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#!/usr/bin/env python
#dhcpd.py pure python dhcp server pxe capable
#psychomario - https://github.com/psychomario
import socket,binascii,time,IN
from sys import exit
from optparse import OptionParser
if not hasattr(IN,"SO_BINDTODEVICE"):
IN.SO_BINDTODEVICE = 25 #http://stackoverflow.com/a/8437870/541038
def slicendice(msg,slices): #generator for each of the dhcp fields
for x in slices:
if str(type(x)) == "<type 'str'>": x=eval(x) #really dirty, deals with variable length options
yield msg[:x]
msg = msg[x:]
# Convert hex IP to string with formated decimal IP
def hex_ip_to_str(hex_ip):
hex_pieces = [hex_ip[i:i+2] for i in range(0, len(hex_ip), 2)] # split hex string into hex chunks
bin_pieces = map(lambda x: int(x, 16), hex_pieces) # convert from hex to dec
return '.'.join(str(y) for y in bin_pieces) # cast int to str for join
def format_hex_mac(hex_mac):
hex_pieces = [hex_mac[i:i+2] for i in range(0, len(hex_mac), 2)]
return ':'.join(str(x) for x in hex_pieces)
# Splits a chunk of hex into a list of hex. e.g. 0123456789abcdef = ['01', '23', '45', '67', '89', 'ab', 'cd', 'ef']
def chunk_hex(hex):
return [hex[i:i+2] for i in range(0, len(hex), 2)]
def parse_options(raw):
print(' --> processing DHCP options')
raw = '3501013d13ffeb9a520f000100011c1b8324b827eb9a520f5000390205dc3c306468637063642d362e362e373a4c696e75782d332e31322e33352d312d415243483a61726d76366c3a42434d323730380c07616c61726d7069910101370e01792103060c0f1c2a33363a3b775223012164697374726f2d746573743a67652d302f302f31322e303a626f6f747374726170'
raw = '3501013c3c4a756e697065722d6578323230302d632d3132742d3267000000000000000000000000000000000000000000000000000000000000000000000000005222012064697374726f2d746573743a67652d302f302f302e303a626f6f747374726170ff'
chunked = chunk_hex(raw)
chunked_length = len(chunked)
next = 0 # counter - next option start
options = {} # options dataset
while True:
option = int(chunked[next], 16) # convert to dec
length = int(chunked[next+1], 16) # convert to dec
options[option] = raw[((next+2)*2):((next+length+2)*2)].decode("hex") # getting the options
next = next + length + 2 # length of option + length field (1 chunk) + option ID (1 chunk)
print(' --> option: %s (length: %s) (next option starting on chunk %s)' % (option, length, next))
if option is 82:
parse_option_82(binascii.hexlify(options[option])) # TODO: "ugly as fuck want to go to bed-hax" must be fixed before 02:21 AM
if int(chunked[next], 16) == 255:
print(' --> finished processing options')
break
return options
def parse_option_82(raw):
print(' --> processing hook for option 82')
# print('RAW:', raw)
chunked = chunk_hex(raw)
chunked_length = len(chunked)
if int(chunked[0], 16) is 1: # suboption 1
subopt_1_length = int(chunked[2], 16)
print(' --> suboption 1 found - value: "%s"' % raw[2:(subopt_1_length+2)].decode("hex"))
