[EventHub][ServiceBus] Fix pyAMQP decode of performatives with omitted trailing null fields

sdk/eventhub/azure-eventhub/CHANGELOG.md

@@ -1,5 +1,11 @@
 # Release History
 
+## 5.15.2 (Unreleased)
+
+### Bugs Fixed
+
+- Fixed a bug in the pyAMQP transport where decoding an incoming performative whose trailing null fields were omitted by the sender (permitted by AMQP 1.0 section 1.4) raised `IndexError`/`TypeError`. The decoded field list is now padded to the performative's full field count so omitted trailing fields read back as `None`.
+
 ## 5.15.1 (2025-11-11)
 
 ### Bugs Fixed

sdk/eventhub/azure-eventhub/azure/eventhub/_pyamqp/_decode.py

@@ -23,6 +23,7 @@
 
 
 from .message import Message, Header, Properties
+from . import performatives
 
 if TYPE_CHECKING:
     from .message import MessageDict
@@ -327,6 +328,36 @@ def decode_payload(buffer: memoryview) -> Message:
     return Message(**message_properties)
 
 
+# Number of fields encoded on the wire for each performative, keyed by its
+# frame-type code. The AMQP 1.0 spec (section 1.4) lets a sender omit trailing
+# null fields, so an incoming performative list can be shorter than the full
+# field count. Padding the decoded list up to this count keeps positional
+# (frame[N]) access and namedtuple unpacking safe; the missing trailing fields
+# read back as None, which is the spec-defined meaning of an omitted field.
+# The transfer performative (code 20) carries a trailing payload that is not a
+# wire field, so its _definition uses a None sentinel for that slot, which is
+# excluded from the count here.
+_PERFORMATIVE_FIELD_COUNT: Dict[int, int] = {
+    performative._code: sum(1 for field in performative._definition if field is not None)
+    for performative in (
+        performatives.OpenFrame,
+        performatives.BeginFrame,
+        performatives.AttachFrame,
+        performatives.FlowFrame,
+        performatives.TransferFrame,
+        performatives.DispositionFrame,
+        performatives.DetachFrame,
+        performatives.EndFrame,
+        performatives.CloseFrame,
+        performatives.SASLMechanism,
+        performatives.SASLInit,
+        performatives.SASLChallenge,
+        performatives.SASLResponse,
+        performatives.SASLOutcome,
+    )
+}
+
+
 def decode_frame(data: memoryview) -> Tuple[int, List[Any]]:
     # Ignore the first two bytes, they will always be the constructors for
     # described type then ulong.
@@ -343,6 +374,11 @@ def decode_frame(data: memoryview) -> Tuple[int, List[Any]]:
     fields: List[Optional[memoryview]] = [None] * count
     for i in range(count):
         buffer, fields[i] = _DECODE_BY_CONSTRUCTOR[buffer[0]](buffer[1:])
+    # A sender may omit trailing null fields, so pad the decoded list up to the
+    # performative's full field count before any positional access or unpacking.
+    full_field_count = _PERFORMATIVE_FIELD_COUNT.get(frame_type)
+    if full_field_count is not None and count < full_field_count:
+        fields.extend([None] * (full_field_count - count))
     if frame_type == 20:
         fields.append(buffer)
     return frame_type, fields

sdk/eventhub/azure-eventhub/azure/eventhub/_version.py

@@ -3,4 +3,4 @@
 # Licensed under the MIT License.
 # ------------------------------------
 
-VERSION = "5.15.1"
+VERSION = "5.15.2"

sdk/eventhub/azure-eventhub/tests/pyamqp_tests/unittest/test_decode.py

@@ -1,5 +1,6 @@
 import pytest
-from azure.eventhub._pyamqp._decode import _decode_decimal128
+from azure.eventhub._pyamqp._decode import _decode_decimal128, decode_frame, _PERFORMATIVE_FIELD_COUNT
+from azure.eventhub._pyamqp import performatives
 from decimal import Decimal
 
 
@@ -18,3 +19,62 @@ def test_decimal_decode(value, expected):
     assert output[1] == expected
 
