package kornell.server;
/**
* Copyright MITRE
*
* 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.
*/
import java.io.Closeable;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.reflect.Constructor;
import java.net.URI;
import java.util.BitSet;
import java.util.Enumeration;
import java.util.Formatter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpEntityEnclosingRequest;
import org.apache.http.HttpHeaders;
import org.apache.http.HttpHost;
import org.apache.http.HttpRequest;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.AbortableHttpRequest;
import org.apache.http.client.params.ClientPNames;
import org.apache.http.client.utils.URIUtils;
import org.apache.http.entity.InputStreamEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;
import org.apache.http.message.BasicHeader;
import org.apache.http.message.BasicHttpEntityEnclosingRequest;
import org.apache.http.message.BasicHttpRequest;
import org.apache.http.message.HeaderGroup;
import org.apache.http.params.BasicHttpParams;
import org.apache.http.params.HttpParams;
import org.apache.http.util.EntityUtils;
/**
* An HTTP reverse proxy/gateway servlet. It is designed to be extended for customization
* if desired. Most of the work is handled by
* <a href="http://hc.apache.org/httpcomponents-client-ga/">Apache HttpClient</a>.
* <p>
* There are alternatives to a servlet based proxy such as Apache mod_proxy if that is available to you. However
* this servlet is easily customizable by Java, secure-able by your web application's security (e.g. spring-security),
* portable across servlet engines, and is embeddable into another web application.
* </p>
* <p>
* Inspiration: http://httpd.apache.org/docs/2.0/mod/mod_proxy.html
* </p>
*
* @author David Smiley dsmiley@mitre.org
*/
@SuppressWarnings({"rawtypes","deprecation", "serial","resource","unchecked"})
public class ProxyServlet extends HttpServlet {
/* INIT PARAMETER NAME CONSTANTS */
/** A boolean parameter name to enable logging of input and target URLs to the servlet log. */
public static final String P_LOG = "log";
/** A boolean parameter name to enable forwarding of the client IP */
public static final String P_FORWARDEDFOR = "forwardip";
/** The parameter name for the target (destination) URI to proxy to. */
private static final String P_TARGET_URI = "targetUri";
/* MISC */
protected boolean doLog = false;
protected boolean doForwardIP = true;
/** User agents shouldn't send the url fragment but what if it does? */
protected boolean doSendUrlFragment = true;
protected URI targetUriObj;
/** targetUriObj.toString() */
protected String targetUri;
protected HttpClient proxyClient;
@Override
public String getServletInfo() {
return "A proxy servlet by David Smiley, dsmiley@mitre.org";
}
@Override
public void init(ServletConfig servletConfig) throws ServletException {
super.init(servletConfig);
String doLogStr = servletConfig.getInitParameter(P_LOG);
if (doLogStr != null) {
this.doLog = Boolean.parseBoolean(doLogStr);
}
String doForwardIPString = servletConfig.getInitParameter(P_FORWARDEDFOR);
if (doForwardIPString != null) {
this.doForwardIP = Boolean.parseBoolean(doForwardIPString);
}
try {
targetUriObj = new URI(servletConfig.getInitParameter(P_TARGET_URI));
} catch (Exception e) {
throw new RuntimeException("Trying to process targetUri init parameter: "+e,e);
}
targetUri = targetUriObj.toString();
HttpParams hcParams = new BasicHttpParams();
readConfigParam(hcParams, ClientPNames.HANDLE_REDIRECTS, Boolean.class);
proxyClient = createHttpClient(hcParams);
}
/** Called from {@link #init(javax.servlet.ServletConfig)}. HttpClient offers many opportunities
* for customization. By default, SystemDefaultHttpClient is used available, otherwise it falls
* back to:
* <pre>new DefaultHttpClient(new ThreadSafeClientConnManager(),hcParams)</pre>*/
protected HttpClient createHttpClient(HttpParams hcParams) {
try {
//as of HttpComponents v4.2, this class is better since it uses System
// Properties:
Class clientClazz = Class.forName("org.apache.http.impl.client.SystemDefaultHttpClient");
Constructor constructor = clientClazz.getConstructor(HttpParams.class);
return (HttpClient) constructor.newInstance(hcParams);
} catch (ClassNotFoundException e) {
//no problem; use v4.1 below
} catch (Exception e) {
throw new RuntimeException(e);
}
//Fallback on using older client:
return new DefaultHttpClient(new ThreadSafeClientConnManager(), hcParams);
}
protected void readConfigParam(HttpParams hcParams, String hcParamName, Class type) {
String val_str = getServletConfig().getInitParameter(hcParamName);
if (val_str == null)
return;
Object val_obj;
if (type == String.class) {
val_obj = val_str;
} else {
try {
//noinspection unchecked
