From d4a8b7e34dd619a4debf9a206c81db26d1402ea6 Mon Sep 17 00:00:00 2001 From: Damien Miller Date: Wed, 27 Oct 1999 13:42:43 +1000 Subject: Initial revision --- channels.c | 1500 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 1500 insertions(+) create mode 100644 channels.c (limited to 'channels.c') diff --git a/channels.c b/channels.c new file mode 100644 index 00000000..38a65a07 --- /dev/null +++ b/channels.c @@ -0,0 +1,1500 @@ +/* + +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 1.1 1999/10/27 03:42:44 damien Exp $"); + +#include "ssh.h" +#include "packet.h" +#include "xmalloc.h" +#include "buffer.h" +#include "authfd.h" +#include "uidswap.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. */ + int 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, old_channels; + + /* Update the maximum file descriptor value. */ + if (sock > channel_max_fd_value) + channel_max_fd_value = sock; + + /* 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 (i = 0; i < channels_alloc; i++) + if (channels[i].type == SSH_CHANNEL_FREE) + { + /* Found a free slot. Initialize the fields and return its number. */ + buffer_init(&channels[i].input); + buffer_init(&channels[i].output); + channels[i].self = i; + channels[i].type = type; + channels[i].x11 = 0; + channels[i].sock = sock; + channels[i].remote_id = -1; + channels[i].remote_name = remote_name; + chan_init_iostates(&channels[i]); + return i; + } + + /* There are no free slots. Must expand the array. */ + old_channels = channels_alloc; + channels_alloc += 10; + channels = xrealloc(channels, channels_alloc * sizeof(Channel)); + for (i = old_channels; i < channels_alloc; i++) + channels[i].type = SSH_CHANNEL_FREE; + + /* We know that the next one after the old maximum channel number is now + available. Initialize and return its number. */ + buffer_init(&channels[old_channels].input); + buffer_init(&channels[old_channels].output); + channels[old_channels].self = old_channels; + channels[old_channels].type = type; + channels[old_channels].x11 = 0; + channels[old_channels].sock = sock; + channels[old_channels].remote_id = -1; + channels[old_channels].remote_name = remote_name; + chan_init_iostates(&channels[old_channels]); + return old_channels; +} + +/* Free the channel and close its socket. */ + +void channel_free(int channel) +{ + assert(channel >= 0 && channel < channels_alloc && + channels[channel].type != SSH_CHANNEL_FREE); + 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) < 32768) + 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) < 32768) + 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.", i); + break; + } + break; + + case SSH_CHANNEL_OUTPUT_DRAINING: + if (!compat13) + fatal("cannot happen: OUT_DRAIN"); + if (buffer_len(&ch->output) == 0) + { + /* debug("Freeing channel %d after output drain.", i); */ + 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; + } + + /* Received authentication protocol and data match our fake data. + Substitute the fake data with real data. */ + assert(x11_fake_data_len == x11_saved_data_len); + 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; + /* Enable X11 Problem FIX */ + ch->x11 = 1; + 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 0x%x 0x%x", ch->self, ch->istate, ch->ostate); + chan_read_failed(ch); + chan_write_failed(ch); + debug("X11 rejected %d 0x%x 0x%x", 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 addrlen, newsock, i, newch, len; + 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:%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, "port %d, connection from %.200s port %d", + ch->listening_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)) + { + int nchan; + len = sizeof(addr); + newsock = accept(ch->sock, &addr, &len); + if (newsock < 0) + { + error("accept from auth socket: %.100s", strerror(errno)); + break; + } + + nchan = channel_allocate(SSH_CHANNEL_OPENING, newsock, + xstrdup("accepted auth socket")); + packet_start(SSH_SMSG_AGENT_OPEN); + packet_put_int(nchan); + 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 (ch->type != SSH_CHANNEL_OPEN && + ch->type != SSH_CHANNEL_INPUT_DRAINING) + 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 + { + if (len > 16384) + len = 16384; /* Keep the packets at reasonable size. */ + } + 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 channel; + char *data; + unsigned int data_len; + + /* 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); + + /* Ignore any data for non-open channels (might happen on close) */ + if (channels[channel].type != SSH_CHANNEL_OPEN && + channels[channel].type != SSH_CHANNEL_X11_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(&channels[channel].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]; + switch (ch->type) + { + case SSH_CHANNEL_X11_LISTENER: + case SSH_CHANNEL_PORT_LISTENER: + case SSH_CHANNEL_AUTH_SOCKET: + continue; + case SSH_CHANNEL_OPEN: + if (buffer_len(&ch->input) > 32768) + return 0; + if (buffer_len(&ch->output) > 32768) + return 0; + continue; + case SSH_CHANNEL_INPUT_DRAINING: + case SSH_CHANNEL_OUTPUT_DRAINING: + case SSH_CHANNEL_X11_OPEN: + case SSH_CHANNEL_FREE: + default: + continue; + } + } + 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; + /* debug("Setting status to output draining; output len = %d", + buffer_len(&channels[channel].output)); */ + } +} + +/* 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/%d %.300s\r\n", + c->self,c->type,c->remote_name); + 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(int port, const char *host, + int host_port) +{ + int ch, sock; + struct sockaddr_in sin; + extern Options options; + + if (strlen(host) > sizeof(channels[0].path) - 1) + packet_disconnect("Forward host name too long."); + + /* Create a port to listen for the host. */ + sock = socket(AF_INET, SOCK_STREAM, 0); + if (sock < 0) + packet_disconnect("socket: %.100s", strerror(errno)); + + /* Initialize socket address. */ + memset(&sin, 0, sizeof(sin)); + sin.sin_family = AF_INET; + if (options.gateway_ports == 1) + sin.sin_addr.s_addr = htonl(INADDR_ANY); + else + sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK); + sin.sin_port = htons(port); + + /* Bind the socket to the address. */ + if (bind(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0) + packet_disconnect("bind: %.100s", strerror(errno)); + + /* Start listening for connections on the socket. */ + if (listen(sock, 5) < 0) + packet_disconnect("listen: %.100s", strerror(errno)); + + /* Allocate a channel number for the socket. */ + ch = channel_allocate(SSH_CHANNEL_PORT_LISTENER, sock, + xstrdup("port listener")); + strcpy(channels[ch].path, host); /* note: host name stored here */ + channels[ch].host_port = host_port; /* port on host to connect to */ + channels[ch].listening_port = port; /* port being listened */ +} + +/* 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(int port, const char *host, + int 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) +{ + int port, host_port; + char *hostname; + + /* Get arguments from the packet. */ + port = packet_get_int(); + hostname = packet_get_string(NULL); + host_port = packet_get_int(); + + /* Port numbers are 16 bit quantities. */ + if ((port & 0xffff) != port) + packet_disconnect("Requested forwarding of nonexistent port %d.", port); + + /* 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. */ + channel_request_local_forwarding(port, hostname, host_port); + + /* 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, newch, host_port, i; + struct sockaddr_in sin; + char *host, *originator_string; + struct hostent *hp; + int host_len, originator_len; + + /* 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); + else + originator_string = xstrdup("unknown (remote did not supply name)"); + + packet_integrity_check(payload_len, + 4 + 4 + host_len + 4 + 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(&sin, 0, sizeof(sin)); + sin.sin_addr.s_addr = inet_addr(host); + if ((sin.sin_addr.s_addr & 0xffffffff) != 0xffffffff) + { + /* It was a valid numeric host address. */ + sin.sin_family = AF_INET; + } + else + { + /* Look up the