xref: /src/sys/netipsec/xform_esp.c

/*	$NetBSD: xform_esp.c,v 1.107 2024/07/05 04:31:54 rin Exp $	*/
/*	$FreeBSD: xform_esp.c,v 1.2.2.1 2003/01/24 05:11:36 sam Exp $	*/
/*	$OpenBSD: ip_esp.c,v 1.69 2001/06/26 06:18:59 angelos Exp $ */

/*
 * The authors of this code are John Ioannidis (ji (at) tla.org),
 * Angelos D. Keromytis (kermit (at) csd.uch.gr) and
 * Niels Provos (provos (at) physnet.uni-hamburg.de).
 *
 * The original version of this code was written by John Ioannidis
 * for BSD/OS in Athens, Greece, in November 1995.
 *
 * Ported to OpenBSD and NetBSD, with additional transforms, in December 1996,
 * by Angelos D. Keromytis.
 *
 * Additional transforms and features in 1997 and 1998 by Angelos D. Keromytis
 * and Niels Provos.
 *
 * Additional features in 1999 by Angelos D. Keromytis.
 *
 * Copyright (C) 1995, 1996, 1997, 1998, 1999 by John Ioannidis,
 * Angelos D. Keromytis and Niels Provos.
 * Copyright (c) 2001 Angelos D. Keromytis.
 *
 * Permission to use, copy, and modify this software with or without fee
 * is hereby granted, provided that this entire notice is included in
 * all copies of any software which is or includes a copy or
 * modification of this software.
 * You may use this code under the GNU public license if you so wish. Please
 * contribute changes back to the authors under this freer than GPL license
 * so that we may further the use of strong encryption without limitations to
 * all.
 *
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
 * MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
 * PURPOSE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: xform_esp.c,v 1.107 2024/07/05 04:31:54 rin Exp $");

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

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/syslog.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/cprng.h>
#include <sys/pool.h>
#include <sys/pserialize.h>

#include <net/if.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_ecn.h>
#include <netinet/ip6.h>

#include <net/route.h>
#include <netipsec/ipsec.h>
#include <netipsec/ipsec_private.h>
#include <netipsec/ah.h>
#include <netipsec/ah_var.h>
#include <netipsec/esp.h>
#include <netipsec/esp_var.h>
#include <netipsec/xform.h>

#ifdef INET6
#include <netinet6/ip6_var.h>
#include <netipsec/ipsec6.h>
#endif

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

#include <opencrypto/cryptodev.h>

percpu_t *espstat_percpu;

int esp_enable = 1;

static int esp_max_ivlen;		/* max iv length over all algorithms */

static void esp_input_cb(struct cryptop *op);
static void esp_output_cb(struct cryptop *crp);

const uint8_t esp_stats[256] = { SADB_EALG_STATS_INIT };

static pool_cache_t esp_tdb_crypto_pool_cache;
static size_t esp_pool_item_size;

/*
 * NB: this is public for use by the PF_KEY support.
 * NB: if you add support here; be sure to add code to esp_attach below!
 */
const struct enc_xform *
esp_algorithm_lookup(int alg)
{

	switch (alg) {
	case SADB_EALG_DESCBC:
		return &enc_xform_des;
	case SADB_EALG_3DESCBC:
		return &enc_xform_3des;
	case SADB_X_EALG_AES:
		return &enc_xform_aes;
	case SADB_X_EALG_BLOWFISHCBC:
		return &enc_xform_blf;
	case SADB_X_EALG_CAST128CBC:
		return &enc_xform_cast5;
	case SADB_X_EALG_SKIPJACK:
		return &enc_xform_skipjack;
	case SADB_X_EALG_CAMELLIACBC:
		return &enc_xform_camellia;
	case SADB_X_EALG_AESCTR:
		return &enc_xform_aes_ctr;
	case SADB_X_EALG_AESGCM16:
		return &enc_xform_aes_gcm;
	case SADB_X_EALG_AESGMAC:
		return &enc_xform_aes_gmac;
	case SADB_EALG_NULL:
		return &enc_xform_null;
	}
	return NULL;
}

size_t
esp_hdrsiz(const struct secasvar *sav)
{
	size_t size;

	if (sav != NULL) {
		/*XXX not right for null algorithm--does it matter??*/
		KASSERT(sav->tdb_encalgxform != NULL);

		/*
		 *   base header size
		 * + iv length for CBC mode
		 * + max pad length
		 * + sizeof(esp trailer)
		 * + icv length (if any).
		 */
		if (sav->flags & SADB_X_EXT_OLD)
			size = sizeof(struct esp);
		else
			size = sizeof(struct newesp);
		size += sav->tdb_encalgxform->ivsize + 9 +
		    sizeof(struct esptail);

