};

struct ssh_tag {
    const struct plug_function_table *fn;
    /* the above field _must_ be first in the structure */

    char *v_c, *v_s;
    void *exhash;

    Socket s;

    void *ldisc;
    void *logctx;

    unsigned char session_key[32];

    const struct ssh_mac *csmac, *scmac;
    void *cs_mac_ctx, *sc_mac_ctx;
    const struct ssh_compress *cscomp, *sccomp;
    void *cs_comp_ctx, *sc_comp_ctx;
    const struct ssh_kex *kex;
    const struct ssh_signkey *hostkey;
    unsigned char v2_session_id[20];
    int v2_session_id_len;
    void *kex_ctx;

    char *savedhost;
    int savedport;
    int send_ok;
    int echoing, editing;

    if (av != bv)
	return (av < bv ? -1 : +1);
    return 0;
}

/*
 * Utility routines for putting an SSH-protocol `string' and
 * `uint32' into a hash state.
 */
static void hash_string(const struct ssh_hash *h, void *s, void *str, int len)
{
    unsigned char lenblk[4];
    PUT_32BIT(lenblk, len);
    h->bytes(s, lenblk, 4);
    h->bytes(s, str, len);
}

static void hash_uint32(const struct ssh_hash *h, void *s, unsigned i)
{
    unsigned char intblk[4];
    PUT_32BIT(intblk, i);
    h->bytes(s, intblk, 4);
}

/*
 * Packet construction functions. Mostly shared between SSH-1 and SSH-2.
 */
static void ssh_pkt_ensure(struct Packet *pkt, int length)
{

    for (i = 0; i < len; i++)
	debug((" %02x", p[i]));
    debug(("\n"));
    sfree(p);
}
#endif

static void hash_mpint(const struct ssh_hash *h, void *s, Bignum b)
{
    unsigned char *p;
    int len;
    p = ssh2_mpint_fmt(b, &len);
    hash_string(h, s, p, len);
    sfree(p);
}

/*
 * Packet decode functions for both SSH-1 and SSH-2.
 */
static unsigned long ssh_pkt_getuint32(struct Packet *pkt)

    return 0;
}


/*
 * SSH-2 key creation method.
 */
static void ssh2_mkkey(Ssh ssh, Bignum K, unsigned char *H, char chr,

		       unsigned char *keyspace)
{
    const struct ssh_hash *h = ssh->kex->hash;
    void *s;
    /* First hlen bytes. */
    s = h->init();
    if (!(ssh->remote_bugs & BUG_SSH2_DERIVEKEY))
	hash_mpint(h, s, K);
    h->bytes(s, H, h->hlen);
    h->bytes(s, &chr, 1);
    h->bytes(s, ssh->v2_session_id, ssh->v2_session_id_len);
    h->final(s, keyspace);
    /* Next hlen bytes. */
    s = h->init();
    if (!(ssh->remote_bugs & BUG_SSH2_DERIVEKEY))
	hash_mpint(h, s, K);
    h->bytes(s, H, h->hlen);
    h->bytes(s, keyspace, h->hlen);
    h->final(s, keyspace + h->hlen);
}

/*
 * Handle the SSH-2 transport layer.
 */
static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
			     struct Packet *pktin)

	    if (s->dlgret == 0) {
		ssh_disconnect(ssh, "User aborted at cipher warning", NULL,
			       0, TRUE);
		crStop(0);
	    }
	}

	ssh->exhash = ssh->kex->hash->init();
	hash_string(ssh->kex->hash, ssh->exhash, ssh->v_c, strlen(ssh->v_c));
	hash_string(ssh->kex->hash, ssh->exhash, ssh->v_s, strlen(ssh->v_s));
	hash_string(ssh->kex->hash, ssh->exhash,
	    s->our_kexinit, s->our_kexinitlen);
	sfree(s->our_kexinit);
	if (pktin->length > 5)
	    hash_string(ssh->kex->hash, ssh->exhash,
		pktin->data + 5, pktin->length - 5);


	if (s->ignorepkt) /* first_kex_packet_follows */
	    crWaitUntil(pktin);                /* Ignore packet */
    }

