Kaniko fails to authenticate to gitlab.com registry

Hi there.

I’m currently having trouble using kaniko to push my docker image to this project’s docker registry.

As you can see on this merge request, I’ve been trying to introduce a “publish” step in my CI that reproduces almost exactly the doc for using kaniko with gitlab-CI, the only difference is that I’m fetching my binary as an artifact from a previous step, and that my dockerfile is located at $CI_PROJECT_DIR/docker/Dockerfile :

publish:
  stage: publish
  needs:
    - job: build
      artifacts: true
  image:
    name: gcr.io/kaniko-project/executor:debug
    entrypoint: [""]
  script:
    - mkdir -p /kaniko/.docker
    - echo "{\"auths\":{\"$CI_REGISTRY\":{\"username\":\"$CI_REGISTRY_USER\",\"password\":\"$CI_REGISTRY_PASSWORD\"}}}" > /kaniko/.docker/config.json
    - /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/docker/Dockerfile --destination $CI_REGISTRY_IMAGE:$CI_COMMIT_SHORT_SHA

Whatever I try to do, I’m always getting an authentication error:

error checking push permissions -- make sure you entered the correct tag name, 
and that you are authenticated correctly, and try again: 
checking push permission for "registry.gitlab.com/neuware/xkcd-bot:f4137e95": 
POST https://registry.gitlab.com/v2/neuware/xkcd-bot/blobs/uploads/: 
UNAUTHORIZED: authentication required; 
[map[Action:pull Class: Name:neuware/xkcd-bot Type:repository] map[Action:push Class: Name:neuware/xkcd-bot Type:repository]]

Is there something broken with the current kaniko release, or the doc, or gitlab’s registry, or am I missing something obvious?

I tried multiple things to reproduce this issue, including building and pushing the same image, using the same version of kaniko executor on my laptop, and I didn’t get any error.

I tried replacing the docker configuration (/kaniko/.docker/config.json) with the auth information I’m using on my laptop : it just won’t work in the CI. I’m always getting this “unauthorized” error message no matter what.