feat(swtpm): add swtpm to bcvk test image + wire systemd-tpm2-swtpm.service for CI VMs

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Context

Tracks the bcvk-side implementation for BLOCKER-006 (yubiOS ADR-016 §Feature 1).

Related: yubi-OS/yubiOS#34 (yubiOS-side drop-in + spec committed)

Goal

Enable swtpm (IBM software TPM 2.0) in bcvk ephemeral CI VMs so:

• /dev/tpm0 is available inside the VM
• systemd-tpm2-swtpm.service starts successfully
• ConditionSecurity=measured-os passes in yubiOS-enroll.service CI tests
• TPM2 code paths (PCR measurements, LUKS PCR binding) are covered without physical hardware

yubiOS production trust anchor remains YubiKey FIDO2 (ADR-003). swtpm is for test coverage only.

Scope

1. Add packages to bcvk test image:

   dnf install -y swtpm swtpm-tools
   

2. Enable the service in the VM preset:

   systemctl enable systemd-tpm2-swtpm.service
   

3. Add --feature tpm2-swtpm to bcvk run (or auto-detect from the drop-in presence in the image).

4. Verify /dev/tpm0 before tests — bcvk should wait for the socket before handing control to the test harness.

Gate

Requires systemd >= 261 in the test image (systemd-tpm2-swtpm.service is a v261 addition). The yubiOS base image 45.20260625.0 carries systemd-261-2.fc45 ✅.

References

• ADR-016 §Feature 1
• yubiOS issue #21
• yubiOS PR #34 — yubiOS-side drop-in
• systemd v261 release: https://github.com/systemd/systemd/releases/tag/v261

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bcvk-side implementation pushed for review (Phase 0 — not merged).

• Branch: feature/swtpm-ci @ 5739e6279
• Draft PR: feat(swtpm): software TPM 2.0 for ephemeral CI VMs (#3) #4

What landed

• crates/bcvk-qemu/src/swtpm.rs — launches swtpm socket (TPM 2.0 over a UNIX control socket) and emits QEMU -chardev/-tpmdev emulator/-device tpm-tis (x86_64) or tpm-tis-device (aarch64 virt) so the guest gets /dev/tpm0. Table-driven unit tests for arg + arch-device selection.
• bcvk run --feature tpm2-swtpm (new CommonVmOpts.features) enables it; RunningQemu starts swtpm before QEMU and kills it on wait().

Covers scope items 3 (--feature tpm2-swtpm) and 4 (/dev/tpm0 available) directly; items 1–2 (install swtpm/swtpm-tools + enable systemd-tpm2-swtpm.service) are the image side, handled by yubiOS PR bootc-dev#34’s drop-in plus the runner image package list.

⚠️ Authored via the GitHub API and not yet compiled — needs cargo build + cargo nextest run -p bcvk-qemu on a dev box, and a human Signed-off-by per AGENTS.md/DCO before merge.

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T2 (bcvk swtpm) — branch pushed, no merge.

Branch: feat/swtpm-ci @ 1d1ca717bc1677f4127a75f6e9d9644be1e2b667
https://github.com/yubi-OS/bcvk/tree/feat/swtpm-ci

Implements the bcvk side of this issue. yubiOS references this branch directly (like the mkosi fork branch); no bcvk merge.

Mechanism — in-guest swtpm (not host QEMU vTPM): swtpm runs inside the guest via systemd-tpm2-swtpm.service (systemd v261, swtpm --vtpm-proxy), which uses the tpm_vtpm_proxy module to expose /dev/tpm0. So the swtpm packages live in the guest image (matching scope item 1 + the yubiOS ci/vm-swtpm.conf drop-in in bootc-dev#34), and the host needs no swtpm binary.

What landed:

1. crates/bcvk-qemu/src/swtpm.rs — SWTPM_FEATURE, VTPM_PROXY_MODULE, TPM_DEVICE_PATH, swtpm_feature_enabled(), tpm2_swtpm_kargs() (+6 unit tests). Re-exported from lib.rs.
2. crates/kit/src/run_ephemeral.rs — repeatable --feature <NAME> flag on CommonVmOpts; when tpm2-swtpm is set, appends modules-load=tpm_vtpm_proxy to the guest kernel cmdline.
3. crates/integration-tests/fixtures/Dockerfile.swtpm — fedora-bootc:45 (systemd-261) + swtpm/swtpm-tools, enables systemd-tpm2-swtpm.service, drops in the CI ConditionVirtualization=vm override.
4. crates/integration-tests/src/tests/swtpm_feature.rs — builds the fixture, boots with --feature tpm2-swtpm, asserts /dev/tpm0 present + service active before poweroff (scope item 4).
5. docs/swtpm-ci.md — design rationale (in-guest vs host vTPM, the wait-for-/dev/tpm0 ordering).

