Based on https://github.com/circleci/encrypted-files

In the CircleCI web UI, we have a secret variable called KEY https://circleci.com/gh/angular/angular/edit#env-vars which is only exposed to non-fork builds (see "Pass secrets to builds from forked pull requests" under https://circleci.com/gh/angular/angular/edit#advanced-settings)

We use this as a symmetric AES encryption key to encrypt tokens like a GitHub token that enables publishing snapshots.

To create the github_token file, we take this approach:

• Find the angular-builds:token in http://valentine
• Go inside the CircleCI default docker image so you use the same version of openssl as we will at runtime: docker run --rm -it circleci/node:10.12
• echo "https://[token]:@github.com" > credentials
• openssl aes-256-cbc -e -in credentials -out .circleci/github_token -k $KEY
• If needed, base64-encode the result so you can copy-paste it out of docker: base64 github_token