001 /*
002 * Copyright (C) 2009 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package com.google.common.net;
018
019 import static com.google.common.base.Preconditions.checkArgument;
020 import static com.google.common.base.Preconditions.checkNotNull;
021 import static com.google.common.base.Preconditions.checkState;
022
023 import com.google.common.annotations.Beta;
024 import com.google.common.annotations.GwtCompatible;
025 import com.google.common.base.Ascii;
026 import com.google.common.base.CharMatcher;
027 import com.google.common.base.Joiner;
028 import com.google.common.base.Objects;
029 import com.google.common.base.Splitter;
030 import com.google.common.collect.ImmutableList;
031
032 import java.util.List;
033
034 import javax.annotation.Nullable;
035
036 /**
037 * An immutable well-formed internet domain name, such as {@code com} or {@code
038 * foo.co.uk}. Only syntactic analysis is performed; no DNS lookups or other
039 * network interactions take place. Thus there is no guarantee that the domain
040 * actually exists on the internet.
041 *
042 * <p>One common use of this class is to determine whether a given string is
043 * likely to represent an addressable domain on the web -- that is, for a
044 * candidate string {@code "xxx"}, might browsing to {@code "http://xxx/"}
045 * result in a webpage being displayed? In the past, this test was frequently
046 * done by determining whether the domain ended with a {@linkplain
047 * #isPublicSuffix() public suffix} but was not itself a public suffix. However,
048 * this test is no longer accurate. There are many domains which are both public
049 * suffixes and addressable as hosts; {@code "uk.com"} is one example. As a
050 * result, the only useful test to determine if a domain is a plausible web host
051 * is {@link #hasPublicSuffix()}. This will return {@code true} for many domains
052 * which (currently) are not hosts, such as {@code "com"}), but given that any
053 * public suffix may become a host without warning, it is better to err on the
054 * side of permissiveness and thus avoid spurious rejection of valid sites.
055 *
056 * <p>During construction, names are normalized in two ways:
057 * <ol>
058 * <li>ASCII uppercase characters are converted to lowercase.
059 * <li>Unicode dot separators other than the ASCII period ({@code '.'}) are
060 * converted to the ASCII period.
061 * </ol>
062 * The normalized values will be returned from {@link #name()} and
063 * {@link #parts()}, and will be reflected in the result of
064 * {@link #equals(Object)}.
065 *
066 * <p><a href="http://en.wikipedia.org/wiki/Internationalized_domain_name">
067 * internationalized domain names</a> such as {@code 网络.cn} are supported, as
068 * are the equivalent <a
069 * href="http://en.wikipedia.org/wiki/Internationalized_domain_name">IDNA
070 * Punycode-encoded</a> versions.
071 *
072 * @author Craig Berry
073 * @since 5.0
074 */
075 @Beta
076 @GwtCompatible(emulated = true)
077 public final class InternetDomainName {
078
079 private static final CharMatcher DOTS_MATCHER =
080 CharMatcher.anyOf(".\u3002\uFF0E\uFF61");
081 private static final Splitter DOT_SPLITTER = Splitter.on('.');
082 private static final Joiner DOT_JOINER = Joiner.on('.');
083
084 /**
085 * Value of {@link #publicSuffixIndex} which indicates that no public suffix
086 * was found.
087 */
088 private static final int NO_PUBLIC_SUFFIX_FOUND = -1;
089
090 private static final String DOT_REGEX = "\\.";
091
092 /**
093 * Maximum parts (labels) in a domain name. This value arises from
094 * the 255-octet limit described in
095 * <a href="http://www.ietf.org/rfc/rfc2181.txt">RFC 2181</a> part 11 with
096 * the fact that the encoding of each part occupies at least two bytes
097 * (dot plus label externally, length byte plus label internally). Thus, if
098 * all labels have the minimum size of one byte, 127 of them will fit.
099 */
100 private static final int MAX_PARTS = 127;
101
102 /**
103 * Maximum length of a full domain name, including separators, and
104 * leaving room for the root label. See
105 * <a href="http://www.ietf.org/rfc/rfc2181.txt">RFC 2181</a> part 11.
106 */
107 private static final int MAX_LENGTH = 253;
108
109 /**
110 * Maximum size of a single part of a domain name. See
111 * <a href="http://www.ietf.org/rfc/rfc2181.txt">RFC 2181</a> part 11.
