1.9. Customizing security in a Service Mesh

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If your service mesh application is constructed with a complex array of microservices, you can use Red Hat OpenShift Service Mesh to customize the security of the communication between those services. The infrastructure of OpenShift Container Platform along with the traffic management features of Service Mesh can help you manage the complexity of your applications and provide service and identity security for microservices.

1.9.1. Enabling mutual Transport Layer Security (mTLS)

Mutual Transport Layer Security (mTLS) is a protocol where two parties authenticate each other at the same time. It is the default mode of authentication in some protocols (IKE, SSH) and optional in others (TLS).

MTLS can be used without changes to the application or service code. The TLS is handled entirely by the service mesh infrastructure and between the two sidecar proxies.

By default, Red Hat OpenShift Service Mesh is set to permissive mode, where the sidecars in Service Mesh accept both plain-text traffic and connections that are encrypted using mTLS. If a service in your mesh is communicating with a service outside the mesh, strict mTLS could break communication between those services. Use permissive mode while you migrate your workloads to Service Mesh.

1.9.1.1. Enabling strict mTLS across the mesh

If your workloads do not communicate with services outside your mesh and communication will not be interrupted by only accepting encrypted connections, you can enable mTLS across your mesh quickly. Set spec.istio.global.mtls.enabled to true in your ServiceMeshControlPlane resource. The operator creates the required resources.

apiVersion: maistra.io/v1
kind: ServiceMeshControlPlane
spec:
  istio:
    global:
      mtls:
        enabled: true

1.9.1.1.1. Configuring sidecars for incoming connections for specific services

You can also configure mTLS for individual services or namespaces by creating a policy.

apiVersion: "authentication.istio.io/v1alpha1"
kind: "Policy"
metadata:
  name: "default"
  namespace: <NAMESPACE>
spec:
  peers:
  - mtls: {}

1.9.1.2. Configuring sidecars for outgoing connections

Create a destination rule to configure Service Mesh to use mTLS when sending requests to other services in the mesh.

apiVersion: "networking.istio.io/v1alpha3"
kind: "DestinationRule"
metadata:
  name: "default"
  namespace: <CONTROL_PLANE_NAMESPACE>
spec:
  host: "*.local"
  trafficPolicy:
    tls:
      mode: ISTIO_MUTUAL

1.9.1.3. Setting the minimum and maximum protocol versions

If your environment has specific requirements for encrypted traffic in your service mesh, you can control the cryptographic functions that are allowed by setting the spec.istio.global.tls.minProtocolVersion or spec.istio.global.tls.maxProtocolVersion in your ServiceMeshControlPlane resource. Those values, configured in your control plane resource, define the minimum and maximum TLS version used by mesh components when communicating securely over TLS.

apiVersion: maistra.io/v1
kind: ServiceMeshControlPlane
spec:
  istio:
    global:
      tls:
        minProtocolVersion: TLSv1_0

The default is TLS_AUTO and does not specify a version of TLS.

表 1.14. Valid values
Value	Description
`TLS_AUTO`	default
`TLSv1_0`	TLS version 1.0
`TLSv1_1`	TLS version 1.1
`TLSv1_2`	TLS version 1.2
`TLSv1_3`	TLS version 1.3

1.9.2. Configuring cipher suites and ECDH curves

Cipher suites and Elliptic-curve Diffie–Hellman (ECDH curves) can help you secure your service mesh. You can define a comma separated list of cipher suites using spec.istio.global.tls.cipherSuites and ECDH curves using spec.istio.global.tls.ecdhCurves in your ServiceMeshControlPlane resource. If either of these attributes are empty, then the default values are used.

The cipherSuites setting is effective if your service mesh uses TLS 1.2 or earlier. It has no effect when negotiating with TLS 1.3.

Set your cipher suites in the comma separated list in order of priority. For example, ecdhCurves: CurveP256, CurveP384 sets CurveP256 as a higher priority than CurveP384.

注意

You must include either TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 or TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 when you configure the cipher suite. HTTP/2 support requires at least one of these cipher suites.

The supported cipher suites are:

TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
TLS_RSA_WITH_AES_128_GCM_SHA256
TLS_RSA_WITH_AES_256_GCM_SHA384
TLS_RSA_WITH_AES_128_CBC_SHA256
TLS_RSA_WITH_AES_128_CBC_SHA
TLS_RSA_WITH_AES_256_CBC_SHA
TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
TLS_RSA_WITH_3DES_EDE_CBC_SHA

The supported ECDH Curves are:

CurveP256
CurveP384
CurveP521
X25519

1.9.3. Adding an external certificate authority key and certificate

By default, Red Hat OpenShift Service Mesh generates self-signed root certificate and key, and uses them to sign the workload certificates. You can also use the user-defined certificate and key to sign workload certificates, with user-defined root certificate. This task demonstrates an example to plug certificates and key into Service Mesh.