val_obj = type.getMethod("valueOf",String.class).invoke(type,val_str);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
hcParams.setParameter(hcParamName,val_obj);
}
@Override
public void destroy() {
//As of HttpComponents v4.3, clients implement closeable
if (proxyClient instanceof Closeable) {//TODO AutoCloseable in Java 1.6
try {
((Closeable) proxyClient).close();
} catch (IOException e) {
log("While destroying servlet, shutting down httpclient: "+e, e);
}
} else {
//Older releases require we do this:
if (proxyClient != null)
proxyClient.getConnectionManager().shutdown();
}
super.destroy();
}
@Override
protected void service(HttpServletRequest servletRequest, HttpServletResponse servletResponse)
throws ServletException, IOException {
// Make the Request
//note: we won't transfer the protocol version because I'm not sure it would truly be compatible
String method = servletRequest.getMethod();
String proxyRequestUri = rewriteUrlFromRequest(servletRequest);
HttpRequest proxyRequest;
//spec: RFC 2616, sec 4.3: either of these two headers signal that there is a message body.
if (servletRequest.getHeader(HttpHeaders.CONTENT_LENGTH) != null ||
servletRequest.getHeader(HttpHeaders.TRANSFER_ENCODING) != null) {
HttpEntityEnclosingRequest eProxyRequest = new BasicHttpEntityEnclosingRequest(method, proxyRequestUri);
// Add the input entity (streamed)
// note: we don't bother ensuring we close the servletInputStream since the container handles it
eProxyRequest.setEntity(new InputStreamEntity(servletRequest.getInputStream(), servletRequest.getContentLength()));
proxyRequest = eProxyRequest;
} else
proxyRequest = new BasicHttpRequest(method, proxyRequestUri);
copyRequestHeaders(servletRequest, proxyRequest);
setXForwardedForHeader(servletRequest, proxyRequest);
HttpResponse proxyResponse = null;
try {
// Execute the request
if (doLog) {
log("proxy " + method + " uri: " + servletRequest.getRequestURI() + " -- " + proxyRequest.getRequestLine().getUri());
}
proxyResponse = proxyClient.execute(URIUtils.extractHost(targetUriObj), proxyRequest);
// Process the response
int statusCode = proxyResponse.getStatusLine().getStatusCode();
if (doResponseRedirectOrNotModifiedLogic(servletRequest, servletResponse, proxyResponse, statusCode)) {
//the response is already "committed" now without any body to send
//TODO copy response headers?
return;
}
// Pass the response code. This method with the "reason phrase" is deprecated but it's the only way to pass the
// reason along too.
//noinspection deprecation
servletResponse.setStatus(statusCode, proxyResponse.getStatusLine().getReasonPhrase());
copyResponseHeaders(proxyResponse, servletResponse);
// Send the content to the client
copyResponseEntity(proxyResponse, servletResponse);
} catch (Exception e) {
//abort request, according to best practice with HttpClient
if (proxyRequest instanceof AbortableHttpRequest) {
AbortableHttpRequest abortableHttpRequest = (AbortableHttpRequest) proxyRequest;
abortableHttpRequest.abort();
}
if (e instanceof RuntimeException)
throw (RuntimeException)e;
if (e instanceof ServletException)
throw (ServletException)e;
//noinspection ConstantConditions
if (e instanceof IOException)
throw (IOException) e;
throw new RuntimeException(e);
} finally {
// make sure the entire entity was consumed, so the connection is released
if (proxyResponse != null)
consumeQuietly(proxyResponse.getEntity());
if (proxyResponse != null)
closeQuietly(servletResponse.getOutputStream());
}
}
protected boolean doResponseRedirectOrNotModifiedLogic(
HttpServletRequest servletRequest, HttpServletResponse servletResponse,
HttpResponse proxyResponse, int statusCode)
throws ServletException, IOException {
// Check if the proxy response is a redirect
// The following code is adapted from org.tigris.noodle.filters.CheckForRedirect
if (statusCode >= HttpServletResponse.SC_MULTIPLE_CHOICES /* 300 */
&& statusCode < HttpServletResponse.SC_NOT_MODIFIED /* 304 */) {
Header locationHeader = proxyResponse.getLastHeader(HttpHeaders.LOCATION);
if (locationHeader == null) {
throw new ServletException("Received status code: " + statusCode
+ " but no " + HttpHeaders.LOCATION + " header was found in the response");
}
// Modify the redirect to go to this proxy servlet rather that the proxied host
String locStr = rewriteUrlFromResponse(servletRequest, locationHeader.getValue());
servletResponse.sendRedirect(locStr);
return true;
}
// 304 needs special handling. See:
// http://www.ics.uci.edu/pub/ietf/http/rfc1945.html#Code304
// We get a 304 whenever passed an 'If-Modified-Since'
// header and the data on disk has not changed; server
// responds w/ a 304 saying I'm not going to send the
// body because the file has not changed.
