view cli-runopts.c @ 1861:2b3a8026a6ce

Add re-exec for server This allows ASLR to re-randomize the address space for every connection, preventing some vulnerabilities from being exploitable by repeated probing. Overhead (memory and time) is yet to be confirmed. At present this is only enabled on Linux. Other BSD platforms with fexecve() would probably also work though have not been tested.
author Matt Johnston <matt@ucc.asn.au>
date Sun, 30 Jan 2022 10:14:56 +0800
parents 94dc11094e26
children 33363a68784d
line wrap: on
line source

/*
 * Dropbear - a SSH2 server
 * 
 * Copyright (c) 2002,2003 Matt Johnston
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE. */

#include "includes.h"
#include "runopts.h"
#include "signkey.h"
#include "buffer.h"
#include "dbutil.h"
#include "algo.h"
#include "tcpfwd.h"
#include "list.h"

cli_runopts cli_opts; /* GLOBAL */

static void printhelp(void);
static void parse_hostname(const char* orighostarg);
static void parse_multihop_hostname(const char* orighostarg, const char* argv0);
static void fill_own_user(void);
#if DROPBEAR_CLI_PUBKEY_AUTH
static void loadidentityfile(const char* filename, int warnfail);
#endif
#if DROPBEAR_CLI_ANYTCPFWD
static void addforward(const char* str, m_list *fwdlist);
#endif
#if DROPBEAR_CLI_NETCAT
static void add_netcat(const char *str);
#endif
static void add_extendedopt(const char *str);

static void printhelp() {

	fprintf(stderr, "Dropbear SSH client v%s https://matt.ucc.asn.au/dropbear/dropbear.html\n"
#if DROPBEAR_CLI_MULTIHOP
					"Usage: %s [options] [user@]host[/port][,[user@]host/port],...] [command]\n"
#else
					"Usage: %s [options] [user@]host[/port] [command]\n"
#endif
					"-p <remoteport>\n"
					"-l <username>\n"
					"-t    Allocate a pty\n"
					"-T    Don't allocate a pty\n"
					"-N    Don't run a remote command\n"
					"-f    Run in background after auth\n"
					"-y    Always accept remote host key if unknown\n"
					"-y -y Don't perform any remote host key checking (caution)\n"
					"-s    Request a subsystem (use by external sftp)\n"
					"-o option     Set option in OpenSSH-like format ('-o help' to list options)\n"
#if DROPBEAR_CLI_PUBKEY_AUTH
					"-i <identityfile>   (multiple allowed, default %s)\n"
#endif
#if DROPBEAR_CLI_AGENTFWD
					"-A    Enable agent auth forwarding\n"
#endif
#if DROPBEAR_CLI_LOCALTCPFWD
					"-L <[listenaddress:]listenport:remotehost:remoteport> Local port forwarding\n"
					"-g    Allow remote hosts to connect to forwarded ports\n"
#endif
#if DROPBEAR_CLI_REMOTETCPFWD
					"-R <[listenaddress:]listenport:remotehost:remoteport> Remote port forwarding\n"
#endif
					"-W <receive_window_buffer> (default %d, larger may be faster, max 10MB)\n"
					"-K <keepalive>  (0 is never, default %d)\n"
					"-I <idle_timeout>  (0 is never, default %d)\n"
#if DROPBEAR_CLI_NETCAT
					"-B <endhost:endport> Netcat-alike forwarding\n"
#endif				
#if DROPBEAR_CLI_PROXYCMD
					"-J <proxy_program> Use program pipe rather than TCP connection\n"
#endif
#if DROPBEAR_USER_ALGO_LIST
					"-c <cipher list> Specify preferred ciphers ('-c help' to list options)\n"
					"-m <MAC list> Specify preferred MACs for packet verification (or '-m help')\n"
#endif
					"-b    [bind_address][:bind_port]\n"
					"-V    Version\n"
#if DEBUG_TRACE
					"-v    verbose (compiled with DEBUG_TRACE)\n"
#endif
					,DROPBEAR_VERSION, cli_opts.progname,
#if DROPBEAR_CLI_PUBKEY_AUTH
					DROPBEAR_DEFAULT_CLI_AUTHKEY,
#endif
					DEFAULT_RECV_WINDOW, DEFAULT_KEEPALIVE, DEFAULT_IDLE_TIMEOUT);
					
