karimkanso/simple-client repository overview

⁠SimpleHTTP

Very simple client server written in Go for testing connections from the command line. Ideal for placing into Docker images and running in GNS3⁠ for testing a firewalls HTTP configuration.

The server writes out a single line of text for each request that details the client and page requested.

The client just performs a HTTP GET to the server address with a unique request code that the server will echo back. Further, the client will check the unique code echo'ed back is the same as it expected.

To install directly, follow standard Go procedure:

go get github.com/kazkansouh/simplehttp/server
go get github.com/kazkansouh/simplehttp/client

⁠Usage

user@hostname:~$ client -help
Usage of ./bin/client:
  -host string
        Remote host to connect to. (default "localhost")
  -port uint
        Port of remote host. (default 8080)
  -requestid string
        The page to request from server, default is a random uuid. (default "hostname-118e24a3-48c0-4b96-b266-01ab13c50c18")
  -verbose
        Display detailed information.

user@hostname:~$ server -help
Usage of ./bin/server:
  -port uint
        Port to run web server on. (default 8080)

While the server is running, it lists out each connection it receives, notice it lists out the requested URL (when used with the client it also lists the hostname of the client):

username@hostname:~$ server
2019/04/19 08:44:34 Starting simple server! version 0.1
2019/04/19 08:44:34 Listening on port 8080
2019/04/19 08:44:42 127.0.0.1:50720 requested /hosta-69f68c8e-a1ce-4b88-a0b2-3a149c8e60b5
2019/04/19 08:44:43 192.168.0.2:50732 requested /hostb-0cf6aed3-7b82-4a56-876a-e3608197b138
2019/04/19 08:44:44 127.0.0.1:50738 requested /hosta-b07b3587-a539-498f-8155-95fac18dce70

⁠GNS3 Docker image

The suggested method to deploy within GNS3 is to use the Docker images available on DockerHub (client⁠, server⁠) and the provided appliance files. In the appliance⁠ directory there are two gns3a files to simplify the import process. Simply download the files and open with GNS3. To change the server port in GNS3, set the environment variable PORT on the server container, there is no need to expose ports.

The Docker images are intended to provide a similar level of functionality to the standard gns3/ipterm⁠ image that is available with GNS3.

⁠Docker image building

Two Dockerfiles provided have been tested with GNS3 and built over a recent alpine image. The set of network tools included are similar to the gns3/ipterm image, this was needed as the gns3/ipterm (which the first version of this code used) is based off Debian Jessie, hence many of the software packages in the repo are also becoming dated.

To build the Docker images, the following commands provide a guide:

docker build -t simple-server:latest . -f server/Dockerfile
docker build -t simple-client:latest . -f client/Dockerfile

The Dockerfiles will install temporarily install golang to compile the client/server. It is suggested that quick tests are perfomed outside Docker to avoid this.

⁠Advanced usage

This section summaries some non-canonical configurations supported by the Docker image when used in GNS3.

⁠802.1X wpa_supplicant

To utilise 802.1X authentication within GNS3, configure the interface ifupdown with a pre-up directive as follows:

auto eth0
iface eth0 inet static
    address 192.168.0.2
    netmask 255.255.255.0
    gateway 192.168.0.1
    pre-up wpa_supplicant -Dwired -ieth0 -c/root/wpa.conf &

Here the file /root/wpa.conf contains the credentials for the supplicant and should be present in the Docker image. As the image marks /root as persistent, the file can be manually created as follows:

$ cat - > /root/wpa.conf << EOF
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=0
eapol_version=2
ap_scan=0
network={
        key_mgmt=IEEE8021X
        eap=PEAP
        identity="user1"
        password="cisco"
        phase2="autheap=MSCHAPV2"
        eapol_flags=0
}
EOF

Then stop/start the image (or use ifdown/ifup) to get the supplicant working as desired.

More information about this configuration, including a Docker RADIUS image and using Cisco L2 devices can be found here⁠.

⁠ettercap

The image contains version 0.8.2 of ettercap⁠ built from source (as its not available currently in Alpine packages) for basic penetration testing.

⁠ISC dhclient

The :dhclient tag (both in GitHub and DockerHub) provides the ISC dhclient⁠ installed into the image. This provides a DHCP client that is vastly more configurable than the client provided by busybox (that GNS3 injects into the image to configure the network).

For example, it is not possible to use the busybox DHCP client to configure the DHCP client identifier that is sent to the DHCP server. To do this with :dhclient variant, configure the interface file with the following to set the client identifier to GNS3:

auto eth0
iface eth0 inet dhcp
	pre-up echo "send dhcp-client-identifier 0:67:6e:73:33;"  > /etc/dhcp/dhclient.conf

However, this only works in GNS3 2.2+ that has the initialisation path updated to include /sbin within the init.sh⁠ script so that it can see the dhclient installed in the image.

⁠Other bits

Copyright (c) 2019 Karim Kanso. All Rights Reserved.