mirror of
https://github.com/ovh/the-bastion.git
synced 2025-11-04 11:26:17 +08:00
114 lines
4.8 KiB
Text
114 lines
4.8 KiB
Text
# Hardened SSH bastion config -- modify wisely!
|
|
# Based on https://wiki.mozilla.org/Security/Guidelines/OpenSSH
|
|
# With modifications where applicable/needed
|
|
|
|
# hardened params follow. every non-needed feature is disabled by default,
|
|
# following the principle of least rights and least features (more enabled
|
|
# features mean a more important attack surface).
|
|
|
|
# === FEATURES ===
|
|
|
|
# disable non-needed sshd features
|
|
# mitigates CVE-0216-0778
|
|
UseRoaming no
|
|
# other unwanted features
|
|
Tunnel no
|
|
ForwardAgent no
|
|
ForwardX11 no
|
|
GatewayPorts no
|
|
ControlMaster no
|
|
|
|
# === CRYPTOGRAPHY ===
|
|
|
|
# enforce the use of ssh version 2 protocol, version 1 is disabled.
|
|
# all sshd_config options regarding protocol 1 are therefore omitted.
|
|
Protocol 2
|
|
|
|
# list of allowed ciphers.
|
|
# chacha20-poly1305 is a modern cipher, considered very secure
|
|
# aes is still the standard, we prefer gcm cipher mode, but also
|
|
# allow ctr cipher mode for compatibility (ctr is considered secure)
|
|
# we deny arcfour(rc4), 3des, blowfish and cast
|
|
# for older remote servers (or esoteric hardware), we might need to add: aes256-cbc,aes192-cbc,aes128-cbc
|
|
# known gotchas:
|
|
# - BSD (https://lists.freebsd.org/pipermail/freebsd-bugs/2013-June/053005.html) needs aes256-gcm@openssh.com,aes128-gcm@openssh.com DISABLED
|
|
# - Old Cisco IOS (such as v12.2) only supports aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
|
|
# - Ancient Debians (Sarge) and RedHats (7) only support aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc@lysator.liu.se,aes128-ctr,aes192-ctr,aes256-ctr
|
|
Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
|
|
|
|
# list of allowed message authentication code algorithms.
|
|
# etm (encrypt-then-mac) are considered the more secure, we
|
|
# prefer umac (has been proven secure) then sha2.
|
|
# for older remote servers, fallback to the non-etm version of
|
|
# the algorithms. we deny md5 entirely.
|
|
# for older remote servers (or esoteric hardware), we might need to add: hmac-sha1
|
|
# Known gotchas:
|
|
# - Old Cisco IOS (such as v12.2) only supports hmac-sha1,hmac-sha1-96,hmac-md5,hmac-md5-96
|
|
# - Ancient Debians (Sarge) and RedHats (7) only support hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
|
|
MACs umac-128-etm@openssh.com,umac-64-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128@openssh.com,umac-64@openssh.com,hmac-sha2-512,hmac-sha2-256
|
|
|
|
# List of allowed key exchange algorithms.
|
|
# we prefer curve25519-sha256 which is considered the most modern/secure,
|
|
# and still allow diffie hellman with group exchange using sha256 which is
|
|
# the most secure dh-based kex.
|
|
# we avoid algorithms based on the disputed NIST curves, and anything based
|
|
# on sha1.
|
|
# known gotchas:
|
|
# - Windows needs diffie-hellman-group14-sha1 and also needs to NOT have diffie-hellman-group-exchange-sha1 present in the list AT ALL
|
|
# - OmniOS 5.11 needs diffie-hellman-group1-sha1
|
|
# - Old Cisco IOS (such as v12.2) only supports diffie-hellman-group1-sha1
|
|
# - Ancient Debians (Sarge) and RedHats (7) only support diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1
|
|
KexAlgorithms curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256
|
|
|
|
# === AUTHENTICATION ===
|
|
|
|
# we allow only public key authentication ...
|
|
PubkeyAuthentication yes
|
|
# ... not password nor keyboard-interactive
|
|
# ... (set to yes if sshpass is to be used)
|
|
PasswordAuthentication no
|
|
# ChallengeResponseAuthentication=yes forces KbdInteractiveAuthentication=yes in the openssh code!
|
|
ChallengeResponseAuthentication no
|
|
KbdInteractiveAuthentication no
|
|
# ... not host-based
|
|
HostbasedAuthentication no
|
|
# now we specify the auth methods order we want for manual ssh calls.
|
|
# NOTE1: as per the ssh source code, an auth method omitted hereafter
|
|
# will not be used, even if set to "yes" above.
|
|
# NOTE2: the bastion code (namely, ttyrec), will always set the proper
|
|
# value explicitly on command-line (pubkey OR sshpass), so the value
|
|
# specified hereafter will be ignored. if you want to force-disable
|
|
# a method, set it to "no" in the list above, as those will never be
|
|
# overridden by the code.
|
|
PreferredAuthentications publickey
|
|
|
|
# === LOGIN ###
|
|
|
|
# disable escape character use
|
|
EscapeChar none
|
|
|
|
# detect if a hostkey changed due to DNS spoofing
|
|
CheckHostIP yes
|
|
|
|
# ignore ssh-agent, only use specified keys (-i)
|
|
IdentitiesOnly yes
|
|
# disable auto-lookup of ~/.ssh/id_rsa ~/.ssh/id_ecdsa etc.
|
|
IdentityFile /dev/non/existent/file
|
|
|
|
# carry those vars to the other side (includes LC_BASTION)
|
|
SendEnv LANG LC_*
|
|
|
|
# allow usage of SSHFP DNS records
|
|
VerifyHostKeyDNS ask
|
|
|
|
# yell if remote hostkey changed
|
|
StrictHostKeyChecking ask
|
|
|
|
# === SYSTEM ===
|
|
|
|
# don't hash the users known_hosts files, in the context of a bastion, this adds no security
|
|
HashKnownHosts no
|
|
|
|
# send an ssh ping each 57 seconds to the client and disconnect after 5 no-replies
|
|
ServerAliveInterval 57
|
|
ServerAliveCountMax 5
|