		/*XXX need alg check???*/
		if (sav->tdb_authalgxform != NULL && sav->replay)
			size += ah_authsiz(sav);
	} else {
		/*
		 *   base header size
		 * + max iv length for CBC mode
		 * + max pad length
		 * + sizeof(esp trailer)
		 * + max icv supported.
		 */
		size = sizeof(struct newesp) + esp_max_ivlen + 9 +
		    sizeof(struct esptail) + ah_authsiz(NULL);
	}
	return size;
}

/*
 * esp_init() is called when an SPI is being set up.
 */
static int
esp_init(struct secasvar *sav, const struct xformsw *xsp)
{
	const struct enc_xform *txform;
	struct cryptoini cria, crie, *cr;
	int keylen;
	int error;

	txform = esp_algorithm_lookup(sav->alg_enc);
	if (txform == NULL) {
		DPRINTF("unsupported encryption algorithm %d\n",
		    sav->alg_enc);
		return EINVAL;
	}
	if (sav->key_enc == NULL) {
		DPRINTF("no encoding key for %s algorithm\n",
		    txform->name);
		return EINVAL;
	}
	if ((sav->flags&(SADB_X_EXT_OLD|SADB_X_EXT_IV4B)) == SADB_X_EXT_IV4B) {
		DPRINTF("4-byte IV not supported with protocol\n");
		return EINVAL;
	}
	keylen = _KEYLEN(sav->key_enc);
	if (txform->minkey > keylen || keylen > txform->maxkey) {
		DPRINTF("invalid key length %u, must be in "
		    "the range [%u..%u] for algorithm %s\n",
		    keylen, txform->minkey, txform->maxkey, txform->name);
		return EINVAL;
	}

	sav->ivlen = txform->ivsize;

	/*
	 * Setup AH-related state.
	 */
	if (sav->alg_auth != 0) {
		error = ah_init0(sav, xsp, &cria);
		if (error)
			return error;
	}

	/* NB: override anything set in ah_init0 */
	sav->tdb_xform = xsp;
	sav->tdb_encalgxform = txform;

	switch (sav->alg_enc) {
	case SADB_X_EALG_AESGCM16:
	case SADB_X_EALG_AESGMAC:
		switch (keylen) {
		case 20:
			sav->alg_auth = SADB_X_AALG_AES128GMAC;
			sav->tdb_authalgxform = &auth_hash_gmac_aes_128;
			break;
		case 28:
			sav->alg_auth = SADB_X_AALG_AES192GMAC;
			sav->tdb_authalgxform = &auth_hash_gmac_aes_192;
			break;
		case 36:
			sav->alg_auth = SADB_X_AALG_AES256GMAC;
			sav->tdb_authalgxform = &auth_hash_gmac_aes_256;
			break;
		default:
			DPRINTF("invalid key length %u, must be either of "
			    "20, 28 or 36\n", keylen);
			return EINVAL;
		}

		memset(&cria, 0, sizeof(cria));
		cria.cri_alg = sav->tdb_authalgxform->type;
		cria.cri_klen = _KEYBITS(sav->key_enc);
		cria.cri_key = _KEYBUF(sav->key_enc);
		break;
	default:
		break;
	}

	/* Initialize crypto session. */
	memset(&crie, 0, sizeof(crie));
	crie.cri_alg = sav->tdb_encalgxform->type;
	crie.cri_klen = _KEYBITS(sav->key_enc);
	crie.cri_key = _KEYBUF(sav->key_enc);
	/* XXX Rounds ? */

	if (sav->tdb_authalgxform && sav->tdb_encalgxform) {
		/* init both auth & enc */
		crie.cri_next = &cria;
		cr = &crie;
	} else if (sav->tdb_encalgxform) {
		cr = &crie;
	} else if (sav->tdb_authalgxform) {
		cr = &cria;
	} else {
		/* XXX cannot happen? */
		DPRINTF("no encoding OR authentication xform!\n");
		return EINVAL;
	}

	return crypto_newsession(&sav->tdb_cryptoid, cr, crypto_support);
}

/*
 * Paranoia.
 */
static void
esp_zeroize(struct secasvar *sav)
{
	/* NB: ah_zerorize free's the crypto session state */
	ah_zeroize(sav);

	if (sav->key_enc) {
		explicit_memset(_KEYBUF(sav->key_enc), 0,
		    _KEYLEN(sav->key_enc));
	}
	sav->tdb_encalgxform = NULL;
	sav->tdb_xform = NULL;
}

