2 * Copyright (C) 2010 IBM Corporation
5 * Mimi Zohar <zohar@us.ibm.com>
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.
12 * - Used to signal when key is on keyring
13 * - Get the key and enable EVM
16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18 #include <linux/audit.h>
19 #include <linux/uaccess.h>
20 #include <linux/module.h>
21 #include <linux/mutex.h>
24 static struct dentry *evm_dir;
25 static struct dentry *evm_init_tpm;
26 static struct dentry *evm_symlink;
28 #ifdef CONFIG_EVM_ADD_XATTRS
29 static struct dentry *evm_xattrs;
30 static DEFINE_MUTEX(xattr_list_mutex);
31 static int evm_xattrs_locked;
35 * evm_read_key - read() for <securityfs>/evm
37 * @filp: file pointer, not actually used
38 * @buf: where to put the result
39 * @count: maximum to send along
40 * @ppos: where to start
42 * Returns number of bytes read or error code, as appropriate
44 static ssize_t evm_read_key(struct file *filp, char __user *buf,
45 size_t count, loff_t *ppos)
53 sprintf(temp, "%d", (evm_initialized & ~EVM_SETUP_COMPLETE));
54 rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
60 * evm_write_key - write() for <securityfs>/evm
61 * @file: file pointer, not actually used
62 * @buf: where to get the data from
64 * @ppos: where to start
66 * Used to signal that key is on the kernel key ring.
67 * - get the integrity hmac key from the kernel key ring
68 * - create list of hmac protected extended attributes
69 * Returns number of bytes written or error code, as appropriate
71 static ssize_t evm_write_key(struct file *file, const char __user *buf,
72 size_t count, loff_t *ppos)
77 if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP_COMPLETE))
80 ret = kstrtouint_from_user(buf, count, 0, &i);
85 /* Reject invalid values */
86 if (!i || (i & ~EVM_INIT_MASK) != 0)
90 * Don't allow a request to enable metadata writes if
91 * an HMAC key is loaded.
93 if ((i & EVM_ALLOW_METADATA_WRITES) &&
94 (evm_initialized & EVM_INIT_HMAC) != 0)
97 if (i & EVM_INIT_HMAC) {
101 /* Forbid further writes after the symmetric key is loaded */
102 i |= EVM_SETUP_COMPLETE;
105 evm_initialized |= i;
107 /* Don't allow protected metadata modification if a symmetric key
110 if (evm_initialized & EVM_INIT_HMAC)
111 evm_initialized &= ~(EVM_ALLOW_METADATA_WRITES);
116 static const struct file_operations evm_key_ops = {
117 .read = evm_read_key,
118 .write = evm_write_key,
121 #ifdef CONFIG_EVM_ADD_XATTRS
123 * evm_read_xattrs - read() for <securityfs>/evm_xattrs
125 * @filp: file pointer, not actually used
126 * @buf: where to put the result
127 * @count: maximum to send along
128 * @ppos: where to start
130 * Returns number of bytes read or error code, as appropriate
132 static ssize_t evm_read_xattrs(struct file *filp, char __user *buf,
133 size_t count, loff_t *ppos)
137 ssize_t rc, size = 0;
138 struct xattr_list *xattr;
143 rc = mutex_lock_interruptible(&xattr_list_mutex);
147 list_for_each_entry(xattr, &evm_config_xattrnames, list)
148 size += strlen(xattr->name) + 1;
150 temp = kmalloc(size + 1, GFP_KERNEL);
152 mutex_unlock(&xattr_list_mutex);
156 list_for_each_entry(xattr, &evm_config_xattrnames, list) {
157 sprintf(temp + offset, "%s\n", xattr->name);
158 offset += strlen(xattr->name) + 1;
161 mutex_unlock(&xattr_list_mutex);
162 rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
170 * evm_write_xattrs - write() for <securityfs>/evm_xattrs
171 * @file: file pointer, not actually used
172 * @buf: where to get the data from
174 * @ppos: where to start
176 * Returns number of bytes written or error code, as appropriate
178 static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
179 size_t count, loff_t *ppos)
182 struct xattr_list *xattr, *tmp;
183 struct audit_buffer *ab;
184 struct iattr newattrs;
187 if (!capable(CAP_SYS_ADMIN) || evm_xattrs_locked)
193 if (count > XATTR_NAME_MAX)
196 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_EVM_XATTR);
200 xattr = kmalloc(sizeof(struct xattr_list), GFP_KERNEL);
206 xattr->name = memdup_user_nul(buf, count);
207 if (IS_ERR(xattr->name)) {
208 err = PTR_ERR(xattr->name);
213 /* Remove any trailing newline */
214 len = strlen(xattr->name);
215 if (len && xattr->name[len-1] == '\n')
216 xattr->name[len-1] = '\0';
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;
224 err = simple_setattr(evm_xattrs, &newattrs);
226 audit_log_format(ab, "locked");
232 audit_log_format(ab, "xattr=");
233 audit_log_untrustedstring(ab, xattr->name);
235 if (strncmp(xattr->name, XATTR_SECURITY_PREFIX,
236 XATTR_SECURITY_PREFIX_LEN) != 0) {
242 * xattr_list_mutex guards against races in evm_read_xattrs().
243 * Entries are only added to the evm_config_xattrnames list
244 * and never deleted. Therefore, the list is traversed
245 * using list_for_each_entry_lockless() without holding
246 * the mutex in evm_calc_hmac_or_hash(), evm_find_protected_xattrs()
247 * and evm_protected_xattr().
249 mutex_lock(&xattr_list_mutex);
250 list_for_each_entry(tmp, &evm_config_xattrnames, list) {
251 if (strcmp(xattr->name, tmp->name) == 0) {
253 mutex_unlock(&xattr_list_mutex);
257 list_add_tail_rcu(&xattr->list, &evm_config_xattrnames);
258 mutex_unlock(&xattr_list_mutex);
260 audit_log_format(ab, " res=0");
264 audit_log_format(ab, " res=%d", err);
273 static const struct file_operations evm_xattr_ops = {
274 .read = evm_read_xattrs,
275 .write = evm_write_xattrs,
278 static int evm_init_xattrs(void)
280 evm_xattrs = securityfs_create_file("evm_xattrs", 0660, evm_dir, NULL,
282 if (!evm_xattrs || IS_ERR(evm_xattrs))
288 static int evm_init_xattrs(void)
294 int __init evm_init_secfs(void)
298 evm_dir = securityfs_create_dir("evm", integrity_dir);
299 if (!evm_dir || IS_ERR(evm_dir))
302 evm_init_tpm = securityfs_create_file("evm", 0660,
303 evm_dir, NULL, &evm_key_ops);
304 if (!evm_init_tpm || IS_ERR(evm_init_tpm)) {
309 evm_symlink = securityfs_create_symlink("evm", NULL,
310 "integrity/evm/evm", NULL);
311 if (!evm_symlink || IS_ERR(evm_symlink)) {
316 if (evm_init_xattrs() != 0) {
323 securityfs_remove(evm_symlink);
324 securityfs_remove(evm_init_tpm);
325 securityfs_remove(evm_dir);