Re: [PATCH 1/3] X.509: Fix certificate gathering again
From: David Howells
Date: Tue May 26 2015 - 12:15:55 EST
Hi Michal,
Could you have a look at the patch at the end of my branch:
http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=modsign-pkcs7
It changes things from picking up arbitrary *.x509 files dropped in the kernel
source and/or build directory to taking a single named PEM file with all the
additional certs as a string config option. The PEM file can contain multiple
certs simply cat'd together.
If you're okay with that, it obsoletes these patches of yours.
I've attached it here for convenience also.
David
---
commit 9c71c950793b1b8c23c6d945b31f6545f82adced
Author: David Woodhouse <David.Woodhouse@xxxxxxxxx>
Date: Thu May 21 12:23:55 2015 +0100
modsign: Add explicit CONFIG_SYSTEM_TRUSTED_KEYS option
Let the user explicitly provide a file containing trusted keys, instead of
just automatically finding files matching *.x509 in the build tree and
trusting whatever we find. This really ought to be an *explicit*
configuration, and the build rules for dealing with the files were
fairly painful too.
Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
diff --git a/Documentation/module-signing.txt b/Documentation/module-signing.txt
index 5d5e4e32dc26..4e62bc29666e 100644
--- a/Documentation/module-signing.txt
+++ b/Documentation/module-signing.txt
@@ -88,6 +88,7 @@ This has a number of options available:
than being a module) so that modules signed with that algorithm can have
their signatures checked without causing a dependency loop.
+
(4) "File name or PKCS#11 URI of module signing key" (CONFIG_MODULE_SIG_KEY)
Setting this option to something other than its default of
@@ -104,6 +105,13 @@ This has a number of options available:
means of the KBUILD_SIGN_PIN variable.
+ (5) "Additional X.509 keys for default system keyring" (CONFIG_SYSTEM_TRUSTED_KEYS)
+
+ This option can be set to the filename of a PEM-encoded file containing
+ additional certificates which will be included in the system keyring by
+ default.
+
+
=======================
GENERATING SIGNING KEYS
=======================
@@ -171,10 +179,9 @@ in a keyring called ".system_keyring" that can be seen by:
302d2d52 I------ 1 perm 1f010000 0 0 asymmetri Fedora kernel signing key: d69a84e6bce3d216b979e9505b3e3ef9a7118079: X509.RSA a7118079 []
...
-Beyond the public key generated specifically for module signing, any file
-placed in the kernel source root directory or the kernel build root directory
-whose name is suffixed with ".x509" will be assumed to be an X.509 public key
-and will be added to the keyring.
+Beyond the public key generated specifically for module signing, additional
+trusted certificates can be provided in a PEM-encoded file referenced by the
+CONFIG_SYSTEM_TRUSTED_KEYS configuration option.
Further, the architecture code may take public keys from a hardware store and
add those in also (e.g. from the UEFI key database).
diff --git a/init/Kconfig b/init/Kconfig
index a52935338419..b46c19525074 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1758,6 +1758,19 @@ config SYSTEM_TRUSTED_KEYRING
Keys in this keyring are used by module signature checking.
+config SYSTEM_TRUSTED_KEYS
+ string "Additional X.509 keys for default system keyring"
+ depends on SYSTEM_TRUSTED_KEYRING
+ help
+ If set, this option should be the filename of a PEM-formatted file
+ containing trusted X.509 certificates to be included in the default
+ system keyring. Any certificate used for module signing is implicitly
+ also trusted.
+
+ NOTE: If you previously provided keys for the system keyring in the
+ form of DER-encoded *.x509 files in the top-level build directory,
+ those are no longer used. You will need to set this option instead.
+
config SYSTEM_DATA_VERIFICATION
def_bool n
select SYSTEM_TRUSTED_KEYRING
diff --git a/kernel/Makefile b/kernel/Makefile
index 541e1e89e90c..2d03e870ba8d 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -114,46 +114,75 @@ $(obj)/config_data.h: $(obj)/config_data.gz FORCE
###############################################################################
#
-# Roll all the X.509 certificates that we can find together and pull them into
-# the kernel so that they get loaded into the system trusted keyring during
-# boot.
+# When a Kconfig string contains a filename, it is suitable for
+# passing to shell commands. It is surrounded by double-quotes, and
+# any double-quotes or backslashes within it are escaped by
+# backslashes.
#
-# We look in the source root and the build root for all files whose name ends
-# in ".x509". Unfortunately, this will generate duplicate filenames, so we
-# have make canonicalise the pathnames and then sort them to discard the
-# duplicates.
+# This is no use for dependencies or $(wildcard). We need to strip the
+# surrounding quotes and the escaping from quotes and backslashes, and
+# we *do* need to escape any spaces in the string. So, for example:
+#
+# Usage: $(eval $(call config_filename,FOO))
+#
+# Defines FOO_FILENAME based on the contents of the CONFIG_FOO option,
+# transformed as described above to be suitable for use within the
+# makefile.
+#
+# Also, if the filename is a relative filename and exists in the source
+# tree but not the build tree, define FOO_SRCPREFIX as $(srctree)/ to
+# be prefixed to *both* command invocation and dependencies.
+#
+# Note: We also print the filenames in the quiet_cmd_foo text, and
+# perhaps ought to have a version specially escaped for that purpose.
