This is not a -1, but I think it'd be useful to have some perspective
here, rather than just the "no HTTPS the sky is falling" view.

> HTTPS everywhere is now a best practice on the web, and through the US
government and among major service providers.

I don't agree with this as a justification. "HTTPS everywhere" has come
out of a specific need. The justifications for its implementation do not
automatically hold "everywhere", especially outside of web apps. That's
not to say that HTTPS shouldn't be implemented here, just that the
argument that "it has been justified elsewhere, therefore it is
justified here" is not a valid one, especially because in the other
cases no HTTPS means no protection, whereas we already use signed
packages. Thus this particular argument is hardly "compelling". The pros
and cons of HTTPS implementation for package repositories should be
considered on its own merits.

> * network attackers can't see what packages you're downloading and the
specific software versions, thus profiling the server and assisting the
targeting of vulnerabilities and zero-day attacks against it

The published packages have well known sizes, so I think attackers
probably can infer what an individual downloads based on size. That
doesn't mean that we should not have HTTPS, but rather that it should
not be assumed that HTTPS downloads of packages would automatically be
private.

If you really want privacy of the packages you download, it would be
more effective to operate a full local repository mirror.

> * a sophisticated attacker with possession of a compromised package
signing key can't leverage a "QUANTUM insert"-esque technique to
redirect to a malicious .deb

A "a compromised package signing key" sounds like a tall order to me.
Far harder than a compromised mirror private SSL key, since the former
doesn't need to be kept on machines with widespread exposure to the
world. I suppose there's no harm in being protected by both, though,
since the two would probably need to be compromised separately - though
I suspect that so many other attack vectors would be opened up by a
compromised packaging signing key that HTTPS to your mirror probably
won't help you anyway. For example, what about "flashplugin-installer"
(for those who have multiverse enabled) and its download of a binary
blob outside the usual packaging system, only verified by a
(package-)signed hash? If a packaging signing key were compromised,
you'd get little protection from an HTTPS apt repository without this
transfer also being on HTTPS.

> * an attacker able to passively sniff the network traffic would not be
able to use fingerprint techniques to find/identify servers installing
an exact set of packages specific to an environment the adversary is
searching for

Note the fingerprint-by-size issue above - I don't think HTTPS will help
you against sophisticated attackers here. Run a full local repository
mirror instead if you care about this.

> * it makes impersonating an apt repo (for example with the goal of
blocking people from receiving security updates) more difficult

Somewhat true I guess, though note that although I don't see it being
used, apt is capable of some level of protection for this by Release
files having expiry dates. See "Check-Valid-Until" in apt.conf(5) for
details. But impersonators would be able to get away with it for a
while, so an HTTPS mirror would improve this by informing users of the
failure immediately rather than after the expiry time.

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https://bugs.launchpad.net/bugs/1464064

Title:
  Ubuntu apt repos are not available via HTTPS

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