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TLS/HTTPS

TLS Secrets

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

!!! warning Ensure that the certificate order is leaf->intermediate->root, otherwise the controller will not be able to import the certificate, and you'll see this error in the logs W1012 09:15:45.920000 6 backend_ssl.go:46] Error obtaining X.509 certificate: unexpected error creating SSL Cert: certificate and private key does not have a matching public key: tls: private key does not match public key

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=${HOST}" -addext "subjectAltName = DNS:${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.

Host names

Ensure that the relevant ingress rules specify a matching hostname.

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 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.

If the tls: section is not set, NGINX will provide the default certificate but will not force HTTPS redirect.

On the other hand, if the tls: section is set - even without specifying a secretName option - NGINX will force HTTPS redirect.

To force redirects for Ingresses that do not specify a TLS-block at all, take a look at force-ssl-redirect in ConfigMap.

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 cert-manager

cert-manager automatically requests missing or expired certificates from a range of supported issuers (including Let's Encrypt) by monitoring ingress resources.

To set up cert-manager you should take a look at this full example.

To enable it for an ingress resource you have to deploy cert-manager, configure a certificate issuer update the manifest:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ingress-demo
  annotations:
    cert-manager.io/issuer: "letsencrypt-staging" # Replace this with a production issuer once you've tested it
    [..]
spec:
  tls:
    - hosts:
        - ingress-demo.example.com
      secretName: ingress-demo-tls
    [...]

Default TLS Version and Ciphers

To provide the most secure baseline configuration possible,

ingress-nginx defaults to using TLS 1.2 and 1.3 only, with 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 ingress-nginx'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 (generated using the Mozilla SSL Configuration Generator)mozilla-ssl-config-old:

kind: ConfigMap
apiVersion: v1
metadata:
  name: nginx-config
data:
  ssl-ciphers: "ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA"
  ssl-protocols: "TLSv1.2 TLSv1.3"