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Date: Tue, 19 May 2015 15:47:52 +0100
From: David Woodhouse <dwmw2@...radead.org>
To: dhowells@...hat.com
Cc: rusty@...tcorp.com.au, mmarek@...e.cz, mjg59@...f.ucam.org,
keyrings@...ux-nfs.org, dmitry.kasatkin@...il.com, mcgrof@...e.com,
linux-kernel@...r.kernel.org, dhowells@...hat.com,
seth.forshee@...onical.com, linux-security-module@...r.kernel.org
Subject: [PATCH 13/8] modsign: Extract signing cert from
CONFIG_MODULE_SIG_KEY if needed
Where an external PEM file or PKCS#11 URI is given, we can get the cert
from it for ourselves instead of making the user drop signing_key.x509
in place for us.
Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
---
The make rules are perhaps a little more baroque than I first intended.
I wonder if I really need to cope with filenames with spaces in. I note
that the *.x509 handling doesn't — if I create a file named 'foo bar.x509'
the build just craps out...
Documentation/module-signing.txt | 11 ++-
init/Kconfig | 8 +--
kernel/Makefile | 38 +++++++++++
scripts/Makefile | 3 +-
scripts/extract-cert.c | 144 +++++++++++++++++++++++++++++++++++++++
5 files changed, 193 insertions(+), 11 deletions(-)
create mode 100644 scripts/extract-cert.c
diff --git a/Documentation/module-signing.txt b/Documentation/module-signing.txt
index 84597c7..6930019 100644
--- a/Documentation/module-signing.txt
+++ b/Documentation/module-signing.txt
@@ -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
diff --git a/init/Kconfig b/init/Kconfig
index 3851815..a4b4f39 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1959,10 +1959,10 @@ 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
diff --git a/kernel/Makefile b/kernel/Makefile
index 050a55e..9fb259d 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -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
diff --git a/scripts/Makefile b/scripts/Makefile
index b12fe02..236f683 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -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)
diff --git a/scripts/extract-cert.c b/scripts/extract-cert.c
new file mode 100644
index 0000000..3faeff1
--- /dev/null
+++ b/scripts/extract-cert.c
@@ -0,0 +1,144 @@
+/* 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@...hat.com>
+ * David Woodhouse <dwmw2@...radead.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 char *key_pass;
+
+int main(int argc, char **argv)
+{
+ const char *pass_env;
+ char *cert_src, *cert_dst;
+ X509 *x509;
+ BIO *b;
+
+ OpenSSL_add_all_algorithms();
+ ERR_load_crypto_strings();
+ ERR_clear_error();
+
+ if (argc != 3)
+ format();
+
+ cert_src = argv[1];
+ cert_dst = argv[2];
+
+ /* If we add PKCS#12 support we'll need this... */
+ pass_env = getenv("CONFIG_MODULE_SIG_KEY_PASSWORD");
+ if (pass_env) {
+ int pwlen = strlen(pass_env);
+
+ if (pass_env[0] == '\"' && pass_env[pwlen - 1] == '\"') {
+ pass_env++;
+ pwlen -= 2;
+ }
+ if (pwlen)
+ key_pass = strndup(pass_env, pwlen);
+ }
+
+ 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;
+}
--
2.4.0
--
David Woodhouse Open Source Technology Centre
David.Woodhouse@...el.com Intel Corporation
--
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