write = evm_write_key,
91};
92
93int __init evm_init_secfs(void)
94{
95 int error = 0;
96
97 evm_init_tpm = securityfs_create_file("evm", S_IRUSR | S_IRGRP,
98 NULL, NULL, &evm_key_ops);
99 if (!evm_init_tpm || IS_ERR(evm_init_tpm))
100 error = -EFAULT;
101 return error;
102}
103
104void __exit evm_cleanup_secfs(void)
105{
106 if (evm_init_tpm)
107 securityfs_remove(evm_init_tpm);
108}