modsign: Extract signing cert from CONFIG_MODULE_SIG_KEY if needed (1329e8cc) · Commits · e / devices / android_kernel_fairphone_FP3

Documentation/module-signing.txt

+5 −6

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		@@ -93,17 +93,16 @@ This has a number of options available:
		Setting this option to something other than its default of
		"signing_key.priv" will disable the autogeneration of signing keys and
		allow the kernel modules to be signed with a key of your choosing.
		The string provided should identify a file containing a private key
		in PEM form, or — on systems where the OpenSSL ENGINE_pkcs11 is
		appropriately installed — a PKCS#11 URI as defined by RFC7512.
		The string provided should identify a file containing both a private
		key and its corresponding X.509 certificate in PEM form, or — on
		systems where the OpenSSL ENGINE_pkcs11 is functional — a PKCS#11 URI
		as defined by RFC7512. In the latter case, the PKCS#11 URI should
		reference both a certificate and a private key.

		If the PEM file containing the private key is encrypted, or if the
		PKCS#11 token requries a PIN, this can be provided at build time by
		means of the KBUILD_SIGN_PIN variable.

		The corresponding X.509 certificate in DER form should still be placed
		in a file named signing_key.x509 in the top-level build directory.


		=======================
		GENERATING SIGNING KEYS

init/Kconfig

+4 −4

Original line number	Diff line number	Diff line
		@@ -1953,10 +1953,10 @@ config MODULE_SIG_KEY
		default "signing_key.priv"
		depends on MODULE_SIG
		help
		Provide the file name of a private key in PKCS#8 PEM format, or
		a PKCS#11 URI according to RFC7512. The corresponding X.509
		certificate in DER form should be present in signing_key.x509
		in the top-level build directory.
		Provide the file name of a private key/certificate in PEM format,
		or a PKCS#11 URI according to RFC7512. The file should contain, or
		the URI should identify, both the certificate and its corresponding
		private key.

		If this option is unchanged from its default "signing_key.priv",
		then the kernel will automatically generate the private key and

kernel/Makefile

+38 −0

Original line number	Diff line number	Diff line
		@@ -210,5 +210,43 @@ x509.genkey:
		@echo >>x509.genkey "keyUsage=digitalSignature"
		@echo >>x509.genkey "subjectKeyIdentifier=hash"
		@echo >>x509.genkey "authorityKeyIdentifier=keyid"
		else
		# For external (PKCS#11 or PEM) key, we need to obtain the certificate from
		# CONFIG_MODULE_SIG_KEY automatically.
		quiet_cmd_extract_der = CERT_DER $(2)
		cmd_extract_der = scripts/extract-cert "$(2)" signing_key.x509

		# CONFIG_MODULE_SIG_KEY is either a PKCS#11 URI or a filename. It is
		# surrounded by quotes, and may contain spaces. To strip the quotes
		# with $(patsubst) we need to turn the spaces into something else.
		# And if it's a filename, those spaces need to be escaped as '\ ' in
		# order to use it in dependencies or $(wildcard).
		space :=
		space +=
		space_escape := %%%SPACE%%%
		X509_SOURCE_temp := $(subst $(space),$(space_escape),$(CONFIG_MODULE_SIG_KEY))
		# We need this to check for absolute paths or PKCS#11 URIs.
		X509_SOURCE_ONEWORD := $(patsubst "%",%,$(X509_SOURCE_temp))
		# This is the actual source filename/URI without the quotes
		X509_SOURCE := $(subst $(space_escape),$(space),$(X509_SOURCE_ONEWORD))
		# This\ version\ with\ spaces\ escaped\ for\ $(wildcard)\ and\ dependencies
		X509_SOURCE_ESCAPED := $(subst $(space_escape),\$(space),$(X509_SOURCE_ONEWORD))

		ifeq ($(patsubst pkcs11:%,%,$(X509_SOURCE_ONEWORD)),$(X509_SOURCE_ONEWORD))
		# If it's a filename, depend on it.
		X509_DEP := $(X509_SOURCE_ESCAPED)
		ifeq ($(patsubst /%,%,$(X509_SOURCE_ONEWORD)),$(X509_SOURCE_ONEWORD))
		ifeq ($(wildcard $(X509_SOURCE_ESCAPED)),)
		ifneq ($(wildcard $(srctree)/$(X509_SOURCE_ESCAPED)),)
		# Non-absolute filename, found in source tree and not build tree
		X509_SOURCE := $(srctree)/$(X509_SOURCE)
		X509_DEP := $(srctree)/$(X509_SOURCE_ESCAPED)
		endif
		endif
		endif
		endif

		signing_key.x509: scripts/extract-cert include/config/module/sig/key.h $(X509_DEP)
		$(call cmd,extract_der,$(X509_SOURCE))
		endif
		endif

scripts/Makefile

+2 −1

Original line number	Diff line number	Diff line
		@@ -16,11 +16,12 @@ hostprogs-$(CONFIG_VT) += conmakehash
		hostprogs-$(BUILD_C_RECORDMCOUNT) += recordmcount
		hostprogs-$(CONFIG_BUILDTIME_EXTABLE_SORT) += sortextable
		hostprogs-$(CONFIG_ASN1) += asn1_compiler
		hostprogs-$(CONFIG_MODULE_SIG) += sign-file
		hostprogs-$(CONFIG_MODULE_SIG) += sign-file extract-cert