112 */
113 private static final int MAX_DOMAIN_PART_LENGTH = 63;
114
115 /**
116 * The full domain name, converted to lower case.
117 */
118 private final String name;
119
120 /**
121 * The parts of the domain name, converted to lower case.
122 */
123 private final ImmutableList<String> parts;
124
125 /**
126 * The index in the {@link #parts()} list at which the public suffix begins.
127 * For example, for the domain name {@code www.google.co.uk}, the value would
128 * be 2 (the index of the {@code co} part). The value is negative
129 * (specifically, {@link #NO_PUBLIC_SUFFIX_FOUND}) if no public suffix was
130 * found.
131 */
132 private final int publicSuffixIndex;
133
134 /**
135 * Constructor used to implement {@link #from(String)}, and from subclasses.
136 */
137 InternetDomainName(String name) {
138 // Normalize:
139 // * ASCII characters to lowercase
140 // * All dot-like characters to '.'
141 // * Strip trailing '.'
142
143 name = Ascii.toLowerCase(DOTS_MATCHER.replaceFrom(name, '.'));
144
145 if (name.endsWith(".")) {
146 name = name.substring(0, name.length() - 1);
147 }
148
149 checkArgument(name.length() <= MAX_LENGTH, "Domain name too long: '%s':", name);
150 this.name = name;
151
152 this.parts = ImmutableList.copyOf(DOT_SPLITTER.split(name));
153 checkArgument(parts.size() <= MAX_PARTS, "Domain has too many parts: '%s'", name);
154 checkArgument(validateSyntax(parts), "Not a valid domain name: '%s'", name);
155
156 this.publicSuffixIndex = findPublicSuffix();
157 }
158
159 /**
160 * Returns the index of the leftmost part of the public suffix, or -1 if not
161 * found. Note that the value defined as the "public suffix" may not be a
162 * public suffix according to {@link #isPublicSuffix()} if the domain ends
163 * with an excluded domain pattern such as {@code "nhs.uk"}.
164 */
165 private int findPublicSuffix() {
166 final int partsSize = parts.size();
167
168 for (int i = 0; i < partsSize; i++) {
169 String ancestorName = DOT_JOINER.join(parts.subList(i, partsSize));
170
171 if (TldPatterns.EXACT.contains(ancestorName)) {
172 return i;
173 }
174
175 // Excluded domains (e.g. !nhs.uk) use the next highest
176 // domain as the effective public suffix (e.g. uk).
177
178 if (TldPatterns.EXCLUDED.contains(ancestorName)) {
179 return i + 1;
180 }
181
182 if (matchesWildcardPublicSuffix(ancestorName)) {
183 return i;
184 }
185 }
186
187 return NO_PUBLIC_SUFFIX_FOUND;
188 }
189
190 /**
191 * A deprecated synonym for {@link #from(String)}.
192 *
193 * @param domain A domain name (not IP address)
194 * @throws IllegalArgumentException if {@code name} is not syntactically valid
195 * according to {@link #isValidLenient}
196 * @since 8.0 (previously named {@code from})
197 * @deprecated Use {@link #from(String)}
198 */
199 @Deprecated
200 public static InternetDomainName fromLenient(String domain) {
201 return from(domain);
202 }
203
204 /**
205 * Returns an instance of {@link InternetDomainName} after lenient
206 * validation. Specifically, validation against <a
207 * href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>
208 * ("Internationalizing Domain Names in Applications") is skipped, while
209 * validation against <a
210 * href="http://www.ietf.org/rfc/rfc1035.txt">RFC 1035</a> is relaxed in
211 * the following ways:
212 * <ul>
213 * <li>Any part containing non-ASCII characters is considered valid.
214 * <li>Underscores ('_') are permitted wherever dashes ('-') are permitted.
215 * <li>Parts other than the final part may start with a digit.
216 * </ul>
217 *
218 *
219 * @param domain A domain name (not IP address)
220 * @throws IllegalArgumentException if {@code name} is not syntactically valid
221 * according to {@link #isValid}
222 * @since 10.0 (previously named {@code fromLenient})
223 */
224 public static InternetDomainName from(String domain) {
225 return new InternetDomainName(checkNotNull(domain));
226 }
227
228 /**
229 * Validation method used by {@from} to ensure that the domain name is
230 * syntactically valid according to RFC 1035.
