feat(fuzz): Adds seed corpus for cdc and msc classes

tools/pcapng_to_corpus.py

@@ -0,0 +1,46 @@
+#!/bin/python3
+import argparse
+import pcapng
+import zipfile
+import hashlib
+
+def extract_packets(pcap_file):
+    """Reads a wireshark packet capture and extracts the binary packets"""
+    packets = []
+    with open(pcap_file, 'rb') as fp:
+        scanner = pcapng.FileScanner(fp)
+        for block in scanner:
+            if isinstance(block, pcapng.blocks.EnhancedPacket):
+                packets.append(block.packet_data)
+    return packets
+
+def build_corpus_zip(zip_file_output, packets):
+    """Builds a zip file with a file per packet
+    
+    The structure of this zip corpus is a simple content addressable storage
+    i.e. seed_file_name == sha256_digest(packet).
+    """
+    with zipfile.ZipFile(zip_file_output, 'a') as out:
+        for packet in packets:
+            hash = hashlib.sha256(packet).hexdigest()
+            if hash not in out.namelist():
+                out.writestr(hash, packet)
+    
+
+def main(pcap_file, output_zip_file):
+    packets = extract_packets(pcap_file)
+    build_corpus_zip(output_zip_file, packets)
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        prog = "pcapng_to_corpus.py",
+        description="""Converts a wireshark capture to a zip of binary packet
+                    files suitable for an oss-fuzz corpus. In the case the 
+                    zip corpus already exists, this script will modify 
+                    the zip file in place adding seed entries.""")
+    parser.add_argument('pcapng_capture_file')
+    parser.add_argument('oss_fuzz_corpus_zip')
+    args = parser.parse_args()
+    main(args.pcapng_capture_file, args.oss_fuzz_corpus_zip)
+    
+