1 /*
2 * Copyright (c) 2002, 2003, 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.Enumeration;
30 import java.util.Hashtable;
31 import java.util.NoSuchElementException;
32 import java.util.Random;
33 import java.util.StringTokenizer;
34 import java.util.List;
35
36 import javax.naming.*;
37 import javax.naming.directory.*;
38 import javax.naming.spi.NamingManager;
39 import javax.naming.ldap.LdapName;
40 import javax.naming.ldap.Rdn;
41
42 import com.sun.jndi.ldap.LdapURL;
43
44 /**
45 * This class discovers the location of LDAP services by querying DNS.
46 * See http://www.ietf.org/internet-drafts/draft-ietf-ldapext-locate-07.txt
47 */
48
49 class ServiceLocator {
50
51 private static final String SRV_RR = "SRV";
52
53 private static final String[] SRV_RR_ATTR = new String[]{SRV_RR};
54
55 private static final Random random = new Random();
56
57 private ServiceLocator() {
58 }
59
60 /**
61 * Maps a distinguished name (RFC 2253) to a fully qualified domain name.
62 * Processes a sequence of RDNs having a DC attribute.
63 * The special RDN "DC=." denotes the root of the domain tree.
64 * Multi-valued RDNs, non-DC attributes, binary-valued attributes and the
65 * RDN "DC=." all reset the domain name and processing continues.
66 *
67 * @param dn A string distinguished name (RFC 2253).
68 * @return A domain name or null if none can be derived.
69 * @throw InvalidNameException If the distinugished name is invalid.
70 */
71 static String mapDnToDomainName(String dn) throws InvalidNameException {
72 if (dn == null) {
73 return null;
74 }
75 StringBuffer domain = new StringBuffer();
76 LdapName ldapName = new LdapName(dn);
77
78 // process RDNs left-to-right
79 //List<Rdn> rdnList = ldapName.getRdns();
80
81 List rdnList = ldapName.getRdns();
82 for (int i = rdnList.size() - 1; i >= 0; i--) {
83 //Rdn rdn = rdnList.get(i);
84 Rdn rdn = (Rdn) rdnList.get(i);
85
86 // single-valued RDN with a DC attribute
87 if ((rdn.size() == 1) &&
88 ("dc".equalsIgnoreCase(rdn.getType()) )) {
89 Object attrval = rdn.getValue();
90 if (attrval instanceof String) {
91 if (attrval.equals(".") ||
92 (domain.length() == 1 && domain.charAt(0) == '.')) {
93 domain.setLength(0); // reset (when current or previous
94 // RDN value is "DC=.")
95 }
96 if (domain.length() > 0) {
97 domain.append('.');
98 }
99 domain.append(attrval);
100 } else {
101 domain.setLength(0); // reset (when binary-valued attribute)
102 }
103 } else {
104 domain.setLength(0); // reset (when multi-valued RDN or non-DC)
105 }
106 }
107 return (domain.length() != 0) ? domain.toString() : null;
108 }
109
110 /**
111 * Locates the LDAP service for a given domain.
112 * Queries DNS for a list of LDAP Service Location Records (SRV) for a
113 * given domain name.
114 *
115 * @param domainName A string domain name.
116 * @param environment The possibly null environment of the context.
117 * @return An ordered list of hostports for the LDAP service or null if
118 * the service has not been located.
119 */
120 static String[] getLdapService(String domainName, Hashtable environment) {
121
122 if (domainName == null || domainName.length() == 0) {
123 return null;
124 }
125
126 String dnsUrl = "dns:///_ldap._tcp." + domainName;
127 String[] hostports = null;
128
129 try {
130 // Create the DNS context using NamingManager rather than using
131 // the initial context constructor. This avoids having the initial
132 // context constructor call itself (when processing the URL
133 // argument in the getAttributes call).
134 Context ctx = NamingManager.getURLContext("dns", environment);
135 if (!(ctx instanceof DirContext)) {
136 return null; // cannot create a DNS context
137 }
138 Attributes attrs =
139 ((DirContext)ctx).getAttributes(dnsUrl, SRV_RR_ATTR);
140 Attribute attr;
141
142 if (attrs != null && ((attr = attrs.get(SRV_RR)) != null)) {
143 int numValues = attr.size();
144 int numRecords = 0;
145 SrvRecord[] srvRecords = new SrvRecord[numValues];
146
147 // create the service records
148 int i = 0;
149 int j = 0;
150 while (i < numValues) {
151 try {
152 srvRecords[j] = new SrvRecord((String) attr.get(i));
153 j++;
154 } catch (Exception e) {
155 // ignore bad value
156 }
157 i++;
158 }
159 numRecords = j;
160
161 // trim
162 if (numRecords < numValues) {
163 SrvRecord[] trimmed = new SrvRecord[numRecords];
164 System.arraycopy(srvRecords, 0, trimmed, 0, numRecords);
165 srvRecords = trimmed;
166 }
167
168 // Sort the service records in ascending order of their
169 // priority value. For records with equal priority, move
170 // those with weight 0 to the top of the list.
