External Authorization

6 minute read

This task provides instructions for configuring external authentication.

External authorization calls an external HTTP or gRPC service to check whether an incoming HTTP request is authorized or not. If the request is deemed unauthorized, then the request will be denied with a 403 (Forbidden) response. If the request is authorized, then the request will be allowed to proceed to the backend service.

Envoy Gateway introduces a new CRD called SecurityPolicy that allows the user to configure external authorization. This instantiated resource can be linked to a Gateway and HTTPRoute resource.

Prerequisites

Follow the steps from the Quickstart to install Envoy Gateway and the example manifest. Before proceeding, you should be able to query the example backend using HTTP.

Verify the Gateway status:

kubectl get gateway/eg -o yaml

HTTP External Authorization Service

Installation

Install a demo HTTP service that will be used as the external authorization service:

kubectl apply -f https://raw.githubusercontent.com/envoyproxy/gateway/latest/examples/kubernetes/ext-auth-http-service.yaml

Create a new HTTPRoute resource to route traffic on the path /myapp to the backend service.

cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: myapp
spec:
  parentRefs:
  - name: eg
  hostnames:
  - "www.example.com"
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /myapp
    backendRefs:
    - name: backend
      port: 3000   
EOF

Save and apply the following resource to your cluster:

---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: myapp
spec:
  parentRefs:
  - name: eg
  hostnames:
  - "www.example.com"
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /myapp
    backendRefs:
    - name: backend
      port: 3000

Verify the HTTPRoute status:

kubectl get httproute/myapp -o yaml

Configuration

Create a new SecurityPolicy resource to configure the external authorization. This SecurityPolicy targets the HTTPRoute “myApp” created in the previous step. It calls the HTTP external authorization service “http-ext-auth” on port 9002 for authorization. The headersToBackend field specifies the headers that will be sent to the backend service if the request is successfully authorized.

cat <<EOF | kubectl apply -f -
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: SecurityPolicy
metadata:
  name: ext-auth-example
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: myapp
  extAuth:
    http:
      backendRef:
        name: http-ext-auth
        port: 9002
      headersToBackend: ["x-current-user"]
EOF

Save and apply the following resource to your cluster:

---
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: SecurityPolicy
metadata:
  name: ext-auth-example
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: myapp
  extAuth:
    http:
      backendRef:
        name: http-ext-auth
        port: 9002
      headersToBackend: ["x-current-user"]

Verify the SecurityPolicy configuration:

kubectl get securitypolicy/ext-auth-example -o yaml

Testing

Ensure the GATEWAY_HOST environment variable from the Quickstart is set. If not, follow the Quickstart instructions to set the variable.

echo $GATEWAY_HOST

Send a request to the backend service without Authentication header:

curl -v -H "Host: www.example.com" "http://${GATEWAY_HOST}/myapp"

You should see 403 Forbidden in the response, indicating that the request is not allowed without authentication.

* Connected to 172.18.255.200 (172.18.255.200) port 80 (#0)
> GET /myapp HTTP/1.1
> Host: www.example.com
> User-Agent: curl/7.68.0
> Accept: */*
...
< HTTP/1.1 403 Forbidden
< date: Mon, 11 Mar 2024 03:41:15 GMT
< x-envoy-upstream-service-time: 0
< content-length: 0
< 
* Connection #0 to host 172.18.255.200 left intact

Send a request to the backend service with Authentication header:

curl -v -H "Host: www.example.com" -H "Authorization: Bearer token1" "http://${GATEWAY_HOST}/myapp"

The request should be allowed and you should see the response from the backend service. Because the x-current-user header from the auth response has been sent to the backend service, you should see the x-current-user header in the response.

"X-Current-User": [
   "user1"
  ],

GRPC External Authorization Service

Installation

Install a demo gRPC service that will be used as the external authorization service. The demo gRPC service is enabled with TLS and a BackendTLSConfig is created to configure the communication between the Envoy proxy and the gRPC service.

Note: TLS is optional for HTTP or gRPC external authorization services. However, enabling TLS is recommended for enhanced security in production environments.

kubectl apply -f https://raw.githubusercontent.com/envoyproxy/gateway/latest/examples/kubernetes/ext-auth-grpc-service.yaml

The HTTPRoute created in the previous section is still valid and can be used with the gRPC auth service, but if you have not created the HTTPRoute, you can create it now.

