| /* |
| * Author: Tatu Ylonen <ylo@cs.hut.fi> |
| * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| * All rights reserved |
| * Created: Sun Sep 10 00:30:37 1995 ylo |
| * Server main loop for handling the interactive session. |
| */ |
| |
| #include "includes.h" |
| #include "xmalloc.h" |
| #include "ssh.h" |
| #include "packet.h" |
| #include "buffer.h" |
| #include "servconf.h" |
| #include "pty.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 int 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 |
| sigchld_handler(int sig) |
| { |
| int save_errno = errno; |
| int 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; |
| } |
| |
| /* |
| * Process any buffered packets that have been received from the client. |
| */ |
| void |
| process_buffered_input_packets() |
| { |
| int type; |
| char *data; |
| unsigned int data_len; |
| int row, col, xpixel, ypixel; |
| int payload_len; |
| |
| /* Process buffered packets from the client. */ |
| while ((type = packet_read_poll(&payload_len)) != SSH_MSG_NONE) { |
| switch (type) { |
| case SSH_CMSG_STDIN_DATA: |
| /* Stdin data from the client. Append it to the buffer. */ |
| /* Ignore any data if the client has closed stdin. */ |
| if (fdin == -1) |
| break; |
| data = packet_get_string(&data_len); |
| packet_integrity_check(payload_len, (4 + data_len), type); |
| buffer_append(&stdin_buffer, data, data_len); |
| memset(data, 0, data_len); |
| xfree(data); |
| break; |
| |
| case SSH_CMSG_EOF: |
| /* 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(payload_len, 0, type); |
| stdin_eof = 1; |
| break; |
| |
| case SSH_CMSG_WINDOW_SIZE: |
| debug("Window change received."); |
| packet_integrity_check(payload_len, 4 * 4, type); |
| row = packet_get_int(); |
| col = packet_get_int(); |
| xpixel = packet_get_int(); |
| ypixel = packet_get_int(); |
| if (fdin != -1) |
| pty_change_window_size(fdin, row, col, xpixel, ypixel); |
| break; |
| |
| case SSH_MSG_PORT_OPEN: |
| debug("Received port open request."); |
| channel_input_port_open(payload_len); |
| break; |
| |
| case SSH_MSG_CHANNEL_OPEN_CONFIRMATION: |
| debug("Received channel open confirmation."); |
| packet_integrity_check(payload_len, 4 + 4, type); |
| channel_input_open_confirmation(); |
| break; |
| |
| case SSH_MSG_CHANNEL_OPEN_FAILURE: |
| debug("Received channel open failure."); |
| packet_integrity_check(payload_len, 4, type); |
| channel_input_open_failure(); |
| break; |
| |
| case SSH_MSG_CHANNEL_DATA: |
| channel_input_data(payload_len); |
| break; |
| |
| case SSH_MSG_CHANNEL_CLOSE: |
| debug("Received channel close."); |
| packet_integrity_check(payload_len, 4, type); |
| channel_input_close(); |
| break; |
| |
| case SSH_MSG_CHANNEL_CLOSE_CONFIRMATION: |
| debug("Received channel close confirmation."); |
| packet_integrity_check(payload_len, 4, type); |
| channel_input_close_confirmation(); |
| break; |
| |
| default: |
| /* In this phase, any unexpected messages cause a |
| protocol error. This is to ease debugging; |
| also, since no confirmations are sent messages, |
| unprocessed unknown messages could cause |
| strange problems. Any compatible protocol |
| extensions must be negotiated before entering |
| the interactive session. */ |
| packet_disconnect("Protocol error during session: type %d", |
| type); |
| } |
| } |
| } |
| |
| /* |
| * 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); |
| |
| /* Read packets from the client unless we have too much buffered |
| stdin or channel data. */ |
| if (buffer_len(&stdin_buffer) < 4096 && |
| 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); |
| } |
| FD_ZERO(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); |
| |
| /* 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); |
| |
| /* 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; |
| } |
| |
| /* 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(); |
| } |
| /* There is a kernel bug on Solaris that causes select to |
| sometimes wake up even though there is no data |
| available. */ |
| if (len < 0 && errno == EAGAIN) |
| len = 0; |
| |
| if (len < 0) { |
| verbose("Read error from remote host: %.100s", strerror(errno)); |
| fatal_cleanup(); |
| } |
| /* Buffer any received data. */ |
| packet_process_incoming(buf, len); |
| } |
| /* 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) |
| 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) |
| 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 (fdin != -1 && FD_ISSET(fdin, writeset)) { |
| len = write(fdin, buffer_ptr(&stdin_buffer), |
| buffer_len(&stdin_buffer)); |
| if (len <= 0) { |
| #ifdef USE_PIPES |
| close(fdin); |
| #else |
| if (fdout == -1) |
| 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(); |
| } |
| |
| /* |
| * 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(int pid, int fdin_arg, int fdout_arg, int fderr_arg) |
| { |
| int wait_status, wait_pid; /* Status and 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; |
| 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; |
| |
| /* Main loop of the server for the interactive session mode. */ |
| for (;;) { |
| fd_set readset, writeset; |
| |
| /* 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 (fdout == -1) |
| 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()) |
| goto quit; |
| 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); |
| } |
| |
| quit: |
| /* 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 */ |
| } |