SSH Agent with Powershell

Another "note to my future self", recoded here for posterity.

Today I finally got around to making SSH agent work in Powershell with Git.  For the last year or so, I haven't had to deal with because my work mostly involved writing PHP code inside of WSL.  In that scenario, you're essentially using Linux, so ssh-agent works just fine.

But on native Windows with Powershell...not so much.

I mean, sure, I could just use Git BASH.  But why would I want to do that?  Powershell is awesome, and even if I probably know BASH better, I prefer Powershell.

But it turns out it wasn't all that difficult to get things working in Powershell.  There were two pieces to it:

  1. Use the right SSH agent (i.e. the one that comes with Git).
  2. Write a Powershell adapter for it.

It turns out that there's a Windows service for "OpenSSH Authentication Agent".  I'm not entirely sure what installs that, but apparently it's different from the ssh-agent that's installed with the Windows Git package and the ssh-add command from that doesn't seem to talk to it properly.

My solution was to just disable that service and use the plain-old ssh-agent that comes with Git.  The only problem with that is that the traditional invocation of eval `ssh-agent` doesn't work in Powershell because it outputs a BASH-formatted script.  But that's easily fixed with a couple of regular expressions.  So I added this to my Powershell $profile:

Set-Alias ssh-agent "$env:ProgramFiles\git\usr\bin\ssh-agent.exe"
Set-Alias ssh-add "$env:ProgramFiles\git\usr\bin\ssh-add.exe"

# Need to turn off Open SSH Authentication Agent system service,
# then run the ssh-agent from Git.
function Start-SshAgent {
    $output = (ssh-agent)
    $sock_match = ($output | Select-String -Pattern 'SSH_AUTH_SOCK=(\S+);')
    $sock_path = $sock_match[0].Matches.Groups[1].Value
    $pid_match = ($output | Select-String -Pattern 'SSH_AGENT_PID=(\d+);')
    $agent_pid = $pid_match[0].Matches.Groups[1].Value
    $env:SSH_AUTH_SOCK = $sock_path
    $env:SSH_AGENT_PID = $agent_pid
    Write-Output "Agent pid $agent_pid"


And there we go!  Now I can just run ssh-add to add my key and Git picks it up as expected.

Minor WSL GUI annoyance

Minor annoyance: For some reason, WSL GUI windows like to hide themselves.  I'm not sure why.

I see this all the time on my Windows 10 work laptop, where I use WSL extensively.  It usually happens after my laptop has gone to sleep.  I come back in the morning, log in, and all of my open WSL gVim windows are just gone.  The processes are still running, they're just not displayed and they're MIA from the Windows taskbar.

Fortunately, this is easily fixed by just starting a new WSL GUI app.  So I generally just pop up my Windows Terminal and start a new gVim instance, and then the running instances pop back into existence and they're fine until the system sleeps again.

I have no idea why that happens, nor if it's specific to Windows 10 or anything else.  It's just one of those things that's annoying but not a big deal.  Rant over.

Sometimes WSL needs an update, apparently

Note to self: Sometimes, it seems that WSL needs to be updated.  I mean, yes, obviously it does.  But apparently sometimes Windows updates will break it and you need to manually intervene.

I saw this the other day.  At some point, something got updated and when I tried to open a new WSL terminal, it would always fail with the message Error code: Wsl/Service/0x80040326.  Oddly enough, the WSL shells and processes I already had running still worked, I just couldn't start any new ones.

Luckily, the fix is pretty simple.  You just have to open up a Powershell instance run wsl --update to update WSL and then wsl --shutdown to reboot it.  That's it.  It's just annoying because that's a manual process - you still need to manually run the update, even if you reboot your computer.

The joy of WSL and desktop Linux

I had a workflow revelation on my work machine the other week: Corporate IT pushed a Windows 10 update that brought me up to a version that actually supports running Linux GUI apps under WSL!

I've WSL GUI apps on my home Win11 system for a while, but having that on my work machine is huge.  I use WSL extensively there.  See, we've been standardizing our dev environment setup using Lando, which is basically a convenience layer on top of docker-compose.  It's a handy tool, but the relevant thing to note here is that it works by directly mounting your project code directory inside the Docker container.  This is convenient for Mac and Linux users, but is kind of a problem for Windows users.

