/* * * clientloop.c * * Author: Tatu Ylonen * * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland * All rights reserved * * * Created: Sat Sep 23 12:23:57 1995 ylo * * The main loop for the interactive session (client side). * */ #include "includes.h" RCSID("$Id: clientloop.c,v 1.13 1999/11/24 19:53:46 markus Exp $"); #include "xmalloc.h" #include "ssh.h" #include "packet.h" #include "buffer.h" #include "authfd.h" #include "readconf.h" /* Flag indicating that stdin should be redirected from /dev/null. */ extern int stdin_null_flag; /* * Name of the host we are connecting to. This is the name given on the * command line, or the HostName specified for the user-supplied name in a * configuration file. */ extern char *host; /* * Flag to indicate that we have received a window change signal which has * not yet been processed. This will cause a message indicating the new * window size to be sent to the server a little later. This is volatile * because this is updated in a signal handler. */ static volatile int received_window_change_signal = 0; /* Terminal modes, as saved by enter_raw_mode. */ static struct termios saved_tio; /* * Flag indicating whether we are in raw mode. This is used by * enter_raw_mode and leave_raw_mode. */ static int in_raw_mode = 0; /* Flag indicating whether the user\'s terminal is in non-blocking mode. */ static int in_non_blocking_mode = 0; /* Common data for the client loop code. */ static int escape_pending; /* Last character was the escape character */ static int last_was_cr; /* Last character was a newline. */ static int exit_status; /* Used to store the exit status of the command. */ static int stdin_eof; /* EOF has been encountered on standard error. */ 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 unsigned int buffer_high;/* Soft max buffer size. */ static int max_fd; /* Maximum file descriptor number in select(). */ static int connection_in; /* Connection to server (input). */ static int connection_out; /* Connection to server (output). */ static unsigned long stdin_bytes, stdout_bytes, stderr_bytes; static int quit_pending; /* Set to non-zero to quit the client loop. */ static int escape_char; /* Escape character. */ /* Returns the user\'s terminal to normal mode if it had been put in raw mode. */ void leave_raw_mode() { if (!in_raw_mode) return; in_raw_mode = 0; if (tcsetattr(fileno(stdin), TCSADRAIN, &saved_tio) < 0) perror("tcsetattr"); fatal_remove_cleanup((void (*) (void *)) leave_raw_mode, NULL); } /* Puts the user\'s terminal in raw mode. */ void enter_raw_mode() { struct termios tio; if (tcgetattr(fileno(stdin), &tio) < 0) perror("tcgetattr"); saved_tio = tio; tio.c_iflag |= IGNPAR; tio.c_iflag &= ~(ISTRIP | INLCR | IGNCR | ICRNL | IXON | IXANY | IXOFF); tio.c_lflag &= ~(ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHONL); #ifdef IEXTEN tio.c_lflag &= ~IEXTEN; #endif /* IEXTEN */ tio.c_oflag &= ~OPOST; tio.c_cc[VMIN] = 1; tio.c_cc[VTIME] = 0; if (tcsetattr(fileno(stdin), TCSADRAIN, &tio) < 0) perror("tcsetattr"); in_raw_mode = 1; fatal_add_cleanup((void (*) (void *)) leave_raw_mode, NULL); } /* Restores stdin to blocking mode. */ void leave_non_blocking() { if (in_non_blocking_mode) { (void) fcntl(fileno(stdin), F_SETFL, 0); in_non_blocking_mode = 0; fatal_remove_cleanup((void (*) (void *)) leave_non_blocking, NULL); } } /* Puts stdin terminal in non-blocking mode. */ void enter_non_blocking() { in_non_blocking_mode = 1; (void) fcntl(fileno(stdin), F_SETFL, O_NONBLOCK); fatal_add_cleanup((void (*) (void *)) leave_non_blocking, NULL); } /* * Signal handler for the window change signal (SIGWINCH). This just sets a * flag indicating that the window has changed. */ void window_change_handler(int sig) { received_window_change_signal = 1; signal(SIGWINCH, window_change_handler); } /* * Signal handler for signals that cause the program