}

void cli_getopts(int argc, char ** argv) {
	unsigned int i, j;
	char ** next = NULL;
	enum {
		OPT_EXTENDED_OPTIONS,
#if DROPBEAR_CLI_PUBKEY_AUTH
		OPT_AUTHKEY,
#endif
#if DROPBEAR_CLI_LOCALTCPFWD
		OPT_LOCALTCPFWD,
#endif
#if DROPBEAR_CLI_REMOTETCPFWD
		OPT_REMOTETCPFWD,
#endif
#if DROPBEAR_CLI_NETCAT
		OPT_NETCAT,
#endif
		/* a flag (no arg) if 'next' is NULL, a string-valued option otherwise */
		OPT_OTHER
	} opt;
	unsigned int cmdlen;

	char* recv_window_arg = NULL;
	char* keepalive_arg = NULL;
	char* idle_timeout_arg = NULL;
	char *host_arg = NULL;
	char *bind_arg = NULL;
	char c;

	/* see printhelp() for options */
	cli_opts.progname = argv[0];
	cli_opts.remotehost = NULL;
	cli_opts.remoteport = NULL;
	cli_opts.username = NULL;
	cli_opts.cmd = NULL;
	cli_opts.no_cmd = 0;
	cli_opts.backgrounded = 0;
	cli_opts.wantpty = 9; /* 9 means "it hasn't been touched", gets set later */
	cli_opts.always_accept_key = 0;
	cli_opts.no_hostkey_check = 0;
	cli_opts.is_subsystem = 0;
#if DROPBEAR_CLI_PUBKEY_AUTH
	cli_opts.privkeys = list_new();
#endif
#if DROPBEAR_CLI_ANYTCPFWD
	cli_opts.exit_on_fwd_failure = 0;
#endif
	cli_opts.disable_trivial_auth = 0;
#if DROPBEAR_CLI_LOCALTCPFWD
	cli_opts.localfwds = list_new();
	opts.listen_fwd_all = 0;
#endif
#if DROPBEAR_CLI_REMOTETCPFWD
	cli_opts.remotefwds = list_new();
#endif
#if DROPBEAR_CLI_AGENTFWD
	cli_opts.agent_fwd = 0;
	cli_opts.agent_fd = -1;
	cli_opts.agent_keys_loaded = 0;
#endif
#if DROPBEAR_CLI_PROXYCMD
	cli_opts.proxycmd = NULL;
#endif
	cli_opts.bind_address = NULL;
	cli_opts.bind_port = NULL;
#ifndef DISABLE_ZLIB
	opts.compress_mode = DROPBEAR_COMPRESS_ON;
#endif
#if DROPBEAR_USER_ALGO_LIST
	opts.cipher_list = NULL;
	opts.mac_list = NULL;
#endif
#ifndef DISABLE_SYSLOG
	opts.usingsyslog = 0;
#endif
	/* not yet
	opts.ipv4 = 1;
	opts.ipv6 = 1;
	*/
	opts.recv_window = DEFAULT_RECV_WINDOW;
	opts.keepalive_secs = DEFAULT_KEEPALIVE;
	opts.idle_timeout_secs = DEFAULT_IDLE_TIMEOUT;

	fill_own_user();

	for (i = 1; i < (unsigned int)argc; i++) {
		/* Handle non-flag arguments such as hostname or commands for the remote host */
		if (argv[i][0] != '-')
		{
			if (host_arg == NULL) {
				host_arg = argv[i];
				continue;
			}
			/* Commands to pass to the remote host. No more flag handling,
			commands are consumed below */
			break;
		}

