package ldaptest;
import java.util.Hashtable;
import javax.naming.Context;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.DirContext;
import javax.naming.directory.SearchControls;
import javax.naming.directory.SearchResult;
import javax.naming.ldap.InitialLdapContext;
import javax.naming.ldap.LdapContext;

/**
 * Example code for retrieving a Users Primary Group
 * from Microsoft Active Directory via. its LDAP API
  */
public class LDAPTest {

    public static void main(String[] args) throws NamingException {

        final String ldapAdServer = "ldap://company.com:3269";
        final String ldapSearchBase = "dc=company,dc=com";

        final String ldapUsername = "ldapUsername";
        final String ldapPassword = "ldapPassword";

        final String ldapAccountToLookup = "ldapAccountToLookup";


        Hashtable<String, Object> env = new Hashtable<String, Object>();
        env.put(Context.SECURITY_AUTHENTICATION, "simple");
        if(ldapUsername != null) {
            env.put(Context.SECURITY_PRINCIPAL, ldapUsername);
        }
        if(ldapPassword != null) {
            env.put(Context.SECURITY_CREDENTIALS, ldapPassword);
        }
        env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
        env.put(Context.PROVIDER_URL, ldapAdServer);

        //ensures that objectSID attribute values
        //will be returned as a byte[] instead of a String
        env.put("java.naming.ldap.attributes.binary", "objectSID");

        // the following is helpful in debugging errors
        //env.put("com.sun.jndi.ldap.trace.ber", System.err);
        LdapContext ctx = new InitialLdapContext();

        LDAPTest ldap = new LDAPTest();
        System.out.println("Before searchresult");
        //1) lookup the ldap account
        SearchResult srLdapUser = ldap.findAccountByAccountName(ctx, ldapSearchBase, ldapAccountToLookup);
        System.out.println("before SID");
        //2) get the SID of the users primary group
        String primaryGroupSID = ldap.getPrimaryGroupSID(srLdapUser);

        //3) get the users Primary Group
        String primaryGroupName = ldap.findGroupBySID(ctx, ldapSearchBase, primaryGroupSID);
    }

    public SearchResult findAccountByAccountName(DirContext ctx, String ldapSearchBase, String accountName) throws NamingException {

        String searchFilter = "(&(objectClass=user)(sAMAccountName=" + accountName + "))";
        System.out.println(searchFilter);
        SearchControls searchControls = new SearchControls();
        searchControls.setSearchScope(SearchControls.SUBTREE_SCOPE);
        System.out.println("before Results");
        NamingEnumeration<SearchResult> results = ctx.search(ldapSearchBase, searchFilter, searchControls);
        System.out.println("after Results");
        SearchResult searchResult = null;
        if(results.hasMoreElements()) {
             searchResult = (SearchResult) results.nextElement();

            //make sure there is not another item available, there should be only 1 match
            if(results.hasMoreElements()) {
                System.err.println("Matched multiple users for the accountName: " + accountName);
                return null;
            }
        }

        return searchResult;
    }

    public String findGroupBySID(DirContext ctx, String ldapSearchBase, String sid) throws NamingException {

        String searchFilter = "(&(objectClass=group)(objectSid=" + sid + "))";

        SearchControls searchControls = new SearchControls();
        searchControls.setSearchScope(SearchControls.SUBTREE_SCOPE);

        NamingEnumeration<SearchResult> results = ctx.search(ldapSearchBase, searchFilter, searchControls);

        if(results.hasMoreElements()) {
            SearchResult searchResult = (SearchResult) results.nextElement();

            //make sure there is not another item available, there should be only 1 match
            if(results.hasMoreElements()) {
                System.err.println("Matched multiple groups for the group with SID: " + sid);
                return null;
            } else {
                return (String)searchResult.getAttributes().get("sAMAccountName").get();
            }
        }
        return null;
    }

    public String getPrimaryGroupSID(SearchResult srLdapUser) throws NamingException {
        byte[] objectSID = (byte[])srLdapUser.getAttributes().get("objectSid").get();
        String strPrimaryGroupID = (String)srLdapUser.getAttributes().get("primaryGroupID").get();

        String strObjectSid = decodeSID(objectSID);

        return strObjectSid.substring(0, strObjectSid.lastIndexOf('-') + 1) + strPrimaryGroupID;
    }

    /**
     * The binary data is in the form:
     * byte[0] - revision level
     * byte[1] - count of sub-authorities
     * byte[2-7] - 48 bit authority (big-endian)
     * and then count x 32 bit sub authorities (little-endian)
     *
     * The String value is: S-Revision-Authority-SubAuthority[n]...
     *
     * Based on code from here - http://forums.oracle.com/forums/thread.jspa?threadID=1155740&tstart=0
     */
    public static String decodeSID(byte[] sid) {

        final StringBuilder strSid = new StringBuilder("S-");

        // get version
        final int revision = sid[0];
        strSid.append(Integer.toString(revision));

        //next byte is the count of sub-authorities
        final int countSubAuths = sid[1] & 0xFF;

        //get the authority
        long authority = 0;
        //String rid = "";
        for(int i = 2; i <= 7; i++) {
           authority |= ((long)sid[i]) << (8 * (5 - (i - 2)));
        }
        strSid.append("-");
        strSid.append(Long.toHexString(authority));

        //iterate all the sub-auths
        int offset = 8;
        int size = 4; //4 bytes for each sub auth
        for(int j = 0; j < countSubAuths; j++) {
            long subAuthority = 0;
            for(int k = 0; k < size; k++) {
                subAuthority |= (long)(sid[offset + k] & 0xFF) << (8 * k);
            }

            strSid.append("-");
            strSid.append(subAuthority);

            offset += size;
        }

        return strSid.toString();
    }
}