Vendor import of OpenSSH.

1 files changed, 1614 insertions, 0 deletions

diff --git a/crypto/openssh/channels.c b/crypto/openssh/channels.c
new file mode 100644
index 0000000..b40e965
--- /dev/null
+++ b/crypto/openssh/channels.c
@@ -0,0 +1,1614 @@
+/*
+ * 
+ * channels.c
+ * 
+ * Author: Tatu Ylonen <ylo@cs.hut.fi>
+ * 
+ * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+ *                    All rights reserved
+ * 
+ * Created: Fri Mar 24 16:35:24 1995 ylo
+ * 
+ * This file contains functions for generic socket connection forwarding.
+ * There is also code for initiating connection forwarding for X11 connections,
+ * arbitrary tcp/ip connections, and the authentication agent connection.
+ * 
+ */
+
+#include "includes.h"
+RCSID("$Id: channels.c,v 1.38 2000/01/24 20:37:29 markus Exp $");
+
+#include "ssh.h"
+#include "packet.h"
+#include "xmalloc.h"
+#include "buffer.h"
+#include "authfd.h"
+#include "uidswap.h"
+#include "readconf.h"
+#include "servconf.h"
+
+#include "channels.h"
+#include "nchan.h"
+#include "compat.h"
+
+/* Maximum number of fake X11 displays to try. */
+#define MAX_DISPLAYS  1000
+
+/* Max len of agent socket */
+#define MAX_SOCKET_NAME 100
+
+/*
+ * Pointer to an array containing all allocated channels.  The array is
+ * dynamically extended as needed.
+ */
+static Channel *channels = NULL;
+
+/*
+ * Size of the channel array.  All slots of the array must always be
+ * initialized (at least the type field); unused slots are marked with type
+ * SSH_CHANNEL_FREE.
+ */
+static int channels_alloc = 0;
+
+/*
+ * Maximum file descriptor value used in any of the channels.  This is
+ * updated in channel_allocate.
+ */
+static int channel_max_fd_value = 0;
+
+/* Name and directory of socket for authentication agent forwarding. */
+static char *channel_forwarded_auth_socket_name = NULL;
+static char *channel_forwarded_auth_socket_dir = NULL;
+
+/* Saved X11 authentication protocol name. */
+char *x11_saved_proto = NULL;
+
+/* Saved X11 authentication data.  This is the real data. */
+char *x11_saved_data = NULL;
+unsigned int x11_saved_data_len = 0;
+
+/*
+ * Fake X11 authentication data.  This is what the server will be sending us;
+ * we should replace any occurrences of this by the real data.
+ */
+char *x11_fake_data = NULL;
+unsigned int x11_fake_data_len;
+
+/*
+ * Data structure for storing which hosts are permitted for forward requests.
+ * The local sides of any remote forwards are stored in this array to prevent
+ * a corrupt remote server from accessing arbitrary TCP/IP ports on our local
+ * network (which might be behind a firewall).
+ */
+typedef struct {
+	char *host;		/* Host name. */
+	u_short port;		/* Port number. */
+} ForwardPermission;
+
+/* List of all permitted host/port pairs to connect. */
+static ForwardPermission permitted_opens[SSH_MAX_FORWARDS_PER_DIRECTION];
+/* Number of permitted host/port pairs in the array. */
+static int num_permitted_opens = 0;
+/*
+ * If this is true, all opens are permitted.  This is the case on the server
+ * on which we have to trust the client anyway, and the user could do
+ * anything after logging in anyway.
+ */
+static int all_opens_permitted = 0;
+
+/* This is set to true if both sides support SSH_PROTOFLAG_HOST_IN_FWD_OPEN. */
+static int have_hostname_in_open = 0;
+
+/* Sets specific protocol options. */
+
+void 
+channel_set_options(int hostname_in_open)
+{
+	have_hostname_in_open = hostname_in_open;
+}
+
+/*
+ * Permits opening to any host/port in SSH_MSG_PORT_OPEN.  This is usually
+ * called by the server, because the user could connect to any port anyway,
+ * and the server has no way to know but to trust the client anyway.
+ */
+
+void 
+channel_permit_all_opens()
+{
+	all_opens_permitted = 1;
+}
+
+/*
+ * Allocate a new channel object and set its type and socket. This will cause
+ * remote_name to be freed.
+ */
+
+int 
+channel_allocate(int type, int sock, char *remote_name)
+{
+	int i, found;
+	Channel *c;
+
+	/* Update the maximum file descriptor value. */
+	if (sock > channel_max_fd_value)
+		channel_max_fd_value = sock;
+	/* XXX set close-on-exec -markus */
+
+	/* Do initial allocation if this is the first call. */
+	if (channels_alloc == 0) {
+		channels_alloc = 10;
+		channels = xmalloc(channels_alloc * sizeof(Channel));
+		for (i = 0; i < channels_alloc; i++)
+			channels[i].type = SSH_CHANNEL_FREE;
+		/*
+		 * Kludge: arrange a call to channel_stop_listening if we
+		 * terminate with fatal().
+		 */
+		fatal_add_cleanup((void (*) (void *)) channel_stop_listening, NULL);
+	}
+	/* Try to find a free slot where to put the new channel. */
+	for (found = -1, i = 0; i < channels_alloc; i++)
+		if (channels[i].type == SSH_CHANNEL_FREE) {
+			/* Found a free slot. */
+			found = i;
+			break;
+		}
+	if (found == -1) {
+		/* There are no free slots.  Take last+1 slot and expand the array.  */
+		found = channels_alloc;
+		channels_alloc += 10;
+		debug("channel: expanding %d", channels_alloc);
+		channels = xrealloc(channels, channels_alloc * sizeof(Channel));
+		for (i = found; i < channels_alloc; i++)
+			channels[i].type = SSH_CHANNEL_FREE;
+	}
+	/* Initialize and return new channel number. */
+	c = &channels[found];
+	buffer_init(&c->input);
+	buffer_init(&c->output);
+	chan_init_iostates(c);
+	c->self = found;
+	c->type = type;
+	c->sock = sock;
+	c->remote_id = -1;
+	c->remote_name = remote_name;
+	debug("channel %d: new [%s]", found, remote_name);
+	return found;
+}
+
+/* Free the channel and close its socket. */
+
+void 
+channel_free(int channel)
+{
+	if (channel < 0 || channel >= channels_alloc ||
+	    channels[channel].type == SSH_CHANNEL_FREE)
+		packet_disconnect("channel free: bad local channel %d", channel);
+
+	if (compat13)
+		shutdown(channels[channel].sock, SHUT_RDWR);
+	close(channels[channel].sock);
+	buffer_free(&channels[channel].input);
+	buffer_free(&channels[channel].output);
+	channels[channel].type = SSH_CHANNEL_FREE;
+	if (channels[channel].remote_name) {
+		xfree(channels[channel].remote_name);
+		channels[channel].remote_name = NULL;
+	}
+}
+
+/*
+ * This is called just before select() to add any bits relevant to channels
+ * in the select bitmasks.
