text: /*	$FreeBSD: src/sys/netipsec/xform_esp.c,v 1.2.2.2 2003/02/26 00:14:05 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@tla.org),
   * Angelos D. Keromytis (kermit@csd.uch.gr) and
   * Niels Provos (provos@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 "opt_inet.h"
  #include "opt_inet6.h"
  
  #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/random.h>
  #include <sys/sysctl.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 <netproto/ipsec/ipsec.h>
  #include <netproto/ipsec/ah.h>
  #include <netproto/ipsec/ah_var.h>
  #include <netproto/ipsec/esp.h>
  #include <netproto/ipsec/esp_var.h>
  #include <netproto/ipsec/xform.h>
  
  #ifdef INET6
  #include <netinet6/ip6_var.h>
  #include <netproto/ipsec/ipsec6.h>
  #include <netinet6/ip6_ecn.h>
  #endif
  
  #include <netproto/ipsec/key.h>
  #include <netproto/ipsec/key_debug.h>
  
  #include <opencrypto/cryptodev.h>
  #include <opencrypto/xform.h>
  
  int	esp_enable = 1;
  struct	espstat espstat;
  
  SYSCTL_DECL(_net_inet_esp);
  SYSCTL_INT(_net_inet_esp, OID_AUTO,
  	esp_enable,	CTLFLAG_RW,	&esp_enable,	0, "");
  SYSCTL_STRUCT(_net_inet_esp, IPSECCTL_STATS,
  	stats,		CTLFLAG_RD,	&espstat,	espstat, "");
  
  static	int esp_max_ivlen;		/* max iv length over all algorithms */
  
  static int esp_input_cb(struct cryptop *op);
  static int esp_output_cb(struct cryptop *crp);
  
  /*
   * 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!
   */
  struct enc_xform *
  esp_algorithm_lookup(int alg)
  {
  	if (alg >= ESP_ALG_MAX)
  		return NULL;
  	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_rijndael128;
  	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_EALG_NULL:
  		return &enc_xform_null;
  	}
  	return NULL;
  }
  
  size_t
  esp_hdrsiz(struct secasvar *sav)
  {
  	size_t size;
  
  	if (sav != NULL) {
  		/*XXX not right for null algorithm--does it matter??*/
  		KASSERT(sav->tdb_encalgxform != NULL,
  			("esp_hdrsiz: SA with null xform"));
  		if (sav->flags & SADB_X_EXT_OLD)
  			size = sizeof (struct esp);
  		else
  			size = sizeof (struct newesp);
  		size += sav->tdb_encalgxform->blocksize + 9;
  		/*XXX need alg check???*/
  		if (sav->tdb_authalgxform != NULL && sav->replay)
  			size += ah_hdrsiz(sav);
  	} else {
  		/*
  		 *   base header size
  		 * + max iv length for CBC mode
  		 * + max pad length
  		 * + sizeof (pad length field)
  		 * + sizeof (next header field)
  		 * + max icv supported.
  		 */
  		size = sizeof (struct newesp) + esp_max_ivlen + 9 + 16;
  	}
  	return size;
  }
  
  /*
   * esp_init() is called when an SPI is being set up.
   */
  static int
  esp_init(struct secasvar *sav, struct xformsw *xsp)
  {
  	struct enc_xform *txform;
  	struct cryptoini cria, crie;
  	int keylen;
  	int error;
  
  	txform = esp_algorithm_lookup(sav->alg_enc);
  	if (txform == NULL) {
  		DPRINTF(("esp_init: unsupported encryption algorithm %d\n",
  			sav->alg_enc));
  		return EINVAL;
  	}
  	if (sav->key_enc == NULL) {
  		DPRINTF(("esp_init: 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(("esp_init: 4-byte IV not supported with protocol\n"));
  		return EINVAL;
  	}
  	keylen = _KEYLEN(sav->key_enc);
  	if (txform->minkey > keylen || keylen > txform->maxkey) {
  		DPRINTF(("esp_init: invalid key length %u, must be in "
  			"the range [%u..%u] for algorithm %s\n",
  			keylen, txform->minkey, txform->maxkey,
  			txform->name));
  		return EINVAL;
  	}
  
