NAME
scapy - Interactive packet manipulation tool
SYNOPSIS
scapy [options]
DESCRIPTION
This manual page documents briefly the scapy tool.
scapy is a powerful interactive packet manipulation tool, packet
generator, network scanner, network discovery, packet sniffer, etc. It
can for the moment replace hping, parts of nmap, arpspoof, arp-sk,
arping, tcpdump, tshark, p0f, ...
scapy uses the python interpreter as a command board. That means that
you can use directly python language (assign variables, use loops,
define functions, etc.) If you give a file as parameter when you run
scapy, your session (variables, functions, intances, ...) will be saved
when you leave the interpretor, and restored the next time you launch
scapy.
The idea is simple. Those kind of tools do two things : sending packets
and receiving answers. That’s what scapy does : you define a set of
packets, it sends them, receives answers, matches requests with answers
and returns a list of packet couples (request, answer) and a list of
unmatched packets. This has the big advantage over tools like nmap or
hping that an answer is not reduced to (open/closed/filtered), but is
the whole packet.
On top of this can be build more high level functions, for example one
that does traceroutes and give as a result only the start TTL of the
request and the source IP of the answer. One that pings a whole network
and gives the list of machines answering. One that does a portscan and
returns a LaTeX report.
OPTIONS
Options for scapy are:
-h display usage
-d increase log verbosity. Can be used many times.
-s FILE
use FILE to save/load session values (variables, functions,
intances, ...)
-p PRESTART_FILE
use PRESTART_FILE instead of $HOME/.scapy_prestart.py as pre-
startup file
-P do not run prestart file
-c STARTUP_FILE
use STARTUP_FILE instead of $HOME/.scapy_startup.py as startup
file
-C do not run startup file
COMMANDS
Only the vital commands to begin are listed here for the moment.
ls() lists supported protocol layers. If a protocol layer is given as
parameter, lists its fields and types of fields.
lsc() lists some user commands. If a command is given as parameter,
its documentation is displayed.
conf this object contains the configuration.
FILES
$HOME/.scapy_prestart.py This file is run before scapy core is loaded.
Only the is available. This file can be used to manipulate
conf.load_layers list to choose which layers will be loaded:
conf.load_layers.remove("bluetooth")
conf.load_layers.append("new_layer")
$HOME/.scapy_startup.py This file is run after scapy is loaded. It can
be used to configure some of the scapy behaviors:
conf.prog.pdfreader="xpdf"
split_layers(UDP,DNS)
EXAMPLES
More verbose examples are available at
http://www.secdev.org/projects/scapy/demo.html Just run scapy and try
the following commands in the interpreter.
Test the robustness of a network stack with invalid packets:
sr(IP(dst="172.16.1.1", ihl=2, options="b$2$", version=3)/ICMP())
Packet sniffing and dissection (with a bpf filter or thetereal-like
output):
a=sniff(filter="tcp port 110")
a=sniff(prn = lambda x: x.display)
Sniffed packet reemission:
a=sniff(filter="tcp port 110")
sendp(a)
Pcap file packet reemission:
sendp(rdpcap("file.cap"))
Manual TCP traceroute:
sr(IP(dst="www.google.com", ttl=(1,30))/TCP(seq=RandInt(), sport=RandShort(), dport=dport)
Protocol scan:
sr(IP(dst="172.16.1.28", proto=(1,254)))
ARP ping:
srp(Ether(dst="ff:ff:ff:ff:ff:ff")/ARP(pdst="172.16.1.1/24"))
ACK scan:
sr(IP(dst="172.16.1.28")/TCP(dport=(1,1024), flags="A"))
Passive OS fingerprinting:
sniff(prn=prnp0f)
Active OS fingerprinting:
nmap_fp("172.16.1.232")
ARP cache poisonning:
sendp(Ether(dst=tmac)/ARP(op="who-has", psrc=victim, pdst=target))
Reporting:
report_ports("192.168.2.34", (20,30))
SEE ALSO
http://www.secdev.org/projects/scapy
http://trac.secdev.org/scapy
BUGS
Does not give the right source IP for routes that use interface
aliases.
May miss packets under heavy load.
Session saving is limited by Python ability to marshal objects. As a
consequence, lambda functions and generators can’t be saved, which
seriously reduce usefulness of this feature.
BPF filters don’t work on Point-to-point interfaces.
AUTHOR
Philippe Biondi <phil@secdev.org>
This manual page was written by Alberto Gonzalez Iniesta <agi@agi.as>
and Philippe Biondi.
May 12, 2003