1 /* 2 * Copyright (c) 2002, 2011, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package com.sun.jndi.ldap; 27 28 import java.util.Arrays; 29 import java.util.Hashtable; 30 import java.util.Random; 31 import java.util.StringTokenizer; 32 import java.util.List; 33 34 import javax.naming.*; 35 import javax.naming.directory.*; 36 import javax.naming.spi.NamingManager; 37 import javax.naming.ldap.LdapName; 38 import javax.naming.ldap.Rdn; 39 40 /** 41 * This class discovers the location of LDAP services by querying DNS. 42 * See http://www.ietf.org/internet-drafts/draft-ietf-ldapext-locate-07.txt 43 */ 44 45 class ServiceLocator { 46 47 private static final String SRV_RR = "SRV"; 48 49 private static final String[] SRV_RR_ATTR = new String[]{SRV_RR}; 50 51 private static final Random random = new Random(); 52 53 private ServiceLocator() { 54 } 55 56 /** 57 * Maps a distinguished name (RFC 2253) to a fully qualified domain name. 58 * Processes a sequence of RDNs having a DC attribute. 59 * The special RDN "DC=." denotes the root of the domain tree. 60 * Multi-valued RDNs, non-DC attributes, binary-valued attributes and the 61 * RDN "DC=." all reset the domain name and processing continues. 62 * 63 * @param dn A string distinguished name (RFC 2253). 64 * @return A domain name or null if none can be derived. 65 * @throws InvalidNameException If the distinguished name is invalid. 66 */ 67 static String mapDnToDomainName(String dn) throws InvalidNameException { 68 if (dn == null) { 69 return null; 70 } 71 StringBuilder domain = new StringBuilder(); 72 LdapName ldapName = new LdapName(dn); 73 74 // process RDNs left-to-right 75 //List<Rdn> rdnList = ldapName.getRdns(); 76 77 List<Rdn> rdnList = ldapName.getRdns(); 78 for (int i = rdnList.size() - 1; i >= 0; i--) { 79 //Rdn rdn = rdnList.get(i); 80 Rdn rdn = rdnList.get(i); 81 82 // single-valued RDN with a DC attribute 83 if ((rdn.size() == 1) && 84 ("dc".equalsIgnoreCase(rdn.getType()) )) { 85 Object attrval = rdn.getValue(); 86 if (attrval instanceof String) { 87 if (attrval.equals(".") || 88 (domain.length() == 1 && domain.charAt(0) == '.')) { 89 domain.setLength(0); // reset (when current or previous 90 // RDN value is "DC=.") 91 } 92 if (domain.length() > 0) { 93 domain.append('.'); 94 } 95 domain.append(attrval); 96 } else { 97 domain.setLength(0); // reset (when binary-valued attribute) 98 } 99 } else { 100 domain.setLength(0); // reset (when multi-valued RDN or non-DC) 101 } 102 } 103 return (domain.length() != 0) ? domain.toString() : null; 104 } 105 106 /** 107 * Locates the LDAP service for a given domain. 108 * Queries DNS for a list of LDAP Service Location Records (SRV) for a 109 * given domain name. 110 * 111 * @param domainName A string domain name. 112 * @param environment The possibly null environment of the context. 113 * @return An ordered list of hostports for the LDAP service or null if 114 * the service has not been located. 115 */ 116 static String[] getLdapService(String domainName, Hashtable<?,?> environment) { 117 118 if (domainName == null || domainName.length() == 0) { 119 return null; 120 } 121 122 String dnsUrl = "dns:///_ldap._tcp." + domainName; 123 String[] hostports = null; 124 125 try { 126 // Create the DNS context using NamingManager rather than using 127 // the initial context constructor. This avoids having the initial 128 // context constructor call itself (when processing the URL 129 // argument in the getAttributes call). 130 Context ctx = NamingManager.getURLContext("dns", environment); 131 if (!