+ */
+
+void 
+channel_prepare_select(fd_set * readset, fd_set * writeset)
+{
+	int i;
+	Channel *ch;
+	unsigned char *ucp;
+	unsigned int proto_len, data_len;
+
+	for (i = 0; i < channels_alloc; i++) {
+		ch = &channels[i];
+redo:
+		switch (ch->type) {
+		case SSH_CHANNEL_X11_LISTENER:
+		case SSH_CHANNEL_PORT_LISTENER:
+		case SSH_CHANNEL_AUTH_SOCKET:
+			FD_SET(ch->sock, readset);
+			break;
+
+		case SSH_CHANNEL_OPEN:
+			if (compat13) {
+				if (buffer_len(&ch->input) < packet_get_maxsize())
+					FD_SET(ch->sock, readset);
+				if (buffer_len(&ch->output) > 0)
+					FD_SET(ch->sock, writeset);
+				break;
+			}
+			/* test whether sockets are 'alive' for read/write */
+			if (ch->istate == CHAN_INPUT_OPEN)
+				if (buffer_len(&ch->input) < packet_get_maxsize())
+					FD_SET(ch->sock, readset);
+			if (ch->ostate == CHAN_OUTPUT_OPEN ||
+			    ch->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
+				if (buffer_len(&ch->output) > 0) {
+					FD_SET(ch->sock, writeset);
+				} else if (ch->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
+					chan_obuf_empty(ch);
+				}
+			}
+			break;
+
+		case SSH_CHANNEL_INPUT_DRAINING:
+			if (!compat13)
+				fatal("cannot happen: IN_DRAIN");
+			if (buffer_len(&ch->input) == 0) {
+				packet_start(SSH_MSG_CHANNEL_CLOSE);
+				packet_put_int(ch->remote_id);
+				packet_send();
+				ch->type = SSH_CHANNEL_CLOSED;
+				debug("Closing channel %d after input drain.", ch->self);
+				break;
+			}
+			break;
+
+		case SSH_CHANNEL_OUTPUT_DRAINING:
+			if (!compat13)
+				fatal("cannot happen: OUT_DRAIN");
+			if (buffer_len(&ch->output) == 0) {
+				channel_free(i);
+				break;
+			}
+			FD_SET(ch->sock, writeset);
+			break;
+
+		case SSH_CHANNEL_X11_OPEN:
+			/*
+			 * This is a special state for X11 authentication
+			 * spoofing.  An opened X11 connection (when
+			 * authentication spoofing is being done) remains in
+			 * this state until the first packet has been
+			 * completely read.  The authentication data in that
+			 * packet is then substituted by the real data if it
+			 * matches the fake data, and the channel is put into
+			 * normal mode.
+			 */
+			/* Check if the fixed size part of the packet is in buffer. */
+			if (buffer_len(&ch->output) < 12)
+				break;
+
+			/* Parse the lengths of variable-length fields. */
+			ucp = (unsigned char *) buffer_ptr(&ch->output);
+			if (ucp[0] == 0x42) {	/* Byte order MSB first. */
+				proto_len = 256 * ucp[6] + ucp[7];
+				data_len = 256 * ucp[8] + ucp[9];
+			} else if (ucp[0] == 0x6c) {	/* Byte order LSB first. */
+				proto_len = ucp[6] + 256 * ucp[7];
+				data_len = ucp[8] + 256 * ucp[9];
+			} else {
+				debug("Initial X11 packet contains bad byte order byte: 0x%x",
+				      ucp[0]);
+				ch->type = SSH_CHANNEL_OPEN;
+				goto reject;
+			}
+
+			/* Check if the whole packet is in buffer. */
+			if (buffer_len(&ch->output) <
+			    12 + ((proto_len + 3) & ~3) + ((data_len + 3) & ~3))
+				break;
+
+			/* Check if authentication protocol matches. */
+			if (proto_len != strlen(x11_saved_proto) ||
+			    memcmp(ucp + 12, x11_saved_proto, proto_len) != 0) {
+				debug("X11 connection uses different authentication protocol.");
+				ch->type = SSH_CHANNEL_OPEN;
+				goto reject;
+			}
+			/* Check if authentication data matches our fake data. */
+			if (data_len != x11_fake_data_len ||
+			    memcmp(ucp + 12 + ((proto_len + 3) & ~3),
+				x11_fake_data, x11_fake_data_len) != 0) {
+				debug("X11 auth data does not match fake data.");
+				ch->type = SSH_CHANNEL_OPEN;
+				goto reject;
+			}
+			/* Check fake data length */
+			if (x11_fake_data_len != x11_saved_data_len) {
+				error("X11 fake_data_len %d != saved_data_len %d",
+				  x11_fake_data_len, x11_saved_data_len);
+				ch->type = SSH_CHANNEL_OPEN;
+				goto reject;
+			}
+			/*
+			 * Received authentication protocol and data match
+			 * our fake data. Substitute the fake data with real
+			 * data.
+			 */
+			memcpy(ucp + 12 + ((proto_len + 3) & ~3),
+			       x11_saved_data, x11_saved_data_len);
+
+			/* Start normal processing for the channel. */
+			ch->type = SSH_CHANNEL_OPEN;
+			goto redo;
+
+	reject:
+			/*
+			 * We have received an X11 connection that has bad
+			 * authentication information.
+			 */
+			log("X11 connection rejected because of wrong authentication.\r\n");
+			buffer_clear(&ch->input);
+			buffer_clear(&ch->output);
+			if (compat13) {
+				close(ch->sock);
+				ch->sock = -1;
+				ch->type = SSH_CHANNEL_CLOSED;
+				packet_start(SSH_MSG_CHANNEL_CLOSE);
+				packet_put_int(ch->remote_id);
+				packet_send();
+			} else {
+				debug("X11 rejected %d i%d/o%d", ch->self, ch->istate, ch->ostate);
+				chan_read_failed(ch);
+				chan_write_failed(ch);
+				debug("X11 rejected %d i%d/o%d", ch->self, ch->istate, ch->ostate);
+			}
+			break;
+
+		case SSH_CHANNEL_FREE:
+		default:
+			continue;
+		}
+	}
+}
+
+/*
+ * After select, perform any appropriate operations for channels which have
+ * events pending.
