SSH de dentro do NAT por meio de travamentos de IP público

1

Por algum motivo desconhecido, meu cliente SSH será interrompido se eu me conectar a um servidor SSH encaminhado por porta de dentro da rede NAT. Se eu SSH de fora da rede (por exemplo, de uma instância do EC2) através do roteador NAT ele funciona bem. Se eu SSH de um host dentro da rede NAT para o outro também funciona bem. Se eu SSH para a porta encaminhada 22 no endereço público ou privado do roteador NAT, o cliente SSH irá travar.

Host A (private: A.A.A.A): SSH Client
HOST B (private: B.B.B.B): SSH Server
EC2 Host (public: E.E.E.E): SSH Client
ROUTER (Public: R.R.R.R): NAT Router
ROUTER (private: r.r.r.r): NAT Router

Aqui está o que eu descobri empiricamente

A.A.A.A -> B.B.B.B works
B.B.B.B -> A.A.A.A works
E.E.E.E -> R.R.R.R -> B.B.B.B works
A.A.A.A -> R.R.R.R -> B.B.B.B does not work
A.A.A.A -> r.r.r.r -> B.B.B.B does not work

A última mensagem que o cliente SSH emite antes de pendurar é

debug1: client_input_global_request: rtype [email protected] want_reply 0

Aqui está o log ssh ao conectar do Host A ao endereço particular do Roteador:

OpenSSH_7.4p1, OpenSSL 1.0.2k  26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolving "10.0.0.1" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 10.0.0.1 [10.0.0.1] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 10.0.0.1:22 as 'me'
debug3: put_host_port: [10.0.0.1]:22
debug3: hostkeys_foreach: reading file "/home/me/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/me/.ssh/known_hosts:8
debug3: load_hostkeys: loaded 1 keys from [10.0.0.1]:22
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
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-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc
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,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]
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
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:2C4WXSvT20pE6QlmenhYFyO1TdTAth9MsbN86nYGi7s
debug3: put_host_port: [10.0.0.1]:22
debug3: put_host_port: [10.0.0.1]:22
debug3: hostkeys_foreach: reading file "/home/me/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/me/.ssh/known_hosts:8
debug3: load_hostkeys: loaded 1 keys from [10.0.0.1]:22
debug3: hostkeys_foreach: reading file "/home/me/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/me/.ssh/known_hosts:8
debug3: load_hostkeys: loaded 1 keys from [10.0.0.1]:22
debug1: Host '[10.0.0.1]:22' is known and matches the ECDSA host key.
debug1: Found key in /home/me/.ssh/known_hosts:8
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug2: key: /home/me/.ssh/id_rsa ((nil))
debug2: key: /home/me/.ssh/id_dsa ((nil))
debug2: key: /home/me/.ssh/id_ecdsa ((nil))
debug2: key: /home/me/.ssh/id_ed25519 ((nil))
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /home/me/.ssh/id_rsa
debug3: no such identity: /home/me/.ssh/id_rsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_dsa
debug3: no such identity: /home/me/.ssh/id_dsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_ecdsa
debug3: no such identity: /home/me/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_ed25519
debug3: no such identity: /home/me/.ssh/id_ed25519: No such file or directory
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
debug3: send packet: type 50
debug2: we sent a password packet, wait for reply
debug3: receive packet: type 52
debug1: Authentication succeeded (password).
Authenticated to 10.0.0.1 ([10.0.0.1]:22).
debug2: fd 5 setting O_NONBLOCK
debug3: fd 6 is O_NONBLOCK
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug3: send packet: type 90
debug1: Requesting [email protected]
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: network
debug3: receive packet: type 80
debug1: client_input_global_request: rtype [email protected] want_reply 0

Aqui está o log ssh ao conectar de A a B diretamente:

