[PATCH v9 3/3] integrity: support including firmware ".platform" keys at build time

[Nayna Jain]

Allow firmware keys to be embedded in the Linux kernel and loaded onto
the ".platform" keyring on boot.

The firmware keys can be specified in a file as a list of PEM encoded
certificates using new config INTEGRITY_PLATFORM_KEYS. The certificates
are embedded in the image by converting the PEM-formatted certificates
into DER(binary) and generating
security/integrity/platform_certs/platform_certificate_list file at
build time. On boot, the embedded certs from the image are loaded onto
the ".platform" keyring at late_initcall(), ensuring the platform keyring
exists before loading the keys.

Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxx>
---
 security/integrity/Kconfig                    | 10 +++++++
 security/integrity/Makefile                   | 15 ++++++++++-
 .../integrity/platform_certs/platform_cert.S  | 23 ++++++++++++++++
 .../platform_certs/platform_keyring.c         | 26 +++++++++++++++++++
 4 files changed, 73 insertions(+), 1 deletion(-)
 create mode 100644 security/integrity/platform_certs/platform_cert.S

diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig
index 599429f99f99..77b2c22c0e1b 100644
--- a/security/integrity/Kconfig
+++ b/security/integrity/Kconfig
@@ -62,6 +62,16 @@ config INTEGRITY_PLATFORM_KEYRING
          provided by the platform for verifying the kexec'ed kerned image
          and, possibly, the initramfs signature.
 
+config INTEGRITY_PLATFORM_KEYS
+        string "Builtin X.509 keys for .platform keyring"
+        depends on KEYS
+        depends on ASYMMETRIC_KEY_TYPE
+        depends on INTEGRITY_PLATFORM_KEYRING
+        help
+          If set, this option should be the filename of a PEM-formatted file
+          containing X.509 certificates to be loaded onto the ".platform"
+          keyring.
+
 config INTEGRITY_MACHINE_KEYRING
 	bool "Provide a keyring to which Machine Owner Keys may be added"
 	depends on SECONDARY_TRUSTED_KEYRING
diff --git a/security/integrity/Makefile b/security/integrity/Makefile
index d0ffe37dc1d6..65bd93301a3a 100644
--- a/security/integrity/Makefile
+++ b/security/integrity/Makefile
@@ -3,13 +3,17 @@
 # Makefile for caching inode integrity data (iint)
 #
 
+quiet_cmd_extract_certs  = CERT  $@
+      cmd_extract_certs  = certs/extract-cert $(2) $@
+
 obj-$(CONFIG_INTEGRITY) += integrity.o
 
 integrity-y := iint.o
 integrity-$(CONFIG_INTEGRITY_AUDIT) += integrity_audit.o
 integrity-$(CONFIG_INTEGRITY_SIGNATURE) += digsig.o
 integrity-$(CONFIG_INTEGRITY_ASYMMETRIC_KEYS) += digsig_asymmetric.o
-integrity-$(CONFIG_INTEGRITY_PLATFORM_KEYRING) += platform_certs/platform_keyring.o
+integrity-$(CONFIG_INTEGRITY_PLATFORM_KEYRING) += platform_certs/platform_keyring.o \
+						  platform_certs/platform_cert.o
 integrity-$(CONFIG_INTEGRITY_MACHINE_KEYRING) += platform_certs/machine_keyring.o
 integrity-$(CONFIG_LOAD_UEFI_KEYS) += platform_certs/efi_parser.o \
 				      platform_certs/load_uefi.o \
@@ -20,3 +24,12 @@ integrity-$(CONFIG_LOAD_PPC_KEYS) += platform_certs/efi_parser.o \
                                      platform_certs/keyring_handler.o
 obj-$(CONFIG_IMA)			+= ima/
 obj-$(CONFIG_EVM)			+= evm/
+
+$(obj)/platform_certs/platform_cert.o: $(obj)/platform_certs/platform_certificate_list
+
+targets += platform_certificate_list
+
+$(obj)/platform_certs/platform_certificate_list: $(CONFIG_INTEGRITY_PLATFORM_KEYS) certs/extract-cert FORCE
+	$(call if_changed,extract_certs,$(if $(CONFIG_INTEGRITY_PLATFORM_KEYS),$<,""))
+
+clean-files := platform_certs/platform_certificate_list
diff --git a/security/integrity/platform_certs/platform_cert.S b/security/integrity/platform_certs/platform_cert.S
new file mode 100644
index 000000000000..20bccce5dc5a
--- /dev/null
+++ b/security/integrity/platform_certs/platform_cert.S
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/export.h>
+#include <linux/init.h>
+
+	__INITRODATA
+
+	.align 8
+#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
+	.globl platform_certificate_list
+platform_certificate_list:
+__cert_list_start:
+	.incbin "security/integrity/platform_certs/platform_certificate_list"
+__cert_list_end:
+#endif
+
+	.align 8
+	.globl platform_certificate_list_size
+platform_certificate_list_size:
+#ifdef CONFIG_64BIT
+	.quad __cert_list_end - __cert_list_start
+#else
+	.long __cert_list_end - __cert_list_start
+#endif
diff --git a/security/integrity/platform_certs/platform_keyring.c b/security/integrity/platform_certs/platform_keyring.c
index bcafd7387729..b45de142c5f5 100644
--- a/security/integrity/platform_certs/platform_keyring.c
+++ b/security/integrity/platform_certs/platform_keyring.c
@@ -12,8 +12,12 @@
 #include <linux/cred.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <keys/system_keyring.h>
 #include "../integrity.h"
 
+extern __initconst const u8 platform_certificate_list[];
+extern __initconst const unsigned long platform_certificate_list_size;
+
 /**
  * add_to_platform_keyring - Add to platform keyring without validation.
  * @source: Source of key
@@ -37,6 +41,28 @@ void __init add_to_platform_keyring(const char *source, const void *data,
 		pr_info("Error adding keys to platform keyring %s\n", source);
 }
 
+static __init int load_platform_certificate_list(void)
+{
+	const u8 *p;
+	unsigned long size;
+	int rc;
+	struct key *keyring;
+
+	p = platform_certificate_list;
+	size = platform_certificate_list_size;
+
+	keyring = integrity_keyring_from_id(INTEGRITY_KEYRING_PLATFORM);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	rc = load_certificate_list(p, size, keyring);
+	if (rc)
+		pr_info("Error adding keys to platform keyring %d\n", rc);
+
+	return rc;
+}
+late_initcall(load_platform_certificate_list);
+
 /*
  * Create the trusted keyrings.
  */
-- 
2.27.0