+ */
+
+void 
+channel_after_select(fd_set * readset, fd_set * writeset)
+{
+	struct sockaddr addr;
+	int newsock, i, newch, len;
+	socklen_t addrlen;
+	Channel *ch;
+	char buf[16384], *remote_hostname;
+
+	/* Loop over all channels... */
+	for (i = 0; i < channels_alloc; i++) {
+		ch = &channels[i];
+		switch (ch->type) {
+		case SSH_CHANNEL_X11_LISTENER:
+			/* This is our fake X11 server socket. */
+			if (FD_ISSET(ch->sock, readset)) {
+				debug("X11 connection requested.");
+				addrlen = sizeof(addr);
+				newsock = accept(ch->sock, &addr, &addrlen);
+				if (newsock < 0) {
+					error("accept: %.100s", strerror(errno));
+					break;
+				}
+				remote_hostname = get_remote_hostname(newsock);
+				snprintf(buf, sizeof buf, "X11 connection from %.200s port %d",
+				remote_hostname, get_peer_port(newsock));
+				xfree(remote_hostname);
+				newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
+							 xstrdup(buf));
+				packet_start(SSH_SMSG_X11_OPEN);
+				packet_put_int(newch);
+				if (have_hostname_in_open)
+					packet_put_string(buf, strlen(buf));
+				packet_send();
+			}
+			break;
+
+		case SSH_CHANNEL_PORT_LISTENER:
+			/*
+			 * This socket is listening for connections to a
+			 * forwarded TCP/IP port.
+			 */
+			if (FD_ISSET(ch->sock, readset)) {
+				debug("Connection to port %d forwarding to %.100s port %d requested.",
+				      ch->listening_port, ch->path, ch->host_port);
+				addrlen = sizeof(addr);
+				newsock = accept(ch->sock, &addr, &addrlen);
+				if (newsock < 0) {
+					error("accept: %.100s", strerror(errno));
+					break;
+				}
+				remote_hostname = get_remote_hostname(newsock);
+				snprintf(buf, sizeof buf, "listen port %d for %.100s port %d, connect from %.200s port %d",
+					 ch->listening_port, ch->path, ch->host_port,
+				remote_hostname, get_peer_port(newsock));
+				xfree(remote_hostname);
+				newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
+							 xstrdup(buf));
+				packet_start(SSH_MSG_PORT_OPEN);
+				packet_put_int(newch);
+				packet_put_string(ch->path, strlen(ch->path));
+				packet_put_int(ch->host_port);
+				if (have_hostname_in_open)
+					packet_put_string(buf, strlen(buf));
+				packet_send();
+			}
+			break;
+
+		case SSH_CHANNEL_AUTH_SOCKET:
+			/*
+			 * This is the authentication agent socket listening
+			 * for connections from clients.
+			 */
+			if (FD_ISSET(ch->sock, readset)) {
+				addrlen = sizeof(addr);
+				newsock = accept(ch->sock, &addr, &addrlen);
+				if (newsock < 0) {
+					error("accept from auth socket: %.100s", strerror(errno));
+					break;
+				}
+				newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
+					xstrdup("accepted auth socket"));
+				packet_start(SSH_SMSG_AGENT_OPEN);
+				packet_put_int(newch);
+				packet_send();
+			}
+			break;
+
+		case SSH_CHANNEL_OPEN:
+			/*
+			 * This is an open two-way communication channel. It
+			 * is not of interest to us at this point what kind
+			 * of data is being transmitted.
+			 */
+
+			/*
+			 * Read available incoming data and append it to
+			 * buffer; shutdown socket, if read or write failes
+			 */
+			if (FD_ISSET(ch->sock, readset)) {
+				len = read(ch->sock, buf, sizeof(buf));
+				if (len <= 0) {
+					if (compat13) {
+						buffer_consume(&ch->output, buffer_len(&ch->output));
+						ch->type = SSH_CHANNEL_INPUT_DRAINING;
+						debug("Channel %d status set to input draining.", i);
+					} else {
+						chan_read_failed(ch);
+					}
+					break;
+				}
+				buffer_append(&ch->input, buf, len);
+			}
+			/* Send buffered output data to the socket. */
+			if (FD_ISSET(ch->sock, writeset) && buffer_len(&ch->output) > 0) {
+				len = write(ch->sock, buffer_ptr(&ch->output),
+					    buffer_len(&ch->output));
+				if (len <= 0) {
+					if (compat13) {
+						buffer_consume(&ch->output, buffer_len(&ch->output));
+						debug("Channel %d status set to input draining.", i);
+						ch->type = SSH_CHANNEL_INPUT_DRAINING;
+					} else {
+						chan_write_failed(ch);
+					}
+					break;
+				}
+				buffer_consume(&ch->output, len);
+			}
+			break;
+
+		case SSH_CHANNEL_OUTPUT_DRAINING:
+			if (!compat13)
+				fatal("cannot happen: OUT_DRAIN");
+			/* Send buffered output data to the socket. */
+			if (FD_ISSET(ch->sock, writeset) && buffer_len(&ch->output) > 0) {
+				len = write(ch->sock, buffer_ptr(&ch->output),
+					    buffer_len(&ch->output));
+				if (len <= 0)
+					buffer_consume(&ch->output, buffer_len(&ch->output));
+				else
+					buffer_consume(&ch->output, len);
+			}
+			break;
+
+		case SSH_CHANNEL_X11_OPEN:
+		case SSH_CHANNEL_FREE:
+		default:
+			continue;
+		}
+	}
+}
+
+/* If there is data to send to the connection, send some of it now. */
+
+void 
+channel_output_poll()
+{
+	int len, i;
+	Channel *ch;
+
+	for (i = 0; i < channels_alloc; i++) {
+		ch = &channels[i];
+
+		/* We are only interested in channels that can have buffered incoming data. */
+		if (compat13) {
+			if (ch->type != SSH_CHANNEL_OPEN &&
+			    ch->type != SSH_CHANNEL_INPUT_DRAINING)
+				continue;
+		} else {
+			if (ch->type != SSH_CHANNEL_OPEN)
+				continue;
+			if (ch->istate != CHAN_INPUT_OPEN &&
+			    ch->istate != CHAN_INPUT_WAIT_DRAIN)
+				continue;
+		}
+
+		/* Get the amount of buffered data for this channel. */
+		len = buffer_len(&ch->input);
+		if (len > 0) {
+			/* Send some data for the other side over the secure connection. */
+			if (packet_is_interactive()) {
+				if (len > 1024)
+					len = 512;
+			} else {
+				/* Keep the packets at reasonable size. */
+				if (len > packet_get_maxsize()/2)
+					len = packet_get_maxsize()/2;
+			}
+			packet_start(SSH_MSG_CHANNEL_DATA);
+			packet_put_int(ch->remote_id);
+			packet_put_string(buffer_ptr(&ch->input), len);
+			packet_send();
+			buffer_consume(&ch->input, len);
+		} else if (ch->istate == CHAN_INPUT_WAIT_DRAIN) {
+			if (compat13)
+				fatal("cannot happen: istate == INPUT_WAIT_DRAIN for proto 1.3");
+			/*
+			 * input-buffer is empty and read-socket shutdown:
+			 * tell peer, that we will not send more data: send IEOF
+			 */
+			chan_ibuf_empty(ch);
+		}
+	}
+}
+
+/*
+ * This is called when a packet of type CHANNEL_DATA has just been received.
