Configuración ssh para múltiples saltos de proxy

Question

Tengo una configuración en la que necesito realizar 2 saltos de proxy para poder conectarme a mi servidor D. Efectivamente, desde A, necesito conectarme a B, desde donde necesito conectarme C(que solo permite conexiones desde B) desde donde luego puedo conectarme D(que solo acepta conexiones desde C).

En B, usando la configuración ssh, puedo conectarme Dsimplemente escribiendo ssh D, por lo que pensé que podría usar esta configuración Apara conectarme a D:

Host B
    hostname 127.0.0.1
    user myUser
    Port 43099
    IdentityFile ~/.ssh/id_rsa

Host D
    hostname D
    ProxyJump B
  

y luego conectarse desde Apara conectarse a Dtravés de ssh D.

Sin embargo, este es el error que recibo de esto:

debug1: Reading configuration data /home/MyUser/.ssh/config
debug1: /home/MyUser/.ssh/config line 17: Applying options for D
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Setting implicit ProxyCommand from ProxyJump: ssh -v -W '[%h]:%p' B
debug1: Authenticator provider $SSH_SK_PROVIDER did not resolve; disabling
debug1: Executing proxy command: exec ssh -v -W '[D]:22' B
debug1: Local version string SSH-2.0-OpenSSH_8.8
OpenSSH_8.8p1, OpenSSL 1.1.1m  14 Dec 2021
debug1: Reading configuration data /home/MyUser/.ssh/config
debug1: /home/MyUser/.ssh/config line 7: Applying options for B
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Authenticator provider $SSH_SK_PROVIDER did not resolve; disabling
debug1: Connecting to 127.0.0.1 [127.0.0.1] port 43023.
debug1: Connection established.
debug1: identity file /home/MyUser/.ssh/id_rsa type 0
debug1: identity file /home/MyUser/.ssh/id_rsa-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.8
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.6
debug1: compat_banner: match: OpenSSH_8.6 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 127.0.0.1:43023 as 'MyUser'
debug1: load_hostkeys: fopen /home/MyUser/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ssh-ed25519
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: SSH2_MSG_KEX_ECDH_REPLY received
debug1: Server host key: ssh-ed25519 SHA256:to5+n56a6Zj+sbTnMghZGehX2OX5cn29HWbje55WJHU
debug1: load_hostkeys: fopen /home/MyUser/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: Host '[127.0.0.1]:43023' is known and matches the ED25519 host key.
debug1: Found key in /home/MyUser/.ssh/known_hosts:45
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: Will attempt key: /home/MyUser/.ssh/id_rsa RSA SHA256:d6hsPtnc6TWfm9j5lOClBzD4ylE+ww/tg9BE7qP8DlE explicit
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,[email protected],ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected]>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug1: Next authentication method: publickey
debug1: Offering public key: /home/MyUser/.ssh/id_rsa RSA SHA256:d6hsPtnc6TWfm9j5lOClBzD4ylE+ww/tg9BE7qP8DlE explicit
debug1: Server accepts key: /home/MyUser/.ssh/id_rsa RSA SHA256:d6hsPtnc6TWfm9j5lOClBzD4ylE+ww/tg9BE7qP8DlE explicit
Authenticated to 127.0.0.1 ([127.0.0.1]:43023) using "publickey".
debug1: channel_connect_stdio_fwd: D:22
debug1: channel 0: new [stdio-forward]
debug1: getpeername failed: Bad file descriptor
debug1: Requesting [email protected]
debug1: Entering interactive session.
debug1: pledge: filesystem full
debug1: client_input_global_request: rtype [email protected] want_reply 0
debug1: client_input_hostkeys: searching /home/MyUser/.ssh/known_hosts for [127.0.0.1]:43023 / (none)
debug1: client_input_hostkeys: searching /home/MyUser/.ssh/known_hosts2 for [127.0.0.1]:43023 / (none)
debug1: client_input_hostkeys: hostkeys file /home/MyUser/.ssh/known_hosts2 does not exist
debug1: client_input_hostkeys: host key found matching a different name/address, skipping UserKnownHostsFile update
debug1: Remote: /Users/Hendrik/.ssh/authorized_keys:3: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Remote: /Users/Hendrik/.ssh/authorized_keys:3: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
channel 0: open failed: connect failed: nodename nor servname provided, or not known
stdio forwarding failed
kex_exchange_identification: Connection closed by remote host
Connection closed by UNKNOWN port 65535

Parece que la configuración ssh activada Bno se lee en absoluto.

Mi configuración ssh Bse ve así:

Host C
  HostName C
  User MyUser
  ForwardX11Trusted yes
  ForwardX11 yes

Host D
  User MyUser
  HostName D
  ProxyCommand ssh %r@C -W %h:22
  RemoteForward 26512 github.com:22
  Compression yes
  ForwardX11Trusted yes
  ForwardX11 yes
  DynamicForward 10080
  ControlMaster auto
  ControlPath ~/.ssh/masters/%C

¿Hay alguna manera de editar la configuración ssh Ade manera que pueda conectarme de Aa Da ssh D?

Answer 1

Cuando se utiliza el salto de proxy, todas las conexiones ssh se originan en el cliente original (A en este caso) y los nodos intermedios son solo puntos finales del túnel. Entonces, en su caso, todas las configuraciones (incluidos los archivos de clave privada) deben estar en A y se verían así (suponiendo que use el mismo archivo de identidad para los 3 hosts):

Host B
    hostname 127.0.0.1
    user myUser
    Port 43099
    IdentityFile ~/.ssh/id_rsa
Host C
    ProxyJump B
    IdentityFile ~/.ssh/id_rsa
    # Any additional options for connecting to C
Host D
    ProxyJump C
    IdentityFile ~/.ssh/id_rsa
    # Any additional options for connecting to D

Cuando usted ssh D, el cliente ssh en A realizará la siguiente serie de sesiones ssh:

1. A -> B (directamente a través de la red)
2. A -> C (túnel a través de la conexión A->B, luego directamente a través de la red de B a C)
3. A -> D (tunelizado a través de la conexión A->C (que está tunelizado a través de A->B), luego directamente a través de la red de C a D)