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TLS/HTTPS

TLS Secrets

Anytime we reference a TLS secret, we mean a PEM-encoded X.509, RSA (2048) secret.

You can generate a self-signed certificate and private key with:

$ openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout ${KEY_FILE} -out ${CERT_FILE} -subj "/CN=${HOST}/O=${HOST}"`

Then create the secret in the cluster via:

kubectl create secret tls ${CERT_NAME} --key ${KEY_FILE} --cert ${CERT_FILE}

The resulting secret will be of type kubernetes.io/tls.

Default SSL Certificate

NGINX provides the option to configure a server as a catch-all with server_name for requests that do not match any of the configured server names. This configuration works without out-of-the-box for HTTP traffic. For HTTPS, a certificate is naturally required.

For this reason the Ingress controller provides the flag --default-ssl-certificate. The secret referred to by this flag contains the default certificate to be used when accessing the catch-all server. If this flag is not provided NGINX will use a self-signed certificate.

For instance, if you have a TLS secret foo-tls in the default namespace, add --default-ssl-certificate=default/foo-tls in the nginx-controller deployment.

SSL Passthrough

The --enable-ssl-passthrough flag enables the SSL Passthrough feature, which is disabled by default. This is required to enable passthrough backends in Ingress objects.

Warning

This feature is implemented by intercepting all traffic on the configured HTTPS port (default: 443) and handing it over to a local TCP proxy. This bypasses NGINX completely and introduces a non-negligible performance penalty.

SSL Passthrough leverages SNI and reads the virtual domain from the TLS negotiation, which requires compatible clients. After a connection has been accepted by the TLS listener, it is handled by the controller itself and piped back and forth between the backend and the client.

If there is no hostname matching the requested host name, the request is handed over to NGINX on the configured passthrough proxy port (default: 442), which proxies the request to the default backend.

Note

Unlike HTTP backends, traffic to Passthrough backends is sent to the clusterIP of the backing Service instead of individual Endpoints.

HTTP Strict Transport Security

HTTP Strict Transport Security (HSTS) is an opt-in security enhancement specified through the use of a special response header. Once a supported browser receives this header that browser will prevent any communications from being sent over HTTP to the specified domain and will instead send all communications over HTTPS.

HSTS is enabled by default.

To disable this behavior use hsts: "false" in the configuration ConfigMap.

Server-side HTTPS enforcement through redirect

By default the controller redirects HTTP clients to the HTTPS port 443 using a 308 Permanent Redirect response if TLS is enabled for that Ingress.

This can be disabled globally using ssl-redirect: "false" in the NGINX config map, or per-Ingress with the nginx.ingress.kubernetes.io/ssl-redirect: "false" annotation in the particular resource.

Tip

When using SSL offloading outside of cluster (e.g. AWS ELB) it may be useful to enforce a redirect to HTTPS even when there is no TLS certificate available. This can be achieved by using the nginx.ingress.kubernetes.io/force-ssl-redirect: "true" annotation in the particular resource.

Automated Certificate Management with Kube-Lego

Tip

Kube-Lego has reached end-of-life and is being replaced by cert-manager.

Kube-Lego automatically requests missing or expired certificates from Let's Encrypt by monitoring ingress resources and their referenced secrets.

To enable this for an ingress resource you have to add an annotation:

kubectl annotate ing ingress-demo kubernetes.io/tls-acme="true"

To setup Kube-Lego you can take a look at this full example. The first version to fully support Kube-Lego is Nginx Ingress controller 0.8.

Default TLS Version and Ciphers

To provide the most secure baseline configuration possible,

nginx-ingress defaults to using TLS 1.2 only and a secure set of TLS ciphers.

Legacy TLS

The default configuration, though secure, does not support some older browsers and operating systems.

For instance, TLS 1.1+ is only enabled by default from Android 5.0 on. At the time of writing, May 2018, approximately 15% of Android devices are not compatible with nginx-ingress's default configuration.

To change this default behavior, use a ConfigMap.

A sample ConfigMap fragment to allow these older clients to connect could look something like the following:

kind: ConfigMap
apiVersion: v1
metadata:
  name: nginx-config
data:
  ssl-ciphers: "ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:DHE-RSA-AES256-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:AES:CAMELLIA:DES-CBC3-SHA:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:!PSK:!aECDH:!EDH-DSS-DES-CBC3-SHA:!EDH-RSA-DES-CBC3-SHA:!KRB5-DES-CBC3-SHA"
  ssl-protocols: "TLSv1 TLSv1.1 TLSv1.2"