Debian jessie GPG error Clearsigned file isn't valid

Question

This is what I get when running apt-get update:

/root$ sudo apt-get update
Get:1 http://security.debian.org jessie/updates InRelease [1,507 B]
Get:2 http://cdn.debian.net jessie InRelease [1,507 B]
Get:3 http://cdn.debian.net jessie-updates InRelease [1,507 B]
Err http://security.debian.org jessie/updates InReleaset/lists/partial/security.debian.org_dists_jessie_updates_InRelease into data and signature failed

Err http://cdn.debian.net jessie InReleasep /var/lib/apt/lists/partial/cdn.debian.net_debian_dists_jessie_InRelease into data and signature failed

Err http://cdn.debian.net jessie-updates InReleaseib/apt/lists/partial/cdn.debian.net_debian_dists_jessie-updates_InRelease into data and signature failed

Fetched 4,521 B in 1s (4,271 B/s)
Reading package lists... Done
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://security.debian.org jessie/updates InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://cdn.debian.net jessie InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://cdn.debian.net jessie-updates InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)

W: Failed to fetch http://cdn.debian.net/debian/dists/jessie/InRelease

W: Failed to fetch http://security.debian.org/dists/jessie/updates/InRelease

W: Failed to fetch http://cdn.debian.net/debian/dists/jessie-updates/InRelease

W: Some index files failed to download. They have been ignored, or old ones used instead.

I was reading about this, but I'm still a little confused with how GPG keys work with repos.

Each repository has a key associated with it that I need to have trusted on my machine before updates from that repo will be allowed right? So if this error is caused by having an out of date key how do I import the new key?

Edit: I'm also curious why it says "Clearsigned file isn't valid". I thought Clearsign was only for wrapping text docs not tar balls- unless I read this wrong.

Solution

I wasn't sure whether or not I should just delete this question because it turned out to be the very common proxy problem.

I was convinced this wasn't it but doing a wget -O- http://cdn.debian.net/debian/dists/jessie/InRelease as suggested returned a response from our proxy. I didn't think I was pointing to our proxy but i was!

Comments

[Ferenc Wágner]

Please provide the full output of the command wget -O- http://cdn.debian.net/debian/dists/jessie/InRelease and the contents of the file /var/lib/apt/lists/cdn.debian.net_debian_dists_jessie_InRele‌​ase. This may be the symptom of a faulty transparent proxy, as explained at askubuntu.com/questions/474549/….