1493936 - Add way to disable DSA signatures through policy

Status: RESOLVED FIXED

(NSS :: Libraries, enhancement)

Description

[Daiki Ueno [:ueno]]

While the use of DSA signatures are prohibited in TLS 1.3, there is no way to turn it off through the current policy mechanism.  It would be nice if there is a new policy keyword for that.

Comment 1

[Darkspirit]

Couldn't you just remove support for "DSA"?

Comment 2

[Daiki Ueno [:ueno]]

Attachment: Bug 1493936, add a new "DSA" policy keyword

This adds a new policy keyword "DSA" to explicitly disable DSA in TLS 1.2 or earlier. 

We could make this a bit more generic, e.g., by adding "ECDSA", "RSA-PSS" etc.   However, considering the current use of policy in [fedora-crypto-policies](https://gitlab.com/redhat-crypto/fedora-crypto-policies), I realized that adding new keywords may cause compatibility problems; because the Fedora configuration has `disallow=ALL`, all new keywords would be disabled by default.   I think it's okay for DSA, though.

Comment 3

[Kai Engert (:KaiE:)]

Comment on attachment 9011797 [details]
Bug 1493936, add a new "DSA" policy keyword

Kai Engert (:kaie:) has approved the revision.

Comment 4

[Kai Engert (:KaiE:)]

Daiki, FYI, there was r+ but no further update.

Comment 5

[Daiki Ueno [:ueno]]

Kai, sorry for not responding earlier; as noted on phabricator, I put this on hold because the patch didn't have sufficient test coverage. In fact, it was revised after we realized that client still sends DSA algorithms in the "signature_algorithms" extension.

Now it has a test for both client and server; could you take a look at it again?

Comment 6

[Daiki Ueno [:ueno]]

Thank you for the review; pushed as:
https://hg.mozilla.org/projects/nss/rev/4bc22e14a592