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Sylvie Crowe
cba6b6a60f
* add function that can clear cached config files Once the first call to `Get()`, `GetStrict()`, `GetAll()`, or`GetAllStrict()` has been made, the contents of the config files will be cached for all future calls to any of those functions. This can be frustrating if the user wants to capture changes to the config file that were made externally. This change adds the `ClearCachedConfigs()` function to provide control over that. * change ClearCachedConfigs to ReloadConfigs Clearing cached data is somewhat vague and could be more confusing to users who are not familiar with this library. But Reloading the config data is very straightforward. For this reason, the ability to clear the cache has been replaced with the ability to reload. The reload simply clears the cache and then loads the contents again. Additionally, this contains a bug fix that ensure the loadConfigs pointer is set to a non-null value before it is used. * add tests for reloading ssh config files This adds 2 tests. The first checks that ssh config data is cached and does not update if the file changes afterward. The second checks that the `ReloadConfigs()` function will discard the cached data and load the current config file contents.
103 lines
3.2 KiB
Markdown
103 lines
3.2 KiB
Markdown
# 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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### Reloading SSH config files
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Once the first call to `Get()`, `GetStrict()`, `GetAll()`, or `GetAllStrict()`
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has been made, the contents of the config files will be cached for all future
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calls to any of those functions. The `ReloadConfigs()` function will reset
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this cache and replace it with the current config file contents.
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```go
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ssh_config.ReloadConfigs()
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```
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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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## Sponsorships
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Thank you very much to Tailscale and Indeed for sponsoring development of this
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library. [Sponsors][sponsors] will get their names featured in the README.
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You can also reach out about a consulting engagement: https://burke.services
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[sponsors]: https://github.com/sponsors/kevinburke
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