sshd Assertion failed after main-n279609-e9bcf7cb96de -> main-n279623-5205b32de3fb

From: David Wolfskill <david_at_catwhisker.org>
Date: Fri, 15 Aug 2025 11:57:45 UTC
Yesterday, I had updated the developemnt machines to:

FreeBSD 15.0-PRERELEASE #302 main-n279609-e9bcf7cb96de: Thu Aug 14 10:55:32 UTC 2025     root@freebeast.catwhisker.org:/common/S4/obj/usr/src/amd64.amd64/sys/GENERIC amd64 1500060 1500060

Today's update was to:

FreeBSD freebeast.catwhisker.org 15.0-PRERELEASE FreeBSD 15.0-PRERELEASE #303 main-n279623-5205b32de3fb: Fri Aug 15 11:10:29 UTC 2025     root@freebeast.catwhisker.org:/common/S4/obj/usr/src/amd64.amd64/sys/GENERIC amd64 1500060 1500060

The cited machine runs headless, so inability to ssh in is proving
awkward.  (I was able to login on the serial console, and ssh out
from there, FWIW.)

I also note that "sudo" claims my login isn't in sudoers; while that
is (technically) true, it has been thus for years: I'm using group
membership (in "wheel" -- as I have for decades), though "groups"
seems to detect the group membership OK.

I had worked around recent issues with library bumps, and I run ssh
from base (vs. ports/packages).

If I "service sshd stop", then fire up sshd in debug mode from the
seroial console, then try to ssh in, I see a fair bit of stuff that
I suspect is not especially relevant or interesting (because t loks
fairly normal), ending with:

...
debug1: attempt 1 failures 0 [preauth]
debug1: userauth_pubkey: publickey test pkalg rsa-sha2-512 pkblob RSA SHA256:Oo/+Lm/ZaJCct0htUaKgWUM1x/EB11h/FDUnzhJLI4w [preauth]
Assertion failed: (saved_egroupslen > 0), function temporarily_use_uid, file /usr/src/crypto/openssh/uidswap.c, line 134.
Abort

Maybe that's a sufficient clue for someone cleverer than I.

Peace,
david
-- 
David H. Wolfskill                              david@catwhisker.org
Of course firing the statistician will force the statistics to conform!

See https://www.catwhisker.org/~david/publickey.gpg for my public key.