Check NvPCR services in staged UKIs

3 files changed, 33 insertions, 4 deletions

diff --git a/docs/tpm-unlock.md b/docs/tpm-unlock.md
index 6a95ac7..653b099 100644
--- a/docs/tpm-unlock.md
+++ b/docs/tpm-unlock.md
@@ -185,10 +185,10 @@ is agreed. Stop if any command fails.
      /var/lib/dotfiles/tpm-nvpcr/stage/arch-linux-lts-fallback.efi
    ```
 
-   The check reads `.pcrpkey`, `.pcrsig`, and `.cmdline` using ukify, then
-   verifies each Secure Boot signature with the enrolled `sbctl` certificate.
-   Stop on any mismatch. The `systemd-pcrextend` socket and early setup units
-   must be present in both initramfs variants.
+   The check reads `.pcrpkey`, `.pcrsig`, and `.cmdline` using ukify. It uses
+   `lsinitcpio` to check the four required initrd units and verifies each
+   Secure Boot signature with the enrolled `sbctl` certificate. Stop on any
+   mismatch.
 
 7. Copy each checked image to the ESP under a temporary name, then rename it
    into place before copying the next one. This needs space for only one extra
diff --git a/scripts/tpm_nvpcr.py b/scripts/tpm_nvpcr.py
index 4f0f0a7..14a250c 100644
--- a/scripts/tpm_nvpcr.py
+++ b/scripts/tpm_nvpcr.py
@@ -21,6 +21,12 @@ MEASUREMENT_OPTIONS = (
     "tpm2-measure-pcr=15",
     "tpm2-measure-keyslot-nvpcr=cryptsetup",
 )
+INITRD_UNITS = (
+    "systemd-tpm2-setup-early.service",
+    "systemd-pcrnvdone.service",
+    "systemd-pcrextend.socket",
+    "systemd-pcrextend@.service",
+)
 
 
 def run(*command: str) -> str:
@@ -69,6 +75,13 @@ def check_sections(sections: dict, public_key: bytes) -> None:
         raise ValueError("Root measurement or TPM unlock option is missing")
 
 
+def check_initrd_listing(listing: str) -> None:
+    members = {line.strip().lstrip("./") for line in listing.splitlines()}
+    for unit in INITRD_UNITS:
+        if f"usr/lib/systemd/system/{unit}" not in members:
+            raise ValueError(f"UKI initrd lacks {unit}")
+
+
 def check_image(path: Path, public_key: bytes) -> None:
     sections = json.loads(
         run(
@@ -84,6 +97,7 @@ def check_image(path: Path, public_key: bytes) -> None:
     if not isinstance(sections, dict) or "_profiles" in sections:
         raise ValueError(f"Unsupported multi-profile UKI: {path}")
     check_sections(sections, public_key)
+    check_initrd_listing(run("lsinitcpio", "--list", str(path)))
     run("sbverify", "--cert", str(SB_CERT), str(path))
     print(f"verified: {path}")
 
diff --git a/tests/test_nvpcr.py b/tests/test_nvpcr.py
index f5765e4..5f36bb7 100644
--- a/tests/test_nvpcr.py
+++ b/tests/test_nvpcr.py
@@ -83,6 +83,21 @@ def sections(public_key, *, policies=None, options=None):
 
 
 class NvPCRImageTests(unittest.TestCase):
+    def test_initrd_has_required_units(self):
+        listing = "\n".join(
+            f"usr/lib/systemd/system/{unit}" for unit in tpm_nvpcr.INITRD_UNITS
+        )
+        tpm_nvpcr.check_initrd_listing(listing)
+
+    def test_rejects_missing_initrd_service(self):
+        listing = "\n".join(
+            f"usr/lib/systemd/system/{unit}"
+            for unit in tpm_nvpcr.INITRD_UNITS
+            if unit != "systemd-pcrnvdone.service"
+        )
+        with self.assertRaisesRegex(ValueError, "systemd-pcrnvdone.service"):
+            tpm_nvpcr.check_initrd_listing(listing)
+
     def test_valid_initrd_signature_and_root_options(self):
         tpm_nvpcr.check_sections(sections(b"public key"), b"public key")