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)
76 if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP_COMPLETE))
79 ret = kstrtoint_from_user(buf, count, 0, &i);
84 /* Reject invalid values */
85 if (!i || (i & ~EVM_INIT_MASK) != 0)
88 /* Don't allow a request to freshly enable metadata writes if
91 if ((i & EVM_ALLOW_METADATA_WRITES) &&
92 ((evm_initialized & EVM_KEY_MASK) != 0) &&
93 !(evm_initialized & EVM_ALLOW_METADATA_WRITES))
96 if (i & EVM_INIT_HMAC) {
100 /* Forbid further writes after the symmetric key is loaded */
101 i |= EVM_SETUP_COMPLETE;
104 evm_initialized |= i;
106 /* Don't allow protected metadata modification if a symmetric key
109 if (evm_initialized & EVM_INIT_HMAC)
110 evm_initialized &= ~(EVM_ALLOW_METADATA_WRITES);
115 static const struct file_operations evm_key_ops = {
116 .read = evm_read_key,
117 .write = evm_write_key,
120 #ifdef CONFIG_EVM_ADD_XATTRS
122 * evm_read_xattrs - read() for <securityfs>/evm_xattrs
124 * @filp: file pointer, not actually used
125 * @buf: where to put the result
126 * @count: maximum to send along
127 * @ppos: where to start
129 * Returns number of bytes read or error code, as appropriate
131 static ssize_t evm_read_xattrs(struct file *filp, char __user *buf,
132 size_t count, loff_t *ppos)
136 ssize_t rc, size = 0;
137 struct xattr_list *xattr;
142 rc = mutex_lock_interruptible(&xattr_list_mutex);
146 list_for_each_entry(xattr, &evm_config_xattrnames, list)
147 size += strlen(xattr->name) + 1;
149 temp = kmalloc(size + 1, GFP_KERNEL);
151 mutex_unlock(&xattr_list_mutex);
155 list_for_each_entry(xattr, &evm_config_xattrnames, list) {
156 sprintf(temp + offset, "%s\n", xattr->name);
157 offset += strlen(xattr->name) + 1;
160 mutex_unlock(&xattr_list_mutex);
161 rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
169 * evm_write_xattrs - write() for <securityfs>/evm_xattrs
170 * @file: file pointer, not actually used
171 * @buf: where to get the data from
173 * @ppos: where to start
175 * Returns number of bytes written or error code, as appropriate
177 static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
178 size_t count, loff_t *ppos)
181 struct xattr_list *xattr, *tmp;
182 struct audit_buffer *ab;
183 struct iattr newattrs;
186 if (!capable(CAP_SYS_ADMIN) || evm_xattrs_locked)
192 if (count > XATTR_NAME_MAX)
195 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_EVM_XATTR);
199 xattr = kmalloc(sizeof(struct xattr_list), GFP_KERNEL);
205 xattr->name = memdup_user_nul(buf, count);
206 if (IS_ERR(xattr->name)) {
207 err = PTR_ERR(xattr->name);
212 /* Remove any trailing newline */
213 len = strlen(xattr->name);
214 if (len && xattr->name[len-1] == '\n')
215 xattr->name[len-1] = '\0';
217 if (strcmp(xattr->name, ".") == 0) {
218 evm_xattrs_locked = 1;
219 newattrs.ia_mode = S_IFREG | 0440;
220 newattrs.ia_valid = ATTR_MODE;
221 inode = evm_xattrs->d_inode;
223 err = simple_setattr(evm_xattrs, &newattrs);
225 audit_log_format(ab, "locked");
231 audit_log_format(ab, "xattr=");
232 audit_log_untrustedstring(ab, xattr->name);
234 if (strncmp(xattr->name, XATTR_SECURITY_PREFIX,
235 XATTR_SECURITY_PREFIX_LEN) != 0) {
240 /* Guard against races in evm_read_xattrs */
241 mutex_lock(&xattr_list_mutex);
242 list_for_each_entry(tmp, &evm_config_xattrnames, list) {
243 if (strcmp(xattr->name, tmp->name) == 0) {
245 mutex_unlock(&xattr_list_mutex);
249 list_add_tail_rcu(&xattr->list, &evm_config_xattrnames);
250 mutex_unlock(&xattr_list_mutex);
252 audit_log_format(ab, " res=0");
256 audit_log_format(ab, " res=%d", err);
265 static const struct file_operations evm_xattr_ops = {
266 .read = evm_read_xattrs,
267 .write = evm_write_xattrs,
270 static int evm_init_xattrs(void)
272 evm_xattrs = securityfs_create_file("evm_xattrs", 0660, evm_dir, NULL,
274 if (!evm_xattrs || IS_ERR(evm_xattrs))
280 static int evm_init_xattrs(void)
286 int __init evm_init_secfs(void)
290 evm_dir = securityfs_create_dir("evm", integrity_dir);
291 if (!evm_dir || IS_ERR(evm_dir))
294 evm_init_tpm = securityfs_create_file("evm", 0660,
295 evm_dir, NULL, &evm_key_ops);
296 if (!evm_init_tpm || IS_ERR(evm_init_tpm)) {
301 evm_symlink = securityfs_create_symlink("evm", NULL,
302 "integrity/evm/evm", NULL);
303 if (!evm_symlink || IS_ERR(evm_symlink)) {
308 if (evm_init_xattrs() != 0) {
315 securityfs_remove(evm_symlink);
316 securityfs_remove(evm_init_tpm);
317 securityfs_remove(evm_dir);