  	/*
  	 * NB: The null xform needs a non-zero blocksize to keep the
  	 *      crypto code happy but if we use it to set ivlen then
  	 *      the ESP header will be processed incorrectly.  The
  	 *      compromise is to force it to zero here.
  	 */
  	sav->ivlen = (txform == &enc_xform_null ? 0 : txform->blocksize);
  	sav->iv = (caddr_t) kmalloc(sav->ivlen, M_XDATA, M_WAITOK);
  	key_randomfill(sav->iv, sav->ivlen);	/*XXX*/
  
  	/*
  	 * 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;
  
  	/* Initialize crypto session. */
  	bzero(&crie, 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;
  		error = crypto_newsession(&sav->tdb_cryptoid,
  					  &crie, crypto_support);
  	} else if (sav->tdb_encalgxform) {
  		error = crypto_newsession(&sav->tdb_cryptoid,
  					  &crie, crypto_support);
  	} else if (sav->tdb_authalgxform) {
  		error = crypto_newsession(&sav->tdb_cryptoid,
  					  &cria, crypto_support);
  	} else {
  		/* XXX cannot happen? */
  		DPRINTF(("esp_init: no encoding OR authentication xform!\n"));
  		error = EINVAL;
  	}
  	return error;
  }
  
  /*
   * Paranoia.
   */
  static int
  esp_zeroize(struct secasvar *sav)
  {
  	/* NB: ah_zerorize free's the crypto session state */
  	int error = ah_zeroize(sav);
  
  	if (sav->key_enc)
  		bzero(_KEYBUF(sav->key_enc), _KEYLEN(sav->key_enc));
  	/* NB: sav->iv is freed elsewhere, even though we malloc it! */
  	sav->tdb_encalgxform = NULL;
  	sav->tdb_xform = NULL;
  	return error;
  }
  
  /*
   * ESP input processing, called (eventually) through the protocol switch.
   */
  static int
  esp_input(struct mbuf *m, struct secasvar *sav, int skip, int protoff)
  {
  	struct auth_hash *esph;
  	struct enc_xform *espx;
  	struct tdb_ident *tdbi;
  	struct tdb_crypto *tc;
  	int plen, alen, hlen;
  	struct m_tag *mtag;
  	struct newesp *esp;
  
  	struct cryptodesc *crde;
  	struct cryptop *crp;
  
  	KASSERT(sav != NULL, ("esp_input: null SA"));
  	KASSERT(sav->tdb_encalgxform != NULL,
  		("esp_input: null encoding xform"));
  	KASSERT((skip&3) == 0 && (m->m_pkthdr.len&3) == 0,
  		("esp_input: misaligned packet, skip %u pkt len %u",
  			skip, m->m_pkthdr.len));
  
  	/* XXX don't pullup, just copy header */
  	IP6_EXTHDR_GET(esp, struct newesp *, m, skip, sizeof (struct newesp));
  
  	esph = sav->tdb_authalgxform;
  	espx = sav->tdb_encalgxform;
  
  	/* 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 ? AH_HMAC_HASHLEN : 0;
  
  	/*
  	 * Verify payload length is multiple of encryption algorithm
  	 * block size.
  	 *
  	 * NB: This works for the null algorithm because the blocksize
  	 *     is 4 and all packets must be 4-byte aligned regardless
  	 *     of the algorithm.
  	 */
  	plen = m->m_pkthdr.len - (skip + hlen + alen);
  	if ((plen & (espx->blocksize - 1)) || (plen <= 0)) {
  		DPRINTF(("esp_input: "
  		    "payload of %d octets not a multiple of %d octets,"
  		    "  SA %s/%08lx\n",
  		    plen, espx->blocksize,
  		    ipsec_address(&sav->sah->saidx.dst),
  		    (u_long) ntohl(sav->spi)));
  		espstat.esps_badilen++;
  		m_freem(m);
  		return EINVAL;
  	}
  
  	/*
  	 * Check sequence number.
  	 */
  	if (esph && sav->replay && !ipsec_chkreplay(ntohl(esp->esp_seq), sav)) {
  		DPRINTF(("esp_input: packet replay check for %s\n",
  		    ipsec_logsastr(sav)));	/*XXX*/
  		espstat.esps_replay++;
  		m_freem(m);
  		return ENOBUFS;		/*XXX*/
  	}
  
  	/* Update the counters */
  	espstat.esps_ibytes += m->m_pkthdr.len - skip - hlen - alen;
  
