security/integrity/evm/evm_secfs.c

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