to terminate. These * signals must be trapped to restore terminal modes. */ void signal_handler(int sig) { if (in_raw_mode) leave_raw_mode(); if (in_non_blocking_mode) leave_non_blocking(); channel_stop_listening(); packet_close(); fatal("Killed by signal %d.", sig); } /* * Returns current time in seconds from Jan 1, 1970 with the maximum * available resolution. */ double get_current_time() { struct timeval tv; gettimeofday(&tv, NULL); return (double) tv.tv_sec + (double) tv.tv_usec / 1000000.0; } /* * This is called when the interactive is entered. This checks if there is * an EOF coming on stdin. We must check this explicitly, as select() does * not appear to wake up when redirecting from /dev/null. */ void client_check_initial_eof_on_stdin() { int len; char buf[1]; /* * If standard input is to be "redirected from /dev/null", we simply * mark that we have seen an EOF and send an EOF message to the * server. Otherwise, we try to read a single character; it appears * that for some files, such /dev/null, select() never wakes up for * read for this descriptor, which means that we never get EOF. This * way we will get the EOF if stdin comes from /dev/null or similar. */ if (stdin_null_flag) { /* Fake EOF on stdin. */ debug("Sending eof."); stdin_eof = 1; packet_start(SSH_CMSG_EOF); packet_send(); } else { enter_non_blocking(); /* Check for immediate EOF on stdin. */ len = read(fileno(stdin), buf, 1); if (len == 0) { /* EOF. Record that we have seen it and send EOF to server. */ debug("Sending eof."); stdin_eof = 1; packet_start(SSH_CMSG_EOF); packet_send(); } else if (len > 0) { /* * Got data. We must store the data in the buffer, * and also process it as an escape character if * appropriate. */ if ((unsigned char) buf[0] == escape_char) escape_pending = 1; else { buffer_append(&stdin_buffer, buf, 1); stdin_bytes += 1; } } leave_non_blocking(); } } /* * Get packets from the connection input buffer, and process them as long as * there are packets available. */ void client_process_buffered_input_packets() { int type; char *data; unsigned int data_len; int payload_len; /* Process any buffered packets from the server. */ while (!quit_pending && (type = packet_read_poll(&payload_len)) != SSH_MSG_NONE) { switch (type) { case SSH_SMSG_STDOUT_DATA: data = packet_get_string(&data_len); packet_integrity_check(payload_len, 4 + data_len, type); buffer_append(&stdout_buffer, data, data_len); stdout_bytes += data_len; memset(data, 0, data_len); xfree(data); break; case SSH_SMSG_STDERR_DATA: data = packet_get_string(&data_len); packet_integrity_check(payload_len, 4 + data_len, type); buffer_append(&stderr_buffer, data, data_len); stdout_bytes += data_len; memset(data, 0, data_len); xfree(data); break; case SSH_SMSG_EXITSTATUS: packet_integrity_check(payload_len, 4, type); exit_status = packet_get_int(); /* Acknowledge the exit. */ packet_start(SSH_CMSG_EXIT_CONFIRMATION); packet_send(); /* * Must wait for packet to be sent since we are * exiting the loop. */ packet_write_wait(); /* Flag that we want to exit. */ quit_pending = 1; break; case SSH_SMSG_X11_OPEN: x11_input_open(payload_len); break; case SSH_MSG_PORT_OPEN: channel_input_port_open(payload_len); break; case SSH_SMSG_AGENT_OPEN: packet_integrity_check(payload_len, 4, type); auth_input_open_request(); break; case SSH_MSG_CHANNEL_OPEN_CONFIRMATION: packet_integrity_check(payload_len, 4 + 4, type); channel_input_open_confirmation(); break; case SSH_MSG_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: packet_integrity_check(payload_len, 4, type); channel_input_close(); break; case SSH_MSG_CHANNEL_CLOSE_CONFIRMATION: packet_integrity_check(payload_len, 4, type); channel_input_close_confirmation(); break; default: /* * Any unknown packets received during the actual * session cause the session to terminate. This is * intended to make debugging