view svr-runopts.c @ 1653:76189c9ffea2

External Public-Key Authentication API (#72) * Implemented dynamic loading of an external plug-in shared library to delegate public key authentication * Moved conditional compilation of the plugin infrastructure into the configure.ac script to be able to add -ldl to dropbear build only when the flag is enabled * Added tags file to the ignore list * Updated API to have the constructor to return function pointers in the pliugin instance. Added support for passing user name to the checkpubkey function. Added options to the session returned by the plugin and have dropbear to parse and process them * Added -rdynamic to the linker flags when EPKA is enabled * Changed the API to pass a previously created session to the checkPubKey function (created during preauth) * Added documentation to the API * Added parameter addrstring to plugin creation function * Modified the API to retrieve the auth options. Instead of having them as field of the EPKASession struct, they are stored internally (plugin-dependent) in the plugin/session and retrieved through a pointer to a function (in the session) * Changed option string to be a simple char * instead of unsigned char *
author fabriziobertocci <fabriziobertocci@gmail.com>
date Wed, 15 May 2019 09:43:57 -0400
parents 0dc3103a5900
children cc0fc5131c5c
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 "ecdsa.h"

#include <grp.h>

svr_runopts svr_opts; /* GLOBAL */

static void printhelp(const char * progname);
static void addportandaddress(const char* spec);
static void loadhostkey(const char *keyfile, int fatal_duplicate);
static void addhostkey(const char *keyfile);

static void printhelp(const char * progname) {

	fprintf(stderr, "Dropbear server v%s https://matt.ucc.asn.au/dropbear/dropbear.html\n"
					"Usage: %s [options]\n"
					"-b bannerfile	Display the contents of bannerfile"
					" before user login\n"
					"		(default: none)\n"
					"-r keyfile      Specify hostkeys (repeatable)\n"
					"		defaults: \n"
#if DROPBEAR_DSS
					"		- dss %s\n"
#endif
#if DROPBEAR_RSA
					"		- rsa %s\n"
#endif
#if DROPBEAR_ECDSA
					"		- ecdsa %s\n"
#endif
#if DROPBEAR_DELAY_HOSTKEY
					"-R		Create hostkeys as required\n" 
#endif
					"-F		Don't fork into background\n"
#ifdef DISABLE_SYSLOG
					"(Syslog support not compiled in, using stderr)\n"
#else
					"-E		Log to stderr rather than syslog\n"
#endif
#if DO_MOTD
					"-m		Don't display the motd on login\n"
#endif
					"-w		Disallow root logins\n"
#ifdef HAVE_GETGROUPLIST
					"-G		Restrict logins to members of specified group\n"
#endif
#if DROPBEAR_SVR_PASSWORD_AUTH || DROPBEAR_SVR_PAM_AUTH
					"-s		Disable password logins\n"
					"-g		Disable password logins for root\n"
					"-B		Allow blank password logins\n"
#endif
					"-T		Maximum authentication tries (default %d)\n"
#if DROPBEAR_SVR_LOCALTCPFWD
					"-j		Disable local port forwarding\n"
#endif
#if DROPBEAR_SVR_REMOTETCPFWD
					"-k		Disable remote port forwarding\n"
					"-a		Allow connections to forwarded ports from any host\n"
					"-c command	Force executed command\n"
#endif
					"-p [address:]port\n"
					"		Listen on specified tcp port (and optionally address),\n"
					"		up to %d can be specified\n"
					"		(default port is %s if none specified)\n"
					"-P PidFile	Create pid file PidFile\n"
					"		(default %s)\n"
#if INETD_MODE
					"-i		Start for inetd\n"
#endif
					"-W <receive_window_buffer> (default %d, larger may be faster, max 1MB)\n"
					"-K <keepalive>  (0 is never, default %d, in seconds)\n"
					"-I <idle_timeout>  (0 is never, default %d, in seconds)\n"
#if DROPBEAR_EPKA
                                        "-A <authplugin>[,<options>]\n"
                                        "               Enable external public key auth through <authplugin>\n"
#endif
					"-V    Version\n"
#if DEBUG_TRACE
					"-v		verbose (compiled with DEBUG_TRACE)\n"
#endif
					,DROPBEAR_VERSION, progname,
#if DROPBEAR_DSS
					DSS_PRIV_FILENAME,
#endif
#if DROPBEAR_RSA
					RSA_PRIV_FILENAME,
#endif
#if DROPBEAR_ECDSA
					ECDSA_PRIV_FILENAME,
#endif
					MAX_AUTH_TRIES,
					DROPBEAR_MAX_PORTS, DROPBEAR_DEFPORT, DROPBEAR_PIDFILE,
					DEFAULT_RECV_WINDOW, DEFAULT_KEEPALIVE, DEFAULT_IDLE_TIMEOUT);
}

