/* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland * All rights reserved * Created: Sun Sep 10 00:30:37 1995 ylo * Server main loop for handling the interactive session. */ /* * SSH2 support by Markus Friedl. * Copyright (c) 2000 Markus Friedl. All rights reserved. */ #include "includes.h" #include "xmalloc.h" #include "ssh.h" #include "packet.h" #include "buffer.h" #include "servconf.h" #include "pty.h" #include "channels.h" #include "compat.h" #include "ssh2.h" #include "session.h" #include "dispatch.h" #include "auth-options.h" static Buffer stdin_buffer; /* Buffer for stdin data. */ static Buffer stdout_buffer; /* Buffer for stdout data. */ static Buffer stderr_buffer; /* Buffer for stderr data. */ static int fdin; /* Descriptor for stdin (for writing) */ static int fdout; /* Descriptor for stdout (for reading); May be same number as fdin. */ static int fderr; /* Descriptor for stderr. May be -1. */ static long stdin_bytes = 0; /* Number of bytes written to stdin. */ static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */ static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */ static long fdout_bytes = 0; /* Number of stdout bytes read from program. */ static int stdin_eof = 0; /* EOF message received from client. */ static int fdout_eof = 0; /* EOF encountered reading from fdout. */ static int fderr_eof = 0; /* EOF encountered readung from fderr. */ static int connection_in; /* Connection to client (input). */ static int connection_out; /* Connection to client (output). */ static unsigned int buffer_high;/* "Soft" max buffer size. */ static int max_fd; /* Max file descriptor number for select(). */ /* * This SIGCHLD kludge is used to detect when the child exits. The server * will exit after that, as soon as forwarded connections have terminated. */ static pid_t child_pid; /* Pid of the child. */ static volatile int child_terminated; /* The child has terminated. */ static volatile int child_wait_status; /* Status from wait(). */ void server_init_dispatch(void); void sigchld_handler(int sig) { int save_errno = errno; pid_t wait_pid; debug("Received SIGCHLD."); wait_pid = wait((int *) &child_wait_status); if (wait_pid != -1) { if (wait_pid != child_pid) error("Strange, got SIGCHLD and wait returned pid %d but child is %d", wait_pid, child_pid); if (WIFEXITED(child_wait_status) || WIFSIGNALED(child_wait_status)) child_terminated = 1; } signal(SIGCHLD, sigchld_handler); errno = save_errno; } void sigchld_handler2(int sig) { int save_errno = errno; debug("Received SIGCHLD."); child_terminated = 1; signal(SIGCHLD, sigchld_handler2); errno = save_errno; } /* * Make packets from buffered stderr data, and buffer it for sending * to the client. */ void make_packets_from_stderr_data() { int len; /* Send buffered stderr data to the client. */ while (buffer_len(&stderr_buffer) > 0 && packet_not_very_much_data_to_write()) { len = buffer_len(&stderr_buffer); if (packet_is_interactive()) { if (len > 512) len = 512; } else { /* Keep the packets at reasonable size. */ if (len > packet_get_maxsize()) len = packet_get_maxsize(); } packet_start(SSH_SMSG_STDERR_DATA); packet_put_string(buffer_ptr(&stderr_buffer), len); packet_send(); buffer_consume(&stderr_buffer, len); stderr_bytes += len; } } /* * Make packets from buffered stdout data, and buffer it for sending to the * client. */ void make_packets_from_stdout_data() { int len; /* Send buffered stdout data to the client. */ while (buffer_len(&stdout_buffer) > 0 && packet_not_very_much_data_to_write()) { len = buffer_len(&stdout_buffer); if (packet_is_interactive()) { if (len > 512) len = 512; } else { /* Keep the packets at reasonable size. */ if (len > packet_get_maxsize()) len = packet_get_maxsize(); } packet_start(SSH_SMSG_STDOUT_DATA); packet_put_string(buffer_ptr(&stdout_buffer), len); packet_send(); buffer_consume(&stdout_buffer, len); stdout_bytes += len; } } /* * Sleep in select() until we can do something. This will initialize the * select masks. Upon return, the masks will indicate which descriptors * have data or can accept data. Optionally, a maximum time can be specified * for the duration of the wait (0 = infinite). */ void wait_until_can_do_something(fd_set * readset, fd_set * writeset, unsigned int max_time_milliseconds) { struct timeval tv, *tvp; int ret; /* When