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b886d83c | 1 | // SPDX-License-Identifier: GPL-2.0-only |
66dbc325 MZ |
2 | /* |
3 | * Copyright (C) 2010 IBM Corporation | |
4 | * | |
5 | * Authors: | |
6 | * Mimi Zohar <zohar@us.ibm.com> | |
7 | * | |
66dbc325 MZ |
8 | * File: evm_secfs.c |
9 | * - Used to signal when key is on keyring | |
10 | * - Get the key and enable EVM | |
11 | */ | |
12 | ||
fa516b66 | 13 | #include <linux/audit.h> |
66dbc325 | 14 | #include <linux/uaccess.h> |
876979c9 | 15 | #include <linux/init.h> |
fa516b66 | 16 | #include <linux/mutex.h> |
66dbc325 MZ |
17 | #include "evm.h" |
18 | ||
0c343af8 | 19 | static struct dentry *evm_dir; |
66dbc325 | 20 | static struct dentry *evm_init_tpm; |
0c343af8 | 21 | static struct dentry *evm_symlink; |
66dbc325 | 22 | |
fa516b66 MG |
23 | #ifdef CONFIG_EVM_ADD_XATTRS |
24 | static struct dentry *evm_xattrs; | |
25 | static DEFINE_MUTEX(xattr_list_mutex); | |
26 | static int evm_xattrs_locked; | |
27 | #endif | |
28 | ||
66dbc325 MZ |
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 | */ | |
39 | static 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 | ||
ae1ba167 | 48 | sprintf(temp, "%d", (evm_initialized & ~EVM_SETUP_COMPLETE)); |
66dbc325 MZ |
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 | */ | |
66 | static ssize_t evm_write_key(struct file *file, const char __user *buf, | |
67 | size_t count, loff_t *ppos) | |
68 | { | |
f00d7975 | 69 | int i, ret; |
66dbc325 | 70 | |
ae1ba167 | 71 | if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP_COMPLETE)) |
66dbc325 MZ |
72 | return -EPERM; |
73 | ||
f00d7975 | 74 | ret = kstrtoint_from_user(buf, count, 0, &i); |
66dbc325 | 75 | |
f00d7975 MG |
76 | if (ret) |
77 | return ret; | |
66dbc325 | 78 | |
f00d7975 MG |
79 | /* Reject invalid values */ |
80 | if (!i || (i & ~EVM_INIT_MASK) != 0) | |
66dbc325 MZ |
81 | return -EINVAL; |
82 | ||
ae1ba167 MG |
83 | /* Don't allow a request to freshly enable metadata writes if |
84 | * keys are loaded. | |
85 | */ | |
86 | if ((i & EVM_ALLOW_METADATA_WRITES) && | |
87 | ((evm_initialized & EVM_KEY_MASK) != 0) && | |
88 | !(evm_initialized & EVM_ALLOW_METADATA_WRITES)) | |
89 | return -EPERM; | |
90 | ||
f00d7975 MG |
91 | if (i & EVM_INIT_HMAC) { |
92 | ret = evm_init_key(); | |
93 | if (ret != 0) | |
94 | return ret; | |
95 | /* Forbid further writes after the symmetric key is loaded */ | |
ae1ba167 | 96 | i |= EVM_SETUP_COMPLETE; |
f00d7975 MG |
97 | } |
98 | ||
99 | evm_initialized |= i; | |
76266763 | 100 | |
ae1ba167 MG |
101 | /* Don't allow protected metadata modification if a symmetric key |
102 | * is loaded | |
103 | */ | |
104 | if (evm_initialized & EVM_INIT_HMAC) | |
105 | evm_initialized &= ~(EVM_ALLOW_METADATA_WRITES); | |
106 | ||
66dbc325 MZ |
107 | return count; |
108 | } | |
109 | ||
110 | static const struct file_operations evm_key_ops = { | |
111 | .read = evm_read_key, | |
112 | .write = evm_write_key, | |
113 | }; | |
114 | ||
fa516b66 MG |
115 | #ifdef CONFIG_EVM_ADD_XATTRS |
116 | /** | |
117 | * evm_read_xattrs - read() for <securityfs>/evm_xattrs | |
118 | * | |
119 | * @filp: file pointer, not actually used | |
120 | * @buf: where to put the result | |
121 | * @count: maximum to send along | |
