As readers of this blog or the mailing lists are likely already
package security is important to both FP Complete and other
members of the Commercial Haskell community. While there was quite
a bit of public discussion around this during the planning phase, I
was reminded in a conversation on Friday that we never announced
the outcome of these plans.
tl;dr: Secure package distribution is fully implemented in
with some options to harden the default. We're still implementing
an easy author signing story, and that will be announced soon.
The implementation we have in stack follows the plan in the
above-linked proposal pretty directly. Let me just flesh it out
- The all-cabal-hashes
repository is used by default by stack for getting the collection
of cabal files (known as the package index). This is downloaded
https. In addition to the raw .cabal files, this
repository also contains hashes and download sizes for all tarballs
- When downloading tarballs, the file size and content hash will
be verified against the information provided in the index, if
available. If more bytes are provided than indicated, the download
is aborted. Only after verification is complete is the file moved
into its final destination and available for future
- For added security (which I'd recommend), you can also turn on
GPG verification and requiring hashes for this index (see
the stack.yaml configuration settings).
- GPG verification will use Git's built-in GPG support to verify
the signature on the all-cabal-hashes tag before accepting the new
content, and will refuse to update the index if the GPG
verification fails. (You'll need to
add our GPG key to your keychain.)
- Requiring hashes means that the package index will not be
accepted unless every package listed also has package hash/download
size information. This is disabled by default for those who
download the package index without Git support.
The story still isn't complete: we have no way to verify that
the package author really is the person who uploaded the package.
Stay tuned to the upload/signature author work we're doing, which
will hopefully be available Real Soon Now(tm).
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