Support dynamic headers with $ in custom-header ConfigMap #13831
Description
What happened:
When trying to set a custom header dynamically from an upstream header in ingress-nginx using the annotation nginx.ingress.kubernetes.io/custom-headers ConfigMap, we run into issues with $ characters.
For example:
Having the following configmap:
apiVersion: v1
data:
X-Accel-Buffering: "$upstream_http_x_accel_buffering"
kind: ConfigMap
metadata:
name: x-accel-buffering-test
And the corresponding ingress:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
annotations:
nginx.ingress.kubernetes.io/custom-headers: namespace/x-accel-buffering-test
...
name: accel-buffering
Then the generated nginx.conf will generate something like this:
more_set_headers "X-Accel-Buffering: ${literal_dollar}upstream_http_x_accel_buffering";
What you expected to happen:
nginx.conf shouldn't have the ${literal_dollar} part:
more_set_headers "X-Accel-Buffering: $upstream_http_x_accel_buffering";
nginx.tmpl is replacing $ with ${literal_dollar} here. I don't know if this is intended.
NGINX Ingress controller version: v1.12.5
Kubernetes version: v1.33.2
Environment:
- Cloud provider or hardware configuration: AWS EKS
- OS (e.g. from /etc/os-release): Amazon Linux 2023
- Kernel (e.g.
uname -a): 6.12
How to reproduce this issue:
As minimally and precisely as possible. Keep in mind we do not have access to your cluster or application.
Help up us (if possible) reproducing the issue using minikube or kind.
Install minikube/kind
- Minikube https://minikube.sigs.k8s.io/docs/start/
- Kind https://kind.sigs.k8s.io/docs/user/quick-start/
Install the ingress controller
kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/main/deploy/static/provider/baremetal/deploy.yaml
Install an application that will act as default backend (is just an echo app)
kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/main/docs/examples/http-svc.yaml
Create an ingress (please add any additional annotation required)
echo "
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: foo-bar
annotations:
kubernetes.io/ingress.class: nginx
nginx.ingress.kubernetes.io/custom-headers: namespace/x-accel-buffering-test
spec:
ingressClassName: nginx # omit this if you're on controller version below 1.0.0
rules:
- host: foo.bar
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: http-svc
port:
number: 80
" | kubectl apply -f -
Create the custom header configmap
apiVersion: v1
data:
X-Accel-Buffering: "$upstream_http_x_accel_buffering"
kind: ConfigMap
metadata:
name: x-accel-buffering-test
Make a request and check the Headers
POD_NAME=$(k get pods -n ingress-nginx -l app.kubernetes.io/name=ingress-nginx -o NAME)
kubectl exec -it -n ingress-nginx $POD_NAME -- curl -vH 'Host: foo.bar' localhost