我需要使用 iptables 仅通过 VPN（openvpn）允许 ssh。所有服务（ssh、vpn）都位于同一台机器上。我目前的 vpn 和 ssh 规则：
# set default policy
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT DROP
# flush rules
iptables -t nat -F
iptables -t mangle -F
iptables -F
iptables -X
# allow localhost
iptables -A INPUT -i $LO -j ACCEPT
iptables -A OUTPUT -o $LO -j ACCEPT
# security
iptables -A INPUT -p tcp ! --syn -m conntrack --ctstate NEW -j DROP -m comment --comment "first tcp segment require SYN bit"
iptables -A INPUT -p tcp --tcp-flags ALL ALL -j DROP -m comment --comment "drop XMAS packets"
iptables -A INPUT -p tcp --tcp-flags ALL NONE -j DROP -m comment --comment "drop NULL packets"
iptables -A INPUT -p icmp --icmp-type address-mask-request -j DROP -m comment --comment "drop ICMP smurf attacks"
iptables -A INPUT -p icmp --icmp-type timestamp-request -j DROP
iptables -A INPUT -p icmp --icmp-type router-solicitation -j DROP
iptables -A INPUT -p icmp -m limit --limit 2/second -j ACCEPT
iptables -A INPUT -m conntrack --ctstate INVALID -j DROP -m comment --comment "drop mangled (invalid) packets"
iptables -A FORWARD -m conntrack --ctstate INVALID -j DROP
iptables -A OUTPUT -m conntrack --ctstate INVALID -j DROP
# allow VPN traffic
iptables -A INPUT -i $WAN -p tcp -m conntrack --ctstate NEW,ESTABLISHED --dport $PORT_OPENVPN -j ACCEPT
iptables -A OUTPUT -o $WAN -p tcp -m conntrack --ctstate ESTABLISHED --sport $PORT_OPENVPN -j ACCEPT
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o $WAN -j MASQUERADE
iptables -A FORWARD -s 10.8.0.0/24 -o $WAN -j ACCEPT
iptables -A FORWARD -i $TUN -o $WAN -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i $WAN -o $TUN -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
# allow SSH
iptables -t nat -I POSTROUTING -p tcp -m tcp --sport $PORT_SSH -o $TUN -j MASQUERADE
iptables -A FORWARD -i $TUN -o $WAN -p tcp --dport $PORT_SSH -j ACCEPT
iptables -A FORWARD -i $WAN -o $TUN -p tcp --sport $PORT_SSH -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport $PORT_SSH -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp --sport $PORT_SSH -j ACCEPT
但目前 ssh 无法工作，无论是通过 vpn 还是不使用 vpn。我做错了什么？
更新输出ssh -vv：
OpenSSH_for_Windows_8.1p1, LibreSSL 3.0.2
debug1: Reading configuration data .ssh/config
debug2: resolve_canonicalize: hostname <VPS IP ADDRESS HERE> is address
debug2: ssh_connect_direct
debug1: Connecting to <VPS IP ADDRESS HERE> [<VPS IP ADDRESS HERE>] port 22.
debug1: Connection established.
debug1: identity file .ssh/id_rsa type -1
debug1: identity file .ssh/id_rsa-cert type -1
debug1: identity file .ssh/id_dsa type -1
debug1: identity file .ssh/id_dsa-cert type -1
debug1: identity file .ssh/id_ecdsa type -1
debug1: identity file .ssh/id_ecdsa-cert type -1
debug1: identity file .ssh/id_ed25519 type -1
debug1: identity file .ssh/id_ed25519-cert type -1
debug1: identity file .ssh/id_xmss type -1
debug1: identity file .ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_for_Windows_8.1
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.6p1 Ubuntu-4ubuntu0.5
debug1: match: OpenSSH_7.6p1 Ubuntu-4ubuntu0.5 pat OpenSSH_7.0*,OpenSSH_7.1*,OpenSSH_7.2*,OpenSSH_7.3*,OpenSSH_7.4*,OpenSSH_7.5*,OpenSSH_7.6*,OpenSSH_7.7* compat 0x04000002
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to <VPS IP ADDRESS HERE>:22 as '<LOGIN HERE>'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,rsa-sha2-512,rsa-sha2-256,ssh-rsa,[email protected],ssh-ed25519
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:qUdNYwEs+cvEVkMKTz4RNOObOBsIByhRaehiNvybIi4
debug1: Host '<VPS IP ADDRESS HERE>' is known and matches the ECDSA host key.
debug1: Found key in .ssh/known_hosts:3
debug2: set_newkeys: mode 1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey in after 134217728 blocks
debug1: pubkey_prepare: ssh_get_authentication_socket: No such file or directory
debug1: Will attempt key: .ssh/id_rsa
debug1: Will attempt key: .ssh/id_dsa
debug1: Will attempt key: .ssh/id_ecdsa
debug1: Will attempt key: .ssh/id_ed25519
debug1: Will attempt key: .ssh/id_xmss
debug2: pubkey_prepare: done
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Trying private key: .ssh/id_rsa
debug1: Trying private key: .ssh/id_dsa
debug1: Trying private key: .ssh/id_ecdsa
debug1: Trying private key: .ssh/id_ed25519
debug1: Trying private key: .ssh/id_xmss
debug2: we did not send a packet, disable method
debug1: Next authentication method: password
debug1: read_passphrase: can't open /dev/tty: No such file or directory
<LOGIN HERE>@<VPS IP ADDRESS HERE>'s password:
debug2: we sent a password packet, wait for reply
debug1: Authentication succeeded (password).
Authenticated to <VPS IP ADDRESS HERE> ([<VPS IP ADDRESS HERE>]:22).
debug1: channel 0: new [client-session]
debug2: channel 0: send open
debug1: Requesting [email protected]
debug1: Entering interactive session.
debug1: pledge: network
debug1: ENABLE_VIRTUAL_TERMINAL_INPUT is supported. Reading the VTSequence from console
debug1: ENABLE_VIRTUAL_TERMINAL_PROCESSING is supported. Console supports the ansi parsing
debug1: client_input_global_request: rtype [email protected] want_reply 0
debug2: channel_input_open_confirmation: channel 0: callback start
debug2: fd 3 setting TCP_NODELAY
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug2: channel 0: request shell confirm 1
debug2: channel_input_open_confirmation: channel 0: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel_input_status_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug2: channel_input_status_confirm: type 99 id 0
debug2: shell request accepted on channel 0