171 if (numRecords > 1) {
172 Arrays.sort(srvRecords);
173 }
174
175 // extract the host and port number from each service record
176 hostports = extractHostports(srvRecords);
177 }
178 } catch (NamingException e) {
179 // ignore
180 }
181 return hostports;
182 }
183
184 /**
185 * Extract hosts and port numbers from a list of SRV records.
186 * An array of hostports is returned or null if none were found.
187 */
188 private static String[] extractHostports(SrvRecord[] srvRecords) {
189 String[] hostports = null;
190
191 int head = 0;
192 int tail = 0;
193 int sublistLength = 0;
194 int k = 0;
195 for (int i = 0; i < srvRecords.length; i++) {
196 if (hostports == null) {
197 hostports = new String[srvRecords.length];
198 }
199 // find the head and tail of the list of records having the same
200 // priority value.
201 head = i;
202 while (i < srvRecords.length - 1 &&
203 srvRecords[i].priority == srvRecords[i + 1].priority) {
204 i++;
205 }
206 tail = i;
207
208 // select hostports from the sublist
209 sublistLength = (tail - head) + 1;
210 for (int j = 0; j < sublistLength; j++) {
211 hostports[k++] = selectHostport(srvRecords, head, tail);
212 }
213 }
214 return hostports;
215 }
216
217 /*
218 * Randomly select a service record in the range [head, tail] and return
219 * its hostport value. Follows the algorithm in RFC 2782.
220 */
221 private static String selectHostport(SrvRecord[] srvRecords, int head,
222 int tail) {
223 if (head == tail) {
224 return srvRecords[head].hostport;
225 }
226
227 // compute the running sum for records between head and tail
228 int sum = 0;
229 for (int i = head; i <= tail; i++) {
230 if (srvRecords[i] != null) {
231 sum += srvRecords[i].weight;
232 srvRecords[i].sum = sum;
233 }
234 }
235 String hostport = null;
236
237 // If all records have zero weight, select first available one;
238 // otherwise, randomly select a record according to its weight
239 int target = (sum == 0 ? 0 : random.nextInt(sum + 1));
240 for (int i = head; i <= tail; i++) {
241 if (srvRecords[i] != null && srvRecords[i].sum >= target) {
242 hostport = srvRecords[i].hostport;
243 srvRecords[i] = null; // make this record unavailable
244 break;
245 }
246 }
247 return hostport;
248 }
249
250 /**
251 * This class holds a DNS service (SRV) record.
252 * See http://www.ietf.org/rfc/rfc2782.txt
253 */
254
255 static class SrvRecord implements Comparable {
256
257 int priority;
258 int weight;
259 int sum;
260 String hostport;
261
262 /**
263 * Creates a service record object from a string record.
264 * DNS supplies the string record in the following format:
265 * <pre>
266 * <Priority> " " <Weight> " " <Port> " " <Host>
267 * </pre>
268 */
269 SrvRecord(String srvRecord) throws Exception {
270 StringTokenizer tokenizer = new StringTokenizer(srvRecord, " ");
271 String port;
272
273 if (tokenizer.countTokens() == 4) {
274 priority = Integer.parseInt(tokenizer.nextToken());
275 weight = Integer.parseInt(tokenizer.nextToken());
276 port = tokenizer.nextToken();
277 hostport = tokenizer.nextToken() + ":" + port;
278 } else {
279 throw new IllegalArgumentException();
280 }
281 }
282
283 /*
284 * Sort records in ascending order of priority value. For records with
285 * equal priority move those with weight 0 to the top of the list.
286 */
287 public int compareTo(Object o) {
288 SrvRecord that = (SrvRecord) o;
289 if (priority > that.priority) {
290 return 1; // this > that
291 } else if (priority < that.priority) {
292 return -1; // this < that
293 } else if (weight == 0 && that.weight != 0) {
294 return -1; // this < that
295 } else if (weight != 0 && that.weight == 0) {
296 return 1; // this > that
297 } else {
298 return 0; // this == that
299 }
300 }
301 }
302 }