  	/* Find out if we've already done crypto */
  	for (mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_CRYPTO_DONE, NULL);
  	     mtag != NULL;
  	     mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_CRYPTO_DONE, mtag)) {
  		tdbi = (struct tdb_ident *)m_tag_data(mtag);
  		if (tdbi->proto == sav->sah->saidx.proto &&
  		    tdbi->spi == sav->spi &&
  		    !bcmp(&tdbi->dst, &sav->sah->saidx.dst,
  			  sizeof(union sockaddr_union)))
  			break;
  	}
  
  	/* Get crypto descriptors */
  	crp = crypto_getreq(esph && espx ? 2 : 1);
  	if (crp == NULL) {
  		DPRINTF(("esp_input: failed to acquire crypto descriptors\n"));
  		espstat.esps_crypto++;
  		m_freem(m);
  		return ENOBUFS;
  	}
  
  	/* Get IPsec-specific opaque pointer */
  	if (esph == NULL || mtag != NULL)
  		tc = kmalloc(sizeof(struct tdb_crypto),
  			    M_XDATA, M_INTWAIT | M_ZERO | M_NULLOK);
  	else
  		tc = kmalloc(sizeof(struct tdb_crypto) + alen,
  			    M_XDATA, M_INTWAIT | M_ZERO | M_NULLOK);
  	if (tc == NULL) {
  		crypto_freereq(crp);
  		DPRINTF(("esp_input: failed to allocate tdb_crypto\n"));
  		espstat.esps_crypto++;
  		m_freem(m);
  		return ENOBUFS;
  	}
  
  	tc->tc_ptr = (caddr_t) mtag;
  
  	if (esph) {
  		struct cryptodesc *crda = crp->crp_desc;
  
  		KASSERT(crda != NULL, ("esp_input: null ah crypto descriptor"));
  
  		/* Authentication descriptor */
  		crda->crd_skip = skip;
  		crda->crd_len = m->m_pkthdr.len - (skip + alen);
  		crda->crd_inject = m->m_pkthdr.len - alen;
  
  		crda->crd_alg = esph->type;
  		crda->crd_key = _KEYBUF(sav->key_auth);
  		crda->crd_klen = _KEYBITS(sav->key_auth);
  
  		/* Copy the authenticator */
  		if (mtag == NULL)
  			m_copydata(m, m->m_pkthdr.len - alen, alen,
  				   (caddr_t) (tc + 1));
  
  		/* Chain authentication request */
  		crde = crda->crd_next;
  	} else {
  		crde = crp->crp_desc;
  	}
  
  	/* Crypto operation descriptor */
  	crp->crp_ilen = m->m_pkthdr.len; /* Total input length */
  	crp->crp_flags = CRYPTO_F_IMBUF;
  	crp->crp_buf = (caddr_t) m;
  	crp->crp_callback = esp_input_cb;
  	crp->crp_sid = sav->tdb_cryptoid;
  	crp->crp_opaque = (caddr_t) 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;
  
  	/* Decryption descriptor */
  	if (espx) {
  		KASSERT(crde != NULL, ("esp_input: null esp crypto descriptor"));
  		crde->crd_skip = skip + hlen;
  		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 ? */
  	}
  
  	if (mtag == NULL)
  		return crypto_dispatch(crp);
  	else
  		return esp_input_cb(crp);
  }
  
  #ifdef INET6
  #define	IPSEC_COMMON_INPUT_CB(m, sav, skip, protoff, mtag) do {		     \
  	if (saidx->dst.sa.sa_family == AF_INET6) {			     \
  		error = ipsec6_common_input_cb(m, sav, skip, protoff, mtag); \
  	} else {							     \
  		error = ipsec4_common_input_cb(m, sav, skip, protoff, mtag); \
  	}								     \
  } while (0)
  #else
  #define	IPSEC_COMMON_INPUT_CB(m, sav, skip, protoff, mtag)		     \
  	(error = ipsec4_common_input_cb(m, sav, skip, protoff, mtag))
  #endif
  
