322 lines
12 KiB
Diff
322 lines
12 KiB
Diff
From f66e25b5f549acf66d1fb6ead13eb3cff7d09af3 Mon Sep 17 00:00:00 2001
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From: Bob Halley <halley@dnspython.org>
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Date: Fri, 9 Feb 2024 11:22:52 -0800
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Subject: [PATCH] Address DoS via the Tudoor mechanism (CVE-2023-29483) (#1044)
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---
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dns/asyncquery.py | 45 +++++++++++++------
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dns/nameserver.py | 2 +
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dns/query.py | 110 +++++++++++++++++++++++++++++-----------------
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3 files changed, 103 insertions(+), 54 deletions(-)
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diff --git a/dns/asyncquery.py b/dns/asyncquery.py
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index 35a355b..94cb241 100644
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--- a/dns/asyncquery.py
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+++ b/dns/asyncquery.py
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@@ -120,6 +120,8 @@ async def receive_udp(
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request_mac: Optional[bytes] = b"",
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ignore_trailing: bool = False,
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raise_on_truncation: bool = False,
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+ ignore_errors: bool = False,
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+ query: Optional[dns.message.Message] = None,
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) -> Any:
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"""Read a DNS message from a UDP socket.
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@@ -133,22 +135,30 @@ async def receive_udp(
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"""
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wire = b""
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- while 1:
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+ while True:
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(wire, from_address) = await sock.recvfrom(65535, _timeout(expiration))
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- if _matches_destination(
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+ if not _matches_destination(
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sock.family, from_address, destination, ignore_unexpected
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):
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- break
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- received_time = time.time()
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- r = dns.message.from_wire(
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- wire,
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- keyring=keyring,
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- request_mac=request_mac,
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- one_rr_per_rrset=one_rr_per_rrset,
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- ignore_trailing=ignore_trailing,
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- raise_on_truncation=raise_on_truncation,
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- )
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- return (r, received_time, from_address)
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+ continue
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+ received_time = time.time()
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+ try:
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+ r = dns.message.from_wire(
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+ wire,
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+ keyring=keyring,
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+ request_mac=request_mac,
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+ one_rr_per_rrset=one_rr_per_rrset,
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+ ignore_trailing=ignore_trailing,
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+ raise_on_truncation=raise_on_truncation,
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+ )
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+ except Exception:
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+ if ignore_errors:
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+ continue
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+ else:
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+ raise
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+ if ignore_errors and query is not None and not query.is_response(r):
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+ continue
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+ return (r, received_time, from_address)
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async def udp(
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@@ -164,6 +174,7 @@ async def udp(
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raise_on_truncation: bool = False,
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sock: Optional[dns.asyncbackend.DatagramSocket] = None,
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backend: Optional[dns.asyncbackend.Backend] = None,
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+ ignore_errors: bool = False,
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) -> dns.message.Message:
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"""Return the response obtained after sending a query via UDP.
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@@ -205,9 +216,13 @@ async def udp(
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q.mac,
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ignore_trailing,
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raise_on_truncation,
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+ ignore_errors,
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+ q,
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)
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r.time = received_time - begin_time
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- if not q.is_response(r):
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+ # We don't need to check q.is_response() if we are in ignore_errors mode
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+ # as receive_udp() will have checked it.
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+ if not (ignore_errors or q.is_response(r)):
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raise BadResponse
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return r
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@@ -225,6 +240,7 @@ async def udp_with_fallback(
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udp_sock: Optional[dns.asyncbackend.DatagramSocket] = None,
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tcp_sock: Optional[dns.asyncbackend.StreamSocket] = None,
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backend: Optional[dns.asyncbackend.Backend] = None,
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+ ignore_errors: bool = False,
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) -> Tuple[dns.message.Message, bool]:
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"""Return the response to the query, trying UDP first and falling back
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to TCP if UDP results in a truncated response.