+ * The message type has already been consumed, but channel number and data is
+ * still there.
+ */
+
+void 
+channel_input_data(int payload_len)
+{
+	int id;
+	char *data;
+	unsigned int data_len;
+	Channel *ch;
+
+	/* Get the channel number and verify it. */
+	id = packet_get_int();
+	if (id < 0 || id >= channels_alloc)
+		packet_disconnect("Received data for nonexistent channel %d.", id);
+	ch = &channels[id];
+
+	if (ch->type == SSH_CHANNEL_FREE)
+		packet_disconnect("Received data for free channel %d.", ch->self);
+
+	/* Ignore any data for non-open channels (might happen on close) */
+	if (ch->type != SSH_CHANNEL_OPEN &&
+	    ch->type != SSH_CHANNEL_X11_OPEN)
+		return;
+
+	/* same for protocol 1.5 if output end is no longer open */
+	if (!compat13 && ch->ostate != CHAN_OUTPUT_OPEN)
+		return;
+
+	/* Get the data. */
+	data = packet_get_string(&data_len);
+	packet_integrity_check(payload_len, 4 + 4 + data_len, SSH_MSG_CHANNEL_DATA);
+	buffer_append(&ch->output, data, data_len);
+	xfree(data);
+}
+
+/*
+ * Returns true if no channel has too much buffered data, and false if one or
+ * more channel is overfull.
+ */
+
+int 
+channel_not_very_much_buffered_data()
+{
+	unsigned int i;
+	Channel *ch;
+
+	for (i = 0; i < channels_alloc; i++) {
+		ch = &channels[i];
+		if (ch->type == SSH_CHANNEL_OPEN) {
+			if (buffer_len(&ch->input) > packet_get_maxsize())
+				return 0;
+			if (buffer_len(&ch->output) > packet_get_maxsize())
+				return 0;
+		}
+	}
+	return 1;
+}
+
+/* This is called after receiving CHANNEL_CLOSE/IEOF. */
+
+void 
+channel_input_close()
+{
+	int channel;
+
+	/* Get the channel number and verify it. */
+	channel = packet_get_int();
+	if (channel < 0 || channel >= channels_alloc ||
+	    channels[channel].type == SSH_CHANNEL_FREE)
+		packet_disconnect("Received data for nonexistent channel %d.", channel);
+
+	if (!compat13) {
+		/* proto version 1.5 overloads CLOSE with IEOF */
+		chan_rcvd_ieof(&channels[channel]);
+		return;
+	}
+
+	/*
+	 * Send a confirmation that we have closed the channel and no more
+	 * data is coming for it.
+	 */
+	packet_start(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION);
+	packet_put_int(channels[channel].remote_id);
+	packet_send();
+
+	/*
+	 * If the channel is in closed state, we have sent a close request,
+	 * and the other side will eventually respond with a confirmation.
+	 * Thus, we cannot free the channel here, because then there would be
+	 * no-one to receive the confirmation.  The channel gets freed when
+	 * the confirmation arrives.
+	 */
+	if (channels[channel].type != SSH_CHANNEL_CLOSED) {
+		/*
+		 * Not a closed channel - mark it as draining, which will
+		 * cause it to be freed later.
+		 */
+		buffer_consume(&channels[channel].input,
+			       buffer_len(&channels[channel].input));
+		channels[channel].type = SSH_CHANNEL_OUTPUT_DRAINING;
+	}
+}
+
+/* This is called after receiving CHANNEL_CLOSE_CONFIRMATION/OCLOSE. */
+
+void 
+channel_input_close_confirmation()
+{
+	int channel;
+
+	/* Get the channel number and verify it. */
+	channel = packet_get_int();
+	if (channel < 0 || channel >= channels_alloc)
+		packet_disconnect("Received close confirmation for out-of-range channel %d.",
+				  channel);
+
+	if (!compat13) {
+		/* proto version 1.5 overloads CLOSE_CONFIRMATION with OCLOSE */
+		chan_rcvd_oclose(&channels[channel]);
+		return;
+	}
+	if (channels[channel].type != SSH_CHANNEL_CLOSED)
+		packet_disconnect("Received close confirmation for non-closed channel %d (type %d).",
+				  channel, channels[channel].type);
+
+	/* Free the channel. */
+	channel_free(channel);
+}
+
+/* This is called after receiving CHANNEL_OPEN_CONFIRMATION. */
+
+void 
+channel_input_open_confirmation()
+{
+	int channel, remote_channel;
+
+	/* Get the channel number and verify it. */
+	channel = packet_get_int();
+	if (channel < 0 || channel >= channels_alloc ||
+	    channels[channel].type != SSH_CHANNEL_OPENING)
+		packet_disconnect("Received open confirmation for non-opening channel %d.",
+				  channel);
+
+	/* Get remote side's id for this channel. */
+	remote_channel = packet_get_int();
+
+	/* Record the remote channel number and mark that the channel is now open. */
+	channels[channel].remote_id = remote_channel;
+	channels[channel].type = SSH_CHANNEL_OPEN;
+}
+
+/* This is called after receiving CHANNEL_OPEN_FAILURE from the other side. */
+
+void 
+channel_input_open_failure()
+{
+	int channel;
+
+	/* Get the channel number and verify it. */
+	channel = packet_get_int();
+	if (channel < 0 || channel >= channels_alloc ||
+	    channels[channel].type != SSH_CHANNEL_OPENING)
+		packet_disconnect("Received open failure for non-opening channel %d.",
+				  channel);
+
+	/* Free the channel.  This will also close the socket. */
+	channel_free(channel);
+}
+
+/*
+ * Stops listening for channels, and removes any unix domain sockets that we
+ * might have.
+ */
+
+void 
+channel_stop_listening()
+{
+	int i;
+	for (i = 0; i < channels_alloc; i++) {
+		switch (channels[i].type) {
+		case SSH_CHANNEL_AUTH_SOCKET:
+			close(channels[i].sock);
+			remove(channels[i].path);
+			channel_free(i);
+			break;
+		case SSH_CHANNEL_PORT_LISTENER:
+		case SSH_CHANNEL_X11_LISTENER:
+			close(channels[i].sock);
+			channel_free(i);
+			break;
+		default:
+			break;
+		}
+	}
+}
+
+/*
+ * Closes the sockets of all channels.  This is used to close extra file
+ * descriptors after a fork.
