fix(attestation): Azure attestation reports never pass verification

python/src/agent_manifest/_attestation.py

@@ -233,18 +233,36 @@ def verify_attestation_chain(
         cannot pass, because an unverified report proves nothing.
     """
     reasons: list[str] = []
+    platform = getattr(report, "platform", "") or ""
 
     # Step 3: manifest-hash binding (software-checkable).
-    expected_digest = expected_manifest_hash.split(":", 1)[-1].lower()
-    actual_hex = _report_data_hex(report)
-    if actual_hex is None:
-        report_data_matched = False
-        reasons.append("report has no 'report_data' field to check the manifest binding against")
+    #
+    # Does not apply on Azure: the guest never controls REPORT_DATA there (the
+    # paravisor sets it to sha256(runtime_data) to bind the vTPM AK, not the
+    # manifest hash - see the module docstring and LIMITATIONS.md). Manifest
+    # binding on Azure is checked separately, via
+    # AzureCVMProvider.verify_manifest_in_report(). Treating this field as
+    # authoritative there would mean `passed` could never be True for a
+    # genuine Azure report, no matter how correct everything else is.
+    azure_paravisor = platform == "azure-cvm-sev-snp"
+    if azure_paravisor:
+        report_data_matched = True
+        reasons.append(
+            "report_data binding not applicable on Azure (REPORT_DATA is "
+            "sha256(runtime_data), not the manifest hash); manifest binding "
+            "is checked via AzureCVMProvider.verify_manifest_in_report()"
+        )
     else:
-        # The first 32 bytes (64 hex chars) of REPORT_DATA carry the digest.
-        report_data_matched = hmac.compare_digest(actual_hex[:64].lower(), expected_digest)
-        if not report_data_matched:
-            reasons.append("manifest hash does not match the report_data binding")
+        expected_digest = expected_manifest_hash.split(":", 1)[-1].lower()
+        actual_hex = _report_data_hex(report)
+        if actual_hex is None:
+            report_data_matched = False
+            reasons.append("report has no 'report_data' field to check the manifest binding against")
+        else:
+            # The first 32 bytes (64 hex chars) of REPORT_DATA carry the digest.
+            report_data_matched = hmac.compare_digest(actual_hex[:64].lower(), expected_digest)
+            if not report_data_matched:
+                reasons.append("manifest hash does not match the report_data binding")
 
     # Step 2: launch-measurement allow-list (software-checkable, optional).
     measurement_matched: Optional[bool]
@@ -266,7 +284,6 @@ def verify_attestation_chain(
     # VCEK material). Intel TDX verifies the self-contained DCAP quote + PCK chain
     # to the pinned Intel SGX Root CA. Either way, without a verifiable signature
     # the result cannot pass.
-    platform = getattr(report, "platform", "") or ""
     if platform == "intel-tdx":
         signature = _verify_tdx_signature_step(report, reasons, trusted_tdx_root_pem)
     elif platform in ("tpm", "aws-nitro"):

python/tests/test_attestation_chain.py

@@ -239,3 +239,54 @@ def test_full_chain_reads_snp_bytes_from_report_quote():
     )
     assert result.signature is SignatureStatus.VERIFIED
     assert result.passed is True
+
+
+# ---------------------------------------------------------------------------
+# Azure paravisor SNP: REPORT_DATA is sha256(runtime_data), never the manifest
+# hash (the guest does not control it - see LIMITATIONS.md). Manifest binding
+# is checked separately via AzureCVMProvider.verify_manifest_in_report(), so
+# this function must not gate `passed` on report_data for azure-cvm-sev-snp.
+# ---------------------------------------------------------------------------
+
+
+def test_azure_report_passes_despite_report_data_not_carrying_manifest_hash():
+    # report_data here is sha256(runtime_data) - by construction NOT equal to
+    # the manifest digest. A genuine Azure report always looks like this.
+    runtime_data_hash = hashlib.sha256(b"azure-runtime-data").hexdigest()
+    snp, vcek_der, chain = _synthetic_snp_with_chain(runtime_data_hash, MEASUREMENT)
+    report = AttestationReport(
+        platform="azure-cvm-sev-snp",
+        manifest_hash=MANIFEST_HASH,
+        quote=snp,
+        raw={"report_data": runtime_data_hash + "00" * 32, "measurement": MEASUREMENT},
+    )
+    result = verify_attestation_chain(
+        report,
+        expected_manifest_hash=MANIFEST_HASH,
+        vcek_cert_der=vcek_der,
+        cert_chain_pem=chain,
+    )
+    assert result.signature is SignatureStatus.VERIFIED
+    assert result.report_data_matched is True
+    assert result.passed is True
+    assert any("not applicable on Azure" in r for r in result.reasons)
+
+
+def test_non_azure_snp_still_requires_report_data_to_match():
+    # Confirms the fix is scoped to azure-cvm-sev-snp: a direct-silicon SNP
+    # report (amd-sev-snp) must still bind REPORT_DATA to the manifest hash.
+    snp, vcek_der, chain = _synthetic_snp_with_chain(MEASUREMENT, MEASUREMENT)  # wrong digest
+    report = AttestationReport(
+        platform="amd-sev-snp",
+        manifest_hash=MANIFEST_HASH,
+        quote=snp,
+        raw={"report_data": MEASUREMENT + "00" * 16, "measurement": MEASUREMENT},
+    )
+    result = verify_attestation_chain(
+        report,
+        expected_manifest_hash=MANIFEST_HASH,
+        vcek_cert_der=vcek_der,
+        cert_chain_pem=chain,
+    )
+    assert result.report_data_matched is False
+    assert result.passed is False