modsign: Enable ML-DSA module signing

Allow ML-DSA module signing to be enabled.

Note that OpenSSL's CMS_*() function suite does not, as of OpenSSL-3.6,
support the use of CMS_NOATTR with ML-DSA, so the prohibition against using
signedAttrs with module signing has to be removed.  The selected digest
then applies only to the algorithm used to calculate the digest stored in
the messageDigest attribute.  The OpenSSL development branch has patches
applied that fix this[1], but it appears that that will only be available
in OpenSSL-4.

[1] openssl/openssl#28923

sign-file won't set CMS_NOATTR if openssl is earlier than v4, resulting in
the use of signed attributes.

The ML-DSA algorithm takes the raw data to be signed without regard to what
digest algorithm is specified in the CMS message.  The CMS specified digest
algorithm is ignored unless signedAttrs are used; in such a case, only
SHA512 is permitted.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jarkko Sakkinen <jarkko@kernel.org>
cc: Eric Biggers <ebiggers@kernel.org>
cc: Lukas Wunner <lukas@wunner.de>
cc: Ignat Korchagin <ignat@cloudflare.com>
cc: Stephan Mueller <smueller@chronox.de>
cc: Herbert Xu <herbert@gondor.apana.org.au>
cc: keyrings@vger.kernel.org
cc: linux-crypto@vger.kernel.org

Author: dhowells

Documentation/admin-guide/module-signing.rst

@@ -28,10 +28,12 @@ trusted userspace bits.
 
 This facility uses X.509 ITU-T standard certificates to encode the public keys
 involved.  The signatures are not themselves encoded in any industrial standard
-type.  The built-in facility currently only supports the RSA & NIST P-384 ECDSA
-public key signing standard (though it is pluggable and permits others to be
-used).  The possible hash algorithms that can be used are SHA-2 and SHA-3 of
-sizes 256, 384, and 512 (the algorithm is selected by data in the signature).
+type.  The built-in facility currently only supports the RSA, NIST P-384 ECDSA
+and NIST FIPS-204 ML-DSA public key signing standards (though it is pluggable
+and permits others to be used).  For RSA and ECDSA, the possible hash
+algorithms that can be used are SHA-2 and SHA-3 of sizes 256, 384, and 512 (the
+algorithm is selected by data in the signature); ML-DSA does its own hashing,
+but is allowed to be used with a SHA512 hash for signed attributes.
 
 
 ==========================
@@ -146,9 +148,9 @@ into vmlinux) using parameters in the::
 
 file (which is also generated if it does not already exist).
 
-One can select between RSA (``MODULE_SIG_KEY_TYPE_RSA``) and ECDSA
-(``MODULE_SIG_KEY_TYPE_ECDSA``) to generate either RSA 4k or NIST
-P-384 keypair.
+One can select between RSA (``MODULE_SIG_KEY_TYPE_RSA``), ECDSA
+(``MODULE_SIG_KEY_TYPE_ECDSA``) and ML-DSA (``MODULE_SIG_KEY_TYPE_MLDSA_*``) to
+generate an RSA 4k, a NIST P-384 keypair or an ML-DSA 44, 65 or 87 keypair.
 
 It is strongly recommended that you provide your own x509.genkey file.
 

certs/Kconfig

@@ -39,6 +39,39 @@ config MODULE_SIG_KEY_TYPE_ECDSA
 	 Note: Remove all ECDSA signing keys, e.g. certs/signing_key.pem,
 	 when falling back to building Linux 5.14 and older kernels.
 
+config MODULE_SIG_KEY_TYPE_MLDSA_44
+	bool "ML-DSA-44"
+	select CRYPTO_MLDSA
+	depends on OPENSSL_SUPPORTS_ML_DSA
+	help
+	  Use an ML-DSA-44 key (NIST FIPS 204) for module signing.  ML-DSA
+	  support requires OpenSSL-3.5 minimum; preferably OpenSSL-4+.  With
+	  the latter, the entire module body will be signed; with the former,
+	  signedAttrs will be used as it lacks support for CMS_NOATTR with
+	  ML-DSA.
+
+config MODULE_SIG_KEY_TYPE_MLDSA_65
+	bool "ML-DSA-65"
+	select CRYPTO_MLDSA
+	depends on OPENSSL_SUPPORTS_ML_DSA
+	help
+	  Use an ML-DSA-65 key (NIST FIPS 204) for module signing.  ML-DSA
+	  support requires OpenSSL-3.5 minimum; preferably OpenSSL-4+.  With
+	  the latter, the entire module body will be signed; with the former,
+	  signedAttrs will be used as it lacks support for CMS_NOATTR with
+	  ML-DSA.
+
+config MODULE_SIG_KEY_TYPE_MLDSA_87
+	bool "ML-DSA-87"
+	select CRYPTO_MLDSA
+	depends on OPENSSL_SUPPORTS_ML_DSA
+	help
+	  Use an ML-DSA-87 key (NIST FIPS 204) for module signing.  ML-DSA
+	  support requires OpenSSL-3.5 minimum; preferably OpenSSL-4+.  With
+	  the latter, the entire module body will be signed; with the former,
+	  signedAttrs will be used as it lacks support for CMS_NOATTR with
+	  ML-DSA.
+
 endchoice
 
