Reading the ~/.ssh/config file

[andylaw]

I've got a lot of SSH configuration set up in my OpenSSH config file. Tabby makes a stab at reading it, and kind-of does well enough but the file parsing code is naive when it comes to inheritance of configuration. I started to look at re-writing the function, but then I began to wonder if it was actually necessary. The code stores some features of the settings into the SSHProfile structures but does it actually use them or does it rely on OpenSSH to have done its own parsing for the actual functionality.

If the answer is "yes, Tabby does use all the SSHProfile attributes and makes its own connections" then I'll try to take a better look at improving the code and implementing the inheritance rules. If not, then I'll look at how the code might be modified to be smarter about parsing the host names.

As an example of what is giving me grief at the moment, if I have two hosts with mostly shared details, but just a single distinguishing feature between them, then I have the following in my config file...

# Shared stuff here
Host  conn_1 conn_2
    ...shared details...

Host  conn_1
    ...conn_1 specifics...

Host  conn_2
    ...conn_2 specifics...

That should give me two profiles in the "Imported from SSH config" group, but it gives me 3 i.e. conn_1, conn_2 and conn_1 conn_2, the last of which is bogus

[Eugeny]

You're correct! Currently the OpenSSH config parser is somewhat naive and only covers basic syntax.
The file is parsed into SSHProfiles which are then provided as built-in profiles that you connect to, Tabby doesn't interact with OpenSSH directly at any point

[andylaw]

So in my example above, the conn_1 profile wouldn't work properly because it doesn't inherit the shared parts? I suspected that Tabby was just calling ssh conn_1 under the hood, leaving the heavy lifting to SSH but now I realise that's not the case. Is there an open issue relating to this that I can look to hop onto, assuming I can find any spare time?

[Eugeny]

Yes! I think this is the closest one: #10012

If you decide to work on this, the place to look at is the OpenSSHImporter class in https://github.com/Eugeny/tabby/blob/master/tabby-electron/src/sshImporters.ts#L15

[andylaw]

Working on this now. I confess that Typescript is not my first language, so apologies for daft questions, but why is sshimporters.ts in the tabby-electron package and not the tabby-ssh package?

I think I have a mostly functional function that reads in the SSH config file and converts all the 'complete' (no wildcards in names, includes at least a Hostname) Hosts into SSHProfile objects. It relies on an additional third party library to do the heavy lifting. As I said, Typescript is not my tool of choice for day-to-day work, so I'm not sure which package.json file I should add that to (the one inside tabby-electron, or the top-level one), nor whether it should in dependencies (where I think it should be), or dev-dependencies which is where I can see some libraries that I suspect are required in the final packaged app.

I'm hoping to have a pull-request available for initial review and feedback sometime through the week, but paid work may get the way of that

[Eugeny]

The reason for separation is because it has a NodeJS dependency (fs) and core packages are nodejs-free.

New dependencies go into their respective plugin's package.json, into devDependencies if they are going to be bundled by webpack (default) or dependencies if they are a webpack external module.

[andylaw]

@Eugeny - I've now got code that's successfully reading in the SSHConfig file and converting it into SSHProfile objects. It returns a list of SSHProfile objects having parsed all the wildcard and multiple entries for a single 'Host' and the list obtained contains a single, complete entry for each Host that has at least a Hostname specified.

The problem that I've now run into is that Hosts that define JumpHosts fail because Tabby doesn't find the JumpHost in its config. I suspect that this may be because it only searches in its own config, rather than the externally-defined SSHConfig because I can see the jump host in the list of config-derived profiles and it connects as I would expect if I use it explicitly. Is that guess likely to be on the money?

I'm starting at Line 79 in sshTab.component.ts under tabby-sh. Any thoughts before I dig too much deeper?

[andylaw]

@peix187 - I wasn't aware that the nightly gets built on a commit.

On a separate issue, the code (when it can be persuaded to compile properly) currently treats SSH Config settings and the profiles created within Tabby as separate things. Are there circumstances where you would ever want the SSH Config to provide a platform on which you built Tabby profiles. For example, defining a set of wildcard configurations in SSH Config and then using those to run tabby profiles with a minimal set of additional data added in?

I don't have that need myself (just now), but I can readily imagine it being a requirement for someone.

[peix187]

@andylaw, yes i use wildcard in my configuration. Look this simple configuration and the result in Tabby profiles.

Host srv-a
    Hostname 172.22.0.1

Host srv-*
    User admin
    IdentitiesOnly yes
    IdentityFile ~/.ssh/mysshkey

Host *
    NumberOfPasswordPrompts 5

For me Tabby should display only one profile (with a Hostname parameter) but apply wildcard blocks for all correspondent "normal" block.

[Eugeny]

I'm currently working on getting validated for a new code signing certificate, until then windows builds have to be built manually

[andylaw]

@peix187 - your scenario works as both you and I would expect in my build. Hopefully once the Windows build is back up and running then you'll be able to check that. However, I was asking about a potential situation where your wildcards were defined in SSH Config, but your specific Hosts were created by adding a Tabby Profile using the "New" button in the Profiles and Connections tab. Would you expect/want a hostname entered in that profile to be processed through the SSH Config settings to automatically fill in details?

[peix187]

@andylaw - Thank for your propose but i use only the SSH Config file for define hosts. If i have time this night i wild try to build the windows package for testing your patch.