options.h

/* Dropbear SSH
 * Copyright (c) 2002,2003 Matt Johnston
 * All rights reserved. See LICENSE for the license. */

#ifndef DROPBEAR_OPTIONS_H_
#define DROPBEAR_OPTIONS_H_

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

/* IMPORTANT: Many options will require "make clean" after changes */

#ifndef DROPBEAR_DEFPORT
#define DROPBEAR_DEFPORT "22"
#endif

#ifndef DROPBEAR_DEFADDRESS
/* Listen on all interfaces */
#define DROPBEAR_DEFADDRESS "127.0.0.1"
#endif

/* 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. */
#define DROPBEAR_SMALL_CODE

/* 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) */

#define ENABLE_CLI_LOCALTCPFWD
#define ENABLE_CLI_REMOTETCPFWD

#define ENABLE_SVR_LOCALTCPFWD
#define ENABLE_SVR_REMOTETCPFWD

/* Enable Authentication Agent Forwarding */
#define ENABLE_SVR_AGENTFWD
#define ENABLE_CLI_AGENTFWD

/* 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 */
#define ENABLE_CLI_PROXYCMD

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

/* Whether to support "-c" and "-m" flags to choose ciphers/MACs at runtime */
#define ENABLE_USER_ALGO_LIST

/* 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_3DES
#define DROPBEAR_AES256
/* Compiling in Blowfish will add ~6kB to runtime heap memory usage */
/*#define DROPBEAR_BLOWFISH*/
#define DROPBEAR_TWOFISH256
#define DROPBEAR_TWOFISH128

/* Enable CBC mode for ciphers. This has security issues though
 * is the most compatible with older SSH implementations */
#define DROPBEAR_ENABLE_CBC_MODE

/* Enable "Counter Mode" for ciphers. This is more secure than normal
 * CBC mode against certain attacks. It is recommended for security
 * and forwards compatibility */
#define DROPBEAR_ENABLE_CTR_MODE

/* Twofish counter mode is disabled by default because it
has not been tested for interoperability with other SSH implementations.
If you test it please contact the Dropbear author */
/* #define DROPBEAR_TWOFISH_CTR */

/* You can compile with no encryption if you want. In some circumstances
 * this could be safe security-wise, though make sure you know what
 * you're doing. Anyone can see everything that goes over the wire, so
 * the only safe auth method is public key. */
/* #define DROPBEAR_NONE_CIPHER */

/* Message Integrity - at least one required.
 * Protocol RFC requires sha1 and recommends sha1-96.
 * sha1-96 is of use for slow links as it has a smaller overhead.
 *
 * There's no reason to disable sha1 or sha1-96 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. */
#define DROPBEAR_SHA1_HMAC
#define DROPBEAR_SHA1_96_HMAC
#define DROPBEAR_SHA2_256_HMAC
#define DROPBEAR_SHA2_512_HMAC
#define DROPBEAR_MD5_HMAC

/* You can also disable integrity. Don't bother disabling this if you're
 * still using a cipher, it's relatively cheap. If you disable this it's dead
 * simple for an attacker to run arbitrary commands on the remote host. Beware.
 */
/* #define DROPBEAR_NONE_INTEGRITY */

/* 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 */
#define DROPBEAR_RSA
#define DROPBEAR_DSS
/* ECDSA is significantly faster than RSA or DSS. Compiling in ECC
 * code (either ECDSA or ECDH) increases binary size - around 30kB
 * on x86-64 */
#define DROPBEAR_ECDSA

/* Enable Curve25519 for key exchange. This is another elliptic
 * curve method with good security properties. Increases binary size
 * by ~8kB on x86-64 */
#define DROPBEAR_CURVE25519

/* Enable elliptic curve Diffie Hellman key exchange, see note about
 * ECDSA above */
#define DROPBEAR_ECDH

/* Group14 (2048 bit) is recommended. Group1 is less secure (1024 bit) though
   is the only option for interoperability with some older SSH programs */
#define DROPBEAR_DH_GROUP1 1
#define DROPBEAR_DH_GROUP14 1

