[winswitch] Issue 270: Winswitch unable to connect over ssh from MS Windows to server running openssh 6.7

[Antoine Martin]

On 18/08/15 14:49, Fabian Ritzmann wrote:
> Hi,
>
> Since I am Trac-impaired (see my previous email to this mailing list), I am sending my comments via email. I was trying to connect from a MacBook with Winswitch 0.12.21-r5329 to an Arch Linux server running OpenSSH 7.0p1. The SSH server is refusing the connection with this error message:
>
> sshd[20761]: fatal: Unable to negotiate with 10.128.133.54: no matching key exchange method found. Their offer: diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1 [preauth]
>
> This looks like the same issue that this Windows user reported in <https://winswitch.org/trac/ticket/270> with OpenSSH 6.7. The suggested work-around in the issue is to reenable the DH SHA1 key exchange, which I don't consider an option because it compromises security and exposes the host to the Logjam attack.
>
> I would hope that this issue gets more traction because it is an issue with any secure installation of OpenSSH and not specific to the Windows Winswitch client.
Until this issue is fixed in Twisted conch (the SSH layer), there is
absolutely nothing we can do about it.
Here's the more recent upstream ticket:
http://twistedmatrix.com/trac/ticket/7717

Cheers
Antoine

>
> Fabian
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