easier since no * confirmations are sent. Any compatible protocol * extensions must be negotiated during the * preparatory phase. */ packet_disconnect("Protocol error during session: type %d", type); } } } /* * Make packets from buffered stdin data, and buffer them for sending to the * connection. */ void client_make_packets_from_stdin_data() { unsigned int len; /* Send buffered stdin data to the server. */ while (buffer_len(&stdin_buffer) > 0 && packet_not_very_much_data_to_write()) { len = buffer_len(&stdin_buffer); /* Keep the packets at reasonable size. */ if (len > packet_get_maxsize()) len = packet_get_maxsize(); packet_start(SSH_CMSG_STDIN_DATA); packet_put_string(buffer_ptr(&stdin_buffer), len); packet_send(); buffer_consume(&stdin_buffer, len); /* If we have a pending EOF, send it now. */ if (stdin_eof && buffer_len(&stdin_buffer) == 0) { packet_start(SSH_CMSG_EOF); packet_send(); } } } /* * Checks if the client window has changed, and sends a packet about it to * the server if so. The actual change is detected elsewhere (by a software * interrupt on Unix); this just checks the flag and sends a message if * appropriate. */ void client_check_window_change() { /* Send possible window change message to the server. */ if (received_window_change_signal) { struct winsize ws; /* Clear the window change indicator. */ received_window_change_signal = 0; /* Read new window size. */ if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) >= 0) { /* Successful, send the packet now. */ packet_start(SSH_CMSG_WINDOW_SIZE); packet_put_int(ws.ws_row); packet_put_int(ws.ws_col); packet_put_int(ws.ws_xpixel); packet_put_int(ws.ws_ypixel); packet_send(); } } } /* * Waits until the client can do something (some data becomes available on * one of the file descriptors). */ void client_wait_until_can_do_something(fd_set * readset, fd_set * writeset) { /* Initialize select masks. */ FD_ZERO(readset); /* Read from the connection, unless our buffers are full. */ if (buffer_len(&stdout_buffer) < buffer_high && buffer_len(&stderr_buffer) < buffer_high && channel_not_very_much_buffered_data()) FD_SET(connection_in, readset); /* * Read from stdin, unless we have seen EOF or have very much * buffered data to send to the server. */ if (!stdin_eof && packet_not_very_much_data_to_write()) FD_SET(fileno(stdin), readset); FD_ZERO(writeset); /* Add any selections by the channel mechanism. */ channel_prepare_select(readset, writeset); /* Select server connection if have data to write to the server. */ if (packet_have_data_to_write()) FD_SET(connection_out, writeset); /* Select stdout if have data in buffer. */ if (buffer_len(&stdout_buffer) > 0) FD_SET(fileno(stdout), writeset); /* Select stderr if have data in buffer. */ if (buffer_len(&stderr_buffer) > 0) FD_SET(fileno(stderr), writeset); /* Update maximum file descriptor number, if appropriate. */ if (channel_max_fd() > max_fd) max_fd = channel_max_fd(); /* * Wait for something to happen. This will suspend the process until * some selected descriptor can be read, written, or has some other * event pending. Note: if you want to implement SSH_MSG_IGNORE * messages to fool traffic analysis, this might be the place to do * it: just have a random timeout for the select, and send a random * SSH_MSG_IGNORE packet when the timeout expires. */ if (select(max_fd + 1, readset, writeset, NULL, NULL) < 0) { char buf[100]; /* Some systems fail to clear these automatically. */ FD_ZERO(readset); FD_ZERO(writeset); if (errno == EINTR) return; /* Note: we might still have data in the buffers. */ snprintf(buf, sizeof buf, "select: %s\r\n", strerror(errno)); buffer_append(&stderr_buffer, buf, strlen(buf)); stderr_bytes += strlen(buf); quit_pending = 1; } } void client_suspend_self() { struct winsize oldws, newws; /* Flush stdout and stderr buffers. */ if (buffer_len(&stdout_buffer) > 