static void
client_alive_check(void)
{
	static int had_channel = 0;
	int id;

	id = channel_find_open();
	if (id == -1) {
		if (!had_channel)
			return;
		packet_disconnect("No open channels after timeout!");
	}
	had_channel = 1;

	/* timeout, check to see how many we have had */
	if (++client_alive_timeouts > options.client_alive_count_max)
		packet_disconnect("Timeout, your session not responding.");

	/*
	 * send a bogus channel request with "wantreply",
	 * we should get back a failure
	 */
	channel_request_start(id, "[email protected]", 1);
	packet_send();
}

static void
server_input_channel_req(int type, u_int32_t seq, void *ctxt)
{
	Channel *c;
	int id, reply, success = 0;
	char *rtype;

	id = packet_get_int();
	rtype = packet_get_string(NULL);
	reply = packet_get_char();

	debug("server_input_channel_req: channel %d request %s reply %d",
	    id, rtype, reply);

	if ((c = channel_lookup(id)) == NULL)
		packet_disconnect("server_input_channel_req: "
		    "unknown channel %d", id);
	if (!strcmp(rtype, "[email protected]")) {
		packet_check_eom();
		chan_rcvd_eow(c);
	} else if ((c->type == SSH_CHANNEL_LARVAL ||
	    c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
		success = session_input_channel_req(c, rtype);
	if (reply) {
		packet_start(success ?
		    SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
		packet_put_int(c->remote_id);
		packet_send();
	}
	free(rtype);
}

/*ARGSUSED*/
static void
input_service_request(int type, u_int32_t seq, void *ctxt)
{
	Authctxt *authctxt = ctxt;
	u_int len;
	int acceptit = 0;
	char *service = packet_get_cstring(&len);
	packet_check_eom();

	if (authctxt == NULL)
		fatal("input_service_request: no authctxt");

	if (strcmp(service, "ssh-userauth") == 0) {
		if (!authctxt->success) {
			acceptit = 1;
			/* now we can handle user-auth requests */
			dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
		}
	}
	/* XXX all other service requests are denied */

	if (acceptit) {
		packet_start(SSH2_MSG_SERVICE_ACCEPT);
		packet_put_cstring(service);
		packet_send();
		packet_write_wait();
	} else {
		debug("bad service request %s", service);
		packet_disconnect("bad service request %s", service);
	}
	free(service);
}

static Channel *
server_request_session(void)
{
	Channel *c;

	debug("input_session_request");
	packet_check_eom();

	if (no_more_sessions) {
		packet_disconnect("Possible attack: attempt to open a session "
		    "after additional sessions disabled");
	}

	/*
	 * A server session has no fd to read or write until a
	 * CHANNEL_REQUEST for a shell is made, so we set the type to
	 * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
	 * CHANNEL_REQUEST messages is registered.
	 */
	c = channel_new("session", SSH_CHANNEL_LARVAL,
	    -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
	    0, "server-session", 1);
	if (session_open(the_authctxt, c->self) != 1) {
		debug("session open failed, free channel %d", c->self);
		channel_free(c);
		return NULL;
	}
	channel_register_cleanup(c->self, session_close_by_channel, 0);
	return c;
}

/* IPv4 only */
static void
check_ip_options(int socket, char *ipaddr)
{
#ifdef IP_OPTIONS
	u_char options[200];
	char text[sizeof(options) * 3 + 1];
	socklen_t option_size;
	int i, ipproto;
	struct protoent *ip;

	if ((ip = getprotobyname("ip")) != NULL)
		ipproto = ip->p_proto;
	else
		ipproto = IPPROTO_IP;
	option_size = sizeof(options);
	if (getsockopt(socket, ipproto, IP_OPTIONS, options,
	    &option_size) >= 0 && option_size != 0) {
		text[0] = '\0';
		for (i = 0; i < option_size; i++)
			snprintf(text + i*3, sizeof(text) - i*3,
			    " %2.2x", options[i]);
		logit("Connection from %.100s with IP options:%.800s",
		    ipaddr, text);
		packet_disconnect("Connection from %.100s with IP options:%.800s",
		    ipaddr, text);
	}
#endif /* IP_OPTIONS */
}

