ABP/Android proxy service

src/org/adblockplus/brazil/RequestHandler.java

Index: src/org/adblockplus/brazil/RequestHandler.java
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+package org.adblockplus.brazil;
+
+import java.io.EOFException;
+import java.io.FilterInputStream;
+import java.io.FilterOutputStream;
+import java.io.IOException;
+import java.io.InterruptedIOException;
+import java.io.OutputStream;
+import java.net.ConnectException;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.UnknownHostException;
+import java.util.List;
+import java.util.Properties;
+import java.util.zip.GZIPInputStream;
+import java.util.zip.InflaterInputStream;
+
+import org.adblockplus.ChunkedOutputStream;
+import org.adblockplus.android.AdblockPlus;
+import org.literateprograms.BoyerMoore;
+
+import sunlabs.brazil.server.Handler;
+import sunlabs.brazil.server.Request;
+import sunlabs.brazil.server.Server;
+import sunlabs.brazil.util.MatchString;
+import sunlabs.brazil.util.http.HttpInputStream;
+import sunlabs.brazil.util.http.HttpRequest;
+import sunlabs.brazil.util.http.MimeHeaders;
+import android.util.Log;
+
+/**
+ * The <code>RequestHandler</code> implements a proxy service optionally
+ * modifying output.
+ * The following configuration parameters are used to initialize this
+ * <code>Handler</code>:
+ * <dl class=props>
+ * 
+ * <dt>prefix, suffix, glob, match
+ * <dd>Specify the URL that triggers this handler. (See {@link MatchString}).
+ * <dt>auth
+ * <dd>The value of the proxy-authenticate header (if any) sent to the upstream
+ * proxy
+ * <dt>proxyHost
+ * <dd>If specified, the name of the upstream proxy
+ * <dt>proxyPort
+ * <dd>The upstream proxy port, if a proxyHost is specified (defaults to 80)
+ * <dt>proxylog
+ * <dd>If set all http headers will be logged to the console. This is for
+ * debugging.
+ * 
+ * </dl>
+ * 
+ * A sample set of configuration parameters illustrating how to use this
+ * handler follows:
+ * 
+ * <pre>
+ * handler=adblock
+ * adblock.class=org.adblockplus.brazil.RequestHandler
+ * </pre>
+ * 
+ * See the description under {@link sunlabs.brazil.server.Handler#respond
+ * respond} for a more detailed explanation.
+ */
+
+public class RequestHandler implements Handler
+{
+  public static final String PROXY_HOST = "proxyHost";
+  public static final String PROXY_PORT = "proxyPort";
+  public static final String AUTH = "auth";
+
+  private AdblockPlus application;
+  private String prefix;
+
+  private String via;
+
+  private String proxyHost;
+  private int proxyPort = 80;
+  private String auth;
+
+  private boolean shouldLog; // if true, log all headers

[Felix Dahlke, 2012/11/09 06:04:32]

Maybe call it shouldLogHeaders then? That'd make the comment redundant. I'm not
a fan of comments where naming suffices, I've seen them get invalid over time
way too often.

[Andrey Novikov, 2012/11/09 09:23:47]

Done.

+
+  @Override
+  public boolean init(Server server, String prefix)
+  {
+    this.prefix = prefix;
+    application = AdblockPlus.getApplication();
+
+    Properties props = server.props;
+
+    proxyHost = props.getProperty(prefix + PROXY_HOST);
+
+    String s = props.getProperty(prefix + PROXY_PORT);
+    try
+    {
+      proxyPort = Integer.decode(s).intValue();
+    }
+    catch (Exception e)
+    {

[Felix Dahlke, 2012/11/09 06:04:32]

It seems this case occurs when the port is not set, so it's not an error worth
logging. I'd like a small comment like "// Use the default port" though.

[Andrey Novikov, 2012/11/09 09:23:47]

Done.

+    }
+
+    auth = props.getProperty(prefix + AUTH);
+
+    shouldLog = (props.getProperty(prefix + "proxylog") != null);
+
+    via = " " + server.hostName + ":" + server.listen.getLocalPort() + " (" + server.name + ")";
+
+    return true;
+  }
+
+  @Override
+  public boolean respond(Request request) throws IOException
+  {
+    boolean block = false;
+    String reqHost = null;
+    String refHost = null;
+
+    try
+    {
+      reqHost = (new URL(request.url)).getHost();
+      refHost = (new URL(request.getRequestHeader("referer"))).getHost();
+    }
+    catch (MalformedURLException e)
+    {

[Felix Dahlke, 2012/11/09 06:04:32]

Can we really safely go on in this case? At least worth a comment IMO.

