Re: Don't panic (ssh)
On Mon, Jan 14, 2002 at 11:07:38AM +0000, Iain Tatch wrote:
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> On 14 January 2002 at 10:35:17 Thomas Seyrat wrote:
>
> TS> Not if your SSH daemon is up to date :-)
>
> Is the SSHD in the latest potato fully up-to-date, though? I am a very
> recent convert to Debian, having been an avid Slackware fan for the last
> seven years. However one of my (very old) Slack boxen was compromised on
> Christmas Day via the sshd CRC32 vulnerability and I decided to replace it
> with Debian, a distro which has seriously impressed me.
>
> Not wanting the same problem to reoccur, after installation &
> configuration I checked my version of sshd. As far as I could ascertain
> the sshd which comes with the current potato release is OpenSSH
> 1.something (can't say exactly what now as I've removed it and my notes
> are all at home), however iirc it was only using version 1 of the SSH
> protocols, which leaves the vulnerability in place.
According to "SSH, the secure shell" Oreilly and Associates...
Insertion or compensation attack:
Although not an especially easy attack to mount, this is a serious vulnerability. The attack results from composition properties of CRC-32 together with certain bulk ciphers in certain modes. The attack can be avoided altogether by using the 3DES cipher, which is immune.
SSH1 1.2.25, F-Secure SSH1 1.3.5 and later versions as well as all versions of OpenSSH include the crc32 compensation attack detector, designed to detect and prevent this attack. The detector renders the attack harder to mount, but doesn't prevent it entirely. SSH-2 uses cryptographically strong integrity checks to avoid such problems.
Kind Regards
Crispin
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