/*
 * ESP input processing, called (eventually) through the protocol switch.
 */
static int
esp_input(struct mbuf *m, struct secasvar *sav, int skip, int protoff)
{
	const struct auth_hash *esph;
	const struct enc_xform *espx;
	struct tdb_crypto *tc;
	int plen, alen, hlen, error, stat = ESP_STAT_CRYPTO;
	struct newesp *esp;
	struct cryptodesc *crde;
	struct cryptop *crp;

	KASSERT(sav != NULL);
	KASSERT(sav->tdb_encalgxform != NULL);
	if (__predict_false((skip & 3) != 0 || (m->m_pkthdr.len & 3) != 0)) {
		DPRINTF("%s: misaligned packet, skip %u pkt len %u", __func__,
		    skip, m->m_pkthdr.len);
		stat = ESP_STAT_BADILEN; /* Same as FreeBSD */
		error = EINVAL;
		goto out;
	}

	/* XXX don't pullup, just copy header */
	M_REGION_GET(esp, struct newesp *, m, skip, sizeof(struct newesp));
	if (esp == NULL) {
		/* m already freed */
		return ENOBUFS;
	}

	esph = sav->tdb_authalgxform;
	espx = sav->tdb_encalgxform;
	KASSERT(espx != NULL);

	/* Determine the ESP header length */
	if (sav->flags & SADB_X_EXT_OLD)
		hlen = sizeof(struct esp) + sav->ivlen;
	else
		hlen = sizeof(struct newesp) + sav->ivlen;
	/* Authenticator hash size */
	alen = esph ? esph->authsize : 0;

	/*
	 * Verify payload length is multiple of encryption algorithm block
	 * size.
	 *
	 * The payload must also be 4-byte-aligned. This is implicitly
	 * verified here too, since the blocksize is always 4-byte-aligned.
	 */
	plen = m->m_pkthdr.len - (skip + hlen + alen);
	KASSERT((espx->blocksize & 3) == 0);
	if ((plen & (espx->blocksize - 1)) || (plen <= 0)) {
		char buf[IPSEC_ADDRSTRLEN];
		DPRINTF("payload of %d octets not a multiple of %d octets,"
		    "  SA %s/%08lx\n", plen, espx->blocksize,
		    ipsec_address(&sav->sah->saidx.dst, buf, sizeof(buf)),
		    (u_long) ntohl(sav->spi));
		stat = ESP_STAT_BADILEN;
		error = EINVAL;
		goto out;
	}

	/*
	 * Check sequence number.
	 */
	if (esph && sav->replay && !ipsec_chkreplay(ntohl(esp->esp_seq), sav)) {
		char logbuf[IPSEC_LOGSASTRLEN];
		DPRINTF("packet replay check for %s\n",
		    ipsec_logsastr(sav, logbuf, sizeof(logbuf)));
		stat = ESP_STAT_REPLAY;
		error = EACCES;
		goto out;
	}

	/* Update the counters */
	ESP_STATADD(ESP_STAT_IBYTES, plen);

	/* Get crypto descriptors */
	crp = crypto_getreq(esph ? 2 : 1);
	if (crp == NULL) {
		DPRINTF("failed to acquire crypto descriptors\n");
		error = ENOBUFS;
		goto out;
	}

	/* Get IPsec-specific opaque pointer */
	size_t extra __diagused = esph == NULL ? 0 : alen;
	KASSERTMSG(sizeof(*tc) + extra <= esp_pool_item_size,
	    "sizeof(*tc) + extra=%zu > esp_pool_item_size=%zu\n",
	    sizeof(*tc) + extra, esp_pool_item_size);
	tc = pool_cache_get(esp_tdb_crypto_pool_cache, PR_NOWAIT);
	if (tc == NULL) {
		DPRINTF("failed to allocate tdb_crypto\n");
		error = ENOBUFS;
		goto out1;
	}

	error = m_makewritable(&m, 0, m->m_pkthdr.len, M_NOWAIT);
	if (error) {
		DPRINTF("m_makewritable failed\n");
		goto out2;
	}

	if (esph) {
		struct cryptodesc *crda;

		KASSERT(crp->crp_desc != NULL);
		crda = crp->crp_desc;

		/* Authentication descriptor */
		crda->crd_skip = skip;
		if (espx->type == CRYPTO_AES_GCM_16)
			crda->crd_len = hlen - sav->ivlen;
		else
			crda->crd_len = m->m_pkthdr.len - (skip + alen);
		crda->crd_inject = m->m_pkthdr.len - alen;

		crda->crd_alg = esph->type;
		if (espx->type == CRYPTO_AES_GCM_16 ||
		    espx->type == CRYPTO_AES_GMAC) {
			crda->crd_key = _KEYBUF(sav->key_enc);
			crda->crd_klen = _KEYBITS(sav->key_enc);
		} else {
			crda->crd_key = _KEYBUF(sav->key_auth);
			crda->crd_klen = _KEYBITS(sav->key_auth);
		}

