telnet_server.c

/***************************************************************************
 *   Copyright (C) 2005 by Dominic Rath                                    *
 *   Dominic.Rath@gmx.de                                                   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "replacements.h"

#include "telnet_server.h"

#include "server.h"
#include "log.h"
#include "command.h"
#include "target.h"
#include "target_request.h"

#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <ctype.h>

static unsigned short telnet_port = 0;

int handle_exit_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc);
int handle_telnet_port_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc);

static char *negotiate =
		"\xFF\xFB\x03"		/* IAC WILL Suppress Go Ahead */
		"\xFF\xFB\x01"		/* IAC WILL Echo */
		"\xFF\xFD\x03"		/* IAC DO Suppress Go Ahead */
		"\xFF\xFE\x01";		/* IAC DON'T Echo */
		
#define CTRL(c) (c - '@')
	
void telnet_prompt(connection_t *connection)
{
	telnet_connection_t *t_con = connection->priv;

	write_socket(connection->fd, t_con->prompt, strlen(t_con->prompt));
}

int telnet_outputline(connection_t *connection, char* line)
{
	write_socket(connection->fd, line, strlen(line));
	return write_socket(connection->fd, "\r\n\0", 3);
}

int telnet_output(struct command_context_s *cmd_ctx, char* line)
{
	connection_t *connection = cmd_ctx->output_handler_priv;
	
	write_socket(connection->fd, line, strlen(line));
	write_socket(connection->fd, "\r\n\0", 3);
	
	return ERROR_OK;
}

void telnet_log_callback(void *privData, const char *file, int line, 
		const char *function, const char *format, va_list args)
{
	connection_t *connection = (connection_t *)privData;
	char *t = allocPrintf(format, args);
	if (t == NULL)
		return;
	
	telnet_outputline(connection, t);
	
	free(t);
}

int telnet_target_callback_event_handler(struct target_s *target, enum target_event event, void *priv)
{
	struct command_context_s *cmd_ctx = priv;
	connection_t *connection = cmd_ctx->output_handler_priv;
	telnet_connection_t *t_con = connection->priv;
	char buffer[512];
	
	switch (event)
	{
		case TARGET_EVENT_HALTED:
			command_print(cmd_ctx, "Target %i halted", get_num_by_target(target));
			target->type->arch_state(target, buffer, 512);
			buffer[511] = 0;
			command_print(cmd_ctx, "%s", buffer);
			if (!t_con->suppress_prompt)
				telnet_prompt(connection);
			break;
		case TARGET_EVENT_RESUMED:
			command_print(cmd_ctx, "Target %i resumed", get_num_by_target(target));
			if (!t_con->suppress_prompt)
				telnet_prompt(connection);
			break;
		default:
			break;
	}

	return ERROR_OK;
}

int telnet_new_connection(connection_t *connection)
{
	telnet_connection_t *telnet_connection = malloc(sizeof(telnet_connection_t));
	telnet_service_t *telnet_service = connection->service->priv;
	int i;
	
	connection->priv = telnet_connection;
	
	/* initialize telnet connection information */
	telnet_connection->line_size = 0;
	telnet_connection->line_cursor = 0;
	telnet_connection->option_size = 0;
	telnet_connection->prompt = strdup("> ");
	telnet_connection->suppress_prompt = 0;
	telnet_connection->state = TELNET_STATE_DATA;
	
	/* output goes through telnet connection */
	command_set_output_handler(connection->cmd_ctx, telnet_output, connection);
	
	/* negotiate telnet options */
	write_socket(connection->fd, negotiate, strlen(negotiate));
	
	/* print connection banner */
	if (telnet_service->banner)
	{
		write_socket(connection->fd, telnet_service->banner, strlen(telnet_service->banner));
		write_socket(connection->fd, "\r\n\0", 3);
	}
	
	telnet_prompt(connection);
	
	/* initialize history */
	for (i = 0; i < TELNET_LINE_HISTORY_SIZE; i++)
	{
		telnet_connection->history[i] = NULL;
	}
	telnet_connection->next_history = 0;
	telnet_connection->current_history = 0;
	
	target_register_event_callback(telnet_target_callback_event_handler, connection->cmd_ctx);
	
	return ERROR_OK;
}

void telnet_clear_line(connection_t *connection, telnet_connection_t *t_con)
{
	/* move to end of line */
	if (t_con->line_cursor < t_con->line_size)
	{
		write_socket(connection->fd, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
	}
							