/*
 * Performs authentication of an incoming connection.  Session key has already
 * been exchanged and encryption is enabled.
 */
Authctxt *
do_authentication(void)
{
	Authctxt *authctxt;
	u_int ulen;
	char *user, *style = NULL;

	/* Get the name of the user that we wish to log in as. */
	packet_read_expect(SSH_CMSG_USER);

	/* Get the user name. */
	user = packet_get_string(&ulen);
	packet_check_eom();

	if ((style = strchr(user, ':')) != NULL)
		*style++ = '\0';

	authctxt = authctxt_new();
	authctxt->user = user;
	authctxt->style = style;

	/* Verify that the user is a valid user. */
	if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
		authctxt->valid = 1;
	else {
		debug("do_authentication: illegal user %s", user);
		authctxt->pw = fakepw();
	}

	setproctitle("%s%s", authctxt->pw ? user : "unknown",
	    use_privsep ? " [net]" : "");

#ifdef USE_PAM
	if (options.use_pam)
		PRIVSEP(start_pam(user));
#endif

	/*
	 * If we are not running as root, the user must have the same uid as
	 * the server. (Unless you are running Windows)
	 */
#ifndef HAVE_CYGWIN
	if (!use_privsep && getuid() != 0 && authctxt->pw &&
	    authctxt->pw->pw_uid != getuid())
		packet_disconnect("Cannot change user when server not running as root.");
#endif

	/*
	 * Loop until the user has been authenticated or the connection is
	 * closed, do_authloop() returns only if authentication is successful
	 */
	do_authloop(authctxt);

	/* The user has been authenticated and accepted. */
	packet_start(SSH_SMSG_SUCCESS);
	packet_send();
	packet_write_wait();

	return (authctxt);
}

//.........这里部分代码省略.........
    socklen_t sinlen;
    char addr_buf[IPLEN];
    int sockfd,count;
    time_t lasttime,now;
    lasttime=time(NULL);
    count=0;
    while (1) {
        sinlen=sizeof(KBS_SOCKADDR_IN);
#ifdef SMTH
        if ((now=time(NULL))!=lasttime)
            count=0;
        else {
            if (count>5)
                sleep(1);
        }
#endif /* SMTH */
        sockfd=accept(SOCKFD,(struct sockaddr*)&sin,&sinlen);
        count++;
        if (sockfd==-1)
            continue;
        proxy_getpeername(sockfd,(struct sockaddr*)&sin,&sinlen);
#ifdef CHECK_IP_LINK
#ifdef HAVE_IPV6_SMTH
        if (check_IP_lists(sin.sin6_addr)==1) {
#else /* ! HAVE_IPV6_SMTH */
        if (check_IP_lists(sin.sin_addr.s_addr)==1) {
#endif /* HAVE_IPV6_SMTH */
            close(sockfd);
            continue;
        }
#endif /* CHECK_IP_LINK */
        if (!no_fork) {
            switch (fork()) {
                case -1:
                    exit(3);
                case 0:
                    break;
                default:
                    close(sockfd);
                    continue;
            }
        }
        KBS_SET_FROMHOST(sin,addr_buf);
        bbslog("0Connect","connect from %d (%d) in port %d",addr_buf,htons(KBS_SIN_MEMBER(sin,port)),mport);
        setsid();
        if (dup2(sockfd,0)==-1)     /* dup tcp link to fd 0 and then in the main_bbs func also to fd 1 */
            exit(2);
        close(3);                   /* close listen sock fd in child session */
        close(4);                   /* close pid file fd in child session */
        close(sockfd);              /* close accept peer fd in child session */
        break;                      /* leave fd 2 still open holding /dev/null */
    }
    KBS_SET_FROMHOST(sin,getSession()->fromhost);
    telnet_init();
    return bbs_main(argv);
}
int main(int argc,char **argv) {
    char addr[STRLEN];
    int ret,inetd,port;
    addr[0]=0;inetd=0;port=23;
    while ((ret=getopt(argc,argv,"idha:p:"))!=-1) {
        switch (ret) {
            case 'i':
                inetd=1;
                break;
            case 'd':
                no_fork=1;
                break;
            case 'h':
                puts("usage: bbsd [-i] [-d] [-h] [-a <addr>] [-p <port>]");
                return 0;
            case 'a':
                if (optarg[0])
                    snprintf(addr,STRLEN,"%s",optarg);
                break;
            case 'p':
                if (!isdigit(optarg[0]))
                    return -1;
                port=atoi(optarg);
                break;
            case '?':
                return -1;
        }
    }
#ifndef HAVE_IPV6_SMTH
    inaddr_any.s_addr=htonl(INADDR_ANY);
#endif /* HAVE_IPV6_SMTH */
    start_daemon(inetd,port,(!addr[0]?NULL:addr));
    main_signals();
    return (!inetd?bbs_standalone_main(argv[0]):bbs_inet_main(argv[0]));
}
#else /* SSHBBS */
void ssh_exit(void) {
    if (ssh_exiting)
        return;
    ssh_exiting=1;
    abort_bbs(0);
    packet_disconnect("sshbbsd exit");
    return;
}

