1 files changed, 114 insertions, 0 deletions
diff --git a/tests/pytests/test_prefix.py b/tests/pytests/test_prefix.py
new file mode 100644
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+++ b/tests/pytests/test_prefix.py
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+# SPDX-License-Identifier: GPL-3.0-or-later
+"""TCP Connection Management tests - prefix length
+
+RFC1035
+4.2.2. TCP usage
+The message is prefixed with a two byte length field which gives the message
+length, excluding the two byte length field.
+
+The following test suite focuses on edge cases for the prefix - when it
+is either too short or too long, instead of matching the length of DNS
+message exactly.
+"""
+
+import time
+
+import pytest
+
+import utils
+
+
+@pytest.fixture(params=[
+    'no_query_before',
+    'query_before',
+    'query_before_in_single_buffer',
+])
+def send_query(request):
+    """Function sends a buffer, either by itself, or with a valid query before.
+    If a valid query is sent before, it can be sent either in a separate buffer, or
+    along with the provided buffer."""
+
+    # pylint: disable=possibly-unused-variable
+
+    def no_query_before(sock, buff):  # pylint: disable=unused-argument
+        sock.sendall(buff)
+
+    def query_before(sock, buff, single_buffer=False):
+        """Send an initial query and expect a response."""
+        msg_buff, msgid = utils.get_msgbuff()
+
+        if single_buffer:
+            sock.sendall(msg_buff + buff)
+        else:
+            sock.sendall(msg_buff)
+            sock.sendall(buff)
+
+        answer = utils.receive_parse_answer(sock)
+        assert answer.id == msgid
+
+    def query_before_in_single_buffer(sock, buff):
+        return query_before(sock, buff, single_buffer=True)
+
+    return locals()[request.param]
+
+
+@pytest.mark.parametrize('datalen', [
+  1,   # just one byte of DNS header
+  11,  # DNS header size minus 1
+  14,  # DNS Header size plus 2
+])
+def test_prefix_cuts_message(kresd_sock, datalen, send_query):
+    """Prefix is shorter than the DNS message."""
+    wire, _ = utils.prepare_wire()
+    assert datalen < len(wire)
+    invalid_buff = utils.prepare_buffer(wire, datalen)
+
+    send_query(kresd_sock, invalid_buff)  # buffer breaks parsing of TCP stream
+
+    with utils.expect_kresd_close():
+        utils.ping_alive(kresd_sock)
+
+
+def test_prefix_greater_than_message(kresd_sock, send_query):
+    """Prefix is greater than the length of the entire DNS message."""
+    wire, invalid_msgid = utils.prepare_wire()
+    datalen = len(wire) + 16
+    invalid_buff = utils.prepare_buffer(wire, datalen)
+
+    send_query(kresd_sock, invalid_buff)
+
+    valid_buff, _ = utils.get_msgbuff()
+    kresd_sock.sendall(valid_buff)
+
+    # invalid_buff is answered (treats additional data as trailing garbage)
+    answer = utils.receive_parse_answer(kresd_sock)
+    assert answer.id == invalid_msgid
+
+    # parsing stream is broken by the invalid_buff, valid query is never answered
+    with utils.expect_kresd_close():
+        utils.receive_parse_answer(kresd_sock)
+
+
+@pytest.mark.parametrize('glength', [
+    0,
+    1,
+    8,
+    1024,
+    4096,
+    20000,
+])
+def test_prefix_trailing_garbage(kresd_sock, glength, query_before):
+    """Send messages with trailing garbage (its length included in prefix)."""
+    if query_before:
+        utils.ping_alive(kresd_sock)
+
+    for _ in range(10):
+        wire, msgid = utils.prepare_wire()
+        wire += utils.get_garbage(glength)
+        buff = utils.prepare_buffer(wire)
+
+        kresd_sock.sendall(buff)
+        answer = utils.receive_parse_answer(kresd_sock)
+        assert answer.id == msgid
+
+        time.sleep(0.1)