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@@ -260,6 +276,7 @@ async def udp_with_fallback(
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True,
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udp_sock,
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backend,
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+ ignore_errors,
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)
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return (response, False)
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except dns.message.Truncated:
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diff --git a/dns/nameserver.py b/dns/nameserver.py
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index a1fb549..0c494c1 100644
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--- a/dns/nameserver.py
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+++ b/dns/nameserver.py
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@@ -115,6 +115,7 @@ class Do53Nameserver(AddressAndPortNameserver):
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raise_on_truncation=True,
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one_rr_per_rrset=one_rr_per_rrset,
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ignore_trailing=ignore_trailing,
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+ ignore_errors=True,
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)
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return response
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@@ -153,6 +154,7 @@ class Do53Nameserver(AddressAndPortNameserver):
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backend=backend,
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one_rr_per_rrset=one_rr_per_rrset,
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ignore_trailing=ignore_trailing,
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+ ignore_errors=True,
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)
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return response
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diff --git a/dns/query.py b/dns/query.py
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index d4bd6b9..bdd251e 100644
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--- a/dns/query.py
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+++ b/dns/query.py
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@@ -569,6 +569,8 @@ def receive_udp(
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request_mac: Optional[bytes] = b"",
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ignore_trailing: bool = False,
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raise_on_truncation: bool = False,
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+ ignore_errors: bool = False,
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+ query: Optional[dns.message.Message] = None,
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) -> Any:
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"""Read a DNS message from a UDP socket.
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@@ -609,28 +611,44 @@ def receive_udp(
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``(dns.message.Message, float, tuple)``
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tuple of the received message, the received time, and the address where
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the message arrived from.
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+
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+ *ignore_errors*, a ``bool``. If various format errors or response
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+ mismatches occur, ignore them and keep listening for a valid response.
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+ The default is ``False``.
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+
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+ *query*, a ``dns.message.Message`` or ``None``. If not ``None`` and
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+ *ignore_errors* is ``True``, check that the received message is a response
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+ to this query, and if not keep listening for a valid response.
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"""
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wire = b""
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while True:
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(wire, from_address) = _udp_recv(sock, 65535, expiration)
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- if _matches_destination(
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+ if not _matches_destination(
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sock.family, from_address, destination, ignore_unexpected
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):
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- break
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- received_time = time.time()
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- r = dns.message.from_wire(
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- wire,
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- keyring=keyring,
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- request_mac=request_mac,
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- one_rr_per_rrset=one_rr_per_rrset,
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- ignore_trailing=ignore_trailing,
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- raise_on_truncation=raise_on_truncation,
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- )
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- if destination:
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- return (r, received_time)
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- else:
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- return (r, received_time, from_address)
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+ continue
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+ received_time = time.time()
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+ try:
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+ r = dns.message.from_wire(
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+ wire,
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+ keyring=keyring,
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+ request_mac=request_mac,
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+ one_rr_per_rrset=one_rr_per_rrset,
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+ ignore_trailing=ignore_trailing,
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+ raise_on_truncation=raise_on_truncation,
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+ )
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+ except Exception:
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+ if ignore_errors:
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+ continue
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+ else:
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+ raise
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+ if ignore_errors and query is not None and not query.is_response(r):
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+ continue
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+ if destination:
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+ return (r, received_time)
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+ else:
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+ return (r, received_time, from_address)
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def udp(
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@@ -645,6 +663,7 @@ def udp(
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ignore_trailing: bool = False,
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raise_on_truncation: bool = False,
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sock: Optional[Any] = None,
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+ ignore_errors: bool = False,
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) -> dns.message.Message:
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"""Return the response obtained after sending a query via UDP.
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@@ -681,6 +700,10 @@ def udp(
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if a socket is provided, it must be a nonblocking datagram socket,
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and the *source* and *source_port* are ignored.
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+ *ignore_errors*, a ``bool``. If various format errors or response
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+ mismatches occur, ignore them and keep listening for a valid response.
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+ The default is ``False``.
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+
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Returns a ``dns.message.Message``.
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"""
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@@ -705,9 +728,13 @@ def udp(
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q.mac,
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ignore_trailing,
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raise_on_truncation,
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+ ignore_errors,
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+ q,
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)
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r.time = received_time - begin_time
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- if not q.is_response(r):
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+ # We don't need to check q.is_response() if we are in ignore_errors mode
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+ # as receive_udp() will have checked it.