static void
server_alive_check(void)
{
	if (++server_alive_timeouts > options.server_alive_count_max)
		packet_disconnect("Timeout, server not responding.");
	packet_start(SSH2_MSG_GLOBAL_REQUEST);
	packet_put_cstring("[email protected]");
	packet_put_char(1);     /* boolean: want reply */
	packet_send();
}

/*
 * Computes the proper response to a RSA challenge, and sends the response to
 * the server.
 */
static void
respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv)
{
	u_char buf[32], response[16];
	struct ssh_digest_ctx *md;
	int i, len;

	/* Decrypt the challenge using the private key. */
	/* XXX think about Bleichenbacher, too */
	if (rsa_private_decrypt(challenge, challenge, prv) != 0)
		packet_disconnect(
		    "respond_to_rsa_challenge: rsa_private_decrypt failed");

	/* Compute the response. */
	/* The response is MD5 of decrypted challenge plus session id. */
	len = BN_num_bytes(challenge);
	if (len <= 0 || (u_int)len > sizeof(buf))
		packet_disconnect(
		    "respond_to_rsa_challenge: bad challenge length %d", len);

	memset(buf, 0, sizeof(buf));
	BN_bn2bin(challenge, buf + sizeof(buf) - len);
	if ((md = ssh_digest_start(SSH_DIGEST_MD5)) == NULL ||
	    ssh_digest_update(md, buf, 32) < 0 ||
	    ssh_digest_update(md, session_id, 16) < 0 ||
	    ssh_digest_final(md, response, sizeof(response)) < 0)
		fatal("%s: md5 failed", __func__);
	ssh_digest_free(md);

	debug("Sending response to host key RSA challenge.");

	/* Send the response back to the server. */
	packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
	for (i = 0; i < 16; i++)
		packet_put_char(response[i]);
	packet_send();
	packet_write_wait();

	explicit_bzero(buf, sizeof(buf));
	explicit_bzero(response, sizeof(response));
	explicit_bzero(&md, sizeof(md));
}

void
auth_maxtries_exceeded(Authctxt *authctxt)
{
	error("maximum authentication attempts exceeded for "
	    "%s%.100s from %.200s port %d %s",
	    authctxt->valid ? "" : "invalid user ",
	    authctxt->user,
	    get_remote_ipaddr(),
	    get_remote_port(),
	    compat20 ? "ssh2" : "ssh1");
	packet_disconnect("Too many authentication failures");
	/* NOTREACHED */
}

void
auth_maxtries_exceeded(Authctxt *authctxt)
{
	struct ssh *ssh = active_state; /* XXX */

	error("maximum authentication attempts exceeded for "
	    "%s%.100s from %.200s port %d ssh2",
	    authctxt->valid ? "" : "invalid user ",
	    authctxt->user,
	    ssh_remote_ipaddr(ssh),
	    ssh_remote_port(ssh));
	packet_disconnect("Too many authentication failures");
	/* NOTREACHED */
}

void PTYPars::read_from_packet (CoreConnection* con)
{
	u_int len;
	int n_bytes;

