OPA server as a sidecar
Enforce Open Policy Agent (OPA) policies through an OPA server that runs as a sidecar to the external auth server.
You can enable an OPA server to run as a sidecar to the Gloo external auth service. Then, you can administer an OPA server for extended use cases such as bundling. With bundling, your Rego rules can live as a signed bundle in an external, central location, such as an AWS S3 bucket to meet your internal security requirements. This sidecar approach increases the resources needed in the external auth server pod, but works better at scale and provides more OPA-native support for teams familiar with administering an OPA server. You also get the OPA-Envoy plugin API as part of the Gloo external auth service.
Other OPA options:
- Load Rego rules as Kubernetes config maps to the Gloo external auth service OPA module.
- Instead of deploying a sidecar, you can bring your own OPA server.
Support for running the OPA server sidecar is a beta feature available in Gloo Mesh Enterprise 2.4.1 and later. For more information, see Gloo feature maturity.
If you import or export resources across workspaces, your policies might not apply. For more information, see Import and export policies.
About the OPA sidecar
Gloo Mesh Enterprise can deploy an OPA sidecar server for you. After, you are responsible for administering the server per OPA best practices.
The following diagram and the steps in the rest of this guide show how you can set up an OPA server sidecar.
- A user sends a request that the ingress gateway receives. The request matches a route that is protected by an external auth policy that uses OPA.
- The ingress gateway sends the request to the external auth service for an authorization decision.
- The external auth service passes the request through to the OPA server sidecar to make an authorization decision.
- The OPA server sidecar loads the OPA config of Rego rules from a bundle in a cloud provider. The OPA server uses these Rego rules to make an authorization decision on the request. You can provide the OPA config via a YAML file during the Helm installation, or subsequently in a Kubernetes config map. Note that the request does not trigger loading the rules. You must restart the OPA server each time that you update the OPA config.
- The OPA server returns the authorization decision to the external auth service, which returns the authorization decision to the ingress gateway.
- The ingress gateway handles the request per the authorization decision.
- If unauthorized, the ingress gateway denies the request.
- If authorized, the ingress gateway forwards the request to the destination workload.
Clear route cache
The Envoy proxy in your sidecar instance keeps a route cache in memory of precomputed routing decisions to help speed up performance. When the sidecar gets a request, it can check the route cache to decide where to send the request. When the route cache is cleared, Gloo recomputes the routing rules. This way, any old and potentially conflicting data from the initial request is cleared.
When running the OPA server as a sidecar to the external auth server, you cannot use the clearRouteCache
option on an external auth policy to force a routing decision. Instead, you can set the clearRouteCache
option on the external auth server. However, keep in mind that this setting then applies to all external auth policies that the external auth server serves.
Before you begin
This guide assumes that you use the same names for components like clusters, workspaces, and namespaces as in the getting started. If you have different names, make sure to update the sample configuration files in this guide.
Complete the multicluster getting started guide to set up the following testing environment.
- Three clusters along with environment variables for the clusters and their Kubernetes contexts.
- The Gloo
meshctl
CLI, along with other CLI tools such askubectl
andistioctl
. - The Gloo management server in the management cluster, and the Gloo agents in the workload clusters.
- Istio installed in the workload clusters.
- A simple Gloo workspace setup.
- Install Bookinfo and other sample apps.
Make sure that the external auth service is installed and running. If not, install the external auth service in your Gloo environment.
kubectl get pods --context $REMOTE_CONTEXT1 -A -l app=ext-auth-service
Bundle Rego rules
Prepare OPA configuration for the OPA server by creating, bundling, and referring to a Rego policy with the rules you want to enforce.
For help writing Rego policies, refer to the OPA policy language docs. If you use the OPA-Envoy plugin API, the OPA docs has a policy primer. For example, you might create an output document to organize the results of a decision or to gather all the metadata of an object like an API key. Then, you can test your Rego policies in the Rego playground.