select fails we restart from here. */ retry_select: /* Initialize select() masks. */ FD_ZERO(readset); FD_ZERO(writeset); if (compat20) { /* wrong: bad condition XXX */ if (channel_not_very_much_buffered_data()) FD_SET(connection_in, readset); } else { /* * Read packets from the client unless we have too much * buffered stdin or channel data. */ if (buffer_len(&stdin_buffer) < buffer_high && channel_not_very_much_buffered_data()) FD_SET(connection_in, readset); /* * If there is not too much data already buffered going to * the client, try to get some more data from the program. */ if (packet_not_very_much_data_to_write()) { if (!fdout_eof) FD_SET(fdout, readset); if (!fderr_eof) FD_SET(fderr, readset); } /* * If we have buffered data, try to write some of that data * to the program. */ if (fdin != -1 && buffer_len(&stdin_buffer) > 0) FD_SET(fdin, writeset); } /* Set masks for channel descriptors. */ channel_prepare_select(readset, writeset); /* * If we have buffered packet data going to the client, mark that * descriptor. */ if (packet_have_data_to_write()) FD_SET(connection_out, writeset); /* Update the maximum descriptor number if appropriate. */ if (channel_max_fd() > max_fd) max_fd = channel_max_fd(); /* * If child has terminated and there is enough buffer space to read * from it, then read as much as is available and exit. */ if (child_terminated && packet_not_very_much_data_to_write()) if (max_time_milliseconds == 0) max_time_milliseconds = 100; if (max_time_milliseconds == 0) tvp = NULL; else { tv.tv_sec = max_time_milliseconds / 1000; tv.tv_usec = 1000 * (max_time_milliseconds % 1000); tvp = &tv; } if (tvp!=NULL) debug("tvp!=NULL kid %d mili %d", child_terminated, max_time_milliseconds); /* Wait for something to happen, or the timeout to expire. */ ret = select(max_fd + 1, readset, writeset, NULL, tvp); if (ret < 0) { if (errno != EINTR) error("select: %.100s", strerror(errno)); else goto retry_select; } } /* * Processes input from the client and the program. Input data is stored * in buffers and processed later. */ void process_input(fd_set * readset) { int len; char buf[16384]; /* Read and buffer any input data from the client. */ if (FD_ISSET(connection_in, readset)) { len = read(connection_in, buf, sizeof(buf)); if (len == 0) { verbose("Connection closed by remote host."); fatal_cleanup(); } else if (len < 0) { if (errno != EINTR && errno != EAGAIN) { verbose("Read error from remote host: %.100s", strerror(errno)); fatal_cleanup(); } } else { /* Buffer any received data. */ packet_process_incoming(buf, len); } } if (compat20) return; /* Read and buffer any available stdout data from the program. */ if (!fdout_eof && FD_ISSET(fdout, readset)) { len = read(fdout, buf, sizeof(buf)); if (len < 0 && (errno == EINTR || errno == EAGAIN)) { /* do nothing */ } else if (len <= 0) { fdout_eof = 1; } else { buffer_append(&stdout_buffer, buf, len); fdout_bytes += len; } } /* Read and buffer any available stderr data from the program. */ if (!fderr_eof && FD_ISSET(fderr, readset)) { len = read(fderr, buf, sizeof(buf)); if (len < 0 && (errno == EINTR || errno == EAGAIN)) { /* do nothing */ } else if (len <= 0) { fderr_eof = 1; } else { buffer_append(&stderr_buffer, buf, len); } } } /* * Sends data from internal buffers to client program stdin. */ void process_output(fd_set * writeset) { int len; /* Write buffered data to program stdin. */ if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) { len = write(fdin, buffer_ptr(&stdin_buffer), buffer_len(&stdin_buffer)); if (len < 0 && (errno == EINTR || errno == EAGAIN)) { /* do nothing */ } else if (len <= 0) { #ifdef USE_PIPES close(fdin); #else if (fdin != fdout) close(fdin); else shutdown(fdin, SHUT_WR); /* We will no longer send. */ #endif fdin = -1; } else { /* Successful write. Consume the data from the buffer. */ buffer_consume(&stdin_buffer, len); /* Update the count of bytes written to the program. */ stdin_bytes += len; } } /* Send any buffered packet data to the client. */ if (FD_ISSET(connection_out, writeset)) packet_write_poll(); } /* * Wait until all buffered output has been sent to the client. * This is used when the program terminates. */ void drain_output() { /* Send any buffered stdout data to the client. */ if (buffer_len(&stdout_buffer) > 