Make cancel request keys longer

Currently, the cancel request key is a 32-bit token, which isn't very
much entropy. If you want to cancel another session's query, you can
brute-force it. In most environments, an unauthorized cancellation of
a query isn't very serious, but it nevertheless would be nice to have
more protection from it. Hence make the key longer, to make it harder
to guess.

The longer cancellation keys are generated when using the new protocol
version 3.2. For connections using version 3.0, short 4-bytes keys are
still used.

The new longer key length is not hardcoded in the protocol anymore,
the client is expected to deal with variable length keys, up to 256
bytes. This flexibility allows e.g. a connection pooler to add more
information to the cancel key, which might be useful for finding the
connection.

Reviewed-by: Jelte Fennema-Nio <postgres@jeltef.nl>
Reviewed-by: Robert Haas <robertmhaas@gmail.com> (earlier versions)
Discussion: https://www.postgresql.org/message-id/508d0505-8b7a-4864-a681-e7e5edfe32aa@iki.fi

1 files changed, 10 insertions, 2 deletions

diff --git a/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl b/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl
index 9691b850418..61524bdbd8f 100644
--- a/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl
+++ b/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl
@@ -49,11 +49,11 @@ for my $testname (@tests)
 		push @extraargs, "-t" => $traceout;
 	}
 
-	# Execute the test
+	# Execute the test using the latest protocol version.
 	$node->command_ok(
 		[
 			'libpq_pipeline', @extraargs,
-			$testname, $node->connstr('postgres')
+			$testname, $node->connstr('postgres') . " max_protocol_version=latest"
 		],
 		"libpq_pipeline $testname");
 
@@ -72,6 +72,14 @@ for my $testname (@tests)
 	}
 }
 
+# There were changes to query cancellation in protocol version 3.2, so
+# test separately that it still works the old protocol version too.
+$node->command_ok(
+	[
+	 'libpq_pipeline', 'cancel', $node->connstr('postgres') . " max_protocol_version=3.0"
+	],
+	"libpq_pipeline cancel with protocol 3.0");
+
 $node->stop('fast');
 
 done_testing();