Archived
beatzaplentyandClaude Sonnet 4.6
f46ae18672
Check NixOS configurations / eval-hosts (pull_request) Failing after 9m43s
OpenSSH 10.0 tightened AuthorizedKeysCommand security by checking every path component of the command binary for group/world-write permission. /nix/store is 1775 (group-writable by nixbld), so sshd silently skips the command for any binary in the Nix store — causing IPA pubkey auth to silently fail with no diagnostic. Fix: copy sss_ssh_authorizedkeys to /usr/local/bin via systemd tmpfiles (C+ copies the file rather than symlinking, so the path at runtime is root-owned/755 throughout), and point AuthorizedKeysCommand at the copy. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
100 lines
3.9 KiB
Nix
100 lines
3.9 KiB
Nix
# Fully declarative FreeIPA domain membership.
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#
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# Configures security.ipa (SSSD, Kerberos, PAM, NSSwitch) and places a
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# pre-provisioned host keytab via sops-nix so no imperative ipa-client-install
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# step is needed after deployment.
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#
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# Usage (in a host.nix imports list):
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# (import ../../modules/ipa/client.nix {
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# keytabSopsFile = ../../secrets/nix-cache.keytab;
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# caCertFile = ../../certs/ipa-ca.crt;
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# })
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#
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# One-time operator setup per host (do this BEFORE deploying):
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#
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# 1. Fetch the IPA CA certificate (public — safe to commit):
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# curl -o certs/ipa-ca.crt http://<ipa-server>/ipa/config/ca.crt
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# Replace the placeholder at certs/ipa-ca.crt and commit it.
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#
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# 2. On the FreeIPA server, add the host and generate a keytab:
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# ipa host-add <fqdn> --ip-address=<ip>
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# ipa-getkeytab -s <ipa-server> -p host/<fqdn> -k /tmp/<host>.keytab
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#
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# 3. sops-encrypt the keytab as a binary secret from your admin machine
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# (must run from repo root; sops matches creation rules against the file
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# path, so copy to secrets/ first and encrypt in-place):
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# cp /tmp/<host>.keytab secrets/<host>.keytab
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# sops -e --input-type binary -i secrets/<host>.keytab
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# Add secrets/<host>.keytab to .sops.yaml with the host's age key as a
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# recipient (see the nix-cache.keytab entry for the pattern), then run:
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# scripts/secrets/sync-host-keys.sh <target> # if not done yet
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# sops updatekeys secrets/<host>.keytab
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# Commit the encrypted file.
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#
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# 4. nixos-rebuild switch (or create-proxmox-resource.sh) — no further
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# manual enrollment steps required.
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#
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# vars dependencies: homeDomain, ipaServer
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{ keytabSopsFile, caCertFile }:
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{ config, lib, pkgs, vars, ... }:
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let
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realm = lib.strings.toUpper vars.homeDomain;
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fqdn = "${config.networking.hostName}.${vars.homeDomain}";
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# "sweet.home" -> "dc=sweet,dc=home"
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basedn = lib.strings.concatMapStringsSep "," (c: "dc=${c}") (lib.strings.splitString "." vars.homeDomain);
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# security.ipa.certificate expects a derivation (package), not a raw path.
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caCertPkg = pkgs.writeText "ipa-ca.crt" (builtins.readFile caCertFile);
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in
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{
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security.ipa = {
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enable = true;
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domain = vars.homeDomain;
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realm = realm;
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server = vars.ipaServer;
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certificate = caCertPkg;
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basedn = basedn;
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ipaHostname = fqdn;
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offlinePasswords = true;
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cacheCredentials = true;
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};
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# Fetch SSH public keys from IPA so users can log in with the key stored
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# in their IPA profile rather than needing ~/.ssh/authorized_keys on every
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# host. sss_ssh_authorizedkeys queries SSSD (which queries IPA LDAP).
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#
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# /nix/store is 1775 (group-writable by nixbld). OpenSSH 10.0+ rejects
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# AuthorizedKeysCommand binaries whose path contains any group-writable
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# component, silently skipping the command. Copy to /usr/local/bin (all
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# components root-owned, 755) so the path passes sshd's safety check.
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systemd.tmpfiles.rules = [
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"d /usr/local 0755 root root - -"
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"d /usr/local/bin 0755 root root - -"
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"C+ /usr/local/bin/sss_ssh_authorizedkeys 0555 root root - ${pkgs.sssd}/bin/sss_ssh_authorizedkeys"
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];
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services.openssh.extraConfig = ''
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AuthorizedKeysCommand /usr/local/bin/sss_ssh_authorizedkeys %u
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AuthorizedKeysCommandUser nobody
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'';
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# Create the home directory on first login if it doesn't exist yet.
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# IPA users have no pre-created home on the host; without this sshd
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# opens a session to a non-existent directory and resets the connection.
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security.pam.services.sshd.makeHomeDir = true;
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# Host keytab: pre-provisioned on the IPA server, sops-encrypted binary.
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# Placed at /etc/krb5.keytab before SSSD starts so the host authenticates
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# to IPA without running ipa-client-install.
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sops.secrets."ipa-host-keytab" = {
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sopsFile = keytabSopsFile;
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format = "binary";
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path = "/etc/krb5.keytab";
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owner = "root";
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group = "root";
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mode = "0600";
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restartUnits = [ "sssd.service" ];
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};
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}
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