Create a Rego policy file in a
rego
directory with the rules you want to enforce with OPA. The following policy allowsGET
andPOST
HTTP requests and denies requests to the/status
endpoint.mkdir rego cat <<EOF > rego/policy.rego package httpbin import input.http_request # deny requests by default default allowed = false # set allowed to true if no error message allowed { not body } # return result and error message allow["allowed"] = allowed allow["body"] = body # main policy logic, with error message per rule body = "HTTP verb is not allowed" { not http_verb_allowed } else = "Path is not allowed" { not path_allowed } # allow only GET and POST requests http_verb_allowed { {"GET", "POST"}[_] == http_request.method } # deny requests to /status endpoint path_allowed { not startswith(http_request.path, "/status") } EOF
Create another Rego policy. The following policy uses metadata that is enabled by the OPA-Envoy plugin API. This example shows how you can use OPA to evaluate and transform responses based on request metadata.
- Check requests for an
api-key
header, with valid API keys either set to the test value oftest-apikey
or located indata.apikeys
. The API keys indata.apikeys
are loaded as part of the data bundle. - If the request is authorized, the
api-key
header is removed. - If the request is not authorized, the body is set to
Unauthorized Request
and returned to the client with a 403 status code, along with areject-reason
response header. - In both cases, the
x-response-header
is added.
cat <<EOF > rego/apikey_policies.rego package apikey_policies import future.keywords.if default allow := false allow { api_key_allowed } api_key_allowed { api_key == "test-apikey" } api_key_allowed { has_key(data.apikeys, api_key) } api_key := input.http_request.headers["api-key"] http_status := 200 { allow } http_status := 403 { not allow } body := "Unauthorized Request" { http_status == 403 } headers["x-ext-auth-allow"] := "yes" if api_key_allowed headers["x-validated-by"] := "security-checkpoint" if api_key_allowed request_headers_to_remove := ["api-key"] response_headers_to_add["x-response-header"] := "for-client-only" response_headers_to_add["reject-reason"] := "unauthorized" if not allow # Helper function to check if a dictionary has a key has_key(dict, k) { dict[k] } EOF
- Check requests for an
Use the
opa
CLI to bundle your Rego rules. The output of the command is abundle.tar.gz
compressed file in your current directory. For more information, see the OPA docs.Signed policies: To make sure that your Rego policies come from a trusted source, you can add a signature to your bundle. For more information, see the OPA docs.opa build -b rego/
Store your bundle in a supported cloud provider. For options and steps, see the OPA implementation docs.
Example command for Google Cloud: Make sure to update the
${BUCKET_NAME}
with the name of thegcs
bucket.gsutil cp bundle.tar.gz gs://${BUCKET_NAME}/
Create a YAML file with your OPA config. For more information, see the OPA implementation docs.
Review the following table to understand this configuration.cat > config.yaml - <<EOF services: gcs: url: https://storage.googleapis.com/storage/v1/b/${BUCKET_NAME}/o bundles: bundle: service: gcs resource: 'bundle.tar.gz?alt=media' EOF
Setting Description services
Provide the details of the cloud service where the bundle is located. In this example, the bundle is in a Google Cloud Storage ( gcs
) bucket. Make sure to update the${BUCKET_NAME}
with the name of thegcs
bucket. For quick testing, you can use a bucket with a public URL. Or, you can also set up secure access with thecredentials
settings.bundles
Provide the details about the particular bundle that you want to use. In this example, the bundle is the bundle.tar.gz
bundle that you previously created.Other settings If you use other features, you can configure those settings in the config map. Common settings include signed bundles and returning decision logs. For more information, see the OPA implementation docs.
Upgrade the external auth server to run the OPA sidecar
Deploy the OPA server sidecar by upgrading the external auth service in your existing Gloo Mesh Enterprise installation. You can also set up the sidecar when you first install Gloo Mesh Enterprise.
The following steps upgrade an existing Helm release to add the OPA server as a sidecar to the external auth service. The steps do not upgrade the Gloo management server or agent versions or otherwise change the components.
Check the Helm releases in your cluster. Depending on your installation method, you either have only a main installation release (such as
gloo-platform
), or a main installation and a separate add-ons release (such asgloo-agent-addons
), in addition to your CRDs release.helm ls -A --kube-context ${REMOTE_CONTEXT1}
Get your current installation values.
