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https://github.com/tbsdtv/linux_media.git
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Move certificate handling to its own directory
Move certificate handling out of the kernel/ directory and into a certs/ directory to get all the weird stuff in one place and move the generated signing keys into this directory. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: David Woodhouse <David.Woodhouse@intel.com>
This commit is contained in:
David Howells
committed by
David Woodhouse
David Woodhouse
parent
0e38c35815
commit
cfc411e7ff
42
certs/Kconfig
Normal file
42
certs/Kconfig
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@@ -0,0 +1,42 @@
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menu "Certificates for signature checking"
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config MODULE_SIG_KEY
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string "File name or PKCS#11 URI of module signing key"
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default "certs/signing_key.pem"
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depends on MODULE_SIG
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help
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Provide the file name of a private key/certificate in PEM format,
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or a PKCS#11 URI according to RFC7512. The file should contain, or
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the URI should identify, both the certificate and its corresponding
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private key.
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If this option is unchanged from its default "certs/signing_key.pem",
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then the kernel will automatically generate the private key and
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certificate as described in Documentation/module-signing.txt
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config SYSTEM_TRUSTED_KEYRING
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bool "Provide system-wide ring of trusted keys"
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depends on KEYS
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help
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Provide a system keyring to which trusted keys can be added. Keys in
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the keyring are considered to be trusted. Keys may be added at will
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by the kernel from compiled-in data and from hardware key stores, but
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userspace may only add extra keys if those keys can be verified by
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keys already in the keyring.
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Keys in this keyring are used by module signature checking.
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config SYSTEM_TRUSTED_KEYS
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string "Additional X.509 keys for default system keyring"
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depends on SYSTEM_TRUSTED_KEYRING
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help
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If set, this option should be the filename of a PEM-formatted file
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containing trusted X.509 certificates to be included in the default
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system keyring. Any certificate used for module signing is implicitly
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also trusted.
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NOTE: If you previously provided keys for the system keyring in the
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form of DER-encoded *.x509 files in the top-level build directory,
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those are no longer used. You will need to set this option instead.
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endmenu
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147
certs/Makefile
Normal file
147
certs/Makefile
Normal file
@@ -0,0 +1,147 @@
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#
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# Makefile for the linux kernel signature checking certificates.
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#
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obj-$(CONFIG_SYSTEM_TRUSTED_KEYRING) += system_keyring.o system_certificates.o
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###############################################################################
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#
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# When a Kconfig string contains a filename, it is suitable for
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# passing to shell commands. It is surrounded by double-quotes, and
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# any double-quotes or backslashes within it are escaped by
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# backslashes.
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#
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# This is no use for dependencies or $(wildcard). We need to strip the
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# surrounding quotes and the escaping from quotes and backslashes, and
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# we *do* need to escape any spaces in the string. So, for example:
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#
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# Usage: $(eval $(call config_filename,FOO))
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#
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# Defines FOO_FILENAME based on the contents of the CONFIG_FOO option,
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# transformed as described above to be suitable for use within the
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# makefile.
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#
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# Also, if the filename is a relative filename and exists in the source
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# tree but not the build tree, define FOO_SRCPREFIX as $(srctree)/ to
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# be prefixed to *both* command invocation and dependencies.
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#
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# Note: We also print the filenames in the quiet_cmd_foo text, and
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# perhaps ought to have a version specially escaped for that purpose.
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# But it's only cosmetic, and $(patsubst "%",%,$(CONFIG_FOO)) is good
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# enough. It'll strip the quotes in the common case where there's no
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# space and it's a simple filename, and it'll retain the quotes when
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# there's a space. There are some esoteric cases in which it'll print
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# the wrong thing, but we don't really care. The actual dependencies
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# and commands *do* get it right, with various combinations of single
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# and double quotes, backslashes and spaces in the filenames.