[Andrey Novikov, 2012/11/09 09:23:47]

We are transparent, it's not our deal if it's malformed. Just have to catch
because of Java API. 

[Felix Dahlke, 2012/11/09 14:40:46]

Hm, but should we just go on with a null reqHost and/or refHost?

[Andrey Novikov, 2012/11/12 08:53:12]

In fact this exception is for referrer, request can hardly be malformed at this
point, it should be processed earlier by third-party code. I can split it in two
catches if you wish.

+    }
+
+    try
+    {
+      block = application.matches(request.url, request.query, reqHost, refHost, request.getRequestHeader("accept"));
+    }
+    catch (Exception e)
+    {
+      Log.e(prefix, "Filter error", e);
+    }
+
+    request.log(Server.LOG_LOG, prefix, block + ": " + request.url);
+
+    if (block)
+    {
+      request.sendError(502, "Blocked by Adblock Plus");
+      return true;
+    }
+
+    // Do not further process non-http requests
+    if (request.url.startsWith("http:") == false && request.url.startsWith("https:") == false)

[Felix Dahlke, 2012/11/09 06:04:32]

How about if (!request.url.matches("^https?:")) ?

[Andrey Novikov, 2012/11/09 09:23:47]

I thought it would be faster...

[Felix Dahlke, 2012/11/09 14:40:46]

Premature optimisation? :) I think you should go with whatever you find most
readable, unless there is an actual issue.

[Andrey Novikov, 2012/11/12 08:53:12]

Done.

+    {
+      return false;
+    }
+
+    String url = request.url;
+
+    if ((request.query != null) && (request.query.length() > 0))
+    {
+      url += "?" + request.query;
+    }
+
+    int count = request.server.requestCount;
+    if (shouldLog)
+    {
+      System.err.println(dumpHeaders(count, request, request.headers, true));
+    }
+
+    /*
+     * "Proxy-Connection" may be used (instead of just "Connection")
+     * to keep alive a connection between a client and this proxy.
+     */
+    String pc = request.headers.get("Proxy-Connection");
+    if (pc != null)
+    {
+      request.connectionHeader = "Proxy-Connection";
+      request.keepAlive = pc.equalsIgnoreCase("Keep-Alive");
+    }
+
+    HttpRequest.removePointToPointHeaders(request.headers, false);
+
+    HttpRequest target = new HttpRequest(url);
+    try
+    {
+      target.setMethod(request.method);
+      request.headers.copyTo(target.requestHeaders);
+
+      if (proxyHost != null)
+      {
+        target.setProxy(proxyHost, proxyPort);
+        if (auth != null)
+        {
+          target.requestHeaders.add("Proxy-Authorization", auth);
+        }
+      }
+
+      if (request.postData != null)
+      {
+        OutputStream out = target.getOutputStream();
+        out.write(request.postData);
+        out.close();
+      }
+
+      target.connect();
+
+      if (shouldLog)
+      {
+        System.err.println("      " + target.status + "\n" + dumpHeaders(count, request, target.responseHeaders, false));
+      }
+      HttpRequest.removePointToPointHeaders(target.responseHeaders, true);
+
+      request.setStatus(target.getResponseCode());
+      target.responseHeaders.copyTo(request.responseHeaders);
+      try
+      {
+        request.responseHeaders.add("Via", target.status.substring(0, 8) + via);
+      }
+      catch (StringIndexOutOfBoundsException e)
+      {
+        request.responseHeaders.add("Via", via);
+      }
+
+      // Detect if we need to add ElemHide filters
+      String type = request.responseHeaders.get("Content-Type");
+
+      String selectors = null;
+      if (type != null && type.toLowerCase().startsWith("text/html"))
+      {
+        selectors = application.getSelectorsForDomain(reqHost);
+      }
+      // If no filters are applicable just pass through the response
+      if (selectors == null || target.getResponseCode() != 200)
+      {
+        int contentLength = target.getContentLength();
+        if (contentLength == 0)
+        {
+          // we do not use request.sendResponse to avoid arbitrary
+          // 200 -> 204 response code conversion
+          request.sendHeaders(-1, null, -1);
+        }
+        else
+        {
+          request.sendResponse(target.getInputStream(), contentLength, null, -1);
+        }
+      }
+      // Insert filters otherwise
+      else
+      {
+        HttpInputStream his = target.getInputStream();
+        int size = target.getContentLength();
+        if (size < 0)
+        {
+          size = Integer.MAX_VALUE;
+        }
+
+        FilterInputStream in = null;
+        FilterOutputStream out = null;
+
+        // Detect if content needs decoding
+        String encodingHeader = request.responseHeaders.get("Content-Encoding");
+        if (encodingHeader != null)
+        {
+          encodingHeader = encodingHeader.toLowerCase();
+          if (encodingHeader.equals("gzip") || encodingHeader.equals("x-gzip"))
+          {
+            in = new GZIPInputStream(his);
+          }
+          else if (encodingHeader.equals("compress") || encodingHeader.equals("x-compress"))
+          {
+            in = new InflaterInputStream(his);
+          }
+          else
+          {
+            // Unsupported encoding, proxy content as-is
+            in = his;
+            out = request.out;
+            selectors = null;
+          }
+        }
+        else
+        {
+          in = his;
+        }
+        // Use chunked encoding when injecting filters in page
+        if (out == null)
+        {
+          request.responseHeaders.remove("Content-Length");
+          request.responseHeaders.remove("Content-Encoding");
+          out = new ChunkedOutputStream(request.out);
+          request.responseHeaders.add("Transfer-Encoding", "chunked");
+          size = Integer.MAX_VALUE;
+        }
+
+        request.sendHeaders(-1, null, -1);
+
+        byte[] buf = new byte[Math.min(4096, size)];
+
+        Log.e(prefix, request.url);

