Java tutorial
/* * $HeadURL: http://juliusdavies.ca/svn/not-yet-commons-ssl/tags/commons-ssl-0.3.16/src/java/org/apache/commons/ssl/HostnameVerifier.java $ * $Revision: 121 $ * $Date: 2007-11-13 21:26:57 -0800 (Tue, 13 Nov 2007) $ * * ==================================================================== * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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. * ==================================================================== * * This software consists of voluntary contributions made by many * individuals on behalf of the Apache Software Foundation. For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. * */ package org.apache.commons.ssl; import javax.net.ssl.SSLException; import javax.net.ssl.SSLPeerUnverifiedException; import javax.net.ssl.SSLSession; import javax.net.ssl.SSLSocket; import java.io.IOException; import java.io.InputStream; import java.security.cert.Certificate; import java.security.cert.X509Certificate; import java.util.Arrays; import java.util.Iterator; import java.util.TreeSet; /** * Interface for checking if a hostname matches the names stored inside the * server's X.509 certificate. Correctly implements * javax.net.ssl.HostnameVerifier, but that interface is not recommended. * Instead we added several check() methods that take SSLSocket, * or X509Certificate, or ultimately (they all end up calling this one), * String. (It's easier to supply JUnit with Strings instead of mock * SSLSession objects!) * </p><p>Our check() methods throw exceptions if the name is * invalid, whereas javax.net.ssl.HostnameVerifier just returns true/false. * <p/> * We provide the HostnameVerifier.DEFAULT, HostnameVerifier.STRICT, and * HostnameVerifier.ALLOW_ALL implementations. We also provide the more * specialized HostnameVerifier.DEFAULT_AND_LOCALHOST, as well as * HostnameVerifier.STRICT_IE6. But feel free to define your own * implementations! * <p/> * Inspired by Sebastian Hauer's original StrictSSLProtocolSocketFactory in the * HttpClient "contrib" repository. * * @author Julius Davies * @author <a href="mailto:hauer@psicode.com">Sebastian Hauer</a> * @since 8-Dec-2006 */ public interface HostnameVerifier extends javax.net.ssl.HostnameVerifier { boolean verify(String host, SSLSession session); void check(String host, SSLSocket ssl) throws IOException; void check(String host, X509Certificate cert) throws SSLException; void check(String host, String[] cns, String[] subjectAlts) throws SSLException; void check(String[] hosts, SSLSocket ssl) throws IOException; void check(String[] hosts, X509Certificate cert) throws SSLException; /** * Checks to see if the supplied hostname matches any of the supplied CNs * or "DNS" Subject-Alts. Most implementations only look at the first CN, * and ignore any additional CNs. Most implementations do look at all of * the "DNS" Subject-Alts. The CNs or Subject-Alts may contain wildcards * according to RFC 2818. * * @param cns CN fields, in order, as extracted from the X.509 * certificate. * @param subjectAlts Subject-Alt fields of type 2 ("DNS"), as extracted * from the X.509 certificate. * @param hosts The array of hostnames to verify. * @throws javax.net.ssl.SSLException If verification failed. */ void check(String[] hosts, String[] cns, String[] subjectAlts) throws SSLException; /** * The DEFAULT HostnameVerifier works the same way as Curl and Firefox. * <p/> * The hostname must match either the first CN, or any of the subject-alts. * A wildcard can occur in the CN, and in any of the subject-alts. * <p/> * The only difference between DEFAULT and STRICT is that a wildcard (such * as "*.foo.com") with DEFAULT matches all subdomains, including * "a.b.foo.com". */ HostnameVerifier DEFAULT = new AbstractVerifier() { public final void check(final String[] hosts, final String[] cns, final String[] subjectAlts) throws SSLException { check(hosts, cns, subjectAlts, false, false); } public final String toString() { return "DEFAULT"; } }; /** * The DEFAULT_AND_LOCALHOST HostnameVerifier works like the DEFAULT * one with one additional relaxation: a host of "localhost", * "localhost.localdomain", "127.0.0.1", "::1" will always pass, no matter * what is in the server's certificate. */ HostnameVerifier DEFAULT_AND_LOCALHOST = new AbstractVerifier() { public final void check(final String[] hosts, final String[] cns, final String[] subjectAlts) throws SSLException { if (isLocalhost(hosts[0])) { return; } check(hosts, cns, subjectAlts, false, false); } public final String toString() { return "DEFAULT_AND_LOCALHOST"; } }; /** * The STRICT