/* 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) */
#ifndef DROPBEAR_ZLIB_WINDOW_BITS
#define DROPBEAR_ZLIB_WINDOW_BITS 15
#endif

/* Server won't allow zlib compression until after authentication. Prevents
   flaws in the zlib library being unauthenticated exploitable flaws.
   Some old ssh clients may not support the alternative zlib@openssh.com method
   */
#define DROPBEAR_SERVER_DELAY_ZLIB 1

/* Whether to do reverse DNS lookups. */
/*#define DO_HOST_LOOKUP */

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

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

/* 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. It won't work for more complex
 * PAM challenge/response.
 * You can't enable both PASSWORD and PAM. */

/* This requires crypt() */
#ifdef HAVE_CRYPT
#define ENABLE_SVR_PASSWORD_AUTH
#endif
/* PAM requires ./configure --enable-pam */
/*#define ENABLE_SVR_PAM_AUTH */
#define ENABLE_SVR_PUBKEY_AUTH

/* Whether to take public key options in
 * authorized_keys file into account */
#ifdef ENABLE_SVR_PUBKEY_AUTH
#define ENABLE_SVR_PUBKEY_OPTIONS
#endif

/* This requires getpass. */
#ifdef HAVE_GETPASS
#define ENABLE_CLI_PASSWORD_AUTH
#define ENABLE_CLI_INTERACT_AUTH
#endif
#define ENABLE_CLI_PUBKEY_AUTH

/* A default argument for dbclient -i <privatekey>.
Homedir is prepended unless path begins with / */
#define DROPBEAR_DEFAULT_CLI_AUTHKEY ".ssh/id_dropbear"

/* 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 DROPBEAR_PASSWORD_ENV "DROPBEAR_PASSWORD"

/* 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 */
/*#define ENABLE_CLI_ASKPASS_HELPER*/

/* Save a network roundtrip by sendng a real auth request immediately after
 * sending a query for the available methods.  It is at the expense of < 100
 * bytes of extra network traffic. This is not yet enabled by default since it
 * could cause problems with non-compliant servers */
/* #define DROPBEAR_CLI_IMMEDIATE_AUTH */

/* Source for randomness. This must be able to provide hundreds of bytes per SSH
 * connection without blocking. In addition /dev/random is used for seeding
 * rsa/dss key generation */
#define DROPBEAR_URANDOM_DEV "/dev/urandom"

/* Set this to use PRNGD or EGD instead of /dev/urandom or /dev/random */
/*#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 */
#ifndef MAX_UNAUTH_PER_IP
#define MAX_UNAUTH_PER_IP 5
#endif

/* And then a global limit to avoid chewing memory if connections
 * come from many IPs */
#ifndef MAX_UNAUTH_CLIENTS
#define MAX_UNAUTH_CLIENTS 30
#endif

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

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

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

/* 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 */
#ifndef SFTPSERVER_PATH
#define SFTPSERVER_PATH "/usr/libexec/sftp-server"
#endif

/* 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 DROPBEAR_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. */
#ifndef DEFAULT_RECV_WINDOW
#define DEFAULT_RECV_WINDOW 24576
#endif
/* Maximum size of a received SSH data packet - this _MUST_ be >= 32768
   in order to interoperate with other implementations */
#ifndef RECV_MAX_PAYLOAD_LEN
#define RECV_MAX_PAYLOAD_LEN 32768
#endif
/* Maximum size of a transmitted data packet - this can be any value,
   though increasing it may not make a significant difference. */
#ifndef TRANS_MAX_PAYLOAD_LEN
#define TRANS_MAX_PAYLOAD_LEN 16384
#endif

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

/* If this many KEEPALIVES are sent with no packets received from the
other side, exit. Not run-time configurable - if you have a need
for runtime configuration please mail the Dropbear list */
#define DEFAULT_KEEPALIVE_LIMIT 3

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

/* 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 /* DROPBEAR_OPTIONS_H_ */