  /*
   * ESP input callback from the crypto driver.
   */
  static int
  esp_input_cb(struct cryptop *crp)
  {
  	u_int8_t lastthree[3], aalg[AH_HMAC_HASHLEN];
  	int hlen, skip, protoff, error;
  	struct mbuf *m;
  	struct cryptodesc *crd;
  	struct auth_hash *esph;
  	struct enc_xform *espx;
  	struct tdb_crypto *tc;
  	struct m_tag *mtag;
  	struct secasvar *sav;
  	struct secasindex *saidx;
  	caddr_t ptr;
  
  	crd = crp->crp_desc;
  	KASSERT(crd != NULL, ("esp_input_cb: null crypto descriptor!"));
  
  	tc = (struct tdb_crypto *) crp->crp_opaque;
  	KASSERT(tc != NULL, ("esp_input_cb: null opaque crypto data area!"));
  	skip = tc->tc_skip;
  	protoff = tc->tc_protoff;
  	mtag = (struct m_tag *) tc->tc_ptr;
  	m = (struct mbuf *) crp->crp_buf;
  
  	crit_enter();
  
  	sav = KEY_ALLOCSA(&tc->tc_dst, tc->tc_proto, tc->tc_spi);
  	if (sav == NULL) {
  		espstat.esps_notdb++;
  		DPRINTF(("esp_input_cb: SA expired while in crypto "
  		    "(SA %s/%08lx proto %u)\n", ipsec_address(&tc->tc_dst),
  		    (u_long) ntohl(tc->tc_spi), tc->tc_proto));
  		error = ENOBUFS;		/*XXX*/
  		goto bad;
  	}
  
  	saidx = &sav->sah->saidx;
  	KASSERT(saidx->dst.sa.sa_family == AF_INET ||
  		saidx->dst.sa.sa_family == AF_INET6,
  		("ah_input_cb: unexpected protocol family %u",
  		 saidx->dst.sa.sa_family));
  
  	esph = sav->tdb_authalgxform;
  	espx = sav->tdb_encalgxform;
  
  	/* Check for crypto errors */
  	if (crp->crp_etype) {
  		/* Reset the session ID */
  		if (sav->tdb_cryptoid != 0)
  			sav->tdb_cryptoid = crp->crp_sid;
  
  		if (crp->crp_etype == EAGAIN) {
  			KEY_FREESAV(&sav);
  			crit_exit();
  			return crypto_dispatch(crp);
  		}
  
  		espstat.esps_noxform++;
  		DPRINTF(("esp_input_cb: crypto error %d\n", crp->crp_etype));
  		error = crp->crp_etype;
  		goto bad;
  	}
  
  	/* Shouldn't happen... */
  	if (m == NULL) {
  		espstat.esps_crypto++;
  		DPRINTF(("esp_input_cb: bogus returned buffer from crypto\n"));
  		error = EINVAL;
  		goto bad;
  	}
  	espstat.esps_hist[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.
  		 */
  		ahstat.ahs_hist[sav->alg_auth]++;
  		if (mtag == NULL) {
  			/* Copy the authenticator from the packet */
  			m_copydata(m, m->m_pkthdr.len - esph->blocksize,
  				esph->blocksize, aalg);
  
  			ptr = (caddr_t) (tc + 1);
  
  			/* Verify authenticator */
  			if (bcmp(ptr, aalg, esph->blocksize) != 0) {
  				DPRINTF(("esp_input_cb: "
  		    "authentication hash mismatch for packet in SA %s/%08lx\n",
  				    ipsec_address(&saidx->dst),
  				    (u_long) ntohl(sav->spi)));
  				espstat.esps_badauth++;
  				error = EACCES;
  				goto bad;
  			}
  		}
  
  		/* Remove trailing authenticator */
  		m_adj(m, -(esph->blocksize));
  	}
  
  	/* Release the crypto descriptors */
  	kfree(tc, M_XDATA), 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) {
  		u_int32_t seq;
  
  		m_copydata(m, skip + offsetof(struct newesp, esp_seq),
  			   sizeof (seq), (caddr_t) &seq);
  		if (ipsec_updatereplay(ntohl(seq), sav)) {
  			DPRINTF(("%s: packet replay check for %s\n", __func__,
  			    ipsec_logsastr(sav)));
  			espstat.esps_replay++;
  			error = ENOBUFS;
  			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. */
  	error = m_striphdr(m, skip, hlen);
  	if (error) {
  		espstat.esps_hdrops++;
  		DPRINTF(("esp_input_cb: bad mbuf chain, SA %s/%08lx\n",
  		    ipsec_address(&sav->sah->saidx.dst),
  		    (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) {
  		espstat.esps_badilen++;
  		DPRINTF(("esp_input_cb: 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),
  			 (u_long) ntohl(sav->spi)));
  		error = EINVAL;
  		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) {
  			espstat.esps_badenc++;
  			DPRINTF(("esp_input_cb: decryption failed "
  				"for packet in SA %s/%08lx\n",
  				ipsec_address(&sav->sah->saidx.dst),
  				(u_long) ntohl(sav->spi)));
  DPRINTF(("esp_input_cb: %x %x\n", lastthree[0], lastthree[1]));
  			error = EINVAL;
  			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 (u_int8_t), lastthree + 2);
  