#if 0 // FIXME
	if (s->ttyfd != -1) {
		packet_disconnect("Protocol error: you already have a pty.");
		return 0;
	}
#endif

	const char* term2 = con-> packet_get_string(&len);
  term = term2;
  xfree ((void*) term2);

  col = con-> packet_get_int();
	row = con-> packet_get_int();
	xpixel = con-> packet_get_int();
	ypixel = con-> packet_get_int();

#if 0
	/* Allocate a pty and open it. */
	debug("Allocating pty.");
	if (!PRIVSEP(pty_allocate(&s->ptyfd, &s->ttyfd, s->tty,
	    sizeof(s->tty)))) {
		if (s->term)
			xfree(s->term);
		s->term = NULL;
		s->ptyfd = -1;
		s->ttyfd = -1;
		error("session_pty_req: session %d alloc failed", s->self);
		return 0;
	}
	debug("session_pty_req: session %d alloc %s", s->self, s->tty);
#endif

  PTY::tty_parse_modes(con, &n_bytes);

#if 0
  /* Set window size from the packet. */
	pty_change_window_size(s->ptyfd, s->row, s->col, s->xpixel, s->ypixel);
#endif

	packet_check_eom (con);
}

void
dispatch_run(int mode, int *done, void *ctxt)
{
	for (;;) {
		int type;
		u_int32_t seqnr;

		if (mode == DISPATCH_BLOCK) {
			type = packet_read_seqnr(&seqnr);
		} else {
			type = packet_read_poll_seqnr(&seqnr);
			if (type == SSH_MSG_NONE)
				return;
		}
		if (type > 0 && type < DISPATCH_MAX && dispatch[type] != NULL)
			(*dispatch[type])(type, seqnr, ctxt);
		else
			packet_disconnect("protocol error: rcvd type %d", type);
		if (done != NULL && *done)
			return;
	}
}

void
userauth_user_svc_change(Authctxt *authctxt, char *user, char *service)
{
	/*
	 * NOTE:
	 *
	 * SSHv2 services should be abstracted and service changes during
	 * userauth should be supported as per the userauth draft.  In the PAM
	 * case, support for multiple SSHv2 services means that we have to
	 * format the PAM service name according to the SSHv2 service *and* the
	 * SSHv2 userauth being attempted ("passwd", "kbdint" and "other").
	 *
	 * We'll cross that bridge when we come to it.  For now disallow service
	 * changes during userauth if using PAM, but allow username changes.
	 */

	/* authctxt->service must == ssh-connection here */
	if (service != NULL && strcmp(service, authctxt->service) != 0) {
		packet_disconnect("Change of service not "
				  "allowed: %s and %s",
				  authctxt->service, service);
	}
	if (user != NULL && authctxt->user != NULL &&
	    strcmp(user, authctxt->user) == 0)
		return;

	/* All good; update authctxt */
	xfree(authctxt->user);
	authctxt->user = xstrdup(user);
	pwfree(&authctxt->pw);
	authctxt->pw = getpwnamallow(user);
	authctxt->valid = (authctxt->pw != NULL);

	/* Forget method state; abandon postponed userauths */
	userauth_reset_methods();
}

void
kexgex_server(Kex *kex)
{
	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
	Key *server_host_public, *server_host_private;
	DH *dh;
	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
	u_int sbloblen, klen, slen, hashlen;
	int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
	int type, kout;

	if (kex->load_host_public_key == NULL ||
	    kex->load_host_private_key == NULL)
		fatal("Cannot load hostkey");
	server_host_public = kex->load_host_public_key(kex->hostkey_type);
	if (server_host_public == NULL)
		fatal("Unsupported hostkey type %d", kex->hostkey_type);
	server_host_private = kex->load_host_private_key(kex->hostkey_type);

	type = packet_read();
	switch (type) {
	case SSH2_MSG_KEX_DH_GEX_REQUEST:
		debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
		omin = min = packet_get_int();
		onbits = nbits = packet_get_int();
		omax = max = packet_get_int();
		min = MAX(DH_GRP_MIN, min);
		max = MIN(DH_GRP_MAX, max);
		nbits = MAX(DH_GRP_MIN, nbits);
		nbits = MIN(DH_GRP_MAX, nbits);
		break;
	case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
		debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
		onbits = nbits = packet_get_int();
		/* unused for old GEX */
		omin = min = DH_GRP_MIN;
		omax = max = DH_GRP_MAX;
		break;
	default:
		fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
	}
	packet_check_eom();

	if (omax < omin || onbits < omin || omax < onbits)
		fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
		    omin, onbits, omax);

