Securing Gateways with HTTPS Using Secret Discovery Service

10 minute read

The Control Ingress Traffic task describes how to configure an ingress gateway to expose an HTTP endpoint of a service to external traffic. This task shows how to do it but using HTTPS access to the service with either simple or mutual TLS. The private key, server certificate, and root certificate required in mutual TLS are configured using Secret Discovery Service (SDS).

Before you begin

Perform the steps in the Before you begin and Determining the ingress IP and ports sections of the Control Ingress Traffic task. After performing those steps you should have Istio and the httpbin service deployed, and the environment variables INGRESS_HOST and SECURE_INGRESS_PORT set.
For macOS users, verify that you use curl compiled with the LibreSSL library:
```
$ curl --version | grep LibreSSL
curl 7.54.0 (x86_64-apple-darwin17.0) libcurl/7.54.0 LibreSSL/2.0.20 zlib/1.2.11 nghttp2/1.24.0
```
If the previous command outputs a version of LibreSSL as shown, your curl command should work correctly with the instructions in this task. Otherwise, try a different implementation of curl, for example on a Linux machine.

Generate client and server certificates and keys

For this task you can use your favorite tool to generate certificates and keys. This example uses a script from the https://github.com/nicholasjackson/mtls-go-example repository.

Clone the example’s repository:

$ git clone https://github.com/nicholasjackson/mtls-go-example

Go to the cloned repository:
```
$ pushd mtls-go-example
```
Generate the certificates for httpbin.example.com. Replace password with any value in the following command:
```
$ ./generate.sh httpbin.example.com password
```
When prompted, answer y to all the questions. The command generates four directories: 1_root, 2_intermediate, 3_application, and 4_client containing the client and server certificates to use in the procedures below.

Move the certificates into a directory named httpbin.example.com:

$ mkdir ~+1/httpbin.example.com && mv 1_root 2_intermediate 3_application 4_client ~+1/httpbin.example.com

Go back to your previous directory:
```
$ popd
```

Configure a TLS ingress gateway using SDS

You can configure a TLS ingress gateway to fetch credentials from the ingress gateway agent via secret discovery service (SDS). The ingress gateway agent runs in the same pod as the ingress gateway and watches the credentials created in the same namespace as the ingress gateway. Enabling SDS at ingress gateway brings the following benefits.

The ingress gateway can dynamically add, delete, or update its key/certificate pairs and its root certificate. You do not have to restart the ingress gateway.
No secret volume mount is needed. Once you create a kubernetes secret, that secret is captured by the gateway agent and sent to ingress gateway as key/certificate or root certificate.
The gateway agent can watch multiple key/certificate pairs. You only need to create secrets for multiple hosts and update the gateway definitions.

Enable SDS at ingress gateway and deploy the ingress gateway agent. Since this feature is disabled by default, you need to enable the istio-ingressgateway.sds.enabled flag in helm, and then generate the istio-ingressgateway.yaml file:

$ helm template install/kubernetes/helm/istio/ --name istio \
--namespace istio-system -x charts/gateways/templates/deployment.yaml \
--set gateways.istio-egressgateway.enabled=false \
--set gateways.istio-ingressgateway.sds.enabled=true > \
$HOME/istio-ingressgateway.yaml
$ kubectl apply -f $HOME/istio-ingressgateway.yaml

Set the environment variables INGRESS_HOST and SECURE_INGRESS_PORT:

$ export SECURE_INGRESS_PORT=$(kubectl -n istio-system \
get service istio-ingressgateway -o jsonpath='{.spec.ports[?(@.name=="https")].port}')
$ export INGRESS_HOST=$(kubectl -n istio-system \
get service istio-ingressgateway -o jsonpath='{.status.loadBalancer.ingress[0].ip}')

Configure a TLS ingress gateway for a single host

Start the httpbin sample:

$ cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Service
metadata:
  name: httpbin
  labels:
    app: httpbin
spec:
  ports:
  - name: http
    port: 8000
  selector:
    app: httpbin
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: httpbin
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: httpbin
        version: v1
    spec:
      containers:
      - image: docker.io/citizenstig/httpbin
        imagePullPolicy: IfNotPresent
        name: httpbin
        ports:
        - containerPort: 8000
EOF

Create a secret for the ingress gateway:

$ kubectl create -n istio-system secret generic httpbin-credential \
--from-file=key=httpbin.example.com/3_application/private/httpbin.example.com.key.pem \
--from-file=cert=httpbin.example.com/3_application/certs/httpbin.example.com.cert.pem

Define a gateway with a servers: section for port 443, and specify values for credentialName to be httpbin-credential. The values are the same as the secret’s name. The TLS mode should have the value of SIMPLE.