def reqparse(message): #handles either DHCPDiscover or DHCPRequest
#using info from http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol
#the tables titled DHCPDISCOVER and DHCPOFFER
data=None
# Length of DHCP fields in octets, and their placement in packet.
# Ref: http://4.bp.blogspot.com/-IyYoFjAC4l8/UXuo16a3sII/AAAAAAAAAXQ/b6BojbYXoXg/s1600/DHCPTitle.JPG
# OP - 1
# HTYPE - 1
# HLEN - 1
# HOPS - 1
# XID - 4
# SECS - 2
# FLAGS - 2
# CIADDR - 4
# YIADDR - 4
# SIADDR - 4
# GIADDR - 4
# CHADDR - ?????
# PADDING - 192 octets of 0's
# MAGIC COOKIE - 4
# OPTIONS - Magic goes here
dhcpfields=[1,1,1,1,4,2,2,4,4,4,4,6,10,192,4,"msg.rfind('\xff')",1,None]
#send: boolean as to whether to send data back, and data: data to send, if any
#print len(message)
hexmessage=binascii.hexlify(message)
messagesplit=[binascii.hexlify(x) for x in slicendice(message,dhcpfields)]
# print(messagesplit)
dhcpopt=messagesplit[15][:6] #hope DHCP type is first. Should be.
if dhcpopt == '350101': # option 53 - identifies DHCP packet type - discover/request/offer/ack++
print('DHCP Discover')
if(int(dhcpfields[10]) is not 0):
print(' --> Relay: %s' % hex_ip_to_str(messagesplit[10]))
print(' --> Client MAC: %s' % format_hex_mac(messagesplit[11]))
# print('DHCP Options: ', messagesplit[15])
options = parse_options('x')
# print(options)
print(' --> crafting response')
# print('parse_options: ', parse_options('x'))
#DHCPDiscover
#craft DHCPOffer
#DHCPOFFER creation:
#options = \xcode \xlength \xdata
lease=getlease(messagesplit[11])
print 'Leased:',lease
data='\x02\x01\x06\x00'+binascii.unhexlify(messagesplit[4])+'\x00\x04'
data+='\x80\x00'+'\x00'*4+socket.inet_aton(lease)
data+=socket.inet_aton(address)+'\x00'*4
data+=binascii.unhexlify(messagesplit[11])+'\x00'*10+'\x00'*192
data+='\x63\x82\x53\x63'+'\x35\x01\x02'+'\x01\x04'
data+=socket.inet_aton(netmask)+'\x36\x04'+socket.inet_aton(address)
data+='\x1c\x04'+socket.inet_aton(broadcast)+'\x03\x04'
data+=socket.inet_aton(gateway)+'\x06\x04'+socket.inet_aton(dns)
data+='\x33\x04'+binascii.unhexlify(hex(leasetime)[2:].rjust(8,'0'))
data+='\x42'+binascii.unhexlify(hex(len(tftp))[2:].rjust(2,'0'))+tftp
data+='\x43'+binascii.unhexlify(hex(len(pxefilename)+1)[2:].rjust(2,'0'))
data+=pxefilename+'\x00\xff'
elif dhcpopt == '350103':
print('DHCP ACK')
#DHCPRequest
#craft DHCPACK
data='\x02\x01\x06\x00'+binascii.unhexlify(messagesplit[4])+'\x00'*8
data+=binascii.unhexlify(messagesplit[15][messagesplit[15].find('3204')+4:messagesplit[15].find('3204')+12])
data+=socket.inet_aton(address)+'\x00'*4
data+=binascii.unhexlify(messagesplit[11])+'\x00'*202
data+='\x63\x82\x53\x63'+'\x35\x01\05'+'\x36\x04'+socket.inet_aton(address)
data+='\x01\x04'+socket.inet_aton(netmask)+'\x03\x04'
data+=socket.inet_aton(address)+'\x33\x04'
data+=binascii.unhexlify(hex(leasetime)[2:].rjust(8,'0'))
data+='\x42'+binascii.unhexlify(hex(len(tftp))[2:].rjust(2,'0'))
data+=tftp+'\x43'+binascii.unhexlify(hex(len(pxefilename)+1)[2:].rjust(2,'0'))
data+=pxefilename+'\x00\xff'
return data
def release(): #release a lease after timelimit has expired
for lease in leases:
if not lease[1]:
if time.time()+leasetime == leasetime:
continue
if lease[-1] > time.time()+leasetime:
print "Released",lease[0]
lease[1]=False
lease[2]='000000000000'
lease[3]=0
def getlease(hwaddr): #return the lease of mac address, or create if doesn't exist
global leases
for lease in leases:
if hwaddr == lease[2]:
return lease[0]
for lease in leases:
if not lease[1]:
lease[1]=True
lease[2]=hwaddr
lease[3]=time.time()
return lease[0]
if __name__ == "__main__":
parser = OptionParser(description='%prog - a simple DHCP server', usage='%prog [options]')
parser.add_option("-a", "--address", dest="address", action="store", help='server ip address (required).')