122 | * @ppos: where to start | |
123 | * | |
124 | * Returns number of bytes read or error code, as appropriate | |
125 | */ | |
126 | static ssize_t evm_read_xattrs(struct file *filp, char __user *buf, | |
127 | size_t count, loff_t *ppos) | |
128 | { | |
129 | char *temp; | |
130 | int offset = 0; | |
131 | ssize_t rc, size = 0; | |
132 | struct xattr_list *xattr; | |
133 | ||
134 | if (*ppos != 0) | |
135 | return 0; | |
136 | ||
137 | rc = mutex_lock_interruptible(&xattr_list_mutex); | |
138 | if (rc) | |
139 | return -ERESTARTSYS; | |
140 | ||
141 | list_for_each_entry(xattr, &evm_config_xattrnames, list) | |
142 | size += strlen(xattr->name) + 1; | |
143 | ||
144 | temp = kmalloc(size + 1, GFP_KERNEL); | |
b5c90a75 DC |
145 | if (!temp) { |
146 | mutex_unlock(&xattr_list_mutex); | |
fa516b66 | 147 | return -ENOMEM; |
b5c90a75 | 148 | } |
fa516b66 MG |
149 | |
150 | list_for_each_entry(xattr, &evm_config_xattrnames, list) { | |
151 | sprintf(temp + offset, "%s\n", xattr->name); | |
152 | offset += strlen(xattr->name) + 1; | |
153 | } | |
154 | ||
155 | mutex_unlock(&xattr_list_mutex); | |
156 | rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); | |
157 | ||
825b8650 CIK |
158 | kfree(temp); |
159 | ||
fa516b66 MG |
160 | return rc; |
161 | } | |
162 | ||
163 | /** | |
164 | * evm_write_xattrs - write() for <securityfs>/evm_xattrs | |
165 | * @file: file pointer, not actually used | |
166 | * @buf: where to get the data from | |
167 | * @count: bytes sent | |
168 | * @ppos: where to start | |
169 | * | |
170 | * Returns number of bytes written or error code, as appropriate | |
171 | */ | |
172 | static ssize_t evm_write_xattrs(struct file *file, const char __user *buf, | |
173 | size_t count, loff_t *ppos) | |
174 | { | |
175 | int len, err; | |
176 | struct xattr_list *xattr, *tmp; | |
177 | struct audit_buffer *ab; | |
178 | struct iattr newattrs; | |
179 | struct inode *inode; | |
180 | ||
181 | if (!capable(CAP_SYS_ADMIN) || evm_xattrs_locked) | |
182 | return -EPERM; | |
183 | ||
184 | if (*ppos != 0) | |
185 | return -EINVAL; | |
186 | ||
187 | if (count > XATTR_NAME_MAX) | |
188 | return -E2BIG; | |
189 | ||
a1aa08a0 RGB |
190 | ab = audit_log_start(audit_context(), GFP_KERNEL, |
191 | AUDIT_INTEGRITY_EVM_XATTR); | |
3dd0f18c WY |
192 | if (!ab) |
193 | return -ENOMEM; | |
fa516b66 MG |
194 | |
195 | xattr = kmalloc(sizeof(struct xattr_list), GFP_KERNEL); | |
196 | if (!xattr) { | |
197 | err = -ENOMEM; | |
198 | goto out; | |
199 | } | |
200 | ||
201 | xattr->name = memdup_user_nul(buf, count); | |
202 | if (IS_ERR(xattr->name)) { | |
203 | err = PTR_ERR(xattr->name); | |
204 | xattr->name = NULL; | |
205 | goto out; | |
206 | } | |
207 | ||
208 | /* Remove any trailing newline */ | |
209 | len = strlen(xattr->name); | |
a41d80ac | 210 | if (len && xattr->name[len-1] == '\n') |
fa516b66 MG |
211 | xattr->name[len-1] = '\0'; |
212 | ||
a1aa08a0 RGB |
213 | audit_log_format(ab, "xattr="); |
214 | audit_log_untrustedstring(ab, xattr->name); | |
215 | ||
fa516b66 MG |
216 | if (strcmp(xattr->name, ".") == 0) { |
217 | evm_xattrs_locked = 1; | |
218 | newattrs.ia_mode = S_IFREG | 0440; | |
219 | newattrs.ia_valid = ATTR_MODE; | |
220 | inode = evm_xattrs->d_inode; | |