OpenSSH_7.4p1, OpenSSL 1.0.2k  26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolving "10.0.0.2" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 10.0.0.2 [10.0.0.2] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 10.0.0.2:22 as 'me'
debug3: hostkeys_foreach: reading file "/home/me/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/me/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from 10.0.0.2
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
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-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc
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,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]
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
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:2C4WXSvT20pE6QlmenhYFyO1TdTAth9MsbN86nYGi7s
debug3: hostkeys_foreach: reading file "/home/me/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/me/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from 10.0.0.2
debug1: Host '10.0.0.2' is known and matches the ECDSA host key.
debug1: Found key in /home/me/.ssh/known_hosts:1
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug2: key: /home/me/.ssh/id_rsa ((nil))
debug2: key: /home/me/.ssh/id_dsa ((nil))
debug2: key: /home/me/.ssh/id_ecdsa ((nil))
debug2: key: /home/me/.ssh/id_ed25519 ((nil))
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /home/me/.ssh/id_rsa
debug3: no such identity: /home/me/.ssh/id_rsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_dsa
debug3: no such identity: /home/me/.ssh/id_dsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_ecdsa
debug3: no such identity: /home/me/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_ed25519
debug3: no such identity: /home/me/.ssh/id_ed25519: No such file or directory
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
debug3: send packet: type 50
debug2: we sent a password packet, wait for reply
debug3: receive packet: type 52
debug1: Authentication succeeded (password).
Authenticated to 10.0.0.2 ([10.0.0.2]:22).
debug2: fd 5 setting O_NONBLOCK
debug3: fd 6 is O_NONBLOCK
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug3: send packet: type 90
debug1: Requesting [email protected]
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: network
debug3: receive packet: type 80
debug1: client_input_global_request: rtype [email protected] want_reply 0
debug3: receive packet: type 91
debug2: callback start
debug2: fd 3 setting TCP_NODELAY
debug3: ssh_packet_set_tos: set IP_TOS 0x08
debug2: client_session2_setup: id 0
debug1: Sending command: ls
debug2: channel 0: request exec confirm 1
debug3: send packet: type 98
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel 0: rcvd adjust 2097152
debug3: receive packet: type 99
debug2: channel_input_status_confirm: type 99 id 0
debug2: exec request accepted on channel 0
aur
bin
documents
keys
lib
music
photos
src
debug3: receive packet: type 96
debug2: channel 0: rcvd eof
debug2: channel 0: output open -> drain
debug2: channel 0: obuf empty
debug2: channel 0: close_write
debug2: channel 0: output drain -> closed
debug3: receive packet: type 98
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug3: receive packet: type 98
debug1: client_input_channel_req: channel 0 rtype [email protected] reply 0
debug2: channel 0: rcvd eow
debug2: channel 0: close_read
debug2: channel 0: input open -> closed
debug3: receive packet: type 97
debug2: channel 0: rcvd close
debug3: channel 0: will not send data after close
debug2: channel 0: almost dead
debug2: channel 0: gc: notify user
debug2: channel 0: gc: user detached
debug2: channel 0: send close
debug3: send packet: type 97
debug2: channel 0: is dead
debug2: channel 0: garbage collecting
debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
  #0 client-session (t4 r0 i3/0 o3/0 fd -1/-1 cc -1)

debug3: send packet: type 1
debug1: fd 1 clearing O_NONBLOCK
debug3: fd 2 is not O_NONBLOCK
Transferred: sent 1816, received 2780 bytes, in 0.1 seconds
Bytes per second: sent 17844.2, received 27316.5
debug1: Exit status 0
    
por Huckle 13.02.2017 / 01:13

1 resposta

2

Este é realmente um comportamento bastante normal para o NAT. Para contornar isso, uma prática comum é usar o DNS local para forçar a resolução para o endereço IP privado, em vez do público.

Por exemplo, o Host B teria um registro DNS público de R.R.R.R para que o resto do mundo possa acessá-lo. Mas, se você alterar o DNS local (ou o arquivo / etc / hosts no Host A) para forçar o nome do host do Host B a ser resolvido para B.B.B.B, você poderá endereçar seu servidor localmente.

Este método obviamente só funciona se você usa DNS, mas é um método que eu confio muito por causa desse comportamento NAT. Além disso, não faz muito sentido que as solicitações atinjam seu roteador se você estiver se conectando a um recurso local, especialmente em uma rede maior.

Este artigo descreve este tipo de comportamento de NAT, bem como uma possível solução usando iptables se você não quiser usar o DNS:

    
por 13.02.2017 / 05:49