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