void svr_getopts(int argc, char ** argv) {

	unsigned int i, j;
	char ** next = NULL;
	int nextisport = 0;
	char* recv_window_arg = NULL;
	char* keepalive_arg = NULL;
	char* idle_timeout_arg = NULL;
	char* maxauthtries_arg = NULL;
	char* keyfile = NULL;
	char c;
#if DROPBEAR_EPKA
        char* pubkey_plugin = NULL;
#endif


	/* see printhelp() for options */
	svr_opts.bannerfile = NULL;
	svr_opts.banner = NULL;
	svr_opts.forced_command = NULL;
	svr_opts.forkbg = 1;
	svr_opts.norootlogin = 0;
#ifdef HAVE_GETGROUPLIST
	svr_opts.restrict_group = NULL;
	svr_opts.restrict_group_gid = 0;
#endif
	svr_opts.noauthpass = 0;
	svr_opts.norootpass = 0;
	svr_opts.allowblankpass = 0;
	svr_opts.maxauthtries = MAX_AUTH_TRIES;
	svr_opts.inetdmode = 0;
	svr_opts.portcount = 0;
	svr_opts.hostkey = NULL;
	svr_opts.delay_hostkey = 0;
	svr_opts.pidfile = DROPBEAR_PIDFILE;
#if DROPBEAR_SVR_LOCALTCPFWD
	svr_opts.nolocaltcp = 0;
#endif
#if DROPBEAR_SVR_REMOTETCPFWD
	svr_opts.noremotetcp = 0;
#endif
#if DROPBEAR_EPKA
        svr_opts.pubkey_plugin = NULL;
        svr_opts.pubkey_plugin_options = NULL;
#endif

#ifndef DISABLE_ZLIB
	opts.compress_mode = DROPBEAR_COMPRESS_DELAYED;
#endif 

	/* not yet
	opts.ipv4 = 1;
	opts.ipv6 = 1;
	*/
#if DO_MOTD
	svr_opts.domotd = 1;
#endif
#ifndef DISABLE_SYSLOG
	opts.usingsyslog = 1;
#endif
	opts.recv_window = DEFAULT_RECV_WINDOW;
	opts.keepalive_secs = DEFAULT_KEEPALIVE;
	opts.idle_timeout_secs = DEFAULT_IDLE_TIMEOUT;
	
#if DROPBEAR_SVR_REMOTETCPFWD
	opts.listen_fwd_all = 0;
#endif

	for (i = 1; i < (unsigned int)argc; i++) {
		if (argv[i][0] != '-' || argv[i][1] == '\0')
			dropbear_exit("Invalid argument: %s", argv[i]);