    /*
     * Work out the number of bits of key we will need from the key
     * exchange. We start with the maximum key length of either
     * cipher...
     */
    {
	int csbits, scbits;

	csbits = s->cscipher_tobe->keylen;
	scbits = s->sccipher_tobe->keylen;
	s->nbits = (csbits > scbits ? csbits : scbits);
    }
    /* The keys only have hlen-bit entropy, since they're based on
     * a hash. So cap the key size at hlen bits. */
    if (s->nbits > ssh->kex->hash->hlen * 8)
	s->nbits = ssh->kex->hash->hlen * 8;

    /*
     * If we're doing Diffie-Hellman group exchange, start by
     * requesting a group.
     */
    if (!ssh->kex->pdata) {
	logevent("Doing Diffie-Hellman group exchange");

    s->K = dh_find_K(ssh->kex_ctx, s->f);

    /* We assume everything from now on will be quick, and it might
     * involve user interaction. */
    set_busy_status(ssh->frontend, BUSY_NOT);

    hash_string(ssh->kex->hash, ssh->exhash, s->hostkeydata, s->hostkeylen);
    if (ssh->kex == &ssh_diffiehellman_gex) {
	hash_uint32(ssh->kex->hash, ssh->exhash, s->pbits);
	hash_mpint(ssh->kex->hash, ssh->exhash, s->p);
	hash_mpint(ssh->kex->hash, ssh->exhash, s->g);
    }
    hash_mpint(ssh->kex->hash, ssh->exhash, s->e);
    hash_mpint(ssh->kex->hash, ssh->exhash, s->f);
    hash_mpint(ssh->kex->hash, ssh->exhash, s->K);
    assert(ssh->kex->hash->hlen <= sizeof(s->exchange_hash));
    ssh->kex->hash->final(ssh->exhash, s->exchange_hash);

    dh_cleanup(ssh->kex_ctx);
    ssh->kex_ctx = NULL;

#if 0
    debug(("Exchange hash is:\n"));
    dmemdump(s->exchange_hash, ssh->kex->hash->hlen);
#endif

    s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
    if (!s->hkey ||
	!ssh->hostkey->verifysig(s->hkey, s->sigdata, s->siglen,
				 (char *)s->exchange_hash,
				 ssh->kex->hash->hlen)) {
	bombout(("Server's host key did not match the signature supplied"));
	crStop(0);
    }

    /*
     * Authenticate remote host: verify host key. (We've already
     * checked the signature of the exchange hash.)

    /*
     * The exchange hash from the very first key exchange is also
     * the session id, used in session key construction and
     * authentication.
     */
    if (!s->got_session_id) {
	assert(sizeof(s->exchange_hash) <= sizeof(ssh->v2_session_id));
	memcpy(ssh->v2_session_id, s->exchange_hash,
	       sizeof(s->exchange_hash));
	assert(ssh->v2_session_id_len <= sizeof(ssh->v2_session_id));
	ssh->v2_session_id_len = ssh->kex->hash->hlen;
	s->got_session_id = TRUE;
    }

    /*
     * Send SSH2_MSG_NEWKEYS.
     */
    s->pktout = ssh2_pkt_init(SSH2_MSG_NEWKEYS);

    /*
     * Set IVs on client-to-server keys. Here we use the exchange
     * hash from the _first_ key exchange.
     */
    {
	unsigned char keyspace[40];
	ssh2_mkkey(ssh,s->K,s->exchange_hash,'C',keyspace);
	ssh->cscipher->setkey(ssh->cs_cipher_ctx, keyspace);
	ssh2_mkkey(ssh,s->K,s->exchange_hash,'A',keyspace);
	ssh->cscipher->setiv(ssh->cs_cipher_ctx, keyspace);
	ssh2_mkkey(ssh,s->K,s->exchange_hash,'E',keyspace);
	ssh->csmac->setkey(ssh->cs_mac_ctx, keyspace);
    }

    logeventf(ssh, "Initialised %.200s client->server encryption",
	      ssh->cscipher->text_name);
    logeventf(ssh, "Initialised %.200s client->server MAC algorithm",
	      ssh->csmac->text_name);

