view options.h @ 605:53c21d4ec98a

- Don't allow setting memLevel since that doesn't work properly - Better handling of the case where compressing makes the data larger (possibly only happens when memLevel is adjusted, but better to be safe)
author Matt Johnston <>
date Mon, 28 Feb 2011 13:51:27 +0000
parents e001bd424f12
children e4991659fc10
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/* Dropbear SSH
 * Copyright (c) 2002,2003 Matt Johnston
 * All rights reserved. See LICENSE for the license. */

#ifndef _OPTIONS_H_
#define _OPTIONS_H_

 * Define compile-time options below - the "#ifndef DROPBEAR_XXX .... #endif"
 * parts are to allow for commandline -DDROPBEAR_XXX options etc.


/* Listen on all interfaces */

/* Default hostkey paths - these can be specified on the command line */
#define DSS_PRIV_FILENAME "/etc/dropbear/dropbear_dss_host_key"
#define RSA_PRIV_FILENAME "/etc/dropbear/dropbear_rsa_host_key"

/* Set NON_INETD_MODE if you require daemon functionality (ie Dropbear listens
 * on chosen ports and keeps accepting connections. This is the default.
 * Set INETD_MODE if you want to be able to run Dropbear with inetd (or
 * similar), where it will use stdin/stdout for connections, and each process
 * lasts for a single connection. Dropbear should be invoked with the -i flag
 * for inetd, and can only accept IPv4 connections.
 * Both of these flags can be defined at once, don't compile without at least
 * one of them. */
#define INETD_MODE

/* Setting this disables the fast exptmod bignum code. It saves ~5kB, but is
 * perhaps 20% slower for pubkey operations (it is probably worth experimenting
 * if you want to use this) */
/*#define NO_FAST_EXPTMOD*/

/* Set this if you want to use the DROPBEAR_SMALL_CODE option. This can save
several kB in binary size however will make the symmetrical ciphers and hashes
slower, perhaps by 50%. Recommended for small systems that aren't doing
much traffic. */

/* Enable X11 Forwarding - server only */
#define ENABLE_X11FWD

/* Enable TCP Fowarding */
/* 'Local' is "-L" style (client listening port forwarded via server)
 * 'Remote' is "-R" style (server listening port forwarded via client) */



/* Enable Authentication Agent Forwarding - server only for now */

/* Note: Both ENABLE_CLI_PROXYCMD and ENABLE_CLI_NETCAT must be set to
 * allow multihop dbclient connections */

/* Allow using -J <proxycommand> to run the connection through a 
   pipe to a program, rather the normal TCP connection */

/* Enable "Netcat mode" option. This will forward standard input/output
 * to a remote TCP-forwarded connection */

/* Encryption - at least one required.
 * Protocol RFC requires 3DES and recommends AES128 for interoperability.
 * Including multiple keysize variants the same cipher 
 * (eg AES256 as well as AES128) will result in a minimal size increase.*/
#define DROPBEAR_AES128
#define DROPBEAR_AES256
/* Compiling in Blowfish will add ~6kB to runtime heap memory usage */

/* Enable "Counter Mode" for ciphers. This is more secure than normal
 * CBC mode against certain attacks. This adds around 1kB to binary 
 * size and is recommended for most cases */

/* Message Integrity - at least one required.
 * Protocol RFC requires sha1 and recommends sha1-96.
 * sha1-96 may be of use for slow links, as it has a smaller overhead.
 * Note: there's no point disabling sha1 to save space, since it's used
 * for the random number generator and public-key cryptography anyway.
 * Disabling it here will just stop it from being used as the integrity portion
 * of the ssh protocol.
 * These hashes are also used for public key fingerprints in logs.
 * If you disable MD5, Dropbear will fall back to SHA1 fingerprints,
 * which are not the standard form. */

/* Hostkey/public key algorithms - at least one required, these are used
 * for hostkey as well as for verifying signatures with pubkey auth.
 * Removing either of these won't save very much space.
 * SSH2 RFC Draft requires dss, recommends rsa */

/* RSA can be vulnerable to timing attacks which use the time required for
 * signing to guess the private key. Blinding avoids this attack, though makes
 * signing operations slightly slower. */

/* Define DSS_PROTOK to use PuTTY's method of generating the value k for dss,
 * rather than just from the random byte source. Undefining this will save you
 * ~4k in binary size with static uclibc, but your DSS hostkey could be exposed
 * if the random number source isn't good. It happened to Sony. 
 * On systems with a decent random source this isn't required. */
/* #define DSS_PROTOK */

/* Control the memory/performance/compression tradeoff for zlib.
 * Set windowBits=8 for least memory usage, see your system's
 * zlib.h for full details.
 * Default settings (windowBits=15) will use 256kB for compression
 * windowBits=8 will use 129kB for compression.
 * Both modes will use ~35kB for decompression (using windowBits=15 for
 * interoperability) */

