CI (Buildkite): for the signed pipeline test, use signature_file instead of signature

[DilumAluthge]

No description provided.

[DilumAluthge]

@staticfloat Any idea what's going wrong here? The signature is exactly the same; I've just moved it from signature to a signature_file.

Running plugin cryptic post-command hook

$ /etc/buildkite-agent/plugins/github-com-staticfloat-cryptic-buildkite-plugin/hooks/post-command

2021-07-26 01:43:51 INFO Reading pipeline config from ".buildkite/pipelines/main/launch_unsigned_builders.yml"

2021-07-26 01:43:51 INFO Updating BUILDKITE_COMMIT to "7136cecec04cc53b6cbd371d4bec51bbfb599a45"

2021-07-26 01:43:52 INFO Successfully uploaded and parsed pipeline config

bad magic number

ERROR: Refusing to continue execution; pipeline '.buildkite/pipelines/main/misc/signed_pipeline_test.yml' fails treehash signature check! You may need to re-run cryptic/bin/sign_treehashes!

🚨 Error: The plugin cryptic post-command hook exited with status 1

[DilumAluthge]

Ah, looks like the signature is Base64-encoded, so I need to Base64-decode it before I write it to the file at signature_file.

Here's the code I used:

import Base64

function base64_decode_signature_file(filename::AbstractString)
    str = read(filename, String)
    b = Base64.base64decode(str)
    rm(filename; force = true)
    open(filename, "w") do io 
        write(io, b)
    end
    return nothing
end

And then you can run it with:

base64_decode_signature_file(".buildkite/pipelines/main/misc/signed_pipeline_test.yml.signature")