+ */
+
+void 
+channel_close_all()
+{
+	int i;
+	for (i = 0; i < channels_alloc; i++) {
+		if (channels[i].type != SSH_CHANNEL_FREE)
+			close(channels[i].sock);
+	}
+}
+
+/* Returns the maximum file descriptor number used by the channels. */
+
+int 
+channel_max_fd()
+{
+	return channel_max_fd_value;
+}
+
+/* Returns true if any channel is still open. */
+
+int 
+channel_still_open()
+{
+	unsigned int i;
+	for (i = 0; i < channels_alloc; i++)
+		switch (channels[i].type) {
+		case SSH_CHANNEL_FREE:
+		case SSH_CHANNEL_X11_LISTENER:
+		case SSH_CHANNEL_PORT_LISTENER:
+		case SSH_CHANNEL_CLOSED:
+		case SSH_CHANNEL_AUTH_SOCKET:
+			continue;
+		case SSH_CHANNEL_OPENING:
+		case SSH_CHANNEL_OPEN:
+		case SSH_CHANNEL_X11_OPEN:
+			return 1;
+		case SSH_CHANNEL_INPUT_DRAINING:
+		case SSH_CHANNEL_OUTPUT_DRAINING:
+			if (!compat13)
+				fatal("cannot happen: OUT_DRAIN");
+			return 1;
+		default:
+			fatal("channel_still_open: bad channel type %d", channels[i].type);
+			/* NOTREACHED */
+		}
+	return 0;
+}
+
+/*
+ * Returns a message describing the currently open forwarded connections,
+ * suitable for sending to the client.  The message contains crlf pairs for
+ * newlines.
+ */
+
+char *
+channel_open_message()
+{
+	Buffer buffer;
+	int i;
+	char buf[512], *cp;
+
+	buffer_init(&buffer);
+	snprintf(buf, sizeof buf, "The following connections are open:\r\n");
+	buffer_append(&buffer, buf, strlen(buf));
+	for (i = 0; i < channels_alloc; i++) {
+		Channel *c = &channels[i];
+		switch (c->type) {
+		case SSH_CHANNEL_FREE:
+		case SSH_CHANNEL_X11_LISTENER:
+		case SSH_CHANNEL_PORT_LISTENER:
+		case SSH_CHANNEL_CLOSED:
+		case SSH_CHANNEL_AUTH_SOCKET:
+			continue;
+		case SSH_CHANNEL_OPENING:
+		case SSH_CHANNEL_OPEN:
+		case SSH_CHANNEL_X11_OPEN:
+		case SSH_CHANNEL_INPUT_DRAINING:
+		case SSH_CHANNEL_OUTPUT_DRAINING:
+			snprintf(buf, sizeof buf, "  #%d %.300s (t%d r%d i%d/%d o%d/%d)\r\n",
+			    c->self, c->remote_name,
+			    c->type, c->remote_id,
+			    c->istate, buffer_len(&c->input),
+			    c->ostate, buffer_len(&c->output));
+			buffer_append(&buffer, buf, strlen(buf));
+			continue;
+		default:
+			fatal("channel_still_open: bad channel type %d", c->type);
+			/* NOTREACHED */
+		}
+	}
+	buffer_append(&buffer, "\0", 1);
+	cp = xstrdup(buffer_ptr(&buffer));
+	buffer_free(&buffer);
+	return cp;
+}
+
+/*
+ * Initiate forwarding of connections to local port "port" through the secure
+ * channel to host:port from remote side.
+ */
+
+void 
+channel_request_local_forwarding(u_short port, const char *host,
+				 u_short host_port, int gateway_ports)
+{
+	int success, ch, sock, on = 1;
+	struct addrinfo hints, *ai, *aitop;
+	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
+	struct linger linger;
+
+	if (strlen(host) > sizeof(channels[0].path) - 1)
+		packet_disconnect("Forward host name too long.");
+
+	/*
+	 * getaddrinfo returns a loopback address if the hostname is
+	 * set to NULL and hints.ai_flags is not AI_PASSIVE
+	 */
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = IPv4or6;
+	hints.ai_flags = gateway_ports ? AI_PASSIVE : 0;
+	hints.ai_socktype = SOCK_STREAM;
+	snprintf(strport, sizeof strport, "%d", port);
+	if (getaddrinfo(NULL, strport, &hints, &aitop) != 0)
+		packet_disconnect("getaddrinfo: fatal error");
+
+	success = 0;
+	for (ai = aitop; ai; ai = ai->ai_next) {
+		if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
+			continue;
+		if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop, sizeof(ntop),
+		    strport, sizeof(strport), NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
+			error("channel_request_local_forwarding: getnameinfo failed");
+			continue;
+		}
+		/* Create a port to listen for the host. */
+		sock = socket(ai->ai_family, SOCK_STREAM, 0);
+		if (sock < 0) {
+			/* this is no error since kernel may not support ipv6 */
+			verbose("socket: %.100s", strerror(errno));
+			continue;
+		}
+		/*
+		 * Set socket options.  We would like the socket to disappear
+		 * as soon as it has been closed for whatever reason.
+		 */
+		setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on));
+		linger.l_onoff = 1;
+		linger.l_linger = 5;
+		setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger));
+		debug("Local forwarding listening on %s port %s.", ntop, strport);
+
+		/* Bind the socket to the address. */
+		if (bind(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
+			/* address can be in use ipv6 address is already bound */
+			verbose("bind: %.100s", strerror(errno));
+			close(sock);
+			continue;
+		}
+		/* Start listening for connections on the socket. */
+		if (listen(sock, 5) < 0) {
+			error("listen: %.100s", strerror(errno));
+			close(sock);
+			continue;
+		}
+		/* Allocate a channel number for the socket. */
+		ch = channel_allocate(SSH_CHANNEL_PORT_LISTENER, sock,
+		    xstrdup("port listener"));
+		strlcpy(channels[ch].path, host, sizeof(channels[ch].path));
+		channels[ch].host_port = host_port;
+		channels[ch].listening_port = port;
+		success = 1;
+	}
+	if (success == 0)
+		packet_disconnect("cannot listen port: %d", port);
+	freeaddrinfo(aitop);
+}
+
+/*
+ * Initiate forwarding of connections to port "port" on remote host through
+ * the secure channel to host:port from local side.
+ */
+
+void 
+channel_request_remote_forwarding(u_short port, const char *host,
+				  u_short remote_port)
+{
+	int payload_len;
+	/* Record locally that connection to this host/port is permitted. */
+	if (num_permitted_opens >= SSH_MAX_FORWARDS_PER_DIRECTION)
+		fatal("channel_request_remote_forwarding: too many forwards");
+
+	permitted_opens[num_permitted_opens].host = xstrdup(host);
+	permitted_opens[num_permitted_opens].port = remote_port;
+	num_permitted_opens++;
+
+	/* Send the forward request to the remote side. */
+	packet_start(SSH_CMSG_PORT_FORWARD_REQUEST);
+	packet_put_int(port);
+	packet_put_string(host, strlen(host));
+	packet_put_int(remote_port);
+	packet_send();
+	packet_write_wait();
+
+	/*
+	 * Wait for response from the remote side.  It will send a disconnect
+	 * message on failure, and we will never see it here.
+	 */
+	packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
+}
+
+/*
+ * This is called after receiving CHANNEL_FORWARDING_REQUEST.  This initates
+ * listening for the port, and sends back a success reply (or disconnect
+ * message if there was an error).  This never returns if there was an error.
