Add reactive CsrfRequestDataValueProcessor

Fixes gh-4762

web/src/main/java/org/springframework/security/web/reactive/result/view/CsrfRequestDataValueProcessor.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2002-2017 the original author or 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 org.springframework.security.web.reactive.result.view;
+
+import org.springframework.lang.NonNull;
+import org.springframework.security.web.server.csrf.CsrfToken;
+import org.springframework.web.reactive.result.view.RequestDataValueProcessor;
+import org.springframework.web.server.ServerWebExchange;
+
+import java.util.Collections;
+import java.util.Map;
+import java.util.regex.Pattern;
+
+/**
+ * @author Rob Winch
+ * @since 5.0
+ */
+public class CsrfRequestDataValueProcessor implements RequestDataValueProcessor {
+
+	private static final Pattern DISABLE_CSRF_TOKEN_PATTERN = Pattern
+		.compile("(?i)^(GET|HEAD|TRACE|OPTIONS)$");
+
+	private static final String DISABLE_CSRF_TOKEN_ATTR = "DISABLE_CSRF_TOKEN_ATTR";
+
+	@Override
+	public String processAction(ServerWebExchange exchange, String action,
+		String httpMethod) {
+		if (httpMethod != null && DISABLE_CSRF_TOKEN_PATTERN.matcher(httpMethod).matches()) {
+			exchange.getAttributes().put(DISABLE_CSRF_TOKEN_ATTR, Boolean.TRUE);
+		}
+		else {
+			exchange.getAttributes().remove(DISABLE_CSRF_TOKEN_ATTR);
+		}
+		return action;
+	}
+
+	@Override
+	public String processFormFieldValue(ServerWebExchange exchange,
+		String name, String value, String type) {
+		return value;
+	}
+
+	@NonNull
+	@Override
+	public Map<String, String> getExtraHiddenFields(
+		ServerWebExchange exchange) {
+		if (Boolean.TRUE.equals(exchange.getAttribute(DISABLE_CSRF_TOKEN_ATTR))) {
+			exchange.getAttributes().remove(DISABLE_CSRF_TOKEN_ATTR);
+			return Collections.emptyMap();
+		}
+		CsrfToken token = exchange.getAttribute(CsrfToken.class.getName());
+		if(token == null) {
+			return Collections.emptyMap();
+		}
+		return Collections.singletonMap(token.getParameterName(), token.getToken());
+	}
+
+	@Override
+	public String processUrl(ServerWebExchange exchange, String url) {
+		return url;
+	}
+}