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Date:      Sun, 12 Sep 2021 05:09:45 +0700
From:      Eugene Grosbein <eugen@grosbein.net>
To:        Ed Maste <emaste@freebsd.org>, freebsd-security@freebsd.org
Subject:   Re: Important note for future FreeBSD base system OpenSSH update
Message-ID:  <e17ea9da-4a3b-a21f-2107-8b94e094974d@grosbein.net>
In-Reply-To: <CAPyFy2Aw8Z3ngiM8YHApjjPRLZVC5MCN8TRQkh6pj2fSeM1zqw@mail.gmail.com>
References:  <CAPyFy2A390kS_C3g=Y9QhQcJ06z_FKUxXsNvi9g2CdWF24pukg@mail.gmail.com> <CAPyFy2B04b0GtWoHFQwxht5vK4_cnApPXpDLXU%2BRvcR=2L9YxA@mail.gmail.com> <CAPyFy2Aw8Z3ngiM8YHApjjPRLZVC5MCN8TRQkh6pj2fSeM1zqw@mail.gmail.com>

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10.09.2021 1:01, Ed Maste wrote:

> To check whether a server is using the weak ssh-rsa public key
> algorithm, for host authentication, try to connect to it after
> removing the ssh-rsa algorithm from ssh(1)'s allowed list:
> 
>     ssh -oHostKeyAlgorithms=-ssh-rsa user@host
> 
> If the host key verification fails and no other supported host key
> types are available, the server software on that host should be
> upgraded.

I have some telco equipment (E1/SS7) based on custom Linux distro built by a vendor:

$ ssh -oHostKeyAlgorithms=-ssh-rsa user@host
Unable to negotiate with X.X.X.X port 22: no matching host key type found. Their offer: ssh-rsa

I've already asked the vendor for possible upgrade and was told that no upgrade will be available.

Will I be able to use ssh_config and following command to re-enable the feature after planned import?

HostKeyAlgorithms ssh-rsa




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