if (statusCode == HttpServletResponse.SC_NOT_MODIFIED) {
servletResponse.setIntHeader(HttpHeaders.CONTENT_LENGTH, 0);
servletResponse.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
return true;
}
return false;
}
protected void closeQuietly(Closeable closeable) {
try {
if(closeable != null) closeable.close();
} catch (IOException e) {
//TODO: Understand and solve log(e.getMessage(), e);
}
}
/** HttpClient v4.1 doesn't have the
* {@link org.apache.http.util.EntityUtils#consumeQuietly(org.apache.http.HttpEntity)} method. */
protected void consumeQuietly(HttpEntity entity) {
try {
EntityUtils.consume(entity);
} catch (IOException e) {//ignore
log(e.getMessage(), e);
}
}
/** These are the "hop-by-hop" headers that should not be copied.
* http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html
* I use an HttpClient HeaderGroup class instead of Set<String> because this
* approach does case insensitive lookup faster.
*/
protected static final HeaderGroup hopByHopHeaders;
static {
hopByHopHeaders = new HeaderGroup();
String[] headers = new String[] {
"Connection", "Keep-Alive", "Proxy-Authenticate", "Proxy-Authorization",
"TE", "Trailers", "Transfer-Encoding", "Upgrade" };
for (String header : headers) {
hopByHopHeaders.addHeader(new BasicHeader(header, null));
}
}
/** Copy request headers from the servlet client to the proxy request. */
protected void copyRequestHeaders(HttpServletRequest servletRequest, HttpRequest proxyRequest) {
// Get an Enumeration of all of the header names sent by the client
Enumeration enumerationOfHeaderNames = servletRequest.getHeaderNames();
while (enumerationOfHeaderNames.hasMoreElements()) {
String headerName = (String) enumerationOfHeaderNames.nextElement();
//Instead the content-length is effectively set via InputStreamEntity
if (headerName.equalsIgnoreCase(HttpHeaders.CONTENT_LENGTH))
continue;
if (hopByHopHeaders.containsHeader(headerName))
continue;
Enumeration headers = servletRequest.getHeaders(headerName);
while (headers.hasMoreElements()) {//sometimes more than one value
String headerValue = (String) headers.nextElement();
// In case the proxy host is running multiple virtual servers,
// rewrite the Host header to ensure that we get content from
// the correct virtual server
if (headerName.equalsIgnoreCase(HttpHeaders.HOST)) {
HttpHost host = URIUtils.extractHost(this.targetUriObj);
headerValue = host.getHostName();
if (host.getPort() != -1)
headerValue += ":"+host.getPort();
}
proxyRequest.addHeader(headerName, headerValue);
}
}
}
private void setXForwardedForHeader(HttpServletRequest servletRequest,
HttpRequest proxyRequest) {
String headerName = "X-Forwarded-For";
if (doForwardIP) {
String newHeader = servletRequest.getRemoteAddr();
String existingHeader = servletRequest.getHeader(headerName);
if (existingHeader != null) {
newHeader = existingHeader + ", " + newHeader;
}
proxyRequest.setHeader(headerName, newHeader);
}
}
/** Copy proxied response headers back to the servlet client. */
protected void copyResponseHeaders(HttpResponse proxyResponse, HttpServletResponse servletResponse) {
for (Header header : proxyResponse.getAllHeaders()) {
if (hopByHopHeaders.containsHeader(header.getName()))
continue;
servletResponse.addHeader(header.getName(), header.getValue());
}
}
/** Copy response body data (the entity) from the proxy to the servlet client. */
protected void copyResponseEntity(HttpResponse proxyResponse, HttpServletResponse servletResponse) throws IOException {
HttpEntity entity = proxyResponse.getEntity();
if (entity != null) {
OutputStream servletOutputStream = servletResponse.getOutputStream();
entity.writeTo(servletOutputStream);
}
}
/** Reads the request URI from {@code servletRequest} and rewrites it, considering {@link
* #targetUriObj}. It's used to make the new request.
