Re: ocserv AnyConnect DTLS cipher

[xabi]

Hi,

I'm checking this issue as it seems it's not yet implemented the
AES-256-CBC in ocserv, I've seen this
https://gitlab.com/openconnect/ocserv/merge_requests/86 and I want to
know if there is a plan to deploy it in version 0.12.2 or if I can
compile it from source just to check it if it's working.

Also I want to know if using DTLS insted TLS via TCP will increase
performance, any experience?

thanks

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Re: ocserv AnyConnect DTLS cipher

[Daniel Lenski]

On Tue, Jul 17, 2018 at 10:45 PM, Nikos Mavrogiannopoulos
 wrote:
>
> On Mon, 2018-07-16 at 16:09 -0500, Marc West wrote:
> > Hi,
> >
> > Is there a way to have the latest Cisco AnyConnect 4.6 clients use
> > ocserv with a stronger DTLS cipher than the default
> > RSA_AES_128_SHA1?
> > When the same version of AnyConnect connects to an ASA the DTLS
> > cipher
> > shows as DHE_RSA_AES256_SHA, which GnuTLS 3.5.18 on my ocserv box
> > should
> > also support. I have tried playing around with the
> > cisco-client-compat/dtls-legacy/dtls-psk/match-tls-dtls-ciphers
> > config
> > options, but understand some of those are mutually exclusive.
> >
> > I plan to force TCP and TLS1.2 with GCM ciphers for most AnyConnect
> > clients with ocserv which works fine, but would like to support the
> > "best DTLS possible" (or at least match the ASA cipher) for a few
> > cases where TCP file transfer throughput through AnyConnect is
> > important (seeing about 3x throughput via DTLS).
> >
> > `occtl show user` with ocserv 0.12.1 and AnyConnect 4.6.01103:
> > TLS ciphersuite: (TLS1.2)-(ECDHE-RSA-SECP521R1)-(AES-256-GCM)
> > DTLS cipher: (DTLS0.9)-(RSA)-(AES-128-CBC)-(SHA1)
>
> You cannot with the current ocserv as it doesn't support anything but
> aes-128 or 3des for compatibility with anyconnect. You could try a
> patch like the one below if AES256-SHA is supported by anyconnect. If
> that works for you, we'd only need a test case for it, to include it in
> the server.

Recent ASAs and AnyConnect *do* support AES-256-CBC. I get this when
connecting to a couple different ASAs:

  (DTLS0.9)-(RSA)-(AES-256-CBC)-(SHA1)

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Re: ocserv AnyConnect DTLS cipher

[Nikos Mavrogiannopoulos]

On Mon, 2018-07-16 at 16:09 -0500, Marc West wrote:
> Hi,
> 
> Is there a way to have the latest Cisco AnyConnect 4.6 clients use 
> ocserv with a stronger DTLS cipher than the default
> RSA_AES_128_SHA1?  
> When the same version of AnyConnect connects to an ASA the DTLS
> cipher 
> shows as DHE_RSA_AES256_SHA, which GnuTLS 3.5.18 on my ocserv box
> should 
> also support. I have tried playing around with the 
> cisco-client-compat/dtls-legacy/dtls-psk/match-tls-dtls-ciphers
> config 
> options, but understand some of those are mutually exclusive.
> 
> I plan to force TCP and TLS1.2 with GCM ciphers for most AnyConnect 
> clients with ocserv which works fine, but would like to support the 
> "best DTLS possible" (or at least match the ASA cipher) for a few 
> cases where TCP file transfer throughput through AnyConnect is
> important (seeing about 3x throughput via DTLS).
> 
> `occtl show user` with ocserv 0.12.1 and AnyConnect 4.6.01103:
> TLS ciphersuite: (TLS1.2)-(ECDHE-RSA-SECP521R1)-(AES-256-GCM)
> DTLS cipher: (DTLS0.9)-(RSA)-(AES-128-CBC)-(SHA1)

You cannot with the current ocserv as it doesn't support anything but
aes-128 or 3des for compatibility with anyconnect. You could try a
patch like the one below if AES256-SHA is supported by anyconnect. If
that works for you, we'd only need a test case for it, to include it in
the server.

regards,
Nikos
diff --git a/src/worker-http.c b/src/worker-http.c
index fd6b998e..65c40fc9 100644
--- a/src/worker-http.c
+++ b/src/worker-http.c
@@ -103,6 +103,16 @@ static const dtls_ciphersuite_st ciphersuites[] = {
 .server_prio = 80,
 .txt_version = "3.2.7",
 },
+   {
+.oc_name = "AES256-SHA",
+.gnutls_name =
+"NONE:+VERS-DTLS0.9:+COMP-NULL:+AES-256-CBC:+SHA1:+RSA:%COMPAT",
+.gnutls_version = GNUTLS_DTLS0_9,
+.gnutls_mac = GNUTLS_MAC_SHA1,
+.gnutls_kx = GNUTLS_KX_RSA,
+.gnutls_cipher = GNUTLS_CIPHER_AES_256_CBC,
+.server_prio = 60,
+},
{
 .oc_name = "AES128-SHA",
 .gnutls_name =
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