/* IKEv2 - more cryptographic calculations
 *
 * Copyright (C) 2007 Michael Richardson <mcr@xelerance.com>
 * Copyright (C) 2008-2010 Paul Wouters <paul@xelerance.com>
 * Copyright (C) 2012 Avesh Agarwal <avagarwa@redhat.com>
 * Copyright (C) 2013-2014 Paul Wouters <paul@libreswan.org>
 * Copyright (C) 2013 D. Hugh Redelmeier <hugh@mimosa.com>
 * Copyright (C) 2017 Andrew Cagney
 * Copyright (C) 2017 Antony Antony <antony@phenome.org>
 *
 * 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 <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <libreswan.h>

#include "sysdep.h"
#include "constants.h"
#include "lswlog.h"
#include "libswan.h"

#include "defs.h"
#include "cookie.h"
#include "id.h"
#include "x509.h"
#include "certs.h"
#include "connections.h"        /* needs id.h */
#include "state.h"
#include "packet.h"
#include "crypto.h"
#include "demux.h"
#include "pluto_crypt.h"  /* for pluto_crypto_req & pluto_crypto_req_cont */
#include "ikev2.h"
#include "ikev2_prf.h"
#include "ike_alg.h"
#include "alg_info.h"
#include "kernel_alg.h"
#include "crypt_symkey.h"
#include "ikev2_prf.h"
#include "kernel.h"

void ikev2_derive_child_keys(struct state *st, enum original_role role)
{
	chunk_t ikeymat, rkeymat;
	/* ??? note assumption that AH and ESP cannot be combined */
	struct ipsec_proto_info *ipi =
		st->st_esp.present? &st->st_esp :
		st->st_ah.present? &st->st_ah :
		NULL;

	passert(ipi != NULL);	/* ESP or AH must be present */
	passert(st->st_esp.present != st->st_ah.present);	/* only one */

	/*
	 * Integrity seed (key).  AEAD, for instance has NULL (no)
	 * separate integrity.
	 */
	const struct integ_desc *integ = ipi->attrs.transattrs.ta_integ;
	size_t integ_key_size = (integ != NULL ? integ->integ_keymat_size : 0);
	/*
	 * If there is encryption, then ENCKEYLEN contains the
	 * required number of bits.
	 */
	size_t encrypt_key_size = BYTES_FOR_BITS(ipi->attrs.transattrs.enckeylen);
	/*
	 * Finally, some encryption algorithms such as AEAD and CTR
	 * require "salt" as part of the "starting variable".
	 */
	const struct encrypt_desc *encrypt = ipi->attrs.transattrs.ta_encrypt;
	size_t encrypt_salt_size = (encrypt != NULL ? encrypt->salt_size : 0);

	ipi->keymat_len = integ_key_size + encrypt_key_size + encrypt_salt_size;

	DBG(DBG_CONTROL,
	    DBG_log("integ=%s: .key_size=%zu encrypt=%s: .key_size=%zu .salt_size=%zu keymat_len=%" PRIu16,
		    integ != NULL ? integ->common.name : "N/A",
		    integ_key_size,
		    encrypt != NULL ? encrypt->common.name : "N/A",
		    encrypt_key_size, encrypt_salt_size,
		    ipi->keymat_len));

	/*
	 *
	 * Keying material MUST be taken from the expanded KEYMAT in the
	 * following order:
	 *
	 *    All keys for SAs carrying data from the initiator to the responder
	 *    are taken before SAs going in the reverse direction.
	 *
	 *    If multiple IPsec protocols are negotiated, keying material is
	 *    taken in the order in which the protocol headers will appear in
	 *    the encapsulated packet.
	 *
	 *    If a single protocol has both encryption and authentication keys,
	 *    the encryption key is taken from the first octets of KEYMAT and
	 *    the authentication key is taken from the next octets.
	 *
	 *    For AES GCM (RFC 4106 Section 8,1) we need to add 4 bytes for
	 *    salt (AES_GCM_SALT_BYTES)
	 */
	chunk_t ni;
	chunk_t nr;
	setchunk(ni, st->st_ni.ptr, st->st_ni.len);
	setchunk(nr, st->st_nr.ptr, st->st_nr.len);
	PK11SymKey *shared = NULL;

	if (st->st_pfs_group != NULL) {
		DBG(DBG_CRYPT, DBG_log("#%lu %s add g^ir to child key %p",
					st->st_serialno,
					st->st_state_name,
					st->st_shared_nss));
		shared = st->st_shared_nss;
	}

	PK11SymKey *keymat = ikev2_child_sa_keymat(st->st_oakley.ta_prf,
						   st->st_skey_d_nss,
						   shared, ni, nr,
						   ipi->keymat_len * 2);
	PK11SymKey *ikey = key_from_symkey_bytes(keymat, 0, ipi->keymat_len);
	ikeymat = chunk_from_symkey("initiator keys", DBG_CRYPT, ikey);
	release_symkey(__func__, "ikey", &ikey);

	PK11SymKey *rkey = key_from_symkey_bytes(keymat, ipi->keymat_len,
						 ipi->keymat_len);
	rkeymat = chunk_from_symkey("responder keys:", DBG_CRYPT, rkey);
	release_symkey(__func__, "rkey", &rkey);

	release_symkey(__func__, "keymat", &keymat);

	if (role != ORIGINAL_INITIATOR) {
		DBG(DBG_PRIVATE, {
			    DBG_dump_chunk("our  keymat", ikeymat);
			    DBG_dump_chunk("peer keymat", rkeymat);
		    });
		ipi->our_keymat = ikeymat.ptr;
		ipi->peer_keymat = rkeymat.ptr;
	} else {
		DBG(DBG_PRIVATE, {
			    DBG_dump_chunk("our  keymat", rkeymat);
			    DBG_dump_chunk("peer keymat", ikeymat);
		    });
		ipi->peer_keymat = ikeymat.ptr;
		ipi->our_keymat = rkeymat.ptr;
	}

}
