Validate subject information in a mTLS configured Ingress (Kubernetes)

In large organisations you often need additional ways to validate a client certificate since most or all certificates use the same CA and you might want to have a more fine grained validation. To use this type of extra validation we also need to setup mTLS. This is a example of how to accomplish both mTLS and an extra layer of validation

All certificates are going to be self-signed in this example, regular certificates from trusted sources like Thwate, GlobalSign and many others will naturally also work.

For Kubernetes I will use Minikube with the Ingress addon:

minikube addons enable ingress

1. First we need a server certificate

openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout server.key -out server.crt -subj "/CN=test.localdev.me/O=test.localdev.me"

This should give you two files, a server.key and a server.crt file with the private key and the certificate.

2. Lets add the certificate to the cluster via a Secret and the special type tls

kubectl create secret tls server-certificate --key server.key --cert server.crt

3. Now we need the client key and certificate. We start by creating our own “CA Authority”

openssl req -x509 -sha256 -newkey rsa:4096 -keyout ca.key -out ca.crt -days 356 -nodes -subj "/CN=My CA"

4. Add the CA to the cluster as a Secret with the type ca-secret

kubectl create secret generic ca-secret --from-file=ca.crt=ca.crt

5. A CSR for our client cert

openssl req -new -newkey rsa:4096 -keyout client.key -out client.csr -nodes -subj "/CN=MyClient"

6. Sign the CSR with our CA (same we put into the cluster)

openssl x509 -req -sha256 -days 365 -in client.csr -CA ca.crt -CAkey ca.key -set_serial 02 -out client.crt

We should now have a client.key and a client.crt ready to use

7. Another client certificate for testing the “match” function
CSR:

openssl req -new -newkey rsa:4096 -keyout client_2.key -out client_2.csr -nodes -subj "/CN=MyOtherClient"

Sign:

openssl x509 -req -sha256 -days 365 -in client_2.csr -CA ca.crt -CAkey ca.key -set_serial 02 -out client_2.crt

8. Now we need an application to call. We create one with the Deployment and Service below:

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: mywebserver
  name: mywebserver
spec:
  replicas: 1
  selector:
    matchLabels:
      app: mywebserver
  template:
    metadata:
      labels:
        app: mywebserver
    spec:
      containers:
      - image: httpd
        name: httpd
        ports:
        - containerPort: 80

---

apiVersion: v1
kind: Service
metadata:
  labels:
    app: my-service
  name: my-service
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: mywebserver

8. Now we need to configure the Ingress for mTLS and our extra layer of authentication:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    nginx.ingress.kubernetes.io/auth-tls-pass-certificate-to-upstream: "true"
    nginx.ingress.kubernetes.io/auth-tls-secret: default/ca-secret
    nginx.ingress.kubernetes.io/auth-tls-verify-client: "on"
    nginx.ingress.kubernetes.io/auth-tls-verify-depth: "1"
    nginx.ingress.kubernetes.io/auth-tls-match-cn: "CN=MyClient"
  name: mtls-ingress
  namespace: default
spec:
  ingressClassName: nginx
  rules:
  - host: test.localdev.me
    http:
      paths:
      - backend:
          service:
            name: my-service
            port:
              number: 80
        path: /
        pathType: Prefix
  tls:
  - hosts:
    - test.localdev.me
    secretName: server-certificate

Here we added the nginx.ingress.kubernetes.io/auth-tls-match-cn for our extra validation. In this case we are looking for a “CN=MyClient” property in the Subject part of the client certificate. If the string is found we continue the communication between client and server, if not then the connection will be terminated with a HTTP 403 error

9. Time to test our mTLS setup with extra validation
First we need to setup a port binding to port 443 on our local machine

sudo kubectl port-forward -n ingress-nginx service/ingress-nginx-controller 443:443

and now we can test with a call with our client certificate and key

curl -k -v https://test.localdev.me/ --key client.key --cert client.crt

If everything is working we should get “It works!” from the Web Server

10. Now we are going to test the “match” function. Remember that both client.crt and client_2.crt uses the same CA so without the “auth-tls-match-dn” function they would both be accepted

curl -k -v https://test.localdev.me/ --key client_2.key --cert client_2.crt

This should fail and you should now get a HTTP 403 (Forbidden)

