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93 lines
2.9 KiB
Markdown
93 lines
2.9 KiB
Markdown
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# ssh_config
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This is a Go parser for `ssh_config` files. Importantly, this parser attempts
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to preserve comments in a given file, so you can manipulate a `ssh_config` file
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from a program, if your heart desires.
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It's designed to be used with the excellent
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[x/crypto/ssh](https://golang.org/x/crypto/ssh) package, which handles SSH
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negotiation but isn't very easy to configure.
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The `ssh_config` `Get()` and `GetStrict()` functions will attempt to read values
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from `$HOME/.ssh/config` and fall back to `/etc/ssh/ssh_config`. The first
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argument is the host name to match on, and the second argument is the key you
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want to retrieve.
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```go
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port := ssh_config.Get("myhost", "Port")
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```
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Certain directives can occur multiple times for a host (such as `IdentityFile`),
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so you should use the `GetAll` or `GetAllStrict` directive to retrieve those
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instead.
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```go
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files := ssh_config.GetAll("myhost", "IdentityFile")
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```
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You can also load a config file and read values from it.
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```go
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var config = `
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Host *.test
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Compression yes
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`
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cfg, err := ssh_config.Decode(strings.NewReader(config))
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fmt.Println(cfg.Get("example.test", "Port"))
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```
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Some SSH arguments have default values - for example, the default value for
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`KeyboardAuthentication` is `"yes"`. If you call Get(), and no value for the
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given Host/keyword pair exists in the config, we'll return a default for the
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keyword if one exists.
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### Manipulating SSH config files
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Here's how you can manipulate an SSH config file, and then write it back to
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disk.
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```go
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f, _ := os.Open(filepath.Join(os.Getenv("HOME"), ".ssh", "config"))
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cfg, _ := ssh_config.Decode(f)
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for _, host := range cfg.Hosts {
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fmt.Println("patterns:", host.Patterns)
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for _, node := range host.Nodes {
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// Manipulate the nodes as you see fit, or use a type switch to
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// distinguish between Empty, KV, and Include nodes.
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fmt.Println(node.String())
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}
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}
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// Print the config to stdout:
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fmt.Println(cfg.String())
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```
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## Spec compliance
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Wherever possible we try to implement the specification as documented in
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the `ssh_config` manpage. Unimplemented features should be present in the
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[issues][issues] list.
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Notably, the `Match` directive is currently unsupported.
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[issues]: https://github.com/kevinburke/ssh_config/issues
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## Errata
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This is the second [comment-preserving configuration parser][blog] I've written, after
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[an /etc/hosts parser][hostsfile]. Eventually, I will write one for every Linux
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file format.
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[blog]: https://kev.inburke.com/kevin/more-comment-preserving-configuration-parsers/
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[hostsfile]: https://github.com/kevinburke/hostsfile
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## Donating
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I don't get paid to maintain this project. Donations free up time to make
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improvements to the library, and respond to bug reports. You can send donations
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via Paypal's "Send Money" feature to kev@inburke.com. Donations are not tax
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deductible in the USA.
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You can also reach out about a consulting engagement: https://burke.services
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