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kernel/modsign-uefi.patch
Josh Boyer c9d9c5a37e Rework Secure Boot support to use the secure_modules approach 
- Drop pekey
2013-08-30 11:32:55 -04:00

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From cff9d37c9529fca5ff853f0050c7f0de0e819ea7 Mon Sep 17 00:00:00 2001
From: Dave Howells <dhowells@redhat.com>
Date: Tue, 23 Oct 2012 09:30:54 -0400
Subject: [PATCH 1/4] Add EFI signature data types
Add the data types that are used for containing hashes, keys and certificates
for cryptographic verification.
Signed-off-by: David Howells <dhowells@redhat.com>
---
include/linux/efi.h | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/include/linux/efi.h b/include/linux/efi.h
index eed2202..1da1b3c 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -389,6 +389,12 @@ typedef efi_status_t efi_query_variable_store_t(u32 attributes, unsigned long si
#define EFI_FILE_SYSTEM_GUID \
EFI_GUID( 0x964e5b22, 0x6459, 0x11d2, 0x8e, 0x39, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b )
+#define EFI_CERT_SHA256_GUID \
+ EFI_GUID( 0xc1c41626, 0x504c, 0x4092, 0xac, 0xa9, 0x41, 0xf9, 0x36, 0x93, 0x43, 0x28 )
+
+#define EFI_CERT_X509_GUID \
+ EFI_GUID( 0xa5c059a1, 0x94e4, 0x4aa7, 0x87, 0xb5, 0xab, 0x15, 0x5c, 0x2b, 0xf0, 0x72 )
+
typedef struct {
efi_guid_t guid;
u64 table;
@@ -524,6 +530,20 @@ typedef struct {
#define EFI_INVALID_TABLE_ADDR (~0UL)
+typedef struct {
+ efi_guid_t signature_owner;
+ u8 signature_data[];
+} efi_signature_data_t;
+
+typedef struct {
+ efi_guid_t signature_type;
+ u32 signature_list_size;
+ u32 signature_header_size;
+ u32 signature_size;
+ u8 signature_header[];
+ /* efi_signature_data_t signatures[][] */
+} efi_signature_list_t;
+
/*
* All runtime access to EFI goes through this structure:
*/
--
1.8.3.1
From 2ce1c1d0d7110c4b06d65e4c8506f6c54aa72628 Mon Sep 17 00:00:00 2001
From: Dave Howells <dhowells@redhat.com>
Date: Tue, 23 Oct 2012 09:36:28 -0400
Subject: [PATCH 2/4] Add an EFI signature blob parser and key loader.
X.509 certificates are loaded into the specified keyring as asymmetric type
keys.
Signed-off-by: David Howells <dhowells@redhat.com>
---
crypto/asymmetric_keys/Kconfig | 8 +++
crypto/asymmetric_keys/Makefile | 1 +
crypto/asymmetric_keys/efi_parser.c | 108 ++++++++++++++++++++++++++++++++++++
include/linux/efi.h | 4 ++
4 files changed, 121 insertions(+)
create mode 100644 crypto/asymmetric_keys/efi_parser.c
diff --git a/crypto/asymmetric_keys/Kconfig b/crypto/asymmetric_keys/Kconfig
index 6d2c2ea..ace9c30 100644
--- a/crypto/asymmetric_keys/Kconfig
+++ b/crypto/asymmetric_keys/Kconfig
@@ -35,4 +35,12 @@ config X509_CERTIFICATE_PARSER
data and provides the ability to instantiate a crypto key from a
public key packet found inside the certificate.
+config EFI_SIGNATURE_LIST_PARSER
+ bool "EFI signature list parser"
+ depends on EFI
+ select X509_CERTIFICATE_PARSER
+ help
+ This option provides support for parsing EFI signature lists for
+ X.509 certificates and turning them into keys.
+
endif # ASYMMETRIC_KEY_TYPE
diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile
index 0727204..cd8388e 100644
--- a/crypto/asymmetric_keys/Makefile
+++ b/crypto/asymmetric_keys/Makefile
@@ -8,6 +8,7 @@ asymmetric_keys-y := asymmetric_type.o signature.o
obj-$(CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += public_key.o
obj-$(CONFIG_PUBLIC_KEY_ALGO_RSA) += rsa.o
+obj-$(CONFIG_EFI_SIGNATURE_LIST_PARSER) += efi_parser.o
#
# X.509 Certificate handling
diff --git a/crypto/asymmetric_keys/efi_parser.c b/crypto/asymmetric_keys/efi_parser.c
new file mode 100644
index 0000000..636feb1
--- /dev/null
+++ b/crypto/asymmetric_keys/efi_parser.c
@@ -0,0 +1,108 @@
+/* EFI signature/key/certificate list parser
+ *
+ * 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.