	/* Contact privileged parent */
	dh = PRIVSEP(choose_dh(min, nbits, max));
	if (dh == NULL)
		packet_disconnect("Protocol error: no matching DH grp found");

	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
	packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
	packet_put_bignum2(dh->p);
	packet_put_bignum2(dh->g);
	packet_send();

	/* flush */
	packet_write_wait();

	/* Compute our exchange value in parallel with the client */
	dh_gen_key(dh, kex->we_need * 8);

	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
	packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);

	/* key, cert */
	if ((dh_client_pub = BN_new()) == NULL)
		fatal("dh_client_pub == NULL");
	packet_get_bignum2(dh_client_pub);
	packet_check_eom();

#ifdef DEBUG_KEXDH
	fprintf(stderr, "dh_client_pub= ");
	BN_print_fp(stderr, dh_client_pub);
	fprintf(stderr, "\n");
	debug("bits %d", BN_num_bits(dh_client_pub));
#endif

#ifdef DEBUG_KEXDH
	DHparams_print_fp(stderr, dh);
	fprintf(stderr, "pub= ");
	BN_print_fp(stderr, dh->pub_key);
	fprintf(stderr, "\n");
#endif
	if (!dh_pub_is_valid(dh, dh_client_pub))
		packet_disconnect("bad client public DH value");

	klen = DH_size(dh);
	kbuf = xmalloc(klen);
	if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
		fatal("DH_compute_key: failed");
#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, kout);
#endif
	if ((shared_secret = BN_new()) == NULL)
		fatal("kexgex_server: BN_new failed");
	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
		fatal("kexgex_server: BN_bin2bn failed");
//.........这里部分代码省略.........

static int
ssh_session(void)
{
	int type;
	int interactive = 0;
	int have_tty = 0;
	struct winsize ws;
	char *cp;
	const char *display;

	/* Enable compression if requested. */
	if (options.compression) {
		debug("Requesting compression at level %d.",
		    options.compression_level);

		if (options.compression_level < 1 ||
		    options.compression_level > 9)
			fatal("Compression level must be from 1 (fast) to "
			    "9 (slow, best).");

		/* Send the request. */
		packet_start(SSH_CMSG_REQUEST_COMPRESSION);
		packet_put_int(options.compression_level);
		packet_send();
		packet_write_wait();
		type = packet_read();
		if (type == SSH_SMSG_SUCCESS)
			packet_start_compression(options.compression_level);
		else if (type == SSH_SMSG_FAILURE)
			logit("Warning: Remote host refused compression.");
		else
			packet_disconnect("Protocol error waiting for "
			    "compression response.");
	}
	/* Allocate a pseudo tty if appropriate. */
	if (tty_flag) {
		debug("Requesting pty.");

		/* Start the packet. */
		packet_start(SSH_CMSG_REQUEST_PTY);

		/* Store TERM in the packet.  There is no limit on the
		   length of the string. */
		cp = getenv("TERM");
		if (!cp)
			cp = "";
		packet_put_cstring(cp);

		/* Store window size in the packet. */
		if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
			memset(&ws, 0, sizeof(ws));
		packet_put_int((u_int)ws.ws_row);
		packet_put_int((u_int)ws.ws_col);
		packet_put_int((u_int)ws.ws_xpixel);
		packet_put_int((u_int)ws.ws_ypixel);

		/* Store tty modes in the packet. */
		tty_make_modes(fileno(stdin), NULL);

		/* Send the packet, and wait for it to leave. */
		packet_send();
		packet_write_wait();