221 | inode_lock(inode); | |
549c7297 | 222 | err = simple_setattr(&init_user_ns, evm_xattrs, &newattrs); |
fa516b66 | 223 | inode_unlock(inode); |
fa516b66 MG |
224 | if (!err) |
225 | err = count; | |
226 | goto out; | |
227 | } | |
228 | ||
fa516b66 MG |
229 | if (strncmp(xattr->name, XATTR_SECURITY_PREFIX, |
230 | XATTR_SECURITY_PREFIX_LEN) != 0) { | |
231 | err = -EINVAL; | |
232 | goto out; | |
233 | } | |
234 | ||
770f6058 MB |
235 | /* |
236 | * xattr_list_mutex guards against races in evm_read_xattrs(). | |
237 | * Entries are only added to the evm_config_xattrnames list | |
238 | * and never deleted. Therefore, the list is traversed | |
239 | * using list_for_each_entry_lockless() without holding | |
240 | * the mutex in evm_calc_hmac_or_hash(), evm_find_protected_xattrs() | |
241 | * and evm_protected_xattr(). | |
242 | */ | |
fa516b66 MG |
243 | mutex_lock(&xattr_list_mutex); |
244 | list_for_each_entry(tmp, &evm_config_xattrnames, list) { | |
245 | if (strcmp(xattr->name, tmp->name) == 0) { | |
246 | err = -EEXIST; | |
247 | mutex_unlock(&xattr_list_mutex); | |
248 | goto out; | |
249 | } | |
250 | } | |
251 | list_add_tail_rcu(&xattr->list, &evm_config_xattrnames); | |
252 | mutex_unlock(&xattr_list_mutex); | |
253 | ||
254 | audit_log_format(ab, " res=0"); | |
255 | audit_log_end(ab); | |
256 | return count; | |
257 | out: | |
258 | audit_log_format(ab, " res=%d", err); | |
259 | audit_log_end(ab); | |
72acd64d CIK |
260 | if (xattr) { |
261 | kfree(xattr->name); | |
262 | kfree(xattr); | |
263 | } | |
fa516b66 MG |
264 | return err; |
265 | } | |
266 | ||
267 | static const struct file_operations evm_xattr_ops = { | |
268 | .read = evm_read_xattrs, | |
269 | .write = evm_write_xattrs, | |
270 | }; | |
271 | ||
272 | static int evm_init_xattrs(void) | |
273 | { | |
274 | evm_xattrs = securityfs_create_file("evm_xattrs", 0660, evm_dir, NULL, | |
275 | &evm_xattr_ops); | |
276 | if (!evm_xattrs || IS_ERR(evm_xattrs)) | |
277 | return -EFAULT; | |
278 | ||
279 | return 0; | |
280 | } | |
281 | #else | |
282 | static int evm_init_xattrs(void) | |
283 | { | |
284 | return 0; | |
285 | } | |
286 | #endif | |
287 | ||
66dbc325 MZ |
288 | int __init evm_init_secfs(void) |
289 | { | |
290 | int error = 0; | |
291 | ||
0c343af8 MG |
292 | evm_dir = securityfs_create_dir("evm", integrity_dir); |
293 | if (!evm_dir || IS_ERR(evm_dir)) | |
294 | return -EFAULT; | |
295 | ||
296 | evm_init_tpm = securityfs_create_file("evm", 0660, | |
297 | evm_dir, NULL, &evm_key_ops); | |
298 | if (!evm_init_tpm || IS_ERR(evm_init_tpm)) { | |
299 | error = -EFAULT; | |
300 | goto out; | |
301 | } | |
302 | ||
303 | evm_symlink = securityfs_create_symlink("evm", NULL, | |
304 | "integrity/evm/evm", NULL); | |
305 | if (!evm_symlink || IS_ERR(evm_symlink)) { | |
66dbc325 | 306 | error = -EFAULT; |
0c343af8 MG |
307 | goto out; |
308 | } | |
309 | ||
fa516b66 MG |
310 | if (evm_init_xattrs() != 0) { |
311 | error = -EFAULT; | |
312 | goto out; | |
313 | } | |
314 | ||
0c343af8 MG |
315 | return 0; |
316 | out: | |
317 | securityfs_remove(evm_symlink); | |
318 | securityfs_remove(evm_init_tpm); | |
319 | securityfs_remove(evm_dir); | |
66dbc325 MZ |
320 | return error; |
321 | } |