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Exposure of trigger tokens on project exports

HackerOne report #497144 by mishre on 2019-02-16, assigned to asaba:

Summary:
Any user can configure a trigger token for himself so that pipelines will be used to create CI/CD jobs on his own user context. When using the trigger token, Jobs created on the user's behalf will have access to all the resources(repositories) the user have (as explained here: https://docs.gitlab.com/ee/ci/triggers/#taking-ownership-of-a-trigger). Maintainers of the repository cannot usually see the trigger tokens for other users (only for themselves) as it will give them complete access (via ci-cd jobs) to perform actions on their behalf.

Description:
All maintainers can perform an export of the repository, which in turn will leak all the trigger tokens created for all the other maintainers of the repository through a file called project.json which contains different information for later restoring the project.

Steps To Reproduce:

  1. Create a new repository.
  2. Go to the Members section of the repository and add another maintainer (the attacker).
  3. Go to the CI/CD settings of the project and create a trigger token.
  4. Login as the attacker and go to the CI/CD settings of the project - you should not be able to see the trigger token.
  5. Now create an export of the project.
  6. Download the exported .tar.gz file and open a file called project.json
  7. Look for the word "trigger" in the json file -> you now should be able to see the token at plaintext and use it to impersonate the victim.

Supporting Material/References:

  • List any additional material (e.g. screenshots, logs, etc.)

Impact

An attacker can impersonate the victim and have access to all the repositories the victims has access to.

Documentation

  • Update the user docs to explicitly call out the fact that trigger tokens are not exported for security reasons.

Implementation plan

Edited by Alan (Maciej) Paruszewski