The use of AllowedAPKSigningKeys afaik is to compare that key with the key used for signing the dev build. If its not the same, the dev build is rejected.
From what I've understood from this POC, its possible to bypass this signature check. The only exploit I can think of with this bypass is that someone who gets access to the developer's release channel can host their own signed apk, which will either get rejected by Android in case of update (signature mismatch) or gets installed in case of first install. But in either case, its still the same reproducible build, only the signature is different.
That still enables a supply chain attack, which should not be dismissed - virtually all modern targeted attacks involve some complex chain of exploits; a sufficiently motivated attacker will use this.
>But in either case, its still the same reproducible build, only the signature is different.
That means the attacker still has to compromise the source repo. If they don't and try to upload a backdoored apk, that would cause a mismatch with the reproducible build and be rejected. If you can compromise the source repo, you're already screwed regardless. Apk signature checks can't protect you against that.
Which post are you talking about? >>42592150 was made by FuturisticGoo, not me.
Also, the wording on f-droid suggests the version that f-droid hosts is built by them, rather than a version that's uploaded by the dev. If you go on any app and check the download section, it says
> It is built by F-Droid and guaranteed to correspond to this source tarball.
It also allows the user to place a little less trust on F-Droid because the developer, as well as F-Droid, must confirm any release before it can be distributed. (Now that I think of it, that probably creates an issue where if malware somehow slips in, F-Droid has no power to remove it via an automatic update. Perhaps they should have a malware response or notification system?)
More: https://f-droid.org/2023/09/03/reproducible-builds-signing-k...