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                                                       int pcr)
  49{
  50        struct ima_queue_entry *qe, *ret = NULL;
  51        unsigned int key;
  52        int rc;
  53
  54        key = ima_hash_key(digest_value);
  55        rcu_read_lock();
  56        hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
  57                rc = memcmp(qe->entry->digest, digest_value, TPM_DIGEST_SIZE);
  58                if ((rc == 0) && (qe->entry->pcr == pcr)) {
  59                        ret = qe;
  60                        break;
  61                }
  62        }
  63        rcu_read_unlock();
  64        return ret;
  65}
  66
  67/* ima_add_template_entry helper function:
  68 * - Add template entry to measurement list and hash table.
  69 *
  70 * (Called with ima_extend_list_mutex held.)
  71 */
  72static int ima_add_digest_entry(struct ima_template_entry *entry)
  73{
  74        struct ima_queue_entry *qe;
  75        unsigned int key;
  76
  77        qe = kmalloc(sizeof(*qe), GFP_KERNEL);
  78        if (qe == NULL) {
  79                pr_err("OUT OF MEMORY ERROR creating queue entry\n");
  80                return -ENOMEM;
  81        }
  82        qe->entry = entry;
  83
  84        INIT_LIST_HEAD(&qe->later);
  85        list_add_tail_rcu(&qe->later, &ima_measurements);
  86
  87        atomic_long_inc(&ima_htable.len);
  88        key = ima_hash_key(entry->digest);
  89        hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
  90        return 0;
  91}
  92
  93static int ima_pcr_extend(const u8 *hash, int pcr)
  94{
  95        int result = 0;
  96
  97        if (!ima_used_chip)
  98                return result;
  99
 100        result = tpm_pcr_extend(TPM_ANY_NUM, pcr, hash);
 101        if (result != 0)
 102                pr_err("Error Communicating to TPM chip, result: %d\n", result);
 103        return result;
 104}
 105
 106/* Add template entry to the measurement list and hash table,
 107 * and extend the pcr.
 108 */
 109int ima_add_template_entry(struct ima_template_entry *entry, int violation,
 110                           const char *op, struct inode *inode,
 111                           const unsigned char *filename)
 112{
 113        u8 digest[TPM_DIGEST_SIZE];
 114        const char *audit_cause = "hash_added";
 115        char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
 116        int audit_info = 1;
 117        int result = 0, tpmresult = 0;
 118
 119        mutex_lock(&ima_extend_list_mutex);
 120        if (!violation) {
 121                memcpy(digest, entry->digest, sizeof(digest));
 122                if (ima_lookup_digest_entry(digest, entry->pcr)) {
 123                        audit_cause = "hash_exists";
 124                        result = -EEXIST;
 125                        goto out;
 126                }
 127        }
 128
 129        result = ima_add_digest_entry(entry);
 130        if (result < 0) {
 131                audit_cause = "ENOMEM";
 132                audit_info = 0;
 133                goto out;
 134        }
 135
 136        if (violation)          /* invalidate pcr */
 137                memset(digest, 0xff, sizeof(digest));
 138
 139        tpmresult = ima_pcr_extend(digest, entry->pcr);
 140        if (tpmresult != 0) {
 141                snprintf(tpm_audit_cause, AUDIT_CAUSE_LEN_MAX, "TPM_error(%d)",
 142                         tpmresult);
 143                audit_cause = tpm_audit_cause;
 144                audit_info = 0;
 145        }
 146out:
 147        mutex_unlock(&ima_extend_list_mutex);
 148        integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 149                            op, audit_cause, result, audit_info);
 150        return result;
 151}
 152