Re: Can't connect with some clients

[Emiliano Gonzalez <egonzalez.hiperion@xxxxxxxxx>]

Solved!!!
I'm using mbedcrypto and do not have ChaCha20-Poly1305. Disabling this
cypher works ok.
But it is allowed to enable in this situation ChaCha20 and
cipher->max_blocks = ((uint64_t)1 << 30) / cipher->blocksize crash with
division by zero.
Shouldn't this situation be controlled? It is not an error?

El mié, 13 de ene. de 2021 a la(s) 07:58, Jakub Jelen (jjelen@xxxxxxxxxx)
escribió:

> On 1/12/21 4:09 PM, Emiliano Gonzalez wrote:
> > I have a ssh server.
> >
> > When I connect with the client on Fedora 32 ssh there are no problems.
> >
> > With PuTTY: Release 0.74 I can't connect with error: Couldn't agree a
> > host key algorithm (available: rsa-sha2-512, rsa-sha2-256)
>
> That sounds like an issue of PuTTY, that it can not use the RSA SHA2
> hostkey algorithms from RFC8332.
>
> As a workaround, you can configure your server with different hostkeys
> (ed25519) so incompatible clients can connect too.
>
> >  From Centos 7 ssh server crash. In packet.c (line 1862):
> >
> > |/* For smaller blocks use limit of 1 GB as recommended in RFC4253 */
> > cipher->max_blocks = ((uint64_t)1 << 30) / cipher->blocksize; |
> >
> > cipher->blocksize is 0;
>
> What cipher is used for this connection? There is no cipher that would
> have blocksize == 0.
>
> Can you get a debug log?
>
> Regards,
> --
> Jakub Jelen
> Senior Software Engineer
> Crypto Team, Security Engineering
> Red Hat, Inc.
>
>
>