	/* backspace, overwrite with space, backspace */
	while (t_con->line_size > 0)
	{
		write_socket(connection->fd, "\b \b", 3);
		t_con->line_size--;
	}
	t_con->line_cursor = 0;
}

int telnet_input(connection_t *connection)
{
	int bytes_read;
	char buffer[TELNET_BUFFER_SIZE];
	char *buf_p;
	telnet_connection_t *t_con = connection->priv;
	command_context_t *command_context = connection->cmd_ctx;
	
	bytes_read = read_socket(connection->fd, buffer, TELNET_BUFFER_SIZE);
	
	if (bytes_read == 0)
		return ERROR_SERVER_REMOTE_CLOSED;
	else if (bytes_read == -1)
	{
		ERROR("error during read: %s", strerror(errno));
		return ERROR_SERVER_REMOTE_CLOSED;
	}
	
	buf_p = buffer;
	while (bytes_read)
	{
		switch (t_con->state)
		{
			case TELNET_STATE_DATA:
				if (*buf_p == '\xff')
				{
					t_con->state = TELNET_STATE_IAC;
				}
				else
				{
					if (isprint(*buf_p)) /* printable character */
					{
						write_socket(connection->fd, buf_p, 1);
						if (t_con->line_cursor == t_con->line_size)
						{
							t_con->line[t_con->line_size++] = *buf_p;
							t_con->line_cursor++;
						}
						else
						{
							int i;
							memmove(t_con->line + t_con->line_cursor + 1, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
							t_con->line[t_con->line_cursor++] = *buf_p;
							t_con->line_size++;
							write_socket(connection->fd, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
							for (i = t_con->line_cursor; i < t_con->line_size; i++)
							{
								write_socket(connection->fd, "\b", 1);
							}
						}
					}
					else /* non-printable */
					{
						if (*buf_p == 0x1b) /* escape */
						{
							t_con->state = TELNET_STATE_ESCAPE;
							t_con->last_escape = '\x00';
						}
						else if ((*buf_p == 0xd) || (*buf_p == 0xa)) /* CR/LF */
						{
							int retval;
							
							/* skip over combinations with CR/LF + NUL */
							if (((*(buf_p + 1) == 0xa) || (*(buf_p + 1) == 0xd)) && (bytes_read > 1))
							{
								buf_p++;
								bytes_read--;
							}
							if ((*(buf_p + 1) == 0) && (bytes_read > 1))
							{
								buf_p++;
								bytes_read--;
							}
							t_con->line[t_con->line_size] = 0;
							
							write_socket(connection->fd, "\r\n\x00", 3);
							
							if (strcmp(t_con->line, "history") == 0)
							{
								int i;
								for (i = 0; i < TELNET_LINE_HISTORY_SIZE; i++)
								{
									if (t_con->history[i])
									{
										write_socket(connection->fd, t_con->history[i], strlen(t_con->history[i]));
										write_socket(connection->fd, "\r\n\x00", 3);
									}
								}
								telnet_prompt(connection);
								t_con->line_size = 0;
								t_con->line_cursor = 0;
								continue;
							}
							
							log_setCallback(telnet_log_callback, connection);
							t_con->suppress_prompt = 1;
							
							if ((retval = command_run_line(command_context, t_con->line)) != ERROR_OK)
							{
								if (retval == ERROR_COMMAND_CLOSE_CONNECTION)
								{
									return ERROR_SERVER_REMOTE_CLOSED;
								}
							}
							
							t_con->suppress_prompt = 0;
							
							/* Save only non-blank lines in the history */
							if (t_con->line_size > 0)
							{
								/* if the history slot is already taken, free it */
								if (t_con->history[t_con->next_history])
								{
									free(t_con->history[t_con->next_history]);
								}
		
								/* add line to history */
								t_con->history[t_con->next_history] = strdup(t_con->line);

								/* wrap history at TELNET_LINE_HISTORY_SIZE */
								t_con->next_history = (t_con->next_history + 1) % TELNET_LINE_HISTORY_SIZE;
							
								/* current history line starts at the new entry */
								t_con->current_history = t_con->next_history;
							
								if (t_con->history[t_con->current_history])
								{
									free(t_con->history[t_con->current_history]);
								}
								t_con->history[t_con->current_history] = strdup("");
							}
							
