[Bug 1206824] Re: bogus network proxies might cause: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)

[David Kalnischkies]

So, what do you suggest? The hint "does the network require
authentication?" is already a wild guess as this can happen for
temporary down servers (e.g. "Down for maintenance"), 'longtime down'
servers (e.g. domain grabber got the domain), the network you are on
requires you to authenticate (first time, again, after X minutes, for
specific domains), the network has a pre-processing proxy to reduce
traffic/enforce restrictions/parental control, the archive software
really produced invalid files or you are under attack …

The sentence is easily 400 characters long and hasn't mentioned a single
"solution" yet even though for all different things need (not) to be
done.

If anyone can provide a better hint than the current which will fit on
one line feel free tell us, but I don't expect that we can do anything
reasonable to detect which one of the various possible problems that
could be.

(It might first sound like we could detect "normal" vs. "restricted"
archives as it seems to happen here, but APT really has no idea what the
difference is, further more these could be on different mirrors, used
via a proxy… so while this is "easy" (really?) to detect for a human,
its close to impossible in code)

I have some hope for "511 Network Authentication Required" (
https://tools.ietf.org/html/rfc6585#section-6 ), but I haven't seen it
implemented so far [APT has no specific support for it so far, but works
as intended by default as any client should do].

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https://bugs.launchpad.net/bugs/1206824

Title:
  bogus network proxies might cause: Clearsigned file isn't valid, got
  'NODATA' (does the network require authentication?)

Status in “apt” package in Ubuntu:
  Triaged

Bug description:
  On a hotel network I  get:

  sudo apt-get update
  0% [Connecting to archive.ubuntu.com] [Connecting to ports.ubuntu.com] [Connecting to ppa.launchpad.net] [Connecting to archive.canonical.com]
  0% [Connecting to archive.ubuntu.com] [Connecting to ports.ubuntu.com] [Connecting to ppa.launchpad.net] [Connecting to archive.canonical.com]
  Get:1 http://archive.canonical.com saucy InRelease [75 B]                                                   
  89% [1 InRelease gpgv 75 B] [Connecting to archive.ubuntu.com (91.189.91.14)] [Waiting for headers] [Waiting for headers]Splitting up /var/lib/apt/lists/partial/arIgn http://archive.canonical.com saucy InRelease    
  E: GPG error: http://archive.canonical.com saucy InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)

  
  and after removing all /var/lib/apt/lists forcefully, I get this variant:

  Get:19 http://ports.ubuntu.com saucy/main armhf Packages [1,215 kB]
  Get:20 http://archive.ubuntu.com saucy-updates Release [40.8 kB]
  Get:21 http://archive.ubuntu.com saucy-security Release [40.8 kB]
  Get:22 http://archive.ubuntu.com saucy/main Sources [1,004 kB]
  Ign http://ppa.launchpad.net saucy/main Translation-en_US
  Ign http://ppa.launchpad.net saucy/main Translation-en
  Ign http://ppa.launchpad.net saucy/main Translation-en_US
  Ign http://ppa.launchpad.net saucy/main Translation-en
  Get:23 http://archive.canonical.com saucy InRelease [75 B]
  66% [23 InRelease gpgv 75 B] [22 Sources 646 kB/1,004 kB 64%] [19 Packages 710 kB/1,215 kB 58%]Splitting up /var/lib/apt/lists/partial/archive.canonical.com_ubuntu_dists_saucy_InRelease into data and signIgn http://archive.canonical.com saucy InRelease
  E: GPG error: http://archive.canonical.com saucy InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)

  
  Would be good to give better error messages that explain to folks that its likely that your network serves corrupted files (rather than ubuntu being broken). Might want to give folks hints that they could try to connect to a different wifi network etc.

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