Comment 11 for bug 1553121

On Monday, 2. May 2016, 16:13:37 I wrote:
> As far as I know ~anders-kaseorg should be right in Bug #1556666. The
> keys are statically imported to the trusted-Keychain. The SHA-1 o
> signature isn't used for any verification in any apt mechanisms I know.
> For this reason the warning in the output of apt-get update should be
> more than enough.

On Monday, 2. May 2016, 18:14:00 I wrote:
> | W:
[...]
> | Signature by key 882F7199B20F94BD7E3E690EFADD8D64B1275EA3 uses
> | weak digest algorithm (SHA1)

On Monday, 2. May 2016, 18:14:00 I wrote:
> IMHO for nothing!

Hi all,

another correction to the backgrounds of the SHA-1 stuff. Someting missleads me
the SHA-1 signature on the key to be the security issue.
It's the signature in the Release.gpg / InRelease file that causes the issue.

For more details:
http://www.cs.umd.edu/~jkatz/papers/pgp-attack.pdf

Exchanging the Key would be usefull to make old signatures worthless for
future attacks. But the key itself is not / or at least should not be the
cause of this message. ;-)

That would mean that the lines in gpg.conf should probably fix that, if
exchanging the key is not an option. If you're doing this, you must hope
nobody can find old signatures of your key.

An hash collision atack (the length attack is a special case of this) isn't an
easy attack, but for distributing malware as security update via an
compromised or malvious mirror server this isn't impossible someone does.

For this it's reasonable to warn or disable this by default with an error
message.

Now, from background informations back to the bug...

Of course this does'nt change the following...

On Monday, 2. May 2016, 16:13:37 I wrote:
> In our case netboot install failed with a "no suitable kernel found with
> your apt settings" (message text written down from memory), when our
> internal software repository was included to bootstrap our deployment
> environment.
[...]
> IMHO this should at least be catched with a propper error message.

On Monday, 2. May 2016, 18:14:00 I wrote:
> Or people are simply
> deploying the repository URL via preseed and get weired errors, now.
>
> At least the last case *should* be fixed, since this will burn a lot of
> time.

And I didn't mean my time, I know this Bug, now. ;-) :-D

As mentioned in my previos messages, I tried to find the lines causing this but
without success, or at least without being able to reproduce this with the
eqations of the binarys in an usual xenial installation (the scripts would
IMHO run with the udeb eqations of gpgv and apt-get - I asummed they're
behaving equally but do they?).

This is'nt really easy to trobleshoot because there are mutiple special
packages for installation and bootstraping playing together. ;-)

Kind regards,
 Lars

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