		/* Read response from the server. */
		type = packet_read();
		if (type == SSH_SMSG_SUCCESS) {
			interactive = 1;
			have_tty = 1;
		} else if (type == SSH_SMSG_FAILURE)
			logit("Warning: Remote host failed or refused to "
			    "allocate a pseudo tty.");
		else
			packet_disconnect("Protocol error waiting for pty "
			    "request response.");
	}
	/* Request X11 forwarding if enabled and DISPLAY is set. */
	display = getenv("DISPLAY");
	if (options.forward_x11 && display != NULL) {
		char *proto, *data;
		/* Get reasonable local authentication information. */
		client_x11_get_proto(display, options.xauth_location,
		    options.forward_x11_trusted, 
		    options.forward_x11_timeout,
		    &proto, &data);
		/* Request forwarding with authentication spoofing. */
		debug("Requesting X11 forwarding with authentication "
		    "spoofing.");
		x11_request_forwarding_with_spoofing(0, display, proto,
		    data, 0);
		/* Read response from the server. */
		type = packet_read();
		if (type == SSH_SMSG_SUCCESS) {
			interactive = 1;
		} else if (type == SSH_SMSG_FAILURE) {
			logit("Warning: Remote host denied X11 forwarding.");
		} else {
			packet_disconnect("Protocol error waiting for X11 "
			    "forwarding");
		}
	}
//.........这里部分代码省略.........

void
kexgss_server(Kex *kex)
{
	OM_uint32 maj_status, min_status;
	
	/* 
	 * Some GSSAPI implementations use the input value of ret_flags (an
 	 * output variable) as a means of triggering mechanism specific 
 	 * features. Initializing it to zero avoids inadvertently 
 	 * activating this non-standard behaviour.
	 */

	OM_uint32 ret_flags = 0;
	gss_buffer_desc gssbuf, recv_tok, msg_tok;
	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
	Gssctxt *ctxt = NULL;
	u_int slen, klen, kout, hashlen;
	u_char *kbuf, *hash;
	DH *dh;
	int min = -1, max = -1, nbits = -1;
	BIGNUM *shared_secret = NULL;
	BIGNUM *dh_client_pub = NULL;
	int type = 0;
	gss_OID oid;
	char *mechs;

	/* Initialise GSSAPI */

	/* If we're rekeying, privsep means that some of the private structures
	 * in the GSSAPI code are no longer available. This kludges them back
	 * into life
	 */
	if (!ssh_gssapi_oid_table_ok()) 
		if ((mechs = ssh_gssapi_server_mechanisms()))
			xfree(mechs);

	debug2("%s: Identifying %s", __func__, kex->name);
	oid = ssh_gssapi_id_kex(NULL, kex->name, kex->kex_type);
	if (oid == GSS_C_NO_OID)
	   fatal("Unknown gssapi mechanism");

	debug2("%s: Acquiring credentials", __func__);

	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid))))
		fatal("Unable to acquire credentials for the server");

	switch (kex->kex_type) {
	case KEX_GSS_GRP1_SHA1:
		dh = dh_new_group1();
		break;
	case KEX_GSS_GRP14_SHA1:
		dh = dh_new_group14();
		break;
	case KEX_GSS_GEX_SHA1:
		debug("Doing group exchange");
		packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ);
		min = packet_get_int();
		nbits = packet_get_int();
		max = packet_get_int();
		min = MAX(DH_GRP_MIN, min);
		max = MIN(DH_GRP_MAX, max);
		packet_check_eom();
		if (max < min || nbits < min || max < nbits)
			fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
			    min, nbits, max);
		dh = PRIVSEP(choose_dh(min, nbits, max));
		if (dh == NULL)
			packet_disconnect("Protocol error: no matching group found");

		packet_start(SSH2_MSG_KEXGSS_GROUP);
		packet_put_bignum2(dh->p);
		packet_put_bignum2(dh->g);
		packet_send();

		packet_write_wait();
		break;
	default:
		fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	}

	dh_gen_key(dh, kex->we_need * 8);

	do {
		debug("Wait SSH2_MSG_GSSAPI_INIT");
		type = packet_read();
		switch(type) {
		case SSH2_MSG_KEXGSS_INIT:
			if (dh_client_pub != NULL) 
				fatal("Received KEXGSS_INIT after initialising");
			recv_tok.value = packet_get_string(&slen);
			recv_tok.length = slen; 

			if ((dh_client_pub = BN_new()) == NULL)
				fatal("dh_client_pub == NULL");

			packet_get_bignum2(dh_client_pub);

			/* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
			break;
		case SSH2_MSG_KEXGSS_CONTINUE:
//.........这里部分代码省略.........

