subkey binding signature with no usage flags and/or a critical notation
wk at gnupg.org
Sat Sep 14 10:51:02 CEST 2013
On Wed, 11 Sep 2013 23:46, dkg at fifthhorseman.net said:
> As i reported earlier, this fix works fine. I've backported it against
> 1.4.14 and it works there too (below). It does not seem to be applied
> to the stable branches (1.4 and 2.0). I think it needs to be applied
> to the stable branches.
It is quite possible that I lost track of it.
> Without this patch, if a subkey with a usage flags subpacket that is
> all-zero appears, GnuPG thinks that the key is valid for all
> capabilities (usage: SCEA).
Yes. It is the key owner's decision.
> * if it's someone else's key, GnuPG may be willing to rely on OpenPGP
> certifications made by the key, despite the owner having clearly
No. Key signatures (certifications) are only allowed by the primary
key. This is an OpenPGP requirement.
> sent a message to an automated service which requires signed mail, and
> the message was rejected because it was made by this subkey).
Old PGP versions (iirc < 6.58) were not abale to handle sugnature
subkeys. Same hoes for old keyservers.
> I'm inclined to see this as a security vulnerability (because of the
> confidentiality and certification-following concerns); i'd like to see
Sorry, I don't understand. Only the owner of the key can create a
subkey. We can't forbid him to shoot in his own foot.
> it fixed in the stable branches and assigned a CVE, so that i can push
> for getting it resolved in those distros that care about CVE coverage.
Die Gedanken sind frei. Ausnahmen regelt ein Bundesgesetz.
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