view common-runopts.c @ 1790:42745af83b7d

Introduce extra delay before closing unauthenticated sessions To make it harder for attackers, introduce a delay to keep an unauthenticated session open a bit longer, thus blocking a connection slot until after the delay. Without this, while there is a limit on the amount of attempts an attacker can make at the same time (MAX_UNAUTH_PER_IP), the time taken by dropbear to handle one attempt is still short and thus for each of the allowed parallel attempts many attempts can be chained one after the other. The attempt rate is then: "MAX_UNAUTH_PER_IP / <process time of one attempt>". With the delay, this rate becomes: "MAX_UNAUTH_PER_IP / UNAUTH_CLOSE_DELAY".
author Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
date Wed, 15 Feb 2017 13:53:04 +0100
parents f8d8af12ac14
children 94dc11094e26
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/*
 * 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 "auth.h"
#include "algo.h"
#include "dbrandom.h"

runopts opts; /* GLOBAL */

/* returns success or failure, and the keytype in *type. If we want
 * to restrict the type, type can contain a type to return */
int readhostkey(const char * filename, sign_key * hostkey, 
	enum signkey_type *type) {

	int ret = DROPBEAR_FAILURE;
	buffer *buf;

	buf = buf_new(MAX_PRIVKEY_SIZE);

	if (buf_readfile(buf, filename) == DROPBEAR_FAILURE) {
		goto out;
	}
	buf_setpos(buf, 0);

	addrandom(buf_getptr(buf, buf->len), buf->len);

	if (buf_get_priv_key(buf, hostkey, type) == DROPBEAR_FAILURE) {
		goto out;
	}

	ret = DROPBEAR_SUCCESS;
out:

	buf_burn(buf);
	buf_free(buf);
	return ret;
}

#if DROPBEAR_USER_ALGO_LIST
void
parse_ciphers_macs() {
	int printed_help = 0;
	if (opts.cipher_list) {
		if (strcmp(opts.cipher_list, "help") == 0) {
			char *ciphers = algolist_string(sshciphers);
			dropbear_log(LOG_INFO, "Available ciphers: %s", ciphers);
			m_free(ciphers);
			printed_help = 1;
		} else {
			if (check_user_algos(opts.cipher_list, sshciphers, "cipher") == 0) {
				dropbear_exit("No valid ciphers specified for '-c'");
			}
		}
	}

	if (opts.mac_list) {
		if (strcmp(opts.mac_list, "help") == 0) {
			char *macs = algolist_string(sshhashes);
			dropbear_log(LOG_INFO, "Available MACs: %s", macs);
			m_free(macs);
			printed_help = 1;
		} else {
			if (check_user_algos(opts.mac_list, sshhashes, "MAC") == 0) {
				dropbear_exit("No valid MACs specified for '-m'");
			}
		}
	}
	if (printed_help) {
		dropbear_exit(".");
	}
}
#endif

void print_version() {
	fprintf(stderr, "Dropbear v%s\n", DROPBEAR_VERSION);
}