[Felix Dahlke, 2012/11/09 06:04:32]

Log.d()?

[Andrey Novikov, 2012/11/09 09:23:47]

Done.

+
+        boolean sent = selectors == null;
+        // TODO Do we need to set encoding here?
+        BoyerMoore matcher = new BoyerMoore("<html".getBytes());
+
+        while (size > 0)
+        {
+          out.flush();
+
+          count = in.read(buf, 0, Math.min(buf.length, size));
+          if (count < 0)
+          {
+            break;
+          }
+          size -= count;
+          try
+          {
+            // Search for <html> tag
+            if (!sent && count > 0)
+            {
+              List<Integer> matches = matcher.match(buf, 0, count);
+              if (!matches.isEmpty())
+              {
+                // TODO Do we need to set encoding here?
+                byte[] addon = selectors.getBytes();
+                // Add filters right before match
+                int m = matches.get(0);
+                out.write(buf, 0, m);
+                out.write(addon);
+                out.write(buf, m, count - m);
+                sent = true;
+                continue;
+              }
+            }
+            out.write(buf, 0, count);
+          }
+          catch (IOException e)
+          {
+            break;
+          }
+        }
+        // The correct way would be to close ChunkedOutputStream
+        // but we can not do it because underlying output stream is
+        // used later in caller code. So we use this ugly hack:
+        try
+        {
+          ((ChunkedOutputStream) out).writeFinalChunk();

[Felix Dahlke, 2012/11/09 06:04:32]

Why use instanceof? That would avoid class cast exceptions.

[Andrey Novikov, 2012/11/09 09:23:47]

Done.

+        }
+        catch (ClassCastException e)
+        {
+          // ignore
+        }
+      }
+    }
+    catch (InterruptedIOException e)
+    {
+      /*
+       * Read timeout while reading from the remote side. We use a
+       * read timeout in case the target never responds.
+       */
+      request.sendError(408, "Timeout / No response");
+    }
+    catch (EOFException e)
+    {
+      request.sendError(500, "No response");
+    }
+    catch (UnknownHostException e)
+    {
+      request.sendError(500, "Unknown host");
+    }
+    catch (ConnectException e)
+    {
+      request.sendError(500, "Connection refused");
+    }
+    catch (IOException e)
+    {
+      /*
+       * An IOException will happen if we can't communicate with the
+       * target or the client. Rather than attempting to discriminate,
+       * just send an error message to the client, and let the send
+       * fail if the client was the one that was in error.
+       */
+
+      String msg = "Error from proxy";
+      if (e.getMessage() != null)
+      {
+        msg += ": " + e.getMessage();
+      }
+      request.sendError(500, msg);
+      Log.e(prefix, msg, e);
+    }
+    finally
+    {
+      target.close();
+    }
+    return true;
+  }
+
+  /**
+   * Dump the headers on stderr
+   */
+  public static String dumpHeaders(int count, Request request, MimeHeaders headers, boolean sent)
+  {
+    String prompt;
+    StringBuffer sb = new StringBuffer();
+    String label = "   " + count;
+    label = label.substring(label.length() - 4);
+    if (sent)
+    {
+      prompt = label + "> ";
+      sb.append(prompt).append(request.toString()).append("\n");
+    }
+    else
+    {
+      prompt = label + "< ";
+    }
+
+    for (int i = 0; i < headers.size(); i++)
+    {
+      sb.append(prompt).append(headers.getKey(i));
+      sb.append(": ").append(headers.get(i)).append("\n");
+    }
+    return (sb.toString());
+  }
+}