botan: Add support for ML-KEM

scripts/test.sh

@@ -235,8 +235,8 @@ gcrypt)
 	DEPS="libgcrypt20-dev"
 	;;
 botan)
-	CONFIG="--disable-defaults --enable-pki --enable-botan --enable-pem --enable-hmac --enable-x509 --enable-constraints"
-	export TESTS_PLUGINS="test-vectors botan! pem hmac x509 constraints"
+	CONFIG="--disable-defaults --enable-pki --enable-botan --enable-pem --enable-hmac --enable-x509 --enable-constraints --enable-drbg"
+	export TESTS_PLUGINS="test-vectors botan! pem hmac x509 constraints drbg"
 	DEPS=""
 	if test "$1" = "build-deps"; then
 		build_botan

src/libstrongswan/plugins/botan/Makefile.am

@@ -17,6 +17,7 @@ libstrongswan_botan_la_SOURCES = \
 	botan_hasher.h botan_hasher.c \
 	botan_hmac.h botan_hmac.c \
 	botan_kdf.h botan_kdf.c \
+	botan_kem.h botan_kem.c \
 	botan_crypter.h botan_crypter.c \
 	botan_rsa_public_key.h botan_rsa_public_key.c \
 	botan_rsa_private_key.h botan_rsa_private_key.c \