		/* Copy the authenticator */
		m_copydata(m, m->m_pkthdr.len - alen, alen, (tc + 1));

		/* Chain authentication request */
		crde = crda->crd_next;
	} else {
		crde = crp->crp_desc;
	}

    {
	int s = pserialize_read_enter();

	/*
	 * Take another reference to the SA for opencrypto callback.
	 */
	if (__predict_false(sav->state == SADB_SASTATE_DEAD)) {
		pserialize_read_exit(s);
		stat = ESP_STAT_NOTDB;
		error = ENOENT;
		goto out2;
	}
	KEY_SA_REF(sav);
	pserialize_read_exit(s);
    }

	/* Crypto operation descriptor */
	crp->crp_ilen = m->m_pkthdr.len; /* Total input length */
	crp->crp_flags = CRYPTO_F_IMBUF;
	crp->crp_buf = m;
	crp->crp_callback = esp_input_cb;
	crp->crp_sid = sav->tdb_cryptoid;
	crp->crp_opaque = tc;

	/* These are passed as-is to the callback */
	tc->tc_spi = sav->spi;
	tc->tc_dst = sav->sah->saidx.dst;
	tc->tc_proto = sav->sah->saidx.proto;
	tc->tc_protoff = protoff;
	tc->tc_skip = skip;
	tc->tc_sav = sav;

	/* Decryption descriptor */
	KASSERTMSG(crde != NULL, "null esp crypto descriptor");
	crde->crd_skip = skip + hlen;
	if (espx->type == CRYPTO_AES_GMAC)
		crde->crd_len = 0;
	else
		crde->crd_len = m->m_pkthdr.len - (skip + hlen + alen);
	crde->crd_inject = skip + hlen - sav->ivlen;
	crde->crd_alg = espx->type;
	crde->crd_key = _KEYBUF(sav->key_enc);
	crde->crd_klen = _KEYBITS(sav->key_enc);
	/* XXX Rounds ? */

	crypto_dispatch(crp);
	return 0;

out2:
	pool_cache_put(esp_tdb_crypto_pool_cache, tc);
out1:
	crypto_freereq(crp);
out:
	ESP_STATINC(stat);
	m_freem(m);
	return error;
}

#ifdef INET6
#define	IPSEC_COMMON_INPUT_CB(m, sav, skip, protoff) do {		\
	if (saidx->dst.sa.sa_family == AF_INET6) {			\
		(void)ipsec6_common_input_cb(m, sav, skip, protoff);	\
	} else {							\
		(void)ipsec4_common_input_cb(m, sav, skip, protoff);	\
	}								\
} while (0)
#else
#define	IPSEC_COMMON_INPUT_CB(m, sav, skip, protoff)			\
	((void)ipsec4_common_input_cb(m, sav, skip, protoff))
#endif

/*
 * ESP input callback from the crypto driver.
 */
static void
esp_input_cb(struct cryptop *crp)
{
	char buf[IPSEC_ADDRSTRLEN];
	uint8_t lastthree[3], aalg[AH_ALEN_MAX];
	int hlen, skip, protoff;
	struct mbuf *m;
	const struct auth_hash *esph;
	struct tdb_crypto *tc;
	struct secasvar *sav;
	struct secasindex *saidx;
	void *ptr;
	IPSEC_DECLARE_LOCK_VARIABLE;

	KASSERT(crp->crp_desc != NULL);
	KASSERT(crp->crp_opaque != NULL);

	tc = crp->crp_opaque;
	skip = tc->tc_skip;
	protoff = tc->tc_protoff;
	m = crp->crp_buf;

	IPSEC_ACQUIRE_GLOBAL_LOCKS();

	sav = tc->tc_sav;
	saidx = &sav->sah->saidx;
	KASSERTMSG(saidx->dst.sa.sa_family == AF_INET ||
	    saidx->dst.sa.sa_family == AF_INET6,
	    "unexpected protocol family %u", saidx->dst.sa.sa_family);

	esph = sav->tdb_authalgxform;

	/* Check for crypto errors */
	if (crp->crp_etype) {
		/* Reset the session ID */
		if (sav->tdb_cryptoid != 0)
			sav->tdb_cryptoid = crp->crp_sid;

		ESP_STATINC(ESP_STAT_NOXFORM);
		DPRINTF("crypto error %d\n", crp->crp_etype);
		goto bad;
	}

	ESP_STATINC(ESP_STAT_HIST + esp_stats[sav->alg_enc]);

