fix: reject debug TDs unconditionally, validate QE vendor ID, fix urlencode import

Author: jdrean

src/tinfoil/attestation/abi_tdx.py

@@ -688,6 +688,12 @@ def _validate_header(header: TdxHeader) -> None:
             f"Invalid TEE type: 0x{header.tee_type:x}. Expected 0x{TEE_TDX:x} (TDX)."
         )
 
+    if header.qe_vendor_id != INTEL_QE_VENDOR_ID:
+        raise TdxQuoteParseError(
+            f"Unknown QE vendor ID: {header.qe_vendor_id.hex()}. "
+            f"Expected Intel QE: {INTEL_QE_VENDOR_ID.hex()}"
+        )
+
 
 def parse_quote(data: bytes) -> QuoteV4:
     """

src/tinfoil/attestation/attestation_tdx.py

@@ -278,7 +278,7 @@ def verify_tdx_attestation_v2(attestation_doc: str) -> Verification:
     try:
         result = verify_tdx_attestation(attestation_doc, is_compressed=True)
     except TdxAttestationError as e:
-        raise ValueError(f"TDX attestation verification failed: {e}")
+        raise ValueError(f"TDX attestation verification failed: {e}") from e
 
     measurement = Measurement(
         type=PredicateType.TDX_GUEST_V2,

src/tinfoil/attestation/validate_tdx.py

@@ -262,8 +262,9 @@ def validate_td_attributes(td_attributes: bytes) -> None:
     """
     Validate TD_ATTRIBUTES fixed bit constraints.
 
-    Note: DEBUG bit (bit 0) is enforced via exact byte matching of
-    EXPECTED_TD_ATTRIBUTES, not via a separate check here.
+    Per Intel DCAP spec Section 2.3.2: "Verify that all TD Under Debug
+    flags (i.e., the TDATTRIBUTES.TUD field in the TD Quote Body) are
+    set to zero."
 
     Args:
         td_attributes: 8-byte TD_ATTRIBUTES from quote
@@ -278,7 +279,13 @@ def validate_td_attributes(td_attributes: bytes) -> None:
 
     value = struct.unpack('<Q', td_attributes)[0]
 
-    # No FIXED1 bits to check for TD_ATTRIBUTES currently.
+    # Mandatory: reject debug TDs unconditionally.
+    # A debug TD has its memory visible to the host, defeating TDX
+    # confidentiality guarantees.
+    if value & TD_ATTRIBUTES_DEBUG_BIT:
+        raise TdxValidationError(
+            f"TD_ATTRIBUTES 0x{value:x}: DEBUG bit must not be set"
+        )
 
     # Check FIXED0 bits (only allowed bits may be set)
     if value & (~TD_ATTRIBUTES_FIXED0):

src/tinfoil/client.py

@@ -7,12 +7,12 @@
 import random
 from dataclasses import dataclass
 from typing import Dict, Optional
-from urllib.parse import urlparse
+from urllib.parse import urlparse, urlencode
 import cryptography.x509
 from cryptography.hazmat.primitives.serialization import PublicFormat, Encoding
 import hashlib
 
-from .attestation import fetch_attestation, PredicateType, TDX_TYPES
+from .attestation import fetch_attestation, TDX_TYPES
 from .attestation.attestation_tdx import verify_tdx_hardware
 from .github import fetch_latest_digest, fetch_attestation_bundle
 from .sigstore import verify_attestation, fetch_latest_hardware_measurements
@@ -248,7 +248,7 @@ def get_router_address(platform: Optional[str] = None) -> str:
     """
     routers_url = "https://atc.tinfoil.sh/routers"
     if platform:
-        routers_url += "?" + urllib.parse.urlencode({"platform": platform})
+        routers_url += "?" + urlencode({"platform": platform})
 
     try:
         with urllib.request.urlopen(routers_url, timeout=15) as response:

tests/test_validate_tdx.py

@@ -126,12 +126,11 @@ def test_expected_td_attributes_value_passes(self):
         """The expected TD_ATTRIBUTES value from Go passes validation."""
         validate_td_attributes(EXPECTED_TD_ATTRIBUTES)  # Should not raise
 
-    def test_debug_bit_allowed_by_fixed0(self):
-        """DEBUG bit is allowed by FIXED0 (validation happens via exact match)."""
-        # DEBUG bit is in FIXED0, so it passes fixed bit validation
-        # The actual DEBUG rejection happens via exact byte matching
+    def test_debug_bit_rejected_unconditionally(self):
+        """DEBUG bit is rejected unconditionally, even though it's in FIXED0."""
         td_attrs = struct.pack('<Q', TD_ATTRIBUTES_DEBUG_BIT)
-        validate_td_attributes(td_attrs)  # Should not raise (fixed bits allow it)
+        with pytest.raises(TdxValidationError, match="DEBUG bit must not be set"):
+            validate_td_attributes(td_attrs)
 
     def test_unauthorized_bits_rejected(self):
         """TD_ATTRIBUTES with bits outside FIXED0 mask is rejected."""