botan: Implement prf+ via Botan's HKDF implementation

src/libstrongswan/plugins/botan/Makefile.am

@@ -16,6 +16,7 @@ libstrongswan_botan_la_SOURCES = \
 	botan_rng.h botan_rng.c \
 	botan_hasher.h botan_hasher.c \
 	botan_hmac.h botan_hmac.c \
+	botan_kdf.h botan_kdf.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_kdf.c

@@ -0,0 +1,185 @@
+/*
+ * Copyright (C) 2022 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.
+ */
+
+#define _GNU_SOURCE
+#include "botan_kdf.h"
+#include "botan_util.h"
+
+#include <botan/build.h>
+
+#ifdef BOTAN_HAS_HKDF
+
+#include <botan/ffi.h>
+
+typedef struct private_kdf_t private_kdf_t;
+
+/**
+ * Private data.
+ */
+struct private_kdf_t {
+
+	/**
+	 * Public interface.
+	 */
+	kdf_t public;
+
+	/**
+	 * Name of the KDF algorithm in Botan.
+	 */
+	char *name;
+
+	/**
+	 * Key for KDF.
+	 */
+	chunk_t key;
+
+	/**
+	 * Salt for KDF.
+	 */
+	chunk_t salt;
+
+#if BOTAN_VERSION_MAJOR == 2
+	/**
+	 * Used for a manual length check in get_bytes().
+	 */
+	size_t hash_size;
+#endif
+};
+
+METHOD(kdf_t, get_type, key_derivation_function_t,
+	private_kdf_t *this)
+{
+	return KDF_PRF_PLUS;
+}
+
+METHOD(kdf_t, get_bytes, bool,
+	private_kdf_t *this, size_t out_len, uint8_t *buffer)
+{
+#if BOTAN_VERSION_MAJOR == 2
+	/* Botan 2 doesn't check the length, just silently prevents wrapping the
+	 * counter and returns truncated output, so do this manually */
+	if (out_len > this->hash_size * 255)
+	{
+		return FALSE;
+	}
+#endif
+	if (botan_kdf(this->name, buffer, out_len, this->key.ptr, this->key.len,
+				  NULL, 0, this->salt.ptr, this->salt.len))
+	{
+		return FALSE;
+	}
+	return TRUE;
+}
+
+METHOD(kdf_t, allocate_bytes, bool,
+	private_kdf_t *this, size_t out_len, chunk_t *chunk)
+{
+	*chunk = chunk_alloc(out_len);
+
+	if (!get_bytes(this, out_len, chunk->ptr))
+	{
+		chunk_free(chunk);
+		return FALSE;
+	}
+	return TRUE;
+}
+
+METHOD(kdf_t, set_param, bool,
+	private_kdf_t *this, kdf_param_t param, ...)
+{
+	chunk_t chunk;
+
+	switch (param)
+	{
+		case KDF_PARAM_KEY:
+			VA_ARGS_GET(param, chunk);
+			chunk_clear(&this->key);
+			this->key = chunk_clone(chunk);
+			break;
+		case KDF_PARAM_SALT:
+			VA_ARGS_GET(param, chunk);
+			chunk_clear(&this->salt);
+			this->salt = chunk_clone(chunk);
+			break;
+	}
+	return TRUE;
+}
+
+METHOD(kdf_t, destroy, void,
+	private_kdf_t *this)
+{
+	chunk_clear(&this->salt);
+	chunk_clear(&this->key);
+	free(this->name);
+	free(this);
+}
+
+/*
+ * Described in header
+ */
+kdf_t *botan_kdf_create(key_derivation_function_t algo, va_list args)
+{
+	private_kdf_t *this;
+	pseudo_random_function_t prf_alg;
+	const char *hash_name;
+	char *name, buf[8];
+
+	if (algo != KDF_PRF_PLUS)
+	{
+		return NULL;
+	}
+
+	VA_ARGS_VGET(args, prf_alg);
+	hash_name = botan_get_hash(hasher_algorithm_from_prf(prf_alg));
+	if (!hash_name)
+	{
+		return NULL;
+	}
+	if (asprintf(&name, "HKDF-Expand(%s)", hash_name) <= 0)
+	{
+		return NULL;
+	}
+
+	INIT(this,
+		.public = {
+			.get_type = _get_type,
+			.get_bytes = _get_bytes,
+			.allocate_bytes = _allocate_bytes,
+			.set_param = _set_param,
+			.destroy = _destroy,
+		},
+		.name = name,
+#if BOTAN_VERSION_MAJOR == 2
+		.hash_size = hasher_hash_size(hasher_algorithm_from_prf(prf_alg)),
+#endif
+	);
+
+	/* test if we can actually use the algorithm */
+	if (!get_bytes(this, sizeof(buf), buf))
+	{
+		destroy(this);
+		return NULL;
+	}
+	return &this->public;
+}
+
+#endif

