[PATCH 21/27] MODSIGN: Add modules_sign make target

[Josh Boyer]

If CONFIG_MODULE_SIG is set, and 'make modules_sign' is called then this
patch will cause the modules to get a signature installed.  The make target
is intended to be run after 'make modules_install', and will modify the
modules in-place in the installed location.

The signature will be appended to the module, along with the payload size,
the signature size and a magic string.  This requires private and public
keys to be available.  By default these are expected to be found in PGP
keyring files called modsign.sec (the secret key) and modsign.pub (the
public key) in the build root.

If signing occurs, lines like the following will be seen:

	SIGN [M] <install path>/fs/foo/foo.ko

will appear in the build log.  If the signature step will be skipped and the
following will be seen:

	NO SIGN [M] <install path>/fs/foo/foo.ko

NOTE!  After the signature step, the signed module must not be passed through
strip.  If you wish to strip or otherwise modify the kernel modules, use the
built-in stripping capabilities with 'make modules_install' or perform said
modifications before calling this make target.  This restriction may affect
packaging tools (such as rpmbuild) and initramfs composition tools.

Note that I do not agree with this method of attaching signatures to modules.
Based on work by David Howells <dhowells at redhat.com>

Signed-off-by: Josh Boyer <jwboyer at redhat.com>
---
 Makefile                 |  6 +++
 scripts/Makefile.modsign | 98 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 104 insertions(+)
 create mode 100644 scripts/Makefile.modsign

diff --git a/Makefile b/Makefile
index a347b81..a708eae 100644
--- a/Makefile
+++ b/Makefile
@@ -965,6 +965,12 @@ _modinst_post: _modinst_
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.fwinst obj=firmware __fw_modinst
 	$(call cmd,depmod)
 
+ifeq ($(CONFIG_MODULE_SIG), y)
+PHONY += modules_sign
+modules_sign:
+	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modsign
+endif
+
 else # CONFIG_MODULES
 
 # Modules not configured
diff --git a/scripts/Makefile.modsign b/scripts/Makefile.modsign
new file mode 100644
index 0000000..3ee7d3a
--- /dev/null
+++ b/scripts/Makefile.modsign
@@ -0,0 +1,98 @@
+# ==========================================================================
+# Signing modules
+# ==========================================================================
+
+PHONY := __modsign
+__modsign:
+
+include scripts/Kbuild.include
+
+__modules := $(sort $(shell grep -h '\.ko' /dev/null $(wildcard $(MODVERDIR)/*.mod)))
+modules := $(patsubst %.o,%.ko,$(wildcard $(__modules:.ko=.o)))
+
+PHONY += $(modules)
+__modsign: $(modules)
+	@:
+
+MODSECKEY = ./modsign.sec
+MODPUBKEY = ./modsign.pub
+KEYFLAGS = --no-default-keyring --secret-keyring $(MODSECKEY) --keyring $(MODPUBKEY) --no-default-keyring --homedir . --no-options --no-auto-check-trustdb --no-permission-warning
+
+ifdef CONFIG_MODULE_SIG_SHA1
+KEYFLAGS += --digest-algo=SHA1
+else
+ifdef CONFIG_MODULE_SIG_SHA224
+KEYFLAGS += --digest-algo=SHA224
+else
+ifdef CONFIG_MODULE_SIG_SHA256
+KEYFLAGS += --digest-algo=SHA256
+else
+ifdef CONFIG_MODULE_SIG_SHA384
+KEYFLAGS += --digest-algo=SHA384
+else
+ifdef CONFIG_MODULE_SIG_SHA512
+KEYFLAGS += --digest-algo=SHA512
+else
+endif
+endif
+endif
+endif
+endif
+
+ifdef MODKEYNAME
+KEYFLAGS += --default-key $(MODKEYNAME)
+endif
+
+ifeq ($(wildcard $(MODSECKEY))+$(wildcard $(MODPUBKEY)),$(MODSECKEY)+$(MODPUBKEY))
+ifeq ($(KBUILD_SRC),)
+       # no O= is being used
+       SCRIPTS_DIR := scripts
+else
+       SCRIPTS_DIR := $(KBUILD_SRC)/scripts
+endif
+SIGN_MODULES := 1
+else
+SIGN_MODULES := 0
+endif
+
+# only sign if it's an in-tree module
+ifneq ($(KBUILD_EXTMOD),)
+SIGN_MODULES := 0
+endif
+
+ifeq ($(SIGN_MODULES),1)
+KEYRING_DEP := modsign.sec modsign.pub
+quiet_cmd_sign_ko = SIGN [M] $(2)/$(notdir $@)
+      cmd_sign_ko = \
+		rm -f $(2)/$(notdir $@).sig && \
+		gpg --batch --no-greeting $(KEYFLAGS) -b $(2)/$(notdir $@) && \
+		( \
+			cat $(2)/$(notdir $@) $(2)/$(notdir $@).sig && \
+			stat --printf %-5s $(2)/$(notdir $@).sig && \
+			echo -n "This Is A Crypto Signed Module" \
+		) >$(2)/$(notdir $@).signed && \
+		mv $(2)/$(notdir $@).signed $(2)/$(notdir $@) && \
+		rm -f $(2)/$(notdir $@).sig
+else
+KEYRING_DEP :=
+quiet_cmd_sign_ko = NO SIGN [M] $@
+      cmd_sign_ko = \
+		true
+endif
+
+#quiet_cmd_modules_sign = SIGN $@
+#      cmd_modules_sign = mkdir -p $(2); cp $@ $(2) ; $(mod_strip_cmd) $(2)/$(notdir $@)
+
+# Modules built outside the kernel source tree go into extra by default
+INSTALL_MOD_DIR ?= extra
+ext-mod-dir = $(INSTALL_MOD_DIR)$(subst $(patsubst %/,%,$(KBUILD_EXTMOD)),,$(@D))
+
+modinst_dir = $(if $(KBUILD_EXTMOD),$(ext-mod-dir),kernel/$(@D))
+
+$(modules):
+	$(call cmd,sign_ko,$(MODLIB)/$(modinst_dir))
+
+# Declare the contents of the .PHONY variable as phony.  We keep that
+# # information in a variable se we can use it in if_changed and friends.
+
+.PHONY: $(PHONY)
-- 
1.7.11.4