Create a new HTTPRoute resource to route traffic on the path /myapp to the backend service.

cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: myapp
spec:
  parentRefs:
  - name: eg
  hostnames:
  - "www.example.com"
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /myapp
    backendRefs:
    - name: backend
      port: 3000   
EOF

Save and apply the following resource to your cluster:

---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: myapp
spec:
  parentRefs:
  - name: eg
  hostnames:
  - "www.example.com"
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /myapp
    backendRefs:
    - name: backend
      port: 3000

Verify the HTTPRoute status:

kubectl get httproute/myapp -o yaml

Configuration

Update the SecurityPolicy that was created in the previous section to use the gRPC external authorization service. It calls the gRPC external authorization service “grpc-ext-auth” on port 9002 for authorization.

cat <<EOF | kubectl apply -f -
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: SecurityPolicy
metadata:
  name: ext-auth-example
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: myapp
  extAuth:
    grpc:
      backendRef:
        name: grpc-ext-auth
        port: 9002
EOF

Save and apply the following resource to your cluster:

---
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: SecurityPolicy
metadata:
  name: ext-auth-example
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: myapp
  extAuth:
    grpc:
      backendRef:
        name: grpc-ext-auth
        port: 9002

Verify the SecurityPolicy configuration:

kubectl get securitypolicy/ext-auth-example -o yaml

Because the gRPC external authorization service is enabled with TLS, a BackendTLSConfig needs to be created to configure the communication between the Envoy proxy and the gRPC auth service.

cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1alpha2
kind: BackendTLSPolicy
metadata:
  name: grpc-ext-auth-btls
spec:
  targetRef:
    group: ''
    kind: Service
    name: grpc-ext-auth
    sectionName: "9002"
  tls:
    caCertRefs:
    - name: grpc-ext-auth-ca
      group: ''
      kind: ConfigMap
    hostname: grpc-ext-auth
EOF

Save and apply the following resource to your cluster:

---
apiVersion: gateway.networking.k8s.io/v1alpha2
kind: BackendTLSPolicy
metadata:
  name: grpc-ext-auth-btls
spec:
  targetRef:
    group: ''
    kind: Service
    name: grpc-ext-auth
    sectionName: "9002"
  tls:
    caCertRefs:
    - name: grpc-ext-auth-ca
      group: ''
      kind: ConfigMap
    hostname: grpc-ext-auth

Verify the BackendTLSPolicy configuration:

kubectl get backendtlspolicy/grpc-ext-auth-btls -o yaml

Testing

Ensure the GATEWAY_HOST environment variable from the Quickstart is set. If not, follow the Quickstart instructions to set the variable.

echo $GATEWAY_HOST

Send a request to the backend service without Authentication header:

curl -v -H "Host: www.example.com" "http://${GATEWAY_HOST}/myapp"

You should see 403 Forbidden in the response, indicating that the request is not allowed without authentication.

* Connected to 172.18.255.200 (172.18.255.200) port 80 (#0)
> GET /myapp HTTP/1.1
> Host: www.example.com
> User-Agent: curl/7.68.0
> Accept: */*
...
< HTTP/1.1 403 Forbidden
< date: Mon, 11 Mar 2024 03:41:15 GMT
< x-envoy-upstream-service-time: 0
< content-length: 0
< 
* Connection #0 to host 172.18.255.200 left intact

Send a request to the backend service with Authentication header:

curl -v -H "Host: www.example.com" -H "Authorization: Bearer token1" "http://${GATEWAY_HOST}/myapp"

Clean-Up

Follow the steps from the Quickstart to uninstall Envoy Gateway and the example manifest.

Delete the demo auth services, HTTPRoute, SecurityPolicy and BackendTLSPolicy:

kubectl delete -f https://raw.githubusercontent.com/envoyproxy/gateway/latest/examples/kubernetes/ext-auth-http-service.yaml
kubectl delete -f https://raw.githubusercontent.com/envoyproxy/gateway/latest/examples/kubernetes/ext-auth-grpc-service.yaml
kubectl delete httproute/myapp
kubectl delete securitypolicy/ext-auth-example
kubectl delete backendtlspolicy/grpc-ext-auth-btls

Next Steps

Checkout the Developer Guide to get involved in the project.

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Last modified May 3, 2024: fix helm IfNotPresent (#3320) (1e4640a)