0) write(fileno(stdout), buffer_ptr(&stdout_buffer), buffer_len(&stdout_buffer)); if (buffer_len(&stderr_buffer) > 0) write(fileno(stderr), buffer_ptr(&stderr_buffer), buffer_len(&stderr_buffer)); leave_raw_mode(); /* * Free (and clear) the buffer to reduce the amount of data that gets * written to swap. */ buffer_free(&stdin_buffer); buffer_free(&stdout_buffer); buffer_free(&stderr_buffer); /* Save old window size. */ ioctl(fileno(stdin), TIOCGWINSZ, &oldws); /* Send the suspend signal to the program itself. */ kill(getpid(), SIGTSTP); /* Check if the window size has changed. */ if (ioctl(fileno(stdin), TIOCGWINSZ, &newws) >= 0 && (oldws.ws_row != newws.ws_row || oldws.ws_col != newws.ws_col || oldws.ws_xpixel != newws.ws_xpixel || oldws.ws_ypixel != newws.ws_ypixel)) received_window_change_signal = 1; /* OK, we have been continued by the user. Reinitialize buffers. */ buffer_init(&stdin_buffer); buffer_init(&stdout_buffer); buffer_init(&stderr_buffer); enter_raw_mode(); } void client_process_input(fd_set * readset) { int len, pid; char buf[8192], *s; /* * Read input from the server, and add any such data to the buffer of * the packet subsystem. */ if (FD_ISSET(connection_in, readset)) { /* Read as much as possible. */ len = read(connection_in, buf, sizeof(buf)); if (len == 0) { /* Received EOF. The remote host has closed the connection. */ snprintf(buf, sizeof buf, "Connection to %.300s closed by remote host.\r\n", host); buffer_append(&stderr_buffer, buf, strlen(buf)); stderr_bytes += strlen(buf); quit_pending = 1; return; } /* * 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) { /* An error has encountered. Perhaps there is a network problem. */ snprintf(buf, sizeof buf, "Read from remote host %.300s: %.100s\r\n", host, strerror(errno)); buffer_append(&stderr_buffer, buf, strlen(buf)); stderr_bytes += strlen(buf); quit_pending = 1; return; } packet_process_incoming(buf, len); } /* Read input from stdin. */ if (FD_ISSET(fileno(stdin), readset)) { /* Read as much as possible. */ len = read(fileno(stdin), buf, sizeof(buf)); if (len <= 0) { /* * Received EOF or error. They are treated * similarly, except that an error message is printed * if it was an error condition. */ if (len < 0) { snprintf(buf, sizeof buf, "read: %.100s\r\n", strerror(errno)); buffer_append(&stderr_buffer, buf, strlen(buf)); stderr_bytes += strlen(buf); } /* Mark that we have seen EOF. */ stdin_eof = 1; /* * Send an EOF message to the server unless there is * data in the buffer. If there is data in the * buffer, no message will be sent now. Code * elsewhere will send the EOF when the buffer * becomes empty if stdin_eof is set. */ if (buffer_len(&stdin_buffer) == 0) { packet_start(SSH_CMSG_EOF); packet_send(); } } else if (escape_char == -1) { /* * Normal successful read, and no escape character. * Just append the data to buffer. */ buffer_append(&stdin_buffer, buf, len); stdin_bytes += len; } else { /* * Normal, successful read. But we have an escape character * and have to process the characters one by one. */ unsigned int i; for (i = 0; i < len; i++) { unsigned char ch; /* Get one character at a time. */ ch = buf[i]; if (escape_pending) { /* We have previously seen an escape character. */ /* Clear the flag now. */ escape_pending = 0; /* Process the escaped character. */ switch (ch) { case '.': /* Terminate the connection. */ snprintf(buf, sizeof buf, "%c.