		/* Begins with '-' */
		opt = OPT_OTHER;
		for (j = 1; (c = argv[i][j]) != '\0' && !next && opt == OPT_OTHER; j++) {
			switch (c) {
				case 'y': /* always accept the remote hostkey */
					if (cli_opts.always_accept_key) {
						/* twice means no checking at all */
						cli_opts.no_hostkey_check = 1;
					}
					cli_opts.always_accept_key = 1;
					break;
				case 'p': /* remoteport */
					next = (char**)&cli_opts.remoteport;
					break;
#if DROPBEAR_CLI_PUBKEY_AUTH
				case 'i': /* an identityfile */
					opt = OPT_AUTHKEY;
					break;
#endif
				case 't': /* we want a pty */
					cli_opts.wantpty = 1;
					break;
				case 'T': /* don't want a pty */
					cli_opts.wantpty = 0;
					break;
				case 'N':
					cli_opts.no_cmd = 1;
					break;
				case 'f':
					cli_opts.backgrounded = 1;
					break;
				case 's':
					cli_opts.is_subsystem = 1;
					break;
				case 'o':
					opt = OPT_EXTENDED_OPTIONS;
					break;
#if DROPBEAR_CLI_LOCALTCPFWD
				case 'L':
					opt = OPT_LOCALTCPFWD;
					break;
				case 'g':
					opts.listen_fwd_all = 1;
					break;
#endif
#if DROPBEAR_CLI_REMOTETCPFWD
				case 'R':
					opt = OPT_REMOTETCPFWD;
					break;
#endif
#if DROPBEAR_CLI_NETCAT
				case 'B':
					opt = OPT_NETCAT;
					break;
#endif
#if DROPBEAR_CLI_PROXYCMD
				case 'J':
					next = &cli_opts.proxycmd;
					break;
#endif
				case 'l':
					next = &cli_opts.username;
					break;
				case 'h':
					printhelp();
					exit(EXIT_SUCCESS);
					break;
				case 'u':
					/* backwards compatibility with old urandom option */
					break;
				case 'W':
					next = &recv_window_arg;
					break;
				case 'K':
					next = &keepalive_arg;
					break;
				case 'I':
					next = &idle_timeout_arg;
					break;
#if DROPBEAR_CLI_AGENTFWD
				case 'A':
					cli_opts.agent_fwd = 1;
					break;
#endif
#if DROPBEAR_USER_ALGO_LIST
				case 'c':
					next = &opts.cipher_list;
					break;
				case 'm':
					next = &opts.mac_list;
					break;
#endif
#if DEBUG_TRACE
				case 'v':
					debug_trace = 1;
					break;
#endif
				case 'F':
				case 'e':
#if !DROPBEAR_USER_ALGO_LIST
				case 'c':
				case 'm':
#endif
				case 'D':
#if !DROPBEAR_CLI_REMOTETCPFWD
				case 'R':
#endif
#if !DROPBEAR_CLI_LOCALTCPFWD
				case 'L':
#endif
				case 'V':
					print_version();
					exit(EXIT_SUCCESS);
					break;
				case 'b':
					next = &bind_arg;
					break;
				default:
					fprintf(stderr,
						"WARNING: Ignoring unknown option -%c\n", c);
					break;
			} /* Switch */
		}

		if (!next && opt == OPT_OTHER) /* got a flag */
			continue;

		if (c == '\0') {
			i++;
			j = 0;
			if (!argv[i])
				dropbear_exit("Missing argument");
		}

		if (opt == OPT_EXTENDED_OPTIONS) {
			TRACE(("opt extended"))
			add_extendedopt(&argv[i][j]);
		}
		else
#if DROPBEAR_CLI_PUBKEY_AUTH
		if (opt == OPT_AUTHKEY) {
			TRACE(("opt authkey"))
			loadidentityfile(&argv[i][j], 1);
		}
		else
#endif
#if DROPBEAR_CLI_REMOTETCPFWD
		if (opt == OPT_REMOTETCPFWD) {
			TRACE(("opt remotetcpfwd"))
			addforward(&argv[i][j], cli_opts.remotefwds);
		}
		else
#endif
#if DROPBEAR_CLI_LOCALTCPFWD
		if (opt == OPT_LOCALTCPFWD) {
			TRACE(("opt localtcpfwd"))
			addforward(&argv[i][j], cli_opts.localfwds);
		}
		else
#endif
#if DROPBEAR_CLI_NETCAT
		if (opt == OPT_NETCAT) {
			TRACE(("opt netcat"))
			add_netcat(&argv[i][j]);
		}
		else
#endif
		if (next) {
			/* The previous flag set a value to assign */
			*next = &argv[i][j];
			if (*next == NULL)
				dropbear_exit("Invalid null argument");
			next = NULL;
		}
	}

