ima_queue.c

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/*
 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
 *
 * Authors:
 * Serge Hallyn <[email protected]>
 * Reiner Sailer <[email protected]>
 * Mimi Zohar <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, version 2 of the
 * License.
 *
 * File: ima_queue.c
 *       Implements queues that store template measurements and
 *       maintains aggregate over the stored measurements
 *       in the pre-configured TPM PCR (if available).
 *       The measurement list is append-only. No entry is
 *       ever removed or changed during the boot-cycle.
 */
#include <linux/module.h>
#include <linux/rculist.h>
#include <linux/slab.h>
#include "ima.h"

#define AUDIT_CAUSE_LEN_MAX 32

LIST_HEAD(ima_measurements);    /* list of all measurements */

/* key: inode (before secure-hashing a file) */
struct ima_h_table ima_htable = {
    .len = ATOMIC_LONG_INIT(0),
    .violations = ATOMIC_LONG_INIT(0),
    .queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
};

/* mutex protects atomicity of extending measurement list
 * and extending the TPM PCR aggregate. Since tpm_extend can take
 * long (and the tpm driver uses a mutex), we can't use the spinlock.
 */
static DEFINE_MUTEX(ima_extend_list_mutex);

/* lookup up the digest value in the hash table, and return the entry */
static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value)
{
    struct ima_queue_entry *qe, *ret = NULL;
    unsigned int key;
    struct hlist_node *pos;
    int rc;

    key = ima_hash_key(digest_value);
    rcu_read_lock();
    hlist_for_each_entry_rcu(qe, pos, &ima_htable.queue[key], hnext) {
        rc = memcmp(qe->entry->digest, digest_value, IMA_DIGEST_SIZE);
        if (rc == 0) {
            ret = qe;
            break;
        }
    }
    rcu_read_unlock();
    return ret;
}

/* ima_add_template_entry helper function:
 * - Add template entry to measurement list and hash table.
 *
 * (Called with ima_extend_list_mutex held.)
 */
static int ima_add_digest_entry(struct ima_template_entry *entry)
{
    struct ima_queue_entry *qe;
    unsigned int key;

    qe = kmalloc(sizeof(*qe), GFP_KERNEL);
    if (qe == NULL) {
        pr_err("IMA: OUT OF MEMORY ERROR creating queue entry.\n");
        return -ENOMEM;
    }
    qe->entry = entry;

    INIT_LIST_HEAD(&qe->later);
    list_add_tail_rcu(&qe->later, &ima_measurements);

    atomic_long_inc(&ima_htable.len);
    key = ima_hash_key(entry->digest);
    hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
    return 0;
}

static int ima_pcr_extend(const u8 *hash)
{
    int result = 0;

    if (!ima_used_chip)
        return result;

    result = tpm_pcr_extend(TPM_ANY_NUM, CONFIG_IMA_MEASURE_PCR_IDX, hash);
    if (result != 0)
        pr_err("IMA: Error Communicating to TPM chip, result: %d\n",
               result);
    return result;
}

/* Add template entry to the measurement list and hash table,
 * and extend the pcr.
 */
int ima_add_template_entry(struct ima_template_entry *entry, int violation,
               const char *op, struct inode *inode)
{
    u8 digest[IMA_DIGEST_SIZE];
    const char *audit_cause = "hash_added";
    char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
    int audit_info = 1;
    int result = 0, tpmresult = 0;

    mutex_lock(&ima_extend_list_mutex);
    if (!violation) {
        memcpy(digest, entry->digest, sizeof digest);
        if (ima_lookup_digest_entry(digest)) {
            audit_cause = "hash_exists";
            result = -EEXIST;
            goto out;
        }
    }

    result = ima_add_digest_entry(entry);
    if (result < 0) {
        audit_cause = "ENOMEM";
        audit_info = 0;
        goto out;
    }

    if (violation)      /* invalidate pcr */
        memset(digest, 0xff, sizeof digest);

    tpmresult = ima_pcr_extend(digest);
    if (tpmresult != 0) {
        snprintf(tpm_audit_cause, AUDIT_CAUSE_LEN_MAX, "TPM_error(%d)",
             tpmresult);
        audit_cause = tpm_audit_cause;
        audit_info = 0;
    }
out:
    mutex_unlock(&ima_extend_list_mutex);
    integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
                entry->template.file_name,
                op, audit_cause, result, audit_info);
    return result;
}