MODSIGN: Provide module signing public keys to the kernel

Include a PGP keyring containing the public keys required to perform module
verification in the kernel image during build and create a special keyring
during boot which is then populated with keys of crypto type holding the public
keys found in the PGP keyring.

These can be seen by root:

[root@andromeda ~]# cat /proc/keys
07ad4ee0 I-----     1 perm 3f010000     0     0 crypto    modsign.0: RSA 87b9b3bd []
15c7f8c3 I-----     1 perm 1f030000     0     0 keyring   .module_sign: 1/4
...

It is probably worth permitting root to invalidate these keys, resulting in
their removal and preventing further modules from being loaded with that key.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
David Howells 2012-09-26 10:09:51 +01:00 committed by Rusty Russell
parent d441108c6f
commit 631cc66eb9
3 changed files with 124 additions and 2 deletions

View file

@ -55,7 +55,7 @@ obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
obj-$(CONFIG_UID16) += uid16.o
obj-$(CONFIG_MODULES) += module.o
obj-$(CONFIG_MODULE_SIG) += module_signing.o
obj-$(CONFIG_MODULE_SIG) += module_signing.o modsign_pubkey.o
obj-$(CONFIG_KALLSYMS) += kallsyms.o
obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
obj-$(CONFIG_KEXEC) += kexec.o
@ -134,6 +134,13 @@ $(obj)/timeconst.h: $(src)/timeconst.pl FORCE
$(call if_changed,timeconst)
ifeq ($(CONFIG_MODULE_SIG),y)
#
# Pull the signing certificate and any extra certificates into the kernel
#
extra_certificates:
touch $@
kernel/modsign_pubkey.o: signing_key.x509 extra_certificates
###############################################################################
#
@ -180,4 +187,4 @@ x509.genkey:
@echo >>x509.genkey "subjectKeyIdentifier=hash"
@echo >>x509.genkey "authorityKeyIdentifier=keyid"
endif
CLEAN_FILES += signing_key.priv signing_key.x509 x509.genkey
CLEAN_FILES += signing_key.priv signing_key.x509 x509.genkey extra_certificates

113
kernel/modsign_pubkey.c Normal file
View file

@ -0,0 +1,113 @@
/* Public keys for module signature verification
*
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* 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"
"modsign_certificate_list:\n"
".incbin \"signing_key.x509\"\n"
".incbin \"extra_certificates\"\n"
"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);

View file

@ -9,5 +9,7 @@
* 2 of the Licence, or (at your option) any later version.
*/
extern struct key *modsign_keyring;
extern int mod_verify_sig(const void *mod, unsigned long modlen,
const void *sig, unsigned long siglen);