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ukify: Support multiple PCR signing keys to sign phases separately #4279

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148 changes: 95 additions & 53 deletions mkosi/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,7 @@
ManifestFormat,
Network,
OutputFormat,
PcrSigner,
SecureBootSignTool,
ShimBootloader,
Ssh,
Expand Down Expand Up @@ -1583,8 +1584,10 @@ def want_signed_pcrs(config: Config) -> bool:
return config.sign_expected_pcr == ConfigFeature.enabled or (
config.sign_expected_pcr == ConfigFeature.auto
and config.find_binary("systemd-measure", "/usr/lib/systemd/systemd-measure") is not None
and bool(config.sign_expected_pcr_key)
and bool(config.sign_expected_pcr_certificate)
and (
(bool(config.sign_expected_pcr_key) and bool(config.sign_expected_pcr_certificate))
or bool(config.sign_expected_pcr_with_phases)
)
)


Expand Down Expand Up @@ -1755,73 +1758,98 @@ def build_uki(

arguments += ["--sign-kernel"]

if want_signed_pcrs(context.config):
assert context.config.sign_expected_pcr_key
assert context.config.sign_expected_pcr_certificate
seen_bind_paths: set[Path] = set()

if want_signed_pcrs(context.config):
arguments += [
# SHA1 might be disabled in OpenSSL depending on the distro so we opt to not sign
# for SHA1 to avoid having to manage a bunch of configuration to re-enable SHA1.
"--pcr-banks", "sha256",
] # fmt: skip

if (
systemd_tool_version(
python_binary(context.config),
ukify,
sandbox=context.sandbox,
)
>= "258"
):
ukify_version = systemd_tool_version(
python_binary(context.config),
ukify,
sandbox=context.sandbox,
)

if ukify_version >= "258":
cert_parameter = "--pcr-certificate"
else:
cert_parameter = "--pcr-public-key"

# If we're providing the private key via an engine or provider, we have to pass in a X.509
# certificate via --pcr-certificate as well.
if context.config.sign_expected_pcr_key_source.type != KeySourceType.file:
if context.config.sign_expected_pcr_certificate_source.type == CertificateSourceType.provider:
arguments += [
"--certificate-provider",
f"provider:{context.config.sign_expected_pcr_certificate_source.source}",
]
if context.config.sign_expected_pcr_with_phases:
signers = context.config.sign_expected_pcr_with_phases
if ukify_version < "253":
die(f"ukify {ukify_version} does not support --phases (need >= 253)")
else:
assert context.config.sign_expected_pcr_key
assert context.config.sign_expected_pcr_certificate
signers = [
PcrSigner(
key=context.config.sign_expected_pcr_key,
certificate=context.config.sign_expected_pcr_certificate,
phases=[],
key_source=context.config.sign_expected_pcr_key_source,
certificate_source=context.config.sign_expected_pcr_certificate_source,
)
]

options += ["--bind", "/run", "/run"]
need_run_bind = False

if context.config.sign_expected_pcr_certificate.exists():
arguments += [
cert_parameter, workdir(context.config.sign_expected_pcr_certificate),
] # fmt: skip
options += [
"--ro-bind", context.config.sign_expected_pcr_certificate, workdir(context.config.sign_expected_pcr_certificate), # noqa: E501
] # fmt: skip
for signer in signers:
# If we're providing the private key via an engine or provider, we have to pass in
# a X.509 certificate via --pcr-certificate as well.
if signer.key_source.type != KeySourceType.file:
if signer.certificate_source.type == CertificateSourceType.provider:
arguments += [
"--certificate-provider", f"provider:{signer.certificate_source.source}",
] # fmt: skip

need_run_bind = True

if signer.certificate.exists():
arguments += [cert_parameter, workdir(signer.certificate)]
seen_bind_paths.add(signer.certificate)
else:
arguments += [cert_parameter, signer.certificate]

if signer.key_source.type == KeySourceType.engine:
arguments += ["--signing-engine", signer.key_source.source]
Comment on lines +1817 to +1818

@github-actions github-actions Bot May 22, 2026

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Claude: suggestion: Claude: When multiple signers have non-file key sources, --signing-engine/--signing-provider is emitted once per signer in the loop. Since ukify uses a single global engine/provider, passing it multiple times is redundant at best. More importantly, if different signers specify inconsistent key source types (e.g., one uses engine:pkcs11 and another uses provider:pkcs11), this would produce conflicting --signing-engine and --signing-provider arguments on the same ukify command line with no early validation error from mkosi.