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+ if not (ignore_errors or q.is_response(r)):
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raise BadResponse
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return r
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assert (
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@@ -727,48 +754,50 @@ def udp_with_fallback(
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ignore_trailing: bool = False,
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udp_sock: Optional[Any] = None,
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tcp_sock: Optional[Any] = None,
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+ ignore_errors: bool = False,
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) -> Tuple[dns.message.Message, bool]:
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"""Return the response to the query, trying UDP first and falling back
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to TCP if UDP results in a truncated response.
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*q*, a ``dns.message.Message``, the query to send
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- *where*, a ``str`` containing an IPv4 or IPv6 address, where
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- to send the message.
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+ *where*, a ``str`` containing an IPv4 or IPv6 address, where to send the message.
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- *timeout*, a ``float`` or ``None``, the number of seconds to wait before the
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- query times out. If ``None``, the default, wait forever.
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+ *timeout*, a ``float`` or ``None``, the number of seconds to wait before the query
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+ times out. If ``None``, the default, wait forever.
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*port*, an ``int``, the port send the message to. The default is 53.
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- *source*, a ``str`` containing an IPv4 or IPv6 address, specifying
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- the source address. The default is the wildcard address.
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+ *source*, a ``str`` containing an IPv4 or IPv6 address, specifying the source
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+ address. The default is the wildcard address.
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- *source_port*, an ``int``, the port from which to send the message.
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- The default is 0.
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+ *source_port*, an ``int``, the port from which to send the message. The default is
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+ 0.
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- *ignore_unexpected*, a ``bool``. If ``True``, ignore responses from
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- unexpected sources.
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+ *ignore_unexpected*, a ``bool``. If ``True``, ignore responses from unexpected
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+ sources.
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- *one_rr_per_rrset*, a ``bool``. If ``True``, put each RR into its own
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- RRset.
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+ *one_rr_per_rrset*, a ``bool``. If ``True``, put each RR into its own RRset.
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- *ignore_trailing*, a ``bool``. If ``True``, ignore trailing
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- junk at end of the received message.
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+ *ignore_trailing*, a ``bool``. If ``True``, ignore trailing junk at end of the
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+ received message.
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- *udp_sock*, a ``socket.socket``, or ``None``, the socket to use for the
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- UDP query. If ``None``, the default, a socket is created. Note that
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- if a socket is provided, it must be a nonblocking datagram socket,
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- and the *source* and *source_port* are ignored for the UDP query.
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+ *udp_sock*, a ``socket.socket``, or ``None``, the socket to use for the UDP query.
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+ If ``None``, the default, a socket is created. Note that if a socket is provided,
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+ it must be a nonblocking datagram socket, and the *source* and *source_port* are
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+ ignored for the UDP query.
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*tcp_sock*, a ``socket.socket``, or ``None``, the connected socket to use for the
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- TCP query. If ``None``, the default, a socket is created. Note that
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- if a socket is provided, it must be a nonblocking connected stream
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- socket, and *where*, *source* and *source_port* are ignored for the TCP
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- query.
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+ TCP query. If ``None``, the default, a socket is created. Note that if a socket is
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+ provided, it must be a nonblocking connected stream socket, and *where*, *source*
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+ and *source_port* are ignored for the TCP query.
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+
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+ *ignore_errors*, a ``bool``. If various format errors or response mismatches occur
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+ while listening for UDP, ignore them and keep listening for a valid response. The
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+ default is ``False``.
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- Returns a (``dns.message.Message``, tcp) tuple where tcp is ``True``
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- if and only if TCP was used.
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+ Returns a (``dns.message.Message``, tcp) tuple where tcp is ``True`` if and only if
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+ TCP was used.
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"""
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try:
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response = udp(
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@@ -783,6 +812,7 @@ def udp_with_fallback(
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ignore_trailing,
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True,
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udp_sock,
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+ ignore_errors,
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)
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return (response, False)
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except dns.message.Truncated:
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--
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2.39.1
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