(ctx instanceof DirContext)) { 132 return null; // cannot create a DNS context 133 } 134 Attributes attrs = 135 ((DirContext)ctx).getAttributes(dnsUrl, SRV_RR_ATTR); 136 Attribute attr; 137 138 if (attrs != null && ((attr = attrs.get(SRV_RR)) != null)) { 139 int numValues = attr.size(); 140 int numRecords = 0; 141 SrvRecord[] srvRecords = new SrvRecord[numValues]; 142 143 // create the service records 144 int i = 0; 145 int j = 0; 146 while (i < numValues) { 147 try { 148 srvRecords[j] = new SrvRecord((String) attr.get(i)); 149 j++; 150 } catch (Exception e) { 151 // ignore bad value 152 } 153 i++; 154 } 155 numRecords = j; 156 157 // trim 158 if (numRecords < numValues) { 159 SrvRecord[] trimmed = new SrvRecord[numRecords]; 160 System.arraycopy(srvRecords, 0, trimmed, 0, numRecords); 161 srvRecords = trimmed; 162 } 163 164 // Sort the service records in ascending order of their 165 // priority value. For records with equal priority, move 166 // those with weight 0 to the top of the list. 167 if (numRecords > 1) { 168 Arrays.sort(srvRecords); 169 } 170 171 // extract the host and port number from each service record 172 hostports = extractHostports(srvRecords); 173 } 174 } catch (NamingException e) { 175 // ignore 176 } 177 return hostports; 178 } 179 180 /** 181 * Extract hosts and port numbers from a list of SRV records. 182 * An array of hostports is returned or null if none were found. 183 */ 184 private static String[] extractHostports(SrvRecord[] srvRecords) { 185 String[] hostports = null; 186 187 int head = 0; 188 int tail = 0; 189 int sublistLength = 0; 190 int k = 0; 191 for (int i = 0; i < srvRecords.length; i++) { 192 if (hostports == null) { 193 hostports = new String[srvRecords.length]; 194 } 195 // find the head and tail of the list of records having the same 196 // priority value. 197 head = i; 198 while (i < srvRecords.length - 1 && 199 srvRecords[i].priority == srvRecords[i + 1].priority) { 200 i++; 201 } 202 tail = i; 203 204 // select hostports from the sublist 205 sublistLength = (tail - head) + 1; 206 for (int j = 0; j < sublistLength; j++) { 207 hostports[k++] = selectHostport(srvRecords, head, tail); 208 } 209 } 210 return hostports; 211 } 212 213 /* 214 * Randomly select a service record in the range [head, tail] and return 215 * its hostport value. Follows the algorithm in RFC 2782. 216 */ 217 private static String selectHostport(SrvRecord[] srvRecords, int head, 218 int tail) { 219 if (head == tail) { 220 return srvRecords[head].hostport; 221 } 222 223 // compute the running sum for records between head and tail 224 int sum = 0; 225 for (int i = head; i <= tail; i++) { 226 if (srvRecords[i] != null) { 227 sum += srvRecords[i].weight; 228 srvRecords[i].sum = sum; 229 } 230 } 231 String hostport = null; 232 233 // If all records have zero weight, select first available one; 234 // otherwise, randomly select a record according to its weight 235 int target = (sum == 0 ? 0 : random.nextInt(sum + 1)); 236 for (int i = head; i <= tail; i++) { 237 if (srvRecords[i] != null && srvRecords[i].sum >= target) { 238 hostport = srvRecords[i].hostport; 239 srvRecords[i] = null; // make this record unavailable 240 break; 241 } 242 } 243 return hostport; 244 } 245 246 /** 247 * This class holds a DNS service (SRV) record. 248 * See http://www.ietf.org/rfc/rfc2782.txt 249 */ 250 251 static class SrvRecord implements Comparable<SrvRecord> { 252 253 int priority; 254 int weight; 255 int sum; 256 String hostport; 257 258 /** 259 * Creates a service record object from a string record. 260 * DNS supplies the string record in the following format: 261 * <pre> 262 * <Priority> " " <Weight> " " <Port> " " <Host> 263 * </pre> 264 */ 265 SrvRecord(String srvRecord) throws Exception { 266 StringTokenizer tokenizer = new StringTokenizer(srvRecord, " "); 267 String port; 268 269 if (tokenizer.countTokens() == 4) { 270 priority = Integer.parseInt(tokenizer.nextToken()); 271 weight = Integer.parseInt(tokenizer.nextToken()); 272 port = tokenizer.nextToken(); 273 hostport = tokenizer.nextToken() + ":" + port; 274 } else { 275 throw new IllegalArgumentException(); 276 } 277 } 278 279 /* 280 * Sort records in ascending order of priority value. For records with 281 * equal priority move those with weight 0 to the top of the list. 282 */ 283 public int compareTo(SrvRecord that) { 284 if (priority > that.priority) { 285 return 1; // this > that 286 } else if (priority < that.priority) { 287 return -1; // this < that 288 } else if (weight == 0 && that.weight != 0) { 289 return -1; // this < that 290 } else if (weight != 0 && that.weight == 0) { 291 return 1; // this > that 292 } else { 293 return 0; // this == that 294 } 295 } 296 } 297 }