/*
 * Performs authentication of an incoming connection.  Session key has already
 * been exchanged and encryption is enabled.
 */
void
do_authentication(Authctxt *authctxt)
{
	u_int ulen;
	char *user, *style = NULL;

	/* Get the name of the user that we wish to log in as. */
	packet_read_expect(SSH_CMSG_USER);

	/* Get the user name. */
	user = packet_get_cstring(&ulen);
	packet_check_eom();

	if ((style = strchr(user, ':')) != NULL)
		*style++ = '\0';

	authctxt->user = user;
	authctxt->style = style;

	/* Verify that the user is a valid user. */
	if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
		authctxt->valid = 1;
	else {
		debug("do_authentication: invalid user %s", user);
		authctxt->pw = fakepw();
	}

	/* Configuration may have changed as a result of Match */
	if (options.num_auth_methods != 0)
		fatal("AuthenticationMethods is not supported with SSH "
		    "protocol 1");

	setproctitle("%s%s", authctxt->valid ? user : "unknown",
	    use_privsep ? " [net]" : "");

#ifdef USE_PAM
	if (options.use_pam)
		PRIVSEP(start_pam(authctxt));
#endif

	/*
	 * If we are not running as root, the user must have the same uid as
	 * the server.
	 */
#ifndef HAVE_CYGWIN
	if (!use_privsep && getuid() != 0 && authctxt->pw &&
	    authctxt->pw->pw_uid != getuid())
		packet_disconnect("Cannot change user when server not running as root.");
#endif

	/*
	 * Loop until the user has been authenticated or the connection is
	 * closed, do_authloop() returns only if authentication is successful
	 */
	do_authloop(authctxt);

	/* The user has been authenticated and accepted. */
	packet_start(SSH_SMSG_SUCCESS);
	packet_send();
	packet_write_wait();
}

void
kexdh_client(Kex *kex)
{
	BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
	DH *dh;
	Key *server_host_key;
	u_char *server_host_key_blob = NULL, *signature = NULL;
	u_char *kbuf, *hash;
	u_int klen, slen, sbloblen, hashlen;
	int kout;

	/* generate and send 'e', client DH public key */
	switch (kex->kex_type) {
	case KEX_DH_GRP1_SHA1:
		dh = dh_new_group1();
		break;
	case KEX_DH_GRP14_SHA1:
		dh = dh_new_group14();
		break;
	default:
		fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
	}
	dh_gen_key(dh, kex->we_need * 8);
	packet_start(SSH2_MSG_KEXDH_INIT);
	packet_put_bignum2(dh->pub_key);
	packet_send();

	debug("sending SSH2_MSG_KEXDH_INIT");
#ifdef DEBUG_KEXDH
	DHparams_print_fp(stderr, dh);
	fprintf(stderr, "pub= ");
	BN_print_fp(stderr, dh->pub_key);
	fprintf(stderr, "\n");
#endif

	debug("expecting SSH2_MSG_KEXDH_REPLY");
	packet_read_expect(SSH2_MSG_KEXDH_REPLY);

	/* key, cert */
	server_host_key_blob = packet_get_string(&sbloblen);
	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
	if (server_host_key == NULL)
		fatal("cannot decode server_host_key_blob");
	if (server_host_key->type != kex->hostkey_type)
		fatal("type mismatch for decoded server_host_key_blob");
	if (kex->verify_host_key == NULL)
		fatal("cannot verify server_host_key");
	if (kex->verify_host_key(server_host_key) == -1)
		fatal("server_host_key verification failed");

	/* DH parameter f, server public DH key */
	if ((dh_server_pub = BN_new()) == NULL)
		fatal("dh_server_pub == NULL");
	packet_get_bignum2(dh_server_pub);

