Re2Pcap : Create PCAP file From Raw HTTP Request Or Response In Seconds

Re2Pcap is abbreviation for Request2Pcap and Response2Pcap. Community users can quickly create PCAP file using it and test them against Snort rules.

It allow you to quickly create PCAP file for raw HTTP request shown below;

POST /admin/tools/iplogging.cgi HTTP/1.1
Host: 192.168.13.31:80
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0
Accept: text/plain, /; q=0.01
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://192.168.13.31:80/admin/tools/iplogging.html
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
Content-Length: 63
Cookie: token=1e9c07e135a15e40b3290c320245ca9a
Connection: close

tcpdumpParams=tcpdump -z reboot -G 2 -i eth0&stateRequest=start

Usage

git clone https://github.com/Cisco-Talos/Re2Pcap.git
cd Re2Pcap/
docker build -t re2pcap .
docker run –rm –cap-add NET_ADMIN -p 5000:5000 re2pcap

OR

docker run –rm –cap-add NET_ADMIN -p 5000:5000 –name re2pcap amitraut/re2pcap

Open localhost:5000 in your web browser to access it or use Re2Pcap-cmd script to interact with it container to get PCAP in current working directory

Also Read – WhatTheHack : A Collection Of Challenge Based Hack

Requirements

  • Docker
  • HTTP Raw Request / Response
  • Web Browser (for best results, please use Chromium based web browsers)

Advantages

  • Easy setup. No complex multi-VM setup required
  • It runs on Alpine Linux based docker image that weighs less than 100 MB 😀
  • Allows you to dump simulated raw HTTP request and response in to PCAP

Dockerfile

FROM alpine

#Get required dependencies and setup for Re2Pcap
RUN echo “http://dl-cdn.alpinelinux.org/alpine/edge/testing” >> /etc/apk/repositories
RUN apk update && apk add python3 tcpdump tcpreplay
RUN pip3 install –upgrade pip
RUN pip3 install pexpect flask requests httpretty requests-toolbelt

COPY Re2Pcap/ /Re2Pcap
RUN cd Re2Pcap && chmod +x Re2Pcap.py

WORKDIR /Re2Pcap
EXPOSE 5000/tcp

#Run application at start of new container
CMD [“/usr/bin/python3”, “Re2Pcap.py”]

Walkthrough

Workflow

As shown in the above image it is Alpine Linux based Python3 application with Flask based web interface

It parses the input data as raw HTTP request or response and actually perfoms client/server interaction while capturing packets. After the interaction it presents the captured packets as PCAP file

Recommendations

  • Please use Linux as your host operating system as it is well tested on Linux
  • If creating PCAP for Host: somedomain:5000 i.e. port 5000, please change Flask application to run on other port by modifying Re2Pcap.Py app.run call otherwise PCAP will contain Flask application response

Limitations

  • If raw HTTP request is without Accept-Encoding: header Accept-Encoding: identity is added in the reqeust
    • There is known issue for it in python requests. Following is closing note for that issue That’s really fairly terrible. Accept-Encoding: identity is always valid, the RFCs say so. It should be utterly harmless to send it along. Otherwise, removing this requires us to replace httplib. That’s a substantial bit of work. =(
  • The following are source and desination IPs in PCAPs from it
    • Sourece IP: 10.10.10.1
    • Destination IP: 172.17.0.2 or (Re2Pcap Container’s IP Address) Please use tcprewrite -D option to modify desitnation IP to something else as per your need. You may also use tcpprep and tcprewrite to set other IPs as endpoints. Due to inconsistent result of tcprewrite I used alternative way to set different SRC/DST IPs
  • Specifying HTTP/1.1 302 FOUND as response will generated PCAP with maximum possible retries to reach resource specified in Location: header. Plase export the first HTTP stream using wireshark in testing if you do not like the additional noise of other streams
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