 
+def _list8_frame(code, count, encoded_fields, payload=b""):
+    # Build a described performative frame using a list8 (0xc0) body:
+    # described-type ctor (0x00), ulong ctor (0x53), descriptor code, list8 (0xc0),
+    # size, count, then the encoded field bytes and any trailing payload.
+    header = bytes([0x00, 0x53, code, 0xC0, len(encoded_fields) + 1, count])
+    return memoryview(header + encoded_fields + payload)
+
+
+# A sender may omit trailing null fields (AMQP 1.0 section 1.4), so an incoming
+# performative list can be shorter than the full field count. The decoder must
+# pad it back to the full count so positional access and namedtuple unpacking
+# stay safe and omitted fields read back as None.
+def test_short_open_is_padded_to_full_field_count():
+    # Open with only container_id set ("x"), 1 field on the wire out of 10.
+    frame = _list8_frame(performatives.OpenFrame._code, 1, bytes([0xA1, 0x01, 0x78]))
+    frame_type, fields = decode_frame(frame)
+    assert frame_type == performatives.OpenFrame._code
+    assert len(fields) == 10
+    # Unpacking and fixed-index access must not raise on the omitted fields.
+    open_frame = performatives.OpenFrame(*fields)
+    assert open_frame.container_id == b"x"
+    assert open_frame.properties is None
+    assert fields[9] is None
+
+
+def test_short_transfer_pads_fields_and_preserves_payload():
+    # Transfer with only handle (0) set, plus a message payload. The payload is
+    # appended after the fields and must survive the padding.
+    frame = _list8_frame(performatives.TransferFrame._code, 1, bytes([0x52, 0x00]), payload=b"\xde\xad")
+    frame_type, fields = decode_frame(frame)
+    assert frame_type == performatives.TransferFrame._code
+    # 11 wire fields padded out, then the trailing payload appended (12 total).
+    assert len(fields) == 12
+    transfer = performatives.TransferFrame(*fields)
+    assert transfer.handle == 0
+    assert transfer.batchable is None
+    assert bytes(transfer.payload) == b"\xde\xad"
+
+
+@pytest.mark.parametrize(
+    "frame_cls,expected_count",
+    [
+        (performatives.OpenFrame, 10),
+        (performatives.BeginFrame, 8),
+        (performatives.AttachFrame, 14),
+        (performatives.FlowFrame, 11),
+        (performatives.TransferFrame, 11),
+        (performatives.DispositionFrame, 6),
+        (performatives.DetachFrame, 3),
+        (performatives.EndFrame, 1),
+        (performatives.CloseFrame, 1),
+    ],
+)
+def test_performative_field_count_matches_spec(frame_cls, expected_count):
+    # The padding target is the number of wire fields defined for each
+    # performative (the trailing transfer payload slot is excluded).
+    assert _PERFORMATIVE_FIELD_COUNT[frame_cls._code] == expected_count
+
+

sdk/servicebus/azure-servicebus/CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Bugs Fixed
 
 - Read `com.microsoft:max-message-batch-size` vendor property from the AMQP sender link to correctly limit batch size on Premium large-message entities, where `max-message-size` can be up to 100 MB but the batch limit is 1 MB.
+- Fixed a bug in the pyAMQP transport where decoding an incoming performative whose trailing null fields were omitted by the sender (permitted by AMQP 1.0 section 1.4) raised `IndexError`/`TypeError`. The decoded field list is now padded to the performative's full field count so omitted trailing fields read back as `None`.
 
 ## 7.14.3 (2025-11-11)
 

sdk/servicebus/azure-servicebus/azure/servicebus/_pyamqp/_decode.py

@@ -23,6 +23,7 @@
 
 
 from .message import Message, Header, Properties
+from . import performatives
 
 if TYPE_CHECKING:
     from .message import MessageDict
@@ -327,6 +328,36 @@ def decode_payload(buffer: memoryview) -> Message:
     return Message(**message_properties)
 
