#!/usr/bin/python3
import socket
import sys

if len(sys.argv) != 4:
	print ("Usage:	" + sys.argv[0] + " <ip> <usernames file> <n usernames>")
	sys.exit(0)

with open(sys.argv[2]) as f:
	users = f.readlines()

# only unique user names
used=set()
totest=list()
i=0
while i <= len(users) and len(used) < int(sys.argv[3]):
	i += 1
# we will do case-insesitive search enumeration
	name = users[i].strip().lower()
	if name in used or len(name) == 0:
		continue
	else:
		totest.append(name)
		used.add(name)

s=socket.socket(socket.AF_INET,	socket.SOCK_STREAM)
# for the servers which do not reply to HELO/EHLO message
s.settimeout(4)
connect=s.connect((sys.argv[1],25))
banner=s.recv(1024)
print("Banner:")
print(banner.decode("ASCII"))

s.send(("EHLO acme.local\r\n").encode("ASCII"))
try:
	reply=s.recv(1024)
	print("Replying to HELO:")
	print(reply.decode("ASCII"))
except:
	print("Timed out")

# enumeration
for n in totest:
	s.send(('VRFY ' + n + '\r\n').encode("ASCII"))
	result=s.recv(1024).decode("ASCII").strip()
# output in a grep-friendly format
	print(sys.argv[1] + " " + n + " " + result)
	sys.stdout.flush()
s.close()