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NixOS + TPMs

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16 Jul 2021
@grahamc:nixos.org@grahamc:nixos.orgrun clevis inside a nix-build with the sandbox disabled :see14:52:18
@grahamc:nixos.org@grahamc:nixos.org * run clevis inside a nix-build with the sandbox disabled14:52:19
@grahamc:nixos.org@grahamc:nixos.org🙈14:52:22
@andi:kack.itandi-The best of none of the worlds?14:52:47
@grahamc:nixos.org@grahamc:nixos.orgbingo14:53:07
@grahamc:nixos.org@grahamc:nixos.orgokay new learning 15:01:07
@grahamc:nixos.org@grahamc:nixos.org
In reply to @grahamc:nixos.org
like, I think the nvram is for "I don't have a filesystem yet!" stuff, plus perhaps password attempt counters

this isn't stored in an arbitrary location in nvram, and it isn't on a per-secret basis, but an overal property of the TPM: a counter of failures:

[nix-shell:~]# tpm2 getcap properties-variable > prop-vals.2

[nix-shell:~]# diff prop-vals.1 prop-vals.2
29c29
< TPM2_PT_LOCKOUT_COUNTER: 0x7
---
> TPM2_PT_LOCKOUT_COUNTER: 0x8

15:02:21
@grahamc:nixos.org@grahamc:nixos.org
Note that the DA lockout counter decrements automatically every TPM_PT_LOCKOUT_INTERVAL seconds, in your case 100s.
15:04:29
@grahamc:nixos.org@grahamc:nixos.orgmine is: TPM2_PT_LOCKOUT_INTERVAL: 0x1C20 so 2 hours15:04:42
@grahamc:nixos.org@grahamc:nixos.orgI sure wish there was some crash course already put together on all this15:05:57
@andi:kack.itandi-I'll book one with DS once you are at that point. There is a friends&family discount, right?15:06:25
@grahamc:nixos.org@grahamc:nixos.orghaha15:07:36
@grahamc:nixos.org@grahamc:nixos.orgI should get a TPM simulator instead of putting my actual TPM in lockout15:09:01
@grahamc:nixos.org@grahamc:nixos.orgdid you figure out how to run the simulator?15:10:51
@grahamc:nixos.org@grahamc:nixos.orga very annoying thing about TPMs is the management thing15:22:05
@andi:kack.itandi-I haven't continued that journey yet. I'm trying to get things organzied for the weekend. Not going to have much more time besides during the Nights.16:20:04
@andi:kack.itandi- invited @mic92:nixos.devMic92 (Old).16:35:10
@mic92:nixos.devMic92 (Old) joined the room.16:35:19
@mic92:nixos.devMic92 (Old)I kinda stopped using my yubikey as well16:35:34
@mic92:nixos.devMic92 (Old)Is there an ssh-agent for tpm2?16:36:34
@mic92:nixos.devMic92 (Old)Otherwise I am ready: https://www.lenovo.com/us/en/laptops/thinkpad/thinkpad-x/ThinkPad-X13-Intel-/p/20T2CTO1WWENUS0/customize16:36:48
@andi:kack.itandi-You can use the TPM as pkcs11 device16:36:49
@andi:kack.itandi-I've been doing that for a few days now16:36:59
@mic92:nixos.devMic92 (Old)Does openssh supports pkcs11?16:37:29
@mic92:nixos.devMic92 (Old)I rather prefer over gnupg codebase16:37:39
@mic92:nixos.devMic92 (Old) * I rather prefer theirs over gnupg codebase16:37:48
@andi:kack.itandi-

Yeah, you basically enable the tpm2 settings in the nixos options. Including the pkcs11 shim and then:

ssh-keygen -D /run/current-system/sw/lib/libtpm2_pkcs11.so
16:37:59
@mic92:nixos.devMic92 (Old)Nice.16:38:10
@andi:kack.itandi-Yeah except that on current unstable you have to patch the tpm2-tss lib or rather remove our dlopen patch.16:38:37
@andi:kack.itandi-I've not had a moment to upstream that yet.16:38:46

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