							/* output prompt after command */
							telnet_prompt(connection);
							
							t_con->line_size = 0;
							t_con->line_cursor = 0;
						}
						else if ((*buf_p == 0x7f) || (*buf_p == 0x8)) /* delete character */
						{
							if (t_con->line_cursor > 0)
							{
								if (t_con->line_cursor != t_con->line_size)
								{
									int i;
									write_socket(connection->fd, "\b", 1);
									t_con->line_cursor--;
									t_con->line_size--;
									memmove(t_con->line + t_con->line_cursor, t_con->line + t_con->line_cursor + 1, t_con->line_size - t_con->line_cursor);
									
									write_socket(connection->fd, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
									write_socket(connection->fd, " \b", 2);
									for (i = t_con->line_cursor; i < t_con->line_size; i++)
									{
										write_socket(connection->fd, "\b", 1);
									}
								}
								else
								{
									t_con->line_size--;
									t_con->line_cursor--;
									/* back space: move the 'printer' head one char back, overwrite with space, move back again */
									write_socket(connection->fd, "\b \b", 3);
								}
							}
						}
						else if (*buf_p == 0x15) /* clear line */
						{
							telnet_clear_line(connection, t_con);
						}
						else if (*buf_p == CTRL('B')) /* cursor left */
						{
							if (t_con->line_cursor > 0)
							{
								write_socket(connection->fd, "\b", 1);
								t_con->line_cursor--;
							}
							t_con->state = TELNET_STATE_DATA;
						}
						else if (*buf_p == CTRL('F')) /* cursor right */
						{
							if (t_con->line_cursor < t_con->line_size)
							{
								write_socket(connection->fd, t_con->line + t_con->line_cursor++, 1);
							}
							t_con->state = TELNET_STATE_DATA;
						}
						else
						{
							DEBUG("unhandled nonprintable: %2.2x", *buf_p);
						}
					}
				}
				break;
			case TELNET_STATE_IAC:
				switch (*buf_p)
				{
					case '\xfe':
						t_con->state = TELNET_STATE_DONT;
						break;
					case '\xfd':
						t_con->state = TELNET_STATE_DO;
						break;
					case '\xfc':
						t_con->state = TELNET_STATE_WONT;
						break;
					case '\xfb':
						t_con->state = TELNET_STATE_WILL;
						break;
				}
				break;
			case TELNET_STATE_SB:
				break;
			case TELNET_STATE_SE:
				break;
			case TELNET_STATE_WILL:
			case TELNET_STATE_WONT:
			case TELNET_STATE_DO:
			case TELNET_STATE_DONT:
				t_con->state = TELNET_STATE_DATA;
				break;
			case TELNET_STATE_ESCAPE:
				if (t_con->last_escape == '[')
				{
					if (*buf_p == 'D') /* cursor left */
					{
						if (t_con->line_cursor > 0)
						{
							write_socket(connection->fd, "\b", 1);
							t_con->line_cursor--;
						}
						t_con->state = TELNET_STATE_DATA;
					}
					else if (*buf_p == 'C') /* cursor right */
					{
						if (t_con->line_cursor < t_con->line_size)
						{
							write_socket(connection->fd, t_con->line + t_con->line_cursor++, 1);
						}
						t_con->state = TELNET_STATE_DATA;
					}
					else if (*buf_p == 'A') /* cursor up */
					{
						int last_history = (t_con->current_history > 0) ? t_con->current_history - 1 : TELNET_LINE_HISTORY_SIZE-1;
						if (t_con->history[last_history])
						{
							telnet_clear_line(connection, t_con);
							t_con->line_size = strlen(t_con->history[last_history]);
							t_con->line_cursor = t_con->line_size;
							memcpy(t_con->line, t_con->history[last_history], t_con->line_size + 1);
							write_socket(connection->fd, t_con->line, t_con->line_size);
							t_con->current_history = last_history;
						}
						t_con->state = TELNET_STATE_DATA;
					}
					else if (*buf_p == 'B') /* cursor down */
					{
						int next_history = (t_con->current_history + 1) % TELNET_LINE_HISTORY_SIZE;
						if (t_con->history[next_history])
						{
							telnet_clear_line(connection, t_con);
							t_con->line_size = strlen(t_con->history[next_history]);
							t_con->line_cursor = t_con->line_size;
							memcpy(t_con->line, t_con->history[next_history], t_con->line_size + 1);
							write_socket(connection->fd, t_con->line, t_con->line_size);
							t_con->current_history = next_history;
						}
						t_con->state = TELNET_STATE_DATA;
					}
					else if (*buf_p == '3')
					{
						t_con->last_escape = *buf_p;
					}
					else
					{
						t_con->state = TELNET_STATE_DATA;
					}
				}
				else if (t_con->last_escape == '3')
				{
					/* Remove character */
					if (*buf_p == '~')
					{
						if (t_con->line_cursor < t_con->line_size)
						{
							int i;
							t_con->line_size--;
							/* remove char from line buffer */
							memmove(t_con->line + t_con->line_cursor, t_con->line + t_con->line_cursor + 1, t_con->line_size - t_con->line_cursor);
							