+ */
+
+void 
+channel_input_port_forward_request(int is_root)
+{
+	u_short port, host_port;
+	char *hostname;
+
+	/* Get arguments from the packet. */
+	port = packet_get_int();
+	hostname = packet_get_string(NULL);
+	host_port = packet_get_int();
+
+	/*
+	 * Check that an unprivileged user is not trying to forward a
+	 * privileged port.
+	 */
+	if (port < IPPORT_RESERVED && !is_root)
+		packet_disconnect("Requested forwarding of port %d but user is not root.",
+				  port);
+	/*
+	 * Initiate forwarding,
+	 * bind port to localhost only (gateway ports == 0).
+	 */
+	channel_request_local_forwarding(port, hostname, host_port, 0);
+
+	/* Free the argument string. */
+	xfree(hostname);
+}
+
+/*
+ * This is called after receiving PORT_OPEN message.  This attempts to
+ * connect to the given host:port, and sends back CHANNEL_OPEN_CONFIRMATION
+ * or CHANNEL_OPEN_FAILURE.
+ */
+
+void 
+channel_input_port_open(int payload_len)
+{
+	int remote_channel, sock = 0, newch, i;
+	u_short host_port;
+	char *host, *originator_string;
+	int host_len, originator_len;
+	struct addrinfo hints, *ai, *aitop;
+	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
+	int gaierr;
+
+	/* Get remote channel number. */
+	remote_channel = packet_get_int();
+
+	/* Get host name to connect to. */
+	host = packet_get_string(&host_len);
+
+	/* Get port to connect to. */
+	host_port = packet_get_int();
+
+	/* Get remote originator name. */
+	if (have_hostname_in_open) {
+		originator_string = packet_get_string(&originator_len);
+		originator_len += 4;	/* size of packet_int */
+	} else {
+		originator_string = xstrdup("unknown (remote did not supply name)");
+		originator_len = 0;	/* no originator supplied */
+	}
+
+	packet_integrity_check(payload_len,
+			       4 + 4 + host_len + 4 + originator_len,
+			       SSH_MSG_PORT_OPEN);
+
+	/* Check if opening that port is permitted. */
+	if (!all_opens_permitted) {
+		/* Go trough all permitted ports. */
+		for (i = 0; i < num_permitted_opens; i++)
+			if (permitted_opens[i].port == host_port &&
+			    strcmp(permitted_opens[i].host, host) == 0)
+				break;
+
+		/* Check if we found the requested port among those permitted. */
+		if (i >= num_permitted_opens) {
+			/* The port is not permitted. */
+			log("Received request to connect to %.100s:%d, but the request was denied.",
+			    host, host_port);
+			goto fail;
+		}
+	}
+
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = IPv4or6;
+	hints.ai_socktype = SOCK_STREAM;
+	snprintf(strport, sizeof strport, "%d", host_port);
+	if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) {
+		error("%.100s: unknown host (%s)", host, gai_strerror(gaierr));
+		goto fail;
+	}
+
+	for (ai = aitop; ai; ai = ai->ai_next) {
+		if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
+			continue;
+		if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop, sizeof(ntop),
+		    strport, sizeof(strport), NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
+			error("channel_input_port_open: getnameinfo failed");
+			continue;
+		}
+		/* Create the socket. */
+		sock = socket(ai->ai_family, SOCK_STREAM, 0);
+		if (sock < 0) {
+			error("socket: %.100s", strerror(errno));
+			continue;
+		}
+		/* Connect to the host/port. */
+		if (connect(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
+			error("connect %.100s port %s: %.100s", ntop, strport,
+			    strerror(errno));
+			close(sock);
+			continue;	/* fail -- try next */	
+		}
+		break; /* success */
+
+	}
+	freeaddrinfo(aitop);
+
+	if (!ai) {
+		error("connect %.100s port %d: failed.", host, host_port);	
+		goto fail;
+	}
+
+	/* Successful connection. */
+
+	/* Allocate a channel for this connection. */
+	newch = channel_allocate(SSH_CHANNEL_OPEN, sock, originator_string);
+	channels[newch].remote_id = remote_channel;
+
+	/* Send a confirmation to the remote host. */
+	packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
+	packet_put_int(remote_channel);
+	packet_put_int(newch);
+	packet_send();
+
+	/* Free the argument string. */
+	xfree(host);
+
+	return;
+
+fail:
+	/* Free the argument string. */
+	xfree(host);
+
+	/* Send refusal to the remote host. */
+	packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
+	packet_put_int(remote_channel);
+	packet_send();
+}
+
+/*
+ * Creates an internet domain socket for listening for X11 connections.
+ * Returns a suitable value for the DISPLAY variable, or NULL if an error
+ * occurs.
+ */
+
+#define	NUM_SOCKS	10
+
+char *
+x11_create_display_inet(int screen_number, int x11_display_offset)
+{
+	int display_number, sock;
+	u_short port;
+	struct addrinfo hints, *ai, *aitop;
+	char strport[NI_MAXSERV];
+	int gaierr, n, num_socks = 0, socks[NUM_SOCKS];
+	char display[512];
+	char hostname[MAXHOSTNAMELEN];
+
+	for (display_number = x11_display_offset;
+	     display_number < MAX_DISPLAYS;
+	     display_number++) {
+		port = 6000 + display_number;
+		memset(&hints, 0, sizeof(hints));
+		hints.ai_family = IPv4or6;
+		hints.ai_flags = AI_PASSIVE;		/* XXX loopback only ? */
+		hints.ai_socktype = SOCK_STREAM;
+		snprintf(strport, sizeof strport, "%d", port);
+		if ((gaierr = getaddrinfo(NULL, strport, &hints, &aitop)) != 0) {
+			error("getaddrinfo: %.100s", gai_strerror(gaierr));
+			return NULL;
+		}
+		for (ai = aitop; ai; ai = ai->ai_next) {
+			if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
+				continue;
+			sock = socket(ai->ai_family, SOCK_STREAM, 0);
+			if (sock < 0) {
+				error("socket: %.100s", strerror(errno));
+				return NULL;
+			}
+			if (bind(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
+				debug("bind port %d: %.100s", port, strerror(errno));
+				shutdown(sock, SHUT_RDWR);
+				close(sock);
+				for (n = 0; n < num_socks; n++) {
+					shutdown(socks[n], SHUT_RDWR);
+					close(socks[n]);
+				}
+				num_socks = 0;
+				break;
+			}
+			socks[num_socks++] = sock;
+			if (num_socks == NUM_SOCKS)
+				break;
+		}
+		if (num_socks > 0)
+			break;
+	}
