modsign: Use single PEM file for autogenerated key

The current rule for generating signing_key.priv and signing_key.x509 is
a classic example of a bad rule which has a tendency to break parallel
make. When invoked to create *either* target, it generates the other
target as a side-effect that make didn't predict.

So let's switch to using a single file signing_key.pem which contains
both key and certificate. That matches what we do in the case of an
external key specified by CONFIG_MODULE_SIG_KEY anyway, so it's also
slightly cleaner.

Signed-off-by: David Woodhouse <[email protected]>
Signed-off-by: David Howells <[email protected]>

.gitignore

@@ -97,6 +97,7 @@ GTAGS
 # Leavings from module signing
 #
 extra_certificates
+signing_key.pem
 signing_key.priv
 signing_key.x509
 x509.genkey

Documentation/module-signing.txt

@@ -91,7 +91,7 @@ This has a number of options available:
  (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
-     "signing_key.priv" will disable the autogeneration of signing keys and
+     "signing_key.pem" 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 both a private
      key and its corresponding X.509 certificate in PEM form, or — on
@@ -116,11 +116,10 @@ kernel so that it can be used to check the signatures as the modules are
 loaded.
 
 Under normal conditions, when CONFIG_MODULE_SIG_KEY is unchanged from its
-default of "signing_key.priv", the kernel build will automatically generate
-a new keypair using openssl if one does not exist in the files:
+default, the kernel build will automatically generate a new keypair using
+openssl if one does not exist in the file:
 
-	signing_key.priv
-	signing_key.x509
+	signing_key.pem
 
 during the building of vmlinux (the public part of the key needs to be built
 into vmlinux) using parameters in the:

Makefile

@@ -1173,8 +1173,8 @@ MRPROPER_DIRS  += include/config usr/include include/generated          \
 		  arch/*/include/generated .tmp_objdiff
 MRPROPER_FILES += .config .config.old .version .old_version \
 		  Module.symvers tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS \
-		  signing_key.priv signing_key.x509 x509.genkey		\
-		  extra_certificates signing_key.x509.keyid		\
+		  signing_key.pem signing_key.priv signing_key.x509	\
+		  x509.genkey extra_certificates signing_key.x509.keyid	\
 		  signing_key.x509.signer vmlinux-gdb.py
 
 # clean - Delete most, but leave enough to build external modules

init/Kconfig

@@ -1950,15 +1950,15 @@ config MODULE_SIG_HASH
 
 config MODULE_SIG_KEY
 	string "File name or PKCS#11 URI of module signing key"
-	default "signing_key.priv"
+	default "signing_key.pem"
 	depends on MODULE_SIG
 	help
          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",
+         If this option is unchanged from its default "signing_key.pem",
          then the kernel will automatically generate the private key and
          certificate as described in Documentation/module-signing.txt
 

kernel/Makefile

@@ -173,8 +173,8 @@ endif
 # We do it this way rather than having a boolean option for enabling an
 # external private key, because 'make randconfig' might enable such a
 # boolean option and we unfortunately can't make it depend on !RANDCONFIG.
-ifeq ($(CONFIG_MODULE_SIG_KEY),"signing_key.priv")
-signing_key.priv signing_key.x509: x509.genkey
+ifeq ($(CONFIG_MODULE_SIG_KEY),"signing_key.pem")
+signing_key.pem: x509.genkey
 	@echo "###"
 	@echo "### Now generating an X.509 key pair to be used for signing modules."
 	@echo "###"
@@ -185,8 +185,8 @@ signing_key.priv signing_key.x509: x509.genkey
 	@echo "###"
 	openssl req -new -nodes -utf8 -$(CONFIG_MODULE_SIG_HASH) -days 36500 \
 		-batch -x509 -config x509.genkey \
-		-outform DER -out signing_key.x509 \
-		-keyout signing_key.priv 2>&1
+		-outform PEM -out signing_key.pem \
+		-keyout signing_key.pem 2>&1
 	@echo "###"
 	@echo "### Key pair generated."
 	@echo "###"
@@ -210,9 +210,9 @@ 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.
+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
 
@@ -249,4 +249,3 @@ endif
 signing_key.x509: scripts/extract-cert include/config/module/sig/key.h $(X509_DEP)
 	$(call cmd,extract_der,$(X509_SOURCE))
 endif
-endif