+ */
+
+#define pr_fmt(fmt) "EFI: "fmt
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/err.h>
+#include <linux/efi.h>
+#include <keys/asymmetric-type.h>
+
+static __initdata efi_guid_t efi_cert_x509_guid = EFI_CERT_X509_GUID;
+
+/**
+ * parse_efi_signature_list - Parse an EFI signature list for certificates
+ * @data: The data blob to parse
+ * @size: The size of the data blob
+ * @keyring: The keyring to add extracted keys to
+ */
+int __init parse_efi_signature_list(const void *data, size_t size, struct key *keyring)
+{
+ unsigned offs = 0;
+ size_t lsize, esize, hsize, elsize;
+
+ pr_devel("-->%s(,%zu)\n", __func__, size);
+
+ while (size > 0) {
+ efi_signature_list_t list;
+ const efi_signature_data_t *elem;
+ key_ref_t key;
+
+ if (size < sizeof(list))
+ return -EBADMSG;
+
+ memcpy(&list, data, sizeof(list));
+ pr_devel("LIST[%04x] guid=%pUl ls=%x hs=%x ss=%x\n",
+ offs,
+ list.signature_type.b, list.signature_list_size,
+ list.signature_header_size, list.signature_size);
+
+ lsize = list.signature_list_size;
+ hsize = list.signature_header_size;
+ esize = list.signature_size;
+ elsize = lsize - sizeof(list) - hsize;
+
+ if (lsize > size) {
+ pr_devel("<--%s() = -EBADMSG [overrun @%x]\n",
+ __func__, offs);
+ return -EBADMSG;
+ }
+ if (lsize < sizeof(list) ||
+ lsize - sizeof(list) < hsize ||
+ esize < sizeof(*elem) ||
+ elsize < esize ||
+ elsize % esize != 0) {
+ pr_devel("- bad size combo @%x\n", offs);
+ return -EBADMSG;
+ }
+
+ if (efi_guidcmp(list.signature_type, efi_cert_x509_guid) != 0) {
+ data += lsize;
+ size -= lsize;
+ offs += lsize;
+ continue;
+ }
+
+ data += sizeof(list) + hsize;
+ size -= sizeof(list) + hsize;
+ offs += sizeof(list) + hsize;
+
+ for (; elsize > 0; elsize -= esize) {
+ elem = data;
+
+ pr_devel("ELEM[%04x]\n", offs);
+
+ key = key_create_or_update(
+ make_key_ref(keyring, 1),
+ "asymmetric",
+ NULL,
+ &elem->signature_data,
+ esize - sizeof(*elem),
+ (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+ KEY_USR_VIEW,
+ KEY_ALLOC_NOT_IN_QUOTA);
+
+ if (IS_ERR(key))
+ pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
+ PTR_ERR(key));
+ else
+ pr_notice("Loaded cert '%s' linked to '%s'\n",
+ key_ref_to_ptr(key)->description,
+ keyring->description);
+
+ data += esize;
+ size -= esize;
+ offs += esize;
+ }
+ }
+
+ return 0;
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 1da1b3c..42a1d25 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -619,6 +619,10 @@ extern int efi_set_rtc_mmss(const struct timespec *now);
extern void efi_reserve_boot_services(void);
extern struct efi_memory_map memmap;
+struct key;
+extern int __init parse_efi_signature_list(const void *data, size_t size,
+ struct key *keyring);
+
/**
* efi_range_is_wc - check the WC bit on an address range
* @start: starting kvirt address
--
1.8.3.1
From 0e4e8acfd0932bbf6b02112218092c810d9469a5 Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer@fedoraproject.org>
Date: Fri, 26 Oct 2012 12:36:24 -0400
Subject: [PATCH 3/4] MODSIGN: Add module certificate blacklist keyring
This adds an additional keyring that is used to store certificates that
are blacklisted. This keyring is searched first when loading signed modules
and if the module's certificate is found, it will refuse to load. This is
useful in cases where third party certificates are used for module signing.
Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
---
init/Kconfig | 8 ++++++++
kernel/modsign_pubkey.c | 14 ++++++++++++++
kernel/module-internal.h | 3 +++
kernel/module_signing.c | 12 ++++++++++++
4 files changed, 37 insertions(+)
diff --git a/init/Kconfig b/init/Kconfig
index fed81b5..b4fa2d1 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1772,6 +1772,14 @@ config MODULE_SIG_ALL
comment "Do not forget to sign required modules with scripts/sign-file"
depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
+config MODULE_SIG_BLACKLIST
+ bool "Support for blacklisting module signature certificates"
+ depends on MODULE_SIG
+ help
+ This adds support for keeping a blacklist of certificates that
+ should not pass module signature verification. If a module is
+ signed with something in this keyring, the load will be rejected.