							/* print remainder of buffer */
							write_socket(connection->fd, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
							/* overwrite last char with whitespace */
							write_socket(connection->fd, " \b", 2);
							
							/* move back to cursor position*/
							for (i = t_con->line_cursor; i < t_con->line_size; i++)
							{
								write_socket(connection->fd, "\b", 1);
							}
						}
							
						t_con->state = TELNET_STATE_DATA;
					}
					else
					{
						t_con->state = TELNET_STATE_DATA;
					}
				}
				else if (t_con->last_escape == '\x00')
				{
					if (*buf_p == '[')
					{
						t_con->last_escape = *buf_p;
					}
					else
					{
						t_con->state = TELNET_STATE_DATA;
					}
				}
				else
				{
					ERROR("BUG: unexpected value in t_con->last_escape");
					t_con->state = TELNET_STATE_DATA;
				}
				
				break;
			default:
				ERROR("unknown telnet state");
				exit(-1);
		}

		bytes_read--;
		buf_p++;
	}
	
	return ERROR_OK;
}

int telnet_connection_closed(connection_t *connection)
{
	telnet_connection_t *t_con = connection->priv;
	int i;
	
	if (t_con->prompt)
	{
		free(t_con->prompt);
		t_con->prompt = NULL;
	}
	
	for (i = 0; i < TELNET_LINE_HISTORY_SIZE; i++)
	{
		if (t_con->history[i])
		{
			free(t_con->history[i]);
			t_con->history[i] = NULL;
		}
	}
	
	/* if this connection registered a debug-message receiver delete it */
	delete_debug_msg_receiver(connection->cmd_ctx, NULL);
	
	if (connection->priv)
	{
		free(connection->priv);
		connection->priv = NULL;
	}
	else
	{
		ERROR("BUG: connection->priv == NULL");
	}
	
	target_unregister_event_callback(telnet_target_callback_event_handler, connection->cmd_ctx);

	return ERROR_OK;
}

int telnet_set_prompt(connection_t *connection, char *prompt)
{
	telnet_connection_t *t_con = connection->priv;

	t_con->prompt = strdup(prompt);
	
	return ERROR_OK;
}

int telnet_init(char *banner)
{
	telnet_service_t *telnet_service = malloc(sizeof(telnet_service_t));
	
	if (telnet_port == 0)
	{
		WARNING("no telnet port specified, using default port 4444");
		telnet_port = 4444;
	}
	
	telnet_service->banner = banner;
	
	add_service("telnet", CONNECTION_TELNET, telnet_port, 1, telnet_new_connection, telnet_input, telnet_connection_closed, telnet_service);
	
	return ERROR_OK;
}

int telnet_register_commands(command_context_t *command_context)
{
	register_command(command_context, NULL, "exit", handle_exit_command,
					 COMMAND_EXEC, "exit telnet session");
	
	register_command(command_context, NULL, "telnet_port", handle_telnet_port_command,
					 COMMAND_CONFIG, "");
	
	return ERROR_OK;
}

/* daemon configuration command telnet_port */
int handle_telnet_port_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc)
{
	if (argc == 0)
		return ERROR_OK;

	/* only if the port wasn't overwritten by cmdline */
	if (telnet_port == 0)
		telnet_port = strtoul(args[0], NULL, 0);

	return ERROR_OK;
}

int handle_exit_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc)
{
	return ERROR_COMMAND_CLOSE_CONNECTION;
}