0) { packet_start(SSH_SMSG_STDOUT_DATA); packet_put_string(buffer_ptr(&stdout_buffer), buffer_len(&stdout_buffer)); packet_send(); /* Update the count of sent bytes. */ stdout_bytes += buffer_len(&stdout_buffer); } /* Send any buffered stderr data to the client. */ if (buffer_len(&stderr_buffer) > 0) { packet_start(SSH_SMSG_STDERR_DATA); packet_put_string(buffer_ptr(&stderr_buffer), buffer_len(&stderr_buffer)); packet_send(); /* Update the count of sent bytes. */ stderr_bytes += buffer_len(&stderr_buffer); } /* Wait until all buffered data has been written to the client. */ packet_write_wait(); } void process_buffered_input_packets() { dispatch_run(DISPATCH_NONBLOCK, NULL); } /* * Performs the interactive session. This handles data transmission between * the client and the program. Note that the notion of stdin, stdout, and * stderr in this function is sort of reversed: this function writes to * stdin (of the child program), and reads from stdout and stderr (of the * child program). */ void server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg) { fd_set readset, writeset; int wait_status; /* Status returned by wait(). */ pid_t wait_pid; /* pid returned by wait(). */ int waiting_termination = 0; /* Have displayed waiting close message. */ unsigned int max_time_milliseconds; unsigned int previous_stdout_buffer_bytes; unsigned int stdout_buffer_bytes; int type; debug("Entering interactive session."); /* Initialize the SIGCHLD kludge. */ child_pid = pid; child_terminated = 0; signal(SIGCHLD, sigchld_handler); /* Initialize our global variables. */ fdin = fdin_arg; fdout = fdout_arg; fderr = fderr_arg; /* nonblocking IO */ set_nonblock(fdin); set_nonblock(fdout); /* we don't have stderr for interactive terminal sessions, see below */ if (fderr != -1) set_nonblock(fderr); connection_in = packet_get_connection_in(); connection_out = packet_get_connection_out(); previous_stdout_buffer_bytes = 0; /* Set approximate I/O buffer size. */ if (packet_is_interactive()) buffer_high = 4096; else buffer_high = 64 * 1024; /* Initialize max_fd to the maximum of the known file descriptors. */ max_fd = fdin; if (fdout > max_fd) max_fd = fdout; if (fderr != -1 && fderr > max_fd) max_fd = fderr; if (connection_in > max_fd) max_fd = connection_in; if (connection_out > max_fd) max_fd = connection_out; /* Initialize Initialize buffers. */ buffer_init(&stdin_buffer); buffer_init(&stdout_buffer); buffer_init(&stderr_buffer); /* * If we have no separate fderr (which is the case when we have a pty * - there we cannot make difference between data sent to stdout and * stderr), indicate that we have seen an EOF from stderr. This way * we don\'t need to check the descriptor everywhere. */ if (fderr == -1) fderr_eof = 1; server_init_dispatch(); /* Main loop of the server for the interactive session mode. */ for (;;) { /* Process buffered packets from the client. */ process_buffered_input_packets(); /* * If we have received eof, and there is no more pending * input data, cause a real eof by closing fdin. */ if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) { #ifdef USE_PIPES close(fdin); #else if (fdin != fdout) close(fdin); else shutdown(fdin, SHUT_WR); /* We will no longer send. */ #endif fdin = -1; } /* Make packets from buffered stderr data to send to the client. */ make_packets_from_stderr_data(); /* * Make packets from buffered stdout data to send to the * client. If there is very little to send, this arranges to * not send them now, but to wait a short while to see if we * are getting more data. This is necessary, as some systems * wake up readers from a pty after each separate character. */ max_time_milliseconds = 0; stdout_buffer_bytes = buffer_len(&stdout_buffer); if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 && stdout_buffer_bytes != previous_stdout_buffer_bytes) { /* try again after a while */ max_time_milliseconds = 10; } else { /* Send it now. */ make_packets_from_stdout_data(); } previous_stdout_buffer_bytes = buffer_len(&stdout_buffer); /* Send channel data to the client. */ if (packet_not_very_much_data_to_write()) channel_output_poll(); /* * Bail out of the loop if the program has closed its output * descriptors, and we have no more data to send to the * client, and there is no pending buffered data. */ if (fdout_eof && fderr_eof && !packet_have_data_to_write() && buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) { if (!channel_still_open()) break; if (!waiting_termination) { const char *s = "Waiting for forwarded connections to terminate...