		HOSTCFLAGS_sortextable.o = -I$(srctree)/tools/include
		HOSTCFLAGS_asn1_compiler.o = -I$(srctree)/include
		HOSTLOADLIBES_sign-file = -lcrypto
		HOSTLOADLIBES_extract-cert = -lcrypto

		always := $(hostprogs-y) $(hostprogs-m)

scripts/extract-cert.c

0 → 100644

+132 −0

Original line number	Diff line number	Diff line
		/* Extract X.509 certificate in DER form from PKCS#11 or PEM.
		*
		* Copyright © 2014 Red Hat, Inc. All Rights Reserved.
		* Copyright © 2015 Intel Corporation.
		*
		* Authors: David Howells <dhowells@redhat.com>
		* David Woodhouse <dwmw2@infradead.org>
		*
		* 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 _GNU_SOURCE
		#include <stdio.h>
		#include <stdlib.h>
		#include <stdint.h>
		#include <stdbool.h>
		#include <string.h>
		#include <getopt.h>
		#include <err.h>
		#include <arpa/inet.h>
		#include <openssl/bio.h>
		#include <openssl/evp.h>
		#include <openssl/pem.h>
		#include <openssl/pkcs7.h>
		#include <openssl/err.h>
		#include <openssl/engine.h>

		#define PKEY_ID_PKCS7 2

		static __attribute__((noreturn))
		void format(void)
		{
		fprintf(stderr,
		"Usage: scripts/extract-cert <source> <dest>\n");
		exit(2);
		}

		static void display_openssl_errors(int l)
		{
		const char *file;
		char buf[120];
		int e, line;

		if (ERR_peek_error() == 0)
		return;
		fprintf(stderr, "At main.c:%d:\n", l);

		while ((e = ERR_get_error_line(&file, &line))) {
		ERR_error_string(e, buf);
		fprintf(stderr, "- SSL %s: %s:%d\n", buf, file, line);
		}
		}

		static void drain_openssl_errors(void)
		{
		const char *file;
		int line;

		if (ERR_peek_error() == 0)
		return;
		while (ERR_get_error_line(&file, &line)) {}
		}

		#define ERR(cond, fmt, ...) \
		do { \
		bool __cond = (cond); \
		display_openssl_errors(__LINE__); \
		if (__cond) { \
		err(1, fmt, ## __VA_ARGS__); \
		} \
		} while(0)

		static const char *key_pass;

		int main(int argc, char **argv)
		{
		char cert_src, cert_dst;
		X509 *x509;
		BIO *b;

		OpenSSL_add_all_algorithms();
		ERR_load_crypto_strings();
		ERR_clear_error();

		key_pass = getenv("KBUILD_SIGN_PIN");

		if (argc != 3)
		format();

		cert_src = argv[1];
		cert_dst = argv[2];

		if (!strncmp(cert_src, "pkcs11:", 7)) {
		ENGINE *e;
		struct {
		const char *cert_id;
		X509 *cert;
		} parms;

		parms.cert_id = cert_src;
		parms.cert = NULL;

		ENGINE_load_builtin_engines();
		drain_openssl_errors();
		e = ENGINE_by_id("pkcs11");
		ERR(!e, "Load PKCS#11 ENGINE");
		if (ENGINE_init(e))
		drain_openssl_errors();
		else
		ERR(1, "ENGINE_init");
		if (key_pass)
		ERR(!ENGINE_ctrl_cmd_string(e, "PIN", key_pass, 0), "Set PKCS#11 PIN");
		ENGINE_ctrl_cmd(e, "LOAD_CERT_CTRL", 0, &parms, NULL, 1);
		ERR(!parms.cert, "Get X.509 from PKCS#11");
		x509 = parms.cert;
		} else {
		b = BIO_new_file(cert_src, "rb");
		ERR(!b, "%s", cert_src);
		x509 = PEM_read_bio_X509(b, NULL, NULL, NULL);
		ERR(!x509, "%s", cert_src);
		BIO_free(b);
		}

		b = BIO_new_file(cert_dst, "wb");
		ERR(!b, "%s", cert_dst);
		ERR(!i2d_X509_bio(b, x509), cert_dst);
		BIO_free(b);

		return 0;
		}