[Bug 2029268] Re: Do not consider two versions with differing SHA256 to be the same

[Julian Andres Klode]

This has landed in 2.7.3 which will sync in the next day or so.

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https://bugs.launchpad.net/bugs/2029268

Title:
  Do not consider two versions with differing SHA256 to be the same

Status in apt package in Ubuntu:
  Fix Committed
Status in apt source package in Jammy:
  Triaged
Status in apt source package in Lunar:
  Triaged
Status in apt source package in Mantic:
  Fix Committed

Bug description:
  [Impact]
  APT sometimes deduplicates two debs into the same version object even if they have different SHA256 field values, causing download to fail later if one the sources also defines SHA512 (or MD5 or SHA1).

  This is a problem for example, if you rebuild in a PPA because PPAs do
  not have SHA512 enabled but the priamary archive does.

  Repositories are not required to have SHA256, so this does nothing if
  we do not have SHA256 for both .deb.

  [Test plan]
  An automated test is included in apt's extensive autopkgtest regression test suite. Successful pass of autopkgtest is the goal.

  [Where problems could occur]
  In terms of regressions it seems unlikely, because we compare the SHA256 only if we previously would have considered them the same version to reject them if they differ.

  But of course there could be the usual unsafe memory bugs.

  In a future this will bite us when we migrated to SHA3 and want to
  drop SHA256, just like we cannot seem to drop MD5 now.

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