DanaEpp · October 20, 2022 17:56 · Oct 20, 2022
diff --git a/guid_reaper.py b/guid_reaper.py
@@ -0,0 +1,109 @@
+#!/bin/env python3
+
+import argparse
+import datetime
+import re
+import sys
+import uuid
+
+###############################################################################
+# Based off of Daniel Thatcher's guid tool
+# Additional reading from https://duo.com/labs/tech-notes/breaking-down-uuids
+###############################################################################
+
+# A nano second is a billionth of a second, so...
+# 1 second = 1e7 100-nanosecond intervals
+NANO_INTERVAL = 1e7
+
+def uuid_time(uid):
+	# Gregorian reform to the Christian calendar (Oct 15, 1582)
+	# See https://datatracker.ietf.org/doc/html/rfc4122#section-4.2.2
+	dt_base = datetime.datetime( 1582, 10, 15 )
+	return dt_base + datetime.timedelta(microseconds=uid.time//10)
+
+def uuid_mac(uid):
+	return ":".join(re.findall('..', '%012x' % uid.node))
+
+def dump_guid(guid):
+	try:
+		uid = uuid.UUID(guid)
+	except ValueError:
+		print("Invalid GUID")
+		sys.exit(2)
+
+	print ("GUID version: {}".format(uid.version))
+
+	if uid.version == 1:
+		t = uuid_time(uid)
+		print("Time: {}".format(t))
+		print("Timestamp: {}".format(uid.time))
+		print("Node: {}".format(uid.node))
+		m = uuid_mac(uid)
+		print("MAC address: {}".format(m))
+		print("Clock sequence: {}".format(uid.clock_seq))
+
+def uuid1(node, clock_seq, timestamp):
+	time_low = timestamp & 0xffffffff
+	time_mid = (timestamp >> 32) & 0xffff
+	time_hi_version = (timestamp >> 48) & 0x0fff
+	clock_seq_low = clock_seq & 0xff
+	clock_seq_hi_variant = (clock_seq >> 8) & 0x3f
+	return uuid.UUID(fields=(time_low, time_mid, time_hi_version,
+		clock_seq_hi_variant, clock_seq_low, node), version=1)
+
+def get_precision(timestamp):
+	# Determine the precision by looking at how many 0 are at the end 
+	# of the previously captured timestamp
+	ts = str(timestamp)
+	l = len(ts) - len(ts.rstrip('0'))
+	return int("1".ljust(l+1, '0'))
+
+def gen_guids(sample_guid, estimated_ts):
+	uid = uuid.UUID(sample_guid)
+	if uid.version != 1:
+		print( "We can only generate GUIDs v1. Aborting." )
+		sys.exit(2)
+
+	# Calculate the timestamp for the first GUID
+	dt_base = datetime.datetime( 1582, 10, 15 )
+	base_guid_time = estimated_ts - dt_base
+	base_timestamp = int(base_guid_time.total_seconds() * NANO_INTERVAL)
+
+	seconds = 2
+	precision = get_precision(uid.time)
+	start_time = int(base_timestamp - (NANO_INTERVAL) * seconds)
+	end_time = int(base_timestamp + (NANO_INTERVAL) * seconds)
+
+	for t in range( start_time, end_time, precision ):
+		yield uuid1(uid.node, uid.clock_seq, t)
+
+def main():
+	parser = argparse.ArgumentParser()
+	parser.add_argument("-d", "--dump", help="Dump decoded GUID and exit", action="store_true")
+	parser.add_argument("-t", "--time",
+                        help="The estimated time at which the GUID was generated. ie: '2021-02-27 17:42:01'",
+                        type=lambda s: datetime.datetime.strptime(s, "%Y-%m-%d %H:%M:%S"))
+	parser.add_argument("guid", help="The GUID to inspect")
+	args = parser.parse_args()
+
+	# Validate GUID
+	try:
+		_ = uuid.UUID(args.guid)
+	except:
+		print("Invalid GUID. Aborting.")
+		sys.exit(1)
+
+	# Dump GUID and exit if that's what we want
+	if args.dump:
+        	dump_guid(args.guid)
+        	sys.exit(0)
+
+	if args.time is None:
+		print( "Timestamp required. Use '-t' option. Aborting.")
+		sys.exit(1)
+
+	for u in gen_guids(args.guid, args.time):
+		print(u)
+
+if __name__ == "__main__":
+	main()