As you may (or may not) know, WSL2 is great and out-performs WSL1 in every way except one: cross-filesystem performance.  As long as you keep everything inside the WSL filesystem, you're golden and everything is fast.  But as soon as you try to cross from the Windows filesystem to the Linux one, or vice versa, performance just falls off a cliff.  Sure, it's not a big deal if you just want to edit a file or something like that, but anything that does any remotely significant amount of filesystem access (e.g. running an npm install) is just painful.  In my experience, it's not unheard of for the performance penalty to be on the order of 10x. 

Clearly that's not something you want to endure as part of your normal workflow.  The simple fix is to do all your work inside WSL, which for me means installing Lando in WSL and hosting my code inside WSL.  The only problem is managing the code.  If you want to do that in Windows, you need to do it over a network share, which works, but isn't exactly a great experience.  It also causes various permissions and file ownership issues for apps like Git that actually care about that.

That's where the WSL GUI apps come in.  Rather than dealing with the network share hassle, you can just install your favorite GUI tools inside WSL and run them just like you're on native Linux.  Problem solved!

Well, mostly solved.  Sadly, not everything runs on Linux.  In particular, there's no Linux port of SourceTree, which is currently my graphical Git client of choice.  But it's not that I particularly like SourceTree - it's just that I hate it less than all the other Git clients I've tried.  So I was forced to try some other options.

This part did not go well.  I tried a few different options, including GitFiend (which was nice, but would randomly crash under WSL) and Git-Cola, which was also decent, but which I had to drop because if left alone it would occasionally lock up and then somehow take down the entire system if I tried to close it.  I have no idea how it managed to do that (presumably some bug in WSL's GUI layer), but that's a different problem.  I also attempted to try Gittyup, but I couldn't, because it only offered Flatpak packages.  And, of course, the Flatpak daemon (or whatever it's called) won't install on WSL because it's missing some of the system-level stuff that it uses.  But that's a different post.

Eventually, I declared GUI bankruptcy and decided to actually learn how to use Fugitive, the Git plugin for Vim.  Turns out that Fugitive is actually pretty good and figuring it out was easier than finding a good graphical Git client.  But that's also a story for another post.

In any event, having WSL GUI apps is pretty nice.  Now I can do all my work in WSL, and still have both GVim and PHPStorm, if I need it, without having to pay the cross-OS performance price.  So I can have nice things and good performance.  Yay!

Installing PHPStorm under WSL2

The other week I tried to install PHPStorm under WSL2.  Because that's a thing you can do now (especially since Linux GUI apps now work in recent Windows 10 updates).  The installation process itself was pretty simple.

  • Download PHPStorm for Linux from JetBrains website.
  • Now extract the tarball and run the bin/ script.
  • PHPStorm should start up.

The next step is to configure your license.  In my case, I was using a corporate license server.  The issue with this is that you need to log into JetBrains' website using a special link to activate the license.  Unfortunately:

  • By default, WSL doesn't have a browser installed.
  • Firefox can't be installed because the default build uses a snap image, and WSL apparently doesn't support snap.
  • PHPStorm doesn't appear to be able to properly deal with activating via a Windows browser (I tried pointing it to the Windows Chrome executable and got an error page that points to a port on localhost).

So how do we get around this?  Well, we need to install a browser in WSL and configure PHPStorm to use it.  So here's what we do:

  • Skip the registration for now by starting a trial license.
  • Download the Vivaldi for Linux DEB package from Vivaldi's website.  You could use a different browser, but I like Vivaldi and it offers a convenient DEB package, so I used that.
  • Install the Vivaldi DEB.  WSL will be missing some packages, so you have to run apt install --fix-broken after installing it.
  • Go into the PHPStorm settings and configure your web browsers to include Vivaldi and set it as the default browser.
  • Go back to the registration dialog and try again.  This time, PHPStorm should start up Vivaldi and direct you to the appropriate link.
  • Log into your JetBrains account and follow the instructions.  The web-based portion should succeed and registration should complete when you click "activate" in PHPStorm again.

There we go - PHPStorm is registered and works.  Mildly annoying setup, but not actually that bad.