/* * * channels.c * * Author: Tatu Ylonen * * Copyright (c) 1995 Tatu Ylonen , 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 1.37 2000/01/10 10:12:52 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); packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE); packet_put_int(remote_channel); packet_send(); } } 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(); }