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"""
This example expands on the print_packets example. It checks for HTTP request headers and displays their contents.
NOTE: We are not reconstructing 'flows' so the request (and response if you tried to parse it) will only
parse correctly if they fit within a single packet. Requests can often fit in a single packet but
Responses almost never will. For proper reconstruction of flows you may want to look at other projects
that use DPKT (http://chains.readthedocs.io and others)
"""
import dpkt
import datetime
from dpkt.utils import mac_to_str, inet_to_str
def print_http_requests(pcap):
"""Print out information about each packet in a pcap
Args:
pcap: dpkt pcap reader object (dpkt.pcap.Reader)
"""
# For each packet in the pcap process the contents
for timestamp, buf in pcap:
# Unpack the Ethernet frame (mac src/dst, ethertype)
eth = dpkt.ethernet.Ethernet(buf)
# Make sure the Ethernet data contains an IP packet
if not isinstance(eth.data, dpkt.ip.IP):
print('Non IP Packet type not supported %s\n' % eth.data.__class__.__name__)
continue
# Now grab the data within the Ethernet frame (the IP packet)
ip = eth.data
# Check for TCP in the transport layer
if isinstance(ip.data, dpkt.tcp.TCP):
# Set the TCP data
tcp = ip.data
# Now see if we can parse the contents as a HTTP request
try:
request = dpkt.http.Request(tcp.data)
except (dpkt.dpkt.NeedData, dpkt.dpkt.UnpackError):
continue
# Pull out fragment information (flags and offset all packed into off field, so use bitmasks)
do_not_fragment = bool(ip.off & dpkt.ip.IP_DF)
more_fragments = bool(ip.off & dpkt.ip.IP_MF)
fragment_offset = ip.off & dpkt.ip.IP_OFFMASK
# Print out the info
print('Timestamp: ', str(datetime.datetime.utcfromtimestamp(timestamp)))
print('Ethernet Frame: ', mac_to_str(eth.src), mac_to_str(eth.dst), eth.type)
print('IP: %s -> %s (len=%d ttl=%d DF=%d MF=%d offset=%d)' %
(inet_to_str(ip.src), inet_to_str(ip.dst), ip.len, ip.ttl, do_not_fragment, more_fragments, fragment_offset))
print('HTTP request: %s\n' % repr(request))
# Check for Header spanning acrossed TCP segments
if not tcp.data.endswith(b'\r\n'):
print('\nHEADER TRUNCATED! Reassemble TCP segments!\n')
def test():
"""Open up a test pcap file and print out the packets"""
with open('data/http.pcap', 'rb') as f:
pcap = dpkt.pcap.Reader(f)
print_http_requests(pcap)
if __name__ == '__main__':
test()
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