Re: [gentoo-user] Ssh problem : half-solved

[Philip Webb <purslow@ca.inter.net>]

190310 Nils Freydank wrote:
> Am Sonntag, 10. März 2019, 08:25:54 CET schrieb Philip Webb:
>> I updated Ssh yesterday :
>> [...]
>>   ssh x.y.z
>>   Unable to negotiate with 128.100.160.1 port 22: no matching key
>> exchange method found. Their offer:
>> diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1
> ssh tells you straight forward what the issue is:
> Within the key exchange at the begin of the communication
> there was no way to establish a connection between server and client,
> probably because the client has a more secure setup than the server.
> This happens mostly due to old ssh versions serverside.

Yes, they mb a bit slow to upgrade.

> You can find solutions pretty fast
> by just searching for "Their offer: <key exchange offers>",
> e.g. https://unix.stackexchange.com/questions/340844/
> how-to-enable-diffie-hellman-group1-sha1-key-exchange-on-debian-8-0

That forum contains a solution :

  ssh -oKexAlgorithms=+diffie-hellman-group1-sha1 123.123.123.123

That gets me thro' & I can do my work there.

> Enable legacy and possible less secure key exchange formats and ciphers
> only per server and not globally
> and if possible upgrade the SSH server version.

However, I've tried to insert an instruction in config files,
but nothing changes after a reboot.
I've tried adding to  ~/.ssh/config  &  /etc/ssh/ssh_config :

  Host 128.100.160.1
    KexAlgorithms +diffie-hellman-group1-sha1

That is what seems to be required by 'man 5 ssh_config'.

Can anyone suggest what + where to tell Ssh to do it every time ?

>> 'x.y.z' disguises the site's URL, which doesn't seem to be a problem.
> That is indeed perfectly fine;
> you might want to hide the IP address in the future as well ;-)

Indeed (red face) : it was at the end of my day.
No point in trying to hide it now (wry smile).

-- 
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