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 #ifdef CONFIG_IMA_KEXEC
  33 static unsigned long binary_runtime_size;
  34 #else
  35 static unsigned long binary_runtime_size = ULONG_MAX;
  36 #endif
  37
  38 /* key: inode (before secure-hashing a file) */
  39 struct 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  */
  49 static DEFINE_MUTEX(ima_extend_list_mutex);
  50
  51 /* lookup up the digest value in the hash table, and return the entry */
  52 static 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  */
  77 static 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) + 1;
  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  */
  96 static 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  */
 133 unsigned 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
 141 static 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  */
 162 int 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         }
 199 out:
 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
 206 int 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 }