com.github.markusbernhardt.proxy.search.wpad.WpadProxySearchStrategy Maven / Gradle / Ivy
package com.github.markusbernhardt.proxy.search.wpad;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.Proxy;
import java.net.ProxySelector;
import java.net.SocketException;
import java.net.URL;
import java.net.UnknownHostException;
import java.util.Enumeration;
import java.util.Properties;
import java.util.Random;
import com.github.markusbernhardt.proxy.ProxySearchStrategy;
import com.github.markusbernhardt.proxy.search.wpad.dhcp.DHCPMessage;
import com.github.markusbernhardt.proxy.search.wpad.dhcp.DHCPOptions;
import com.github.markusbernhardt.proxy.search.wpad.dhcp.DHCPSocket;
import com.github.markusbernhardt.proxy.util.Logger;
import com.github.markusbernhardt.proxy.util.Logger.LogLevel;
import com.github.markusbernhardt.proxy.util.ProxyException;
import com.github.markusbernhardt.proxy.util.ProxyUtil;
/*****************************************************************************
* Uses automatic proxy script search (WPAD) to find an PAC file automatically.
*
* Note: at the moment only the DNS name guessing schema is implemented. All
* others are missing.
*
*
* For more information about WPAD:
*
* Web_Proxy_Autodiscovery_Protocol
*
*
* Outdated RFC draft:
* draft-ietf-wrec-wpad-01.txt
*
*
* @author Markus Bernhardt, Copyright 2016
* @author Bernd Rosstauscher, Copyright 2009
****************************************************************************/
public class WpadProxySearchStrategy implements ProxySearchStrategy {
/*************************************************************************
* Constructor
************************************************************************/
public WpadProxySearchStrategy() {
super();
}
/*************************************************************************
* Loads the proxy settings from a PAC file. The location of the PAC file is
* determined automatically.
*
* @return a configured ProxySelector, null if none is found.
* @throws ProxyException
* on error.
************************************************************************/
@Override
public ProxySelector getProxySelector() throws ProxyException {
try {
Logger.log(getClass(), LogLevel.TRACE, "Using WPAD to find a proxy");
String pacScriptUrl = detectScriptUrlPerDHCP();
if (pacScriptUrl == null) {
pacScriptUrl = detectScriptUrlPerDNS();
}
if (pacScriptUrl == null) {
return null;
}
Logger.log(getClass(), LogLevel.TRACE, "PAC script url found: {}", pacScriptUrl);
return ProxyUtil.buildPacSelectorForUrl(pacScriptUrl);
} catch (IOException e) {
Logger.log(getClass(), LogLevel.ERROR, "Error during WPAD search.", e);
throw new ProxyException(e);
}
}
/*************************************************************************
* Gets the printable name of the search strategy.
*
* @return the printable name of the search strategy
************************************************************************/
@Override
public String getName() {
return "wpad";
}
/*************************************************************************
* Loads the settings and stores them in a properties map.
*
* @return the settings.
************************************************************************/
public Properties readSettings() {
try {
String pacScriptUrl = detectScriptUrlPerDHCP();
if (pacScriptUrl == null) {
pacScriptUrl = detectScriptUrlPerDNS();
}
if (pacScriptUrl == null) {
return null;
}
Properties result = new Properties();
result.setProperty("url", pacScriptUrl);
return result;
} catch (IOException e) {
// Ignore and return empty properties.
return new Properties();
}
}
/*************************************************************************
* Uses DNS to find the script URL. Attention: this detection method is known
* to have some severe security issues.
*
* @return the URL, null if not found.
************************************************************************/
private String detectScriptUrlPerDNS() throws IOException {
String fqdn = InetAddress.getLocalHost().getCanonicalHostName();
if (fqdn.equalsIgnoreCase("localhost") || fqdn.length() == 0 || Character.isDigit(fqdn.charAt(0))) {
return null;
}
Logger.log(getClass(), LogLevel.TRACE, "Searching per DNS guessing.");
String[] fqdnParts = fqdn.split("\\.");
for (int i = 0; i < fqdnParts.length; i++) {
// Skip "wpad." (for instance "wpad.com"), as this is useless and unsafe
if (i == fqdnParts.length - 2) {
continue;
}
// Build URL
StringBuilder stringBuilder = new StringBuilder("http://wpad");
for (int j = i + 1; j < fqdnParts.length; j++) {
stringBuilder.append('.');
stringBuilder.append(fqdnParts[j]);
}
stringBuilder.append("/wpad.dat");
// Try to connect to URL
try {
URL lookupURL = new URL(stringBuilder.toString());
Logger.log(getClass(), LogLevel.TRACE, "Trying url: {}", lookupURL);
HttpURLConnection con = (HttpURLConnection) lookupURL.openConnection(Proxy.NO_PROXY);
con.setInstanceFollowRedirects(true);
con.setRequestProperty("accept", "application/x-ns-proxy-autoconfig");
if (con.getResponseCode() == 200) {
return lookupURL.toString();
}
con.disconnect();
} catch (UnknownHostException e) {
Logger.log(getClass(), LogLevel.DEBUG, "Not available!");
// Not a real error, try next address
}
}
return null;
}
/*************************************************************************
* Uses DHCP to find the script URL.
