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>
diff --git a/kernel/modsign_pubkey.c b/kernel/modsign_pubkey.c
new file mode 100644
index 0000000..4646eb2
--- /dev/null
+++ b/kernel/modsign_pubkey.c
@@ -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);