/* Whether to do reverse DNS lookups. */

/* Whether to print the message of the day (MOTD). This doesn't add much code
 * size */
#define DO_MOTD

/* The MOTD file path */
#define MOTD_FILENAME "/etc/motd"

/* Authentication Types - at least one required.
   RFC Draft requires pubkey auth, and recommends password */

/* Note: PAM auth is quite simple, and only works for PAM modules which just do
 * a simple "Login: " "Password: " (you can edit the strings in svr-authpam.c).
 * It's useful for systems like OS X where standard password crypts don't work,
 * but there's an interface via a PAM module - don't bother using it otherwise.
 * You can't enable both PASSWORD and PAM. */

/* PAM requires ./configure --enable-pam */

/* Whether to take public key options in 
 * authorized_keys file into account */


/* This variable can be used to set a password for client
 * authentication on the commandline. Beware of platforms
 * that don't protect environment variables of processes etc. Also
 * note that it will be provided for all "hidden" client-interactive
 * style prompts - if you want something more sophisticated, use 
 * SSH_ASKPASS instead. Comment out this var to remove this functionality.*/

/* Define this (as well as ENABLE_CLI_PASSWORD_AUTH) to allow the use of
 * a helper program for the ssh client. The helper program should be
 * specified in the SSH_ASKPASS environment variable, and dbclient
 * should be run with DISPLAY set and no tty. The program should
 * return the password on standard output */

/* Random device to use - define either DROPBEAR_RANDOM_DEV or
 * DROPBEAR_RANDOM_DEV is recommended on hosts with a good /dev/(u)random,
 * otherwise use run prngd (or egd if you want), specifying the socket. 
 * The device will be queried for a few dozen bytes of seed a couple of times
 * per session (or more for very long-lived sessions). */

/* We'll use /dev/urandom by default, since /dev/random is too much hassle.
 * If system developers aren't keeping seeds between boots nor getting
 * any entropy from somewhere it's their own fault. */
#define DROPBEAR_RANDOM_DEV "/dev/urandom"

/* prngd must be manually set up to produce output */
/*#define DROPBEAR_PRNGD_SOCKET "/var/run/dropbear-rng"*/

/* Specify the number of clients we will allow to be connected but
 * not yet authenticated. After this limit, connections are rejected */
/* The first setting is per-IP, to avoid denial of service */

/* And then a global limit to avoid chewing memory if connections 
 * come from many IPs */

/* Maximum number of failed authentication tries (server option) */
#define MAX_AUTH_TRIES 10

/* The default file to store the daemon's process ID, for shutdown
   scripts etc. This can be overridden with the -P flag */
#define DROPBEAR_PIDFILE "/var/run/"

/* The command to invoke for xauth when using X11 forwarding.
 * "-q" for quiet */
#define XAUTH_COMMAND "/usr/bin/X11/xauth -q"

/* if you want to enable running an sftp server (such as the one included with
 * OpenSSH), set the path below. If the path isn't defined, sftp will not
 * be enabled */
#define SFTPSERVER_PATH "/usr/libexec/sftp-server"

/* This is used by the scp binary when used as a client binary. If you're
 * not using the Dropbear client, you'll need to change it */
#define _PATH_SSH_PROGRAM "/usr/bin/dbclient"

/* Whether to log commands executed by a client. This only logs the 
 * (single) command sent to the server, not what a user did in a 
 * shell/sftp session etc. */
/* #define LOG_COMMANDS */

/* Window size limits. These tend to be a trade-off between memory
   usage and network performance: */
/* Size of the network receive window. This amount of memory is allocated
   as a per-channel receive buffer. Increasing this value can make a
   significant difference to network performance. 24kB was empirically
   chosen for a 100mbit ethernet network. The value can be altered at
   runtime with the -W argument. */
/* Maximum size of a received SSH data packet - this _MUST_ be >= 32768
   in order to interoperate with other implementations */
#define RECV_MAX_PAYLOAD_LEN 32768
/* Maximum size of a transmitted data packet - this can be any value,
   though increasing it may not make a significant difference. */

/* Ensure that data is transmitted every KEEPALIVE seconds. This can
be overridden at runtime with -K. 0 disables keepalives */

/* Ensure that data is received within IDLE_TIMEOUT seconds. This can
be overridden at runtime with -I. 0 disables idle timeouts */

/* The default path. This will often get replaced by the shell */
#define DEFAULT_PATH "/usr/bin:/bin"

/* Some other defines (that mostly should be left alone) are defined
 * in sysoptions.h */
#include "sysoptions.h"

#endif /* _OPTIONS_H_ */