231 *
232 * @return Is the domain name syntactically valid?
233 */
234 private static boolean validateSyntax(List<String> parts) {
235 final int lastIndex = parts.size() - 1;
236
237 // Validate the last part specially, as it has different syntax rules.
238
239 if (!validatePart(parts.get(lastIndex), true)) {
240 return false;
241 }
242
243 for (int i = 0; i < lastIndex; i++) {
244 String part = parts.get(i);
245 if (!validatePart(part, false)) {
246 return false;
247 }
248 }
249
250 return true;
251 }
252
253 private static final CharMatcher DASH_MATCHER = CharMatcher.anyOf("-_");
254
255 private static final CharMatcher PART_CHAR_MATCHER =
256 CharMatcher.JAVA_LETTER_OR_DIGIT.or(DASH_MATCHER);
257
258 /**
259 * Helper method for {@link #validateSyntax(List)}. Validates that one part of
260 * a domain name is valid.
261 *
262 * @param part The domain name part to be validated
263 * @param isFinalPart Is this the final (rightmost) domain part?
264 * @return Whether the part is valid
265 */
266 private static boolean validatePart(String part, boolean isFinalPart) {
267
268 // These tests could be collapsed into one big boolean expression, but
269 // they have been left as independent tests for clarity.
270
271 if (part.length() < 1 || part.length() > MAX_DOMAIN_PART_LENGTH) {
272 return false;
273 }
274
275 /*
276 * GWT claims to support java.lang.Character's char-classification methods,
277 * but it actually only works for ASCII. So for now, assume any non-ASCII
278 * characters are valid. The only place this seems to be documented is here:
279 * http://osdir.com/ml/GoogleWebToolkitContributors/2010-03/msg00178.html
280 *
281 * <p>ASCII characters in the part are expected to be valid per RFC 1035,
282 * with underscore also being allowed due to widespread practice.
283 */
284
285 String asciiChars = CharMatcher.ASCII.retainFrom(part);
286
287 if (!PART_CHAR_MATCHER.matchesAllOf(asciiChars)) {
288 return false;
289 }
290
291 // No initial or final dashes or underscores.
292
293 if (DASH_MATCHER.matches(part.charAt(0))
294 || DASH_MATCHER.matches(part.charAt(part.length() - 1))) {
295 return false;
296 }
297
298 /*
299 * Note that we allow (in contravention of a strict interpretation of the
300 * relevant RFCs) domain parts other than the last may begin with a digit
301 * (for example, "3com.com"). It's important to disallow an initial digit in
302 * the last part; it's the only thing that stops an IPv4 numeric address
303 * like 127.0.0.1 from looking like a valid domain name.
304 */
305
306 if (isFinalPart && CharMatcher.DIGIT.matches(part.charAt(0))) {
307 return false;
308 }
309
310 return true;
311 }
312
313 /**
314 * Returns the domain name, normalized to all lower case.
315 */
316 public String name() {
317 return name;
318 }
319
320 /**
321 * Returns the individual components of this domain name, normalized to all
322 * lower case. For example, for the domain name {@code mail.google.com}, this
323 * method returns the list {@code ["mail", "google", "com"]}.
324 */
325 public ImmutableList<String> parts() {
326 return parts;
327 }
328
329 /**
330 * Indicates whether this domain name represents a <i>public suffix</i>, as
331 * defined by the Mozilla Foundation's
332 * <a href="http://publicsuffix.org/">Public Suffix List</a> (PSL). A public
333 * suffix is one under which Internet users can directly register names, such
334 * as {@code com}, {@code co.uk} or {@code pvt.k12.wy.us}. Examples of domain
335 * names that are <i>not</i> public suffixes include {@code google}, {@code
336 * google.com} and {@code foo.co.uk}.
337 *
338 * @return {@code true} if this domain name appears exactly on the public
339 * suffix list
340 * @since 6.0
341 */
342 public boolean isPublicSuffix() {
343 return publicSuffixIndex == 0;
344 }
345
346 /**
347 * Indicates whether this domain name ends in a {@linkplain #isPublicSuffix()
348 * public suffix}, including if it is a public suffix itself. For example,
349 * returns {@code true} for {@code www.google.com}, {@code foo.co.uk} and
350 * {@code com}, but not for {@code google} or {@code google.foo}. This is
351 * the recommended method for determining whether a domain is potentially an
352 * addressable host.
