Host header copied from X-Forwarded-Host (when forwarded headers are enabled)

[paovitali]

Is this a request for help? (If yes, you should use our troubleshooting guide and community support channels, see https://kubernetes.io/docs/tasks/debug-application-cluster/troubleshooting/.): No

What keywords did you search in NGINX Ingress controller issues before filing this one? (If you have found any duplicates, you should instead reply there.): nginx, ingress, forwarded, x-forwarded-host

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Is this a BUG REPORT or FEATURE REQUEST? (choose one): BUG REPORT

NGINX Ingress controller version: 0.22

Kubernetes version (use kubectl version): 1.10.5

Environment: Bare Metal

• Cloud provider or hardware configuration: Bare Metal
• OS (e.g. from /etc/os-release): Ubuntu 16.04.3 LTS
• Kernel (e.g. uname -a): 4.4.0-109-generic
• Install tools: Puppet

What happened:
With reference to these past issue (went stale/closed with no action):

#3131
#2463

I am still seeing, when applying to a nginx controller deploy the configmap key use-forwarded-headers: "true" , that the Host header gets populated with values from X-Forwarded-Host. This leads to issues when applications/components that are receiving traffic from controller are not able to evaluate an array of values in the Host header e.g.:Host=<host..1>,<host..2>,<host..n>.

What you expected to happen: the Host header must never be rewritten or contain duplicated values from other headers, expecially the X-Forwarded-Host.

How to reproduce it (as minimally and precisely as possible): Fire up a 0.22 nginx ingress controller with cfm use-forwarded-headers: "true" and check the value of Host header on an upstream pod receiving traffic.

Anything else we need to know: The template snippet involved in the above described actions:

nginx map activated when use-forwarded-headers: "true"

map $http_x_forwarded_host $best_http_host {
        default          $http_x_forwarded_host;
        ''               $this_host;
    }