[PATCH v2 3/4] certs: Add ability to preload revocation certs

[David Howells]

From: Eric Snowberg <eric.snowberg@xxxxxxxxxx>

Add a new Kconfig option called SYSTEM_REVOCATION_KEYS. If set,
this option should be the filename of a PEM-formated file containing
X.509 certificates to be included in the default blacklist keyring.

[DH: Changed this to make the new Kconfig option depend on the option to
enable the facility.]

Signed-off-by: Eric Snowberg <eric.snowberg@xxxxxxxxxx>
Acked-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200930201508.35113-3-eric.snowberg@xxxxxxxxxx/
Link: https://lore.kernel.org/r/20210122181054.32635-4-eric.snowberg@xxxxxxxxxx/ # v5
Link: https://lore.kernel.org/r/161428673564.677100.4112098280028451629.stgit@xxxxxxxxxxxxxxxxxxxxxx/
---

 certs/Kconfig                   |    8 ++++++++
 certs/Makefile                  |   18 ++++++++++++++++--
 certs/blacklist.c               |   17 +++++++++++++++++
 certs/revocation_certificates.S |   21 +++++++++++++++++++++
 scripts/Makefile                |    1 +
 5 files changed, 63 insertions(+), 2 deletions(-)
 create mode 100644 certs/revocation_certificates.S

diff --git a/certs/Kconfig b/certs/Kconfig
index 76e469b56a77..ab88d2a7f3c7 100644
--- a/certs/Kconfig
+++ b/certs/Kconfig
@@ -92,4 +92,12 @@ config SYSTEM_REVOCATION_LIST
 	  blacklist keyring and implements a hook whereby a PKCS#7 message can
 	  be checked to see if it matches such a certificate.
 
+config SYSTEM_REVOCATION_KEYS
+	string "X.509 certificates to be preloaded into the system blacklist keyring"
+	depends on SYSTEM_REVOCATION_LIST
+	help
+	  If set, this option should be the filename of a PEM-formatted file
+	  containing X.509 certificates to be included in the default blacklist
+	  keyring.
+
 endmenu
diff --git a/certs/Makefile b/certs/Makefile
index f4b90bad8690..e3f4926fd21e 100644
--- a/certs/Makefile
+++ b/certs/Makefile
@@ -4,7 +4,7 @@
 #
 
 obj-$(CONFIG_SYSTEM_TRUSTED_KEYRING) += system_keyring.o system_certificates.o common.o
-obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist.o
+obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist.o revocation_certificates.o common.o
 ifneq ($(CONFIG_SYSTEM_BLACKLIST_HASH_LIST),"")
 obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist_hashes.o
 else
@@ -29,7 +29,7 @@ $(obj)/x509_certificate_list: scripts/extract-cert $(SYSTEM_TRUSTED_KEYS_SRCPREF
 	$(call if_changed,extract_certs,$(SYSTEM_TRUSTED_KEYS_SRCPREFIX)$(CONFIG_SYSTEM_TRUSTED_KEYS))
 endif # CONFIG_SYSTEM_TRUSTED_KEYRING
 
-clean-files := x509_certificate_list .x509.list
+clean-files := x509_certificate_list .x509.list x509_revocation_list
 
 ifeq ($(CONFIG_MODULE_SIG),y)
 ###############################################################################
@@ -104,3 +104,17 @@ targets += signing_key.x509
 $(obj)/signing_key.x509: scripts/extract-cert $(X509_DEP) FORCE
 	$(call if_changed,extract_certs,$(MODULE_SIG_KEY_SRCPREFIX)$(CONFIG_MODULE_SIG_KEY))
 endif # CONFIG_MODULE_SIG
+
+ifeq ($(CONFIG_SYSTEM_BLACKLIST_KEYRING),y)
+
+$(eval $(call config_filename,SYSTEM_REVOCATION_KEYS))
+
+$(obj)/revocation_certificates.o: $(obj)/x509_revocation_list
+
+quiet_cmd_extract_certs  = EXTRACT_CERTS   $(patsubst "%",%,$(2))
+      cmd_extract_certs  = scripts/extract-cert $(2) $@
+
+targets += x509_revocation_list
+$(obj)/x509_revocation_list: scripts/extract-cert $(SYSTEM_REVOCATION_KEYS_SRCPREFIX)$(SYSTEM_REVOCATION_KEYS_FILENAME) FORCE
+	$(call if_changed,extract_certs,$(SYSTEM_REVOCATION_KEYS_SRCPREFIX)$(CONFIG_SYSTEM_REVOCATION_KEYS))
+endif
diff --git a/certs/blacklist.c b/certs/blacklist.c
index 2b8644123d5f..723b19c96256 100644
--- a/certs/blacklist.c
+++ b/certs/blacklist.c
@@ -17,9 +17,13 @@
 #include <linux/uidgid.h>
 #include <keys/system_keyring.h>
 #include "blacklist.h"
+#include "common.h"
 
 static struct key *blacklist_keyring;
 
+extern __initconst const u8 revocation_certificate_list[];
+extern __initconst const unsigned long revocation_certificate_list_size;
+
 /*
  * The description must be a type prefix, a colon and then an even number of
  * hex digits.  The hash is kept in the description.
@@ -220,3 +224,16 @@ static int __init blacklist_init(void)
  * Must be initialised before we try and load the keys into the keyring.
  */
 device_initcall(blacklist_init);
+
+/*
+ * Load the compiled-in list of revocation X.509 certificates.
+ */
+static __init int load_revocation_certificate_list(void)
+{
+	if (revocation_certificate_list_size)
+		pr_notice("Loading compiled-in revocation X.509 certificates\n");
+
+	return load_certificate_list(revocation_certificate_list, revocation_certificate_list_size,
+				     blacklist_keyring);
+}
+late_initcall(load_revocation_certificate_list);
diff --git a/certs/revocation_certificates.S b/certs/revocation_certificates.S
new file mode 100644
index 000000000000..f21aae8a8f0e
--- /dev/null
+++ b/certs/revocation_certificates.S
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/export.h>
+#include <linux/init.h>
+
+	__INITRODATA
+
+	.align 8
+	.globl revocation_certificate_list
+revocation_certificate_list:
+__revocation_list_start:
+	.incbin "certs/x509_revocation_list"
+__revocation_list_end:
+
+	.align 8
+	.globl revocation_certificate_list_size
+revocation_certificate_list_size:
+#ifdef CONFIG_64BIT
+	.quad __revocation_list_end - __revocation_list_start
+#else
+	.long __revocation_list_end - __revocation_list_start
+#endif
diff --git a/scripts/Makefile b/scripts/Makefile
index b5418ec587fb..983b785f13cb 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -11,6 +11,7 @@ hostprogs-always-$(CONFIG_ASN1)				+= asn1_compiler
 hostprogs-always-$(CONFIG_MODULE_SIG_FORMAT)		+= sign-file
 hostprogs-always-$(CONFIG_SYSTEM_TRUSTED_KEYRING)	+= extract-cert
 hostprogs-always-$(CONFIG_SYSTEM_EXTRA_CERTIFICATE)	+= insert-sys-cert
+ hostprogs-always-$(CONFIG_SYSTEM_BLACKLIST_KEYRING)	+= extract-cert
 
 HOSTCFLAGS_sorttable.o = -I$(srctree)/tools/include
 HOSTCFLAGS_asn1_compiler.o = -I$(srctree)/include