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
  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
  31 LIST_HEAD(ima_measurements);    /* list of all measurements */
  32
  33 /* key: inode (before secure-hashing a file) */
  34 struct 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  */
  44 static DEFINE_MUTEX(ima_extend_list_mutex);
  45
  46 /* lookup up the digest value in the hash table, and return the entry */
  47 static 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  */
  72 static 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
  93 static 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  */
 109 int 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         }
 146 out:
 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 }