    /*
     * Set IVs on server-to-client keys. Here we use the exchange
     * hash from the _first_ key exchange.
     */
    {
	unsigned char keyspace[40];
	ssh2_mkkey(ssh,s->K,s->exchange_hash,'D',keyspace);
	ssh->sccipher->setkey(ssh->sc_cipher_ctx, keyspace);
	ssh2_mkkey(ssh,s->K,s->exchange_hash,'B',keyspace);
	ssh->sccipher->setiv(ssh->sc_cipher_ctx, keyspace);
	ssh2_mkkey(ssh,s->K,s->exchange_hash,'F',keyspace);
	ssh->scmac->setkey(ssh->sc_mac_ctx, keyspace);
    }
    logeventf(ssh, "Initialised %.200s server->client encryption",
	      ssh->sccipher->text_name);
    logeventf(ssh, "Initialised %.200s server->client MAC algorithm",
	      ssh->scmac->text_name);
    if (ssh->sccomp->text_name)

			ssh2_pkt_addstring(s->pktout, "publickey");	/* method */
			ssh2_pkt_addbool(s->pktout, TRUE);
			ssh2_pkt_addstring_start(s->pktout);
			ssh2_pkt_addstring_data(s->pktout, s->alg, s->alglen);
			ssh2_pkt_addstring_start(s->pktout);
			ssh2_pkt_addstring_data(s->pktout, s->pkblob, s->pklen);

			s->siglen = s->pktout->length - 5 + 4 +
			    ssh->v2_session_id_len;
                        if (ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)
                            s->siglen -= 4;
			s->len = 1;       /* message type */
			s->len += 4 + s->pklen;	/* key blob */
			s->len += 4 + s->siglen;	/* data to sign */
			s->len += 4;      /* flags */
			s->agentreq = snewn(4 + s->len, char);
			PUT_32BIT(s->agentreq, s->len);
			s->q = s->agentreq + 4;
			*s->q++ = SSH2_AGENTC_SIGN_REQUEST;
			PUT_32BIT(s->q, s->pklen);
			s->q += 4;
			memcpy(s->q, s->pkblob, s->pklen);
			s->q += s->pklen;
			PUT_32BIT(s->q, s->siglen);
			s->q += 4;
			/* Now the data to be signed... */
                        if (!(ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)) {
                            PUT_32BIT(s->q, ssh->v2_session_id_len);
                            s->q += 4;
                        }
			memcpy(s->q, ssh->v2_session_id,
			       ssh->v2_session_id_len);
			s->q += ssh->v2_session_id_len;
			memcpy(s->q, s->pktout->data + 5,
			       s->pktout->length - 5);
			s->q += s->pktout->length - 5;
			/* And finally the (zero) flags word. */
			PUT_32BIT(s->q, 0);
			if (!agent_query(s->agentreq, s->len + 4,
					 &vret, &s->retlen,

		     * The data to be signed is:
		     *
		     *   string  session-id
		     *
		     * followed by everything so far placed in the
		     * outgoing packet.
		     */
		    sigdata_len = s->pktout->length - 5 + 4 +
			ssh->v2_session_id_len;
                    if (ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)
                        sigdata_len -= 4;
		    sigdata = snewn(sigdata_len, unsigned char);
                    p = 0;
                    if (!(ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)) {
                        PUT_32BIT(sigdata+p, ssh->v2_session_id_len);
                        p += 4;
                    }
		    memcpy(sigdata+p, ssh->v2_session_id,
			   ssh->v2_session_id_len);
		    p += ssh->v2_session_id_len;
		    memcpy(sigdata+p, s->pktout->data + 5,
			   s->pktout->length - 5);
                    p += s->pktout->length - 5;
                    assert(p == sigdata_len);
		    sigblob = key->alg->sign(key->data, (char *)sigdata,
					     sigdata_len, &sigblob_len);
		    ssh2_add_sigblob(ssh, s->pktout, pkblob, pkblob_len,