\r\n", escape_char); buffer_append(&stderr_buffer, buf, strlen(buf)); stderr_bytes += strlen(buf); quit_pending = 1; return; case 'Z' - 64: /* Suspend the program. */ /* Print a message to that effect to the user. */ snprintf(buf, sizeof buf, "%c^Z\r\n", escape_char); buffer_append(&stderr_buffer, buf, strlen(buf)); stderr_bytes += strlen(buf); /* Restore terminal modes and suspend. */ client_suspend_self(); /* We have been continued. */ continue; case '&': /* * Detach the program (continue to serve connections, * but put in background and no more new connections). */ if (!stdin_eof) { /* * Sending SSH_CMSG_EOF alone does not always appear * to be enough. So we try to send an EOF character * first. */ packet_start(SSH_CMSG_STDIN_DATA); packet_put_string("\004", 1); packet_send(); /* Close stdin. */ stdin_eof = 1; if (buffer_len(&stdin_buffer) == 0) { packet_start(SSH_CMSG_EOF); packet_send(); } } /* Restore tty modes. */ leave_raw_mode(); /* Stop listening for new connections. */ channel_stop_listening(); printf("%c& [backgrounded]\n", escape_char); /* Fork into background. */ pid = fork(); if (pid < 0) { error("fork: %.100s", strerror(errno)); continue; } if (pid != 0) { /* This is the parent. */ /* The parent just exits. */ exit(0); } /* The child continues serving connections. */ continue; case '?': snprintf(buf, sizeof buf, "%c?\r\n\ Supported escape sequences:\r\n\ ~. - terminate connection\r\n\ ~^Z - suspend ssh\r\n\ ~# - list forwarded connections\r\n\ ~& - background ssh (when waiting for connections to terminate)\r\n\ ~? - this message\r\n\ ~~ - send the escape character by typing it twice\r\n\ (Note that escapes are only recognized immediately after newline.)\r\n", escape_char); buffer_append(&stderr_buffer, buf, strlen(buf)); continue; case '#': snprintf(buf, sizeof buf, "%c#\r\n", escape_char); buffer_append(&stderr_buffer, buf, strlen(buf)); s = channel_open_message(); buffer_append(&stderr_buffer, s, strlen(s)); xfree(s); continue; default: if (ch != escape_char) { /* * Escape character followed by non-special character. * Append both to the input buffer. */ buf[0] = escape_char; buf[1] = ch; buffer_append(&stdin_buffer, buf, 2); stdin_bytes += 2; continue; } /* * Note that escape character typed twice * falls through here; the latter gets processed * as a normal character below. */ break; } } else { /* * The previous character was not an escape char. Check if this * is an escape. */ if (last_was_cr && ch == escape_char) { /* It is. Set the flag and continue to next character. */ escape_pending = 1; continue; } } /* * Normal character. Record whether it was a newline, * and append it to the buffer. */ last_was_cr = (ch == '\r' || ch == '\n'); buf[0] = ch; buffer_append(&stdin_buffer, buf, 1); stdin_bytes += 1; continue; } } } } void client_process_output(fd_set * writeset) { int len; char buf[100]; /* Write buffered output to stdout. */ if (FD_ISSET(fileno(stdout), writeset)) { /* Write as much data as possible. */ len = write(fileno(stdout), buffer_ptr(&stdout_buffer), buffer_len(&stdout_buffer)); if (len <= 0) { if (errno == EAGAIN) len = 0; else { /* * An error or EOF was encountered. Put an * error message to stderr buffer. */ snprintf(buf, sizeof buf, "write stdout: %.50s\r\n", strerror(errno)); buffer_append(&stderr_buffer, buf, strlen(buf)); stderr_bytes += strlen(buf); quit_pending = 1; return; } } /* Consume printed data from the buffer. */ buffer_consume(&stdout_buffer, len); } /* Write buffered output to stderr. */ if (FD_ISSET(fileno(stderr), writeset)) { /* Write as much data as possible. */ len = write(fileno(stderr), buffer_ptr(&stderr_buffer), buffer_len(&stderr_buffer)); if (len <= 0) { if (errno == EAGAIN) len = 0; else { /* EOF or error, but can't even print error message. */ quit_pending = 1; return; } } /* Consume printed characters from the buffer. */ buffer_consume(&stderr_buffer, len); } } /* * Implements the interactive session with the server. This is called after * the user has been authenticated, and a command has been started on the * remote host. If escape_char != -1, it is the character used as an escape * character for terminating or suspending the session. */ int client_loop(int have_pty, int escape_char_arg) { extern Options options; double start_time, total_time; int len; char