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Project dedicated to fight Layer 7 DDoS with proof of work, with an additional WAF and controller. Completed with full set of features and containerized for rapid and lightweight deployment.

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PoW Shield

Description

PoW Shield provides DDoS protection on OSI application layer by acting as a proxy that utilizes proof of work between the backend service and the end user. This project aims to provide an alternative to general anti-DDoS methods such as Google's ReCaptcha that has always been a pain to solve. Accessing a web service protected by PoW Shield has never been easier, simply go to the url, and your browser will do the rest of the verification automatically for you.

PoW Shield aims to provide the following services bundled in a single webapp / docker image:

  • proof of work authentication
  • ratelimiting and ip blacklisting
  • web application firewall

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Features

  • Web Service Structure
  • Proxy Functionality
  • PoW Implementation
  • Dockerization
  • IP Blacklisting
  • Ratelimiting
  • Unit Testing
  • WAF Implementation
  • Multi-Instance Syncing (Redis)
  • SSL Support

Supported via PoW Phalanx controller:

  • Multi-instance Management
  • Whitelist tokens
  • Blacklist IP syncing
  • Dynamic difficulty control
  • Dashboard

Alternate implementation in Go PoW-Shield-Go (WIP) for stress testing purposes and future optimized production version.

How it Works

So basically, PoW Shield works as a proxy in front of the actual web app/service. It conducts verification via proof-of-work and only proxies authorized traffic through to the actual server. The proxy is easily installable, and is capable of protecting low security applications with a WAF.

Here’s what happens behind the scenes when a user browses a PoW Shield-protected webservice:

  1. The server generates a random hex-encoded “prefix” and sends it along with the PoW Shield page to the client.
  2. Browser JavaScript on the client side then attempts to brute-force a “nonce” that when appended with the prefix, can produce a SHA256 hash with the number of leading zero-bits more than the “difficulty” D specified by the server. i.e. SHA256(prefix + nonce)=0…0xxxx (binary, with more than D leading 0s)
  3. Client-side JavaScript then sends the calculated nonce to the server for verification, if verification passes, the server generates a cookie for the client to pass authentication.
  4. The server starts proxying the now authenticated client traffic to the server with WAF filtering enabled.

Configuration

You can configure PoW Shield via the following methods.

  • nodejs: .env (example: .env.example)
  • docker-compose: docker-compose.yaml (example: docker-compose.example.yaml)
  • docker run: -e parameter

Environmental Variables

Variable Type Default Description
PORT General 3000 port that PoW Shield listens to
SESSION_KEY General secret key for cookie signatures, use a unique one for security reasons, or anyone can forge your signed cookies
BACKEND_URL General location to proxy authenticated traffic to, IP and URLs are both accepted(accepts protocol://url(:port) or protocol://ip(:port))
DATABASE_HOST Redis 127.0.0.1 redis service host
DATABASE_PORT Redis 6379 redis service port
DATABASE_PASSWORD Redis null redis service password
POW PoW on toggles PoW functionality on/off (if not temporary switched off, why use this project at all?)
NONCE_VALIDITY PoW 60000 specifies the maximum seconds a nonce has to be submitted to the server after generation(used to enforce difficulty change and filter out stale nonces)
DIFFICULTY PoW 13 problem difficulty, number of leading 0-bits in produced hash (0:extremely easy ~ 256:impossible, 13(default) takes about 5 seconds for the browser to calculate)
RATE_LIMIT Rate Limit on toggles ratelimit functionality on/off
RATE_LIMIT_SAMPLE_MINUTES Rate Limit 60 specifies how many minutes until statistics reset for session/ip
RATE_LIMIT_SESSION_THRESHOLD Rate Limit 100 number of requests that a single session can make until triggering token revocation
RATE_LIMIT_BAN_IP Rate Limit on toggles ip banning functionality on/off
RATE_LIMIT_IP_THRESHOLD Rate Limit 500 number of requests that a single session can make until triggering IP ban
RATE_LIMIT_BAN_MINUTES Rate Limit 15 number of minutes that IP ban persists
WAF WAF on toggles waf functionality on/off
WAF_URL_EXCLUDE_RULES WAF exclude rules to check when scanning request url, use ',' to seperate rule numbers, use '-' to specify a range (eg: 1,2-4,5,7-10)
WAF_HEADER_EXCLUDE_RULES WAF 14,33,80,96,100 exclude rules to check when scanning request header, use ',' to seperate rule numbers, use '-' to specify a range (eg: 1,2-4,5,7-10)
WAF_BODY_EXCLUDE_RULES WAF exclude rules to check when scanning request body, use ',' to seperate rule numbers, use '-' to specify a range (eg: 1,2-4,5,7-10)
SSL SSL off toggles SSL functionality on/off
SSL_CERT_PATH SSL tests/ssl/mock-cert.pem path to SSL certificate password
SSL_KEY_PATH SSL tests/ssl/mock-key.pem path to SSL key
SOCKET Socket off toggles socket functionality on/off
SOCKET_URL Socket location of PoW Phalanx controller, IP and URLs are both accepted(accepts protocol://url:port or protocol://ip:port)
SOCKET_TOKEN Socket subscription token for PoW Phalanx controller