#if DROPBEAR_USER_ALGO_LIST
	/* -c help doesn't need a hostname */
	parse_ciphers_macs();
#endif

	/* Done with options/flags; now handle the hostname (which may not
	 * start with a hyphen) and optional command */

	if (host_arg == NULL) { /* missing hostname */
		printhelp();
		exit(EXIT_FAILURE);
	}
	TRACE(("host is: %s", host_arg))

	if (i < (unsigned int)argc) {
		/* Build the command to send */
		cmdlen = 0;
		for (j = i; j < (unsigned int)argc; j++)
			cmdlen += strlen(argv[j]) + 1; /* +1 for spaces */

		/* Allocate the space */
		cli_opts.cmd = (char*)m_malloc(cmdlen);
		cli_opts.cmd[0] = '\0';

		/* Append all the bits */
		for (j = i; j < (unsigned int)argc; j++) {
			strlcat(cli_opts.cmd, argv[j], cmdlen);
			strlcat(cli_opts.cmd, " ", cmdlen);
		}
		/* It'll be null-terminated here */
		TRACE(("cmd is: %s", cli_opts.cmd))
	}

	/* And now a few sanity checks and setup */

#if DROPBEAR_CLI_PROXYCMD                                                                                                                                   
	if (cli_opts.proxycmd) {
		/* To match the common path of m_freeing it */
		cli_opts.proxycmd = m_strdup(cli_opts.proxycmd);
	}
#endif

	if (cli_opts.remoteport == NULL) {
		cli_opts.remoteport = "22";
	}

	if (bind_arg) {
		/* split [host][:port] */
		char *port = strrchr(bind_arg, ':');
		if (port) {
			cli_opts.bind_port = m_strdup(port+1);
			*port = '\0';
		}
		if (strlen(bind_arg) > 0) {
			cli_opts.bind_address = m_strdup(bind_arg);
		}
	}

	/* If not explicitly specified with -t or -T, we don't want a pty if
	 * there's a command, but we do otherwise */
	if (cli_opts.wantpty == 9) {
		if (cli_opts.cmd == NULL) {
			cli_opts.wantpty = 1;
		} else {
			cli_opts.wantpty = 0;
		}
	}

	if (cli_opts.backgrounded && cli_opts.cmd == NULL
			&& cli_opts.no_cmd == 0) {
		dropbear_exit("Command required for -f");
	}

	if (recv_window_arg) {
		parse_recv_window(recv_window_arg);
	}
	if (keepalive_arg) {
		unsigned int val;
		if (m_str_to_uint(keepalive_arg, &val) == DROPBEAR_FAILURE) {
			dropbear_exit("Bad keepalive '%s'", keepalive_arg);
		}
		opts.keepalive_secs = val;
	}

	if (idle_timeout_arg) {
		unsigned int val;
		if (m_str_to_uint(idle_timeout_arg, &val) == DROPBEAR_FAILURE) {
			dropbear_exit("Bad idle_timeout '%s'", idle_timeout_arg);
		}
		opts.idle_timeout_secs = val;
	}

#if DROPBEAR_CLI_NETCAT
	if (cli_opts.cmd && cli_opts.netcat_host) {
		dropbear_log(LOG_INFO, "Ignoring command '%s' in netcat mode", cli_opts.cmd);
	}
#endif

#if (DROPBEAR_CLI_PUBKEY_AUTH)
	{
		char *expand_path = expand_homedir_path(DROPBEAR_DEFAULT_CLI_AUTHKEY);
		loadidentityfile(expand_path, 0);
		m_free(expand_path);
	}
#endif

	/* The hostname gets set up last, since
	 * in multi-hop mode it will require knowledge
	 * of other flags such as -i */
#if DROPBEAR_CLI_MULTIHOP
	parse_multihop_hostname(host_arg, argv[0]);
#else
	parse_hostname(host_arg);
#endif
}

#if DROPBEAR_CLI_PUBKEY_AUTH
static void loadidentityfile(const char* filename, int warnfail) {
	sign_key *key;
	enum signkey_type keytype;