*
* @return the URL, null if not found.
* @throws IOException
************************************************************************/
private String detectScriptUrlPerDHCP() throws IOException {
Logger.log(getClass(), LogLevel.TRACE, "Searching per DHCP.");
String url = null;
try {
Enumeration interfaces = NetworkInterface.getNetworkInterfaces();
while (interfaces.hasMoreElements()) {
NetworkInterface network = interfaces.nextElement();
if (!network.getName().equals("lo")) {
byte[] mac = network.getHardwareAddress();
Enumeration ips = network.getInetAddresses();
while (ips.hasMoreElements()) {
InetAddress ip = ips.nextElement();
// If ip is an IPv4 address
if (ip.getAddress().length == 4)
url = checkDhcpAckForPAC(ip, mac);
if (url != null)
return url;
}
}
}
} catch (SocketException e) {
e.printStackTrace();
}
return url;
}
private String getMacString(byte[] mac) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < 6; i++)
sb.append(String.format("%02X%s", mac[i], (i < 6 - 1) ? ":" : ""));
return sb.toString();
}
private String checkDhcpAckForPAC(InetAddress ip, byte[] mac) throws IOException {
try (DHCPSocket bindSocket = new DHCPSocket(DHCPMessage.CLIENT_PORT, ip)) {
DHCPMessage messageOut = new DHCPMessage(DHCPMessage.SERVER_PORT);
DHCPMessage messageIn = new DHCPMessage(DHCPMessage.CLIENT_PORT);
// from DHCPINFORM Message Clarifications
// https://tools.ietf.org/html/draft-ietf-dhc-dhcpinform-clarify-06
// Clients are still required to fulfill the DHCPv4 requirements for
// DHCPINFORM messages ([RFC2131], Sections 4.4.1 and 4.4.3). But
// the following are clarified as in addition, or to overlay those
// requirements:
messageOut.setOp((byte) 1); // setup message to send a DCHPREQUEST
// Clients MUST set 'ciaddr' to a working IPv4 address which they
// can use to receive replies. This address SHOULD be an address
// that is currently assigned to the interface upon which the client
// is transmitting its DHCPINFORM, except in the condition where the
// DHCP client is unable to determine a valid IP address for its
// host, in which case the client MUST set 'ciaddr' to all-zero.
messageOut.setCiaddr(ip.getAddress());
// Clients MUST set 'chaddr', 'htype', and 'hlen' to the hardware
// address of the interface upon which the DHCPINFORM message is
// being transmitted, except in the condition where the DHCP client
// is unable to determine this address, in which case all three
// fields MUST be set all-zero.
byte[] addr = new byte[16];
if (mac != null)
for (int i = 0; i < 6; i++)
addr[i] = mac[i];
// Despite what the spec says above if these are set to 0 you may
// not get a response from some dhcp servers
messageOut.setHtype((byte) 1); // 1 for Ethernet
messageOut.setHlen((byte) 6); // 6 for IEEE 802 MAC addresses
messageOut.setChaddr(addr);
// Clients MUST set the 'flags' field to zero. This means that the
// client MUST NOT set the 'BROADCAST' flag, and MUST be capable of
// receiving IP unicasts.
messageOut.setFlags((short) 0);
messageOut.setHops((byte) 0);
messageOut.setXid(new Random().nextInt());
messageOut.setSecs((short) 0);
messageOut.setYiaddr(InetAddress.getByName("0.0.0.0").getAddress());
messageOut.setSiaddr(InetAddress.getByName("0.0.0.0").getAddress());
messageOut.setGiaddr(InetAddress.getByName("0.0.0.0").getAddress());
// From RFC 2131 Section 4.4 Table 5
// https://tools.ietf.org/html/rfc2131#section-4.4
// Looks like the only option we need to set for a DHCPINFORM
// message is the DHCP message type
messageOut.setOption(DHCPOptions.OPTION_DHCP_MESSAGE_TYPE, new byte[] { DHCPMessage.DHCPINFORM });
Logger.log(getClass(), LogLevel.TRACE, "Trying DHCPInform on " + ip.getHostAddress() + (mac != null ? (" @ " + getMacString(mac)) : ""));
bindSocket.send(messageOut);
boolean sentinal = true;
while (sentinal) {
if (bindSocket.receive(messageIn)) {
if (messageOut.getXid() == messageIn.getXid()) {
byte[] pacFileLocationRaw = messageIn.getOption(DHCPOptions.OPTION_PROXY_AUTODISCOVERY);
String pacFileLocation = null;
if (pacFileLocationRaw != null)
pacFileLocation = new String(pacFileLocationRaw);
return pacFileLocation;
} else {
bindSocket.send(messageOut);
}
} else {
Logger.log(getClass(), LogLevel.DEBUG, "Timed out.");
sentinal = false;
}
}
}
return null;
}
}