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package com.sun.jndi.ldap;

import java.util.*;

import javax.naming.*;
import javax.naming.directory.*;
import javax.naming.spi.NamingManager;
import javax.naming.ldap.LdapName;
import javax.naming.ldap.Rdn;

This class discovers the location of LDAP services by querying DNS. See http://www.ietf.org/internet-drafts/draft-ietf-ldapext-locate-07.txt
/** * This class discovers the location of LDAP services by querying DNS. * See http://www.ietf.org/internet-drafts/draft-ietf-ldapext-locate-07.txt */
class ServiceLocator { private static final String SRV_RR = "SRV"; private static final String[] SRV_RR_ATTR = new String[]{SRV_RR}; private static final Random random = new Random(); private ServiceLocator() { }
Maps a distinguished name (RFC 2253) to a fully qualified domain name. Processes a sequence of RDNs having a DC attribute. The special RDN "DC=." denotes the root of the domain tree. Multi-valued RDNs, non-DC attributes, binary-valued attributes and the RDN "DC=." all reset the domain name and processing continues.
Params:
  • dn – A string distinguished name (RFC 2253).
Returns:A domain name or null if none can be derived.
@throwInvalidNameException If the distinugished name is invalid.
/** * Maps a distinguished name (RFC 2253) to a fully qualified domain name. * Processes a sequence of RDNs having a DC attribute. * The special RDN "DC=." denotes the root of the domain tree. * Multi-valued RDNs, non-DC attributes, binary-valued attributes and the * RDN "DC=." all reset the domain name and processing continues. * * @param dn A string distinguished name (RFC 2253). * @return A domain name or null if none can be derived. * @throw InvalidNameException If the distinugished name is invalid. */
static String mapDnToDomainName(String dn) throws InvalidNameException { if (dn == null) { return null; } StringBuffer domain = new StringBuffer(); LdapName ldapName = new LdapName(dn); // process RDNs left-to-right //List<Rdn> rdnList = ldapName.getRdns(); List<Rdn> rdnList = ldapName.getRdns(); for (int i = rdnList.size() - 1; i >= 0; i--) { //Rdn rdn = rdnList.get(i); Rdn rdn = rdnList.get(i); // single-valued RDN with a DC attribute if ((rdn.size() == 1) && ("dc".equalsIgnoreCase(rdn.getType()) )) { Object attrval = rdn.getValue(); if (attrval instanceof String) { if (attrval.equals(".") || (domain.length() == 1 && domain.charAt(0) == '.')) { domain.setLength(0); // reset (when current or previous // RDN value is "DC=.") } if (domain.length() > 0) { domain.append('.'); } domain.append(attrval); } else { domain.setLength(0); // reset (when binary-valued attribute) } } else { domain.setLength(0); // reset (when multi-valued RDN or non-DC) } } return (domain.length() != 0) ? domain.toString() : null; }
Locates the LDAP service for a given domain. Queries DNS for a list of LDAP Service Location Records (SRV) for a given domain name.
Params:
  • domainName – A string domain name.
  • environment – The possibly null environment of the context.
Returns:An ordered list of hostports for the LDAP service or null if the service has not been located.
/** * Locates the LDAP service for a given domain. * Queries DNS for a list of LDAP Service Location Records (SRV) for a * given domain name. * * @param domainName A string domain name. * @param environment The possibly null environment of the context. * @return An ordered list of hostports for the LDAP service or null if * the service has not been located. */
static String[] getLdapService(String domainName, Map<?,?> environment) { if (environment instanceof Hashtable) { return getLdapService(domainName, (Hashtable)environment); } return getLdapService(domainName, new Hashtable<>(environment)); }
Locates the LDAP service for a given domain. Queries DNS for a list of LDAP Service Location Records (SRV) for a given domain name.
Params:
  • domainName – A string domain name.
  • environment – The possibly null environment of the context.
Returns:An ordered list of hostports for the LDAP service or null if the service has not been located.
/** * Locates the LDAP service for a given domain. * Queries DNS for a list of LDAP Service Location Records (SRV) for a * given domain name. * * @param domainName A string domain name. * @param environment The possibly null environment of the context. * @return An ordered list of hostports for the LDAP service or null if * the service has not been located. */
