Our check() methods throw exceptions if the name is + * invalid, whereas javax.net.ssl.HostnameVerifier just returns true/false. + *
+ * 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! + * + * Inspired by Sebastian Hauer's original StrictSSLProtocolSocketFactory in the + * HttpClient "contrib" repository. + * + * @author Julius Davies + * @author Sebastian Hauer + * @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 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. + * + * 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 only difference between DEFAULT and STRICT is that a wildcard (such + * as "*.foo.com") with DEFAULT matches all subdomains, including + * "a.b.foo.com". + */ + public final static 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. + */ + public final static 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. + * + * 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. + * + * 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". + */ + public final static 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. + */ + public final static 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. + */ + public final static 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"; } + }; + + 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]. + * + * 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 final static String[] BAD_COUNTRY_2LDS = + {"ac", "co", "com", "ed", "edu", "go", "gouv", "gov", "info", + "lg", "ne", "net", "or", "org"}; + + private final static 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 = getCNs(cert); + String[] subjectAlts = 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) { + // Look for the '.' in the 3rd-last position: + if (cn.charAt(cnLen - 3) == '.') { + // 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; + } + } + + //from Certificate + public static String getCN(X509Certificate cert) { + String[] cns = getCNs(cert); + boolean foundSomeCNs = cns != null && cns.length >= 1; + return foundSomeCNs ? cns[0] : null; + } + + public static String[] getCNs(X509Certificate cert) { + try { + final String subjectPrincipal = cert.getSubjectX500Principal().getName(X500Principal.RFC2253); + final LinkedList