libtls: Add TLS 1.3 implementation of tls_aead_t

The key material, in particular the nonce/IV, is derived differently and
the IV is also generated in a different way.  Additionally, the actual
content type is encrypted and there may be optional padding to mask the
actual size of the encrypted data.

src/libcharon/Android.mk

@@ -220,10 +220,10 @@ ifneq ($(or $(call plugin_enabled, eap-tls), $(call plugin_enabled, eap-ttls), \
 			$(call plugin_enabled, eap-peap), $(call plugin_enabled, eap-tnc)),)
 LOCAL_C_INCLUDES += $(LOCAL_PATH)/../libtls/
 LOCAL_SRC_FILES += $(addprefix ../libtls/, \
-		tls_protection.c tls_compression.c tls_fragmentation.c tls_alert.c \
-		tls_crypto.c tls_prf.c tls_socket.c tls_eap.c tls_cache.c tls_peer.c \
-		tls_aead_expl.c tls_aead_impl.c tls_aead_null.c tls_aead.c \
-		tls_server.c tls.c \
+	tls_protection.c tls_compression.c tls_fragmentation.c tls_alert.c \
+	tls_crypto.c tls_prf.c tls_socket.c tls_eap.c tls_cache.c tls_peer.c \
+	tls_aead_expl.c tls_aead_impl.c tls_aead_null.c tls_aead_seq.c tls_aead.c \
+	tls_server.c tls.c \
 	)
 endif
 

src/libtls/Makefile.am

@@ -11,7 +11,7 @@ ipseclib_LTLIBRARIES = libtls.la
 libtls_la_SOURCES = \
 	tls_protection.c tls_compression.c tls_fragmentation.c tls_alert.c \
 	tls_crypto.c tls_prf.c tls_socket.c tls_eap.c tls_cache.c tls_peer.c \
-	tls_aead_expl.c tls_aead_impl.c tls_aead_null.c tls_aead.c \
+	tls_aead_expl.c tls_aead_impl.c tls_aead_null.c tls_aead_seq.c tls_aead.c \
 	tls_server.c tls.c
 
 libtls_la_LIBADD = \

src/libtls/tls_aead.h

@@ -1,4 +1,7 @@
 /*
+ * Copyright (C) 2020 Tobias Brunner
+ * HSR Hochschule fuer Technik Rapperswil
+ *
  * Copyright (C) 2014 Martin Willi
  * Copyright (C) 2014 revosec AG
  *
@@ -147,10 +150,27 @@ tls_aead_t *tls_aead_create_null(integrity_algorithm_t mac);
 /**
  * Create a tls_aead instance using real a AEAD cipher.
  *
+ * The sequence number is used as IV directly. The internally used nonce
+ * is derived from the key material. Used for TLS 1.2.
+ *
  * @param encr			AEAD encryption algorithm
  * @param encr_size		encryption key size, in bytes
  * @return				TLS AEAD transform
  */
 tls_aead_t *tls_aead_create_aead(encryption_algorithm_t encr, size_t encr_size);
 
+/**
+ * Create a tls_aead instance using real a AEAD cipher and sequence number
+ * as IV.
+ *
+ * The sequence number XORed with a static value of at least the same length
+ * that is derived from the key material is used as IV. This is what TLS 1.3
+ * and newer uses.
+ *
+ * @param encr			AEAD encryption algorithm
+ * @param encr_size		encryption key size, in bytes
+ * @return				TLS AEAD transform
+ */
+tls_aead_t *tls_aead_create_seq(encryption_algorithm_t encr, size_t encr_size);
+
 #endif /** TLS_AEAD_H_ @}*/

