Add a very simple parse for COF in python including validation of the

format.

example_code/python/README.md

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+# Example python parser
+
+This little package can parse the Passive DNS Common Output Format (COF) and validate it.
+It is given as example code.
+
+

example_code/python/cofparser.py

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+"""
+Example passive DNS Common Output Format]() parser.
+It will parse the JSON file and validate it.
+
+Author: Aaron Kaplan <aaron@lo-res.org>
+Copyright 2021, all rights reserved.
+
+License: AGPL v3. See https://www.gnu.org/licenses/agpl-3.0.en.html
+"""
+
+import sys
+import json         # maybe use an ndjson library...
+
+
+def is_valid(d: dict) -> bool:
+    # Check MANDATORY fields according to COF
+    if "rrname" not in d:
+        print("Missing MANDATORY field 'rrname'", file=sys.stderr)
+        return False
+    if not isinstance(d['rrname'], str):
+        print("Type error: 'rrname' is not a JSON string", file=sys.stderr)
+        return False
+    if "rrtype" not in d:
+        print("Missing MANDATORY field 'rrtype'", file=sys.stderr)
+        return False
+    if not isinstance(d['rrtype'], str):
+        print("Type error: 'rrtype' is not a JSON string", file=sys.stderr)
+        return False
+    if "rdata" not in d:
+        print("Missing MANDATORY field 'rdata'", file=sys.stderr)
+        return False
+    if "rdata" not in d:
+        print("Missing MANDATORY field 'rdata'", file=sys.stderr)
+        return False
+    if not isinstance(d['rdata'], str) and not isinstance(d['rdata'], list):
+        print("'rdata' is not a list and not a string.", file=sys.stderr)
+        return False
+    if not ("time_first" in d and "time_last" in d) or ("zone_time_first" in d and "zone_time_last" in d):
+        print("We are missing EITHER ('first_seen' and 'last_seen') OR ('zone_time_first' and zone_time_last') fields")
+        return False
+    # currently we don't check the OPTIONAL fields. Sorry... to be done later.
+    return True
+
+
+def parse_line(input: str) -> dict:
+    d = None
+    try:
+        d = json.loads(input)
+        if not is_valid(d):
+            print("Warning: line %s does not conform to the COF standard." % input)
+    except Exception as ex:
+        print("error. Could not parse input '%s'. Reason: '%s'" %(input, str(ex)), file=sys.stderr)
+    return d
+
+
+def parse_lines(multilines: str):
+    for line in multilines.split('\n'):
+        yield parse_line(line)
+
+
+if __name__ == "__main__":
+    mock_input = """{"count":1909,"rdata":["cpa.circl.lu"],"rrname":"www.circl.lu","rrtype":"CNAME","time_first":"1315586409","time_last":"1449566799"}
+{"count":2560,"rdata":["cpab.circl.lu"],"rrname":"www.circl.lu","rrtype":"CNAME","time_first":"1449584660","time_last":"1617676151"}"""
+
+    for result in parse_lines(mock_input):
+        print("result: %r" % result)