On Fri, Dec 10, 2021 at 10:09 AM Gert Doering <g...@greenie.muc.de> wrote:
>
> Hi,
>
> On Fri, Dec 10, 2021 at 02:06:51PM +0100, Arne Schwabe wrote:
> > Patch v3: fix errors with mbed TLS without having md_kt to const char *
> > patch
> > also applied, fix logic inversion in tls_crypt_tk
>
> Thanks, this is much better than v2 - now all client-side tests pass
> that led to "openvpn exiting" previously, or SIGSEGV'ing.
>
> *BUT* - it totally fails to work on a connection that negotiates BF-CBC,
> though, both with mbedTLS 2.27.0 and with OpenSSL 1.1.1l - I did not see
> it in the client side tests first (because I only ran a limited subset),
> but it is easily triggered by connecting to a 2.3 server, requiring
> fallback to BF-CBC.
>
> It also fails all server side tests that end up in trying to use BF-CBC
> (long e-mail cut short).
>
> Most notable indication is: with an older binary, I get these lines
> in the log:
>
> 2021-12-10 15:53:14 us=406619 cron2-freebsd-tc-amd64-24/194.97.140.21:40161
> Outgoing Data Channel: Cipher 'BF-CBC' initialized with 128 bit key
> 2021-12-10 15:53:14 us=406645 cron2-freebsd-tc-amd64-24/194.97.140.21:40161
> WARNING: INSECURE cipher (BF-CBC) with block size less than 128 bit (64 bit).
> This allows attacks like SWEET32. Mitigate by using a --cipher with a
> larger block size (e.g. AES-256-CBC). Support for these insecure ciphers will
> be removed in OpenVPN 2.6.
>
> which are totally missing (!) for master + 7/9v3.
This may be related to this chunk:
@@ -2762,16 +2762,19 @@ do_init_crypto_tls_c1(struct context *c)
* Note that BF-CBC will still be part of the OCC string to retain
* backwards compatibility with older clients.
*/
+ const char* ciphername = options->ciphername;
if (!streq(options->ciphername, "BF-CBC")
|| tls_item_in_cipher_list("BF-CBC", options->ncp_ciphers)
|| options->enable_ncp_fallback)
{
- /* Do not warn if the if the cipher is used only in OCC */
- bool warn = options->enable_ncp_fallback;
- init_key_type(&c->c1.ks.key_type, options->ciphername,
options->authname,
- true, warn);
+ ciphername = "none";
}
+ /* Do not warn if the cipher is used only in OCC */
+ bool warn = options->enable_ncp_fallback;
+ init_key_type(&c->c1.ks.key_type, ciphername, options->authname,
+ true, warn);
+
Selva
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