Thursday, October 29, 2020

DDoS protection of local address space

Docker DDoS testbed describes how to use Docker Desktop to experiment with Real-time DDoS mitigation using BGP RTBH and FlowSpec. In this article, Real-time BGP route analytics are used to automatically classify address space, replacing the manually configured classification in the previous example.

Routers supporting the sFlow extended_gateway extension include BGP routing information as part of the exported telemetry stream.  Real-time DDoS mitigation using BGP RTBH and FlowSpec describes how to configure an Arista router.
sflow sample 16384
sflow polling-interval 30
sflow extension bgp
sflow destination
sflow run
Adding the highlighted command to the sFlow configuration above enables the extended_gateway extension.

The alternative if the router doesn't support the extended_gateway extension, or doesn't support sFlow at all, sFlow-RT can be configured to match up sFlow streams from switches with routes discovered via BGP from routers in order to perform the route analytics needed to automatically classify DDoS attacks. The Docker DDoS testbed has separate sFlow and BGP agents, and so requires the use of this technique.

Start a Host sFlow agent using the pre-built sflow/host-sflow image:
docker run --rm -d -e "COLLECTOR=host.docker.internal" -e "SAMPLING=10" \
--net=host -v /var/run/docker.sock:/var/run/docker.sock:ro \
--name=host-sflow sflow/host-sflow
Start ExaBGP using the pre-built sflow/exabgp image. ExaBGP connects to the sFlow-RT analytics software and displays BGP RTBH / Flowspec controls sent by sFlow-RT:
docker run --rm --name=exabgp sflow/exabgp
Run sFlow-RT:
AGENT=`docker exec host-sflow awk -F = '/agentIP/ { print $2 }' /etc/`

GW=`docker network inspect bridge -f '{{range .IPAM.Config}}{{.Gateway}}{{end}}'`

docker run --rm -p 6343:6343/udp -p 8008:8008 -p 1179:1179 --name=sflow-rt \
sflow/ddos-protect -Dddos_protect.router=$GW \
-Dddos_protect.enable.flowspec=yes -Dddos_protect.bgpgroup=local \
-Dddos_protect.router.0.agent=$AGENT \
-Dddos_protect.mode=automatic \
-Dddos_protect.udp_amplification.action=filter \
The ddos_protect.bgpgroup setting enables the automatic classification of traffic sources / destinations using the BGP data. This is the only setting required in the case where routers support the sFlow extended_gateway feature.

The ddos_protect.router.0.agent setting pairs up the sFlow agent with the first entry in the ddos_protect.router list of BGP routers. The statement, clearing the private address space from the exclusion list, is needed in this example because Docker uses private address space to connect the containers in the testbed and we don't want to ignore this traffic.

Now access the DDoS Protect application at http://localhost:8008/app/ddos-protect/html/index.html
Use ExaBGP to advertise the testbed address space:
GW=`docker network inspect bridge -f '{{range .IPAM.Config}}{{.Gateway}}{{end}}'`

SUBNET=`docker network inspect bridge -f '{{range .IPAM.Config}}{{.Subnet}}{{end}}'`

docker exec exabgp exabgp-cli announce route $SUBNET next-hop $GW
docker exec exabgp exabgp-cli announce route next-hop $GW as-path [ 65003 ]
The $SUBNET variable contains the private address space used by Docker that will be protected from attacks. The CIDR associated with AS 65003 represents external address space containing potential DDoS sources.

Finally, hping3 can be used to generate simulated DDoS attacks. Start a simulated DNS amplification attack using the pre-built sflow/hping3 image:
GW=`docker network inspect bridge -f '{{range .IPAM.Config}}{{.Gateway}}{{end}}'`

docker run --rm sflow/hping3 --flood --udp -k -a -s 53 $GW
The udp_amplification chart in the screen capture shows the traffic rising to cross the threshold and trigger the control shown in the Controls chart.

This testbed provides a convenient way to become familiar with the tools to automatically mitigate DDoS attacks. The following articles provide additional information on moving the solution into production: Real-time DDoS mitigation using BGP RTBH and FlowSpec, Pushing BGP Flowspec rules to multiple routers, and Monitoring DDoS mitigation. Real-time network and system metrics as a service provides background on the sFlow-RT analytics platform running the DDoS Protect application.

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