#ifdef DEBUG_KEXDH
	fprintf(stderr, "dh_server_pub= ");
	BN_print_fp(stderr, dh_server_pub);
	fprintf(stderr, "\n");
	debug("bits %d", BN_num_bits(dh_server_pub));
#endif

	/* signed H */
	signature = packet_get_string(&slen);
	packet_check_eom();

	if (!dh_pub_is_valid(dh, dh_server_pub))
		packet_disconnect("bad server public DH value");

	klen = DH_size(dh);
	kbuf = xmalloc(klen);
	if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0)
		fatal("DH_compute_key: failed");
#ifdef DEBUG_KEXDH
	dump_digest("shared secret", kbuf, kout);
#endif
	if ((shared_secret = BN_new()) == NULL)
		fatal("kexdh_client: BN_new failed");
	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
		fatal("kexdh_client: BN_bin2bn failed");
	memset(kbuf, 0, klen);
	free(kbuf);

	/* calc and verify H */
	kex_dh_hash(
	    kex->client_version_string,
	    kex->server_version_string,
	    buffer_ptr(&kex->my), buffer_len(&kex->my),
	    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
	    server_host_key_blob, sbloblen,
	    dh->pub_key,
	    dh_server_pub,
	    shared_secret,
	    &hash, &hashlen
	);
	free(server_host_key_blob);
	BN_clear_free(dh_server_pub);
	DH_free(dh);

	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
//.........这里部分代码省略.........

void
userauth_finish(Authctxt *authctxt, int authenticated, const char *method,
    const char *submethod)
{
	char *methods;
	int partial = 0;

	if (!authctxt->valid && authenticated)
		fatal("INTERNAL ERROR: authenticated invalid user %s",
		    authctxt->user);
	if (authenticated && authctxt->postponed)
		fatal("INTERNAL ERROR: authenticated and postponed");

	/* Special handling for root */
	if (authenticated && authctxt->pw->pw_uid == 0 &&
	    !auth_root_allowed(method)) {
		authenticated = 0;
#ifdef SSH_AUDIT_EVENTS
		PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
#endif
	}

	if (authenticated && options.num_auth_methods != 0) {
		if (!auth2_update_methods_lists(authctxt, method, submethod)) {
			authenticated = 0;
			partial = 1;
		}
	}

	/* Log before sending the reply */
	auth_log(authctxt, authenticated, partial, method, submethod);

	if (authctxt->postponed)
		return;

#ifdef USE_PAM
	if (options.use_pam && authenticated) {
		if (!PRIVSEP(do_pam_account())) {
			/* if PAM returned a message, send it to the user */
			if (buffer_len(&loginmsg) > 0) {
				buffer_append(&loginmsg, "\0", 1);
				userauth_send_banner(buffer_ptr(&loginmsg));
				packet_write_wait();
			}
			fatal("Access denied for user %s by PAM account "
			    "configuration", authctxt->user);
		}
	}
#endif

#ifdef _UNICOS
	if (authenticated && cray_access_denied(authctxt->user)) {
		authenticated = 0;
		fatal("Access denied for user %s.", authctxt->user);
	}
#endif /* _UNICOS */

	if (authenticated == 1) {
		/* turn off userauth */
		dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
		packet_start(SSH2_MSG_USERAUTH_SUCCESS);
		packet_send();
		packet_write_wait();
		/* now we can break out */
		authctxt->success = 1;
	} else {

		/* Allow initial try of "none" auth without failure penalty */
		if (!authctxt->server_caused_failure &&
		    (authctxt->attempt > 1 || strcmp(method, "none") != 0))
			authctxt->failures++;
		if (authctxt->failures >= options.max_authtries) {
#ifdef SSH_AUDIT_EVENTS
			PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
#endif
			packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
		}
		methods = authmethods_get(authctxt);
		debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
		    partial, methods);
		packet_start(SSH2_MSG_USERAUTH_FAILURE);
		packet_put_cstring(methods);
		packet_put_char(partial);
		packet_send();
		packet_write_wait();
		free(methods);
	}
}