ssh_config

by kevinburke

kevinburke / ssh_config

Go parser for ssh_config files

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ssh_config

This is a Go parser for

ssh_config
files. Importantly, this parser attempts to preserve comments in a given file, so you can manipulate a
ssh_config
file from a program, if your heart desires.

It's designed to be used with the excellent x/crypto/ssh package, which handles SSH negotiation but isn't very easy to configure.

The

ssh_config
Get()
and
GetStrict()
functions will attempt to read values from
$HOME/.ssh/config
and fall back to
/etc/ssh/ssh_config
. The first argument is the host name to match on, and the second argument is the key you want to retrieve.
port := ssh_config.Get("myhost", "Port")

You can also load a config file and read values from it.

var config = `
Host *.test
  Compression yes
`

cfg, err := ssh_config.Decode(strings.NewReader(config)) fmt.Println(cfg.Get("example.test", "Port"))

Some SSH arguments have default values - for example, the default value for

KeyboardAuthentication
is
"yes"
. If you call Get(), and no value for the given Host/keyword pair exists in the config, we'll return a default for the keyword if one exists.

Manipulating SSH config files

Here's how you can manipulate an SSH config file, and then write it back to disk.

f, _ := os.Open(filepath.Join(os.Getenv("HOME"), ".ssh", "config"))
cfg, _ := ssh_config.Decode(f)
for _, host := range cfg.Hosts {
    fmt.Println("patterns:", host.Patterns)
    for _, node := range host.Nodes {
        // Manipulate the nodes as you see fit, or use a type switch to
        // distinguish between Empty, KV, and Include nodes.
        fmt.Println(node.String())
    }
}

// Print the config to stdout: fmt.Println(cfg.String())

Spec compliance

Wherever possible we try to implement the specification as documented in the

ssh_config
manpage. Unimplemented features should be present in the issues list.

Notably, the

Match
directive is currently unsupported.

Errata

This is the second comment-preserving configuration parser I've written, after an /etc/hosts parser. Eventually, I will write one for every Linux file format.

Donating

Donations free up time to make improvements to the library, and respond to bug reports. You can send donations via Paypal's "Send Money" feature to [email protected] Donations are not tax deductible in the USA.

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