HostnameVerifier works the same way as java.net.URL in Sun * Java 1.4, Sun Java 5, Sun Java 6. It's also pretty close to IE6. * This implementation appears to be compliant with RFC 2818 for dealing * with wildcards. * <p/> * The hostname must match either the first CN, or any of the subject-alts. * A wildcard can occur in the CN, and in any of the subject-alts. The * one divergence from IE6 is how we only check the first CN. IE6 allows * a match against any of the CNs present. We decided to follow in * Sun Java 1.4's footsteps and only check the first CN. * <p/> * A wildcard such as "*.foo.com" matches only subdomains in the same * level, for example "a.foo.com". It does not match deeper subdomains * such as "a.b.foo.com". */ HostnameVerifier STRICT = new AbstractVerifier() { public final void check(final String[] host, final String[] cns, final String[] subjectAlts) throws SSLException { check(host, cns, subjectAlts, false, true); } public final String toString() { return "STRICT"; } }; /** * The STRICT_IE6 HostnameVerifier works just like the STRICT one with one * minor variation: the hostname can match against any of the CN's in the * server's certificate, not just the first one. This behaviour is * identical to IE6's behaviour. */ HostnameVerifier STRICT_IE6 = new AbstractVerifier() { public final void check(final String[] host, final String[] cns, final String[] subjectAlts) throws SSLException { check(host, cns, subjectAlts, true, true); } public final String toString() { return "STRICT_IE6"; } }; /** * The ALLOW_ALL HostnameVerifier essentially turns hostname verification * off. This implementation is a no-op, and never throws the SSLException. */ HostnameVerifier ALLOW_ALL = new AbstractVerifier() { public final void check(final String[] host, final String[] cns, final String[] subjectAlts) { // Allow everything - so never blowup. } public final String toString() { return "ALLOW_ALL"; } }; @SuppressWarnings("PMD.AvoidUsingHardCodedIP") abstract class AbstractVerifier implements HostnameVerifier { /** * This contains a list of 2nd-level domains that aren't allowed to * have wildcards when combined with country-codes. * For example: [*.co.uk]. * <p/> * The [*.co.uk] problem is an interesting one. Should we just hope * that CA's would never foolishly allow such a certificate to happen? * Looks like we're the only implementation guarding against this. * Firefox, Curl, Sun Java 1.4, 5, 6 don't bother with this check. */ private static final String[] BAD_COUNTRY_2LDS = { "ac", "co", "com", "ed", "edu", "go", "gouv", "gov", "info", "lg", "ne", "net", "or", "org" }; private static final String[] LOCALHOSTS = { "::1", "127.0.0.1", "localhost", "localhost.localdomain" }; static { // Just in case developer forgot to manually sort the array. :-) Arrays.sort(BAD_COUNTRY_2LDS); Arrays.sort(LOCALHOSTS); } protected AbstractVerifier() { } /** * The javax.net.ssl.HostnameVerifier contract. * * @param host 'hostname' we used to create our socket * @param session SSLSession with the remote server * @return true if the host matched the one in the certificate. */ public boolean verify(String host, SSLSession session) { try { Certificate[] certs = session.getPeerCertificates(); X509Certificate x509 = (X509Certificate) certs[0]; check(new String[] { host }, x509); return true; } catch (SSLException e) { return false; } } public void check(String host, SSLSocket ssl) throws IOException { check(new String[] { host }, ssl); } public void check(String host, X509Certificate cert) throws SSLException { check(new String[] { host }, cert); } public void check(String host, String[] cns, String[] subjectAlts) throws SSLException { check(new String[] { host }, cns, subjectAlts); } public void check(String[] host, SSLSocket ssl) throws IOException { if (host == null) { throw new NullPointerException("host to verify is null"); } SSLSession session = ssl.getSession(); if (session == null) { // In our experience this only happens under IBM 1.4.x when // spurious (unrelated) certificates show up in the server' // chain. Hopefully this will unearth the real problem: InputStream in = ssl.getInputStream(); in.available(); /* If you're looking at the 2 lines of code above because you're running into a problem, you probably have two options: #1. Clean up the certificate chain that your server is presenting (e.g. edit "/etc/apache2/server.crt" or wherever it is your server's certificate chain is defined). OR #2. Upgrade to an IBM 1.5.x or greater JVM, or switch to a non-IBM JVM. */ // If ssl.getInputStream().available() didn't cause an // exception, maybe at