src/libstrongswan/plugins/botan/botan_kem.c

@@ -0,0 +1,355 @@
+/*
+ * Copyright (C) 2024 Tobias Brunner, codelabs GmbH
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "botan_kdf.h"
+#include "botan_util.h"
+
+#include <botan/build.h>
+
+#ifdef BOTAN_HAS_ML_KEM
+
+#include <botan/ffi.h>
+
+/**
+ * Length of the private key seed (d || z).
+ */
+#define ML_KEM_SEED_LEN 64
+
+/**
+ * Length of the shared secret.
+ */
+#define ML_KEM_SHARED_LEN 32
+
+typedef struct private_key_exchange_t private_key_exchange_t;
+
+/**
+ * Private data.
+ */
+struct private_key_exchange_t {
+
+	/**
+	 * Public interface.
+	 */
+	key_exchange_t public;
+
+	/**
+	 * KE method.
+	 */
+	key_exchange_method_t method;
+
+	/**
+	 * Internal algorithm name.
+	 */
+	char *name;
+
+	/**
+	 * Key pair as initiator.
+	 */
+	botan_privkey_t kem;
+
+	/**
+	 * Ciphertext as responder.
+	 */
+	chunk_t ciphertext;
+
+	/**
+	 * Shared secret.
+	 */
+	chunk_t shared_secret;
+
+	/**
+	 * DRBG for testing.
+	 */
+	drbg_t *drbg;
+};
+
+CALLBACK(get_random, int,
+	drbg_t *drbg, uint8_t *out, size_t out_len)
+{
+	if (!drbg->generate(drbg, out_len, out))
+	{
+		return -1;
+	}
+	return 0;
+}
+
+/**
+ * Initializes the given RNG, either based on a DRBG during testing or using
+ * the plugin's configured RNG.
+ */
+static bool get_rng(private_key_exchange_t *this, botan_rng_t *rng)
+{
+	if (this->drbg)
+	{
+		return !botan_rng_init_custom(rng, "kem-drbg", this->drbg,
+									  get_random, NULL, NULL);
+	}
+	return botan_get_rng(rng, RNG_STRONG);
+}
+
+/**
+ * Convert the given "view" to a chunk.
+ */
+CALLBACK(botan_view_to_chunk, int,
+	chunk_t *chunk, const uint8_t *data, size_t len)
+{
+	*chunk = chunk_clone(chunk_create((u_char*)data, len));
+	return 0;
+}
+
+/**
+ * Generate a key pair as initiator.
+ */
+static bool generate_keypair(private_key_exchange_t *this)
+{
+	if (this->drbg)
+	{
+		uint8_t random[ML_KEM_SEED_LEN];
+
+		/* during testing, we load the DRBG-generated seed (d || z) as private
+		 * key, as Botan would otherwise pull these separately from the RNG */
+		if (!this->drbg->generate(this->drbg, sizeof(random), random) ||
+			botan_privkey_load_ml_kem(&this->kem, random, sizeof(random),
+									  this->name))
+		{
+			return FALSE;
+		}
+	}
+	else
+	{
+		botan_rng_t rng = NULL;
+
+		if (!botan_get_rng(&rng, RNG_STRONG) ||
+			botan_privkey_create(&this->kem, "ML-KEM", this->name, rng))
+		{
+			botan_rng_destroy(rng);
+			return FALSE;
+		}
+		botan_rng_destroy(rng);
+	}
+	return TRUE;
+}
+
+/**
+ * Export the public key of the generated key pair as initiator.
+ */
+static bool export_pubkey(private_key_exchange_t *this, chunk_t *public)
+{
+	botan_pubkey_t pubkey = NULL;
+
+	if (!this->kem && !generate_keypair(this))
+	{
+		DBG1(DBG_LIB, "%N key pair generation failed",
+			 key_exchange_method_names, this->method);
+		return FALSE;
+	}
+
+	if (botan_privkey_export_pubkey(&pubkey, this->kem) ||
+		botan_pubkey_view_raw(pubkey, public, botan_view_to_chunk))
+	{
+		DBG1(DBG_LIB, "%N public key encoding failed",
+				 key_exchange_method_names, this->method);
+		botan_pubkey_destroy(pubkey);
+		return FALSE;
+	}
+	botan_pubkey_destroy(pubkey);
+	return TRUE;
+}
+
+METHOD(key_exchange_t, get_public_key, bool,
+	private_key_exchange_t *this, chunk_t *value)
+{
+	/* as responder, this method is called after set_public_key(), which
+	 * encapsulated the secret to produce this ciphertext */
+	if (this->ciphertext.len)
+	{
+		*value = chunk_clone(this->ciphertext);
+		return TRUE;
+	}
+
+	/* as initiator, we generate a key pair and return the public key */
+	return export_pubkey(this, value);
+}
+
+/**
+ * Decapsulate the shared secret from the given ciphertext using our key pair.
+ */
+static bool decaps_ciphertext(private_key_exchange_t *this, chunk_t ciphertext)
+{
+	botan_pk_op_kem_decrypt_t op;
+
+	if (botan_pk_op_kem_decrypt_create(&op, this->kem, "Raw"))
+	{
+		return FALSE;
+	}
+	this->shared_secret = chunk_alloc(ML_KEM_SHARED_LEN);
+
+	if (botan_pk_op_kem_decrypt_shared_key(op, NULL, 0, ciphertext.ptr,
+							ciphertext.len, this->shared_secret.len,
+							this->shared_secret.ptr, &this->shared_secret.len))
+	{
+		DBG1(DBG_LIB, "%N decapsulation failed",
+			 key_exchange_method_names, this->method);
+		botan_pk_op_kem_decrypt_destroy(op);
+		return FALSE;
+	}
+	botan_pk_op_kem_decrypt_destroy(op);
+	return TRUE;
+}
+
+/**
+ * Generate a shared secret an encapsulate it using the given public key.
+ */
+static bool encaps_shared_secret(private_key_exchange_t *this, chunk_t public)
+{
+	botan_pk_op_kem_encrypt_t op;
+	botan_pubkey_t kem;
+	botan_rng_t rng;
+	size_t len;
+
+	if (botan_pubkey_load_ml_kem(&kem, public.ptr, public.len, this->name))
+	{
+		DBG1(DBG_LIB, "%N public key invalid",
+			 key_exchange_method_names, this->method);
+		return FALSE;
+	}
+	if (botan_pk_op_kem_encrypt_create(&op, kem, "Raw"))
+	{
+		botan_pubkey_destroy(kem);
+		return FALSE;
+	}
+	if (botan_pk_op_kem_encrypt_encapsulated_key_length(op, &len) ||
+		!get_rng(this, &rng))
+	{
+		botan_pk_op_kem_encrypt_destroy(op);
+		botan_pubkey_destroy(kem);
+		return FALSE;
+	}
+	this->ciphertext = chunk_alloc(len);
+	this->shared_secret = chunk_alloc(ML_KEM_SHARED_LEN);
+
+	if (botan_pk_op_kem_encrypt_create_shared_key(op, rng, NULL, 0,
+							this->shared_secret.len,
+							this->shared_secret.ptr, &this->shared_secret.len,
+							this->ciphertext.ptr, &this->ciphertext.len))
+	{
+		DBG1(DBG_LIB, "%N encapsulation failed",
+			 key_exchange_method_names, this->method);
+		botan_pk_op_kem_encrypt_destroy(op);
+		botan_pubkey_destroy(kem);
+		botan_rng_destroy(rng);
+		return FALSE;
+	}
+	botan_pk_op_kem_encrypt_destroy(op);
+	botan_pubkey_destroy(kem);
+	botan_rng_destroy(rng);
+	return TRUE;
+}
+
+METHOD(key_exchange_t, set_public_key, bool,
+	private_key_exchange_t *this, chunk_t value)
+{
+	/* as initiator, we decapsulate the secret from the given ciphertext */
+	if (this->kem)
+	{
+		return decaps_ciphertext(this, value);
+	}
+
+	/* as responder, we generate a secret and encapsulate it */
+	return encaps_shared_secret(this, value);
+}
+
+METHOD(key_exchange_t, get_shared_secret, bool,
+	private_key_exchange_t *this, chunk_t *secret)
+{
+	*secret = chunk_clone(this->shared_secret);
+	return TRUE;
+}
+
+METHOD(key_exchange_t, get_method, key_exchange_method_t,
+	private_key_exchange_t *this)
+{
+	return this->method;
+}
+
+METHOD(key_exchange_t, set_seed, bool,
+	private_key_exchange_t *this, chunk_t value, drbg_t *drbg)
+{
+	if (!drbg)
+	{
+		return FALSE;
+	}
+	DESTROY_IF(this->drbg);
+	this->drbg = drbg->get_ref(drbg);
+	return TRUE;
+}
+
+METHOD(key_exchange_t, destroy, void,
+	private_key_exchange_t *this)
+{
+	chunk_clear(&this->shared_secret);
+	chunk_free(&this->ciphertext);
+	botan_privkey_destroy(this->kem);
+	DESTROY_IF(this->drbg);
+	free(this->name);
+	free(this);
+}
+
+/*
+ * Described in header
+ */
+key_exchange_t *botan_kem_create(key_exchange_method_t method)
+{
+	private_key_exchange_t *this;
+	char *name;
+
+	switch (method)
+	{
+		case ML_KEM_512:
+			name = "ML-KEM-512";
+			break;
+		case ML_KEM_768:
+			name = "ML-KEM-768";
+			break;
+		case ML_KEM_1024:
+			name = "ML-KEM-1024";
+			break;
+		default:
+			return NULL;
+	}
+
+	INIT(this,
+		.public = {
+			.get_method = _get_method,
+			.get_public_key = _get_public_key,
+			.set_public_key = _set_public_key,
+			.get_shared_secret = _get_shared_secret,
+			.set_seed = _set_seed,
+			.destroy = _destroy,
+		},
+		.method = method,
+		.name = strdup(name),
+	);
+	return &this->public;
+}
+
+#endif /* BOTAN_HAS_ML_KEM */