$ cat <<EOF | kubectl apply -f -
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: mygateway
spec:
  selector:
    istio: ingressgateway # use istio default ingress gateway
  servers:
  - port:
      number: 443
      name: https
      protocol: HTTPS
    tls:
      mode: SIMPLE
      credentialName: "httpbin-credential" # must be the same as secret
    hosts:
    - "httpbin.example.com"
EOF

Configure the gateway’s ingress traffic routes. Define the corresponding virtual service.

$ cat <<EOF | kubectl apply -f -
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: httpbin
spec:
  hosts:
  - "httpbin.example.com"
  gateways:
  - mygateway
  http:
  - match:
    - uri:
        prefix: /status
    - uri:
        prefix: /delay
    route:
    - destination:
        port:
          number: 8000
        host: httpbin
EOF

Send an HTTPS request to access the httpbin service through HTTPS:

$ curl -v -HHost:httpbin.example.com \
--resolve httpbin.example.com:$SECURE_INGRESS_PORT:$INGRESS_HOST \
--cacert httpbin.example.com/2_intermediate/certs/ca-chain.cert.pem \
https://httpbin.example.com:$SECURE_INGRESS_PORT/status/418

The httpbin service will return the 418 I’m a Teapot code.

Delete the gateway’s secret and create a new one to change the ingress gateway’s credentials.

$ kubectl -n istio-system delete secret httpbin-credential

$ pushd mtls-go-example
$ ./generate.sh httpbin.example.com <password>
$ mkdir ~+1/httpbin.new.example.com && mv 1_root 2_intermediate \
3_application 4_client ~+1/httpbin.new.example.com
$ popd
$ kubectl create -n istio-system secret generic httpbin-credential \
--from-file=key=httpbin.new.example.com/3_application/private/httpbin.example.com.key.pem \
--from-file=cert=httpbin.new.example.com/3_application/certs/httpbin.example.com.cert.pem

Access the httpbin service using curl

$ curl -v -HHost:httpbin.example.com \
--resolve httpbin.example.com:$SECURE_INGRESS_PORT:$INGRESS_HOST \
--cacert httpbin.new.example.com/2_intermediate/certs/ca-chain.cert.pem \
https://httpbin.example.com:$SECURE_INGRESS_PORT/status/418
...
HTTP/2 418
...
-=[ teapot ]=-

   _...._
 .'  _ _ `.
| ."` ^ `". _,
\_;`"---"`|//
  |       ;/
  \_     _/
    `"""`

If you try to access httpbin with the previous certificate chain, the attempt now fails.

$ curl -v -HHost:httpbin.example.com \
--resolve httpbin.example.com:$SECURE_INGRESS_PORT:$INGRESS_HOST \
--cacert httpbin.example.com/2_intermediate/certs/ca-chain.cert.pem \
https://httpbin.example.com:$SECURE_INGRESS_PORT/status/418
...
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (OUT), TLS alert, Server hello (2):
* SSL certificate problem: unable to get local issuer certificate

Configure a TLS ingress gateway for multiple hosts

You can configure an ingress gateway for multiple hosts, httpbin.example.com and helloworld-v1.example.com, for example. The ingress gateway retrieves unique credentials corresponding to a specific credentialName.