host address from the name servers. */ + hp = gethostbyname(host); + if (!hp) + { + error("%.100s: unknown host.", host); + goto fail; + } + if (!hp->h_addr_list[0]) + { + error("%.100s: host has no IP address.", host); + goto fail; + } + sin.sin_family = hp->h_addrtype; + memcpy(&sin.sin_addr, hp->h_addr_list[0], + sizeof(sin.sin_addr)); + } + sin.sin_port = htons(host_port); + + /* Create the socket. */ + sock = socket(sin.sin_family, SOCK_STREAM, 0); + if (sock < 0) + { + error("socket: %.100s", strerror(errno)); + goto fail; + } + + /* Connect to the host/port. */ + if (connect(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0) + { + error("connect %.100s:%d: %.100s", host, host_port, + strerror(errno)); + close(sock); + 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. */ + +char *x11_create_display_inet(int screen_number) +{ + extern ServerOptions options; + int display_number, port, sock; + struct sockaddr_in sin; + char buf[512]; + char hostname[MAXHOSTNAMELEN]; + + for (display_number = options.x11_display_offset; display_number < MAX_DISPLAYS; display_number++) + { + port = 6000 + display_number; + memset(&sin, 0, sizeof(sin)); + sin.sin_family = AF_INET; + sin.sin_addr.s_addr = htonl(INADDR_ANY); + sin.sin_port = htons(port); + + sock = socket(AF_INET, SOCK_STREAM, 0); + if (sock < 0) + { + error("socket: %.100s", strerror(errno)); + return NULL; + } + + if (bind(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0) + { + debug("bind port %d: %.100s", port, strerror(errno)); + shutdown(sock, SHUT_RDWR); + close(sock); + continue; + } + break; + } + if (display_number >= MAX_DISPLAYS) + { + error("Failed to allocate internet-domain X11 display socket."); + return NULL; + } + + /* Start listening for connections on the socket. */ + 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(buf, sizeof buf, "%.400s:%d.%d", hostname, + display_number, screen_number); + + /* Allocate a channel for the socket. */ + (void)channel_allocate(SSH_CHANNEL_X11_LISTENER, sock, + xstrdup("X11 inet listener")); + + /* Return a suitable value for the DISPLAY environment variable. */ + return xstrdup(buf); +} + +#ifndef X_UNIX_PATH +#define X_UNIX_PATH "/tmp/.X11-unix/X" +#endif + +static +int +connect_local_xsocket(unsigned 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, newch; + const char *display; + struct sockaddr_in sin; + char buf[1024], *cp, *remote_host; + struct hostent *hp; + int remote_len; + + /* 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); + else + remote_host = xstrdup("unknown (remote did not supply name)"); + + debug("Received X11 open request."); + packet_integrity_check(payload_len, 4 + 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; + } + + /* Try to parse the host name as a numeric IP address. */ + memset(&sin, 0, sizeof(sin)); + sin.sin_addr.s_addr = inet_addr(buf); + if ((sin.sin_addr.s_addr & 0xffffffff) != 0xffffffff) + { + /* It was a valid numeric host address. */ + sin.sin_family = AF_INET; + } + else + { + /* Not a numeric IP address. */ + /* Look up the host address from the name servers. */ + hp = gethostbyname(buf); + if (!hp) + { + error("%.100s: unknown host.", buf); + goto fail; + } + if (!hp->h_addr_list[0]) + { + error("%.100s: host has no IP address.", buf); + goto fail; + } + sin.sin_family = hp->h_addrtype; + memcpy(&sin.sin_addr, hp->h_addr_list[0], + sizeof(sin.sin_addr)); + } + /* Set port number. */ + sin.sin_port = htons(6000 + display_number); + + /* Create a socket. */ + sock = socket(sin.sin_family, SOCK_STREAM, 0); + if (sock < 0) + { + error("socket: %.100s", strerror(errno)); + goto fail; + } + /* Connect it to the display. */ + if (connect(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0) + { + error("connect %.100s:%d: %.100s", buf, 6000 + display_number, + strerror(errno)); + close(sock); + 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")); + strcpy(channels[newch].path, channel_forwarded_auth_socket_name); +} + +/* 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(); +} -- cgit v1.2.1