  	IPSEC_COMMON_INPUT_CB(m, sav, skip, protoff, mtag);
  
  	KEY_FREESAV(&sav);
  	crit_exit();
  	return error;
  bad:
  	if (sav)
  		KEY_FREESAV(&sav);
  	crit_exit();
  	if (m != NULL)
  		m_freem(m);
  	if (tc != NULL)
  		kfree(tc, M_XDATA);
  	if (crp != NULL)
  		crypto_freereq(crp);
  	return error;
  }
  
  /*
   * ESP output routine, called by ipsec[46]_process_packet().
   */
  static int
  esp_output(
  	struct mbuf *m,
  	struct ipsecrequest *isr,
  	struct mbuf **mp,
  	int skip,
  	int protoff
  )
  {
  	struct enc_xform *espx;
  	struct auth_hash *esph;
  	int hlen, rlen, plen, padding, blks, alen, i, roff;
  	struct mbuf *mo = NULL;
  	struct tdb_crypto *tc;
  	struct secasvar *sav;
  	struct secasindex *saidx;
  	unsigned char *pad;
  	u_int8_t prot;
  	int error, maxpacketsize;
  
  	struct cryptodesc *crde = NULL, *crda = NULL;
  	struct cryptop *crp;
  
  	sav = isr->sav;
  	KASSERT(sav != NULL, ("esp_output: null SA"));
  	esph = sav->tdb_authalgxform;
  	espx = sav->tdb_encalgxform;
  	KASSERT(espx != NULL, ("esp_output: null encoding xform"));
  
  	if (sav->flags & SADB_X_EXT_OLD)
  		hlen = sizeof (struct esp) + sav->ivlen;
  	else
  		hlen = sizeof (struct newesp) + sav->ivlen;
  
  	rlen = m->m_pkthdr.len - skip;	/* Raw payload length. */
  	/*
  	 * NB: The null encoding transform has a blocksize of 4
  	 *     so that headers are properly aligned.
  	 */
  	blks = espx->blocksize;		/* IV blocksize */
  
  	/* XXX clamp padding length a la KAME??? */
  	padding = ((blks - ((rlen + 2) % blks)) % blks) + 2;
  	plen = rlen + padding;		/* Padded payload length. */
  
  	if (esph)
  		alen = AH_HMAC_HASHLEN;
  	else
  		alen = 0;
  
  	espstat.esps_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 /* INET */
  #ifdef INET6
  	case AF_INET6:
  		maxpacketsize = IPV6_MAXPACKET;
  		break;
  #endif /* INET6 */
  	default:
  		DPRINTF(("esp_output: unknown/unsupported protocol "
  		    "family %d, SA %s/%08lx\n",
  		    saidx->dst.sa.sa_family, ipsec_address(&saidx->dst),
  		    (u_long) ntohl(sav->spi)));
  		espstat.esps_nopf++;
  		error = EPFNOSUPPORT;
  		goto bad;
  	}
  	if (skip + hlen + rlen + padding + alen > maxpacketsize) {
  		DPRINTF(("esp_output: packet in SA %s/%08lx got too big "
  		    "(len %u, max len %u)\n",
  		    ipsec_address(&saidx->dst), (u_long) ntohl(sav->spi),
  		    skip + hlen + rlen + padding + alen, maxpacketsize));
  		espstat.esps_toobig++;
  		error = EMSGSIZE;
  		goto bad;
  	}
  
  	/* Update the counters. */
  	espstat.esps_obytes += m->m_pkthdr.len - skip;
  
  	m = m_clone(m);
  	if (m == NULL) {
  		DPRINTF(("esp_output: cannot clone mbuf chain, SA %s/%08lx\n",
  		    ipsec_address(&saidx->dst), (u_long) ntohl(sav->spi)));
  		espstat.esps_hdrops++;
  		error = ENOBUFS;
  		goto bad;
  	}
  