		for (j = 1; (c = argv[i][j]) != '\0' && !next && !nextisport; j++) {
			switch (c) {
				case 'b':
					next = &svr_opts.bannerfile;
					break;
				case 'c':
					next = &svr_opts.forced_command;
					break;
				case 'd':
				case 'r':
					next = &keyfile;
					break;
				case 'R':
					svr_opts.delay_hostkey = 1;
					break;
				case 'F':
					svr_opts.forkbg = 0;
					break;
#ifndef DISABLE_SYSLOG
				case 'E':
					opts.usingsyslog = 0;
					break;
#endif
#if DROPBEAR_SVR_LOCALTCPFWD
				case 'j':
					svr_opts.nolocaltcp = 1;
					break;
#endif
#if DROPBEAR_SVR_REMOTETCPFWD
				case 'k':
					svr_opts.noremotetcp = 1;
					break;
				case 'a':
					opts.listen_fwd_all = 1;
					break;
#endif
#if INETD_MODE
				case 'i':
					svr_opts.inetdmode = 1;
					break;
#endif
				case 'p':
				  nextisport = 1;
				  break;
				case 'P':
					next = &svr_opts.pidfile;
					break;
#if DO_MOTD
				/* motd is displayed by default, -m turns it off */
				case 'm':
					svr_opts.domotd = 0;
					break;
#endif
				case 'w':
					svr_opts.norootlogin = 1;
					break;
#ifdef HAVE_GETGROUPLIST
				case 'G':
					next = &svr_opts.restrict_group;
					break;
#endif
				case 'W':
					next = &recv_window_arg;
					break;
				case 'K':
					next = &keepalive_arg;
					break;
				case 'I':
					next = &idle_timeout_arg;
					break;
				case 'T':
					next = &maxauthtries_arg;
					break;
#if DROPBEAR_SVR_PASSWORD_AUTH || DROPBEAR_SVR_PAM_AUTH
				case 's':
					svr_opts.noauthpass = 1;
					break;
				case 'g':
					svr_opts.norootpass = 1;
					break;
				case 'B':
					svr_opts.allowblankpass = 1;
					break;
#endif
				case 'h':
					printhelp(argv[0]);
					exit(EXIT_SUCCESS);
					break;
				case 'u':
					/* backwards compatibility with old urandom option */
					break;
#if DROPBEAR_EPKA
                                case 'A':
                                        next = &pubkey_plugin;
                                        break;
#endif
#if DEBUG_TRACE
				case 'v':
					debug_trace = 1;
					break;
#endif
				case 'V':
					print_version();
					exit(EXIT_SUCCESS);
					break;
				default:
					fprintf(stderr, "Invalid option -%c\n", c);
					printhelp(argv[0]);
					exit(EXIT_FAILURE);
					break;
			}
		}

		if (!next && !nextisport)
			continue;

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

		if (nextisport) {
			addportandaddress(&argv[i][j]);
			nextisport = 0;
		} else if (next) {
			*next = &argv[i][j];
			if (*next == NULL) {
				dropbear_exit("Invalid null argument");
			}
			next = NULL;

			if (keyfile) {
				addhostkey(keyfile);
				keyfile = NULL;
			}
		}
	}

	/* Set up listening ports */
	if (svr_opts.portcount == 0) {
		svr_opts.ports[0] = m_strdup(DROPBEAR_DEFPORT);
		svr_opts.addresses[0] = m_strdup(DROPBEAR_DEFADDRESS);
		svr_opts.portcount = 1;
	}

	if (svr_opts.bannerfile) {
		struct stat buf;
		if (stat(svr_opts.bannerfile, &buf) != 0) {
			dropbear_exit("Error opening banner file '%s'",
					svr_opts.bannerfile);
		}
		
		if (buf.st_size > MAX_BANNER_SIZE) {
			dropbear_exit("Banner file too large, max is %d bytes",
					MAX_BANNER_SIZE);
		}

		svr_opts.banner = buf_new(buf.st_size);
		if (buf_readfile(svr_opts.banner, svr_opts.bannerfile)!=DROPBEAR_SUCCESS) {
			dropbear_exit("Error reading banner file '%s'",
					svr_opts.bannerfile);
		}
		buf_setpos(svr_opts.banner, 0);
	}

#ifdef HAVE_GETGROUPLIST
	if (svr_opts.restrict_group) {
		struct group *restrictedgroup = getgrnam(svr_opts.restrict_group);

		if (restrictedgroup){
			svr_opts.restrict_group_gid = restrictedgroup->gr_gid;
		} else {
			dropbear_exit("Cannot restrict logins to group '%s' as the group does not exist", svr_opts.restrict_group);
		}
	}
#endif
	
	if (recv_window_arg) {
		opts.recv_window = atol(recv_window_arg);
		if (opts.recv_window == 0 || opts.recv_window > MAX_RECV_WINDOW) {
			dropbear_exit("Bad recv window '%s'", recv_window_arg);
		}
	}

	if (maxauthtries_arg) {
		unsigned int val = 0;
		if (m_str_to_uint(maxauthtries_arg, &val) == DROPBEAR_FAILURE 
			|| val == 0) {
			dropbear_exit("Bad maxauthtries '%s'", maxauthtries_arg);
		}
		svr_opts.maxauthtries = val;
	}

