Add test case for binpac flowbuffer frame length parsing bug

testing/btest/plugins/binpac-flowbuffer-frame-length.zeek

@@ -0,0 +1,40 @@
+# This test exercises a previous bug in binpac flowbuffer frame length
+# boundary checks:
+
+# Incremental flowbuffer parsing sought to first parse the "minimum header
+# length" required to get the full frame length, possibly from a record
+# field, but generating the logic to parse that field could greedily
+# bundle in additional boundary-checks for all subsequent fields of
+# known-size.
+#
+# E.g. for flowunit parsing of this:
+#
+#     type HDR = record {
+#         version:    uint8;
+#         reserved:   uint8;
+#         len:        uint16;
+#     } &byteorder=bigendian;
+#
+#     type FOO_PDU(is_orig: bool) = record {
+#         hdr:        HDR;
+#         plen:       uint8;
+#         ptype:      uint8;
+#         something:  bytestring &restofdata;
+#     } &byteorder=bigendian, &length=hdr.len;
+
+# The flowbuffer was correctly seeking to buffer 4 bytes and parse the
+# "hdr.len" field, but the generated parsing logic for "hdr.len" included
+# a boundary check all the way up to include "plen" and "ptype".
+
+# This causes out-of-bounds exceptions to be thrown for inputs that should
+# actually be possible to incrementally parse via flowbuffer.
+
+# @TEST-EXEC: ${DIST}/aux/zeek-aux/plugin-support/init-plugin -u . Foo FOO
+# @TEST-EXEC: cp -r %DIR/binpac-flowbuffer-frame-length-plugin/* .
+# @TEST-EXEC: ./configure --zeek-dist=${DIST} && make
+# @TEST-EXEC: ZEEK_PLUGIN_PATH=`pwd` zeek -r $TRACES/mmsX.pcap %INPUT >output
+
+event Foo::foo_message(c: connection, is_orig: bool, len: count, plen: count, ptype: count)
+	{
+	print "foo_message", len, plen, ptype;
+	}