 
+# Number of fields encoded on the wire for each performative, keyed by its
+# frame-type code. The AMQP 1.0 spec (section 1.4) lets a sender omit trailing
+# null fields, so an incoming performative list can be shorter than the full
+# field count. Padding the decoded list up to this count keeps positional
+# (frame[N]) access and namedtuple unpacking safe; the missing trailing fields
+# read back as None, which is the spec-defined meaning of an omitted field.
+# The transfer performative (code 20) carries a trailing payload that is not a
+# wire field, so its _definition uses a None sentinel for that slot, which is
+# excluded from the count here.
+_PERFORMATIVE_FIELD_COUNT: Dict[int, int] = {
+    performative._code: sum(1 for field in performative._definition if field is not None)
+    for performative in (
+        performatives.OpenFrame,
+        performatives.BeginFrame,
+        performatives.AttachFrame,
+        performatives.FlowFrame,
+        performatives.TransferFrame,
+        performatives.DispositionFrame,
+        performatives.DetachFrame,
+        performatives.EndFrame,
+        performatives.CloseFrame,
+        performatives.SASLMechanism,
+        performatives.SASLInit,
+        performatives.SASLChallenge,
+        performatives.SASLResponse,
+        performatives.SASLOutcome,
+    )
+}
+
+
 def decode_frame(data: memoryview) -> Tuple[int, List[Any]]:
     # Ignore the first two bytes, they will always be the constructors for
     # described type then ulong.
@@ -343,6 +374,11 @@ def decode_frame(data: memoryview) -> Tuple[int, List[Any]]:
     fields: List[Optional[memoryview]] = [None] * count
     for i in range(count):
         buffer, fields[i] = _DECODE_BY_CONSTRUCTOR[buffer[0]](buffer[1:])
+    # A sender may omit trailing null fields, so pad the decoded list up to the
+    # performative's full field count before any positional access or unpacking.
+    full_field_count = _PERFORMATIVE_FIELD_COUNT.get(frame_type)
+    if full_field_count is not None and count < full_field_count:
+        fields.extend([None] * (full_field_count - count))
     if frame_type == 20:
         fields.append(buffer)
     return frame_type, fields

sdk/servicebus/azure-servicebus/tests/unittests/test_pyamqp_decode.py

@@ -0,0 +1,62 @@
+import pytest
+from azure.servicebus._pyamqp._decode import decode_frame, _PERFORMATIVE_FIELD_COUNT
+from azure.servicebus._pyamqp import performatives
+
+
+def _list8_frame(code, count, encoded_fields, payload=b""):
+    # Build a described performative frame using a list8 (0xc0) body:
+    # described-type ctor (0x00), ulong ctor (0x53), descriptor code, list8 (0xc0),
+    # size, count, then the encoded field bytes and any trailing payload.
+    header = bytes([0x00, 0x53, code, 0xC0, len(encoded_fields) + 1, count])
+    return memoryview(header + encoded_fields + payload)
+
+
+# A sender may omit trailing null fields (AMQP 1.0 section 1.4), so an incoming
+# performative list can be shorter than the full field count. The decoder must
+# pad it back to the full count so positional access and namedtuple unpacking
+# stay safe and omitted fields read back as None.
+def test_short_open_is_padded_to_full_field_count():
+    # Open with only container_id set ("x"), 1 field on the wire out of 10.
+    frame = _list8_frame(performatives.OpenFrame._code, 1, bytes([0xA1, 0x01, 0x78]))
+    frame_type, fields = decode_frame(frame)
+    assert frame_type == performatives.OpenFrame._code
+    assert len(fields) == 10
+    # Unpacking and fixed-index access must not raise on the omitted fields.
+    open_frame = performatives.OpenFrame(*fields)
+    assert open_frame.container_id == b"x"
+    assert open_frame.properties is None
+    assert fields[9] is None
+
+
+def test_short_transfer_pads_fields_and_preserves_payload():
+    # Transfer with only handle (0) set, plus a message payload. The payload is
+    # appended after the fields and must survive the padding.
+    frame = _list8_frame(performatives.TransferFrame._code, 1, bytes([0x52, 0x00]), payload=b"\xde\xad")
+    frame_type, fields = decode_frame(frame)
+    assert frame_type == performatives.TransferFrame._code
+    # 11 wire fields padded out, then the trailing payload appended (12 total).
+    assert len(fields) == 12
+    transfer = performatives.TransferFrame(*fields)
+    assert transfer.handle == 0
+    assert transfer.batchable is None
+    assert bytes(transfer.payload) == b"\xde\xad"
+
+
+@pytest.mark.parametrize(
+    "frame_cls,expected_count",
+    [
+        (performatives.OpenFrame, 10),
+        (performatives.BeginFrame, 8),
+        (performatives.AttachFrame, 14),
+        (performatives.FlowFrame, 11),
+        (performatives.TransferFrame, 11),
+        (performatives.DispositionFrame, 6),
+        (performatives.DetachFrame, 3),
+        (performatives.EndFrame, 1),
+        (performatives.CloseFrame, 1),
+    ],
+)
+def test_performative_field_count_matches_spec(frame_cls, expected_count):
+    # The padding target is the number of wire fields defined for each
+    # performative (the trailing transfer payload slot is excluded).
+    assert _PERFORMATIVE_FIELD_COUNT[frame_cls._code] == expected_count