  	/* Inject ESP header. */
  	mo = m_makespace(m, skip, hlen, &roff);
  	if (mo == NULL) {
  		DPRINTF(("esp_output: failed to inject %u byte ESP hdr for SA "
  		    "%s/%08lx\n",
  		    hlen, ipsec_address(&saidx->dst),
  		    (u_long) ntohl(sav->spi)));
  		espstat.esps_hdrops++;		/* XXX diffs from openbsd */
  		error = ENOBUFS;
  		goto bad;
  	}
  
  	/* Initialize ESP header. */
  	bcopy((caddr_t) &sav->spi, mtod(mo, caddr_t) + roff, sizeof(u_int32_t));
  	if (sav->replay) {
  		u_int32_t replay = htonl(++(sav->replay->count));
  		bcopy((caddr_t) &replay,
  		    mtod(mo, caddr_t) + roff + sizeof(u_int32_t),
  		    sizeof(u_int32_t));
  	}
  
  	/*
  	 * Add padding -- better to do it ourselves than use the crypto engine,
  	 * although if/when we support compression, we'd have to do that.
  	 */
  	pad = (u_char *) m_pad(m, padding + alen);
  	if (pad == NULL) {
  		DPRINTF(("esp_output: m_pad failed for SA %s/%08lx\n",
  		    ipsec_address(&saidx->dst), (u_long) ntohl(sav->spi)));
  		m = NULL;		/* NB: free'd by m_pad */
  		error = ENOBUFS;
  		goto bad;
  	}
  
  	/*
  	 * Add padding: random, zero, or self-describing.
  	 * XXX catch unexpected setting
  	 */
  	switch (sav->flags & SADB_X_EXT_PMASK) {
  	case SADB_X_EXT_PRAND:
  		read_random(pad, padding - 2);
  		break;
  	case SADB_X_EXT_PZERO:
  		bzero(pad, padding - 2);
  		break;
  	case SADB_X_EXT_PSEQ:
  		for (i = 0; i < padding - 2; i++)
  			pad[i] = i+1;
  		break;
  	}
  
  	/* Fix padding length and Next Protocol in padding itself. */
  	pad[padding - 2] = padding - 2;
  	m_copydata(m, protoff, sizeof(u_int8_t), pad + padding - 1);
  
  	/* Fix Next Protocol in IPv4/IPv6 header. */
  	prot = IPPROTO_ESP;
  	m_copyback(m, protoff, sizeof(u_int8_t), (u_char *) &prot);
  
  	/* Get crypto descriptors. */
  	crp = crypto_getreq(esph && espx ? 2 : 1);
  	if (crp == NULL) {
  		DPRINTF(("esp_output: failed to acquire crypto descriptors\n"));
  		espstat.esps_crypto++;
  		error = ENOBUFS;
  		goto bad;
  	}
  
  	if (espx) {
  		crde = crp->crp_desc;
  		crda = crde->crd_next;
  
  		/* Encryption descriptor. */
  		crde->crd_skip = skip + hlen;
  		crde->crd_len = m->m_pkthdr.len - (skip + hlen + alen);
  		crde->crd_flags = CRD_F_ENCRYPT;
  		crde->crd_inject = skip + hlen - sav->ivlen;
  
  		/* Encryption operation. */
  		crde->crd_alg = espx->type;
  		crde->crd_key = _KEYBUF(sav->key_enc);
  		crde->crd_klen = _KEYBITS(sav->key_enc);
  		/* XXX Rounds ? */
  	} else
  		crda = crp->crp_desc;
  
  	/* IPsec-specific opaque crypto info. */
  	tc = kmalloc(sizeof(struct tdb_crypto),
  			M_XDATA, M_INTWAIT | M_ZERO | M_NULLOK);
  	if (tc == NULL) {
  		crypto_freereq(crp);
  		DPRINTF(("esp_output: failed to allocate tdb_crypto\n"));
  		espstat.esps_crypto++;
  		error = ENOBUFS;
  		goto bad;
  	}
  
  	/* Callback parameters */
  	tc->tc_isr = isr;
  	tc->tc_spi = sav->spi;
  	tc->tc_dst = saidx->dst;
  	tc->tc_proto = saidx->proto;
  
  	/* Crypto operation descriptor. */
  	crp->crp_ilen = m->m_pkthdr.len; /* Total input length. */
  	crp->crp_flags = CRYPTO_F_IMBUF;
  	crp->crp_buf = (caddr_t) m;
  	crp->crp_callback = esp_output_cb;
  	crp->crp_opaque = (caddr_t) tc;
  	crp->crp_sid = sav->tdb_cryptoid;
  
  	if (esph) {
  		/* Authentication descriptor. */
  		crda->crd_skip = skip;
  		crda->crd_len = m->m_pkthdr.len - (skip + alen);
  		crda->crd_inject = m->m_pkthdr.len - alen;
  
