CODEWITHSUNDEEP
pythonnetwork-programmingscapy
Christoph
Christoph

Reputation: 89

Specifying packet length with scapy

I'm trying to send a specific packet size (100 bytes) with scapy but cant seem to get it.

I'm using this to start. 

sr(IP(dst="192.168.1.1")/TCP(dport=443))

Looking at the docs / help I cant tell if I can use PacketLenField to specify the length of the packet. I can do it with NMAP & NSE but would like to do it outside of NMAP.

Any ideas on this one?

Thanks!

Upvotes: 4

Views: 22225

Answers (3)

Konstantin
Konstantin

Reputation: 3159

You may use inet.Padding() from scapy library:

packet = IP(dst="192.168.1.1")/TCP(dport=443)

if len(packet)<100:
    #"\x00" is a single zero byte
    myString = "\x00"*(100 - len(packet))
    packet = packet/inet.Padding(myString)

Upvotes: 1

BeefSupreme
BeefSupreme

Reputation: 138

Scapy's Raw() function populates the payload of the packet. If you know your header size, you only need to fill in the remaining bytes with random data.

You can use RandString() to generate random padding. The following command sends a packet of length 100 (and listens for a response):

sr(IP(dst="192.168.1.1")/TCP(dport=443)/Raw(RandString(size=72))

Upvotes: 2

wookie919
wookie919

Reputation: 3134

You can just add on the required number of bytes as a String when crafting the packet e.g.:

payload = 'ZZZZZZZZZZZZZZZZZZZZZ'
pkt = Ether() / IP() / TCP() / payload

will work. You just need to adjust the length of the payload as you require.

Upvotes: 5

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