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mw feaccf201d docs(learnings): record YubiKey + Dell E7250 air-gapped keygen host setup 
Session record 2026-06-24: YubiKey inventory, GPG commit-signing plan,
reusable SPECCOL inventory/provisioning stick (dock-aware), and full
hardening + provisioning of the Dell Latitude E7250 as the dedicated
air-gapped keygen/forensic host (BIOS A24, Secure Boot, AMT off, radios
off, dist-upgraded, Phase-2 tooling installed). TPM 1.2-only (hardware
limit). Captures key gotchas (yubikey-manager package name, FAT32 +x,
TXT-before-TPM-clear, E7250 not on LVFS) and the refined architecture.
2026-06-24 20:02:43 +02:00

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description tags last_updated
Session record (2026-06-24) of detecting the YubiKey, planning GPG commit signing, building a reusable SPECCOL inventory/provisioning stick, and hardening + provisioning a Dell Latitude E7250 as a dedicated air-gapped keygen/forensic host.
learning
yubikey
gpg
security
air-gap
latitude-e7250
2026-06-24

YubiKey + Dell E7250 air-gapped keygen host - 2026-06-24

Summary

Detected and inventoried the attached YubiKey; researched 2026 best practice for hardware-backed Git commit signing; wrote a baby-step plan; then procured, hardened, and provisioned a dedicated Dell Latitude E7250 as the permanent air-gapped keygen/forensic host. Built a reusable SPECCOL USB toolkit (inventory + provisioning scripts, verified BIOS, checklist) along the way.

Outcome: E7250 is fully hardened + provisioned and ready to go offline for PGP key generation. The YubiKey remains the daily-carry signer; the Type-C USB will hold the LUKS-encrypted key recovery backup (pending keygen).

Decisions (with rationale)

Decision Choice Why
Signing approach GPG/OpenPGP on YubiKey (not SSH ed25519-sk) Secret keys are exportable -> a true LUKS recovery backup on USB is possible (requirement #3).
Keygen environment Dedicated air-gapped host (Dell E7250) instead of a re-booted live USB Reproducible; Certify key never touches a networked machine; reusable for forensic work.
Key identity Michael Wegener <mw@satware.com>; subkeys ed25519(S)/cv25519(E)/ed25519(A); 2y expiry; touch required 2026 modern; avoids RSA-deprecation for SSH auth.
Push transport HTTPS + GPG-sign (unchanged) Lowest risk; signing is transport-independent.

Components & final state

1. YubiKey (serial 30836069, FW 5.7.1, USB-A)

  • OTP: slot 1 programmed, slot 2 empty.
  • FIDO2: PIN set (8 tries left), 4 credentials - google.com (Jane Alesi), auth.satware.ai, git.g-b-c.de, github.com (satwareAG-ironMike).
  • OATH: empty. PIV: factory-defaults/empty. OpenPGP: empty, sign-PIN was blocked.
  • Note: existing GPG keyring has 3 expired ed25519 keys tied to a different card serial (24530904) - stale references, not on this key.

2. Plan (committed)

  • docs/plans/2026-06-24-yubikey-gpg-github-signing.md (commit 5a714e6).
  • 9 phases (0-9): remediate -> air-gapped keygen -> LUKS backup -> transfer to YubiKey -> configure workstation -> register with GitHub -> Ansible -> recovery -> 2nd YubiKey.

3. Boot stick (Type-C USB, 29 GB)

  • Debian Live 13.5.0 Trixie XFCE ISO, verified (SHA512 + Dell... Debian CD OpenPGP signature), dd'd clean at ~40 MB/s.

4. SPECCOL toolkit stick (FAT32, label SPECCOL, ~1.9 GB) - reusable

toolkit/collect-specs.sh            dock-aware inventory (TPM version, radios,
                                    TB dock nvm/serial, fwupd, robust tooling check)
devices/latitude-e7250/provision.sh apt update + full-upgrade + tooling + autoremove
                                    + logging + re-inventory (idempotent)
devices/latitude-e7250/checklist.md hardening + provisioning checklist
devices/latitude-e7250/bios/        E7250A24.exe (verified) + flash instructions
devices/latitude-e7250/logs/        one provision log per run
inventory/<hostname>/               collected hw-specs baselines
README.txt                          incl. FAT32 "+x" rule (run via `bash`)