buf[100]; debug("Entering interactive session."); start_time = get_current_time(); /* Initialize variables. */ escape_pending = 0; last_was_cr = 1; exit_status = -1; stdin_eof = 0; buffer_high = 64 * 1024; 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; stdin_bytes = 0; stdout_bytes = 0; stderr_bytes = 0; quit_pending = 0; escape_char = escape_char_arg; /* Initialize buffers. */ buffer_init(&stdin_buffer); buffer_init(&stdout_buffer); buffer_init(&stderr_buffer); /* Set signal handlers to restore non-blocking mode. */ signal(SIGINT, signal_handler); signal(SIGQUIT, signal_handler); signal(SIGTERM, signal_handler); signal(SIGPIPE, SIG_IGN); if (have_pty) signal(SIGWINCH, window_change_handler); if (have_pty) enter_raw_mode(); /* Check if we should immediately send of on stdin. */ client_check_initial_eof_on_stdin(); /* Main loop of the client for the interactive session mode. */ while (!quit_pending) { fd_set readset, writeset; /* Process buffered packets sent by the server. */ client_process_buffered_input_packets(); /* * Make packets of buffered stdin data, and buffer them for * sending to the server. */ client_make_packets_from_stdin_data(); /* * Make packets from buffered channel data, and buffer them * for sending to the server. */ if (packet_not_very_much_data_to_write()) channel_output_poll(); /* * Check if the window size has changed, and buffer a message * about it to the server if so. */ client_check_window_change(); if (quit_pending) break; /* * Wait until we have something to do (something becomes * available on one of the descriptors). */ client_wait_until_can_do_something(&readset, &writeset); if (quit_pending) break; /* Do channel operations. */ channel_after_select(&readset, &writeset); /* * Process input from the connection and from stdin. Buffer * any data that is available. */ client_process_input(&readset); /* * Process output to stdout and stderr. Output to the * connection is processed elsewhere (above). */ client_process_output(&writeset); /* Send as much buffered packet data as possible to the sender. */ if (FD_ISSET(connection_out, &writeset)) packet_write_poll(); } /* Terminate the session. */ /* Stop watching for window change. */ if (have_pty) signal(SIGWINCH, SIG_DFL); /* Stop listening for connections. */ channel_stop_listening(); /* * In interactive mode (with pseudo tty) display a message indicating * that the connection has been closed. */ if (have_pty && options.log_level != SYSLOG_LEVEL_QUIET) { snprintf(buf, sizeof buf, "Connection to %.64s closed.\r\n", host); buffer_append(&stderr_buffer, buf, strlen(buf)); stderr_bytes += strlen(buf); } /* Output any buffered data for stdout. */ while (buffer_len(&stdout_buffer) > 0) { len = write(fileno(stdout), buffer_ptr(&stdout_buffer), buffer_len(&stdout_buffer)); if (len <= 0) { error("Write failed flushing stdout buffer."); break; } buffer_consume(&stdout_buffer, len); } /* Output any buffered data for stderr. */ while (buffer_len(&stderr_buffer) > 0) { len = write(fileno(stderr), buffer_ptr(&stderr_buffer), buffer_len(&stderr_buffer)); if (len <= 0) { error("Write failed flushing stderr buffer."); break; } buffer_consume(&stderr_buffer, len); } if (have_pty) leave_raw_mode(); /* Clear and free any buffers. */ memset(buf, 0, sizeof(buf)); buffer_free(&stdin_buffer); buffer_free(&stdout_buffer); buffer_free(&stderr_buffer); /* Report bytes transferred, and transfer rates. */ total_time = get_current_time() - start_time; debug("Transferred: stdin %lu, stdout %lu, stderr %lu bytes in %.1f seconds", stdin_bytes, stdout_bytes, stderr_bytes, total_time); if (total_time > 0) debug("Bytes per second: stdin %.1f, stdout %.1f, stderr %.1f", stdin_bytes / total_time, stdout_bytes / total_time, stderr_bytes / total_time); /* Return the exit status of the program. */ debug("Exit status %d", exit_status); return exit_status; }