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