src/libtls/tls_aead_seq.c

@@ -0,0 +1,264 @@
+/*
+ * Copyright (C) 2020 Tobias Brunner
+ * HSR Hochschule fuer Technik Rapperswil
+ *
+ * Copyright (C) 2014 Martin Willi
+ * Copyright (C) 2014 revosec AG
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+#include "tls_aead.h"
+
+#include <bio/bio_writer.h>
+
+typedef struct private_tls_aead_t private_tls_aead_t;
+
+/**
+ * Private data of an tls_aead_t object.
+ */
+struct private_tls_aead_t {
+
+	/**
+	 * Public tls_aead_t interface.
+	 */
+	tls_aead_t public;
+
+	/**
+	 * AEAD transform.
+	 */
+	aead_t *aead;
+
+	/**
+	 * IV derived from key material.
+	 */
+	chunk_t iv;
+
+	/**
+	 * Size of the salt that's internally used by the AEAD implementation.
+	 */
+	size_t salt;
+};
+
+/**
+ * Additional data for AEAD (record header)
+ */
+typedef struct __attribute__((__packed__)) {
+	uint8_t type;
+	uint16_t version;
+	uint16_t length;
+} sigheader_t;
+
+/**
+ * Generate the IV from the given sequence number.
+ */
+static bool generate_iv(private_tls_aead_t *this, uint64_t seq, chunk_t iv)
+{
+	if (iv.len < sizeof(uint64_t) ||
+		iv.len < this->iv.len)
+	{
+		return FALSE;
+	}
+	memset(iv.ptr, 0, iv.len);
+	htoun64(iv.ptr + iv.len - sizeof(uint64_t), seq);
+	memxor(iv.ptr + iv.len - this->iv.len, this->iv.ptr, this->iv.len);
+	return TRUE;
+}
+
+METHOD(tls_aead_t, encrypt, bool,
+	private_tls_aead_t *this, tls_version_t version, tls_content_type_t *type,
+	uint64_t seq, chunk_t *data)
+{
+	bio_writer_t *writer;
+	chunk_t assoc, encrypted, iv, padding, plain;
+	uint8_t icvlen;
+	sigheader_t hdr;
+
+	iv = chunk_alloca(this->aead->get_iv_size(this->aead));
+	if (!generate_iv(this, seq, iv))
+	{
+		return FALSE;
+	}
+
+	/* no padding for now */
+	padding = chunk_empty;
+	icvlen = this->aead->get_icv_size(this->aead);
+
+	writer = bio_writer_create(data->len + 1 + padding.len + icvlen);
+	writer->write_data(writer, *data);
+	writer->write_uint8(writer, *type);
+	writer->write_data(writer, padding);
+	writer->skip(writer, icvlen);
+	encrypted = writer->extract_buf(writer);
+	writer->destroy(writer);
+
+	plain = encrypted;
+	plain.len -= icvlen;
+
+	hdr.type = TLS_APPLICATION_DATA;
+	htoun16(&hdr.version, TLS_1_2);
+	htoun16(&hdr.length, encrypted.len);
+
+	assoc = chunk_from_thing(hdr);
+	if (!this->aead->encrypt(this->aead, plain, assoc, iv, NULL))
+	{
+		chunk_free(&encrypted);
+		return FALSE;
+	}
+	chunk_free(data);
+	*type = TLS_APPLICATION_DATA;
+	*data = encrypted;
+	return TRUE;
+}
+
+METHOD(tls_aead_t, decrypt, bool,
+	private_tls_aead_t *this, tls_version_t version, tls_content_type_t *type,
+	uint64_t seq, chunk_t *data)
+{
+	chunk_t assoc, iv;
+	uint8_t icvlen;
+	sigheader_t hdr;
+
+	iv = chunk_alloca(this->aead->get_iv_size(this->aead));
+	if (!generate_iv(this, seq, iv))
+	{
+		return FALSE;
+	}
+
+	icvlen = this->aead->get_icv_size(this->aead);
+	if (data->len < icvlen)
+	{
+		return FALSE;
+	}
+
+	hdr.type = TLS_APPLICATION_DATA;
+	htoun16(&hdr.version, TLS_1_2);
+	htoun16(&hdr.length, data->len);
+
+	assoc = chunk_from_thing(hdr);
+	if (!this->aead->decrypt(this->aead, *data, assoc, iv, NULL))
+	{
+		return FALSE;
+	}
+	data->len -= icvlen;
+
+	while (data->len && !data->ptr[data->len-1])
+	{	/* ignore any padding */
+		data->len--;
+	}
+	if (data->len < 1)
+	{
+		return FALSE;
+	}
+	*type = data->ptr[data->len-1];
+	data->len--;
+	return TRUE;
+}
+
+METHOD(tls_aead_t, get_mac_key_size, size_t,
+	private_tls_aead_t *this)
+{
+	return 0;
+}
+
+METHOD(tls_aead_t, get_encr_key_size, size_t,
+	private_tls_aead_t *this)
+{
+	/* our AEAD implementations add the salt length here, so subtract it */
+	return this->aead->get_key_size(this->aead) - this->salt;
+}
+
+METHOD(tls_aead_t, get_iv_size, size_t,
+	private_tls_aead_t *this)
+{
+	/* analogous to the change above, we add the salt length here */
+	return this->aead->get_iv_size(this->aead) + this->salt;
+}
+
+METHOD(tls_aead_t, set_keys, bool,
+	private_tls_aead_t *this, chunk_t mac, chunk_t encr, chunk_t iv)
+{
+	chunk_t key, salt;
+	bool success;
+
+	if (mac.len || iv.len < this->salt)
+	{
+		return FALSE;
+	}
+
+	/* we have to recombine the keys as our AEAD implementations expect the
+	 * salt as part of the key */
+	chunk_clear(&this->iv);
+	chunk_split(iv, "ma", this->salt, &salt, iv.len - this->salt, &this->iv);
+	key = chunk_cata("cc", encr, salt);
+	success = this->aead->set_key(this->aead, key);
+	memwipe(key.ptr, key.len);
+	return success;
+}
+
+METHOD(tls_aead_t, destroy, void,
+	private_tls_aead_t *this)
+{
+	this->aead->destroy(this->aead);
+	chunk_clear(&this->iv);
+	free(this);
+}
+
+/*
+ * Described in header
+ */
+tls_aead_t *tls_aead_create_seq(encryption_algorithm_t encr, size_t encr_size)
+{
+	private_tls_aead_t *this;
+	size_t salt;
+
+	switch (encr)
+	{
+		case ENCR_AES_GCM_ICV16:
+		case ENCR_CHACHA20_POLY1305:
+			salt = 4;
+			break;
+		case ENCR_AES_CCM_ICV8:
+		case ENCR_AES_CCM_ICV16:
+			salt = 3;
+			break;
+		default:
+			return NULL;
+	}
+
+	INIT(this,
+		.public = {
+			.encrypt = _encrypt,
+			.decrypt = _decrypt,
+			.get_mac_key_size = _get_mac_key_size,
+			.get_encr_key_size = _get_encr_key_size,
+			.get_iv_size = _get_iv_size,
+			.set_keys = _set_keys,
+			.destroy = _destroy,
+		},
+		.aead = lib->crypto->create_aead(lib->crypto, encr, encr_size, salt),
+		.salt = salt,
+	);
+
+	if (!this->aead)
+	{
+		free(this);
+		return NULL;
+	}
+
+	if (this->aead->get_block_size(this->aead) != 1)
+	{	/* TLS does not define any padding scheme for AEAD */
+		destroy(this);
+		return NULL;
+	}
+
+	return &this->public;
+}