353 *
354 * @since 6.0
355 */
356 public boolean hasPublicSuffix() {
357 return publicSuffixIndex != NO_PUBLIC_SUFFIX_FOUND;
358 }
359
360 /**
361 * Returns the {@linkplain #isPublicSuffix() public suffix} portion of the
362 * domain name, or {@code null} if no public suffix is present.
363 *
364 * @since 6.0
365 */
366 public InternetDomainName publicSuffix() {
367 return hasPublicSuffix() ? ancestor(publicSuffixIndex) : null;
368 }
369
370 /**
371 * Indicates whether this domain name ends in a {@linkplain #isPublicSuffix()
372 * public suffix}, while not being a public suffix itself. For example,
373 * returns {@code true} for {@code www.google.com}, {@code foo.co.uk} and
374 * {@code bar.ca.us}, but not for {@code google}, {@code com}, or {@code
375 * google.foo}.
376 *
377 * <p><b>Warning:</b> a {@code false} result from this method does not imply
378 * that the domain does not represent an addressable host, as many public
379 * suffixes are also addressable hosts. Use {@link #hasPublicSuffix()} for
380 * that test.
381 *
382 * <p>This method can be used to determine whether it will probably be
383 * possible to set cookies on the domain, though even that depends on
384 * individual browsers' implementations of cookie controls. See
385 * <a href="http://www.ietf.org/rfc/rfc2109.txt">RFC 2109</a> for details.
386 *
387 * @since 6.0
388 */
389 public boolean isUnderPublicSuffix() {
390 return publicSuffixIndex > 0;
391 }
392
393 /**
394 * Indicates whether this domain name is composed of exactly one subdomain
395 * component followed by a {@linkplain #isPublicSuffix() public suffix}. For
396 * example, returns {@code true} for {@code google.com} and {@code foo.co.uk},
397 * but not for {@code www.google.com} or {@code co.uk}.
398 *
399 * <p><b>Warning:</b> A {@code true} result from this method does not imply
400 * that the domain is at the highest level which is addressable as a host, as
401 * many public suffixes are also addressable hosts. For example, the domain
402 * {@code bar.uk.com} has a public suffix of {@code uk.com}, so it would
403 * return {@code true} from this method. But {@code uk.com} is itself an
404 * addressable host.
405 *
406 * <p>This method can be used to determine whether a domain is probably the
407 * highest level for which cookies may be set, though even that depends on
408 * individual browsers' implementations of cookie controls. See
409 * <a href="http://www.ietf.org/rfc/rfc2109.txt">RFC 2109</a> for details.
410 *
411 * @since 6.0
412 */
413 public boolean isTopPrivateDomain() {
414 return publicSuffixIndex == 1;
415 }
416
417 /**
418 * Returns the portion of this domain name that is one level beneath the
419 * public suffix. For example, for {@code x.adwords.google.co.uk} it returns
420 * {@code google.co.uk}, since {@code co.uk} is a public suffix.
421 *
422 * <p>If {@link #isTopPrivateDomain()} is true, the current domain name
423 * instance is returned.
424 *
425 * <p>This method should not be used to determine the topmost parent domain
426 * which is addressable as a host, as many public suffixes are also
427 * addressable hosts. For example, the domain {@code foo.bar.uk.com} has
428 * a public suffix of {@code uk.com}, so it would return {@code bar.uk.com}
429 * from this method. But {@code uk.com} is itself an addressable host.
430 *
431 * <p>This method can be used to determine the probable highest level parent
432 * domain for which cookies may be set, though even that depends on individual
433 * browsers' implementations of cookie controls.
434 *
435 * @throws IllegalStateException if this domain does not end with a
436 * public suffix
437 * @since 6.0
438 */
439 public InternetDomainName topPrivateDomain() {
440 if (isTopPrivateDomain()) {
441 return this;
442 }
443 checkState(isUnderPublicSuffix(), "Not under a public suffix: %s", name);
444 return ancestor(publicSuffixIndex - 1);
445 }
446
447 /**
448 * Indicates whether this domain is composed of two or more parts.