parser.add_option("-i", "--interface", dest="interface", action="store", help='network interface to use (default all interfaces).')
parser.add_option("-p", "--port", dest="port", action="store", help='server port to bind (default 67).')
parser.add_option("-f", "--from", dest="offerfrom", action="store", help='ip pool from (default x.x.x.100).')
parser.add_option("-t", "--to", dest="offerto", action="store", help='ip pool to (default x.x.x.150).')
parser.add_option("-b", "--broadcast", dest="broadcast", action="store", help='broadcast ip to reply (x.x.x.254).')
parser.add_option("-n", "--netmask", dest="netmask", action="store", help='netmask (default 255.255.255.0).')
parser.add_option("-s", "--tftp", dest="tftp", action="store", help='tftp ip address (default ip address provided).')
parser.add_option("-d", "--dns", dest="dns", action="store", help='dns ip address (default 8.8.8.8).')
parser.add_option("-g", "--gateway", dest="gateway", action="store", help='gateway ip address (default ip address provided).')
parser.add_option("-x", "--pxefilename", dest="pxefilename", action="store", help='pxe filename (default pxelinux.0).')
(options, args) = parser.parse_args()
if not (args or options.address):
parser.print_help()
exit(1)
if options.interface:
interface = options.interface
else:
interface = '' # Symbolic name meaning all available interfaces
if options.port:
port = options.port
else:
port = '67'
port = int(port)
if options.address:
address = options.address
elements_in_address = address.split('.')
if len(elements_in_address) != 4:
sys.exit(os.path.basename(__file__) + ": invalid ip address")
else:
exit(1)
if options.offerfrom:
offerfrom = options.offerfrom
else:
offerfrom = '.'.join(elements_in_address[0:3])
offerfrom = offerfrom + '.100'
if options.offerto:
offerto = options.offerto
else:
offerto = '.'.join(elements_in_address[0:3])
offerto = offerto + '.150'
if options.broadcast:
broadcast = options.broadcast
else:
broadcast = '.'.join(elements_in_address[0:3])
broadcast = broadcast + '.254'
if options.netmask:
netmask = options.netmask
else:
netmask = '255.255.255.0'
if options.tftp:
tftp = options.tftp
else:
tftp = address
if options.dns:
dns = options.dns
else:
dns = '8.8.8.8'
if options.gateway:
gateway = options.gateway
else:
gateway = address
if options.pxefilename:
pxefilename = options.pxefilename
else:
pxefilename = 'pxelinux.0'
leasetime=86400 #int
leases=[]
#next line creates the (blank) leases table. This probably isn't necessary.
for ip in ['.'.join(elements_in_address[0:3])+'.'+str(x) for x in range(int(offerfrom[offerfrom.rfind('.')+1:]),int(offerto[offerto.rfind('.')+1:])+1)]:
leases.append([ip,False,'000000000000',0])
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.setsockopt(socket.SOL_SOCKET,IN.SO_BINDTODEVICE,interface+'\0') #experimental
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
s.bind(('',port))
#s.sendto(data,(ip,port))
while 1: #main loop
try:
message, addressf = s.recvfrom(8192)
if not message.startswith('\x01') and not addressf[0] == '0.0.0.0':
continue #only serve if a dhcp request
data=reqparse(message) #handle request
if data:
s.sendto(data,('<broadcast>',68)) #reply
release() #update releases table
except KeyboardInterrupt:
exit()
# except:
# continue
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