/*	$NetBSD: xform_tcp.c,v 1.25 2022/05/22 11:39:08 riastradh Exp $ */
/*	$FreeBSD: xform_tcp.c,v 1.1.2.1 2004/02/14 22:24:09 bms Exp $ */

/*
 * Copyright (c) 2003 Bruce M. Simpson <bms@spc.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * TCP MD5 Signature Option (RFC2385). Dummy code, everything is handled
 * in TCP directly.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: xform_tcp.c,v 1.25 2022/05/22 11:39:08 riastradh Exp $");

#if defined(_KERNEL_OPT)
#include "opt_inet.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/kernel.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#ifdef TCP_SIGNATURE
#include <netinet/tcp_timer.h>
#include <netinet/tcp.h>
#include <netinet/tcp_var.h>
#endif

#include <netipsec/ipsec.h>
#include <netipsec/xform.h>

#include <netipsec/key.h>
#include <netipsec/key_debug.h>

/*
 * Initialize a TCP-MD5 SA. Called when the SA is being set up.
 *
 * We don't need to set up the tdb prefixed fields, as we don't use the
 * opencrypto code; we just perform a key length check.
 *
 * XXX: Currently we only allow a single 'magic' SPI to be used.
 *
 * This allows per-host granularity without affecting the userland
 * interface, which is a simple socket option toggle switch,
 * TCP_SIGNATURE_ENABLE.
 *
 * To allow per-service granularity requires that we have a means
 * of mapping port to SPI. The mandated way of doing this is to
 * use SPD entries to specify packet flows which get the TCP-MD5
 * treatment, however the code to do this is currently unstable
 * and unsuitable for production use.
 *
 * Therefore we use this compromise in the meantime.
 */
static int
tcpsignature_init(struct secasvar *sav, const struct xformsw *xsp)
{
	int keylen;

	if (sav->spi != htonl(TCP_SIG_SPI)) {
		DPRINTF("SPI %x must be TCP_SIG_SPI (0x1000)\n", sav->alg_auth);
		return EINVAL;
	}
	if (sav->alg_auth != SADB_X_AALG_TCP_MD5) {
		DPRINTF("unsupported authentication algorithm %u\n",
		    sav->alg_auth);
		return EINVAL;
	}
	if (sav->key_auth == NULL) {
		DPRINTF("no authentication key present\n");
		return EINVAL;
	}
	keylen = _KEYLEN(sav->key_auth);
	if ((keylen < TCP_KEYLEN_MIN) || (keylen > TCP_KEYLEN_MAX)) {
		DPRINTF("invalid key length %u\n", keylen);
		return EINVAL;
	}

	return 0;
}

static void
tcpsignature_zeroize(struct secasvar *sav)
{
	if (sav->key_auth) {
		explicit_memset(_KEYBUF(sav->key_auth), 0,
		    _KEYLEN(sav->key_auth));
	}

	sav->tdb_cryptoid = 0;
	sav->tdb_authalgxform = NULL;
	sav->tdb_xform = NULL;
}

static int
tcpsignature_input(struct mbuf *m, struct secasvar *sav, int skip,
    int protoff)
{
	panic("%s: should not have been called", __func__);
}

static int
tcpsignature_output(struct mbuf *m, const struct ipsecrequest *isr,
    struct secasvar *sav, int skip, int protoff, int flags)
{
	panic("%s: should not have been called", __func__);
}

static struct xformsw tcpsignature_xformsw = {
	.xf_type	= XF_TCPSIGNATURE,
	.xf_flags	= XFT_AUTH,
	.xf_name	= "TCPMD5",
	.xf_init	= tcpsignature_init,
	.xf_zeroize	= tcpsignature_zeroize,
	.xf_input	= tcpsignature_input,
	.xf_output	= tcpsignature_output,
	.xf_next	= NULL,
};

void
tcpsignature_attach(void)
{
	xform_register(&tcpsignature_xformsw);
}