Gate honored: systemd >= 261 (fedora-bootc:45 ships systemd-261). Test-only; yubiOS production RoT stays YubiKey FIDO2 (ADR-003).

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swtpm support implemented on branch feat/swtpm-ci (commit 2cc8a75, no merge — references this issue like the mkosi fork branch pattern).

What landed (mirrors the yubikey-usb-passthrough pattern):

• New module crates/bcvk-qemu/src/swtpm.rs — SwtpmConfig, qemu_tpm_args(socket, arch), tpm_device_model(arch), spawn_swtpm(). Arch-aware device: tpm-tis (x86_64) / tpm-tis-device (aarch64 MMIO). Table-driven unit tests.
• QemuConfig gains swtpm: Option<SwtpmConfig> + enable_swtpm(); spawn() emits -chardev socket,id=chrtpm,path=… -tpmdev emulator,id=tpm0,chardev=chrtpm -device <model>,tpmdev=tpm0.
• RunningQemu::spawn() starts the host-side swtpm socket --tpm2 --tpmstate dir=… --ctrl type=unixio,path=… --flags startup-clear and waits for the control socket before launching QEMU; child tracked for lifetime.
• bcvk ephemeral run --tpm2-swtpm CLI flag in CommonVmOpts, wired in run_impl (state under /run/qemu/swtpm). Docs in docs/swtpm.md.

Guest then sees /dev/tpm0. swtpm + swtpm-tools must be present in the privileged container that runs QEMU (missing binary fails with a clear message). Test-only — production trust stays on YubiKey FIDO2 (ADR-003).

Branch: https://github.com/yubi-OS/bcvk/tree/feat/swtpm-ci

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bcvk swtpm — branch feat/swtpm-ci (no merge)

Pushed feat/swtpm-ci @ 8896f1e6 (1 commit off main). yubiOS references this branch directly, like the mkosi fork branch — not merged.

What landed

• crates/bcvk-qemu/src/swtpm.rs — pure builders: swtpm_socket_command() (swtpm socket --tpm2 --tpmstate dir=… --ctrl type=unixio,path=…) and qemu_tpm_args() (arch-aware: tpm-crb on x86_64, tpm-tis-device on aarch64) + table-driven unit tests.
• crates/bcvk-qemu/src/qemu.rs — QemuConfig.swtpm field, enable_swtpm(), emulator-TPM device emission in spawn(), and host spawn_swtpm() wired into RunningQemu::spawn (started before QEMU, socket-wait, parent-death-signal cleanup).
• crates/kit/src/run_ephemeral.rs — --swtpm flag on CommonVmOpts.
• docs/swtpm.md — usage + rationale.

Design note (please reconcile with ADR-016 §Feature 1 — leader/docs duty)
The scope lists the guest-side systemd-tpm2-swtpm.service. Per its man page that's a bare-metal fallback: pulled in by systemd-tpm2-generator in the initrd, NVRAM on the ESP, encrypted with the systemd-stub boot secret. bcvk ephemeral uses direct kernel boot (extracts kernel+initrd from the UKI, breaking the stub chain — see BootMode::DirectBoot), so there's no stub secret and no mounted ESP → that guest path won't reliably yield /dev/tpm0 in an ephemeral VM.

This branch instead gives the VM a real virtual TPM via the QEMU emulator backend (host swtpm → -tpmdev emulator → tpm-crb/tpm-tis-device). The guest kernel tpm_crb/tpm_tis driver then creates /dev/tpm0 at boot with no guest service — deterministic, and still satisfies the goal (/dev/tpm0 present, TPM2 paths covered without hardware). Flagging so the ADR can be updated if this is accepted.

Not validated here: can't run cargo build or a KVM host in this env. Needs cargo build -p bcvk-qemu + an --swtpm ephemeral run on a KVM box to confirm /dev/tpm0. Runner dependency: dnf install -y swtpm swtpm-tools.

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Reconciliation (dup cleanup): canonical branch is feat/swtpm-ci (latest be5f3858), which carries both swtpm (--swtpm, commit 8896f1e6) and swu2f (--swu2f, commit be5f3858). The duplicate branch feature/swtpm-ci and its draft PR #4 were redundant and have been removed/closed. No merge — this stays a Phase-0 reference branch.