least now the session is available? session = ssl.getSession(); if (session == null) { // If it's still null, probably a startHandshake() will // unearth the real problem. ssl.startHandshake(); // Okay, if we still haven't managed to cause an exception, // might as well go for the NPE. Or maybe we're okay now? session = ssl.getSession(); } } Certificate[] certs; try { certs = session.getPeerCertificates(); } catch (SSLPeerUnverifiedException spue) { InputStream in = ssl.getInputStream(); in.available(); // Didn't trigger anything interesting? Okay, just throw // original. throw spue; } X509Certificate x509 = (X509Certificate) certs[0]; check(host, x509); } public void check(String[] host, X509Certificate cert) throws SSLException { String[] cns = Certificates.getCNs(cert); String[] subjectAlts = Certificates.getDNSSubjectAlts(cert); check(host, cns, subjectAlts); } public void check(final String[] hosts, final String[] cns, final String[] subjectAlts, final boolean ie6, final boolean strictWithSubDomains) throws SSLException { // Build up lists of allowed hosts For logging/debugging purposes. StringBuffer buf = new StringBuffer(32); buf.append('<'); for (int i = 0; i < hosts.length; i++) { String h = hosts[i]; h = h != null ? h.trim().toLowerCase() : ""; hosts[i] = h; if (i > 0) { buf.append('/'); } buf.append(h); } buf.append('>'); String hostnames = buf.toString(); // Build the list of names we're going to check. Our DEFAULT and // STRICT implementations of the HostnameVerifier only use the // first CN provided. All other CNs are ignored. // (Firefox, wget, curl, Sun Java 1.4, 5, 6 all work this way). TreeSet names = new TreeSet(); if (cns != null && cns.length > 0 && cns[0] != null) { names.add(cns[0]); if (ie6) { for (int i = 1; i < cns.length; i++) { names.add(cns[i]); } } } if (subjectAlts != null) { for (int i = 0; i < subjectAlts.length; i++) { if (subjectAlts[i] != null) { names.add(subjectAlts[i]); } } } if (names.isEmpty()) { String msg = "Certificate for " + hosts[0] + " doesn't contain CN or DNS subjectAlt"; throw new SSLException(msg); } // StringBuffer for building the error message. buf = new StringBuffer(); boolean match = false; out: for (Iterator it = names.iterator(); it.hasNext();) { // Don't trim the CN, though! String cn = (String) it.next(); cn = cn.toLowerCase(); // Store CN in StringBuffer in case we need to report an error. buf.append(" <"); buf.append(cn); buf.append('>'); if (it.hasNext()) { buf.append(" OR"); } // The CN better have at least two dots if it wants wildcard // action. It also can't be [*.co.uk] or [*.co.jp] or // [*.org.uk], etc... boolean doWildcard = cn.startsWith("*.") && cn.lastIndexOf('.') >= 0 && !isIP4Address(cn) && acceptableCountryWildcard(cn); for (int i = 0; i < hosts.length; i++) { final String hostName = hosts[i].trim().toLowerCase(); if (doWildcard) { match = hostName.endsWith(cn.substring(1)); if (match && strictWithSubDomains) { // If we're in strict mode, then [*.foo.com] is not // allowed to match [a.b.foo.com] match = countDots(hostName) == countDots(cn); } } else { match = hostName.equals(cn); } if (match) { break out; } } } if (!match) { throw new SSLException("hostname in certificate didn't match: " + hostnames + " !=" + buf); } } public static boolean isIP4Address(final String cn) { boolean isIP4 = true; String tld = cn; int x = cn.lastIndexOf('.'); // We only bother analyzing the characters after the final dot // in the name. if (x >= 0 && x + 1 < cn.length()) { tld = cn.substring(x + 1); } for (int i = 0; i < tld.length(); i++) { if (!Character.isDigit(tld.charAt(0))) { isIP4 = false; break; } } return isIP4; } public static boolean acceptableCountryWildcard(final String cn) { int cnLen = cn.length(); if (cnLen >= 7 && cnLen <= 9 && cn.charAt(cnLen - 3) == '.') { // Look for the '.' in the 3rd-last position: // Trim off the [*.] and the [.XX]. String s = cn.substring(2, cnLen - 3); // And test against the sorted array of bad 2lds: int x = Arrays.binarySearch(BAD_COUNTRY_2LDS, s); return x < 0; } return true; } public static boolean isLocalhost(String host) { host = host != null ? host.trim().toLowerCase() : ""; if (host.startsWith("::1")) { int x = host.lastIndexOf('%'); if (x >= 0) { host = host.substring(0, x); } } int x = Arrays.binarySearch(LOCALHOSTS, host); return x >= 0; } /** * Counts the number of dots "." in a string. * * @param s string to count dots from * @return number of dots */ public static int countDots(final String s) { int count = 0; for (int i = 0; i < s.length(); i++) { if (s.charAt(i) == '.') { count++; } } return count; } } }