	/* If authentication was performed, check now. */
	if (esph != NULL) {
		/*
		 * If we have a tag, it means an IPsec-aware NIC did
		 * the verification for us.  Otherwise we need to
		 * check the authentication calculation.
		 */
		AH_STATINC(AH_STAT_HIST + ah_stats[sav->alg_auth]);
		/* Copy the authenticator from the packet */
		m_copydata(m, m->m_pkthdr.len - esph->authsize,
			esph->authsize, aalg);

		ptr = (tc + 1);

		/* Verify authenticator */
		if (!consttime_memequal(ptr, aalg, esph->authsize)) {
			DPRINTF("authentication hash mismatch "
			    "for packet in SA %s/%08lx\n",
			    ipsec_address(&saidx->dst, buf,
			    sizeof(buf)), (u_long) ntohl(sav->spi));
			ESP_STATINC(ESP_STAT_BADAUTH);
			goto bad;
		}

		/* Remove trailing authenticator */
		m_adj(m, -(esph->authsize));
	}

	/* Release the crypto descriptors */
	pool_cache_put(esp_tdb_crypto_pool_cache, tc);
	tc = NULL;
	crypto_freereq(crp);
	crp = NULL;

	/*
	 * Packet is now decrypted.
	 */
	m->m_flags |= M_DECRYPTED;

	/*
	 * Update replay sequence number, if appropriate.
	 */
	if (sav->replay) {
		uint32_t seq;

		m_copydata(m, skip + offsetof(struct newesp, esp_seq),
		    sizeof(seq), &seq);
		if (ipsec_updatereplay(ntohl(seq), sav)) {
			char logbuf[IPSEC_LOGSASTRLEN];
			DPRINTF("packet replay check for %s\n",
			    ipsec_logsastr(sav, logbuf, sizeof(logbuf)));
			ESP_STATINC(ESP_STAT_REPLAY);
			goto bad;
		}
	}

	/* Determine the ESP header length */
	if (sav->flags & SADB_X_EXT_OLD)
		hlen = sizeof(struct esp) + sav->ivlen;
	else
		hlen = sizeof(struct newesp) + sav->ivlen;

	/* Remove the ESP header and IV from the mbuf. */
	if (m_striphdr(m, skip, hlen) != 0) {
		ESP_STATINC(ESP_STAT_HDROPS);
		DPRINTF("bad mbuf chain, SA %s/%08lx\n",
		    ipsec_address(&sav->sah->saidx.dst, buf, sizeof(buf)),
		    (u_long) ntohl(sav->spi));
		goto bad;
	}

	/* Save the last three bytes of decrypted data */
	m_copydata(m, m->m_pkthdr.len - 3, 3, lastthree);

	/* Verify pad length */
	if (lastthree[1] + 2 > m->m_pkthdr.len - skip) {
		ESP_STATINC(ESP_STAT_BADILEN);
		DPRINTF("invalid padding length %d "
		    "for %u byte packet in SA %s/%08lx\n",
		    lastthree[1], m->m_pkthdr.len - skip,
		    ipsec_address(&sav->sah->saidx.dst, buf, sizeof(buf)),
		    (u_long) ntohl(sav->spi));
		goto bad;
	}

	/* Verify correct decryption by checking the last padding bytes */
	if ((sav->flags & SADB_X_EXT_PMASK) != SADB_X_EXT_PRAND) {
		if (lastthree[1] != lastthree[0] && lastthree[1] != 0) {
			ESP_STATINC(ESP_STAT_BADENC);
			DPRINTF("decryption failed for packet in SA "
			    "%s/%08lx\n",
			    ipsec_address(&sav->sah->saidx.dst, buf,
			    sizeof(buf)), (u_long) ntohl(sav->spi));
			DPRINTF("%x %x\n", lastthree[0],
			    lastthree[1]);
			goto bad;
		}
	}

	/* Trim the mbuf chain to remove trailing authenticator and padding */
	m_adj(m, -(lastthree[1] + 2));

	/* Restore the Next Protocol field */
	m_copyback(m, protoff, sizeof(uint8_t), lastthree + 2);

	IPSEC_COMMON_INPUT_CB(m, sav, skip, protoff);

	KEY_SA_UNREF(&sav);
	IPSEC_RELEASE_GLOBAL_LOCKS();
	return;
bad:
	if (sav)
		KEY_SA_UNREF(&sav);
	IPSEC_RELEASE_GLOBAL_LOCKS();
	m_freem(m);
	if (tc != NULL)
		pool_cache_put(esp_tdb_crypto_pool_cache, tc);
	if (crp != NULL)
		crypto_freereq(crp);
}

