A couple of months ago, I stumbled upon this list of 16 practices to secure your API:

1. Authentication 🕵️️ - Verifies the identity of users accessing APIs.
2. Authorization 🚦 - Determines permissions of authenticated users.
3. Data Redaction 🖍️ - Obscures sensitive data for protection.
4. Encryption 🔒 - Encodes data so only authorized parties can decode it.
5. Error Handling ❌ - Manages responses when things go wrong, avoiding revealing sensitive info.
6. Input Validation & Data Sanitization 🧹 - Checks input data and removes harmful parts.
7. Intrusion Detection Systems 👀 - Monitor networks for suspicious activities.
8. IP Whitelisting 📝 - Permits API access only from trusted IP addresses.
9. Logging and Monitoring 🖥️ - Keeps detailed logs and regularly monitors APIs.
10. Rate Limiting ⏱️ - Limits user requests to prevent overload.
11. Secure Dependencies 📦 - Ensures third-party code is free from vulnerabilities.
12. Security Headers 📋 - Enhances site security against types of attacks like XSS.
13. Token Expiry ⏳ - Regularly expiring and renewing tokens prevents unauthorized access.
14. Use of Security Standards and Frameworks 📘 - Guides your API security strategy.
15. Web Application Firewall 🔥 - Protects your site from HTTP-specific attacks.
16. API Versioning 🔄 - Maintains different versions of your API for seamless updates.

While it's debatable whether some points relate to security, e.g.,, versioning, the list is a good starting point anyway. In this two-post series, I'd like to describe how we can implement each point with Apache APISIX (or not).

Authentication

Authentication is about identifying yourself with a system. It requires a proof.

Apache APISIX provides two kinds of authentications: internal, with APISIX checking credentials, and external, when delegated to a third party. All authentication mechanisms work via plugins. Here's the current list of available authentication plugins.

APISIX assigns authenticated calls to a consumer. For example, we can create a consumer authenticated with the key-auth plugin:

consumers:
  - username: john
    plugins:
      key-auth:
        key: mykey

Every request containing the header apikey with the key mykey will be assigned to the consumer john.

Authorization

Authentication alone isn't enough. Once a request to a URL has been authenticated, we need to decide whether it's allowed to proceed further. That's the role of authorization.

Authorization [...] is the function of specifying access rights/privileges to resources, which is related to general information security and computer security, and to access control in particular. More formally, "to authorize" is to define an access policy.

-- Authorization on Wikipedia

Apache APISIX implements authorization mainly via the consumer-restriction plugin. Here's the most straightforward usage of the consumer-restriction plugin:

consumers:
  - username: johndoe                     #1
    plugins:
      keyauth:
        key: mykey

routes:
  - upstream_id: 1                        #2
    plugins:
      keyauth: ~
      consumer-restriction:
        whitelist:                        #3
          - johndoe               

1. Define a consumer
2. Reference an already existing upstream
3. Only allows defined consumers to access the route

Most real-world authorization models avoid binding an identity directly to a permission. They generally bind a group (and even a role) so that it becomes easier to manage many identities. Apache APISIX provides the consumer group abstraction for this.

consumer_groups:
  - id: accountants                      #1

consumers:
  - username: johndoe
    group_id: accountants                #2
    plugins:
      keyauth:
        key: mykey

routes:
  - upstream_id: 1
    plugins:
      keyauth: ~
      consumer-restriction:
        type: consumer_group_id          #3
        whitelist:
          - accountants               

1. Define a consumer group
2. Assign the consumer to the previously defined consumer group
3. Restrict the access to members of the defined consumer group, i.e., accountants

Input validation

With Apache APISIX, you can define a set of JSON schemas and validate a request against any of them. My colleague Navendu has written an exhaustive blog post on the subject: Your API Requests Should Be Validated.

I think it's not the API Gateway's responsibility to handle request validation. Each upstream has specific logic, and moving the validation responsibility from the upstream to the Gateway ties the latter to the logic for no actual benefit.

In any case, the checkbox is ticked.

IP Whitelisting

Apache APISIX implements IP Whitelisting via the ip-restriction plugin. You can define either regular IPs or CIDR blocks.

routes:
  - upstream_id: 1
    plugins:
      ip-restriction:
        whitelist:
          - 127.0.0.1
          - 13.74.26.106/24               

Logging and Monitoring

Logging and Monitoring fall into the broader Observability category, also encompassing Tracing. Apache APISIX offers a broad range of Observability plugins in each category.

Rate Limiting

Rate Limiting protects upstreams from Distributed Denial of Services attacks, a.k.a DDoS. It's one of the main features of reverse proxies and API Gateways. APISIX implements rate limiting through three different plugins:

• The limit-conn Plugin limits the number of concurrent requests to your services
• The limit-req Plugin limits the number of requests to your service using the leaky bucket algorithm
• The limit-count Plugin limits the number of requests to your service by a given count per time. The plugin is using Fixed Window algorithm

Let's use limit-count for the sake of example:

routes:
  - upstream_id: 1
    plugins:
      limit-count:
        count: 10
        time_window: 1
        rejected_code: 429

The above configuration snippet protects the upstream from being hit by more than ten requests per second. It applies to every IP address because of the default configuration. The complete snippet would look like the following:

routes:
  - upstream_id: 1
    plugins:
      limit-count:
        count: 10
        time_window: 1
        rejected_code: 429
        key_type: var
        key: remote_addr

When dealing with APIs, there's a considerable chance you want to differentiate between your clients. Some might get a better rate for different reasons: they paid a premium offer; they are considered strategic; they are internal clients, etc. The same consumer could also use different IP addresses because they run on various machines with other APIs. Allowing the same consumer more calls because they execute their requests on a distributed infrastructure would be unfair.

As it stands, the IP is not a great way to assign the limit; we prefer to use a named consumer or, even better, a consumer group. It's perfectly possible with APISIX:

consumer_groups:
  - id: basic
    plugins:
      limit-count:
        count: 1
        time_window: 1
        rejected_code: 429
  - id: premium
    plugins:
      limit-count:
        count: 10
        time_window: 1
        rejected_code: 429

consumers:
  - username: johndoe
    group_id: basic
    plugins:
      keyauth:
        key: mykey1
  - username: janedoe
    group_id: premium
    plugins:
      keyauth:
        key: mykey2

routes:
  - upstream_id: 1
    plugins:
      key-auth: ~

Now, johndoe can only send a request every second, as he's part of the basic plan, while janedoe can request ten times as much as part of the premium plan.

Conclusion

We've seen how to configure Apache APISIX to secure your APIs against 7 of the 16 rules in the original list. The rules left could be less straightforward to implement; we will cover them in the second installment.

Originally published at A Java Geek on February 18^th, 2024