kex_choose_conf(struct ssh *ssh)
{
	struct kex *kex = ssh->kex;
	struct newkeys *newkeys;
	char **my = NULL, **peer = NULL;
	char **cprop, **sprop;
	int nenc, nmac, ncomp;
	u_int mode, ctos, need, dh_need, authlen;
	int r, first_kex_follows;

	debug2("local %s KEXINIT proposal", kex->server ? "server" : "client");
	if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0)
		goto out;
	debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server");
	if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
		goto out;

	if (kex->server) {
		cprop=peer;
		sprop=my;
	} else {
		cprop=my;
		sprop=peer;
	}

	/* Check whether client supports ext_info_c */
	if (kex->server) {
		char *ext;

		ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
		kex->ext_info_c = (ext != NULL);
		free(ext);
	}

	/* Algorithm Negotiation */
	if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
	    sprop[PROPOSAL_KEX_ALGS])) != 0) {
		kex->failed_choice = peer[PROPOSAL_KEX_ALGS];
		peer[PROPOSAL_KEX_ALGS] = NULL;
		goto out;
	}
	if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
	    sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) {
		kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS];
		peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL;
		goto out;
	}
	for (mode = 0; mode < MODE_MAX; mode++) {
		if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
			r = SSH_ERR_ALLOC_FAIL;
			goto out;
		}
		kex->newkeys[mode] = newkeys;
		ctos = (!kex->server && mode == MODE_OUT) ||
		    (kex->server && mode == MODE_IN);
		nenc  = ctos ? PROPOSAL_ENC_ALGS_CTOS  : PROPOSAL_ENC_ALGS_STOC;
		nmac  = ctos ? PROPOSAL_MAC_ALGS_CTOS  : PROPOSAL_MAC_ALGS_STOC;
		ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
		if ((r = choose_enc(&newkeys->enc, cprop[nenc],
		    sprop[nenc])) != 0) {
			kex->failed_choice = peer[nenc];
			peer[nenc] = NULL;
			goto out;
		}
		authlen = cipher_authlen(newkeys->enc.cipher);
		/* ignore mac for authenticated encryption */
		if (authlen == 0 &&
		    (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
		    sprop[nmac])) != 0) {
			kex->failed_choice = peer[nmac];
			peer[nmac] = NULL;
			goto out;
		}
		if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
		    sprop[ncomp])) != 0) {
			kex->failed_choice = peer[ncomp];
			peer[ncomp] = NULL;
			goto out;
		}
		debug("kex: %s cipher: %s MAC: %s compression: %s",
		    ctos ? "client->server" : "server->client",
		    newkeys->enc.name,
		    authlen == 0 ? newkeys->mac.name : "<implicit>",
		    newkeys->comp.name);
	}
	need = dh_need = 0;
	for (mode = 0; mode < MODE_MAX; mode++) {
		newkeys = kex->newkeys[mode];
		need = MAXIMUM(need, newkeys->enc.key_len);
		need = MAXIMUM(need, newkeys->enc.block_size);
		need = MAXIMUM(need, newkeys->enc.iv_len);
		need = MAXIMUM(need, newkeys->mac.key_len);
		dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher));
		dh_need = MAXIMUM(dh_need, newkeys->enc.block_size);
		dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len);
		dh_need = MAXIMUM(dh_need, newkeys->mac.key_len);
	}
	/* XXX need runden? */
	kex->we_need = need;
	kex->dh_need = dh_need;

	/* ignore the next message if the proposals do not match */
	if (first_kex_follows && !proposals_match(my, peer) &&
	    !(ssh->compat & SSH_BUG_FIRSTKEX))
		ssh->dispatch_skip_packets = 1;
	r = 0;
 out:
	kex_prop_free(my);
	kex_prop_free(peer);
	return r;
}