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;
 66
 67	if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_INIT_HMAC))
 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	evm_init_key();
 82
 83	return count;
 84}
 85
 86static const struct file_operations evm_key_ops = {
 87	.read		= evm_read_key,
 88	.write		= evm_write_key,
 89};
 90
 91int __init evm_init_secfs(void)
 92{
 93	int error = 0;
 94
 95	evm_init_tpm = securityfs_create_file("evm", S_IRUSR | S_IRGRP,
 96					      NULL, NULL, &evm_key_ops);
 97	if (!evm_init_tpm || IS_ERR(evm_init_tpm))
 98		error = -EFAULT;
 99	return error;
100}