/*
 * ESP output routine, called by ipsec[46]_process_packet().
 */
static int
esp_output(struct mbuf *m, const struct ipsecrequest *isr, struct secasvar *sav,
    int skip, int protoff, int flags)
{
	char buf[IPSEC_ADDRSTRLEN];
	const struct enc_xform *espx;
	const struct auth_hash *esph;
	int hlen, rlen, tlen, padlen, blks, alen, i, roff;
	struct mbuf *mo = NULL;
	struct tdb_crypto *tc;
	struct secasindex *saidx;
	unsigned char *tail;
	uint8_t prot;
	int error, maxpacketsize;
	struct esptail *esptail;
	struct cryptodesc *crde, *crda;
	struct cryptop *crp;

	esph = sav->tdb_authalgxform;
	espx = sav->tdb_encalgxform;
	KASSERT(espx != NULL);

	/* Determine the ESP header length */
	if (sav->flags & SADB_X_EXT_OLD)
		hlen = sizeof(struct esp) + sav->ivlen;
	else
		hlen = sizeof(struct newesp) + sav->ivlen;
	/* Authenticator hash size */
	alen = esph ? esph->authsize : 0;

	/*
	 * NB: The null encoding transform has a blocksize of 4
	 *     so that headers are properly aligned.
	 */
	blks = espx->blocksize;		/* IV blocksize */

	/* Raw payload length. */
	rlen = m->m_pkthdr.len - skip;

	/* Encryption padding. */
	padlen = ((blks - ((rlen + sizeof(struct esptail)) % blks)) % blks);

	/* Length of what we append (tail). */
	tlen = padlen + sizeof(struct esptail) + alen;

	ESP_STATINC(ESP_STAT_OUTPUT);

	saidx = &sav->sah->saidx;
	/* Check for maximum packet size violations. */
	switch (saidx->dst.sa.sa_family) {
#ifdef INET
	case AF_INET:
		maxpacketsize = IP_MAXPACKET;
		break;
#endif
#ifdef INET6
	case AF_INET6:
		maxpacketsize = IPV6_MAXPACKET;
		break;
#endif
	default:
		DPRINTF("unknown/unsupported protocol family %d, "
		    "SA %s/%08lx\n", saidx->dst.sa.sa_family,
		    ipsec_address(&saidx->dst, buf, sizeof(buf)),
		    (u_long)ntohl(sav->spi));
		ESP_STATINC(ESP_STAT_NOPF);
		error = EPFNOSUPPORT;
		goto bad;
	}
	if (skip + hlen + rlen + tlen > maxpacketsize) {
		DPRINTF("packet in SA %s/%08lx got too big (len %u, "
		    "max len %u)\n",
		    ipsec_address(&saidx->dst, buf, sizeof(buf)),
		    (u_long) ntohl(sav->spi),
		    skip + hlen + rlen + tlen, maxpacketsize);
		ESP_STATINC(ESP_STAT_TOOBIG);
		error = EMSGSIZE;
		goto bad;
	}

	/* Update the counters. */
	ESP_STATADD(ESP_STAT_OBYTES, m->m_pkthdr.len - skip);

	m = m_clone(m);
	if (m == NULL) {
		DPRINTF("cannot clone mbuf chain, SA %s/%08lx\n",
		    ipsec_address(&saidx->dst, buf, sizeof(buf)),
		    (u_long) ntohl(sav->spi));
		ESP_STATINC(ESP_STAT_HDROPS);
		error = ENOBUFS;
		goto bad;
	}

	/* Inject ESP header. */
	mo = m_makespace(m, skip, hlen, &roff);
	if (mo == NULL) {
		DPRINTF("failed to inject %u byte ESP hdr for SA "
		    "%s/%08lx\n", hlen,
		    ipsec_address(&saidx->dst, buf, sizeof(buf)),
		    (u_long) ntohl(sav->spi));
		ESP_STATINC(ESP_STAT_HDROPS);
		error = ENOBUFS;
		goto bad;
	}

	/* Initialize ESP header. */
	memcpy(mtod(mo, char *) + roff, &sav->spi, sizeof(uint32_t));
	if (sav->replay) {
		uint32_t replay;

#ifdef IPSEC_DEBUG
		/* Emulate replay attack when ipsec_replay is TRUE. */
		if (ipsec_replay)
			replay = htonl(sav->replay->count);
		else
#endif
			replay = htonl(atomic_inc_32_nv(&sav->replay->count));

		memcpy(mtod(mo,char *) + roff + sizeof(uint32_t), &replay,
		    sizeof(uint32_t));
	}

	/*
	 * Grow the mbuf, we will append data at the tail.
	 */
	tail = m_pad(m, tlen);
	if (tail == NULL) {
		DPRINTF("m_pad failed for SA %s/%08lx\n",
		    ipsec_address(&saidx->dst, buf, sizeof(buf)),
		    (u_long) ntohl(sav->spi));
		m = NULL;
		error = ENOBUFS;
		goto bad;
	}