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#
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###############################################################################
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#
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quote := $(firstword " ")
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space :=
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space +=
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space_escape := %%%SPACE%%%
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#
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define config_filename
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ifneq ($$(CONFIG_$(1)),"")
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$(1)_FILENAME := $$(subst \\,\,$$(subst \$$(quote),$$(quote),$$(subst $$(space_escape),\$$(space),$$(patsubst "%",%,$$(subst $$(space),$$(space_escape),$$(CONFIG_$(1)))))))
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ifneq ($$(patsubst /%,%,$$(firstword $$($(1)_FILENAME))),$$(firstword $$($(1)_FILENAME)))
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else
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ifeq ($$(wildcard $$($(1)_FILENAME)),)
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ifneq ($$(wildcard $$(srctree)/$$($(1)_FILENAME)),)
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$(1)_SRCPREFIX := $(srctree)/
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endif
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endif
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endif
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endif
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endef
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#
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###############################################################################
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ifeq ($(CONFIG_SYSTEM_TRUSTED_KEYRING),y)
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$(eval $(call config_filename,SYSTEM_TRUSTED_KEYS))
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# GCC doesn't include .incbin files in -MD generated dependencies (PR#66871)
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$(obj)/system_certificates.o: $(obj)/x509_certificate_list
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# Cope with signing_key.x509 existing in $(srctree) not $(objtree)
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AFLAGS_system_certificates.o := -I$(srctree)
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quiet_cmd_extract_certs = EXTRACT_CERTS $(patsubst "%",%,$(2))
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cmd_extract_certs = scripts/extract-cert $(2) $@ || ( rm $@; exit 1)
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targets += x509_certificate_list
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$(obj)/x509_certificate_list: scripts/extract-cert $(SYSTEM_TRUSTED_KEYS_SRCPREFIX)$(SYSTEM_TRUSTED_KEYS_FILENAME) FORCE
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$(call if_changed,extract_certs,$(SYSTEM_TRUSTED_KEYS_SRCPREFIX)$(CONFIG_SYSTEM_TRUSTED_KEYS))
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endif
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clean-files := x509_certificate_list .x509.list
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ifeq ($(CONFIG_MODULE_SIG),y)
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###############################################################################
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#
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# If module signing is requested, say by allyesconfig, but a key has not been
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# supplied, then one will need to be generated to make sure the build does not
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# fail and that the kernel may be used afterwards.
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#
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###############################################################################
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ifndef CONFIG_MODULE_SIG_HASH
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$(error Could not determine digest type to use from kernel config)
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endif
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# We do it this way rather than having a boolean option for enabling an
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# external private key, because 'make randconfig' might enable such a
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# boolean option and we unfortunately can't make it depend on !RANDCONFIG.
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ifeq ($(CONFIG_MODULE_SIG_KEY),"certs/signing_key.pem")
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$(obj)/signing_key.pem: $(obj)/x509.genkey
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@echo "###"
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@echo "### Now generating an X.509 key pair to be used for signing modules."
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@echo "###"
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@echo "### If this takes a long time, you might wish to run rngd in the"
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@echo "### background to keep the supply of entropy topped up. It"
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@echo "### needs to be run as root, and uses a hardware random"
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@echo "### number generator if one is available."
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@echo "###"
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openssl req -new -nodes -utf8 -$(CONFIG_MODULE_SIG_HASH) -days 36500 \
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-batch -x509 -config $(obj)/x509.genkey \
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-outform PEM -out $(obj)/signing_key.pem \
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-keyout $(obj)/signing_key.pem 2>&1
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@echo "###"
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@echo "### Key pair generated."
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@echo "###"
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$(obj)/x509.genkey:
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@echo Generating X.509 key generation config
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@echo >$@ "[ req ]"
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@echo >>$@ "default_bits = 4096"
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@echo >>$@ "distinguished_name = req_distinguished_name"
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@echo >>$@ "prompt = no"
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@echo >>$@ "string_mask = utf8only"
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@echo >>$@ "x509_extensions = myexts"
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@echo >>$@
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@echo >>$@ "[ req_distinguished_name ]"
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@echo >>$@ "#O = Unspecified company"
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@echo >>$@ "CN = Build time autogenerated kernel key"
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@echo >>$@ "#emailAddress = unspecified.user@unspecified.company"
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@echo >>$@
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@echo >>$@ "[ myexts ]"
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@echo >>$@ "basicConstraints=critical,CA:FALSE"
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@echo >>$@ "keyUsage=digitalSignature"
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@echo >>$@ "subjectKeyIdentifier=hash"
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@echo >>$@ "authorityKeyIdentifier=keyid"
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endif
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$(eval $(call config_filename,MODULE_SIG_KEY))
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# If CONFIG_MODULE_SIG_KEY isn't a PKCS#11 URI, depend on it
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ifeq ($(patsubst pkcs11:%,%,$(firstword $(MODULE_SIG_KEY_FILENAME))),$(firstword $(MODULE_SIG_KEY_FILENAME)))
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X509_DEP := $(MODULE_SIG_KEY_SRCPREFIX)$(MODULE_SIG_KEY_FILENAME)
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endif
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# GCC PR#66871 again.