If you have only one release for your installation, get those values. Note that your Helm release might have a different name.
helm get values gloo-platform -n gloo-mesh -o yaml --kube-context ${REMOTE_CONTEXT1} > gloo-single.yaml open gloo-single.yaml
If you have a separate add-ons release, get those values.
helm get values gloo-agent-addons -n gloo-mesh -o yaml --kube-context ${REMOTE_CONTEXT1} > gloo-agent-addons.yaml open gloo-agent-addons.yaml
Add or edit the following settings to deploy the OPA server sidecar as part of the external auth service. For other settings, see the
opaServer
settings in the Helm reference docs.extAuthService: enabled: true extAuth: opaServer: enabled: true configYaml: ""
Upgrade your Helm release with the OPA server sidecar. Be sure to include the OPA config file that you previously created.
If you have only one release for your installation, upgrade the
gloo-platform
release. Note that your Helm release might have a different name.helm upgrade gloo-platform gloo-platform/gloo-platform --kube-context ${REMOTE_CONTEXT1} \ --namespace gloo-mesh \ -f gloo-single.yaml \ --set-file configYaml=config.yaml \ --version $GLOO_VERSION
If you have a separate add-ons release, upgrade the
gloo-agent-addons
release.helm upgrade gloo-agent-addons gloo-platform/gloo-platform --kube-context ${REMOTE_CONTEXT1} \ --namespace gloo-mesh \ -f gloo-agent-addons.yaml \ --set-file configYaml=config.yaml \ --version $GLOO_VERSION
This Helm upgrade loads the initial OPA config for the OPA server to test an example policy. Later, if you want to update the OPA config, see Update OPA config.Verify that the external auth service is healthy, with 2 containers ready.
kubectl get po -n gloo-mesh -l app=ext-auth-service --context $REMOTE_CONTEXT1
NAME READY STATUS RESTARTS AGE ext-auth-service-6546584c8d-w9s4l 2/2 Running 0 97s
If the OPA sidecar is not healthy, the external auth service cannot enter a healthy running state, either. Continue to the next step to check the OPA server.Check that the OPA server is healthy and accepted the config. Note the following example command pipes the output to
jq
for readability.- Confirm that the OPA server loaded the bundle that you referred to in the config map.
- Confirm the health checks return a
200
response status. - If the OPA server is not healthy, try the OPA troubleshooting docs. Common errors include misconfiguration such as the wrong credentials to download a bundle or the wrong URL to the storage bucket.
kubectl logs -n gloo-mesh deploy/ext-auth-service -c opa-auth --context $REMOTE_CONTEXT1 | jq
{ "level": "info", "msg": "Bundle loaded and activated successfully. Etag updated to CMzq8eO/p4EDEAE=.", "name": "httpbin", "plugin": "bundle", "time": "2023-09-20T15:54:47Z" } { "client_addr": "@", "level": "info", "msg": "Received request.", "req_id": 2, "req_method": "GET", "req_path": "/health", "time": "2023-09-20T15:54:48Z" } { "client_addr": "@", "level": "info", "msg": "Sent response.", "req_id": 2, "req_method": "GET", "req_path": "/health", "resp_bytes": 3, "resp_duration": 0.499848, "resp_status": 200, "time": "2023-09-20T15:54:48Z" }
Create the OPA external auth policy
Create the Gloo external auth resources to enforce the OPA policy.
Create an external auth server to use for your policy.
kubectl apply --context $REMOTE_CONTEXT1 -f - <<EOF apiVersion: admin.gloo.solo.io/v2 kind: ExtAuthServer metadata: name: opa-ext-auth-server namespace: httpbin spec: destinationServer: port: number: 8083 ref: cluster: $REMOTE_CLUSTER1 name: ext-auth-service namespace: gloo-mesh EOF
Create an external auth policy that uses the OPA config map.
