References: <20170701112951.19119-1-steffan@...1856...> From: Steffan Karger Message-ID: <7ca195bc-c088-5ccc-3b2f-07e2dec215ee@...1435...> Date: Mon, 14 Aug 2017 13:17:25 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="kIU114eCDvOl8nWDK1dwu9EtL1HORkGIh" Subject: Re: [Openvpn-devel] [PATCH] Deprecate --keysize List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: openvpn-devel@lists.sourceforge.net --kIU114eCDvOl8nWDK1dwu9EtL1HORkGIh Content-Type: multipart/mixed; boundary="sbLx2pSinfxWixKlxwJ39OMvXm8U8nMUi"; protected-headers="v1" From: Steffan Karger To: openvpn-devel@lists.sourceforge.net Message-ID: <7ca195bc-c088-5ccc-3b2f-07e2dec215ee@...1435...> Subject: Re: [Openvpn-devel] [PATCH] Deprecate --keysize References: <20170701112951.19119-1-steffan@...1856...> In-Reply-To: --sbLx2pSinfxWixKlxwJ39OMvXm8U8nMUi Content-Language: en-US Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Hi, On 14-08-17 12:36, David Sommerseth wrote: > On 01/07/17 13:29, Steffan Karger wrote: >> The --keysize option can only be used with already deprecated ciphers, >> such as CAST5, RC2 or BF. Deviating from the default keysize is >> generally not a good idea (see man page text), and otherwise only >> complicates our code.> >> (If this patch is accepted, I'll send a follow-up patch to remove the >> option from the master branch.) >=20 > I agree to the wanted intention of this change. But, it hits badly if > we remove --keysize on configurations still enforcing BF-CBC with > --keysize 256. I don't have any numbers of how many users uses it; but > I know many have preferred BF-CBC for a long time - at least before > SWEET32 came and hit us all. Bare in mind that BF-CBC was the default > since 2002-ish (probably even longer, if considering the OpenVPN v1.x > branch). And many have added --cipher BF-CBC in their configs despite it > was the default. >=20 > As long as BF-CBC is available, we cannot remove --keysize. And to > remove BF-CBC support, I think that needs a bit longer timespan than > v2.5. Users *must* be far better prepared for that and we need to make > loud and clear announcements with such a change. >=20 > Yes, in all this, I know that NCP is a nice rescue. As long as everyone > either runs v2.4 everywhere or deploys --ncp-ciphers and starts the > migration. But I've lost confidence that the vast majority of our users > pays closely attention to such feature changes - thus they won't notice > until it stops working. We need to PUSH this information into their > faces, with large posters carrying promises of rainbow coloured unicorns > if they comply today(!). In addition to adding clear warnings in the > log files for a looong time. >=20 > So I propose: >=20 > - We add the warning about removing --keysize for both v2.4 and v2.5. >=20 > - Add a warning in v2.4 and v2.5 that ciphers with block sizes < 128 > bits will be *removed* in v2.6 >=20 > - When removing those ciphers in v2.6, we can remove --keysize together > with the ciphers, as it will no longer be valid. But --keysize needs > to be a NOP for some time (with a warning it has no effect), to avoid > OpenVPN stopping to run on upgrades. Okay. Instead of sending the keysize removal patch, I'll send a patch that warns that small block ciphers will be removed in 2.6. Can you then do s/2.5/2.6/ on the patch, or shall I send a v2? -Steffan --sbLx2pSinfxWixKlxwJ39OMvXm8U8nMUi-- --kIU114eCDvOl8nWDK1dwu9EtL1HORkGIh Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJZkYbKAAoJEEEwndWOY1w5fUMIAIdfSbYr3EG5ixMHXeLtZvn9 dTHKOJBb3YrxjkVmArRnKtD+RzetaAHpqTGfkupqskGqW+lswMuq6ocaqAJU6NSY l76c7nS5tzhrGNaWHdpoV+pZ7h7tub941OzcYcSUbQ7wEyGdm85zPiViLqMHD+eE Xuf9EQ0ujRkOsY2yDEUj5y0h/nMgmfJI1UI30aufITlrSK1t55gx4qkm1RDu7/4C DGUqv5VrZm7ud/N2FIq/NLFZRXTL7UD/hm5dgA7BMZQYsMnG6z9JslSIcWSd+t65 HebPS3P5XOUrUwaLT4m19fa4uwj7gexgp5e9Q2SilNi2tzXBjSIaSw/+5LIK6VA= =nTyj -----END PGP SIGNATURE----- --kIU114eCDvOl8nWDK1dwu9EtL1HORkGIh--