[Bug 756317] Re: apt broken if cache files are invalid

[Paul F]

Still present in 12.04 LTS, Precise running apt 0.8.16

In my case the corrupted package list files in /var/lib/apt/lists are
caused by the router redirecting to an internal help page when it
realises that its internet connection is down. So, when a fetch is
attempted from, say gb.archive.ubuntu.com/ubuntu/dists/precise-
updates/universe/binary-i386/Packages when checking for updates what
comes back is the html source from the router's help page (example
attached -- line 52 contains the requested url).

It would appear that no sanity check is done on the returned data
leaving subsequent parse attempts to choke. The corrupted files remain
and may propagate (???) causing other update failures.

On a security note, it occurs to me that an attacker in control of the
router could return crafted files in place of apt's package lists to
introduce malware as part of the normal automated update process. I
trust checks are in place to prevent this???

** Attachment added: "Example corrupted package list file from /var/lib/apt/lists"
   https://bugs.launchpad.net/ubuntu/+source/apt/+bug/756317/+attachment/3341764/+files/gb.archive.ubuntu.com_ubuntu_dists_precise-updates_universe_binary-i386_Packages.IndexDiff

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https://bugs.launchpad.net/bugs/756317

Title:
  apt broken if cache files are invalid

Status in “apt” package in Ubuntu:
  Confirmed

Bug description:
  I have an adsl modem which returns an html page if the adsl link is
  broken. This page ends as the content of the apt cache files stored in
  /var/lib/apt/lists, which breaks apt.

  The only way to make apt work again is to delete all the files stored
  in /var/lib/apt/lists.

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