	
	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 (svr_opts.forced_command) {
		dropbear_log(LOG_INFO, "Forced command set to '%s'", svr_opts.forced_command);
	}
#if DROPBEAR_EPKA
        if (pubkey_plugin) {
            char *args = strchr(pubkey_plugin, ',');
            if (args) {
                *args='\0';
                ++args;
            }
            svr_opts.pubkey_plugin = pubkey_plugin;
            svr_opts.pubkey_plugin_options = args;
        }
#endif
}

static void addportandaddress(const char* spec) {
	char *spec_copy = NULL, *myspec = NULL, *port = NULL, *address = NULL;

	if (svr_opts.portcount < DROPBEAR_MAX_PORTS) {

		/* We don't free it, it becomes part of the runopt state */
		spec_copy = m_strdup(spec);
		myspec = spec_copy;

		if (myspec[0] == '[') {
			myspec++;
			port = strchr(myspec, ']');
			if (!port) {
				/* Unmatched [ -> exit */
				dropbear_exit("Bad listen address");
			}
			port[0] = '\0';
			port++;
			if (port[0] != ':') {
				/* Missing port -> exit */
				dropbear_exit("Missing port");
			}
		} else {
			/* search for ':', that separates address and port */
			port = strrchr(myspec, ':');
		}

		if (!port) {
			/* no ':' -> the whole string specifies just a port */
			port = myspec;
		} else {
			/* Split the address/port */
			port[0] = '\0'; 
			port++;
			address = myspec;
		}

		if (!address) {
			/* no address given -> fill in the default address */
			address = DROPBEAR_DEFADDRESS;
		}

		if (port[0] == '\0') {
			/* empty port -> exit */
			dropbear_exit("Bad port");
		}
		svr_opts.ports[svr_opts.portcount] = m_strdup(port);
		svr_opts.addresses[svr_opts.portcount] = m_strdup(address);
		svr_opts.portcount++;
		m_free(spec_copy);
	}
}

static void disablekey(int type) {
	int i;
	TRACE(("Disabling key type %d", type))
	for (i = 0; sshhostkey[i].name != NULL; i++) {
		if (sshhostkey[i].val == type) {
			sshhostkey[i].usable = 0;
			break;
		}
	}
}

static void loadhostkey_helper(const char *name, void** src, void** dst, int fatal_duplicate) {
	if (*dst) {
		if (fatal_duplicate) {
			dropbear_exit("Only one %s key can be specified", name);
		}
	} else {
		*dst = *src;
		*src = NULL;
	}

}

/* Must be called after syslog/etc is working */
static void loadhostkey(const char *keyfile, int fatal_duplicate) {
	sign_key * read_key = new_sign_key();
	enum signkey_type type = DROPBEAR_SIGNKEY_ANY;
	if (readhostkey(keyfile, read_key, &type) == DROPBEAR_FAILURE) {
		if (!svr_opts.delay_hostkey) {
			dropbear_log(LOG_WARNING, "Failed loading %s", keyfile);
		}
	}

#if DROPBEAR_RSA
	if (type == DROPBEAR_SIGNKEY_RSA) {
		loadhostkey_helper("RSA", (void**)&read_key->rsakey, (void**)&svr_opts.hostkey->rsakey, fatal_duplicate);
	}
#endif

#if DROPBEAR_DSS
	if (type == DROPBEAR_SIGNKEY_DSS) {
		loadhostkey_helper("DSS", (void**)&read_key->dsskey, (void**)&svr_opts.hostkey->dsskey, fatal_duplicate);
	}
#endif

#if DROPBEAR_ECDSA
#if DROPBEAR_ECC_256
	if (type == DROPBEAR_SIGNKEY_ECDSA_NISTP256) {
		loadhostkey_helper("ECDSA256", (void**)&read_key->ecckey256, (void**)&svr_opts.hostkey->ecckey256, fatal_duplicate);
	}
#endif
#if DROPBEAR_ECC_384
	if (type == DROPBEAR_SIGNKEY_ECDSA_NISTP384) {
		loadhostkey_helper("ECDSA384", (void**)&read_key->ecckey384, (void**)&svr_opts.hostkey->ecckey384, fatal_duplicate);
	}
#endif
#if DROPBEAR_ECC_521
	if (type == DROPBEAR_SIGNKEY_ECDSA_NISTP521) {
		loadhostkey_helper("ECDSA521", (void**)&read_key->ecckey521, (void**)&svr_opts.hostkey->ecckey521, fatal_duplicate);
	}
#endif
#endif /* DROPBEAR_ECDSA */
	sign_key_free(read_key);
	TRACE(("leave loadhostkey"))
}