The documentation notes that "it is the user's responsibility to keep sources consistent across signers," but a validation check in validate_pcr_signing (similar to the existing secure_boot_key_source consistency check) would catch misconfigurations early with a clear error message. Alternatively, emitting --signing-engine/--signing-provider only once (outside or after the loop) would make the "global" nature explicit in code.

elif signer.key_source.type == KeySourceType.provider:
arguments += ["--signing-provider", signer.key_source.source]

if signer.key.exists():
arguments += ["--pcr-private-key", workdir(signer.key)]
seen_bind_paths.add(signer.key)
else:
arguments += [cert_parameter, context.config.sign_expected_pcr_certificate]
arguments += ["--pcr-private-key", signer.key]

if context.config.sign_expected_pcr_key_source.type == KeySourceType.engine:
arguments += ["--signing-engine", context.config.sign_expected_pcr_key_source.source]
elif context.config.sign_expected_pcr_key_source.type == KeySourceType.provider:
arguments += ["--signing-provider", context.config.sign_expected_pcr_key_source.source]
if signer.phases:
arguments += ["--phases", " ".join(signer.phases)]

if context.config.sign_expected_pcr_key.exists():
arguments += ["--pcr-private-key", workdir(context.config.sign_expected_pcr_key)]
options += [
"--ro-bind", context.config.sign_expected_pcr_key, workdir(context.config.sign_expected_pcr_key), # noqa: E501
] # fmt: skip
else:
arguments += ["--pcr-private-key", context.config.sign_expected_pcr_key]
if need_run_bind:
options += ["--bind", "/run", "/run"]
elif ArtifactOutput.pcrs in context.config.split_artifacts:
assert context.config.sign_expected_pcr_certificate

json_out = True
cert = context.config.sign_expected_pcr_certificate
arguments += [
"--policy-digest",
"--pcr-banks", "sha256",
"--pcr-certificate", workdir(context.config.sign_expected_pcr_certificate),
] # fmt: skip
options += [
"--ro-bind", context.config.sign_expected_pcr_certificate, workdir(context.config.sign_expected_pcr_certificate), # noqa: E501
"--pcr-certificate", workdir(cert),
] # fmt: skip
seen_bind_paths.add(cert)

if (pcrpkey := context.config.sign_expected_pcr_uki_public_key) is not None:
if not pcrpkey.exists():
die(f"SignExpectedPcrUKIPublicKey={pcrpkey} does not exist")
arguments += ["--pcrpkey", workdir(pcrpkey)]
seen_bind_paths.add(pcrpkey)

for file in seen_bind_paths:
options += ["--ro-bind", file, workdir(file)]

if microcodes:
# new .ucode section support?
Expand Down Expand Up @@ -2723,25 +2751,39 @@ def check_inputs(config: Config) -> None:
hint="Run mkosi genkey to generate a key/certificate pair",
)

if config.sign_expected_pcr == ConfigFeature.enabled and not config.sign_expected_pcr_key:
if (
config.sign_expected_pcr == ConfigFeature.enabled
and not config.sign_expected_pcr_with_phases
and not config.sign_expected_pcr_key
):
die(
"SignExpectedPcr= is enabled but no private key is configured",
hint="Run mkosi genkey to generate a key/certificate pair",
)

if config.sign_expected_pcr == ConfigFeature.enabled and not config.sign_expected_pcr_certificate:
if (
config.sign_expected_pcr == ConfigFeature.enabled
and not config.sign_expected_pcr_with_phases
and not config.sign_expected_pcr_certificate
):
die(
"SignExpectedPcr= is enabled but no certificate is configured",
hint="Run mkosi genkey to generate a key/certificate pair",
)

if config.secure_boot_key_source != config.sign_expected_pcr_key_source:
die("Secure boot key source and expected PCR signatures key source have to be the same")
# When SignExpectedPcrWithPhases= is used the key/certificate sources live per-entry, so the
# scalar sign_expected_pcr_{key,certificate}_source fields default to "file" regardless of
# what the per-signer sources are. Comparing those scalars against secure boot's sources
# would be meaningless, so skip the check in that case and rely on ukify to reject
# inconsistent sources at invocation time.
if not config.sign_expected_pcr_with_phases:
if config.secure_boot_key_source != config.sign_expected_pcr_key_source:
die("Secure boot key source and expected PCR signatures key source have to be the same")

if config.secure_boot_certificate_source != config.sign_expected_pcr_certificate_source:
die(
"Secure boot certificate source and expected PCR signatures certificate source have to be the same" # noqa: E501
) # fmt: skip
if config.secure_boot_certificate_source != config.sign_expected_pcr_certificate_source:
die(
"Secure boot certificate source and expected PCR signatures certificate source have to be the same" # noqa: E501
) # fmt: skip

if config.verity == Verity.signed and not config.verity_key:
die(
Expand Down
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