How to Use Fastly's WAF with Appdome MOBILEBot Defense

Last updated November 29, 2023 by Appdome

Introduction

Web Application Firewalls (WAFs), like the one offered by Fastly, play a crucial role in protecting web applications from a wide range of cyber threats. Using Fastly’s WAF with Appdome’s MOBILEBot™ Defense solution offers app developers a streamlined approach to protect backend APIs against malicious bots and botnets, credential stuffing attacks, DDoS, invalid traffic and other automated attacks. In this guide, you’ll learn how to integrate Appdome’s Docker Image with Fastly’s WAF.

Before delving into the steps, let’s understand some of the terms used:

MTLS (Mutual Transport Layer Security): Mutual TLS (mTLS) is a method for mutual authentication in which both parties in a network connection validate the SSL certificates presented by each other against a trusted root Certificate Authority (CA) certificate.

Client Certificate: In cryptography, a client certificate is a type of digital certificate that is used by client systems to make authenticated requests to a remote server.

Safe Session: Represents sessions that are determined to be safe or not at risk of any threat.

At Risk Session: Represents sessions that are potentially under threat or have detected anomalies.

Header Payload: The data transferred in the header of HTTP requests or responses. Protecting this data ensures that it cannot be tampered with during transit.

RSA private and public keys: The RSA private key is used to generate digital signatures, and the RSA public key is used to verify digital signatures.

When Appdome’s code is integrated into the Virtual Server, it enhances the firewall’s capability to determine the validity of a session. To categorize sessions as “Safe Session” or “At Risk Session”, Appdome’s code analyzes specific headers within incoming requests: Timestamp, Nonce, and SignedMessage. The Timestamp header allows Appdome’s code to detect potential delay attacks by comparing the request’s timestamp with the server’s time. The Nonce, a unique random value, ensures the uniqueness of each request, protecting against replay attacks. The SignedMessage, typically an RSA-encrypted SHA256 hash of the timestamp, nonce, and a shared secret, ensures the integrity of the request.

Prerequisites for Using Fastly & Appdome Docker Image

For utilizing Appdome MOBILEBot Defense with Fastly, you’ll need the following:

A Fastly account with admin permissions
An AWS, GCP, or Azure server with admin permissions
An Android or iOS app secured by Appdome MOBILEBot Defense
An Appdome MOBILEBot Defense License

Getting Started with Fastly’s WAF Setup and Configuration

Note: For any additional information, please refer to Fastly’s documentation on

Upload a TLS certificate
- Cloud WAF Certificate Management
- Keep in mind that, for requests coming from Fastly’s Edge, you can use a Fastly-managed TLS certificate instead when you create a Cloud WAF instance. In this case, uploading a TLS certificate is optional.
Create a Cloud WAF Instance
- See the Fastly’s guide on how to Create a Cloud Waf Instance
Setup a Site Rule
- Learn more about Site Rules
mTLS Configuration
- Setting up Mutual TLS Authentication

IMPORTANT: It is only necessary to configure the mTLS if you have enabled mTLS in the Appdome Build process. Otherwise, skip ahead to the section “Configure Appdome’s Docker Image“

Setting up the server of your choice

When the Fastly configuration has been completed, you can begin setting up up your GCP, Azure or AWS sever or any cloud provider of your choice.

Links to Dedicated Appdome Knowledge Base articles:

GCP: For setting up a server on Google Cloud Platform and configuring it with Appdome’s Docker Image, follow this guide.
Azure: For setting up a server on Microsoft Azure and configuring it with Appdome’s Docker Image, follow this guide.
AWS: For setting up a server on Amazon Web Services and configuring it with Appdome’s Docker Image, follow this guide.

After setting up your server of choice, continue with setting up Appdome Docker Image.

Configure Appdome’s Docker Image

Appdome’s Docker Image is a custom solution to secure apps built on the Appdome platform, with the MOBILEBot Defense service enabled. This service functions within a Docker container that’s based on nginx. To facilitate its operation, users must supply an SSL certificate, a private RSA key, and designated environment variables.

Prerequisites: Familiarity with Docker and UNIX-based machines is beneficial.

How Does It Work?

The service is based on nginx and Lua, it uses the Lua module to decrypt the payload and validate the signature, then it uses the request to be proxied to the AD_TARGET route.
The module can be used with either the built-in LRU cache or with Redis, but it is recommended to use the built-in LRU to reduce the overhead of making the calls to Redis and ease the setup.

Setup

The following steps are required to set up the service.

Mount SSL certificates to the container, under /etc/ssl/certs/{ssl_certificate.crt, ssl_certificate_key.key}.
Mount CA certificate that wil be used for mTLS to the container, under /etc/nginx/client_certs/ca.crt.
Mount a private RSA key for payload decryption to the container, the pair to the public key provided in the build process. under /home/lua/private.pem
Provide AD_SERVER_NAME – domain to which the service will respond.
Provide AD_HOST – host header to override.
Provide AD_TARGET – target URL to which the request will be proxied.
Provide AD_SHARED_SECRET – shared secret used in the encrypted message.
Provide COMPROMISED_SECRET – compromised secret used in the compromised encrypted message.
Provide AD_MODULE of redis if you plan on using Redis as the cache. Make sure it is accessible from the container and is located as close as possible to the container, be it on the same network, same availability zone or same server rack.
If AD_MODULE is redis, provide AD_REDIS_HOST.

How To Run

Setup the following environment variables.

Copy the following files from your local machine onto the VM:
- Copy SSL certificates to:
```
/home/\<user\>/certs/ssl
```
- Copy the Root CA certificate to:
```
/home/\<user\>/rootCA.crt
```
- Copy a private RSA key for payload decryption, the pair to the public key provided in the build process to:
```
/home/<user>/private.pem
```
  Example command:
```
scp mykey.key ec2-user@INSTANCE_IP:/home/ec2-user/certs/ssl_certificate_key.key
```
Connect to your VM, and run the following commands:
- Pull the docker image from our public repository:
```
docker pull public.ecr.aws/n2i7f1e2/appdome-waf:basic-0.0.0
```

Note: If you are using Fastly in conjunction with either Azure, GCP or AWS, make sure to populate the <server name> field with the domain name that is registered for this service. It needs to be the same server name that was configured in your Fastly Origin server setup.

Run the docker image with the following command:

docker run -p 443:443 -p 80:80 \  
-v "$(pwd)"/certs/ssl:/etc/ssl/ \  
-v "$(pwd)"/rootCA.crt:/etc/nginx/client_certs/ca.crt \  
-e AD_SERVER_NAME= <domain to which the service will respond> \  
-e AD_TARGET= <target URL to which the request will be proxied> \  
-e AD_HOST= <host header to override> \  
-e AD_SHARED_SECRET= <shared secret used in the encrypted message> \  
-e AD_COMPROMISED_SECRET= <compromised secret used in the compromised encrypted message>  \
public.ecr.aws/n2i7f1e2/appdome-waf:basic-0.0.0

Conclusion

By integrating Fastly with your preferred Virtual Server and using Appdome’s MOBILEBot Defense, you can protect your backend APIs against malicious bots and enhance the security of mobile apps. By mastering and implementing the aforementioned configurations, businesses can safeguard and optimize their mobile app traffic.

Thank you!

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