commit eac08feb1fffd0b9faa2b1862985b09386789536
author Elly <ellyjones@chromium.org> Tue Oct 29 17:21:17 2024
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Tue Oct 29 17:21:17 2024
tree 3b2ce55cf20bb0099f00917ba2e2b6448159cdb2
parent ab3b514d58d77c18d50d893c66a201cc48146abf

onc: remove unused passphrase support

ONC configs can be encrypted with a passphrase, which is used to derive
a key with a specified key derivation function (which ONC calls a
"stretch").  Our low-level code for dealing with ONC configs supports
decrypting ONC configs with arbitrary passphrases, and we have tests
that exercise this behavior, but none of the production code paths into
this decryption function can ever actually supply a non-empty
passphrase. The result of that is that we cannot decrypt ONC configs in
production unless they use an empty passphrase anyway, at which point
the key is solely derived from the salt - included in the ONC config
itself, so providing no incremental security. As far as I can tell,
non-empty passphrases for decrypting ONC configs were never supported.

This change removes the passphrase parameter from the low-level ONC
decryption code and removes the test coverage for nonempty passphrases;
the decryption code is now hardcoded to use an empty passphrase for key
derivation. This simplifies reasoning about the security guarantees
provided a bit and will also make an upcoming refactor to use the new
crypto::kdf and crypto::aes_cbc APIs a bit more straightforward.

See the ONC spec for more details: //components/onc/docs/onc_spec.md

Fixed: 375231017
Change-Id: Ibc945d18aba6c4ab3518f00104e0dc2b63134318
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5958357
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Igor <igorcov@chromium.org>
Commit-Queue: Elly FJ <ellyjones@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Nikhil Nayunigari <nikhilcn@google.com>
Cr-Commit-Position: refs/heads/main@{#1375342}