Start the helloworld-v1 sample

$ cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Service
metadata:
  name: helloworld-v1
  labels:
    app: helloworld-v1
spec:
  ports:
  - name: http
    port: 8000
  selector:
    app: helloworld-v1
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: helloworld-v1
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: helloworld-v1
    spec:
      containers:
      - name: helloworld
        image: istio/examples-helloworld-v1
        resources:
          requests:
            cpu: "100m"
        imagePullPolicy: IfNotPresent #Always
        ports:
        - containerPort: 5000
EOF

Create a secret for the ingress gateway. If you created the httpbin-credential secret already, you can now create the helloworld-credential secret.

$ pushd mtls-go-example
$ ./generate.sh helloworld-v1.example.com <password>
$ mkdir ~+1/helloworld-v1.example.com && mv 1_root 2_intermediate \
3_application 4_client ~+1/helloworld-v1.example.com
$ popd
$ kubectl create -n istio-system secret generic helloworld-credential \
--from-file=key=helloworld-v1.example.com/3_application/private/helloworld-v1.example.com.key.pem \
--from-file=cert=helloworld-v1.example.com/3_application/certs/helloworld-v1.example.com.cert.pem

Define a gateway with two server sections for port 443. Set the value of credentialName on each port to httpbin-credential and helloworld-credential respectively. Set TLS mode to SIMPLE. serverCertificate and privateKey should not be empty.

$ cat <<EOF | kubectl apply -f -
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: mygateway
spec:
  selector:
    istio: ingressgateway # use istio default ingress gateway
  servers:
  - port:
      number: 443
      name: https-httpbin
      protocol: HTTPS
    tls:
      mode: SIMPLE
      credentialName: "httpbin-credential"
    hosts:
    - "httpbin.example.com"
  - port:
      number: 443
      name: https-helloworld
      protocol: HTTPS
    tls:
      mode: SIMPLE
      credentialName: "helloworld-credential"
    hosts:
    - "helloworld-v1.example.com"
EOF

Configure the gateway’s traffic routes. Define the corresponding virtual service.

$ cat <<EOF | kubectl apply -f -
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: helloworld-v1
spec:
  hosts:
  - "helloworld-v1.example.com"
  gateways:
  - mygateway
  http:
  - match:
    - uri:
        exact: /hello
    route:
    - destination:
        host: helloworld-v1
        port:
          number: 5000
EOF

Send an HTTPS request to helloworld-v1.example.com:

$ curl -v -HHost:helloworld-v1.example.com \
--resolve helloworld-v1.example.com:$SECURE_INGRESS_PORT:$INGRESS_HOST \
--cacert helloworld-v1.example.com/2_intermediate/certs/ca-chain.cert.pem \
https://helloworld-v1.example.com:$SECURE_INGRESS_PORT/hello
HTTP/2 200

Send an HTTPS request to httpbin.example.com and still get a teapot in return:

$ curl -v -HHost:httpbin.example.com \
--resolve httpbin.example.com:$SECURE_INGRESS_PORT:$INGRESS_HOST \
--cacert httpbin.example.com/2_intermediate/certs/ca-chain.cert.pem \
https://httpbin.example.com:$SECURE_INGRESS_PORT/status/418
    -=[ teapot ]=-

       _...._
     .'  _ _ `.
    | ."` ^ `". _,
    \_;`"---"`|//
      |       ;/
      \_     _/
        `"""`

Configure a mutual TLS ingress gateway

You can extend your gateway’s definition to support mutual TLS. Change the credentials of the ingress gateway by deleting its secret and creating a new one. The server uses the CA certificate to verify its clients, and we must use the name cacert to hold the CA certificate.

$ kubectl -n istio-system delete secret httpbin-credential
$ kubectl create -n istio-system secret generic httpbin-credential  \
--from-file=key=httpbin.example.com/3_application/private/httpbin.example.com.key.pem \
--from-file=cert=httpbin.example.com/3_application/certs/httpbin.example.com.cert.pem \
--from-file=cacert=httpbin.example.com/2_intermediate/certs/ca-chain.cert.pem

Change the gateway’s definition to set the TLS mode to MUTUAL.

