Add annotation to add CORS support

ingress/controllers/nginx/controller.go

@@ -43,6 +43,7 @@ import (
 	"k8s.io/contrib/ingress/controllers/nginx/nginx"
 	"k8s.io/contrib/ingress/controllers/nginx/nginx/auth"
 	"k8s.io/contrib/ingress/controllers/nginx/nginx/config"
+	"k8s.io/contrib/ingress/controllers/nginx/nginx/cors"
 	"k8s.io/contrib/ingress/controllers/nginx/nginx/healthcheck"
 	"k8s.io/contrib/ingress/controllers/nginx/nginx/ingress"
 	"k8s.io/contrib/ingress/controllers/nginx/nginx/ipwhitelist"
@@ -717,6 +718,11 @@ func (lbc *loadBalancerController) getUpstreamServers(ngxCfg config.Configuratio
 				glog.V(3).Infof("error reading white list annotation in Ingress %v/%v: %v", ing.GetNamespace(), ing.GetName(), err)
 			}
 
+			eCORS, err := cors.ParseAnnotations(ing)
+			if err != nil {
+				glog.V(3).Infof("error reading CORS annotation in Ingress %v/%v: %v", ing.GetNamespace(), ing.GetName(), err)
+			}
+
 			host := rule.Host
 			if host == "" {
 				host = defServerName
@@ -749,6 +755,7 @@ func (lbc *loadBalancerController) getUpstreamServers(ngxCfg config.Configuratio
 						loc.Redirect = *locRew
 						loc.SecureUpstream = secUpstream
 						loc.Whitelist = *wl
+						loc.EnableCORS = eCORS
 
 						addLoc = false
 						continue
@@ -763,7 +770,6 @@ func (lbc *loadBalancerController) getUpstreamServers(ngxCfg config.Configuratio
 				}
 
 				if addLoc {
-
 					server.Locations = append(server.Locations, &ingress.Location{
 						Path:           nginxPath,
 						Upstream:       *ups,
@@ -772,6 +778,7 @@ func (lbc *loadBalancerController) getUpstreamServers(ngxCfg config.Configuratio
 						Redirect:       *locRew,
 						SecureUpstream: secUpstream,
 						Whitelist:      *wl,
+						EnableCORS:     eCORS,
 					})
 				}
 			}

ingress/controllers/nginx/nginx.tmpl

@@ -228,6 +228,10 @@ http {
             proxy_set_header Authorization "";
             {{- end }}
 
+            {{ if $location.EnableCORS }}
+            {{ template "CORS" }}
+            {{ end }}
+
             proxy_set_header Host                   $host;
 
             # Pass Real IP
@@ -374,3 +378,38 @@ stream {
         }    
         {{ end }}
 {{ end }}
+
+{{/* CORS support from https://michielkalkman.com/snippets/nginx-cors-open-configuration.html */}}
+{{ define "CORS" }}
+     if ($request_method = 'OPTIONS') {
+        add_header 'Access-Control-Allow-Origin' '*';
+        #
+        # Om nom nom cookies
+        #
+        add_header 'Access-Control-Allow-Credentials' 'true';
+        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
+        #
+        # Custom headers and headers various browsers *should* be OK with but aren't
+        #
+        add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type';
+        #
+        # Tell client that this pre-flight info is valid for 20 days
+        #
+        add_header 'Access-Control-Max-Age' 1728000;
+        add_header 'Content-Type' 'text/plain charset=UTF-8';
+        add_header 'Content-Length' 0;
+        return 204;
+     }
+     if ($request_method = 'POST') {
+        add_header 'Access-Control-Allow-Origin' '*';
+        add_header 'Access-Control-Allow-Credentials' 'true';
+        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
+        add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type';
+     }
+     if ($request_method = 'GET') {
+        add_header 'Access-Control-Allow-Origin' '*';
+        add_header 'Access-Control-Allow-Credentials' 'true';
+        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
+        add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type';
+     }
+{{ end }}

ingress/controllers/nginx/nginx/cors/main.go

@@ -0,0 +1,50 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package cors
+
+import (
+	"errors"
+	"strconv"
+
+	"k8s.io/kubernetes/pkg/apis/extensions"
+)
+
+const (
+	cors = "ingress.kubernetes.io/enable-cors"
+)
+
+type ingAnnotations map[string]string
+
+func (a ingAnnotations) cors() bool {
+	val, ok := a[cors]
+	if ok {
+		if b, err := strconv.ParseBool(val); err == nil {
+			return b
+		}
+	}
+	return false
+}
+
+// ParseAnnotations parses the annotations contained in the ingress
+// rule used to indicate if the upstream servers should use SSL
+func ParseAnnotations(ing *extensions.Ingress) (bool, error) {
+	if ing.GetAnnotations() == nil {
+		return false, errors.New("no annotations present")
+	}
+
+	return ingAnnotations(ing.GetAnnotations()).cors(), nil
+}

ingress/controllers/nginx/nginx/ingress/nginx.go

@@ -101,6 +101,7 @@ type Location struct {
 	Redirect       rewrite.Redirect
 	SecureUpstream bool
 	Whitelist      ipwhitelist.SourceRange
+	EnableCORS     bool
 }
 
 // LocationByPath sorts location by path