 config SYSTEM_TRUSTED_KEYRING
@@ -154,4 +187,11 @@ config SYSTEM_BLACKLIST_AUTH_UPDATE
 	  keyring.  The PKCS#7 signature of the description is set in the key
 	  payload.  Blacklist keys cannot be removed.
 
+config OPENSSL_SUPPORTS_ML_DSA
+	def_bool $(success, openssl list -key-managers | grep -q ML-DSA-87)
+	help
+	  Support for ML-DSA-44/65/87 was added in openssl-3.5, so as long
+	  as older versions are supported, the key types may only be
+	  set after testing the installed binary for support.
+
 endmenu

certs/Makefile

@@ -43,6 +43,9 @@ targets += x509_certificate_list
 ifeq ($(CONFIG_MODULE_SIG_KEY),certs/signing_key.pem)
 
 keytype-$(CONFIG_MODULE_SIG_KEY_TYPE_ECDSA) := -newkey ec -pkeyopt ec_paramgen_curve:secp384r1
+keytype-$(CONFIG_MODULE_SIG_KEY_TYPE_MLDSA_44) := -newkey ml-dsa-44
+keytype-$(CONFIG_MODULE_SIG_KEY_TYPE_MLDSA_65) := -newkey ml-dsa-65
+keytype-$(CONFIG_MODULE_SIG_KEY_TYPE_MLDSA_87) := -newkey ml-dsa-87
 
 quiet_cmd_gen_key = GENKEY  $@
       cmd_gen_key = openssl req -new -nodes -utf8 -$(CONFIG_MODULE_SIG_HASH) -days 36500 \

scripts/sign-file.c

@@ -27,7 +27,7 @@
 #include <openssl/evp.h>
 #include <openssl/pem.h>
 #include <openssl/err.h>
-#if OPENSSL_VERSION_MAJOR >= 3
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L
 # define USE_PKCS11_PROVIDER
 # include <openssl/provider.h>
 # include <openssl/store.h>
@@ -315,18 +315,39 @@ int main(int argc, char **argv)
 		ERR(!digest_algo, "EVP_get_digestbyname");
 
 #ifndef USE_PKCS7
+
+		unsigned int flags =
+			CMS_NOCERTS |
+			CMS_PARTIAL |
+			CMS_BINARY |
+			CMS_DETACHED |
+			CMS_STREAM  |
+			CMS_NOSMIMECAP |
+#ifdef CMS_NO_SIGNING_TIME
+			CMS_NO_SIGNING_TIME |
+#endif
+			use_keyid;
+
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L && OPENSSL_VERSION_NUMBER < 0x40000000L
+		if (EVP_PKEY_is_a(private_key, "ML-DSA-44") ||
+		    EVP_PKEY_is_a(private_key, "ML-DSA-65") ||
+		    EVP_PKEY_is_a(private_key, "ML-DSA-87")) {
+			 /* ML-DSA + CMS_NOATTR is not supported in openssl-3.5
+			  * and before.
+			  */
+			use_signed_attrs = 0;
+		}
+#endif
+
+		flags |= use_signed_attrs;
+
 		/* Load the signature message from the digest buffer. */
-		cms = CMS_sign(NULL, NULL, NULL, NULL,
-			       CMS_NOCERTS | CMS_PARTIAL | CMS_BINARY |
-			       CMS_DETACHED | CMS_STREAM);
+		cms = CMS_sign(NULL, NULL, NULL, NULL, flags);
 		ERR(!cms, "CMS_sign");
 
-		ERR(!CMS_add1_signer(cms, x509, private_key, digest_algo,
-				     CMS_NOCERTS | CMS_BINARY |
-				     CMS_NOSMIMECAP | use_keyid |
-				     use_signed_attrs),
+		ERR(!CMS_add1_signer(cms, x509, private_key, digest_algo, flags),
 		    "CMS_add1_signer");
-		ERR(CMS_final(cms, bm, NULL, CMS_NOCERTS | CMS_BINARY) != 1,
+		ERR(CMS_final(cms, bm, NULL, flags) != 1,
 		    "CMS_final");
 
 #else