[Bug 1157943] Re: apt-get update fails hash checks on https repositories when file size changes

[Thomas Bushnell, BSG]

David, #6 means that servers SHOULD send a 416. But apt should support
both, because it cannot rely on servers sending a 416.

#7, you have misunderstood. Yes, there is newer contents, and the server
returns the current complete contents of the file in this case, and apt
is *not replacing the file correctly*.

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https://bugs.launchpad.net/bugs/1157943

Title:
  apt-get update fails hash checks on https repositories when file size
  changes

Status in “apt” package in Ubuntu:
  New
Status in “apt” source package in Precise:
  New

Bug description:
  apt uses its own strategy for sending Range: requests on https,
  instead of the libcurl handling. Here's is a scenario where it gets it
  wrong:

  1) apt downloads the file but doesn't put the file in place yet (perhaps it got interrupted or something)
  2) the file on the server gets replaced by a smaller file
  3) the next update run wants to download the file, sees a partial read, and asks for Range: (len(file)-1)-
  4) the server sees a Range: request for a byte-range past the end of (the current version of) the file, considers it invalid, and streams the entire file. (This is correct behavior.)
  5) apt assumes the response is the range it expected, and appends it to the local staging copy (minus one byte).

  Instead of rolling apt's own attempt to handle ranges in the https
  method, it should just use libcurl's. Attached is a patch which solves
  the problem.

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