certs: Add FIPS selftests

Add some selftests for signature checking when FIPS mode is enabled.  These
need to be done before we start actually using the signature checking for
things and must panic the kernel upon failure.

Note that the tests must not check the blacklist lest this provide a way to
prevent a kernel from booting by installing a hash of a test key in the
appropriate UEFI table.
Reported-by: Simo Sorce <simo@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Reviewed-by: Herbert Xu <herbert@gondor.apana.org.au>
cc: keyrings@vger.kernel.org
cc: linux-crypto@vger.kernel.org
Link: https://lore.kernel.org/r/165515742832.1554877.2073456606206090838.stgit@warthog.procyon.org.uk/

crypto/asymmetric_keys/Kconfig

@@ -75,4 +75,14 @@ config SIGNED_PE_FILE_VERIFICATION
 	  This option provides support for verifying the signature(s) on a
 	  signed PE binary.
 
+config FIPS_SIGNATURE_SELFTEST
+	bool "Run FIPS selftests on the X.509+PKCS7 signature verification"
+	help
+	  This option causes some selftests to be run on the signature
+	  verification code, using some built in data.  This is required
+	  for FIPS.
+	depends on KEYS
+	depends on ASYMMETRIC_KEY_TYPE
+	depends on PKCS7_MESSAGE_PARSER
+
 endif # ASYMMETRIC_KEY_TYPE

crypto/asymmetric_keys/Makefile

@@ -22,6 +22,7 @@ x509_key_parser-y := \
 	x509_cert_parser.o \
 	x509_loader.o \
 	x509_public_key.o
+x509_key_parser-$(CONFIG_FIPS_SIGNATURE_SELFTEST) += selftest.o
 
 $(obj)/x509_cert_parser.o: \
 	$(obj)/x509.asn1.h \

crypto/asymmetric_keys/x509_parser.h

@@ -40,6 +40,15 @@ struct x509_certificate {
 	bool		blacklisted;
 };
 
+/*
+ * selftest.c
+ */
+#ifdef CONFIG_FIPS_SIGNATURE_SELFTEST
+extern int __init fips_signature_selftest(void);
+#else
+static inline int fips_signature_selftest(void) { return 0; }
+#endif
+
 /*
  * x509_cert_parser.c
  */

crypto/asymmetric_keys/x509_public_key.c

@@ -244,9 +244,15 @@ static struct asymmetric_key_parser x509_key_parser = {
 /*
  * Module stuff
  */
+extern int __init certs_selftest(void);
 static int __init x509_key_init(void)
 {
-	return register_asymmetric_key_parser(&x509_key_parser);
+	int ret;
+
+	ret = register_asymmetric_key_parser(&x509_key_parser);
+	if (ret < 0)
+		return ret;
+	return fips_signature_selftest();
 }
 
 static void __exit x509_key_exit(void)