	/*
	 * Add padding: random, zero, or self-describing.
	 */
	switch (sav->flags & SADB_X_EXT_PMASK) {
	case SADB_X_EXT_PSEQ:
		for (i = 0; i < padlen; i++)
			tail[i] = i + 1;
		break;
	case SADB_X_EXT_PRAND:
		(void)cprng_fast(tail, padlen);
		break;
	case SADB_X_EXT_PZERO:
	default:
		memset(tail, 0, padlen);
		break;
	}

	/* Build the ESP Trailer. */
	esptail = (struct esptail *)&tail[padlen];
	esptail->esp_padlen = padlen;
	m_copydata(m, protoff, sizeof(uint8_t), &esptail->esp_nxt);

	/* Fix Next Protocol in IPv4/IPv6 header. */
	prot = IPPROTO_ESP;
	m_copyback(m, protoff, sizeof(uint8_t), &prot);

	/* Get crypto descriptors. */
	crp = crypto_getreq(esph ? 2 : 1);
	if (crp == NULL) {
		DPRINTF("failed to acquire crypto descriptors\n");
		ESP_STATINC(ESP_STAT_CRYPTO);
		error = ENOBUFS;
		goto bad;
	}

	/* Get the descriptors. */
	crde = crp->crp_desc;
	crda = crde->crd_next;

	/* Encryption descriptor. */
	crde->crd_skip = skip + hlen;
	if (espx->type == CRYPTO_AES_GMAC)
		crde->crd_len = 0;
	else
		crde->crd_len = m->m_pkthdr.len - (skip + hlen + alen);
	crde->crd_flags = CRD_F_ENCRYPT;
	crde->crd_inject = skip + hlen - sav->ivlen;
	crde->crd_alg = espx->type;
	crde->crd_key = _KEYBUF(sav->key_enc);
	crde->crd_klen = _KEYBITS(sav->key_enc);
	/* XXX Rounds ? */

	/* IPsec-specific opaque crypto info. */
	tc = pool_cache_get(esp_tdb_crypto_pool_cache, PR_NOWAIT);
	if (tc == NULL) {
		crypto_freereq(crp);
		DPRINTF("failed to allocate tdb_crypto\n");
		ESP_STATINC(ESP_STAT_CRYPTO);
		error = ENOBUFS;
		goto bad;
	}

    {
	int s = pserialize_read_enter();

	/*
	 * Take another reference to the SP and the SA for opencrypto callback.
	 */
	if (__predict_false(isr->sp->state == IPSEC_SPSTATE_DEAD ||
	    sav->state == SADB_SASTATE_DEAD)) {
		pserialize_read_exit(s);
		pool_cache_put(esp_tdb_crypto_pool_cache, tc);
		crypto_freereq(crp);
		ESP_STATINC(ESP_STAT_NOTDB);
		error = ENOENT;
		goto bad;
	}
	KEY_SP_REF(isr->sp);
	KEY_SA_REF(sav);
	pserialize_read_exit(s);
    }

	/* Callback parameters */
	tc->tc_isr = isr;
	tc->tc_spi = sav->spi;
	tc->tc_dst = saidx->dst;
	tc->tc_proto = saidx->proto;
	tc->tc_flags = flags;
	tc->tc_sav = sav;

	/* Crypto operation descriptor. */
	crp->crp_ilen = m->m_pkthdr.len; /* Total input length. */
	crp->crp_flags = CRYPTO_F_IMBUF;
	crp->crp_buf = m;
	crp->crp_callback = esp_output_cb;
	crp->crp_opaque = tc;
	crp->crp_sid = sav->tdb_cryptoid;

	if (esph) {
		/* Authentication descriptor. */
		crda->crd_skip = skip;
		if (espx->type == CRYPTO_AES_GCM_16)
			crda->crd_len = hlen - sav->ivlen;
		else
			crda->crd_len = m->m_pkthdr.len - (skip + alen);
		crda->crd_inject = m->m_pkthdr.len - alen;

		/* Authentication operation. */
		crda->crd_alg = esph->type;
		if (espx->type == CRYPTO_AES_GCM_16 ||
		    espx->type == CRYPTO_AES_GMAC) {
			crda->crd_key = _KEYBUF(sav->key_enc);
			crda->crd_klen = _KEYBITS(sav->key_enc);
		} else {
			crda->crd_key = _KEYBUF(sav->key_auth);
			crda->crd_klen = _KEYBITS(sav->key_auth);
		}
	}

	crypto_dispatch(crp);
	return 0;

bad:
	m_freem(m);
	return error;
}

/*
 * ESP output callback from the crypto driver.
 */
static void
esp_output_cb(struct cryptop *crp)
{
	struct tdb_crypto *tc;
	const struct ipsecrequest *isr;
	struct secasvar *sav;
	struct mbuf *m;
	int flags;
	IPSEC_DECLARE_LOCK_VARIABLE;

