security/integrity/ima/ima_queue.c

   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 #include <linux/module.h>
  22 #include <linux/rculist.h>
  23 #include <linux/slab.h>
  24 #include "ima.h"
  25
  26 #define AUDIT_CAUSE_LEN_MAX 32
  27
  28 LIST_HEAD(ima_measurements);    /* list of all measurements */
  29
  30 /* key: inode (before secure-hashing a file) */
  31 struct ima_h_table ima_htable = {
  32         .len = ATOMIC_LONG_INIT(0),
  33         .violations = ATOMIC_LONG_INIT(0),
  34         .queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
  35 };
  36
  37 /* mutex protects atomicity of extending measurement list
  38  * and extending the TPM PCR aggregate. Since tpm_extend can take
  39  * long (and the tpm driver uses a mutex), we can't use the spinlock.
  40  */
  41 static DEFINE_MUTEX(ima_extend_list_mutex);
  42
  43 /* lookup up the digest value in the hash table, and return the entry */
  44 static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value)
  45 {
  46         struct ima_queue_entry *qe, *ret = NULL;
  47         unsigned int key;
  48         struct hlist_node *pos;
  49         int rc;
  50
  51         key = ima_hash_key(digest_value);
  52         rcu_read_lock();
  53         hlist_for_each_entry_rcu(qe, pos, &ima_htable.queue[key], hnext) {
  54                 rc = memcmp(qe->entry->digest, digest_value, IMA_DIGEST_SIZE);
  55                 if (rc == 0) {
  56                         ret = qe;
  57                         break;
  58                 }
  59         }
  60         rcu_read_unlock();
  61         return ret;
  62 }
  63
  64 /* ima_add_template_entry helper function:
  65  * - Add template entry to measurement list and hash table.
  66  *
  67  * (Called with ima_extend_list_mutex held.)
  68  */
  69 static int ima_add_digest_entry(struct ima_template_entry *entry)
  70 {
  71         struct ima_queue_entry *qe;
  72         unsigned int key;
  73
  74         qe = kmalloc(sizeof(*qe), GFP_KERNEL);
  75         if (qe == NULL) {
  76                 pr_err("IMA: OUT OF MEMORY ERROR creating queue entry.\n");
  77                 return -ENOMEM;
  78         }
  79         qe->entry = entry;
  80
  81         INIT_LIST_HEAD(&qe->later);
  82         list_add_tail_rcu(&qe->later, &ima_measurements);
  83
  84         atomic_long_inc(&ima_htable.len);
  85         key = ima_hash_key(entry->digest);
  86         hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
  87         return 0;
  88 }
  89
  90 static int ima_pcr_extend(const u8 *hash)
  91 {
  92         int result = 0;
  93
  94         if (!ima_used_chip)
  95                 return result;
  96
  97         result = tpm_pcr_extend(TPM_ANY_NUM, CONFIG_IMA_MEASURE_PCR_IDX, hash);
  98         if (result != 0)
  99                 pr_err("IMA: Error Communicating to TPM chip, result: %d\n",
 100                        result);
 101         return result;
 102 }
 103
 104 /* Add template entry to the measurement list and hash table,
 105  * and extend the pcr.
 106  */
 107 int ima_add_template_entry(struct ima_template_entry *entry, int violation,
 108                            const char *op, struct inode *inode)
 109 {
 110         u8 digest[IMA_DIGEST_SIZE];
 111         const char *audit_cause = "hash_added";
 112         char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
 113         int audit_info = 1;
 114         int result = 0, tpmresult = 0;
 115
 116         mutex_lock(&ima_extend_list_mutex);
 117         if (!violation) {
 118                 memcpy(digest, entry->digest, sizeof digest);
 119                 if (ima_lookup_digest_entry(digest)) {
 120                         audit_cause = "hash_exists";
 121                         result = -EEXIST;
 122                         goto out;
 123                 }
 124         }
 125
 126         result = ima_add_digest_entry(entry);
 127         if (result < 0) {
 128                 audit_cause = "ENOMEM";
 129                 audit_info = 0;
 130                 goto out;
 131         }
 132
 133         if (violation)          /* invalidate pcr */
 134                 memset(digest, 0xff, sizeof digest);
 135
 136         tpmresult = ima_pcr_extend(digest);
 137         if (tpmresult != 0) {
 138                 snprintf(tpm_audit_cause, AUDIT_CAUSE_LEN_MAX, "TPM_error(%d)",
 139                          tpmresult);
 140                 audit_cause = tpm_audit_cause;
 141                 audit_info = 0;
 142         }
 143 out:
 144         mutex_unlock(&ima_extend_list_mutex);
 145         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
 146                             entry->template.file_name,
 147                             op, audit_cause, result, audit_info);
 148         return result;
 149 }