Secure Gateways (SDS)

10 minute read

The Control Ingress Traffic task describes how to configure an ingress gateway to expose an HTTP service to external traffic. This task shows how to expose a secure HTTPS service using either simple or mutual TLS.

The TLS required private key, server certificate, and root certificate, are configured using the 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. The commands below use openssl

Create a root certificate and private key to sign the certificates for your services:

$ openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -subj '/O=example Inc./CN=example.com' -keyout example.com.key -out example.com.crt

Create a certificate and a private key for httpbin.example.com:

$ openssl req -out httpbin.example.com.csr -newkey rsa:2048 -nodes -keyout httpbin.example.com.key -subj "/CN=httpbin.example.com/O=httpbin organization"
$ openssl x509 -req -days 365 -CA example.com.crt -CAkey example.com.key -set_serial 0 -in httpbin.example.com.csr -out httpbin.example.com.crt

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 installation option and generate the istio-ingressgateway.yaml file:

$ istioctl manifest generate \
--set values.gateways.istio-egressgateway.enabled=false \
--set values.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: apps/v1
kind: Deployment
metadata:
  name: httpbin
spec:
  replicas: 1
  selector:
    matchLabels:
      app: httpbin
      version: v1
  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.key \
--from-file=cert=httpbin.example.com.crt

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 example.com.crt 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

$ mkdir new_certificates
$ openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -subj '/O=example Inc./CN=example.com' -keyout new_certificates/example.com.key -out new_certificates/example.com.crt
$ openssl req -out new_certificates/httpbin.example.com.csr -newkey rsa:2048 -nodes -keyout new_certificates/httpbin.example.com.key -subj "/CN=httpbin.example.com/O=httpbin organization"
$ openssl x509 -req -days 365 -CA new_certificates/example.com.crt -CAkey new_certificates/example.com.key -set_serial 0 -in new_certificates/httpbin.example.com.csr -out new_certificates/httpbin.example.com.crt
$ kubectl create -n istio-system secret generic httpbin-credential \
--from-file=key=new_certificates/httpbin.example.com.key \
--from-file=cert=new_certificates/httpbin.example.com.crt

Access the httpbin service using curl using the new certificate chain:

$ curl -v -HHost:httpbin.example.com --resolve httpbin.example.com:$SECURE_INGRESS_PORT:$INGRESS_HOST \
--cacert new_certificates/example.com.crt 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 example.com.crt 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):
* curl: (35) error:04FFF06A:rsa routines:CRYPTO_internal:block type is not 01

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.

To restore the credentials for httpbin, delete its secret and create it again.

$ kubectl -n istio-system delete secret httpbin-credential
$ kubectl create -n istio-system secret generic httpbin-credential \
--from-file=key=httpbin.example.com.key \
--from-file=cert=httpbin.example.com.crt

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: 5000
  selector:
    app: helloworld-v1
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: helloworld-v1
spec:
  replicas: 1
  selector:
    matchLabels:
      app: helloworld-v1
      version: v1
  template:
    metadata:
      labels:
        app: helloworld-v1
        version: v1
    spec:
      containers:
      - name: helloworld
        image: istio/examples-helloworld-v1
        resources:
          requests:
            cpu: "100m"
        imagePullPolicy: IfNotPresent #Always
        ports:
        - containerPort: 5000
EOF

Generate a certificate and a private key for helloworld-v1.example.com:

$ openssl req -out helloworld-v1.example.com.csr -newkey rsa:2048 -nodes -keyout helloworld-v1.example.com.key -subj "/CN=helloworld-v1.example.com/O=helloworld organization"
$ openssl x509 -req -days 365 -CA example.com.crt -CAkey example.com.key -set_serial 1 -in helloworld-v1.example.com.csr -out helloworld-v1.example.com.crt

Create the helloworld-credential secret:

$ kubectl create -n istio-system secret generic helloworld-credential --from-file=key=helloworld-v1.example.com.key \
--from-file=cert=helloworld-v1.example.com.crt

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.

$ 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 example.com.crt 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 example.com.crt 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.key \
--from-file=cert=httpbin.example.com.crt --from-file=cacert=example.com.crt

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 example.com.crt https://httpbin.example.com:$SECURE_INGRESS_PORT/status/418
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
* TLSv1.3 (IN), TLS handshake, Server hello (2):
* TLSv1.3 (IN), TLS handshake, Encrypted Extensions (8):
* TLSv1.3 (IN), TLS handshake, Request CERT (13):
* TLSv1.3 (IN), TLS handshake, Certificate (11):
* TLSv1.3 (IN), TLS handshake, CERT verify (15):
* TLSv1.3 (IN), TLS handshake, Finished (20):
* TLSv1.3 (OUT), TLS change cipher, Change cipher spec (1):
* TLSv1.3 (OUT), TLS handshake, Certificate (11):
* TLSv1.3 (OUT), TLS handshake, Finished (20):
* TLSv1.3 (IN), TLS alert, unknown (628):
* OpenSSL SSL_read: error:1409445C:SSL routines:ssl3_read_bytes:tlsv13 alert certificate required, errno 0

Generate client certificate and private key:

$ openssl req -out client.example.com.csr -newkey rsa:2048 -nodes -keyout client.example.com.key -subj "/CN=client.example.com/O=client organization"
$ openssl x509 -req -days 365 -CA example.com.crt -CAkey example.com.key -set_serial 1 -in client.example.com.csr -out client.example.com.crt

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 example.com.crt --cert client.example.com.crt --key client.example.com.key \
https://httpbin.example.com:$SECURE_INGRESS_PORT/status/418

    -=[ teapot ]=-

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

Instead of creating a httpbin-credential secret to hold all the credentials, you can create two separate secrets:

httpbin-credential holds the server’s key and certificate
httpbin-credential-cacert holds the client’s CA certificate and must have the -cacert suffix

Create the two separate secrets with the following commands:

$ kubectl -n istio-system delete secret httpbin-credential
$ kubectl create -n istio-system secret generic httpbin-credential  \
--from-file=key=httpbin.example.com.key --from-file=cert=httpbin.example.com.crt
$ kubectl create -n istio-system secret generic httpbin-credential-cacert  \
--from-file=cacert=example.com.crt

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 certificates and keys:

$ rm -rf example.com.crt example.com.key httpbin.example.com.crt httpbin.example.com.key httpbin.example.com.csr helloworld-v1.example.com.crt helloworld-v1.example.com.key helloworld-v1.example.com.csr client.example.com.crt client.example.com.csr client.example.com.key ./new_certificates

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