show how to reverse the repository hash

howto/gitlab.md

@@ -527,6 +527,34 @@ $ curl -s 'https://gitlab.torproject.org/api/v4/projects/647' | jq .web_url
 "https://gitlab.torproject.org/tpo/core/arti"
 ```
 
+## Find the project associated with a hashed repository name
+
+Git repositories are not stored under the project name in GitLab
+anymore, but under a hash of the project ID. The easiest way to get to
+the project URL from a hash is [through the rails console](https://docs.gitlab.com/ee/administration/repository_storage_paths.html#from-hashed-path-to-project-name), for
+example:
+
+    sudo gitlab-rails console
+
+then:
+
+    ProjectRepository.find_by(disk_path: '@hashed/b1/7e/b17ef6d19c7a5b1ee83b907c595526dcb1eb06db8227d650d5dda0a9f4ce8cd9').project
+
+The project's full path is also available in the `config` file in the
+git repository, under the `fullpath` config entry.
+
+Finally, you can also generate a rainbow table of all possible hashes
+to get the project ID, and from there, find the project using the API
+above. Here's a Python blob that will generate a hash for every
+project ID up to 2000:
+
+    import hashlib
+
+    for i in range(2000):
+        h = hashlib.sha256()
+        h.update(str(i).encode('ascii'))
+        print(i, h.hexdigest())
+
 ## Connect to the PostgreSQL server
 
 The GitLab Omnibus setup is special: it ships its own embedded