禁止对已编码请求包重复编码，禁止对未编码请求包解码

Author: c0ny1

src/main/java/burp/BurpExtender.java

@@ -4,7 +4,7 @@
 
 public class BurpExtender implements IBurpExtender,IHttpListener,IProxyListener {
     public static IBurpExtenderCallbacks callbacks;
-    private IExtensionHelpers helpers;
+    public static IExtensionHelpers helpers;
     private String extensionName = "Chunked coding converter";
     private String version ="0.1";
     public static PrintWriter stdout;

src/main/java/burp/Config.java

@@ -33,7 +33,6 @@ public static void setMin_chunked_len(Integer min_chunked_len) {
 
     public static Integer getMax_chunked_len() {
         String val = BurpExtender.callbacks.loadExtensionSetting("max_chunked_len");
-        BurpExtender.stdout.println("[+] max_chunked_len: " + val);
         try {
             return Integer.valueOf(val);
         }catch(Exception e){

src/main/java/burp/Menu.java

@@ -51,6 +51,12 @@ public void actionPerformed(ActionEvent arg0) {
                     return;
                 }
 
+                // 不重复编码
+                if(Transfer.isChunked(iReqResp)){
+                    JOptionPane.showConfirmDialog(null,"The request has been chunked encoded，Do not repeat the encoding！","Warning",JOptionPane.CLOSED_OPTION,JOptionPane.WARNING_MESSAGE);
+                    return;
+                }
+
                 try {
                     byte[] request = Transfer.encoding(m_helpers, iReqResp, Config.getMin_chunked_len(),Config.getMax_chunked_len(),Config.isAddComment(),Config.getMin_comment_len(),Config.getMax_comment_len());
                     if (request != null) {
@@ -66,6 +72,13 @@ public void actionPerformed(ActionEvent arg0) {
 
             public void actionPerformed(ActionEvent arg0) {
                 IHttpRequestResponse iReqResp = invocation.getSelectedMessages()[0];
+
+                // 进制对未编码请求解码
+                if(!Transfer.isChunked(iReqResp)){
+                    JOptionPane.showConfirmDialog(null,"The request is unencoded and cannot be decoded!","Warning",JOptionPane.CLOSED_OPTION,JOptionPane.WARNING_MESSAGE);
+                    return;
+                }
+
                 try {
                     byte[] request = Transfer.decoding(m_helpers,iReqResp);
                     if (request != null) {

src/main/java/burp/Transfer.java

@@ -15,6 +15,18 @@ public static  byte[] encoding(IExtensionHelpers helpers, IHttpRequestResponse r
             return request;
         }
 
+        List<String> headers = helpers.analyzeRequest(request).getHeaders();
+        Iterator<String> iter = headers.iterator();
+        while (iter.hasNext()) {
+            //不对请求包重复编码
+            if (((String)iter.next()).contains("Transfer-Encoding")) {
+                return request;
+            }
+        }
+        //Add Transfer-Encoding header
+        headers.add("Transfer-Encoding: chunked");
+
+        //encoding
         List<String> str_list = Util.getStrList1(body,minChunkedLen,maxChunkedLen);
         String encoding_body = "";
         for(String str:str_list){
@@ -30,15 +42,8 @@ public static  byte[] encoding(IExtensionHelpers helpers, IHttpRequestResponse r
         }
         encoding_body += "0\r\n\r\n";
 
-        List<String> headers = helpers.analyzeRequest(request).getHeaders();
 
-        Iterator<String> iter = headers.iterator();
-        while (iter.hasNext()) {
-            if (((String)iter.next()).contains("Transfer-Encoding")) {
-                iter.remove();
-            }
-        }
-        headers.add("Transfer-Encoding: chunked");
+
         return helpers.buildHttpMessage(headers,encoding_body.getBytes());
     }
 
@@ -48,7 +53,22 @@ public static byte[] decoding(IExtensionHelpers helpers, IHttpRequestResponse re
         int bodyOffset = requestInfo.getBodyOffset();
         String body = new String(request, bodyOffset, request.length - bodyOffset, "UTF-8");
 
-        // decoding
+        // Delete Transfer-Encoding header
+        List<String> headers = helpers.analyzeRequest(request).getHeaders();
+        Iterator<String> iter = headers.iterator();
+        Boolean isChunked = false;//是否被分块编码过
+        while (iter.hasNext()) {
+            if (((String)iter.next()).contains("Transfer-Encoding")) {
+                iter.remove();
+                isChunked = true;
+            }
+        }
+        //不对未编码过的请求包解码
+        if(!isChunked){
+            return request;
+        }
+
+        //Decoding
         String[] array_body = body.split("\r\n");
         List<String> list_string_body = Arrays.asList(array_body);
         List list_body = new ArrayList(list_string_body);
@@ -61,15 +81,23 @@ public static byte[] decoding(IExtensionHelpers helpers, IHttpRequestResponse re
             }
         }
 
-        // del Transfer-Encoding header
-        List<String> headers = helpers.analyzeRequest(request).getHeaders();
+        return helpers.buildHttpMessage(headers,decoding_body.getBytes());
+    }
+
+    /**
+     * 通过数据包头部是否存在Transfer-Encoding头，来判断其是否被编码
+     * @param requestResponse
+     * @return 是否被编码
+     */
+    public static boolean isChunked(IHttpRequestResponse requestResponse){
+        byte[] request = requestResponse.getRequest();
+        List<String> headers = BurpExtender.helpers.analyzeRequest(request).getHeaders();
         Iterator<String> iter = headers.iterator();
         while (iter.hasNext()) {
             if (((String)iter.next()).contains("Transfer-Encoding")) {
-                iter.remove();
+                return true;
             }
         }
-
-        return helpers.buildHttpMessage(headers,decoding_body.getBytes());
+        return false;
     }
 }