5. Dell Latitude E7250 (Service Tag JQN3P32) - the air-gapped host

  • i7-5600U (vPro), 16 GB RAM, SK hynix SC210 mSATA 256 GB SSD (TRIM), Intel HD 5500.
  • Debian 13 Trixie, kernel 6.12.94 (dist-upgraded), LUKS on root+swap.
  • Hardened: BIOS A24; Secure Boot enabled (+ kernel lockdown); AMT/vPro disabled (MEBx); Wi-Fi off (gone from bus); Bluetooth hard-blocked; WWAN (Dell Gobi 5809e 4G LTE) off; TPM cleared -> 1.2-only (hardware limit - no 2.0 option in BIOS A24; non-blocking).
  • Provisioned: full dist-upgrade applied; 20/20 Phase-2 tools installed (scdaemon, pcscd, pcsc-tools, yubikey-manager/ykman, yubikey-personalization, cryptsetup, parted, fdisk, dosfstools, e2fsprogs, paperkey, tpm2-tools, fwupd, hdparm, smartmontools, nvme-cli, usbutils, pciutils, rfkill). 0 packages pending.
  • Dock: Dell E-Port Replicator (legacy bottom-connector; SMSC USB hubs only; no Thunderbolt, no serial, no updatable firmware).

Architecture (refined)

  • E7250 (offline, LUKS) = keygen + recovery host; holds the Certify key.
  • YubiKey = daily-carry commit/tag signer on the workstation.
  • Type-C USB = offline LUKS-encrypted recovery backup of the keys (pending Phase 3).

Key learnings / gotchas

  • LVFS: the E7250 is NOT on the LVFS - no fwupd/.cab BIOS path; Dell dock also not updatable. BIOS update only via the Dell .exe (F12 BIOS Flash Update or FreeDOS).
  • Dell package naming: the YubiKey Manager CLI is Debian package yubikey-manager (provides the ykman binary), not ykman. One invalid name aborts the entire apt-get install. Fixed in provision.sh.
  • FAT32 +x: the SPECCOL stick can't store the executable bit - scripts must be invoked as bash <script> (the toolkit scripts chain each other via bash).
  • TXT vs TPM: Intel TXT must be disabled before clearing the TPM ("TXT must be disabled before clearing"). TXT is not needed for this host - left disabled.
  • TPM version: /sys/class/tpm/tpm0/tpm_version_major (kernel) is the reliable TPM 1.2-vs-2.0 indicator; /dev/tpmrm0 presence also signals TPM 2.0.
  • OpenPGP sign-PIN block was pre-existing; a ykman openpgp reset will clear it before key transfer (Phase 4).
  • gh auth token for satwareAG-ironMike is invalid on the workstation; git protocol is HTTPS. (Re-auth when starting workstation-side setup.)
  • Plaintext secrets exposure: a yubikey-provision-… folder with unencrypted GnuPG + SSH private keys was on the Type-C USB ("safety net"). It gets destroyed when that stick is repartitioned for the LUKS backup (Phase 3) - same keys exist on the workstation ~/.gnupg/~/.ssh, so nothing is lost.

Verification baselines captured (on the SPECCOL stick)

inventory/michael-latitudee7250/hw-specs-*.txt across: pre-flash (A19) -> post-flash (A24) -> post-provision -> post-TPM-clear. Tooling-detection bugs (scdaemon/pcsc-tools/yubikey-personalization binary-name mismatches; ambiguous lsusb messages; ANSI codes from fwupd) were fixed in collect-specs.sh.

Open items / next steps

  1. On the E7250: (optional) set a BIOS/Setup admin password; unplug Ethernet permanently.
  2. Phase 2 - keygen on the E7250 (tmpfs GNUPGHOME): Certify key + S/E/A subkeys. Then Phase 3 (LUKS backup to Type-C USB sdc3) and Phase 4 (transfer to YubiKey; reset OpenPGP app first to clear the blocked sign-PIN).
  3. Workstation side: gh auth login, import public key, configure git signing (Phases 5-6), fold non-secret config into ansible/ (Phase 7).
  4. Procure a 2nd YubiKey for redundancy (Phase 9).

Artifacts produced today

  • docs/plans/2026-06-24-yubikey-gpg-github-signing.md (commit 5a714e6)
  • docs/learnings/2026-06-24-yubikey-e7250-airgap-setup.md (this file)
  • SPECCOL toolkit stick (toolkit + devices/latitude-e7250/* + verified BIOS A24)
  • Type-C USB = current Debian-Live boot stick (29 GB; to be repurposed as the LUKS recovery backup in Phase 3)
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