static void addhostkey(const char *keyfile) {
	if (svr_opts.num_hostkey_files >= MAX_HOSTKEYS) {
		dropbear_exit("Too many hostkeys");
	}
	svr_opts.hostkey_files[svr_opts.num_hostkey_files] = m_strdup(keyfile);
	svr_opts.num_hostkey_files++;
}


void load_all_hostkeys() {
	int i;
	int any_keys = 0;
#ifdef DROPBEAR_ECDSA
	int loaded_any_ecdsa = 0;
#endif

	svr_opts.hostkey = new_sign_key();

	for (i = 0; i < svr_opts.num_hostkey_files; i++) {
		char *hostkey_file = svr_opts.hostkey_files[i];
		loadhostkey(hostkey_file, 1);
		m_free(hostkey_file);
	}

	/* Only load default host keys if a host key is not specified by the user */
	if (svr_opts.num_hostkey_files == 0) {
#if DROPBEAR_RSA
		loadhostkey(RSA_PRIV_FILENAME, 0);
#endif

#if DROPBEAR_DSS
		loadhostkey(DSS_PRIV_FILENAME, 0);
#endif

#if DROPBEAR_ECDSA
		loadhostkey(ECDSA_PRIV_FILENAME, 0);
#endif
	}

#if DROPBEAR_RSA
	if (!svr_opts.delay_hostkey && !svr_opts.hostkey->rsakey) {
		disablekey(DROPBEAR_SIGNKEY_RSA);
	} else {
		any_keys = 1;
	}
#endif

#if DROPBEAR_DSS
	if (!svr_opts.delay_hostkey && !svr_opts.hostkey->dsskey) {
		disablekey(DROPBEAR_SIGNKEY_DSS);
	} else {
		any_keys = 1;
	}
#endif

#if DROPBEAR_ECDSA
	/* We want to advertise a single ecdsa algorithm size.
	- If there is a ecdsa hostkey at startup we choose that that size.
	- If we generate at runtime we choose the default ecdsa size.
	- Otherwise no ecdsa keys will be advertised */

	/* check if any keys were loaded at startup */
	loaded_any_ecdsa = 
		0
#if DROPBEAR_ECC_256
		|| svr_opts.hostkey->ecckey256
#endif
#if DROPBEAR_ECC_384
		|| svr_opts.hostkey->ecckey384
#endif
#if DROPBEAR_ECC_521
		|| svr_opts.hostkey->ecckey521
#endif
		;
	any_keys |= loaded_any_ecdsa;

	/* Or an ecdsa key could be generated at runtime */
	any_keys |= svr_opts.delay_hostkey;

	/* At most one ecdsa key size will be left enabled */
#if DROPBEAR_ECC_256
	if (!svr_opts.hostkey->ecckey256
		&& (!svr_opts.delay_hostkey || loaded_any_ecdsa || ECDSA_DEFAULT_SIZE != 256 )) {
		disablekey(DROPBEAR_SIGNKEY_ECDSA_NISTP256);
	}
#endif
#if DROPBEAR_ECC_384
	if (!svr_opts.hostkey->ecckey384
		&& (!svr_opts.delay_hostkey || loaded_any_ecdsa || ECDSA_DEFAULT_SIZE != 384 )) {
		disablekey(DROPBEAR_SIGNKEY_ECDSA_NISTP384);
	}
#endif
#if DROPBEAR_ECC_521
	if (!svr_opts.hostkey->ecckey521
		&& (!svr_opts.delay_hostkey || loaded_any_ecdsa || ECDSA_DEFAULT_SIZE != 521 )) {
		disablekey(DROPBEAR_SIGNKEY_ECDSA_NISTP521);
	}
#endif
#endif /* DROPBEAR_ECDSA */

	if (!any_keys) {
		dropbear_exit("No hostkeys available. 'dropbear -R' may be useful or run dropbearkey.");
	}
}