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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17
  18 #include <linux/uaccess.h>
  19 #include <linux/module.h>
  20 #include "evm.h"
  21
  22 static 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  */
  34 static 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  */
  61 static 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
  90 static const struct file_operations evm_key_ops = {
  91         .read           = evm_read_key,
  92         .write          = evm_write_key,
  93 };
  94
  95 int __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 }