This policy currently does not support selecting VirtualDestinations as a destination.
kubectl apply --context ${REMOTE_CONTEXT1} -f - <<EOF
apiVersion: security.policy.gloo.solo.io/v2
kind: ExtAuthPolicy
metadata:
name: opa-sidecar
namespace: httpbin
spec:
applyToDestinations:
- selector:
labels:
app: httpbin
config:
server:
name: opa-ext-auth-server
namespace: httpbin
glooAuth:
configs:
- opaServerAuth:
package: httpbin
ruleName: allow/allowed
- opaServerAuth:
package: apikey_policies
EOF
Review the following table to understand this configuration. For more information, see the API reference.
Setting | Description |
---|---|
applyToDestinations | Use labels to apply the policy to destinations. Destinations might be a Kubernetes service, VirtualDestination, or ExternalService (if supported by the policy). If you do not specify any destinations or routes, the policy applies to all destinations in the workspace by default. If you do not specify any destinations but you do specify a route, the policy applies to the route but to no destinations. |
server | The external auth server to use for the policy. |
opaServerAuth | Configure the OPA server sidecar authentication details. |
package | Refer to the package in the Rego bundle that you set up in the config map earlier, such as httpbin from the policy.rego file. |
ruleName | Select the Rego rules within the bundle that you want to enforce for this OPA external auth policy.
|
Verify the OPA external auth policy
Verify that the Rego rules are evaluated by the OPA server and enforced by the external auth service.
Confirm that the external auth policy’s state is
ACCEPTED
.kubectl get -n httpbin ExtAuthPolicy opa-sidecar -o yaml --context $REMOTE_CONTEXT1
Send an allowed request to the
httpbin
app, such as aGET bytes
request with thetest-apikey
API key.Create a temporary curl pod in thebookinfo
namespace, so that you can test the app setup. You can also use this method in Kubernetes 1.23 or later, but an ephemeral container might be simpler.- Create the curl pod.
kubectl run -it -n httpbin --context ${REMOTE_CONTEXT1} curl --image=curlimages/curl:7.73.0 --rm -- sh
- Send a request to the ratings app.
curl -H "X-httpbin: true" -H "api-key: test-apikey" -v http://httpbin:8000/bytes/5
In the response, you get a successful 200 status code. Also notice that the
api-key
header is removed and thex-response-header
is added, as specified in the Rego policy.* Trying 3.130.169.185:80... * Connected to $INGRESS_GW_IP port 80 (#0) > GET /bytes/5 HTTP/1.1 > Host: www.example.com:80 > User-Agent: curl/8.1.2 > Accept: */* > X-httpbin: true > api-key: test-apikey > HTTP/1.1 200 OK access-control-allow-credentials: true access-control-allow-origin: * content-type: application/octet-stream date: Thu, 16 Nov 2023 15:57:15 GMT content-length: 5 x-envoy-upstream-service-time: 2 x-response-header: for-client-only server: istio-envoy * Connection #0 to host $INGRESS_GW_IP left intact D?d?L%
- Create the curl pod.
Repeat the request, but remove the
test-apikey
API key. You get a 403 response because the request must meet all the Rego policy requirements to succeed.curl -H "X-httpbin: true" -v http://httpbin:8000/bytes/5
Notice that the response includes the transformations that you specified in the Rego policy, particularly:
- The
x-response-header: for-client-only
is added to the response. - The
reject-reason: unauthorized
is added to the response. - The body returned says
Unauthorized Request
.
* Connected to $INGRESS_GW_IP port 80 (#0) > GET /bytes/5 HTTP/1.1 > Host: www.example.com:80 > User-Agent: curl/8.1.2 > Accept: */* > X-httpbin: true HTTP/1.1 403 Forbidden reject-reason: unauthorized x-response-header: for-client-only content-length: 20 content-type: text/plain date: Thu, 16 Nov 2023 15:36:05 GMT server: istio-envoy * Connection #0 to host $INGRESS_GW_IP left intact Unauthorized Request
- The
Send the request again along a path that is not allowed by the OPA policy, such as
/status
. Now, the request is blocked with a404 Not Found
response because the endpoint cannot be accessed.curl -H "X-httpbin: true" -H "api-key: test-apikey" -v http://httpbin:8000/status
This time, send a request to an allowed endpoint but with an HTTP method that is not allowed by the OPA policy, such as
PUT
. The request is blocked with a405 Method Not Allowed
response.curl -H "X-httpbin: true" -H "api-key: test-apikey" -X PUT -v http://httpbin:8000/status
Cleanup
You can optionally remove the resources that you set up as part of this guide.
