使用Java JNDI执行DNS“ ANY”查找

Question

I am using Java JNDI to perform DNS lookups using the following basic syntax as per the SSCCE below, but I am trying to query all records using the "ANY" attribute:

import java.util.*;
import javax.naming.*;
import javax.naming.directory.*;

public class SSCCE {
  public static void main(String[] args) {
    try {
      Properties p = new Properties();
      p.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.dns.DnsContextFactory");
      InitialDirContext idc = new InitialDirContext(p);

      Attributes attrs = idc.getAttributes("netnix.org", new String[] { "* *" });
      Attribute attr = attrs.get("* *");

      if (attr != null) {
        for (int i = 0; i < attr.size(); i++) {
          System.out.println("Found " + (String)attr.get(i));
        }
      }
      else {
        System.out.println("Found nothing");
      }
    }
    catch (Exception e) {
      e.printStackTrace();
    }
  }
}

My question is around being able to query a resource type of "ANY" which should return all the DNS resource records associated with a specific domain - example below using the "host" utility.

chrixm@puffy(:):~$ host -t ANY netnix.org
netnix.org has SPF record "v=spf1 include:_spf.google.com ~all"
netnix.org mail is handled by 10 aspmx2.googlemail.com.
netnix.org mail is handled by 5 alt1.aspmx.l.google.com.
netnix.org mail is handled by 1 aspmx.l.google.com.
netnix.org mail is handled by 5 alt2.aspmx.l.google.com.
netnix.org mail is handled by 10 aspmx3.googlemail.com.
netnix.org name server ns-1154.awsdns-16.org.
netnix.org name server ns-941.awsdns-53.net.
netnix.org name server ns-61.awsdns-07.com.
netnix.org name server ns-1880.awsdns-43.co.uk.

I have read http://docs.oracle.com/javase/7/docs/technotes/guides/jndi/jndi-dns.html , which says:

Superclass attribute identifiers are also defined. These may be useful when querying records using the DirContext.getAttributes() method. If an attribute name has "*" in place of a type name (or class name), it represents records of any type (or class). For example, the attribute identifier "IN *" may be passed to the getAttributes() method to find all internet class records. The attribute identifier "* *" represents records of any class or type.

However, Java JNDI doesn't understand a resource record of "*" or "* *" as the above code doesn't return any records (I am able to query "NS" or "SOA", etc individually) - has anyone had any experience of getting this working. I can of course query each individual resource type, but considering there is a valid record type of "ANY" as per RFC 1035 (Type ID 255) this seems very inefficient?

Answer 1

After examining the methods of the Attributes class I noticed a getAll() method. After further searching I was able to implement the following which now allows you to search using "*" as the record type and print all the records.

Attributes attrs = idc.getAttributes("netnix.org", new String[] { "*" });
NamingEnumeration<?> ae = attrs.getAll();

while (ae.hasMore()) {
  Attribute attr = (Attribute)ae.next();
  for (int i = 0; i < attr.size(); i++) {
    Object a = attr.get(i);
    if (a instanceof String) {
      System.out.println(attr.getID() + " " + a);
    }
    else {
      System.out.println(attr.getID() + " NOT ASCII");
    }
  }
}
ae.close();

Answer 2

You're inventing semantics here. There is no support anywhere in JNDI for "* *" as either an attribute set or an attribute name. The correct syntax for 'all attributes' as an attribute set to return is "*" , and the correct way to enumerate them all is via Attributes.getAll() .