src/libstrongswan/plugins/botan/botan_kdf.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2022 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 derivation functions (KDF) using Botan, in particular prf+,
+ * which is implemented via Botan's HKDF implementation.
+ *
+ * @defgroup botan_kdf botan_kdf
+ * @{ @ingroup botan_p
+ */
+
+#ifndef BOTAN_KDF_H_
+#define BOTAN_KDF_H_
+
+#include <crypto/kdfs/kdf.h>
+
+/**
+ * Creates a new kdf_t object.
+ *
+ * @param algo		algorithm to instantiate
+ * @param args		algorithm-specific arguments
+ * @return			kdf_t object, NULL if not supported
+ */
+kdf_t *botan_kdf_create(key_derivation_function_t algo, va_list args);
+
+#endif /** BOTAN_KDF_H_ @}*/

src/libstrongswan/plugins/botan/botan_plugin.c

@@ -32,6 +32,7 @@
 #include "botan_crypter.h"
 #include "botan_diffie_hellman.h"
 #include "botan_hmac.h"
+#include "botan_kdf.h"
 #include "botan_rsa_public_key.h"
 #include "botan_rsa_private_key.h"
 #include "botan_ec_diffie_hellman.h"
@@ -209,6 +210,12 @@ METHOD(plugin_t, get_features, int,
 #endif
 #endif /* BOTAN_HAS_HMAC */
 
+		/* kdfs */
+#ifdef BOTAN_HAS_HKDF
+		PLUGIN_REGISTER(SIGNER, botan_kdf_create),
+			PLUGIN_PROVIDE(KDF, KDF_PRF_PLUS),
+#endif /* BOTAN_HAS_HKDF */
+
 		/* generic key loaders */
 #if defined (BOTAN_HAS_RSA) || defined(BOTAN_HAS_ECDSA) || \
 	defined(BOTAN_HAS_ED25519)

src/libstrongswan/tests/suites/test_prf_plus.c

@@ -137,7 +137,13 @@ START_TEST(test_wrap)
 
 	/* the 1-byte counter overflows after 255 blocks of the underlying PRF */
 	out = chunk_alloc(32 * 255 + 1);
-	ck_assert(kdf->get_bytes(kdf, out.len - 1 , out.ptr));
+	ck_assert(kdf->get_bytes(kdf, out.len - 2, out.ptr));
+	if (!kdf->get_bytes(kdf, out.len - 1, out.ptr))
+	{	/* Botan 3.x has a check for (len/bs) >= 255 blocks, so we allow this */
+		warn("unable to generate maximum-sized key for %N (%N) but maximum-1 "
+			 "is fine", key_derivation_function_names, KDF_PRF_PLUS,
+			 pseudo_random_function_names, PRF_HMAC_SHA2_256);
+	}
 	ck_assert(!kdf->get_bytes(kdf, out.len, out.ptr));
 	chunk_free(&out);
 	kdf->destroy(kdf);

src/libstrongswan/utils/leak_detective.c

@@ -637,6 +637,7 @@ static char *whitelist[] = {
 	"botan_privkey_create",
 	"botan_privkey_load_ecdh",
 	"botan_privkey_load",
+	"botan_kdf",
 };
 
 /**

testing/tests/botan/net2net-ed25519/hosts/moon/etc/strongswan.conf

@@ -5,5 +5,5 @@ swanctl {
 }
 
 charon-systemd {
-  load = random nonce kdf pem botan x509 revocation constraints curl kernel-netlink socket-default updown vici
+  load = random nonce pem botan x509 revocation constraints curl kernel-netlink socket-default updown vici
 }

testing/tests/botan/net2net-pkcs12/hosts/moon/etc/strongswan.conf

@@ -5,5 +5,5 @@ swanctl {
 }
 
 charon-systemd {
-  load = pem nonce kdf botan x509 revocation constraints curl vici kernel-netlink socket-default updown
+  load = pem nonce botan x509 revocation constraints curl vici kernel-netlink socket-default updown
 }

testing/tests/botan/net2net-pkcs12/hosts/sun/etc/strongswan.conf

@@ -5,5 +5,5 @@ swanctl {
 }
 
 charon-systemd {
-  load = pem nonce kdf botan x509 revocation constraints curl vici kernel-netlink socket-default updown
+  load = pem nonce botan x509 revocation constraints curl vici kernel-netlink socket-default updown
 }

testing/tests/botan/net2net-sha3-rsa-cert/hosts/moon/etc/strongswan.conf

@@ -5,5 +5,5 @@ swanctl {
 }
 
 charon-systemd {
-  load = random nonce kdf pem x509 revocation constraints pubkey botan curl kernel-netlink socket-default updown vici
+  load = random nonce pem x509 revocation constraints pubkey botan curl kernel-netlink socket-default updown vici
 }

testing/tests/botan/net2net-sha3-rsa-cert/hosts/sun/etc/strongswan.conf

@@ -5,5 +5,5 @@ swanctl {
 }
 
 charon-systemd {
-  load = random nonce kdf pem x509 revocation constraints pubkey botan curl kernel-netlink socket-default updown vici
+  load = random nonce pem x509 revocation constraints pubkey botan curl kernel-netlink socket-default updown vici
 }

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

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

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

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

testing/tests/botan/rw-ecp256/hosts/carol/etc/strongswan.conf

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

testing/tests/botan/rw-ecp256/hosts/moon/etc/strongswan.conf

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

testing/tests/botan/rw-modp3072/hosts/carol/etc/strongswan.conf

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

testing/tests/botan/rw-modp3072/hosts/moon/etc/strongswan.conf

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