stackage-install

stackage-install provides a wrapper around the cabal install command, which will download packages more securely. Initially, this means downloading over an HTTPS connection from FP Complete's Amazon S3 mirror of Hackage, though more hardening is planned for the future (see future improvements below).

To install, simply run cabal update && cabal install stackage-install. Usage is intended to overlap well with cabal install. Whenever you would have run cabal install foo, you can now run stackage-install foo (or stk install foo with stackage-cli installed), which will perform the following steps:

1. Run cabal fetch --dry-run ... to get cabal's build plan
2. Download the relevant packages from S3, and place them in the locations that cabal-install expects
3. Run cabal install ...

Caveats

If you have a modified remote-repo in your ~/.cabal/config file, this tool will not provide proper hardening. Most users do not modify their remote-repo, so this shouldn't be an issue most of the time.

There are some combinations of cabal install arguments which may not translate well to this tool. One known issue is that passing --dry-run is not supported, but others may apply as well.

This tool necessarily has to call cabal-install twice, once to calculate the dependencies, and then to install them. It's theoretically possible that cabal-install could come up with different build plans between the two calls, in which case the second call may download some packages insecurely. I've opened cabal issue #2566 about disabling downloading in cabal.

Why not fix cabal?

Hopefully cabal will get fixed soon, the discussion has already started. It's unfortunately unclear how long that discussion will take, and I received a specific request to write this tool. Since it's a small amount of code, I went ahead with this as an interim solution.

That said, some of the future enhancements discussed below are not planned for cabal, in which case this tool will continue to remain relevant for people looking for additional security beyond transport security.

Why Stackage?

See the same question and its answer on stackage-update.

Future enhancements

• Check hashes of all packages downloaded against a collection of package hashes
• Verify signatures from authors against the signature archive