+
choice
prompt "Which hash algorithm should modules be signed with?"
depends on MODULE_SIG
diff --git a/kernel/modsign_pubkey.c b/kernel/modsign_pubkey.c
index 2b6e699..4cd408d 100644
--- a/kernel/modsign_pubkey.c
+++ b/kernel/modsign_pubkey.c
@@ -17,6 +17,9 @@
#include "module-internal.h"
struct key *modsign_keyring;
+#ifdef CONFIG_MODULE_SIG_BLACKLIST
+struct key *modsign_blacklist;
+#endif
extern __initdata const u8 modsign_certificate_list[];
extern __initdata const u8 modsign_certificate_list_end[];
@@ -43,6 +46,17 @@ static __init int module_verify_init(void)
if (IS_ERR(modsign_keyring))
panic("Can't allocate module signing keyring\n");
+#ifdef CONFIG_MODULE_SIG_BLACKLIST
+ modsign_blacklist = keyring_alloc(".modsign_blacklist",
+ 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, NULL);
+ if (IS_ERR(modsign_blacklist))
+ panic("Can't allocate module signing blacklist keyring\n");
+#endif
+
return 0;
}
diff --git a/kernel/module-internal.h b/kernel/module-internal.h
index 24f9247..51a8380 100644
--- a/kernel/module-internal.h
+++ b/kernel/module-internal.h
@@ -10,5 +10,8 @@
*/
extern struct key *modsign_keyring;
+#ifdef CONFIG_MODULE_SIG_BLACKLIST
+extern struct key *modsign_blacklist;
+#endif
extern int mod_verify_sig(const void *mod, unsigned long *_modlen);
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index f2970bd..5423195 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -157,6 +157,18 @@ static struct key *request_asymmetric_key(const char *signer, size_t signer_len,
pr_debug("Look up: \"%s\"\n", id);
+#ifdef CONFIG_MODULE_SIG_BLACKLIST
+ key = keyring_search(make_key_ref(modsign_blacklist, 1),
+ &key_type_asymmetric, id);
+ if (!IS_ERR(key)) {
+ /* module is signed with a cert in the blacklist. reject */
+ pr_err("Module key '%s' is in blacklist\n", id);
+ key_ref_put(key);
+ kfree(id);
+ return ERR_PTR(-EKEYREJECTED);
+ }
+#endif
+
key = keyring_search(make_key_ref(modsign_keyring, 1),
&key_type_asymmetric, id);
if (IS_ERR(key))
--
1.8.3.1
From c558b46370e850851a94795df67b7c57aecc48ea Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer@fedoraproject.org>
Date: Fri, 26 Oct 2012 12:42:16 -0400
Subject: [PATCH 4/4] MODSIGN: Import certificates from UEFI Secure Boot
Secure Boot stores a list of allowed certificates in the 'db' variable.
This imports those certificates into the module signing keyring. This
allows for a third party signing certificate to be used in conjunction
with signed modules. By importing the public certificate into the 'db'
variable, a user can allow a module signed with that certificate to
load. The shim UEFI bootloader has a similar certificate list stored
in the 'MokListRT' variable. We import those as well.
In the opposite case, Secure Boot maintains a list of disallowed
certificates in the 'dbx' variable. We load those certificates into
the newly introduced module blacklist keyring and forbid any module
signed with those from loading.
Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
---
include/linux/efi.h | 6 ++++
init/Kconfig | 9 +++++
kernel/Makefile | 3 ++
kernel/modsign_uefi.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 109 insertions(+)
create mode 100644 kernel/modsign_uefi.c
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 42a1d25..d3e6036 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -395,6 +395,12 @@ typedef efi_status_t efi_query_variable_store_t(u32 attributes, unsigned long si
#define EFI_CERT_X509_GUID \
EFI_GUID( 0xa5c059a1, 0x94e4, 0x4aa7, 0x87, 0xb5, 0xab, 0x15, 0x5c, 0x2b, 0xf0, 0x72 )
+#define EFI_IMAGE_SECURITY_DATABASE_GUID \
+ EFI_GUID( 0xd719b2cb, 0x3d3a, 0x4596, 0xa3, 0xbc, 0xda, 0xd0, 0x0e, 0x67, 0x65, 0x6f )
+
+#define EFI_SHIM_LOCK_GUID \
+ EFI_GUID( 0x605dab50, 0xe046, 0x4300, 0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23 )
+
typedef struct {
efi_guid_t guid;
u64 table;
diff --git a/init/Kconfig b/init/Kconfig
index b4fa2d1..94ce526 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1780,6 +1780,15 @@ config MODULE_SIG_BLACKLIST
should not pass module signature verification. If a module is
signed with something in this keyring, the load will be rejected.
