DefaultHostnameVerifier.javaAPI DocAndroid 1.5 API13779Wed May 06 22:41:06 BST


public class DefaultHostnameVerifier extends Object implements HostnameVerifier
A HostnameVerifier that 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 BROWSER_COMPATIBLE and STRICT is that a wildcard (such as "*") with BROWSER_COMPATIBLE matches all subdomains, including "".

Julius Davies

Fields Summary
private static final String[]
This contains a list of 2nd-level domains that aren't allowed to have wildcards when combined with country-codes. For example: [*].

The [*] 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.

Constructors Summary
public DefaultHostnameVerifier()

        // Just in case developer forgot to manually sort the array.  :-)
Methods Summary
public static booleanacceptableCountryWildcard(java.lang.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 intcountDots(java.lang.String s)
Counts the number of dots "." in a string.

s string to count dots from
number of dots

        int count = 0;
        for(int i = 0; i < s.length(); i++) {
            if(s.charAt(i) == '.") {
        return count;
public static java.lang.String[]getCNs( cert)

        LinkedList<String> cnList = new LinkedList<String>();
          Sebastian Hauer's original StrictSSLProtocolSocketFactory used
          getName() and had the following comment:

              Parses a X.500 distinguished name for the value of the
              "Common Name" field.  This is done a bit sloppy right
              now and should probably be done a bit more according to
              <code>RFC 2253</code>.

          I've noticed that toString() seems to do a better job than
          getName() on these X500Principal objects, so I'm hoping that
          addresses Sebastian's concern.

          For example, getName() gives me this:

          whereas toString() gives me this:

          Looks like toString() even works with non-ascii domain names!
          I tested it with "花子" and it worked fine.
        String subjectPrincipal = cert.getSubjectX500Principal().toString();
        StringTokenizer st = new StringTokenizer(subjectPrincipal, ",");
        while(st.hasMoreTokens()) {
            String tok = st.nextToken();
            int x = tok.indexOf("CN=");
            if(x >= 0) {
                cnList.add(tok.substring(x + 3));
        if(!cnList.isEmpty()) {
            String[] cns = new String[cnList.size()];
            return cns;
        } else {
            return null;
public static java.lang.String[]getDNSSubjectAlts( cert)
Extracts the array of SubjectAlt DNS names from an X509Certificate. Returns null if there aren't any.

Note: Java doesn't appear able to extract international characters from the SubjectAlts. It can only extract international characters from the CN field.

(Or maybe the version of OpenSSL I'm using to test isn't storing the international characters correctly in the SubjectAlts?).

cert X509Certificate
Array of SubjectALT DNS names stored in the certificate.

        LinkedList<String> subjectAltList = new LinkedList<String>();
        Collection<List<?>> c = null;
        try {
            c = cert.getSubjectAlternativeNames();
        catch(CertificateParsingException cpe) {
                    .log(Level.FINE, "Error parsing certificate.", cpe);
        if(c != null) {
            for (List<?> aC : c) {
                List<?> list = aC;
                int type = ((Integer) list.get(0)).intValue();
                // If type is 2, then we've got a dNSName
                if (type == 2) {
                    String s = (String) list.get(1);
        if(!subjectAltList.isEmpty()) {
            String[] subjectAlts = new String[subjectAltList.size()];
            return subjectAlts;
        } else {
            return null;
public final voidverify(java.lang.String host, java.lang.String[] cns, java.lang.String[] subjectAlts)
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.

cns CN fields, in order, as extracted from the X.509 certificate.
subjectAlts Subject-Alt fields of type 2 ("DNS"), as extracted from the X.509 certificate.
host The hostname to verify.
SSLException If verification failed.

        verify(host, cns, subjectAlts, false);
public final voidverify(java.lang.String host, ssl)

        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();
              If you're looking at the 2 lines of code above because
              you're running into a problem, you probably have two

                #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).


                #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.

                // 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 = session.getPeerCertificates();
        X509Certificate x509 = (X509Certificate) certs[0];
        verify(host, x509);
public final booleanverify(java.lang.String host, session)

        try {
            Certificate[] certs = session.getPeerCertificates();
            X509Certificate x509 = (X509Certificate) certs[0];
            verify(host, x509);
            return true;
        catch(SSLException e) {
            return false;
public final voidverify(java.lang.String host, cert)

        String[] cns = getCNs(cert);
        String[] subjectAlts = getDNSSubjectAlts(cert);
        verify(host, cns, subjectAlts);
public final voidverify(java.lang.String host, java.lang.String[] cns, java.lang.String[] subjectAlts, boolean strictWithSubDomains)

        // 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).
        LinkedList<String> names = new LinkedList<String>();
        if(cns != null && cns.length > 0 && cns[0] != null) {
        if(subjectAlts != null) {
            for (String subjectAlt : subjectAlts) {
                if (subjectAlt != null) {

        if(names.isEmpty()) {
            String msg = "Certificate for <" + host +
                         "> doesn't contain CN or DNS subjectAlt";
            throw new SSLException(msg);

        // StringBuffer for building the error message.
        StringBuffer buf = new StringBuffer();

        // We're can be case-insensitive when comparing the host we used to
        // establish the socket to the hostname in the certificate.
        String hostName = host.trim().toLowerCase(Locale.ENGLISH);
        boolean match = false;
        for(Iterator<String> it = names.iterator(); it.hasNext();) {
            // Don't trim the CN, though!
            String cn =;
            cn = cn.toLowerCase(Locale.ENGLISH);
            // Store CN in StringBuffer in case we need to report an error.
            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 [*] or [*] or
            // [*], etc...
            boolean doWildcard = cn.startsWith("*.") &&
                                 cn.lastIndexOf('.") >= 0 &&
                                 acceptableCountryWildcard(cn) &&

            if(doWildcard) {
                match = hostName.endsWith(cn.substring(1));
                if(match && strictWithSubDomains) {
                    // If we're in strict mode, then [*] is not
                    // allowed to match []
                    match = countDots(hostName) == countDots(cn);
            } else {
                match = hostName.equals(cn);
            if(match) {
        if(!match) {
            throw new SSLException("hostname in certificate didn't match: <" + 
                                   host + "> !=" + buf);