\r\n"; char *cp; waiting_termination = 1; buffer_append(&stderr_buffer, s, strlen(s)); /* Display list of open channels. */ cp = channel_open_message(); buffer_append(&stderr_buffer, cp, strlen(cp)); xfree(cp); } } /* Sleep in select() until we can do something. */ wait_until_can_do_something(&readset, &writeset, max_time_milliseconds); /* Process any channel events. */ channel_after_select(&readset, &writeset); /* Process input from the client and from program stdout/stderr. */ process_input(&readset); /* Process output to the client and to program stdin. */ process_output(&writeset); } /* Cleanup and termination code. */ /* Wait until all output has been sent to the client. */ drain_output(); debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.", stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes); /* Free and clear the buffers. */ buffer_free(&stdin_buffer); buffer_free(&stdout_buffer); buffer_free(&stderr_buffer); /* Close the file descriptors. */ if (fdout != -1) close(fdout); fdout = -1; fdout_eof = 1; if (fderr != -1) close(fderr); fderr = -1; fderr_eof = 1; if (fdin != -1) close(fdin); fdin = -1; /* Stop listening for channels; this removes unix domain sockets. */ channel_stop_listening(); /* Wait for the child to exit. Get its exit status. */ wait_pid = wait(&wait_status); if (wait_pid < 0) { /* * It is possible that the wait was handled by SIGCHLD * handler. This may result in either: this call * returning with EINTR, or: this call returning ECHILD. */ if (child_terminated) wait_status = child_wait_status; else packet_disconnect("wait: %.100s", strerror(errno)); } else { /* Check if it matches the process we forked. */ if (wait_pid != pid) error("Strange, wait returned pid %d, expected %d", wait_pid, pid); } /* We no longer want our SIGCHLD handler to be called. */ signal(SIGCHLD, SIG_DFL); /* Check if it exited normally. */ if (WIFEXITED(wait_status)) { /* Yes, normal exit. Get exit status and send it to the client. */ debug("Command exited with status %d.", WEXITSTATUS(wait_status)); packet_start(SSH_SMSG_EXITSTATUS); packet_put_int(WEXITSTATUS(wait_status)); packet_send(); packet_write_wait(); /* * Wait for exit confirmation. Note that there might be * other packets coming before it; however, the program has * already died so we just ignore them. The client is * supposed to respond with the confirmation when it receives * the exit status. */ do { int plen; type = packet_read(&plen); } while (type != SSH_CMSG_EXIT_CONFIRMATION); debug("Received exit confirmation."); return; } /* Check if the program terminated due to a signal. */ if (WIFSIGNALED(wait_status)) packet_disconnect("Command terminated on signal %d.", WTERMSIG(wait_status)); /* Some weird exit cause. Just exit. */ packet_disconnect("wait returned status %04x.", wait_status); /* NOTREACHED */ } void server_loop2(void) { fd_set readset, writeset; int had_channel = 0; int status; pid_t pid; debug("Entering interactive session for SSH2."); signal(SIGCHLD, sigchld_handler2); child_terminated = 0; connection_in = packet_get_connection_in(); connection_out = packet_get_connection_out(); max_fd = connection_in; if (connection_out > max_fd) max_fd = connection_out; server_init_dispatch(); for (;;) { process_buffered_input_packets(); if (!had_channel && channel_still_open()) had_channel = 1; if (had_channel && !channel_still_open()) { debug("!channel_still_open."); break; } if (packet_not_very_much_data_to_write()) channel_output_poll(); wait_until_can_do_something(&readset, &writeset, 0); if (child_terminated) { while ((pid = waitpid(-1, &status, WNOHANG)) > 0) session_close_by_pid(pid, status); child_terminated = 0; } channel_after_select(&readset, &writeset); process_input(&readset); process_output(&writeset); } signal(SIGCHLD, SIG_DFL); while ((pid = waitpid(-1, &status, WNOHANG)) > 0) session_close_by_pid(pid, status); channel_stop_listening(); } void server_input_stdin_data(int type, int plen) { char *data; unsigned int data_len; /* Stdin data from the client. Append it to the buffer. */ /* Ignore any data if the client has closed stdin. */ if (fdin == -1) return; data = packet_get_string(&data_len); packet_integrity_check(plen, (4 + data_len), type); buffer_append(&stdin_buffer, data, data_len); memset(data, 0, data_len); xfree(data); } void server_input_eof(int type, int plen) { /* * Eof from the client. The stdin descriptor to the * program will be closed when all buffered data has * drained. */ debug("EOF received for stdin."); packet_integrity_check(plen, 0, type); stdin_eof = 1; } void server_input_window_size(int type, int plen) { int row = packet_get_int(); int col = packet_get_int(); int xpixel = packet_get_int(); int ypixel = packet_get_int(); debug("Window change received."); packet_integrity_check(plen, 4 * 4, type); if (fdin != -1) pty_change_window_size(fdin, row, col, xpixel, ypixel); } int input_direct_tcpip(void) { int sock; char *target, *originator; int target_port, originator_port; target = packet_get_string(NULL); target_port = packet_get_int(); originator = packet_get_string(NULL); originator_port = packet_get_int(); packet_done(); debug("open direct-tcpip: from %s port %d to %s port %d", originator, originator_port, target, target_port); /* XXX check permission */ if (no_port_forwarding_flag) { xfree(target); xfree(originator); return -1; } sock = channel_connect_to(target, target_port); xfree(target); xfree(originator); if (sock < 0) return -1; return channel_new("direct-tcpip", SSH_CHANNEL_OPEN, sock, sock, -1, 4*1024, 32*1024, 0, xstrdup("direct-tcpip")); } void server_input_channel_open(int type, int plen) { Channel *c = NULL; char *ctype; int id; unsigned int len; int rchan; int rmaxpack; int rwindow; ctype = packet_get_string(&len); rchan = packet_get_int(); rwindow = packet_get_int(); rmaxpack = packet_get_int(); debug("channel_input_open: ctype %s rchan %d win %d max %d", ctype, rchan, rwindow, rmaxpack); if (strcmp(ctype, "session") == 0) { debug("open session"); packet_done(); /* * A server session has no fd to read or write * until a CHANNEL_REQUEST for a shell is made, * so we set the type to SSH_CHANNEL_LARVAL. * Additionally, a callback for handling all * CHANNEL_REQUEST messages is registered. */ id = channel_new(ctype, SSH_CHANNEL_LARVAL, -1, -1, -1, 0, 32*1024, 0, xstrdup("server-session")); if (session_open(id) == 1) { channel_register_callback(id, SSH2_MSG_CHANNEL_REQUEST, session_input_channel_req, (void *)0); channel_register_cleanup(id, session_close_by_channel); c = channel_lookup(id); } else { debug("session open failed, free channel %d", id); channel_free(id); } } else if (strcmp(ctype, "direct-tcpip") == 0) { id = input_direct_tcpip(); if (id >= 0) c = channel_lookup(id); } if (c != NULL) { debug("confirm %s", ctype); c->remote_id = rchan; c->remote_window = rwindow; c->remote_maxpacket = rmaxpack; packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); packet_put_int(c->remote_id); packet_put_int(c->self); packet_put_int(c->local_window); packet_put_int(c->local_maxpacket); packet_send(); } else { debug("failure %s", ctype); packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); packet_put_int(rchan); packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED); packet_put_cstring("bla bla"); packet_put_cstring(""); packet_send(); } xfree(ctype); } void server_init_dispatch_20() { debug("server_init_dispatch_20"); dispatch_init(&dispatch_protocol_error); dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &channel_input_channel_request); dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); } void server_init_dispatch_13() { debug("server_init_dispatch_13"); dispatch_init(NULL); dispatch_set(SSH_CMSG_EOF, &server_input_eof); dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data); dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size); dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close); dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation); dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data); dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open); } void server_init_dispatch_15() { server_init_dispatch_13(); debug("server_init_dispatch_15"); dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof); dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose); } void server_init_dispatch() { if (compat20) server_init_dispatch_20(); else if (compat13) server_init_dispatch_13(); else server_init_dispatch_15(); }