+# But it's only cosmetic, and $(patsubst "%",%,$(CONFIG_FOO)) is good
+# enough. It'll strip the quotes in the common case where there's no
+# space and it's a simple filename, and it'll retain the quotes when
+# there's a space. There are some esoteric cases in which it'll print
+# the wrong thing, but we don't really care. The actual dependencies
+# and commands *do* get it right, with various combinations of single
+# and double quotes, backslashes and spaces in the filenames.
#
###############################################################################
-ifeq ($(CONFIG_SYSTEM_TRUSTED_KEYRING),y)
-X509_CERTIFICATES-y := $(wildcard *.x509) $(wildcard $(srctree)/*.x509)
-X509_CERTIFICATES-$(CONFIG_MODULE_SIG) += $(objtree)/signing_key.x509
-X509_CERTIFICATES-raw := $(sort $(foreach CERT,$(X509_CERTIFICATES-y), \
- $(or $(realpath $(CERT)),$(CERT))))
-X509_CERTIFICATES := $(subst $(realpath $(objtree))/,,$(X509_CERTIFICATES-raw))
-
-ifeq ($(X509_CERTIFICATES),)
-$(warning *** No X.509 certificates found ***)
+#
+quote := $(firstword " ")
+space :=
+space +=
+space_escape := %%%SPACE%%%
+#
+define config_filename =
+ifneq ($$(CONFIG_$(1)),"")
+$(1)_FILENAME := $$(subst \\,\,$$(subst \$$(quote),$$(quote),$$(subst $$(space_escape),\$$(space),$$(patsubst "%",%,$$(subst $$(space),$$(space_escape),$$(CONFIG_$(1)))))))
+ifneq ($$(patsubst /%,%,$$(firstword $$($(1)_FILENAME))),$$(firstword $$($(1)_FILENAME)))
+else
+ifeq ($$(wildcard $$($(1)_FILENAME)),)
+ifneq ($$(wildcard $$(srctree)/$$($(1)_FILENAME)),)
+$(1)_SRCPREFIX := $(srctree)/
+endif
endif
-
-ifneq ($(wildcard $(obj)/.x509.list),)
-ifneq ($(shell cat $(obj)/.x509.list),$(X509_CERTIFICATES))
-$(info X.509 certificate list changed)
-$(shell rm $(obj)/.x509.list)
endif
endif
+endef
+#
+###############################################################################
+
+
+ifeq ($(CONFIG_SYSTEM_TRUSTED_KEYRING),y)
+
+$(eval $(call config_filename,SYSTEM_TRUSTED_KEYS))
+
+SIGNING_X509-$(CONFIG_MODULE_SIG) += signing_key.x509
kernel/system_certificates.o: $(obj)/x509_certificate_list
-quiet_cmd_x509certs = CERTS $@
- cmd_x509certs = cat $(X509_CERTIFICATES) /dev/null >$@ $(foreach X509,$(X509_CERTIFICATES),; $(kecho) " - Including cert $(X509)")
+quiet_cmd_x509certs = CERTS $(SIGNING_X509-y) $(patsubst "%",%,$(2))
+ cmd_x509certs = ( cat $(SIGNING_X509-y) /dev/null; \
+ awk '/-----BEGIN CERTIFICATE-----/{flag=1;next}/-----END CERTIFICATE-----/{flag=0}flag' $(2) /dev/null | base64 -d ) > $@ || ( rm $@; exit 1)
targets += $(obj)/x509_certificate_list
-$(obj)/x509_certificate_list: $(X509_CERTIFICATES) $(obj)/.x509.list
- $(call if_changed,x509certs)
+$(obj)/x509_certificate_list: $(SIGNING_X509-y) include/config/system/trusted/keys.h include/config/module/sig.h $(SYSTEM_TRUSTED_KEYS_SRCPREFIX)$(SYSTEM_TRUSTED_KEYS_FILENAME)
+ $(call if_changed,x509certs,$(SYSTEM_TRUSTED_KEYS_SRCPREFIX)$(CONFIG_SYSTEM_TRUSTED_KEYS))
-targets += $(obj)/.x509.list
-$(obj)/.x509.list:
- @echo $(X509_CERTIFICATES) >$@
endif
clean-files := x509_certificate_list .x509.list
@@ -212,40 +241,16 @@ x509.genkey:
@echo >>x509.genkey "authorityKeyIdentifier=keyid"
endif
-# We need to obtain the certificate from CONFIG_MODULE_SIG_KEY.
-quiet_cmd_extract_der = CERT_DER $(2)
- cmd_extract_der = scripts/extract-cert "$(2)" signing_key.x509
+$(eval $(call config_filename,MODULE_SIG_KEY))
-# 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
+# If CONFIG_MODULE_SIG_KEY isn't a PKCS#11 URI, depend on it
+ifeq ($(patsubst pkcs11:%,%,$(firstword $(MODULE_SIG_KEY_FILENAME))),$(firstword $(MODULE_SIG_KEY_FILENAME)))
+X509_DEP := $(MODULE_SIG_KEY_SRCPREFIX)$(MODULE_SIG_KEY_FILENAME)
endif
+quiet_cmd_extract_der = SIGNING_CERT $(patsubst "%",%,$(2))
+ cmd_extract_der = scripts/extract-cert $(2) signing_key.x509
+
signing_key.x509: scripts/extract-cert include/config/module/sig/key.h $(X509_DEP)
- $(call cmd,extract_der,$(X509_SOURCE))
+ $(call cmd,extract_der,$(MODULE_SIG_KEY_SRCPREFIX)$(CONFIG_MODULE_SIG_KEY))
endif
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