The latest page cache-related LPE, even though it's not Thursday night (here). EL9 kernels don't have the modules enabled, and the PoC doesn't build on Debian 13 or Ubuntu 24.04, whether or not that means they're safe.
Any university or national HPC system as I'd understand the term is multi-user.
There are also things like the extensive high energy physics WLCG compute federation, which is somewhat different, but can potentially be compromised quickly at large scale. For the original copy-fail we didn't want to drain our WLCG Alma9 cluster, or just kill all the jobs like the university HPC system. We got eBPF mitigation in place within a couple of hours, relieved the exploit signature wasn't in logs from the night before. That would have been done earlier if Proofpoint hadn't bounced the forwarded oss-security article as "contains malware"; sigh.
Can't really speak to the point of the guy you're replying to, but the FreeIPA implementation via SSSD does more than just Kerberos tickets. Actually, I think the Kerberos based stuff as it relates to SSH is GSSAPI as part of sshd itself and has little to do with sssd, though I could be wrong.
That said...
If I'm remembering things correctly (and it's been a looong while since I've played with this), FreeIPA's client configures sshd with an AuthorizedKeysCommand that executes a program that queries sssd for the list of authorized keys for a given user. Sssd then uses a plugin to query the LDAP server @ FreeIPA to get the list of keys.
There's also SSHFP (I think) records in DNS if you're using FreeIPA's DNS servers. These provide the host keys for servers for your ssh client to check against. Not sure if that's integrated into ssh itself or something else -- I can't remember how it's implemented offhand -- but it's fairly nifty since you never see the TOFU prompt (or it would be if DNS was actually secure, anyway).
Yes, FreeIPA is Kerberos+LDAP+X.509 CA, and GSSAPI is in OpenSSH (normally with the key exchange patch). SSSD is a local mechanism, not network authentication. I mentioned authorized keys distribution mechanisms elsewhere, but I was thinking authentication (c.f. OIDC), not authorization.
Yes, but its authN components only act locally, and PAM is optional for sshd. It can/does call out to network services like Kerberos/LDAP given a password, of course, but I was thinking of network authN connected directly with OIDC somehow, for which I don't know a mechanism in vanilla OpenSSH. (I don't know what Authentik does for this -- I could imagine it's behind the scenes somehow.) I should probably look it up sometime.
My understanding is since it's an agent running on the target, possibilities will be quite extensive. But it is relatively new and there is no stable release of it yet.
Life is easier if you can use Kerberos SSO, i.e. GSSAPIAuthentication in OpenSSH. (If we're talking certificates, presumably it is OpenSSH, or does anything else implement them?)
I don't want to have to get a special purpose credential when I have a TGT which can work generally, and is at least required for secure remote filesystem access.
You have to manage extra infrastructure for certificates and, as a user, have the friction of firing up a JavaScript-enabled web browser via an additional tool, assuming "real IdP" means using OIDC. Unfortunately that flow is actually needed for remote systems and something like Edugain federation, since Moonshot/IETF ABFAB failed, but at least Shibboleth can use the TGT, and it's not the Globus horror.
Every serious shop of any real size is already managing an OIDC IdP (you need one for whatever SAAS apps your team is using along with any internal web applications you're using). Why not just link it to something that can issue short-lived SSH certificates? That's also the cleanest way to get strong multifactor auth for SSH (certificates issued only through an OIDC progress minted with MFA requirements).
Setting up Kerberos in 2026 feels somewhat close to malpractice to me.
I'm happy for anyone who doesn't have MS Windows/Active Directory -- so Kerberos -- in their organization, but I'd need (Free)IPA or similar for user/access management anyway. Certificates are an extra layer of SSH-specific complexity, which concerns me for security even if it doesn't involve some third party. MFA is needed once a day, say, for SSO to all Kerberized services. [As I understand it, "managing an OIDC IdP" includes shipping the contents of Active Directory to Entra, heaven help us.]
> Setting up Kerberos in 2026 feels somewhat close to malpractice to me.
Microsoft (if that means anything, but they've done good work) and Red Hat obviously disagree, along with decades' experience. It is malpractice not to secure NFS mounts (and other network filesystems with sensitive data), and that means Kerberos.
I wish that (still) worked reliably, but it can unfortunately get one into trouble with some compilers and some optimization modes that assume that NaNs are undefined behavior.
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