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Date: Fri, 11 May 2012 00:43:27 +0100
From: David Howells <dhowells@...hat.com>
To: rusty@...tcorp.com.au
Cc: kyle@...artin.ca, linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org, keyrings@...ux-nfs.org,
David Howells <dhowells@...hat.com>
Subject: [PATCH 24/29] MODSIGN: Provide module signing public keys to the
kernel [ver #4]
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@...romeda ~]# 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@...hat.com>
---
kernel/Makefile | 3 +-
kernel/modsign-pubkey.c | 74 +++++++++++++++++++++++++++++++++++++++++++
kernel/module-verify-defs.h | 4 ++
kernel/module-verify.c | 2 -
4 files changed, 80 insertions(+), 3 deletions(-)
create mode 100644 kernel/modsign-pubkey.c
diff --git a/kernel/Makefile b/kernel/Makefile
index 7608053..986ed7f 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -51,7 +51,8 @@ obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
obj-$(CONFIG_UID16) += uid16.o
obj-$(CONFIG_MODULES) += module.o
-obj-$(CONFIG_MODULE_SIG) += module-verify.o
+obj-$(CONFIG_MODULE_SIG) += module-verify.o modsign-pubkey.o
+kernel/modsign-pubkey.o: modsign.pub
obj-$(CONFIG_KALLSYMS) += kallsyms.o
obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
obj-$(CONFIG_KEXEC) += kexec.o
diff --git a/kernel/modsign-pubkey.c b/kernel/modsign-pubkey.c
new file mode 100644
index 0000000..2ada460
--- /dev/null
+++ b/kernel/modsign-pubkey.c
@@ -0,0 +1,74 @@
+/* Public keys for module signature verification
+ *
+ * Copyright (C) 2011 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@...hat.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 <keys/crypto-type.h>
+#include "module-verify-defs.h"
+
+struct key *modsign_keyring;
+
+extern __initdata const u8 modsign_public_keys[];
+extern __initdata const u8 modsign_public_keys_end[];
+asm(".section .init.data,\"aw\"\n"
+ "modsign_public_keys:\n"
+ ".incbin \"modsign.pub\"\n"
+ "modsign_public_keys_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",
+ 0, 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 modsign_pubkey_init(void)
+{
+ pr_notice("Load module verification keys\n");
+
+ if (preload_pgp_keys(modsign_public_keys,
+ modsign_public_keys_end - modsign_public_keys,
+ modsign_keyring, "modsign.") < 0)
+ panic("Can't load module signing keys\n");
+
+ return 0;
+}
+late_initcall(modsign_pubkey_init);
diff --git a/kernel/module-verify-defs.h b/kernel/module-verify-defs.h
index 292d2ba..45bea45 100644
--- a/kernel/module-verify-defs.h
+++ b/kernel/module-verify-defs.h
@@ -11,6 +11,10 @@
#ifdef CONFIG_MODULE_SIG
+#include <linux/module.h>
+
+extern struct key *modsign_keyring;
+
/*
* Internal state
*/
diff --git a/kernel/module-verify.c b/kernel/module-verify.c
index 0a3eb4b..b1c1d4c 100644
--- a/kernel/module-verify.c
+++ b/kernel/module-verify.c
@@ -27,8 +27,6 @@
#include <linux/slab.h>
#include <linux/elf.h>
#include <linux/elfnote.h>
-#include <linux/sched.h>
-#include <linux/cred.h>
#include <linux/modsign.h>
#include <linux/moduleparam.h>
#include <keys/crypto-type.h>
--
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