Usage

Nodejs

Prerequisites

  • Docker ^19.0.0
  • Nodejs ^14.0.0
# Clone repository
git clone https://github.com/RuiSiang/PoW-Shield.git

# Install dependencies
npm install

# Configure settings
cp -n .env.example .env
# Edit .env
nano .env

# Transpile
npm run build

#############################################
# Run with db (redis), recommended & faster #
# install redis first                       #
# sudo apt-get install redis-server         #
#############################################
npm start
#############################################

#############################################
#        Run without db (mock redis)        #
#############################################
npm run start:standalone # linux
npm run start:standalone-win # windows
#############################################

# Test functionalities(optional)
npm test

Docker (repo)

####################################################
# Docker run with db (redis), recommended & faster #
####################################################
docker run -p 3000:3000 -e BACKEND_URL="http://example.com" -d ruisiang/pow-shield
####################################################

####################################################
#        Docker run without db (mock redis)        #
####################################################
docker run -p 3000:3000 -e BACKEND_URL="http://example.com" -e NODE_ENV="standalone" -d ruisiang/pow-shield
####################################################

####################################################
#                  Docker Compose                  #
####################################################
# Copy docker-compose.example.yaml
cp -n docker-compose.example.yaml docker-compose.yaml
# Edit docker-compose.yaml
nano docker-compose.yaml

# Start the container
docker-compose -f docker-compose.yaml up
####################################################

Stress Test

Note: This only works on non-containerized version of PoW Shield, and that your system might experience unstability when running the test.

# Start the stress test
npm run stress

# If you changed the PORT variable in .env, you should also change the target variable in the stress test script
nano scripts/stress.sh

The following tests are are conducted on a single thread of a i7-10870H CPU with a 60 second period for each concurrent parameter.

Mass GET

Concurrent Connections Avg Latency Error Rate Requests/Second
64 15.3ms 0.0000 4188
128 30.2ms 0.0000 4229
256 60.4ms 0.0000 4235
512 122.6ms 0.0142 4166
1024 261.7ms 0.1766 3894
2048 1966.5ms 0.4979 1027
4096 4685ms 0.7179 838

Nonce Flood

Concurrent Connections Avg Latency Error Rate Requests/Second
64 15.6ms N/A 4094
128 31.5ms N/A 4058
256 61.5ms N/A 4159
512 129.5ms N/A 3945
1024 264.4ms N/A 3858
2048 592.1ms N/A 3407
4096 1212.6ms N/A 3322

From the above sample, we can see that the appropriate max load estimate for PoW Shield is around 512 concurrent connections. Error rates and latencies deteriorate beyond normal acceptance afterwards. Hence in a load-balanced environment on the machine (1 PoW Shield instance on each of it's 8 cores), it should be able to handle a maximum of approximately 4096 concurrent connections (clients) at a total request rate of 32k requests/second.

References

  • Proof-of-work by Fedor Indutny (PoW utility functions)
  • Shadowd by Zesecure (WAF rules)

License

MIT