Ubuntu downloads are insecure

[Matthew Paul Thomas]

1. Starting at the ubuntu.com front page, download a copy of Ubuntu.

What happens:
A. <http://www.ubuntu.com/> is served over HTTP.
B. <http://www.ubuntu.com/download> is served over HTTP.
C. <http://www.ubuntu.com/download/desktop> is served over HTTP.
D. <http://www.ubuntu.com/download/desktop/contribute/?version=14.04.2&architecture=amd64> is served over HTTP.
E. <http://www.ubuntu.com/download/desktop/thank-you?country=GB&version=14.04.2&architecture=amd64> is served over HTTP.
F. <http://releases.ubuntu.com/14.04.2/ubuntu-14.04.2-desktop-amd64.iso> is served over HTTP.

An attacker could perform a MITM attack at any of these stages to give you an ISO that seems to be the real Ubuntu, but is actually malware.

What should happen: The image, and all the ubuntu.com pages leading to it, are served over HTTPS.

This might be dependent on moving www.ubuntu.com to HTTPS generally (see also bug 1385886), but switching releases.ubuntu.com to HTTPS is also necessary and could be worked on in parallel.

[Peter Mahnke (peterm-ubuntu)]

I have passed this to IS

[Matthew Paul Thomas (mpt)]

Setting to public, as there are no confidential details here and the issue has been raised on ubuntu-devel-discuss@. <https://lists.ubuntu.com/archives/ubuntu-devel-discuss/2015-September/thread.html#15819>

[Dimitri John Ledkov (xnox)]

After downloading the image F, one should proceed to verify its authenticity.

1) download checksums
2) download GPG signatures on those checksums
3) verify GPG signature
4) compare checksums of the image downloaded with the signed ones

All of the above mentioned things are available from http://releases.ubuntu.com/

e.g. For trusty
http://releases.ubuntu.com/trusty/SHA256SUMS
http://releases.ubuntu.com/trusty/SHA256SUMS.gpg

And the keys used to sign these, are in the global strongly connected GnuPG web of trust set. And one can establish a trust path to said key, via real humans. (Most ubuntu and debian developers).

However, I do take that this is slightly obscure. However, we will not rely on TLS (SSL) as that opens us up to all the TLS/SSL server and client side vulnerabilities as well as rogue CA, whilst limiting our ability to utilise CDN, mirror network and country specific mirrors.

An easier way to grab and validate checksums and GPG signatures would be nice. Imho web browsers should be able to find and validate those.