Re: Git private branch Feature Suggestion
On 2025-09-10 at 23:28:54, ynckz wrote:
Show 11 quoted lines
> Hi Git developers,
>
> I have a request for you. Could you please add private branches? This
> is a really useful thing.
> Imagine that you want to publish your project as open source, but you
> need to hide the .env file in a separate repository. It's easier to do
> everything in one repository, but in a different branch. Maybe there
> is another way, and I'm just dumb as fuck, but here's another example:
> Say you don't want to release a new feature yet. To do so, create a
> private branch, make the feature there, then merge it into the main
> branch.
The reason we haven't added this is that it isn't secure. Git has a feature called namespaces, which basically implements the feature you want. There are different namespaces and references can be stored in any one of them.
Here's what the gitnamespaces(5) manual page says about this:
The fetch and push protocols are not designed to prevent one side
from stealing data from the other repository that was not intended
to be shared. If you have private data that you need to protect from
a malicious peer, your best option is to store it in another
repository. This applies to both clients and servers. In particular,
namespaces on a server are not effective for read access control;
you should only grant read access to a namespace to clients that you
would trust with read access to the entire repository.It then goes on to explain the kinds of approaches that can be used to exploit this, but basically, if an attacker can find an object ID that it thinks the server has, it can acquire information about that object.
Now, you might say, well, the object ID is private. But it's very common to leak those in issues, build logs, or as part of a version identified in a build, so in general we can't base security on that. Cryptography tells us that cryptographic hashes of general data are not secrets, so we cannot rely on them for access control.
It could be possible to allow this _if_ Git had some way to know that the client was only allowed to access certain refs _and_ Git were configured to only allow access to objects that were reachable from those refs. However, Git doesn't have that information and that's in general expensive to determine, so it would make things like partial clone perform really terribly. It would also require a lot of changes to Git's internals and security model, and nobody has so far volunteered to do that.
I will note that in general, secrets should never be checked into a repository. It's too easy to accidentally expose a repository, and when that happens, you leak every secret in the entire history, and then rotating them all is a colossal hassle. (I know, I've had to do it.) If you use a secret store, which is a security best practice, then this doesn't happen.
--
brian m. carlson (they/them)
Toronto, Ontario, CA
