HTTP Redirects

The HTTPRoute resource can issue redirects to clients or rewrite paths sent upstream using filters. Note that HTTPRoute rules cannot use both filter types at once. Currently, Envoy Gateway only supports core HTTPRoute filters which consist of RequestRedirect and RequestHeaderModifier at the time of this writing. To learn more about HTTP routing, refer to the Gateway API documentation.

Prerequisites

Follow the steps from the Quickstart to install Envoy Gateway and the example manifest. Before proceeding, you should be able to query the example backend using HTTPS.

Redirects

Redirects return HTTP 3XX responses to a client, instructing it to retrieve a different resource. A RequestRedirect filter instructs Gateways to emit a redirect response to requests that match the rule. For example, to issue a permanent redirect (301) from HTTP to HTTPS, configure requestRedirect.statusCode=301 and requestRedirect.scheme="https":

cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: http-to-https-filter-redirect
spec:
  parentRefs:
    - name: eg
  hostnames:
    - redirect.example
  rules:
    - filters:
      - type: RequestRedirect
        requestRedirect:
          scheme: https
          statusCode: 301
          hostname: www.example.com
          port: 443
      backendRefs:
      - name: backend
        port: 3000
EOF

Note: 301 (default) and 302 are the only supported statusCodes.

The HTTPRoute status should indicate that it has been accepted and is bound to the example Gateway.

kubectl get httproute/http-to-https-filter-redirect -o yaml

Get the Gateway’s address:

export GATEWAY_HOST=$(kubectl get gateway/eg -o jsonpath='{.status.addresses[0].value}')

Querying redirect.example/get should result in a 301 response from the example Gateway and redirecting to the configured redirect hostname.

$ curl -L -vvv --header "Host: redirect.example" "http://${GATEWAY_HOST}/get"
...
< HTTP/1.1 301 Moved Permanently
< location: https://www.example.com/get
...

If you followed the steps in the Secure Gateways guide, you should be able to curl the redirect location.

HTTP –> HTTPS

Listeners expose the TLS setting on a per domain or subdomain basis. TLS settings of a listener are applied to all domains that satisfy the hostname criteria.

Create a root certificate and private key to sign certificates:

openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -subj '/CN=example.com' -keyout CA.key -out CA.crt
openssl req -out example.com.csr -newkey rsa:2048 -nodes -keyout tls.key -subj "/CN=example.com"

Generate a self-signed wildcard certificate for example.com with *.example.com extension

cat <<EOF | openssl x509 -req -days 365 -CA CA.crt -CAkey CA.key -set_serial 0 \
-subj "/CN=example.com" \
-in example.com.csr -out tls.crt -extensions v3_req  -extfile -
[v3_req]
keyUsage = keyEncipherment, dataEncipherment
extendedKeyUsage = serverAuth
subjectAltName = @alt_names
[alt_names]
DNS.1   = example.com
DNS.2   = *.example.com
EOF

Create the kubernetes tls secret

kubectl create secret tls example-com --key=tls.key --cert=tls.crt

Define a https listener on the existing gateway

cat <<EOF | kubectl apply -n default -f -
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: eg
spec:
  gatewayClassName: eg
  listeners:
  - name: http
    port: 80
    protocol: HTTP
    # hostname: "*.example.com"
  - name: https
    port: 443
    protocol: HTTPS
    # hostname: "*.example.com"
    tls:
      mode: Terminate
      certificateRefs:
      - kind: Secret
        name: example-com
EOF

Check for any TLS certificate issues on the gateway.

kubectl -n default describe gateway eg

Create two HTTPRoutes and attach them to the HTTP and HTTPS listeners using the sectionName field.

cat <<EOF | kubectl apply -n default -f -
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: tls-redirect
spec:
  parentRefs:
    - name: eg
      sectionName: http
  hostnames:
    # - "*.example.com" # catch all hostnames
    - "www.example.com"
  rules:
    - filters:
        - type: RequestRedirect
          requestRedirect:
            scheme: https
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: backend
spec:
  parentRefs:
    - name: eg
      sectionName: https
  hostnames:
    - "www.example.com"
  rules:
    - backendRefs:
        - group: ""
          kind: Service
          name: backend
          port: 3000
          weight: 1
      matches:
        - path:
            type: PathPrefix
            value: /
EOF

Curl the example app through http listener:

curl --verbose --header "Host: www.example.com" http://$GATEWAY_HOST/get

Curl the example app through https listener:

curl -v -H 'Host:www.example.com' --resolve "www.example.com:443:$GATEWAY_HOST" \
--cacert CA.crt https://www.example.com:443/get

Path Redirects

Path redirects use an HTTP Path Modifier to replace either entire paths or path prefixes. For example, the HTTPRoute below will issue a 302 redirect to all path.redirect.example requests whose path begins with /get to /status/200.

cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: http-filter-path-redirect
spec:
  parentRefs:
    - name: eg
  hostnames:
    - path.redirect.example
  rules:
    - matches:
      - path:
          type: PathPrefix
          value: /get
      filters:
      - type: RequestRedirect
        requestRedirect:
          path:
            type: ReplaceFullPath
            replaceFullPath: /status/200
          statusCode: 302
      backendRefs:
      - name: backend
        port: 3000
EOF

The HTTPRoute status should indicate that it has been accepted and is bound to the example Gateway.

kubectl get httproute/http-filter-path-redirect -o yaml

Querying path.redirect.example should result in a 302 response from the example Gateway and a redirect location containing the configured redirect path.

Query the path.redirect.example host:

curl -vvv --header "Host: path.redirect.example" "http://${GATEWAY_HOST}/get"

You should receive a 302 with a redirect location of http://path.redirect.example/status/200.


Last modified May 25, 2024: fix api wording (#3467) (5bc5e0f)