Prerequisites

You must have installed Red Hat OpenShift Service Mesh with mutual TLS enabled to configure certificates.
This example uses the certificates from the Maistra repository. For production, use your own certificates from your certificate authority.
You must deploy the Bookinfo sample application to verify the results with these instructions.

1.9.3.1. Adding an existing certificate and key

To use an existing signing (CA) certificate and key, you must create a chain of trust file that includes the CA certificate, key, and root certificate. You must use the following exact file names for each of the corresponding certificates. The CA certificate is called ca-cert.pem, the key is ca-key.pem, and the root certificate, which signs ca-cert.pem, is called root-cert.pem. If your workload uses intermediate certificates, you must specify them in a cert-chain.pem file.

Add the certificates to Service Mesh by following these steps. Save the example certificates from the Maistra repository locally and replace <path> with the path to your certificates.

Create a secret cacert that includes the input files ca-cert.pem, ca-key.pem, root-cert.pem and cert-chain.pem.

$ oc create secret generic cacerts -n istio-system --from-file=<path>/ca-cert.pem \
    --from-file=<path>/ca-key.pem --from-file=<path>/root-cert.pem \
    --from-file=<path>/cert-chain.pem

In the ServiceMeshControlPlane resource set global.mtls.enabled to true and security.selfSigned set to false. Service Mesh reads the certificates and key from the secret-mount files.
```
apiVersion: maistra.io/v1
kind: ServiceMeshControlPlane
spec:
  istio:
    global:
      mtls:
        enabled: true
    security:
      selfSigned: false
```
To make sure the workloads add the new certificates promptly, delete the secrets generated by Service Mesh, named istio.*. In this example, istio.default. Service Mesh issues new certificates for the workloads.
```
$ oc delete secret istio.default
```

1.9.3.2. Verifying your certificates

Use the Bookinfo sample application to verify your certificates are mounted correctly. First, retrieve the mounted certificates. Then, verify the certificates mounted on the pod.

Store the pod name in the variable RATINGSPOD.

$ RATINGSPOD=`oc get pods -l app=ratings -o jsonpath='{.items[0].metadata.name}'`

Run the following commands to retrieve the certificates mounted on the proxy.
```
$ oc exec -it $RATINGSPOD -c istio-proxy -- /bin/cat /etc/certs/root-cert.pem > /tmp/pod-root-cert.pem
```
The file /tmp/pod-root-cert.pem contains the root certificate propagated to the pod.
```
$ oc exec -it $RATINGSPOD -c istio-proxy -- /bin/cat /etc/certs/cert-chain.pem > /tmp/pod-cert-chain.pem
```
The file /tmp/pod-cert-chain.pem contains the workload certificate and the CA certificate propagated to the pod.

Verify the root certificate is the same as the one specified by the Operator. Replace <path> with the path to your certificates.

$ openssl x509 -in <path>/root-cert.pem -text -noout > /tmp/root-cert.crt.txt

$ openssl x509 -in /tmp/pod-root-cert.pem -text -noout > /tmp/pod-root-cert.crt.txt

$ diff /tmp/root-cert.crt.txt /tmp/pod-root-cert.crt.txt

Expect the output to be empty.

Verify the CA certificate is the same as the one specified by Operator. Replace <path> with the path to your certificates.

$ sed '0,/^-----END CERTIFICATE-----/d' /tmp/pod-cert-chain.pem > /tmp/pod-cert-chain-ca.pem

$ openssl x509 -in <path>/ca-cert.pem -text -noout > /tmp/ca-cert.crt.txt

$ openssl x509 -in /tmp/pod-cert-chain-ca.pem -text -noout > /tmp/pod-cert-chain-ca.crt.txt

$ diff /tmp/ca-cert.crt.txt /tmp/pod-cert-chain-ca.crt.txt

Expect the output to be empty.

Verify the certificate chain from the root certificate to the workload certificate. Replace <path> with the path to your certificates.

$ head -n 21 /tmp/pod-cert-chain.pem > /tmp/pod-cert-chain-workload.pem

$ openssl verify -CAfile <(cat <path>/ca-cert.pem <path>/root-cert.pem) /tmp/pod-cert-chain-workload.pem

Example output

/tmp/pod-cert-chain-workload.pem: OK

1.9.3.3. Removing the certificates

To remove the certificates you added, follow these steps.

Remove the secret cacerts.

$ oc delete secret cacerts -n istio-system

Redeploy Service Mesh with a self-signed root certificate in the ServiceMeshControlPlane resource.

apiVersion: maistra.io/v1
kind: ServiceMeshControlPlane
spec:
  istio:
    global:
      mtls:
        enabled: true
    security:
      selfSigned: true