Re: [mdk-re] SSHd

[Sergey Vlasov <vsu@mivlgu.murom.ru>]

On Wed, 22 Aug 2001 23:14:00 -0700
Al Nikolov <al@smena.ru> wrote:

> AN> Никак не получается логиниться на SSHd с помощью ключей. В манах
> AN> белиберда какая-то, в /etc/openssh зачем-то каталоги
> AN> authorized_keys...
> 
> Сам разобрался. Беда была с PuTTY.
> 
> Однако, кто-нибудь понимает смысл таких слов из его фака?
> 
> Question: Does PuTTY support the SSH 2 protocol?
> Answer: Yes, as of version 0.50. Upgrade now! 
> Public key authentication in SSH 2 is not supported, for security reasons
> 
> 
> Какой такой резон?

Так на странице же как раз на security reasons ссылка болтается:

    * Creating a DSA signature requires a 160-bit random number k. This is
used in computing the signature itself, and then discarded.
    * However, if k were to be accidentally made known to the recipient
along with the public key, the signature, and the hash of the message,
then they would have enough information to deduce the private key -
completely compromising the key and allowing the attacker to forge any
number of signatures with it.
    * Furthermore, if k is not actually known to the attacker but the
random number generation is weak enough to make it guessable in feasibly
many attempts, then the signature also contains enough information to let
the attacker know when he has guessed the correct k - and then the key is
compromised as before.
    * Therefore, a DSA signature should never be created on a platform
with less than perfect random number generation. PuTTY's random numbers
are as good as I know how to make them, and I welcome improvements, but I
don't think they're good enough to trust the security of an authentication
key to.

Кстати, в новых development-версиях PuTTY вроде бы появилась поддержка
ключей RSA для SSH2.