Environment substitution replaces env vars in the topology file that are not set

[lostdave]

Steps to reproduce:
Created a topology that included some Junos vSwitch images -> Added a block config in the topology file -> the resultant encrypted password (if if contained . or / characters) would truncate.

startup-config: |
  system {
    login {
      user someuser {
        class super-user;
        authentication {
          encrypted-password "$6$8gNjhXy6$Vj69F.QdM.Nvz1fDDYhnwb27cMSXJmXxS23ti50z/liD3obqPRYs5UKHVbKFRtqZO.AoXJIVR6Um17RFfSwWm1"
        }
      }
    }
  }

What winds up happening is the encrypted password appears as ".QdM.Nvz1fDDYhnwb27cMSXJmXxS23ti50z/liD3obqPRYs5UKHVbKFRtqZO.AoXJIVR6Um17RFfSwWm1"

ContainerLab Version 0.56.0

[hellt]

Hi @lostdave
containerlab/vrnetlab do not modify the contents of the provided startup config.

The way it works with junos is an disk with the startup-config is mounted to the VM, and junos should read the config from it

https://github.com/hellt/vrnetlab/blob/master/vjunosswitch/docker/make-config.sh

I suppose you should check the contents of that disk to verify that the encrypted string is there as it was in the yaml file

[hellt]

buuuut, I think what could have happened is that containerlab tried to expand variables :D $6, etc

Would you mind to try using the startup-config with a file, and not as embedded multiline string to confirm this theory?

[lostdave]

Sorry ....slow to get back to this one..travel and training stuff....
i will have a look in the next couple of weeks and see what is going on

[hellt]

Yes, the issue stems from the fact that the https://github.com/a8m/envsubst package that we use to replace env vards in the topology file replaces the env vars that are not set or empty.

This leads to $foo to be replaced with "" if the $foo is not even set.

Unfortunately, the original package maintainer stopped maintaining the package and this particular feature request left dangling - a8m/envsubst#56

I made a fork of a fork by @dnitsch that added some parts of this functionality, but it doesn't work when the env var is set with the default in the template. To demonstrate this use case I added a test case that currently fails:

https://github.com/hellt/envsubst/blob/50934c197f4028463435a6aa0e8556ca60b442e5/parse/parse_test.go#L179

Looking for brave contributors to see if they can crack it