KEYS: Introduce load_pgp_public_keyring()

Preload PGP keys from 'pubring.gpg', placed in certs/ of the kernel source
directory.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>

certs/Kconfig

diff --git a/certs/Kconfig b/certs/Kconfig
index 78307dc..9b7ece1 100644
--- a/certs/Kconfig
+++ b/certs/Kconfig
@@ -154,4 +154,15 @@
 	  keyring.  The PKCS#7 signature of the description is set in the key
 	  payload.  Blacklist keys cannot be removed.
 
+config PGP_PRELOAD_PUBLIC_KEYS
+	bool "Preload PGP public keys"
+	depends on SYSTEM_TRUSTED_KEYRING
+	select PGP_PRELOAD
+	default n
+	help
+	  Load at boot time the PGP public keys from a reserved area (populated
+	  with the content of 'certs/pubring.gpg' provided at kernel build
+	  time), and add them to the built-in keyring. Invalid keys are ignored
+	  and the loading continues.
+
 endmenu

certs/Makefile

diff --git a/certs/Makefile b/certs/Makefile
index 1094e38..1faa44e 100644
--- a/certs/Makefile
+++ b/certs/Makefile
@@ -22,6 +22,16 @@
 
 targets += blacklist_hash_list
 
+ifdef CONFIG_PGP_PRELOAD_PUBLIC_KEYS
+ifeq ($(shell ls $(srctree)/certs/pubring.gpg 2> /dev/null), $(srctree)/certs/pubring.gpg)
+AFLAGS_system_certificates.o += -DHAVE_PUBRING_GPG
+$(obj)/system_certificates.o: $(srctree)/certs/pubring.gpg
+endif
+endif
+
+quiet_cmd_extract_certs  = EXTRACT_CERTS   $(patsubst "%",%,$(2))
+      cmd_extract_certs  = scripts/extract-cert $(2) $@
+
 quiet_cmd_extract_certs  = CERT    $@
       cmd_extract_certs  = $(obj)/extract-cert "$(extract-cert-in)" $@
 extract-cert-in = $(filter-out $(obj)/extract-cert, $(real-prereqs))

certs/system_certificates.S

diff --git a/certs/system_certificates.S b/certs/system_certificates.S
index 003e25d..b3cbf081 100644
--- a/certs/system_certificates.S
+++ b/certs/system_certificates.S
@@ -44,3 +44,21 @@
 #else
 	.long __module_cert_end - __module_cert_start
 #endif
+
+	.align 8
+	.globl pgp_public_keys
+pgp_public_keys:
+__pgp_key_list_start:
+#ifdef HAVE_PUBRING_GPG
+	.incbin "certs/pubring.gpg"
+#endif
+__pgp_key_list_end:
+
+	.align 8
+	.globl pgp_public_keys_size
+pgp_public_keys_size:
+#ifdef CONFIG_64BIT
+	.quad __pgp_key_list_end - __pgp_key_list_start
+#else
+	.long __pgp_key_list_end - __pgp_key_list_start
+#endif

certs/system_keyring.c

diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index db0fde3..ee07f4e 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -296,6 +296,27 @@ static __init int load_system_certificate_list(void)
 }
 late_initcall(load_system_certificate_list);
 
+#ifdef CONFIG_PGP_PRELOAD_PUBLIC_KEYS
+extern __initconst const u8 pgp_public_keys[];
+extern __initconst const unsigned long pgp_public_keys_size;
+
+/*
+ * Load a list of PGP keys.
+ */
+static __init int load_pgp_public_keyring(void)
+{
+	pr_notice("Load PGP public keys\n");
+
+	if (preload_pgp_keys(pgp_public_keys,
+			     pgp_public_keys_size,
+			     builtin_trusted_keys) < 0)
+		pr_err("Can't load PGP public keys\n");
+
+	return 0;
+}
+late_initcall(load_pgp_public_keyring);
+#endif /* CONFIG_PGP_PRELOAD_PUBLIC_KEYS */
+
 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 
 /**