[Bug 915246] [NEW] update-manager could detect transparent proxy to avoid "Hash Sum mismatch" errors

[James Hunt]

Public bug reported:

If you are behind a transparent proxy (such as squid) or using a local
caching proxy such as apt-cacher-ng, you can end up with errors
resulting from the proxy caching an old version of particular packages,
or not honouring certain HTTP headers.

Errors such as this can occur when attempting to upgrade your system:

  W: Failed to fetch http://gb.archive.ubuntu.com/...some-pkg.i386.deb
Hash Sum mismatch

We could consider enhancing update-manager et al to detect this scenario
and warn the user that the update/upgrade *may* be problematic as a
result of the proxy. Techniques to use include:

- Attempting a "GET /"  on port 80 of an IP address on which it is guaranteed there is no web server listening.
  We could then check the response to look for common proxy info.

- Creating a CGI script on an ubuntu.com server which is guaranteed to return a small file with different content every time.
  Assuming the ubuntu.com web server is configured correctly, if calling this CGI script returns the same value twice,
  the result must be being cached by a proxy.

- Attempt to retrieve the HTTP headers for any valid package file in the archive.
  If the response comes back and includes a "Via:" header, a proxy is in use.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: update-manager 1:0.152.25.5
ProcVersionSignature: Ubuntu 3.0.0-14.23-generic-pae 3.0.9
Uname: Linux 3.0.0-14-generic-pae i686
NonfreeKernelModules: nvidia
ApportVersion: 1.23-0ubuntu4
Architecture: i386
Date: Thu Jan 12 09:59:41 2012
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
PackageArchitecture: all
ProcEnviron:
 PATH=(custom, user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
UpgradeStatus: Upgraded to precise on 2012-01-12 (0 days ago)

** Affects: update-manager (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: apport-bug i386 precise running-unity

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https://bugs.launchpad.net/bugs/915246

Title:
  update-manager could detect transparent proxy to avoid "Hash Sum
  mismatch" errors

Status in “update-manager” package in Ubuntu:
  New

Bug description:
  If you are behind a transparent proxy (such as squid) or using a local
  caching proxy such as apt-cacher-ng, you can end up with errors
  resulting from the proxy caching an old version of particular
  packages, or not honouring certain HTTP headers.

  Errors such as this can occur when attempting to upgrade your system:

    W: Failed to fetch http://gb.archive.ubuntu.com/...some-pkg.i386.deb
  Hash Sum mismatch

  We could consider enhancing update-manager et al to detect this
  scenario and warn the user that the update/upgrade *may* be
  problematic as a result of the proxy. Techniques to use include:

  - Attempting a "GET /"  on port 80 of an IP address on which it is guaranteed there is no web server listening.
    We could then check the response to look for common proxy info.

  - Creating a CGI script on an ubuntu.com server which is guaranteed to return a small file with different content every time.
    Assuming the ubuntu.com web server is configured correctly, if calling this CGI script returns the same value twice,
    the result must be being cached by a proxy.

  - Attempt to retrieve the HTTP headers for any valid package file in the archive.
    If the response comes back and includes a "Via:" header, a proxy is in use.

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: update-manager 1:0.152.25.5
  ProcVersionSignature: Ubuntu 3.0.0-14.23-generic-pae 3.0.9
  Uname: Linux 3.0.0-14-generic-pae i686
  NonfreeKernelModules: nvidia
  ApportVersion: 1.23-0ubuntu4
  Architecture: i386
  Date: Thu Jan 12 09:59:41 2012
  InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
  PackageArchitecture: all
  ProcEnviron:
   PATH=(custom, user)
   LANG=en_GB.UTF-8
   SHELL=/bin/bash
  SourcePackage: update-manager
  UpgradeStatus: Upgraded to precise on 2012-01-12 (0 days ago)

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