view common-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 8b4274d34fe8
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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);
}

void parse_recv_window(const char* recv_window_arg) {
	int ret;
	unsigned int rw;

	ret = m_str_to_uint(recv_window_arg, &rw);
	if (ret == DROPBEAR_FAILURE || rw == 0 || rw > MAX_RECV_WINDOW) {
		if (rw > MAX_RECV_WINDOW) {
			opts.recv_window = MAX_RECV_WINDOW;
		}
		dropbear_log(LOG_WARNING, "Bad recv window '%s', using %d",
			recv_window_arg, opts.recv_window);
	} else {
		opts.recv_window = rw;
	}

}