	TRACE(("loadidentityfile %s", filename))

	key = new_sign_key();
	keytype = DROPBEAR_SIGNKEY_ANY;
	if ( readhostkey(filename, key, &keytype) != DROPBEAR_SUCCESS ) {
		if (warnfail) {
			dropbear_log(LOG_WARNING, "Failed loading keyfile '%s'\n", filename);
		}
		sign_key_free(key);
	} else {
		key->type = keytype;
		key->source = SIGNKEY_SOURCE_RAW_FILE;
		key->filename = m_strdup(filename);
		list_append(cli_opts.privkeys, key);
	}
}
#endif

#if DROPBEAR_CLI_MULTIHOP

static char*
multihop_passthrough_args() {
	char *ret;
	int total;
	unsigned int len = 0;
	m_list_elem *iter;
	/* Fill out -i, -y, -W options that make sense for all
	 * the intermediate processes */
#if DROPBEAR_CLI_PUBKEY_AUTH
	for (iter = cli_opts.privkeys->first; iter; iter = iter->next)
	{
		sign_key * key = (sign_key*)iter->item;
		len += 3 + strlen(key->filename);
	}
#endif /* DROPBEAR_CLI_PUBKEY_AUTH */

	len += 30; /* space for -W <size>, terminator. */
	ret = m_malloc(len);
	total = 0;

	if (cli_opts.no_hostkey_check)
	{
		int written = snprintf(ret+total, len-total, "-y -y ");
		total += written;
	}
	else if (cli_opts.always_accept_key)
	{
		int written = snprintf(ret+total, len-total, "-y ");
		total += written;
	}

	if (opts.recv_window != DEFAULT_RECV_WINDOW)
	{
		int written = snprintf(ret+total, len-total, "-W %u ", opts.recv_window);
		total += written;
	}

#if DROPBEAR_CLI_PUBKEY_AUTH
	for (iter = cli_opts.privkeys->first; iter; iter = iter->next)
	{
		sign_key * key = (sign_key*)iter->item;
		const size_t size = len - total;
		int written = snprintf(ret+total, size, "-i %s ", key->filename);
		dropbear_assert((unsigned int)written < size);
		total += written;
	}
#endif /* DROPBEAR_CLI_PUBKEY_AUTH */

	/* if args were passed, total will be not zero, and it will have a space at the end, so remove that */
	if (total > 0) 
	{
		total--;
	}

	return ret;
}

/* Sets up 'onion-forwarding' connections. This will spawn
 * a separate dbclient process for each hop.
 * As an example, if the cmdline is
 *   dbclient wrt,madako,canyons
 * then we want to run:
 *   dbclient -J "dbclient -B canyons:22 wrt,madako" canyons
 * and then the inner dbclient will recursively run:
 *   dbclient -J "dbclient -B madako:22 wrt" madako
 * etc for as many hosts as we want.
 *
 * Ports for hosts can be specified as host/port.
 */
static void parse_multihop_hostname(const char* orighostarg, const char* argv0) {
	char *userhostarg = NULL;
	char *hostbuf = NULL;
	char *last_hop = NULL;
	char *remainder = NULL;

	/* both scp and rsync parse a user@host argument
	 * and turn it into "-l user host". This breaks
	 * for our multihop syntax, so we suture it back together.
	 * This will break usernames that have both '@' and ',' in them,
	 * though that should be fairly uncommon. */
	if (cli_opts.username 
			&& strchr(cli_opts.username, ',') 
			&& strchr(cli_opts.username, '@')) {
		unsigned int len = strlen(orighostarg) + strlen(cli_opts.username) + 2;
		hostbuf = m_malloc(len);
		snprintf(hostbuf, len, "%s@%s", cli_opts.username, orighostarg);
	} else {
		hostbuf = m_strdup(orighostarg);
	}
	userhostarg = hostbuf;

	last_hop = strrchr(userhostarg, ',');
	if (last_hop) {
		if (last_hop == userhostarg) {
			dropbear_exit("Bad multi-hop hostnames");
		}
		*last_hop = '\0';
		last_hop++;
		remainder = userhostarg;
		userhostarg = last_hop;
	}

	parse_hostname(userhostarg);

