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About Carlo Sciolla

Carlo Sciolla
An enterprise software engineer by day and Clojurian, meetup organizer, blogger and biker by night, Carlo is an Open Source enthusiast and passionate of every thing software. Currently working as Product Lead at Backbase, he is also the organizer of the Amsterdam Clojurians meetup and the yearly October Amsterdam Clojure conference.

Clojure GitLab deps

You need to force  the ssh-rsa host key instead of the default one picked up by the tooling:

$ ssh-keygen -R gitlab.com
$ cat <<EOF >> ~/.ssh/config

Host gitlab.com
  HostKeyAlgorithms ssh-rsa

EOF
$ ssh git@gitlab.com

CSI version of the above

You are using the brand new dependency resolution from the Clojure core team for the first time. So you like the idea of fetching your dependency straight from git. You host all of your repos on GitLab, it just makes sense, right? Right.

You go ahead and start your new project, you just need to bring in the usual me/my-awesome-lib that you use everywhere. That’s just a new, empty folder in which you configure your deps.edn like the following:

{:deps {my-awesome-lib {:git/url "git@gitlab.com:me/my-awesome-lib.git" :sha "031aa264afc2cf6dee9e12de8b88c608faefea80"}}}

No more lein new, no more templates, no more nothing. You mentally pat yourself on the shoulder.

You’re now at the terminal, ready to sprinkle your clojure fairy powder all over. You fire clj -m my-awesome-lib.main and stand in awe as the tool fetches bits from GitLab and…

Cloning: git@gitlab.com:me/my-awesome-lib.git
Error building classpath. git@gitlab.com:me/my-awesome-lib.git: UnknownHostKey: gitlab.com. RSA key fingerprint is b6:03:0e:39:97:9e:d0:e7:24:ce:a3:77:3e:01:42:09
org.eclipse.jgit.api.errors.TransportException: git@gitlab.com:me/my-awesome-lib.git: UnknownHostKey: gitlab.com. RSA key fingerprint is b6:03:0e:39:97:9e:d0:e7:24:ce:a3:77:3e:01:42:09

Damn! Damn. Really? Mhhhhh…

$ ssh git@gitlab.com
PTY allocation request failed on channel 0
Welcome to GitLab, @carlo.sciolla!
Connection to gitlab.com closed.

Seems all good. One final check:

$ grep gitlab ~/.ssh/known_hosts
gitlab.com,35.231.145.151 ecdsa-sha2-nistp256 ****

Things are getting creepy. Worse of it all, you got stuck there. Fortunately, you have a little bird spilling some relevant beans: the specific host key crypto algorithm (ecdsa-sha2-nistp256 in the above) might be relevant! A lead is a lead, and this feels like a good one. Let’s explore.

First things first, you need to start from a clean slate. Let’s remove the currently installed host key:

$ ssh-keygen -R gitlab.com

Good. Now let’s have a look at what keys are provided by GitLab, just to have a feel for what could be a sensible one to pick:

$ ssh -Q key git@gitlab.com
ssh-ed25519
ssh-ed25519-cert-v01@openssh.com
ssh-rsa
ssh-dss
ecdsa-sha2-nistp256
ecdsa-sha2-nistp384
ecdsa-sha2-nistp521
ssh-rsa-cert-v01@openssh.com
ssh-dss-cert-v01@openssh.com
ecdsa-sha2-nistp256-cert-v01@openssh.com
ecdsa-sha2-nistp384-cert-v01@openssh.com
ecdsa-sha2-nistp521-cert-v01@openssh.com

Whoa! That’s quite a rich of a menu to choose from. But your spidey senses are tingling: that ssh-rsa feels good. Warm. Homey. Or maybe it’s just the closest to what the original error message said. Whatever, lets tell SSH to pick that one:

$ cat <<EOF >> ~/.ssh/config

Host gitlab.com
  HostKeyAlgorithms ssh-rsa

EOF

Alright, time to shine.

$ clj -m my-awesome-lib.main
Cloning: git@gitlab.com:me/my-awesome-lib.git
Error building classpath. git@gitlab.com:me/my-awesome-lib.git: UnknownHostKey: gitlab.com. RSA key fingerprint is b6:03:0e:39:97:9e:d0:e7:24:ce:a3:77:3e:01:42:09
org.eclipse.jgit.api.errors.TransportException: git@gitlab.com:me/my-awesome-lib.git: UnknownHostKey: gitlab.com. RSA key fingerprint is b6:03:0e:39:97:9e:d0:e7:24:ce:a3:77:3e:01:42:09

Damn! Really?! “Oh wait!” you think, as you realize that maybe now you need to first get the new host key:

$ ssh git@gitlab.com
The authenticity of host 'gitlab.com (35.231.145.151)' can't be established.
RSA key fingerprint is SHA256:ROQFvPThGrW4RuWLoL9tq9I9zJ42fK4XywyRtbOz/EQ.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'gitlab.com,35.231.145.151' (RSA) to the list of known hosts.
PTY allocation request failed on channel 0
Welcome to GitLab, @carlo.sciolla!
Connection to gitlab.com closed.

Good! Now, what if… you just did it? “Well, here goes nothing.” you think, mindlessly typing that dreaded command one last time:

$ clj -m my-awesome-lib.main
Cloning: git@gitlab.com:me/my-awesome-lib.git
Checking out: git@gitlab.com:me/my-awesome-lib.git at 031aa264afc2cf6dee9e12de8b88c608faefea80
Welcome to MyProject!

Good. That’s good, really. You feel like you deserve a coffee now. And you do.

Published on Java Code Geeks with permission by Carlo Sciolla, partner at our JCG program. See the original article here: Clojure GitLab deps

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