pysshconfig's Introduction

pysshconfig

Extremely simple, pure-python library to read ssh_config files. Useful to see what keywords/options are applied to a certain host, just like the official ssh client would.

Requires Python >=3.5

Example usage

Let's say your ~/.ssh/config file looks like this:

Host special.example.net
    User root
    Port 2222

Host *.example.com !insecure.example.com
    ForwardAgent yes
    User johndoe
    PreferredAuthentications publickey

Host *
    ForwardAgent no
    HashKnownHosts no

Then you can parse it like this:

import os.path
import pysshconfig as psc
with open(os.path.expanduser('~/.ssh/config')) as f:
    ssh_config = psc.load(f)

Now check what keywords are applied to a certain host like this:

>>> ssh_config.get_config_for_host('somehost.example.com')
{'ForwardAgent': 'yes', 'User': 'johndoe', 'PreferredAuthentications': 'publickey', 'HashKnownHosts': 'no'}

>>> ssh_config.get_config_for_host('insecure.example.com')
{'ForwardAgent': 'no', 'HashKnownHosts': 'no'}

>>> ssh_config.get_config_for_host('special.example.net')
{'User': 'root', 'Port': '2222', 'Forwardagent': 'yes', 'Preferredauthentications': 'publickey', 'HashKnownHosts': 'no'}

Adding a new Host block is as easy as modifying a list:

>>> myhosts = ['newhost.example.com', '*.www.example.com', '!test.www.example.com']
>>> myoptions = {'user': 'bob', 'port': '8080'}
>>> ssh_config.insert(0, psc.HostBlock(psc.HostList(myhosts), psc.KeywordSet(myoptions)))

>>> psc.dumps(ssh_config)
Host newhost.example.com *.www.example.com !test.www.example.com
    User bob
    Port 8080

Host special.example.net
    User root
    Port 2222

Host *.example.com !insecure.example.com special.example.net
    ForwardAgent yes
    User johndoe
    PreferredAuthentications publickey

Host *
    ForwardAgent no
    HashKnownHosts no

You can modify existing keywords as if they were dictionaries:

>>> hostblocks = ssh_config.get_matching_hosts('host.www.example.com')
>>> for _, kw in hostblocks:
...    kw['user'] = "alice"
...
>>> psc.dumps(ssh_config)
Host newhost.example.com *.www.example.com !test.www.example.com
    User alice
    Port 8080

Host special.example.net
    User root
    Port 2222

Host *.example.com !insecure.example.com special.example.net
    ForwardAgent yes
    User alice
    PreferredAuthentications publickey

Host *
    ForwardAgent no
    HashKnownHosts no
    User alice

Limitations

Formatting from the original file will not be preserved. To be more specific:

The keywords will change to match the correct case ('hashknownhosts' -> 'HashKnownHosts')
Comments and empty lines will be removed

It will validate that the keywords are correct, but it does not perform any validation on their values.

It does not support the Match keyword yet.

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pysshconfig's Issues

Incorrectly drops duplicates of some keywords

First off, thank you for this package, definitely making my life easier. However, I did notice an issue where a keyword (in my case LocalForward) is dropped if it is specified more than once for a host.

Example input:

Host server
     Hostname server.example.com
     ServerAliveInterval 300
     PubkeyAuthentication yes
     IdentitiesOnly no
     LocalForward 8443 api.internal.example.com:443
     LocalForward 9443 api-02.internal.example.com:443

Example program

from pathlib import Path
import pysshconfig


sshconfig_path = Path('./ssh_config')
with sshconfig_path.open('r') as input_fp:
    sshconfig = pysshconfig.load(input_fp)

with sshconfig_path.open('w') as output_fp:
    pysshconfig.dump(results, output_fp)

Expected that the output be the same as the input. Actual:

Host server
     Hostname server.example.com
     ServerAliveInterval 300
     PubkeyAuthentication yes
     IdentitiesOnly no
     LocalForward 8443 api.internal.example.com:443

I am using version 0.0.2

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