+	if (display_number >= MAX_DISPLAYS) {
+		error("Failed to allocate internet-domain X11 display socket.");
+		return NULL;
+	}
+	/* Start listening for connections on the socket. */
+	for (n = 0; n < num_socks; n++) {
+		sock = socks[n];
+		if (listen(sock, 5) < 0) {
+			error("listen: %.100s", strerror(errno));
+			shutdown(sock, SHUT_RDWR);
+			close(sock);
+			return NULL;
+		}
+	}
+
+	/* Set up a suitable value for the DISPLAY variable. */
+	if (gethostname(hostname, sizeof(hostname)) < 0)
+		fatal("gethostname: %.100s", strerror(errno));
+	snprintf(display, sizeof display, "%.400s:%d.%d", hostname,
+		 display_number, screen_number);
+
+	/* Allocate a channel for each socket. */
+	for (n = 0; n < num_socks; n++) {
+		sock = socks[n];
+		(void) channel_allocate(SSH_CHANNEL_X11_LISTENER, sock,
+					xstrdup("X11 inet listener"));
+	}
+
+	/* Return a suitable value for the DISPLAY environment variable. */
+	return xstrdup(display);
+}
+
+#ifndef X_UNIX_PATH
+#define X_UNIX_PATH "/tmp/.X11-unix/X"
+#endif
+
+static
+int
+connect_local_xsocket(unsigned int dnr)
+{
+	static const char *const x_sockets[] = {
+		X_UNIX_PATH "%u",
+		"/var/X/.X11-unix/X" "%u",
+		"/usr/spool/sockets/X11/" "%u",
+		NULL
+	};
+	int sock;
+	struct sockaddr_un addr;
+	const char *const * path;
+
+	for (path = x_sockets; *path; ++path) {
+		sock = socket(AF_UNIX, SOCK_STREAM, 0);
+		if (sock < 0)
+			error("socket: %.100s", strerror(errno));
+		memset(&addr, 0, sizeof(addr));
+		addr.sun_family = AF_UNIX;
+		snprintf(addr.sun_path, sizeof addr.sun_path, *path, dnr);
+		if (connect(sock, (struct sockaddr *) & addr, sizeof(addr)) == 0)
+			return sock;
+		close(sock);
+	}
+	error("connect %.100s: %.100s", addr.sun_path, strerror(errno));
+	return -1;
+}
+
+
+/*
+ * This is called when SSH_SMSG_X11_OPEN is received.  The packet contains
+ * the remote channel number.  We should do whatever we want, and respond
+ * with either SSH_MSG_OPEN_CONFIRMATION or SSH_MSG_OPEN_FAILURE.
+ */
+
+void 
+x11_input_open(int payload_len)
+{
+	int remote_channel, display_number, sock = 0, newch;
+	const char *display;
+	char buf[1024], *cp, *remote_host;
+	int remote_len;
+	struct addrinfo hints, *ai, *aitop;
+	char strport[NI_MAXSERV];
+	int gaierr;
+
+	/* Get remote channel number. */
+	remote_channel = packet_get_int();
+
+	/* Get remote originator name. */
+	if (have_hostname_in_open) {
+		remote_host = packet_get_string(&remote_len);
+		remote_len += 4;
+	} else {
+		remote_host = xstrdup("unknown (remote did not supply name)");
+		remote_len = 0;
+	}
+
+	debug("Received X11 open request.");
+	packet_integrity_check(payload_len, 4 + remote_len, SSH_SMSG_X11_OPEN);
+
+	/* Try to open a socket for the local X server. */
+	display = getenv("DISPLAY");
+	if (!display) {
+		error("DISPLAY not set.");
+		goto fail;
+	}
+	/*
+	 * Now we decode the value of the DISPLAY variable and make a
+	 * connection to the real X server.
+	 */
+
+	/*
+	 * Check if it is a unix domain socket.  Unix domain displays are in
+	 * one of the following formats: unix:d[.s], :d[.s], ::d[.s]
+	 */
+	if (strncmp(display, "unix:", 5) == 0 ||
+	    display[0] == ':') {
+		/* Connect to the unix domain socket. */
+		if (sscanf(strrchr(display, ':') + 1, "%d", &display_number) != 1) {
+			error("Could not parse display number from DISPLAY: %.100s",
+			      display);
+			goto fail;
+		}
+		/* Create a socket. */
+		sock = connect_local_xsocket(display_number);
+		if (sock < 0)
+			goto fail;
+
+		/* OK, we now have a connection to the display. */
+		goto success;
+	}
+	/*
+	 * Connect to an inet socket.  The DISPLAY value is supposedly
+	 * hostname:d[.s], where hostname may also be numeric IP address.
+	 */
+	strncpy(buf, display, sizeof(buf));
+	buf[sizeof(buf) - 1] = 0;
+	cp = strchr(buf, ':');
+	if (!cp) {
+		error("Could not find ':' in DISPLAY: %.100s", display);
+		goto fail;
+	}
+	*cp = 0;
+	/* buf now contains the host name.  But first we parse the display number. */
+	if (sscanf(cp + 1, "%d", &display_number) != 1) {
+		error("Could not parse display number from DISPLAY: %.100s",
+		      display);
+		goto fail;
+	}
+
+	/* Look up the host address */
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = IPv4or6;
+	hints.ai_socktype = SOCK_STREAM;
+	snprintf(strport, sizeof strport, "%d", 6000 + display_number);
+	if ((gaierr = getaddrinfo(buf, strport, &hints, &aitop)) != 0) {
+		error("%.100s: unknown host. (%s)", buf, gai_strerror(gaierr));
+		goto fail;
+	}
+	for (ai = aitop; ai; ai = ai->ai_next) {
+		/* Create a socket. */
+		sock = socket(ai->ai_family, SOCK_STREAM, 0);
+		if (sock < 0) {
+			debug("socket: %.100s", strerror(errno));
+		continue;
+	}
+	/* Connect it to the display. */
+	if (connect(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
+		debug("connect %.100s port %d: %.100s", buf, 6000 + display_number, 
+		    strerror(errno));
+		close(sock);
+		continue;
+	}
+	/* Success */
+	break;
+
+	} /* (ai = aitop, ai; ai = ai->ai_next) */
+	freeaddrinfo(aitop);
+	if (!ai) {
+		error("connect %.100s port %d: %.100s", buf, 6000 + display_number, 
+		    strerror(errno));
+		goto fail;
+	}
+success:
+	/* We have successfully obtained a connection to the real X display. */
+
+	/* Allocate a channel for this connection. */
+	if (x11_saved_proto == NULL)
+		newch = channel_allocate(SSH_CHANNEL_OPEN, sock, remote_host);
+	else
+		newch = channel_allocate(SSH_CHANNEL_X11_OPEN, sock, remote_host);
+	channels[newch].remote_id = remote_channel;
+
+	/* Send a confirmation to the remote host. */
+	packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
+	packet_put_int(remote_channel);
+	packet_put_int(newch);
+	packet_send();
+
+	return;
+
+fail:
+	/* Send refusal to the remote host. */
+	packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
+	packet_put_int(remote_channel);
+	packet_send();
+}
+
+/*
+ * Requests forwarding of X11 connections, generates fake authentication
+ * data, and enables authentication spoofing.