$ cat <<EOF | kubectl apply -f -
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
 name: mygateway
spec:
 selector:
   istio: ingressgateway # use istio default ingress gateway
 servers:
 - port:
     number: 443
     name: https
     protocol: HTTPS
   tls:
     mode: MUTUAL
     credentialName: "httpbin-credential" # must be the same as secret
   hosts:
   - "httpbin.example.com"
EOF

Attempt to send an HTTPS request using the prior approach and see how it fails:

$ curl -v -HHost:httpbin.example.com \
--resolve httpbin.example.com:$SECURE_INGRESS_PORT:$INGRESS_HOST \
--cacert httpbin.example.com/2_intermediate/certs/ca-chain.cert.pem \
https://httpbin.example.com:$SECURE_INGRESS_PORT/status/418
* TLSv1.2 (OUT), TLS header, Certificate Status (22):
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Request CERT (13):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Certificate (11):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Client hello (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS alert, Server hello (2):
* error:14094410:SSL routines:ssl3_read_bytes:sslv3 alert handshake failure

Pass a client certificate and private key to curl and resend the request. Pass your client’s certificate with the --cert flag and your private key with the --key flag to curl.

$ curl -v -HHost:httpbin.example.com \
--resolve httpbin.example.com:$SECURE_INGRESS_PORT:$INGRESS_HOST \
--cacert httpbin.example.com/2_intermediate/certs/ca-chain.cert.pem \
--cert httpbin.example.com/4_client/certs/httpbin.example.com.cert.pem \
--key httpbin.example.com/4_client/private/httpbin.example.com.key.pem \
https://httpbin.example.com:$SECURE_INGRESS_PORT/status/418

    -=[ teapot ]=-

       _...._
     .'  _ _ `.
    | ."` ^ `". _,
    \_;`"---"`|//
      |       ;/
      \_     _/

Troubleshooting

Inspect the values of the INGRESS_HOST and SECURE_INGRESS_PORT environment variables. Make sure they have valid values, according to the output of the following commands:
```
$ kubectl get svc -n istio-system
$ echo INGRESS_HOST=$INGRESS_HOST, SECURE_INGRESS_PORT=$SECURE_INGRESS_PORT
```

Check the log of the istio-ingressgateway controller for error messages:

$ kubectl logs -n istio-system $(kubectl get pod -l istio=ingressgateway \
-n istio-system -o jsonpath='{.items[0].metadata.name}') -c istio-proxy

If using macOS, verify you are using curl compiled with the LibreSSL library, as described in the Before you begin section.
Verify that the secrets are successfully created in the istio-system namespace:
```
$ kubectl -n istio-system get secrets
```
httpbin-credential and helloworld-credential should show in the secrets list.
Check the logs to verify that the ingress gateway agent has pushed the key/certificate pair to the ingress gateway.
```
$ kubectl logs -n istio-system $(kubectl get pod -l istio=ingressgateway \
-n istio-system -o jsonpath='{.items[0].metadata.name}') -c ingress-sds
```
The log should show that the httpbin-credential secret was added. If using mutual TLS, then the httpbin-credential-cacert secret should also appear. Verify the log shows that the gateway agent receives SDS requests from the ingress gateway, that the resource’s name is httpbin-credential, and that the ingress gateway obtained the key/certificate pair. If using mutual TLS, the log should show key/certificate was sent to the ingress gateway, that the gateway agent received the SDS request with the httpbin-credential-cacert resource name, and that the ingress gateway obtained the root certificate.

Cleanup

Delete the gateway configuration, the virtual service definition, and the secrets:

$ kubectl delete gateway mygateway
$ kubectl delete virtualservice httpbin
$ kubectl delete --ignore-not-found=true -n istio-system secret httpbin-credential \
helloworld-credential
$ kubectl delete --ignore-not-found=true virtualservice helloworld-v1

Delete the directories of the certificates and the repository used to generate them:
```
$ rm -rf httpbin.example.com helloworld-v1.example.com mtls-go-example
```
Remove the file you used for redeployment of the ingress gateway.
```
$ rm -f $HOME/istio-ingressgateway.yaml
```

Shutdown the httpbin and helloworld-v1 services:

$ kubectl delete service --ignore-not-found=true helloworld-v1
$ kubectl delete service --ignore-not-found=true httpbin