  		/* Authentication operation. */
  		crda->crd_alg = esph->type;
  		crda->crd_key = _KEYBUF(sav->key_auth);
  		crda->crd_klen = _KEYBITS(sav->key_auth);
  	}
  
  	return crypto_dispatch(crp);
  bad:
  	if (m)
  		m_freem(m);
  	return (error);
  }
  
  /*
   * ESP output callback from the crypto driver.
   */
  static int
  esp_output_cb(struct cryptop *crp)
  {
  	struct tdb_crypto *tc;
  	struct ipsecrequest *isr;
  	struct secasvar *sav;
  	struct mbuf *m;
  	int err, error;
  
  	tc = (struct tdb_crypto *) crp->crp_opaque;
  	KASSERT(tc != NULL, ("esp_output_cb: null opaque data area!"));
  	m = (struct mbuf *) crp->crp_buf;
  
  	crit_enter();
  
  	isr = tc->tc_isr;
  	sav = KEY_ALLOCSA(&tc->tc_dst, tc->tc_proto, tc->tc_spi);
  	if (sav == NULL) {
  		espstat.esps_notdb++;
  		DPRINTF(("esp_output_cb: SA expired while in crypto "
  		    "(SA %s/%08lx proto %u)\n", ipsec_address(&tc->tc_dst),
  		    (u_long) ntohl(tc->tc_spi), tc->tc_proto));
  		error = ENOBUFS;		/*XXX*/
  		goto bad;
  	}
  	KASSERT(isr->sav == sav,
  		("esp_output_cb: SA changed was %p now %p\n", isr->sav, sav));
  
  	/* Check for crypto errors. */
  	if (crp->crp_etype) {
  		/* Reset session ID. */
  		if (sav->tdb_cryptoid != 0)
  			sav->tdb_cryptoid = crp->crp_sid;
  
  		if (crp->crp_etype == EAGAIN) {
  			KEY_FREESAV(&sav);
  			crit_exit();
  			return crypto_dispatch(crp);
  		}
  
  		espstat.esps_noxform++;
  		DPRINTF(("esp_output_cb: crypto error %d\n", crp->crp_etype));
  		error = crp->crp_etype;
  		goto bad;
  	}
  
  	/* Shouldn't happen... */
  	if (m == NULL) {
  		espstat.esps_crypto++;
  		DPRINTF(("esp_output_cb: bogus returned buffer from crypto\n"));
  		error = EINVAL;
  		goto bad;
  	}
  	espstat.esps_hist[sav->alg_enc]++;
  	if (sav->tdb_authalgxform != NULL)
  		ahstat.ahs_hist[sav->alg_auth]++;
  
  	/* Release crypto descriptors. */
  	kfree(tc, M_XDATA);
  	crypto_freereq(crp);
  
  	/* NB: m is reclaimed by ipsec_process_done. */
  	err = ipsec_process_done(m, isr);
  	KEY_FREESAV(&sav);
  	crit_exit();
  	return err;
  bad:
  	if (sav)
  		KEY_FREESAV(&sav);
  	crit_exit();
  	if (m)
  		m_freem(m);
  	kfree(tc, M_XDATA);
  	crypto_freereq(crp);
  	return error;
  }
  
  static struct xformsw esp_xformsw = {
  	XF_ESP,		XFT_CONF|XFT_AUTH,	"IPsec ESP",
  	esp_init,	esp_zeroize,		esp_input,
  	esp_output
  };
  
  static void
  esp_attach(void)
  {
  #define	MAXIV(xform)					\
  	if (xform.blocksize > esp_max_ivlen)		\
  		esp_max_ivlen = xform.blocksize		\
  
  	esp_max_ivlen = 0;
  	MAXIV(enc_xform_des);		/* SADB_EALG_DESCBC */
  	MAXIV(enc_xform_3des);		/* SADB_EALG_3DESCBC */
  	MAXIV(enc_xform_rijndael128);	/* 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_null);		/* SADB_EALG_NULL */
  
  	xform_register(&esp_xformsw);
  #undef MAXIV
  }
  SYSINIT(esp_xform_init, SI_SUB_DRIVERS, SI_ORDER_FIRST, esp_attach, NULL);
  