+ */
+
+void 
+x11_request_forwarding_with_spoofing(const char *proto, const char *data)
+{
+	unsigned int data_len = (unsigned int) strlen(data) / 2;
+	unsigned int i, value;
+	char *new_data;
+	int screen_number;
+	const char *cp;
+	u_int32_t rand = 0;
+
+	cp = getenv("DISPLAY");
+	if (cp)
+		cp = strchr(cp, ':');
+	if (cp)
+		cp = strchr(cp, '.');
+	if (cp)
+		screen_number = atoi(cp + 1);
+	else
+		screen_number = 0;
+
+	/* Save protocol name. */
+	x11_saved_proto = xstrdup(proto);
+
+	/*
+	 * Extract real authentication data and generate fake data of the
+	 * same length.
+	 */
+	x11_saved_data = xmalloc(data_len);
+	x11_fake_data = xmalloc(data_len);
+	for (i = 0; i < data_len; i++) {
+		if (sscanf(data + 2 * i, "%2x", &value) != 1)
+			fatal("x11_request_forwarding: bad authentication data: %.100s", data);
+		if (i % 4 == 0)
+			rand = arc4random();
+		x11_saved_data[i] = value;
+		x11_fake_data[i] = rand & 0xff;
+		rand >>= 8;
+	}
+	x11_saved_data_len = data_len;
+	x11_fake_data_len = data_len;
+
+	/* Convert the fake data into hex. */
+	new_data = xmalloc(2 * data_len + 1);
+	for (i = 0; i < data_len; i++)
+		sprintf(new_data + 2 * i, "%02x", (unsigned char) x11_fake_data[i]);
+
+	/* Send the request packet. */
+	packet_start(SSH_CMSG_X11_REQUEST_FORWARDING);
+	packet_put_string(proto, strlen(proto));
+	packet_put_string(new_data, strlen(new_data));
+	packet_put_int(screen_number);
+	packet_send();
+	packet_write_wait();
+	xfree(new_data);
+}
+
+/* Sends a message to the server to request authentication fd forwarding. */
+
+void 
+auth_request_forwarding()
+{
+	packet_start(SSH_CMSG_AGENT_REQUEST_FORWARDING);
+	packet_send();
+	packet_write_wait();
+}
+
+/*
+ * Returns the name of the forwarded authentication socket.  Returns NULL if
+ * there is no forwarded authentication socket.  The returned value points to
+ * a static buffer.
+ */
+
+char *
+auth_get_socket_name()
+{
+	return channel_forwarded_auth_socket_name;
+}
+
+/* removes the agent forwarding socket */
+
+void 
+cleanup_socket(void)
+{
+	remove(channel_forwarded_auth_socket_name);
+	rmdir(channel_forwarded_auth_socket_dir);
+}
+
+/*
+ * This if called to process SSH_CMSG_AGENT_REQUEST_FORWARDING on the server.
+ * This starts forwarding authentication requests.
+ */
+
+void 
+auth_input_request_forwarding(struct passwd * pw)
+{
+	int sock, newch;
+	struct sockaddr_un sunaddr;
+
+	if (auth_get_socket_name() != NULL)
+		fatal("Protocol error: authentication forwarding requested twice.");
+
+	/* Temporarily drop privileged uid for mkdir/bind. */
+	temporarily_use_uid(pw->pw_uid);
+
+	/* Allocate a buffer for the socket name, and format the name. */
+	channel_forwarded_auth_socket_name = xmalloc(MAX_SOCKET_NAME);
+	channel_forwarded_auth_socket_dir = xmalloc(MAX_SOCKET_NAME);
+	strlcpy(channel_forwarded_auth_socket_dir, "/tmp/ssh-XXXXXXXX", MAX_SOCKET_NAME);
+
+	/* Create private directory for socket */
+	if (mkdtemp(channel_forwarded_auth_socket_dir) == NULL)
+		packet_disconnect("mkdtemp: %.100s", strerror(errno));
+	snprintf(channel_forwarded_auth_socket_name, MAX_SOCKET_NAME, "%s/agent.%d",
+		 channel_forwarded_auth_socket_dir, (int) getpid());
+
+	if (atexit(cleanup_socket) < 0) {
+		int saved = errno;
+		cleanup_socket();
+		packet_disconnect("socket: %.100s", strerror(saved));
+	}
+	/* Create the socket. */
+	sock = socket(AF_UNIX, SOCK_STREAM, 0);
+	if (sock < 0)
+		packet_disconnect("socket: %.100s", strerror(errno));
+
+	/* Bind it to the name. */
+	memset(&sunaddr, 0, sizeof(sunaddr));
+	sunaddr.sun_family = AF_UNIX;
+	strncpy(sunaddr.sun_path, channel_forwarded_auth_socket_name,
+		sizeof(sunaddr.sun_path));
+
+	if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0)
+		packet_disconnect("bind: %.100s", strerror(errno));
+
+	/* Restore the privileged uid. */
+	restore_uid();
+
+	/* Start listening on the socket. */
+	if (listen(sock, 5) < 0)
+		packet_disconnect("listen: %.100s", strerror(errno));
+
+	/* Allocate a channel for the authentication agent socket. */
+	newch = channel_allocate(SSH_CHANNEL_AUTH_SOCKET, sock,
+				 xstrdup("auth socket"));
+	strlcpy(channels[newch].path, channel_forwarded_auth_socket_name,
+	    sizeof(channels[newch].path));
+}
+
+/* This is called to process an SSH_SMSG_AGENT_OPEN message. */
+
+void 
+auth_input_open_request()
+{
+	int remch, sock, newch;
+	char *dummyname;
+
+	/* Read the remote channel number from the message. */
+	remch = packet_get_int();
+
+	/*
+	 * Get a connection to the local authentication agent (this may again
+	 * get forwarded).
+	 */
+	sock = ssh_get_authentication_socket();
+
+	/*
+	 * If we could not connect the agent, send an error message back to
+	 * the server. This should never happen unless the agent dies,
+	 * because authentication forwarding is only enabled if we have an
+	 * agent.
+	 */
+	if (sock < 0) {
+		packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
+		packet_put_int(remch);
+		packet_send();
+		return;
+	}
+	debug("Forwarding authentication connection.");
+
+	/*
+	 * Dummy host name.  This will be freed when the channel is freed; it
+	 * will still be valid in the packet_put_string below since the
+	 * channel cannot yet be freed at that point.
+	 */
+	dummyname = xstrdup("authentication agent connection");
+
+	newch = channel_allocate(SSH_CHANNEL_OPEN, sock, dummyname);
+	channels[newch].remote_id = remch;
+
+	/* Send a confirmation to the remote host. */
+	packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
+	packet_put_int(remch);
+	packet_put_int(newch);
+	packet_send();
+}