On 3/9/22 08:52, Alexander Sosedkin wrote: > On Wed, Mar 9, 2022 at 2:47 PM Richard W.M. Jones <rjo...@redhat.com> wrote: >> >> Previous tightening of crypto defaults caused problems with us >> connecting to older ssh servers. >> >> I am particularly interested / worried about sshd from RHEL 5, 6 & 7 >> for virt-p2v and virt-v2v conversions. This broke before, requiring >> us to advise users to set the global policy for the machine to LEGACY >> (thus ironically weakening crypto for everything). >> >> Also I have some ancient network equipment that cannot be upgraded but >> needs older ssh protocols. I can't connect to it from Fedora unless I >> set the crypto policy to LEGACY. >> >> Anyway I'm wondering if the SHA-1 change will impact ssh further? > > IIRC, the only SHA-1 thing that should be left in DEFAULT for SSH > is SHA-1 as HMAC, which doesn't rely on collision resistance. > So, not this round.
SHA-1 HMAC is still considered to be a perfectly good MAC. For new protocols, I recommend using Blake2b instead, but that is purely for performance reasons, not because HMAC-SHA-1 is broken. There are no known attacks on HMAC-SHA-1, and it is actually stronger than AES-128 in CBC-MAC (160 bits of security vs. 128). -- Sincerely, Demi Marie Obenour (she/her/hers)
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