NOTE: A match with “CN=My Client” does not work! Spaces does not work when matching like this

Tested in Minikube 1.26.0 and with OpenSSL 1.1.1f on Ubuntu 20.08

Apache Camel CXF gives you “org.apache.cxf.service.factory.ServiceConstructionException: Could not find portType named {<some namespace>}<some service>PortType”

I got this when implementing a SOAP service from a provided wsdl. I hope I would not done the same mistake if I wrote the wsdl myself, but we will never know for sure 😉

Now to the solution. You probably have something like this in your code (Apache Camel in a SpringBoot application)

...
@Component
public class CurrencyRoute extends RouteBuilder {

    @Override
    public void configure() throws Exception {
        from("cxf:bean:currencyLookupAdapterEndpoint")
            .log("Body: ${body}");
    }

    @Bean
    private CxfEndpoint currencyLookupAdapterEndpoint() {
        final CxfEndpoint cxfEndpoint = new CxfEndpoint();
        cxfEndpoint.setWsdlURL("currencies.wsdl");
        cxfEndpoint.setAddress("/getCurrencies");

        // Set the Service Class
        cxfEndpoint.setServiceClass(CurrenciesResponderService.class);

        cxfEndpoint.setProperties(new HashMap<>());
        cxfEndpoint.getProperties().put("schema-validation-enabled", "true");
        return cxfEndpoint;
    }
}

In the currencies.wsdl I had a CurrenciesResponderService and a CurrenciesResponderInterface.
If I choose the CurrenciesResponderService.class as the ServiceClass I got the error below:

org.apache.cxf.service.factory.ServiceConstructionException: Could not find portType named {<some namespace>}<some service>PortType

and if I choose the CurrenciesResponderInterface.class instead the application started without the error 🙂

Tested on Apache Camel v3.17 and SpringBoot v3.2.0

Setup a TLS enabled Ingress in Kubernetes

TLS is a very common security mechanism on web servers through out the Internet. It creates a transport tunnel of encrypted data between the server and client. This tunnel is created with the help of the server certificate and is dependent of that the client trusts the server. We are now going to see an example of how to set this up in the Ingress component of Kubernetes

All certificates are going to be self-signed in this example, regular certificates from trusted sources like Thwate, GlobalSign and many others will also work.

For Kubernetes I will use Minikube with the Ingress addon:

minikube addons enable ingress

1. We start with creating the server certificate

openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout server.key -out server.crt -subj "/CN=test.localdev.me/O=test.localdev.me"

This should give you two files, a server.key and a server.crt file with the private key and the certificate to present to clients trying to connect.
NOTE: the “domain” test.localdev.me will normally return 127.0.0.1 automatically which makes it perfect to use in cases like this

2. Lets add the certificate to the cluster via a Secret and the special type tls

kubectl create secret tls server-certificate --key server.key --cert server.crt

3. Now we need an application to call. We create one with the Deployment below:

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: mywebserver
  name: mywebserver
spec:
  replicas: 1
  selector:
    matchLabels:
      app: mywebserver
  template:
    metadata:
      labels:
        app: mywebserver
    spec:
      containers:
      - image: httpd
        name: httpd
        ports:
        - containerPort: 80

4. A Service to expose the application to the cluster

apiVersion: v1
kind: Service
metadata:
  labels:
    app: my-service
  name: my-service
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: mywebserver

5. A Ingress to handle the authentication

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: mtls-ingress
  namespace: default
spec:
  ingressClassName: nginx
  rules:
  - host: test.localdev.me
    http:
      paths:
      - backend:
          service:
            name: my-service
            port:
              number: 80
        path: /
        pathType: Prefix
  tls:
  - hosts:
    - test.localdev.me
    secretName: server-certificate

6. Time to test our TLS setup
First we need to setup a port binding to port 443 on our local machine

sudo kubectl port-forward -n ingress-nginx service/ingress-nginx-controller 443:443

and now we can test with curl and the test.localdev.me domain

curl -k -v https://test.localdev.me/

If everything is working we should get “It works!” from the Web Server

Tested in Minikube 1.26.0 and with OpenSSL 1.1.1f on Ubuntu 20.08