	KASSERT(crp->crp_opaque != NULL);
	tc = crp->crp_opaque;
	m = crp->crp_buf;

	IPSEC_ACQUIRE_GLOBAL_LOCKS();

	isr = tc->tc_isr;
	sav = tc->tc_sav;

	/* Check for crypto errors. */
	if (crp->crp_etype) {
		/* Reset session ID. */
		if (sav->tdb_cryptoid != 0)
			sav->tdb_cryptoid = crp->crp_sid;

		ESP_STATINC(ESP_STAT_NOXFORM);
		DPRINTF("crypto error %d\n", crp->crp_etype);
		goto bad;
	}

	ESP_STATINC(ESP_STAT_HIST + esp_stats[sav->alg_enc]);
	if (sav->tdb_authalgxform != NULL)
		AH_STATINC(AH_STAT_HIST + ah_stats[sav->alg_auth]);

	flags = tc->tc_flags;
	/* Release crypto descriptors. */
	pool_cache_put(esp_tdb_crypto_pool_cache, tc);
	crypto_freereq(crp);

#ifdef IPSEC_DEBUG
	/* Emulate man-in-the-middle attack when ipsec_integrity is TRUE. */
	if (ipsec_integrity) {
		static unsigned char ipseczeroes[AH_ALEN_MAX];
		const struct auth_hash *esph;

		/*
		 * Corrupt HMAC if we want to test integrity verification of
		 * the other side.
		 */
		esph = sav->tdb_authalgxform;
		if (esph !=  NULL) {
			m_copyback(m, m->m_pkthdr.len - esph->authsize,
			    esph->authsize, ipseczeroes);
		}
	}
#endif

	/* NB: m is reclaimed by ipsec_process_done. */
	(void)ipsec_process_done(m, isr, sav, flags);
	KEY_SA_UNREF(&sav);
	KEY_SP_UNREF(&isr->sp);
	IPSEC_RELEASE_GLOBAL_LOCKS();
	return;

bad:
	if (sav)
		KEY_SA_UNREF(&sav);
	KEY_SP_UNREF(&isr->sp);
	IPSEC_RELEASE_GLOBAL_LOCKS();
	m_freem(m);
	pool_cache_put(esp_tdb_crypto_pool_cache, tc);
	crypto_freereq(crp);
}

static struct xformsw esp_xformsw = {
	.xf_type	= XF_ESP,
	.xf_flags	= XFT_CONF|XFT_AUTH,
	.xf_name	= "IPsec ESP",
	.xf_init	= esp_init,
	.xf_zeroize	= esp_zeroize,
	.xf_input	= esp_input,
	.xf_output	= esp_output,
	.xf_next	= NULL,
};

void
esp_attach(void)
{

	espstat_percpu = percpu_alloc(sizeof(uint64_t) * ESP_NSTATS);

	extern int ah_max_authsize;
	KASSERT(ah_max_authsize != 0);
	esp_pool_item_size = sizeof(struct tdb_crypto) + ah_max_authsize;
	esp_tdb_crypto_pool_cache = pool_cache_init(esp_pool_item_size,
	    coherency_unit, 0, 0, "esp_tdb_crypto", NULL, IPL_SOFTNET,
	    NULL, NULL, NULL);

#define	MAXIV(xform)					\
	if (xform.ivsize > esp_max_ivlen)		\
		esp_max_ivlen = xform.ivsize		\

	esp_max_ivlen = 0;
	MAXIV(enc_xform_des);		/* SADB_EALG_DESCBC */
	MAXIV(enc_xform_3des);		/* SADB_EALG_3DESCBC */
	MAXIV(enc_xform_aes);		/* SADB_X_EALG_AES */
	MAXIV(enc_xform_blf);		/* SADB_X_EALG_BLOWFISHCBC */
	MAXIV(enc_xform_cast5);		/* SADB_X_EALG_CAST128CBC */
	MAXIV(enc_xform_skipjack);	/* SADB_X_EALG_SKIPJACK */
	MAXIV(enc_xform_camellia);	/* SADB_X_EALG_CAMELLIACBC */
	MAXIV(enc_xform_aes_ctr);	/* SADB_X_EALG_AESCTR */
	MAXIV(enc_xform_null);		/* SADB_EALG_NULL */

	xform_register(&esp_xformsw);
#undef MAXIV
}