- Delete the resources that you created.
kubectl -n gloo-mesh delete ConfigMap opa-config --context $REMOTE_CONTEXT1 kubectl -n httpbin delete ExtAuthServer opa-ext-auth-server --context $REMOTE_CONTEXT1 kubectl -n httpbin delete ExtAuthPolicy opa-sidecar --context $REMOTE_CONTEXT1
- Repeat the Helm upgrade steps, disabling the OPA server sidecar in the external auth service in the Helm values file.
extAuthService: enabled: true extAuth: opaServer: enabled: false
Update OPA config
To update OPA config after initially deploying the OPA server sidecar, choose from the following options.
- Upgrade your Helm installation with the new OPA config.
- Create a Kubernetes config map with the new OPA config and restart the OPA server, as show in the following steps.
Steps for creating and updating config maps:
Follow Steps 1 - 3 of Bundle Rego rules to create, bundle, and store your Rego rules in a cloud provider.
Create a Kubernetes config map that refers to your bundle.
Review the following table to understand this configuration.kubectl apply --context $REMOTE_CONTEXT1 -f - <<EOF apiVersion: v1 kind: ConfigMap metadata: name: opa-config namespace: gloo-mesh data: config.yaml: | services: gcs: url: https://storage.googleapis.com/storage/v1/b/${BUCKET_NAME}/o bundles: bundle: service: gcs resource: 'bundle.tar.gz?alt=media' EOF
Setting Description namespace
Create the config map in the same namespace as the external auth server, such as gloo-mesh
.config.yaml
Enter the bundle configuration details that you created as part of uploading your bundle to the cloud provider. For more information, see the OPA implementation docs. services
Provide the details of the cloud service where the bundle is located. In this example, the bundle is in a Google Cloud Storage ( gcs
) bucket. Make sure to update the${BUCKET_NAME}
with the name of thegcs
bucket. For quick testing, you can use a bucket with a public URL. Or, you can also set up secure access with thecredentials
settings.bundles
Provide the details about the particular bundle that you want to use. In this example, the bundle is the bundle.tar.gz
bundle that you previously created.Other settings If you use other features, you can configure those settings in the config map. Common settings include signed bundles and returning decision logs. For more information, see the OPA implementation docs. For your OPA config changes to take effect, restart the external auth service with the OPA server sidecar. You must restart the OPA server each time that you update the OPA config. Optionally, you can create the config map before enabling the OPA server sidecar and refer to the config map during the Helm installation. This way, the first time the OPA server sidecar comes up, it has the OPA config already, reducing the number of times you might have to restart the service.
kubectl rollout restart deployment/ext-auth-service -n gloo-mesh --context $REMOTE_CONTEXT1
Optional: Check that the OPA server is healthy and accepted the config. Note the following example command pipes the output to
jq
for readability.- Confirm that the OPA server loaded the bundle that you referred to in the config map.
- Confirm the health checks return a
200
response status.
kubectl logs -n gloo-mesh deploy/ext-auth-service -c opa-auth --context $REMOTE_CONTEXT1 | jq
{ "level": "info", "msg": "Bundle loaded and activated successfully. Etag updated to CMzq8eO/p4EDEAE=.", "name": "httpbin", "plugin": "bundle", "time": "2023-09-20T15:54:47Z" } { "client_addr": "@", "level": "info", "msg": "Received request.", "req_id": 2, "req_method": "GET", "req_path": "/health", "time": "2023-09-20T15:54:48Z" } { "client_addr": "@", "level": "info", "msg": "Sent response.", "req_id": 2, "req_method": "GET", "req_path": "/health", "resp_bytes": 3, "resp_duration": 0.499848, "resp_status": 200, "time": "2023-09-20T15:54:48Z" }