modsign_pubkey.c

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/* Public keys for module signature verification
 *
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/err.h>
#include <keys/asymmetric-type.h>
#include "module-internal.h"

struct key *modsign_keyring;

extern __initdata const u8 modsign_certificate_list[];
extern __initdata const u8 modsign_certificate_list_end[];
asm(".section .init.data,\"aw\"\n"
    SYMBOL_PREFIX "modsign_certificate_list:\n"
    ".incbin \"signing_key.x509\"\n"
    ".incbin \"extra_certificates\"\n"
    SYMBOL_PREFIX "modsign_certificate_list_end:"
    );

/*
 * We need to make sure ccache doesn't cache the .o file as it doesn't notice
 * if modsign.pub changes.
 */
static __initdata const char annoy_ccache[] = __TIME__ "foo";

/*
 * Load the compiled-in keys
 */
static __init int module_verify_init(void)
{
    pr_notice("Initialise module verification\n");

    modsign_keyring = key_alloc(&key_type_keyring, ".module_sign",
                    KUIDT_INIT(0), KGIDT_INIT(0),
                    current_cred(),
                    (KEY_POS_ALL & ~KEY_POS_SETATTR) |
                    KEY_USR_VIEW | KEY_USR_READ,
                    KEY_ALLOC_NOT_IN_QUOTA);
    if (IS_ERR(modsign_keyring))
        panic("Can't allocate module signing keyring\n");

    if (key_instantiate_and_link(modsign_keyring, NULL, 0, NULL, NULL) < 0)
        panic("Can't instantiate module signing keyring\n");

    return 0;
}

/*
 * Must be initialised before we try and load the keys into the keyring.
 */
device_initcall(module_verify_init);

/*
 * Load the compiled-in keys
 */
static __init int load_module_signing_keys(void)
{
    key_ref_t key;
    const u8 *p, *end;
    size_t plen;

    pr_notice("Loading module verification certificates\n");

    end = modsign_certificate_list_end;
    p = modsign_certificate_list;
    while (p < end) {
        /* Each cert begins with an ASN.1 SEQUENCE tag and must be more
         * than 256 bytes in size.
         */
        if (end - p < 4)
            goto dodgy_cert;
        if (p[0] != 0x30 &&
            p[1] != 0x82)
            goto dodgy_cert;
        plen = (p[2] << 8) | p[3];
        plen += 4;
        if (plen > end - p)
            goto dodgy_cert;

        key = key_create_or_update(make_key_ref(modsign_keyring, 1),
                       "asymmetric",
                       NULL,
                       p,
                       plen,
                       (KEY_POS_ALL & ~KEY_POS_SETATTR) |
                       KEY_USR_VIEW,
                       KEY_ALLOC_NOT_IN_QUOTA);
        if (IS_ERR(key))
            pr_err("MODSIGN: Problem loading in-kernel X.509 certificate (%ld)\n",
                   PTR_ERR(key));
        else
            pr_notice("MODSIGN: Loaded cert '%s'\n",
                  key_ref_to_ptr(key)->description);
        p += plen;
    }

    return 0;

dodgy_cert:
    pr_err("MODSIGN: Problem parsing in-kernel X.509 certificate list\n");
    return 0;
}
late_initcall(load_module_signing_keys);