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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17
18#include <linux/uaccess.h>
19#include <linux/module.h>
20#include "evm.h"
21
22static struct dentry *evm_init_tpm;
23
24/**
25 * evm_read_key - read() for <securityfs>/evm
26 *
27 * @filp: file pointer, not actually used
28 * @buf: where to put the result
29 * @count: maximum to send along
30 * @ppos: where to start
31 *
32 * Returns number of bytes read or error code, as appropriate
33 */
34static ssize_t evm_read_key(struct file *filp, char __user *buf,
35			    size_t count, loff_t *ppos)
36{
37	char temp[80];
38	ssize_t rc;
39
40	if (*ppos != 0)
41		return 0;
42
43	sprintf(temp, "%d", evm_initialized);
44	rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
45
46	return rc;
47}
48
49/**
50 * evm_write_key - write() for <securityfs>/evm
51 * @file: file pointer, not actually used
52 * @buf: where to get the data from
53 * @count: bytes sent
54 * @ppos: where to start
55 *
56 * Used to signal that key is on the kernel key ring.
57 * - get the integrity hmac key from the kernel key ring
58 * - create list of hmac protected extended attributes
59 * Returns number of bytes written or error code, as appropriate
60 */
61static ssize_t evm_write_key(struct file *file, const char __user *buf,
62			     size_t count, loff_t *ppos)
63{
64	char temp[80];
65	int i, error;
66
67	if (!capable(CAP_SYS_ADMIN) || evm_initialized)
68		return -EPERM;
69
70	if (count >= sizeof(temp) || count == 0)
71		return -EINVAL;
72
73	if (copy_from_user(temp, buf, count) != 0)
74		return -EFAULT;
75
76	temp[count] = '\0';
77
78	if ((sscanf(temp, "%d", &i) != 1) || (i != 1))
79		return -EINVAL;
80
81	error = evm_init_key();
82	if (!error) {
83		evm_initialized = 1;
84		pr_info("initialized\n");
85	} else
86		pr_err("initialization failed\n");
87	return count;
88}
89
90static const struct file_operations evm_key_ops = {
91	.read		= evm_read_key,
92	.write		= evm_write_key,
93};
94
95int __init evm_init_secfs(void)
96{
97	int error = 0;
98
99	evm_init_tpm = securityfs_create_file("evm", S_IRUSR | S_IRGRP,
100					      NULL, NULL, &evm_key_ops);
101	if (!evm_init_tpm || IS_ERR(evm_init_tpm))
102		error = -EFAULT;
103	return error;
104}
105