+config MODULE_SIG_UEFI
+ bool "Allow modules signed with certs stored in UEFI"
+ depends on MODULE_SIG && MODULE_SIG_BLACKLIST && EFI
+ select EFI_SIGNATURE_LIST_PARSER
+ help
+ This will import certificates stored in UEFI and allow modules
+ signed with those to be loaded. It will also disallow loading
+ of modules stored in the UEFI dbx variable.
+
choice
prompt "Which hash algorithm should modules be signed with?"
depends on MODULE_SIG
diff --git a/kernel/Makefile b/kernel/Makefile
index 35ef118..6ca1fea 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -55,6 +55,7 @@ obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
obj-$(CONFIG_UID16) += uid16.o
obj-$(CONFIG_MODULES) += module.o
obj-$(CONFIG_MODULE_SIG) += module_signing.o modsign_pubkey.o modsign_certificate.o
+obj-$(CONFIG_MODULE_SIG_UEFI) += modsign_uefi.o
obj-$(CONFIG_KALLSYMS) += kallsyms.o
obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
obj-$(CONFIG_KEXEC) += kexec.o
@@ -114,6 +115,8 @@ obj-$(CONFIG_CONTEXT_TRACKING) += context_tracking.o
$(obj)/configs.o: $(obj)/config_data.h
+$(obj)/modsign_uefi.o: KBUILD_CFLAGS += -fshort-wchar
+
# config_data.h contains the same information as ikconfig.h but gzipped.
# Info from config_data can be extracted from /proc/config*
targets += config_data.gz
diff --git a/kernel/modsign_uefi.c b/kernel/modsign_uefi.c
new file mode 100644
index 0000000..7eae5b4
--- /dev/null
+++ b/kernel/modsign_uefi.c
@@ -0,0 +1,91 @@
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/cred.h>
+#include <linux/err.h>
+#include <linux/efi.h>
+#include <linux/slab.h>
+#include <keys/asymmetric-type.h>
+#include "module-internal.h"
+
+static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, unsigned long *size)
+{
+ efi_status_t status;
+ unsigned long lsize = 4;
+ unsigned long tmpdb[4];
+ void *db = NULL;
+
+ status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb);
+ if (status != EFI_BUFFER_TOO_SMALL) {
+ pr_err("Couldn't get size: 0x%lx\n", status);
+ return NULL;
+ }
+
+ db = kmalloc(lsize, GFP_KERNEL);
+ if (!db) {
+ pr_err("Couldn't allocate memory for uefi cert list\n");
+ goto out;
+ }
+
+ status = efi.get_variable(name, guid, NULL, &lsize, db);
+ if (status != EFI_SUCCESS) {
+ kfree(db);
+ db = NULL;
+ pr_err("Error reading db var: 0x%lx\n", status);
+ }
+out:
+ *size = lsize;
+ return db;
+}
+
+/*
+ * * Load the certs contained in the UEFI databases
+ * */
+static int __init load_uefi_certs(void)
+{
+ efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
+ efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
+ void *db = NULL, *dbx = NULL, *mok = NULL;
+ unsigned long dbsize = 0, dbxsize = 0, moksize = 0;
+ int rc = 0;
+
+ /* Check if SB is enabled and just return if not */
+ if (!efi_enabled(EFI_SECURE_BOOT))
+ return 0;
+
+ /* Get db, MokListRT, and dbx. They might not exist, so it isn't
+ * an error if we can't get them.
+ */
+ db = get_cert_list(L"db", &secure_var, &dbsize);
+ if (!db) {
+ pr_err("MODSIGN: Couldn't get UEFI db list\n");
+ } else {
+ rc = parse_efi_signature_list(db, dbsize, modsign_keyring);
+ if (rc)
+ pr_err("Couldn't parse db signatures: %d\n", rc);
+ kfree(db);
+ }
+
+ mok = get_cert_list(L"MokListRT", &mok_var, &moksize);
+ if (!mok) {
+ pr_info("MODSIGN: Couldn't get UEFI MokListRT\n");
+ } else {
+ rc = parse_efi_signature_list(mok, moksize, modsign_keyring);
+ if (rc)
+ pr_err("Couldn't parse MokListRT signatures: %d\n", rc);
+ kfree(mok);
+ }
+
+ dbx = get_cert_list(L"dbx", &secure_var, &dbxsize);
+ if (!dbx) {
+ pr_info("MODSIGN: Couldn't get UEFI dbx list\n");
+ } else {
+ rc = parse_efi_signature_list(dbx, dbxsize,
+ modsign_blacklist);
+ if (rc)
+ pr_err("Couldn't parse dbx signatures: %d\n", rc);
+ kfree(dbx);
+ }
+
+ return rc;
+}
+late_initcall(load_uefi_certs);
--
1.8.3.1
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