/* * 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 = NULL, *writeset = NULL; int max_fd = 0; u_int nalloc = 0; int wait_status; /* Status returned by wait(). */ pid_t wait_pid; /* pid returned by wait(). */ int waiting_termination = 0; /* Have displayed waiting close message. */ u_int64_t max_time_milliseconds; u_int previous_stdout_buffer_bytes; u_int stdout_buffer_bytes; int type; debug("Entering interactive session."); /* Initialize the SIGCHLD kludge. */ child_terminated = 0; mysignal(SIGCHLD, sigchld_handler); if (!use_privsep) { signal(SIGTERM, sigterm_handler); signal(SIGINT, sigterm_handler); signal(SIGQUIT, sigterm_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); if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin)) fdin_is_tty = 1; connection_in = packet_get_connection_in(); connection_out = packet_get_connection_out(); notify_setup(); previous_stdout_buffer_bytes = 0; /* Set approximate I/O buffer size. */ if (packet_is_interactive()) buffer_high = 4096; else buffer_high = 64 * 1024; #if 0 /* Initialize max_fd to the maximum of the known file descriptors. */ max_fd = MAX(connection_in, connection_out); max_fd = MAX(max_fd, fdin); max_fd = MAX(max_fd, fdout); if (fderr != -1) max_fd = MAX(max_fd, fderr); #endif /* 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) { if (fdin != fdout) close(fdin); else shutdown(fdin, SHUT_WR); /* We will no longer send. */ 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... (press ~& to background)\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)); free(cp); } } max_fd = MAX(connection_in, connection_out); max_fd = MAX(max_fd, fdin); max_fd = MAX(max_fd, fdout); max_fd = MAX(max_fd, fderr); max_fd = MAX(max_fd, notify_pipe[0]); /* Sleep in select() until we can do something. */ wait_until_can_do_something(&readset, &writeset, &max_fd, &nalloc, max_time_milliseconds); if (received_sigterm) { logit("Exiting on signal %d", (int)received_sigterm); /* Clean up sessions, utmp, etc. */ cleanup_exit(255); } /* 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); } free(readset); free(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; channel_free_all(); /* We no longer want our SIGCHLD handler to be called. */ mysignal(SIGCHLD, SIG_DFL); while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0) if (errno != EINTR) packet_disconnect("wait: %.100s", strerror(errno)); if (wait_pid != pid) error("Strange, wait returned pid %ld, expected %ld", (long)wait_pid, (long)pid); /* 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 { type = packet_read(); } 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 */ }
/* process the characters one by one */ static int process_escapes(Buffer *bin, Buffer *bout, Buffer *berr, char *buf, int len) { char string[1024]; pid_t pid; int bytes = 0; u_int i; u_char ch; char *s; for (i = 0; i < len; i++) { /* 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(string, sizeof string, "%c.\r\n", escape_char); buffer_append(berr, string, strlen(string)); quit_pending = 1; return -1; case 'Z' - 64: /* Suspend the program. */ /* Print a message to that effect to the user. */ snprintf(string, sizeof string, "%c^Z [suspend ssh]\r\n", escape_char); buffer_append(berr, string, strlen(string)); /* Restore terminal modes and suspend. */ client_suspend_self(bin, bout, berr); /* We have been continued. */ continue; case 'B': if (compat20) { snprintf(string, sizeof string, "%cB\r\n", escape_char); buffer_append(berr, string, strlen(string)); channel_request_start(session_ident, "break", 0); packet_put_int(1000); packet_send(); } continue; case 'R': if (compat20) { if (datafellows & SSH_BUG_NOREKEY) logit("Server does not support re-keying"); else need_rekeying = 1; } continue; case '&': /* * Detach the program (continue to serve connections, * but put in background and no more new connections). */ /* Restore tty modes. */ leave_raw_mode(); /* Stop listening for new connections. */ channel_stop_listening(); snprintf(string, sizeof string, "%c& [backgrounded]\n", escape_char); buffer_append(berr, string, strlen(string)); /* 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. */ if (compat20) { buffer_append(bin, "\004", 1); /* fake EOF on stdin */ return -1; } else 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(bin) == 0) { packet_start(SSH_CMSG_EOF); packet_send(); } } continue; case '?': snprintf(string, sizeof string, "%c?\r\n\ Supported escape sequences:\r\n\ %c. - terminate connection\r\n\ %cB - send a BREAK to the remote system\r\n\ %cC - open a command line\r\n\ %cR - Request rekey (SSH protocol 2 only)\r\n\ %c^Z - suspend ssh\r\n\ %c# - list forwarded connections\r\n\ %c& - background ssh (when waiting for connections to terminate)\r\n\ %c? - this message\r\n\ %c%c - send the escape character by typing it twice\r\n\ (Note that escapes are only recognized immediately after newline.)\r\n", escape_char, escape_char, escape_char, escape_char, escape_char, escape_char, escape_char, escape_char, escape_char, escape_char, escape_char); buffer_append(berr, string, strlen(string)); continue; case '#': snprintf(string, sizeof string, "%c#\r\n", escape_char); buffer_append(berr, string, strlen(string)); s = channel_open_message(); buffer_append(berr, s, strlen(s)); xfree(s); continue; case 'C': process_cmdline(); continue; default: if (ch != escape_char) { buffer_put_char(bin, escape_char); bytes++; } /* Escaped characters fall through here */ 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'); buffer_put_char(bin, ch); bytes++; }