Diffie-Hellman key exchange has been lowered to 256 bits

[James Cloos <cloos@jhcloos.com>]

I've been getting this message on my deb box for a few days now:

,----
| gnutls.c: [1] Note that the security level of the Diffie-Hellman key
| exchange has been lowered to 256 bits and this may allow decryption of
| the session data
`----

It occurs for both nntp starttls and imaps connectins.

That box runs sid and emacs24-nox, which uses libgnutls-deb0-28
(currently 3.2.15-2).

Using gnutls-cli directly, with either --tofu or --insecure to
connect to news.gmane.org (also with --starttls) results in:

,----
| - Description: (TLS1.0)-(RSA)-(AES-128-CBC)-(SHA1)
| - Session ID: E9:A4:91:94:AF:F0:B0:0E:EB:E1:55:BD:80:8F:A5:63:88:FC:38:96:3F:75:1E:63:2B:18:F4:F1:11:D6:98:E0
| - Version: TLS1.0
| - Key Exchange: RSA
| - Cipher: AES-128-CBC
| - MAC: SHA1
| - Compression: NULL
`----

and no error.

gnutls-cli -p imaps imap.gmail.com also works well, generating:

,----
| - Description: (TLS1.2)-(ECDHE-RSA-SECP256R1)-(AES-128-GCM)
| - Session ID: 5A:B8:70:F0:43:3D:25:EF:9D:F2:2D:9A:73:5C:CB:6E:DE:45:01:0C:71:E3:D6:F6:B3:C0:B9:47:5A:E2:E4:A4
| - Ephemeral EC Diffie-Hellman parameters
|  - Using curve: SECP256R1
|  - Curve size: 256 bits
| - Version: TLS1.2
| - Key Exchange: ECDHE-RSA
| - Server Signature: RSA-SHA256
| - Cipher: AES-128-GCM
| - MAC: AEAD
| - Compression: NULL
`----

So I cannot see why gnus' usage triggers that warning from gnutls.

-JimC
--
-JimC
-- 
James Cloos <cloos@jhcloos.com>         OpenPGP: 0x997A9F17ED7DAEA6