LXR linux/security/integrity/ima/ima

   1/*
   2 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
   3 *
   4 * Authors:
   5 * Serge Hallyn <serue@us.ibm.com>
   6 * Reiner Sailer <sailer@watson.ibm.com>
   7 * Mimi Zohar <zohar@us.ibm.com>
   8 *
   9 * This program is free software; you can redistribute it and/or
  10 * modify it under the terms of the GNU General Public License as
  11 * published by the Free Software Foundation, version 2 of the
  12 * License.
  13 *
  14 * File: ima_queue.c
  15 *       Implements queues that store template measurements and
  16 *       maintains aggregate over the stored measurements
  17 *       in the pre-configured TPM PCR (if available).
  18 *       The measurement list is append-only. No entry is
  19 *       ever removed or changed during the boot-cycle.
  20 */
  21
  22#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  23
  24#include <linux/module.h>
  25#include <linux/rculist.h>
  26#include <linux/slab.h>
  27#include "ima.h"
  28
  29#define AUDIT_CAUSE_LEN_MAX 32
  30
  31LIST_HEAD(ima_measurements);    /* list of all measurements */
  32
  33/* key: inode (before secure-hashing a file) */
  34struct ima_h_table ima_htable = {
  35        .len = ATOMIC_LONG_INIT(0),
  36        .violations = ATOMIC_LONG_INIT(0),
  37        .queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
  38};
  39
  40/* mutex protects atomicity of extending measurement list
  41 * and extending the TPM PCR aggregate. Since tpm_extend can take
  42 * long (and the tpm driver uses a mutex), we can't use the spinlock.
  43 */
  44static DEFINE_MUTEX(ima_extend_list_mutex);
  45
  46/* lookup up the digest value in the hash table, and return the entry */
  47static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value)
  48{
  49        struct ima_queue_entry *qe, *ret = NULL;
  50        unsigned int key;
  51        int rc;
  52
  53        key = ima_hash_key(digest_value);
  54        rcu_read_lock();
  55        hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
  56                rc = memcmp(qe->entry->digest, digest_value, TPM_DIGEST_SIZE);
  57                if (rc == 0) {
  58                        ret = qe;
  59                        break;
  60                }
  61        }
  62        rcu_read_unlock();
  63        return ret;
  64}
  65
  66/* ima_add_template_entry helper function:
  67 * - Add template entry to measurement list and hash table.
  68 *
  69 * (Called with ima_extend_list_mutex held.)
  70 */
  71static int ima_add_digest_entry(struct ima_template_entry *entry)
  72{
  73        struct ima_queue_entry *qe;
  74        unsigned int key;
  75
  76        qe = kmalloc(sizeof(*qe), GFP_KERNEL);
  77        if (qe == NULL) {
  78                pr_err("OUT OF MEMORY ERROR creating queue entry\n");
  79                return -ENOMEM;
  80        }
  81        qe->entry = entry;
  82
  83        INIT_LIST_HEAD(&qe->later);
  84        list_add_tail_rcu(&qe->later, &ima_measurements);
  85
  86        atomic_long_inc(&ima_htable.len);
  87        key = ima_hash_key(entry->digest);
  88        hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
  89        return 0;
  90}
  91
  92static int ima_pcr_extend(const u8 *hash)
  93{
  94        int result = 0;
  95
  96        if (!ima_used_chip)
  97                return result;
  98
  99        result = tpm_pcr_extend(TPM_ANY_NUM, CONFIG_IMA_MEASURE_PCR_IDX, hash);
 100        if (result != 0)
 101                pr_err("Error Communicating to TPM chip, result: %d\n", result);
 102        return result;
 103}
 104
 105/* Add template entry to the measurement list and hash table,
 106 * and extend the pcr.
 107 */
 108int ima_add_template_entry(struct ima_template_entry *entry, int violation,
 109                           const char *op, struct inode *inode,
 110                           const unsigned char *filename)
 111{
 112        u8 digest[TPM_DIGEST_SIZE];
 113        const char *audit_cause = "hash_added";
 114        char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
 115        int audit_info = 1;
 116        int result = 0, tpmresult = 0;
 117
 118        mutex_lock(&ima_extend_list_mutex);
 119        if (!violation) {
 120                memcpy(digest, entry->digest, sizeof(digest));
 121                if (ima_lookup_digest_entry(digest)) {
 122                        audit_cause = "hash_exists";
 123                        result = -EEXIST;
 124                        goto out;
 125                }
 126        }
 127
 128        result = ima_add_digest_entry(entry);
 129        if (result < 0) {
 130                audit_cause = "ENOMEM";
 131                audit_info = 0;
 132                goto out;
 133        }
 134
 135        if (violation)          /* invalidate pcr */
 136                memset(digest, 0xff, sizeof(digest));
 137
 138        tpmresult = ima_pcr_extend(digest);
 139        if (tpmresult != 0) {
 140                snprintf(tpm_audit_cause, AUDIT_CAUSE_LEN_MAX, "TPM_error(%d)",
 141                         tpmresult);
 142                audit_cause = tpm_audit_cause;
 143                audit_info = 0;
 144        }
 145out:
 146        mutex_unlock(&ima_extend_list_mutex);
 147        integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 148                            op, audit_cause, result, audit_info);
 149        return result;
 150}
 151