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#ifdef CONFIG_IMA_KEXEC
  33static unsigned long binary_runtime_size;
  34#else
  35static unsigned long binary_runtime_size = ULONG_MAX;
  36#endif
  37
  38/* key: inode (before secure-hashing a file) */
  39struct ima_h_table ima_htable = {
  40        .len = ATOMIC_LONG_INIT(0),
  41        .violations = ATOMIC_LONG_INIT(0),
  42        .queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
  43};
  44
  45/* mutex protects atomicity of extending measurement list
  46 * and extending the TPM PCR aggregate. Since tpm_extend can take
  47 * long (and the tpm driver uses a mutex), we can't use the spinlock.
  48 */
  49static DEFINE_MUTEX(ima_extend_list_mutex);
  50
  51/* lookup up the digest value in the hash table, and return the entry */
  52static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value,
  53                                                       int pcr)
  54{
  55        struct ima_queue_entry *qe, *ret = NULL;
  56        unsigned int key;
  57        int rc;
  58
  59        key = ima_hash_key(digest_value);
  60        rcu_read_lock();
  61        hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
  62                rc = memcmp(qe->entry->digest, digest_value, TPM_DIGEST_SIZE);
  63                if ((rc == 0) && (qe->entry->pcr == pcr)) {
  64                        ret = qe;
  65                        break;
  66                }
  67        }
  68        rcu_read_unlock();
  69        return ret;
  70}
  71
  72/*
  73 * Calculate the memory required for serializing a single
  74 * binary_runtime_measurement list entry, which contains a
  75 * couple of variable length fields (e.g template name and data).
  76 */
  77static int get_binary_runtime_size(struct ima_template_entry *entry)
  78{
  79        int size = 0;
  80
  81        size += sizeof(u32);    /* pcr */
  82        size += sizeof(entry->digest);
  83        size += sizeof(int);    /* template name size field */
  84        size += strlen(entry->template_desc->name);
  85        size += sizeof(entry->template_data_len);
  86        size += entry->template_data_len;
  87        return size;
  88}
  89
  90/* ima_add_template_entry helper function:
  91 * - Add template entry to the measurement list and hash table, for
  92 *   all entries except those carried across kexec.
  93 *
  94 * (Called with ima_extend_list_mutex held.)
  95 */
  96static int ima_add_digest_entry(struct ima_template_entry *entry,
  97                                bool update_htable)
  98{
  99        struct ima_queue_entry *qe;
 100        unsigned int key;
 101
 102        qe = kmalloc(sizeof(*qe), GFP_KERNEL);
 103        if (qe == NULL) {
 104                pr_err("OUT OF MEMORY ERROR creating queue entry\n");
 105                return -ENOMEM;
 106        }
 107        qe->entry = entry;
 108
 109        INIT_LIST_HEAD(&qe->later);
 110        list_add_tail_rcu(&qe->later, &ima_measurements);
 111
 112        atomic_long_inc(&ima_htable.len);
 113        if (update_htable) {
 114                key = ima_hash_key(entry->digest);
 115                hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
 116        }
 117
 118        if (binary_runtime_size != ULONG_MAX) {
 119                int size;
 120
 121                size = get_binary_runtime_size(entry);
 122                binary_runtime_size = (binary_runtime_size < ULONG_MAX - size) ?
 123                     binary_runtime_size + size : ULONG_MAX;
 124        }
 125        return 0;
 126}
 127
 128/*
 129 * Return the amount of memory required for serializing the
 130 * entire binary_runtime_measurement list, including the ima_kexec_hdr
 131 * structure.
 132 */
 133unsigned long ima_get_binary_runtime_size(void)
 134{
 135        if (binary_runtime_size >= (ULONG_MAX - sizeof(struct ima_kexec_hdr)))
 136                return ULONG_MAX;
 137        else
 138                return binary_runtime_size + sizeof(struct ima_kexec_hdr);
 139};
 140
 141static int ima_pcr_extend(const u8 *hash, int pcr)
 142{
 143        int result = 0;
 144
 145        if (!ima_used_chip)
 146                return result;
 147
 148        result = tpm_pcr_extend(TPM_ANY_NUM, pcr, hash);
 149        if (result != 0)
 150                pr_err("Error Communicating to TPM chip, result: %d\n", result);
 151        return result;
 152}
 153
 154/*
 155 * Add template entry to the measurement list and hash table, and
 156 * extend the pcr.
 157 *
 158 * On systems which support carrying the IMA measurement list across
 159 * kexec, maintain the total memory size required for serializing the
 160 * binary_runtime_measurements.
 161 */
 162int ima_add_template_entry(struct ima_template_entry *entry, int violation,
 163                           const char *op, struct inode *inode,
 164                           const unsigned char *filename)
 165{
 166        u8 digest[TPM_DIGEST_SIZE];
 167        const char *audit_cause = "hash_added";
 168        char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
 169        int audit_info = 1;
 170        int result = 0, tpmresult = 0;
 171
 172        mutex_lock(&ima_extend_list_mutex);
 173        if (!violation) {
 174                memcpy(digest, entry->digest, sizeof(digest));
 175                if (ima_lookup_digest_entry(digest, entry->pcr)) {
 176                        audit_cause = "hash_exists";
 177                        result = -EEXIST;
 178                        goto out;
 179                }
 180        }
 181
 182        result = ima_add_digest_entry(entry, 1);
 183        if (result < 0) {
 184                audit_cause = "ENOMEM";
 185                audit_info = 0;
 186                goto out;
 187        }
 188
 189        if (violation)          /* invalidate pcr */
 190                memset(digest, 0xff, sizeof(digest));
 191
 192        tpmresult = ima_pcr_extend(digest, entry->pcr);
 193        if (tpmresult != 0) {
 194                snprintf(tpm_audit_cause, AUDIT_CAUSE_LEN_MAX, "TPM_error(%d)",
 195                         tpmresult);
 196                audit_cause = tpm_audit_cause;
 197                audit_info = 0;
 198        }
 199out:
 200        mutex_unlock(&ima_extend_list_mutex);
 201        integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 202                            op, audit_cause, result, audit_info);
 203        return result;
 204}
 205
 206int ima_restore_measurement_entry(struct ima_template_entry *entry)
 207{
 208        int result = 0;
 209
 210        mutex_lock(&ima_extend_list_mutex);
 211        result = ima_add_digest_entry(entry, 0);
 212        mutex_unlock(&ima_extend_list_mutex);
 213        return result;
 214}
 215