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$(obj)/system_certificates.o: $(obj)/signing_key.x509
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$(obj)/signing_key.x509: scripts/extract-cert include/config/module/sig/key.h $(X509_DEP)
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$(call cmd,extract_certs,$(MODULE_SIG_KEY_SRCPREFIX)$(CONFIG_MODULE_SIG_KEY))
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endif
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23
certs/system_certificates.S
Normal file
23
certs/system_certificates.S
Normal file
@@ -0,0 +1,23 @@
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#include <linux/export.h>
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#include <linux/init.h>
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__INITRODATA
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.align 8
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.globl VMLINUX_SYMBOL(system_certificate_list)
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VMLINUX_SYMBOL(system_certificate_list):
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__cert_list_start:
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#ifdef CONFIG_MODULE_SIG
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.incbin "certs/signing_key.x509"
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#endif
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.incbin "certs/x509_certificate_list"
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__cert_list_end:
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.align 8
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.globl VMLINUX_SYMBOL(system_certificate_list_size)
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VMLINUX_SYMBOL(system_certificate_list_size):
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#ifdef CONFIG_64BIT
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.quad __cert_list_end - __cert_list_start
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#else
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.long __cert_list_end - __cert_list_start
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#endif
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157
certs/system_keyring.c
Normal file
157
certs/system_keyring.c
Normal file
@@ -0,0 +1,157 @@
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/* System trusted keyring for trusted public keys
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*
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* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/export.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/cred.h>
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#include <linux/err.h>
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#include <keys/asymmetric-type.h>
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#include <keys/system_keyring.h>
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#include <crypto/pkcs7.h>
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struct key *system_trusted_keyring;
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EXPORT_SYMBOL_GPL(system_trusted_keyring);
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extern __initconst const u8 system_certificate_list[];
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extern __initconst const unsigned long system_certificate_list_size;
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/*
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* Load the compiled-in keys
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*/
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static __init int system_trusted_keyring_init(void)
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{
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pr_notice("Initialise system trusted keyring\n");
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system_trusted_keyring =
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keyring_alloc(".system_keyring",
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KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
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((KEY_POS_ALL & ~KEY_POS_SETATTR) |
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KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
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KEY_ALLOC_NOT_IN_QUOTA, NULL);
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if (IS_ERR(system_trusted_keyring))
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panic("Can't allocate system trusted keyring\n");
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set_bit(KEY_FLAG_TRUSTED_ONLY, &system_trusted_keyring->flags);
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return 0;
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}
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/*
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* Must be initialised before we try and load the keys into the keyring.
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*/
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device_initcall(system_trusted_keyring_init);
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/*
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* Load the compiled-in list of X.509 certificates.
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*/
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static __init int load_system_certificate_list(void)
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{
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key_ref_t key;
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const u8 *p, *end;
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size_t plen;
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pr_notice("Loading compiled-in X.509 certificates\n");
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p = system_certificate_list;
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end = p + system_certificate_list_size;
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while (p < end) {
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/* Each cert begins with an ASN.1 SEQUENCE tag and must be more
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* than 256 bytes in size.
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*/
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if (end - p < 4)
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goto dodgy_cert;
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if (p[0] != 0x30 &&
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p[1] != 0x82)
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goto dodgy_cert;
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plen = (p[2] << 8) | p[3];
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plen += 4;
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if (plen > end - p)
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goto dodgy_cert;
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key = key_create_or_update(make_key_ref(system_trusted_keyring, 1),
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"asymmetric",
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NULL,
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p,
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plen,
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((KEY_POS_ALL & ~KEY_POS_SETATTR) |
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KEY_USR_VIEW | KEY_USR_READ),
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KEY_ALLOC_NOT_IN_QUOTA |
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KEY_ALLOC_TRUSTED);
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if (IS_ERR(key)) {
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pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
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PTR_ERR(key));
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} else {
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set_bit(KEY_FLAG_BUILTIN, &key_ref_to_ptr(key)->flags);
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pr_notice("Loaded X.509 cert '%s'\n",
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key_ref_to_ptr(key)->description);
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key_ref_put(key);
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}
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p += plen;
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}
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return 0;
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dodgy_cert:
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pr_err("Problem parsing in-kernel X.509 certificate list\n");
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return 0;
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}
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late_initcall(load_system_certificate_list);
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#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
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/**
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* Verify a PKCS#7-based signature on system data.
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* @data: The data to be verified.
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* @len: Size of @data.
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* @raw_pkcs7: The PKCS#7 message that is the signature.
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* @pkcs7_len: The size of @raw_pkcs7.
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* @usage: The use to which the key is being put.
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*/
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int system_verify_data(const void *data, unsigned long len,
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const void *raw_pkcs7, size_t pkcs7_len,
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enum key_being_used_for usage)
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{
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struct pkcs7_message *pkcs7;
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bool trusted;
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int ret;
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pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
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if (IS_ERR(pkcs7))
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return PTR_ERR(pkcs7);
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/* The data should be detached - so we need to supply it. */
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if (pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
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pr_err("PKCS#7 signature with non-detached data\n");
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ret = -EBADMSG;
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goto error;
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}
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ret = pkcs7_verify(pkcs7, usage);
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if (ret < 0)
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goto error;
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ret = pkcs7_validate_trust(pkcs7, system_trusted_keyring, &trusted);
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if (ret < 0)
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goto error;
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if (!trusted) {
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pr_err("PKCS#7 signature not signed with a trusted key\n");
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ret = -ENOKEY;
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}
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error:
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pkcs7_free_message(pkcs7);
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pr_devel("<==%s() = %d\n", __func__, ret);
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return ret;
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}
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EXPORT_SYMBOL_GPL(system_verify_data);
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#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
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Reference in New Issue
Block a user