src/libstrongswan/plugins/botan/botan_kem.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2024 Tobias Brunner, codelabs GmbH
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ * Implements key encapsulation methods (KEM) using Botan.
+ *
+ * @defgroup botan_kem botan_kem
+ * @{ @ingroup botan_p
+ */
+
+#ifndef BOTAN_KEM_H_
+#define BOTAN_KEM_H_
+
+#include <crypto/key_exchange.h>
+
+/**
+ * Creates a new key_exchange_t object.
+ *
+ * @param method	KEM to instantiate
+ * @return			key_exchange_t object, NULL if not supported
+ */
+key_exchange_t *botan_kem_create(key_exchange_method_t method);
+
+#endif /** BOTAN_KEM_H_ @}*/

src/libstrongswan/plugins/botan/botan_plugin.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2018 Tobias Brunner
+ * Copyright (C) 2018-2024 Tobias Brunner
  * Copyright (C) 2018 Andreas Steffen
  *
  * Copyright (C) 2018 René Korthaus
@@ -32,6 +32,7 @@
 #include "botan_diffie_hellman.h"
 #include "botan_hmac.h"
 #include "botan_kdf.h"
+#include "botan_kem.h"
 #include "botan_rsa_public_key.h"
 #include "botan_rsa_private_key.h"
 #include "botan_ec_diffie_hellman.h"
@@ -360,6 +361,13 @@ METHOD(plugin_t, get_features, int,
 			PLUGIN_PROVIDE(HASHER, HASH_IDENTITY),
 #endif
 
+#ifdef BOTAN_HAS_ML_KEM
+		PLUGIN_REGISTER(KE, botan_kem_create),
+			PLUGIN_PROVIDE(KE, ML_KEM_512),
+			PLUGIN_PROVIDE(KE, ML_KEM_768),
+			PLUGIN_PROVIDE(KE, ML_KEM_1024),
+#endif
+
 		/* random numbers */
 #if BOTAN_HAS_SYSTEM_RNG
 #if BOTAN_HAS_HMAC_DRBG

testing/tests/botan/rw-cert/hosts/moon/etc/strongswan.conf

@@ -5,7 +5,7 @@ swanctl {
 }
 
 charon-systemd {
-  load = nonce test-vectors botan pem x509 revocation constraints pubkey curl kernel-netlink socket-default updown vici
+  load = nonce test-vectors drbg botan pem x509 revocation constraints pubkey curl kernel-netlink socket-default updown vici
 
   rsa_pss = yes
   integrity_test = yes