	if (last_hop) {
		/* Set up the proxycmd */
		unsigned int cmd_len = 0;
		char *passthrough_args = multihop_passthrough_args();
		if (cli_opts.proxycmd) {
			dropbear_exit("-J can't be used with multihop mode");
		}
		if (cli_opts.remoteport == NULL) {
			cli_opts.remoteport = "22";
		}
		cmd_len = strlen(argv0) + strlen(remainder) 
			+ strlen(cli_opts.remotehost) + strlen(cli_opts.remoteport)
			+ strlen(passthrough_args)
			+ 30;
		cli_opts.proxycmd = m_malloc(cmd_len);
		snprintf(cli_opts.proxycmd, cmd_len, "%s -B %s:%s %s %s", 
				argv0, cli_opts.remotehost, cli_opts.remoteport, 
				passthrough_args, remainder);
#ifndef DISABLE_ZLIB
		/* The stream will be incompressible since it's encrypted. */
		opts.compress_mode = DROPBEAR_COMPRESS_OFF;
#endif
		m_free(passthrough_args);
	}
	m_free(hostbuf);
}
#endif /* !DROPBEAR_CLI_MULTIHOP */

/* Parses a [user@]hostname[/port] argument. */
static void parse_hostname(const char* orighostarg) {
	char *userhostarg = NULL;
	char *port = NULL;

	userhostarg = m_strdup(orighostarg);

	cli_opts.remotehost = strchr(userhostarg, '@');
	if (cli_opts.remotehost == NULL) {
		/* no username portion, the cli-auth.c code can figure the
		 * local user's name */
		cli_opts.remotehost = userhostarg;
	} else {
		cli_opts.remotehost[0] = '\0'; /* Split the user/host */
		cli_opts.remotehost++;
		cli_opts.username = userhostarg;
	}

	if (cli_opts.username == NULL) {
		cli_opts.username = m_strdup(cli_opts.own_user);
	}

	port = strchr(cli_opts.remotehost, '^');
	if (!port)  {
		/* legacy separator */
		port = strchr(cli_opts.remotehost, '/');
	}
	if (port) {
		*port = '\0';
		cli_opts.remoteport = port+1;
	}

	if (cli_opts.remotehost[0] == '\0') {
		dropbear_exit("Bad hostname");
	}
}

#if DROPBEAR_CLI_NETCAT
static void add_netcat(const char* origstr) {
	char *portstr = NULL;
	
	char * str = m_strdup(origstr);
	
	portstr = strchr(str, ':');
	if (portstr == NULL) {
		TRACE(("No netcat port"))
		goto fail;
	}
	*portstr = '\0';
	portstr++;
	
	if (strchr(portstr, ':')) {
		TRACE(("Multiple netcat colons"))
		goto fail;
	}
	
	if (m_str_to_uint(portstr, &cli_opts.netcat_port) == DROPBEAR_FAILURE) {
		TRACE(("bad netcat port"))
		goto fail;
	}
	
	if (cli_opts.netcat_port > 65535) {
		TRACE(("too large netcat port"))
		goto fail;
	}
	
	cli_opts.netcat_host = str;
	return;
	
fail:
	dropbear_exit("Bad netcat endpoint '%s'", origstr);
}
#endif

static void fill_own_user() {
	uid_t uid;
	struct passwd *pw = NULL; 

	uid = getuid();

	pw = getpwuid(uid);
	if (pw && pw->pw_name != NULL) {
		cli_opts.own_user = m_strdup(pw->pw_name);
	} else {
		dropbear_log(LOG_INFO, "Warning: failed to identify current user. Trying anyway.");
		cli_opts.own_user = m_strdup("unknown");
	}

}

#if DROPBEAR_CLI_ANYTCPFWD
/* Turn a "[listenaddr:]listenport:remoteaddr:remoteport" string into into a forwarding
 * set, and add it to the forwarding list */
static void addforward(const char* origstr, m_list *fwdlist) {

	char *part1 = NULL, *part2 = NULL, *part3 = NULL, *part4 = NULL;
	char * listenaddr = NULL;
	char * listenport = NULL;
	char * connectaddr = NULL;
	char * connectport = NULL;
	struct TCPFwdEntry* newfwd = NULL;
	char * str = NULL;

	TRACE(("enter addforward"))