*/
protected String rewriteUrlFromRequest(HttpServletRequest servletRequest) {
StringBuilder uri = new StringBuilder(500);
uri.append(targetUri);
// Handle the path given to the servlet
//String path = servletRequest.getPathInfo();
String path = servletRequest.getRequestURI();
if (path != null) {//ex: /my/path.html
uri.append(encodeUriQuery(path));
}
// Handle the query string
String queryString = servletRequest.getQueryString();//ex:(following '?'): name=value&foo=bar#fragment
if (queryString != null && queryString.length() > 0) {
uri.append('?');
int fragIdx = queryString.indexOf('#');
String queryNoFrag = (fragIdx < 0 ? queryString : queryString.substring(0,fragIdx));
uri.append(encodeUriQuery(queryNoFrag));
if (doSendUrlFragment && fragIdx >= 0) {
uri.append('#');
uri.append(encodeUriQuery(queryString.substring(fragIdx + 1)));
}
}
return uri.toString();
}
/** For a redirect response from the target server, this translates {@code theUrl} to redirect to
* and translates it to one the original client can use. */
protected String rewriteUrlFromResponse(HttpServletRequest servletRequest, String theUrl) {
//TODO document example paths
if (theUrl.startsWith(targetUri)) {
String curUrl = servletRequest.getRequestURL().toString();//no query
String pathInfo = servletRequest.getPathInfo();
if (pathInfo != null) {
assert curUrl.endsWith(pathInfo);
curUrl = curUrl.substring(0,curUrl.length()-pathInfo.length());//take pathInfo off
}
theUrl = curUrl+theUrl.substring(targetUri.length());
}
return theUrl;
}
/** The target URI as configured. Not null. */
public String getTargetUri() { return targetUri; }
/**
* Encodes characters in the query or fragment part of the URI.
*
* <p>Unfortunately, an incoming URI sometimes has characters disallowed by the spec. HttpClient
* insists that the outgoing proxied request has a valid URI because it uses Java's {@link URI}.
* To be more forgiving, we must escape the problematic characters. See the URI class for the
* spec.
*
* @param in example: name=value&foo=bar#fragment
*/
protected static CharSequence encodeUriQuery(CharSequence in) {
//Note that I can't simply use URI.java to encode because it will escape pre-existing escaped things.
StringBuilder outBuf = null;
Formatter formatter = null;
for(int i = 0; i < in.length(); i++) {
char c = in.charAt(i);
boolean escape = true;
if (c < 128) {
if (asciiQueryChars.get((int)c)) {
escape = false;
}
} else if (!Character.isISOControl(c) && !Character.isSpaceChar(c)) {//not-ascii
escape = false;
}
if (!escape) {
if (outBuf != null)
outBuf.append(c);
} else {
//escape
if (outBuf == null) {
outBuf = new StringBuilder(in.length() + 5*3);
outBuf.append(in,0,i);
formatter = new Formatter(outBuf);
}
//leading %, 0 padded, width 2, capital hex
formatter.format("%%%02X",(int)c);//TODO
}
}
return outBuf != null ? outBuf : in;
}
protected static final BitSet asciiQueryChars;
static {
char[] c_unreserved = "_-!.~'()*".toCharArray();//plus alphanum
char[] c_punct = ",;:$&+=".toCharArray();
char[] c_reserved = "?/[]@".toCharArray();//plus punct
asciiQueryChars = new BitSet(128);
for(char c = 'a'; c <= 'z'; c++) asciiQueryChars.set((int)c);
for(char c = 'A'; c <= 'Z'; c++) asciiQueryChars.set((int)c);
for(char c = '0'; c <= '9'; c++) asciiQueryChars.set((int)c);
for(char c : c_unreserved) asciiQueryChars.set((int)c);
for(char c : c_punct) asciiQueryChars.set((int)c);
for(char c : c_reserved) asciiQueryChars.set((int)c);
asciiQueryChars.set((int)'%');//leave existing percent escapes in place
}
}