Compose: SSHException: Server not found in known_hosts when using non-default SSH port

[Archomeda]

Description of the issue

When using a non-default SSH port, docker-compose doesn't want to execute any command (e.g. docker-compose pull) on the remote host. It fails with the server not being found in known_hosts.
On the same remote host, when using the default SSH port 22, it does succeed in executing the command. Docker itself has no issues as far as I can tell.

In both cases, the server is in the known hosts file, and connecting normally through ssh directly does work.

Context information (for bug reports)

Output of docker-compose version

docker-compose version 1.24.1, build 4667896
docker-py version: 3.7.3
CPython version: 3.7.5
OpenSSL version: OpenSSL 1.1.1d  10 Sep 2019

Output of docker version

Client: Docker Engine - Community
 Version:           19.03.4
 API version:       1.40
 Go version:        go1.12.10
 Git commit:        9013bf583a
 Built:             Fri Oct 18 15:49:05 2019
 OS/Arch:           linux/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          19.03.4
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.12.10
  Git commit:       9013bf583a
  Built:            Fri Oct 18 15:55:51 2019
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          v1.2.10
  GitCommit:        b34a5c8af56e510852c35414db4c1f4fa6172339
 runc:
  Version:          1.0.0-rc8+dev
  GitCommit:        3e425f80a8c931f88e6d94a8c831b9d5aa481657
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683

Output of docker-compose config
I think this is irrelevant in this issue, but in any case:

services:
  server:
    environment:
      MINECRAFT_ARGUMENTS: -Xms215M -Xmx1024M
      MINECRAFT_PATH: minecraft/server.jar
      PROXY_PORT: '27035'
    image: registry.gitlab.com/archomeda/minecraft-reverse-proxy
    ports:
    - published: 27035
      target: 27035
    restart: unless-stopped
    volumes:
    - /home/docker/data/minecraft-reverse-proxy-vanilla:/app/storage:rw
version: '3.3'

Steps to reproduce the issue

1. Start an SSH server on a non-default SSH port, e.g. 2222
2. ssh-keyscan -H -p <port> <host> and add the contents to ~/.ssh/known_hosts
3. export DOCKER_HOST=ssh://<host>:<port>
4. Run e.g. docker-compose pull

Observed result

The command fails with SSHException: Server '[\

Expected result

The command to succeed.

Stacktrace / full error message

Connected (version 2.0, client OpenSSH_7.6p1)
Traceback (most recent call last):
  File "/usr/bin/docker-compose", line 10, in <module>
    sys.exit(main())
  File "/usr/lib/python3.7/site-packages/compose/cli/main.py", line 71, in main
    command()
  File "/usr/lib/python3.7/site-packages/compose/cli/main.py", line 124, in perform_command
    project = project_from_options('.', options)
  File "/usr/lib/python3.7/site-packages/compose/cli/command.py", line 42, in project_from_options
    compatibility=options.get('--compatibility'),
  File "/usr/lib/python3.7/site-packages/compose/cli/command.py", line 123, in get_project
    host=host, environment=environment
  File "/usr/lib/python3.7/site-packages/compose/cli/command.py", line 94, in get_client
    environment=environment, tls_version=get_tls_version(environment)
  File "/usr/lib/python3.7/site-packages/compose/cli/docker_client.py", line 127, in docker_client
    client = APIClient(**kwargs)
  File "/usr/lib/python3.7/site-packages/docker/api/client.py", line 166, in __init__
    base_url, timeout, pool_connections=num_pools
  File "/usr/lib/python3.7/site-packages/docker/transport/sshconn.py", line 84, in __init__
    self._connect()
  File "/usr/lib/python3.7/site-packages/docker/transport/sshconn.py", line 94, in _connect
    parsed.hostname, parsed.port, parsed.username,
  File "/usr/lib/python3.7/site-packages/paramiko/client.py", line 416, in connect
    self, server_hostkey_name, server_key
  File "/usr/lib/python3.7/site-packages/paramiko/client.py", line 824, in missing_host_key
    "Server {!r} not found in known_hosts".format(hostname)
paramiko.ssh_exception.SSHException: Server '[<host>]:<port>' not found in known_hosts

Additional information

N/A

[mnzaki]

I think this issue goes further: if the server hostname is not exactly as it is in the known_hosts file, things fail.
In my case, I had the server IP in ~/.ssh/known_hosts but was calling the docker-compose command with a host name, which it obviously didn't find in the known_hosts file.

Quick solution: set DOCKER_HOST the same way it appears in your known_hosts file

But otherwise, more robust code in paramiko would be nice

[Bessonov]

Run in the same issue. Usage of hostname doesn't worked for me, but it works with the IP address.

[silviuvulcan]

Same issue:

export DOCKER_HOST="ssh://[email protected]:1234"
docker-compose pull
[...]
paramiko.ssh_exception.SSHException: Server '[host.example.com]:1234' not found in known_hosts

I cleaned known_hosts and logged in once manually. I noticed this:

ssh host.example.com
Warning: Permanently added '[1.2.3.4]:2202' (ECDSA) to the list of known hosts.

So now if I export DOCKER_HOST="ssh://[email protected]:1234"

Suddenly it works. I never had this issue until ssh daemon was switched away from the default port.
I feel this shouldn't require so much fuss simply to run.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[Bessonov]

Activity.