static String[] getLdapService(String domainName, Hashtable<?,?> environment) { if (domainName == null || domainName.length() == 0) { return null; } String dnsUrl = "dns:///_ldap._tcp." + domainName; String[] hostports = null; try { // Create the DNS context using NamingManager rather than using // the initial context constructor. This avoids having the initial // context constructor call itself (when processing the URL // argument in the getAttributes call). Context ctx = NamingManager.getURLContext("dns", environment); if (!(ctx instanceof DirContext)) { return null; // cannot create a DNS context } Attributes attrs = ((DirContext)ctx).getAttributes(dnsUrl, SRV_RR_ATTR); Attribute attr; if (attrs != null && ((attr = attrs.get(SRV_RR)) != null)) { int numValues = attr.size(); int numRecords = 0; SrvRecord[] srvRecords = new SrvRecord[numValues]; // create the service records int i = 0; int j = 0; while (i < numValues) { try { srvRecords[j] = new SrvRecord((String) attr.get(i)); j++; } catch (Exception e) { // ignore bad value } i++; } numRecords = j; // trim if (numRecords < numValues) { SrvRecord[] trimmed = new SrvRecord[numRecords]; System.arraycopy(srvRecords, 0, trimmed, 0, numRecords); srvRecords = trimmed; } // Sort the service records in ascending order of their // priority value. For records with equal priority, move // those with weight 0 to the top of the list. if (numRecords > 1) { Arrays.sort(srvRecords); } // extract the host and port number from each service record hostports = extractHostports(srvRecords); } } catch (NamingException e) { // ignore } return hostports; }
Extract hosts and port numbers from a list of SRV records. An array of hostports is returned or null if none were found.
/** * Extract hosts and port numbers from a list of SRV records. * An array of hostports is returned or null if none were found. */
private static String[] extractHostports(SrvRecord[] srvRecords) { String[] hostports = null; int head = 0; int tail = 0; int sublistLength = 0; int k = 0; for (int i = 0; i < srvRecords.length; i++) { if (hostports == null) { hostports = new String[srvRecords.length]; } // find the head and tail of the list of records having the same // priority value. head = i; while (i < srvRecords.length - 1 && srvRecords[i].priority == srvRecords[i + 1].priority) { i++; } tail = i; // select hostports from the sublist sublistLength = (tail - head) + 1; for (int j = 0; j < sublistLength; j++) { hostports[k++] = selectHostport(srvRecords, head, tail); } } return hostports; } /* * Randomly select a service record in the range [head, tail] and return * its hostport value. Follows the algorithm in RFC 2782. */ private static String selectHostport(SrvRecord[] srvRecords, int head, int tail) { if (head == tail) { return srvRecords[head].hostport; } // compute the running sum for records between head and tail int sum = 0; for (int i = head; i <= tail; i++) { if (srvRecords[i] != null) { sum += srvRecords[i].weight; srvRecords[i].sum = sum; } } String hostport = null; // If all records have zero weight, select first available one; // otherwise, randomly select a record according to its weight int target = (sum == 0 ? 0 : random.nextInt(sum + 1)); for (int i = head; i <= tail; i++) { if (srvRecords[i] != null && srvRecords[i].sum >= target) { hostport = srvRecords[i].hostport; srvRecords[i] = null; // make this record unavailable break; } } return hostport; }
This class holds a DNS service (SRV) record. See http://www.ietf.org/rfc/rfc2782.txt
/** * This class holds a DNS service (SRV) record. * See http://www.ietf.org/rfc/rfc2782.txt */
static class SrvRecord implements Comparable<SrvRecord> { int priority; int weight; int sum; String hostport;
Creates a service record object from a string record. DNS supplies the string record in the following format:
     " "  " "  " " 
/** * Creates a service record object from a string record. * DNS supplies the string record in the following format: * <pre> * <Priority> " " <Weight> " " <Port> " " <Host> * </pre> */
SrvRecord(String srvRecord) throws Exception { StringTokenizer tokenizer = new StringTokenizer(srvRecord, " "); String port; if (tokenizer.countTokens() == 4) { priority = Integer.parseInt(tokenizer.nextToken()); weight = Integer.parseInt(tokenizer.nextToken()); port = tokenizer.nextToken(); hostport = tokenizer.nextToken() + ":" + port; } else { throw new IllegalArgumentException(); } } /* * Sort records in ascending order of priority value. For records with * equal priority move those with weight 0 to the top of the list. */ public int compareTo(SrvRecord that) { if (priority > that.priority) { return 1; // this > that } else if (priority < that.priority) { return -1; // this < that } else if (weight == 0 && that.weight != 0) { return -1; // this < that } else if (weight != 0 && that.weight == 0) { return 1; // this > that } else { return 0; // this == that } } } }