add support for {{.Origin}} in proxy response handler

Signed-off-by: Ronni Skansing <rskansing@gmail.com>

backend/proxy/proxy.go

@@ -3658,8 +3658,19 @@ func (m *ProxyHandler) createResponseFromRule(rule service.ProxyServiceResponseR
 		Request:    req,
 	}
 
-	// set headers
+	// set headers with support for {{.Origin}} interpolation
+	requestOrigin := req.Header.Get("Origin")
 	for name, value := range rule.Headers {
+		// support {{.Origin}} placeholder to echo back the request's origin header
+		// this is useful for cors when credentials mode is 'include' and wildcard '*' is not allowed
+		if strings.Contains(value, "{{.Origin}}") {
+			if requestOrigin != "" {
+				value = strings.ReplaceAll(value, "{{.Origin}}", requestOrigin)
+			} else {
+				// if no origin header present, skip this header
+				continue
+			}
+		}
 		resp.Header.Set(name, value)
 	}
 

frontend/src/lib/components/proxy/ProxyConfigBuilder.svelte

@@ -2114,18 +2114,21 @@
 																	{/each}
 																</div>
 															{/if}
+															<span class="form-hint"
+																>Use <code>{'{{.Origin}}'}</code> to echo the request's Origin header</span
+															>
 														</div>
 													</div>
 													<div class="field-wrapper checkbox-wrapper">
 														<label class="checkbox-label">
 															<input
 																type="checkbox"
-																checked={rule.forward}
+																bind:checked={rule.forward}
+																class="checkbox-input"
 																on:change={(e) => {
 																	rule.forward = e.currentTarget.checked;
 																	configData = configData;
 																}}
-																class="checkbox-input"
 															/>
 															<span class="checkbox-text">Forward to target</span>
 														</label>
@@ -2884,13 +2887,16 @@
 																{/each}
 															</div>
 														{/if}
+														<span class="form-hint"
+															>Use <code>{'{{.Origin}}'}</code> to echo the request's Origin header</span
+														>
 													</div>
 												</div>
 												<div class="field-wrapper checkbox-wrapper">
 													<label class="checkbox-label">
 														<input
 															type="checkbox"
-															checked={rule.forward}
+															bind:checked={rule.forward}
 															on:change={(e) => {
 																rule.forward = e.currentTarget.checked;
 																configData = configData;