fix newlines location denied

[alanbover]

What this PR does / why we need it:
Escape '\n' simbols when logging 'Location denied' error in nginx configuration. Without it, nginx completelly breaks and it's unable to generate new configurations affecting other possible tenants in the cluster.

Which issue this PR fixes
We create an ingress object with an incorrect ip-whitelisting annotation. For example:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: cafe-ingress
  annotations:
    nginx.ingress.kubernetes.io/whitelist-source-range: |
       # This comment breaks ingress
       8.8.8.8/32,
       9.9.9.9/32
spec:
  rules:
  - host: cafe.example.com
    http:
      paths:
      - path: /tea
        backend:
          serviceName: tea-svc
          servicePort: 80
      - path: /coffee
        backend:
          serviceName: coffee-svc
          servicePort: 80

Ingress will start failing with an error:

E0921 09:40:26.453561       8 controller.go:183] Unexpected failure reloading the backend:-------------------------------------------------------------------------------
Error: exit status 1
2018/09/21 09:40:26 [emerg] 660#660: unknown directive "8.8.8.8/32" in /tmp/nginx-cfg534865713:414
nginx: [emerg] unknown directive "8.8.8.8/32" in /tmp/nginx-cfg534865713:414
nginx: configuration file /tmp/nginx-cfg534865713 test failed-------------------------------------------------------------------------------
W0921 09:40:26.453594       8 queue.go:130] requeuing default/cafe-ingress, err 

Because it's generating an incorrect location on nginx:

 location /tea {

                        set $namespace      "default";
                        set $ingress_name   "cafe-ingress";
                        set $service_name   "tea-svc";
                        set $service_port   "80";
                        set $location_path  "/tea";

                        rewrite_by_lua_block {

                                balancer.rewrite()

                        }

                        log_by_lua_block {

                                balancer.log()

                                monitor.call()
                        }

                        port_in_redirect off;

                        set $proxy_upstream_name "default-tea-svc-80";

                        # Location denied. Reason: the annotation does not contain a valid IP address or network: invalid CIDR address: # This should make it fail
                        8.8.8.8/32
                        return 503;

                }

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[alanbover]

Contributor License Agreement (CLA) should be signed now

[antoineco]

@alanbover this sounds like an input issue to me.

1. The annotation does not support comments, the input must be a comma separated list with nothing else.
2. Please use the > syntax instead of |, this effectively ignores new lines in YAML.

With that being said, this PR is only about preventing formatting issues, right? If yes, to my knowledge %q does not suppress newlines.

[alanbover]

@antoineco ,

Yes, I know the input is incorrect. In fact the PR, as you said, is not about making nginx support comments or new lines, but to prevent it from explote.

This is what you get as result with this PR (tested locally on minikube):

		location /coffee {
			
			set $namespace      "default";
			set $ingress_name   "cafe-ingress2";
			set $service_name   "coffee-svc";
			set $service_port   "80";
			set $location_path  "/coffee";
			
			rewrite_by_lua_block {
				
				balancer.rewrite()
				
			}
			
			log_by_lua_block {
				
				balancer.log()
				
				monitor.call()
			}
			
			if ($scheme = https) {
				more_set_headers                        "Strict-Transport-Security: max-age=15724800; includeSubDomains";
			}
			
			port_in_redirect off;
			
			set $proxy_upstream_name "default-coffee-svc-80";
			
			# enforce ssl on server side
			if ($redirect_to_https) {
				
				return 308 https://$best_http_host$request_uri;
				
			}
			
			# Location denied. Reason: "the annotation does not contain a valid IP address or network: invalid CIDR address: # This comment breaks ingress\n8.8.8.8"
			return 503;
			
		}

As you can see, the \n are now escaped. From https://golang.org/pkg/fmt/:

%q	a single-quoted character literal safely escaped with Go syntax.

[antoineco]

@alanbover Alright, thanks for the confirmation. And you're right about %q 👍 New lines are converted to a litteral \n.

/lgtm

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alanbover, antoineco

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[alanbover]

thanks!