	/* We need to split the original argument up. This var
	   is never free()d. */ 
	str = m_strdup(origstr);

	part1 = str;

	part2 = strchr(str, ':');
	if (part2 == NULL) {
		TRACE(("part2 == NULL"))
		goto fail;
	}
	*part2 = '\0';
	part2++;

	part3 = strchr(part2, ':');
	if (part3 == NULL) {
		TRACE(("part3 == NULL"))
		goto fail;
	}
	*part3 = '\0';
	part3++;

	part4 = strchr(part3, ':');
	if (part4) {
		*part4 = '\0';
		part4++;
	}

	if (part4) {
		listenaddr = part1;
		listenport = part2;
		connectaddr = part3;
		connectport = part4;
	} else {
		listenaddr = NULL;
		listenport = part1;
		connectaddr = part2;
		connectport = part3;
	}

	newfwd = m_malloc(sizeof(struct TCPFwdEntry));

	/* Now we check the ports - note that the port ints are unsigned,
	 * the check later only checks for >= MAX_PORT */
	if (m_str_to_uint(listenport, &newfwd->listenport) == DROPBEAR_FAILURE) {
		TRACE(("bad listenport strtoul"))
		goto fail;
	}

	if (m_str_to_uint(connectport, &newfwd->connectport) == DROPBEAR_FAILURE) {
		TRACE(("bad connectport strtoul"))
		goto fail;
	}

	newfwd->listenaddr = listenaddr;
	newfwd->connectaddr = connectaddr;

	if (newfwd->listenport > 65535) {
		TRACE(("listenport > 65535"))
		goto badport;
	}
		
	if (newfwd->connectport > 65535) {
		TRACE(("connectport > 65535"))
		goto badport;
	}

	newfwd->have_reply = 0;
	list_append(fwdlist, newfwd);

	TRACE(("leave addforward: done"))
	return;

fail:
	dropbear_exit("Bad TCP forward '%s'", origstr);

badport:
	dropbear_exit("Bad TCP port in '%s'", origstr);
}
#endif

static int match_extendedopt(const char** strptr, const char *optname) {
	int seen_eq = 0;
	int optlen = strlen(optname);
	const char *str = *strptr;

	while (isspace(*str)) {
		++str;
	}

	if (strncasecmp(str, optname, optlen) != 0) {
		return DROPBEAR_FAILURE;
	}

	str += optlen;

	while (isspace(*str) || (!seen_eq && *str == '=')) {
		if (*str == '=') {
			seen_eq = 1;
		}
		++str;
	}

	if (str-*strptr == optlen) {
		/* matched just a prefix of optname */
		return DROPBEAR_FAILURE;
	}

	*strptr = str;
	return DROPBEAR_SUCCESS;
}

static int parse_flag_value(const char *value) {
	if (strcmp(value, "yes") == 0 || strcmp(value, "true") == 0) {
		return 1;
	} else if (strcmp(value, "no") == 0 || strcmp(value, "false") == 0) {
		return 0;
	}

	dropbear_exit("Bad yes/no argument '%s'", value);
}

static void add_extendedopt(const char* origstr) {
	const char *optstr = origstr;

	if (strcmp(origstr, "help") == 0) {
		dropbear_log(LOG_INFO, "Available options:\n"
#if DROPBEAR_CLI_ANYTCPFWD
			"\tExitOnForwardFailure\n"
#endif
			"\tDisableTrivialAuth\n"
#ifndef DISABLE_SYSLOG
			"\tUseSyslog\n"
#endif
			"\tPort\n"
		);
		exit(EXIT_SUCCESS);
	}

#if DROPBEAR_CLI_ANYTCPFWD
	if (match_extendedopt(&optstr, "ExitOnForwardFailure") == DROPBEAR_SUCCESS) {
		cli_opts.exit_on_fwd_failure = parse_flag_value(optstr);
		return;
	}
#endif

#ifndef DISABLE_SYSLOG
	if (match_extendedopt(&optstr, "UseSyslog") == DROPBEAR_SUCCESS) {
		opts.usingsyslog = parse_flag_value(optstr);
		return;
	}
#endif

	if (match_extendedopt(&optstr, "Port") == DROPBEAR_SUCCESS) {
		cli_opts.remoteport = optstr;
		return;
	}

	if (match_extendedopt(&optstr, "DisableTrivialAuth") == DROPBEAR_SUCCESS) {
		cli_opts.disable_trivial_auth = parse_flag_value(optstr);
		return;
	}

	dropbear_log(LOG_WARNING, "Ignoring unknown configuration option '%s'", origstr);
}