449 */
450 public boolean hasParent() {
451 return parts.size() > 1;
452 }
453
454 /**
455 * Returns an {@code InternetDomainName} that is the immediate ancestor of
456 * this one; that is, the current domain with the leftmost part removed. For
457 * example, the parent of {@code www.google.com} is {@code google.com}.
458 *
459 * @throws IllegalStateException if the domain has no parent, as determined
460 * by {@link #hasParent}
461 */
462 public InternetDomainName parent() {
463 checkState(hasParent(), "Domain '%s' has no parent", name);
464 return ancestor(1);
465 }
466
467 /**
468 * Returns the ancestor of the current domain at the given number of levels
469 * "higher" (rightward) in the subdomain list. The number of levels must be
470 * non-negative, and less than {@code N-1}, where {@code N} is the number of
471 * parts in the domain.
472 *
473 * <p>TODO: Reasonable candidate for addition to public API.
474 */
475 private InternetDomainName ancestor(int levels) {
476 return from(DOT_JOINER.join(parts.subList(levels, parts.size())));
477 }
478
479 /**
480 * Creates and returns a new {@code InternetDomainName} by prepending the
481 * argument and a dot to the current name. For example, {@code
482 * InternetDomainName.from("foo.com").child("www.bar")} returns a new
483 * {@code InternetDomainName} with the value {@code www.bar.foo.com}. Only
484 * lenient validation is performed, as described {@link #from(String) here}.
485 *
486 * @throws NullPointerException if leftParts is null
487 * @throws IllegalArgumentException if the resulting name is not valid
488 */
489 public InternetDomainName child(String leftParts) {
490 return from(checkNotNull(leftParts) + "." + name);
491 }
492
493 /**
494 * A deprecated synonym for {@link #isValid(String)}.
495 *
496 * @since 8.0 (previously named {@code isValid})
497 * @deprecated Use {@link #isValid(String)} instead
498 */
499 @Deprecated
500 public static boolean isValidLenient(String name) {
501 return isValid(name);
502 }
503
504 /**
505 * Indicates whether the argument is a syntactically valid domain name using
506 * lenient validation. Specifically, validation against <a
507 * href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>
508 * ("Internationalizing Domain Names in Applications") is skipped.
509 *
510 * <p>The following two code snippets are equivalent:
511 *
512 * <pre> {@code
513 *
514 * domainName = InternetDomainName.isValid(name)
515 * ? InternetDomainName.from(name)
516 * : DEFAULT_DOMAIN;
517 * }</pre>
518 *
519 * <pre> {@code
520 *
521 * try {
522 * domainName = InternetDomainName.from(name);
523 * } catch (IllegalArgumentException e) {
524 * domainName = DEFAULT_DOMAIN;
525 * }}</pre>
526 *
527 * @since 8.0 (previously named {@code isValidLenient})
528 */
529 public static boolean isValid(String name) {
530 try {
531 from(name);
532 return true;
533 } catch (IllegalArgumentException e) {
534 return false;
535 }
536 }
537
538 /**
539 * Does the domain name match one of the "wildcard" patterns (e.g.
540 * {@code "*.ar"})?
541 */
542 private static boolean matchesWildcardPublicSuffix(String domain) {
543 final String[] pieces = domain.split(DOT_REGEX, 2);
544 return pieces.length == 2 && TldPatterns.UNDER.contains(pieces[1]);
545 }
546
547 // TODO: specify this to return the same as name(); remove name()
548 @Override
549 public String toString() {
550 return Objects.toStringHelper(this).add("name", name).toString();
551 }
552
553 /**
554 * Equality testing is based on the text supplied by the caller,
555 * after normalization as described in the class documentation. For
556 * example, a non-ASCII Unicode domain name and the Punycode version
557 * of the same domain name would not be considered equal.
558 *
559 */
560 @Override
561 public boolean equals(@Nullable Object object) {
562 if (object == this) {
563 return true;
564 }
565
566 if (object instanceof InternetDomainName) {
567 InternetDomainName that = (InternetDomainName) object;
568 return this.name.equals(that.name);
569 }
570
571 return false;
572 }
573
574 @Override
575 public int hashCode() {
576 return name.hashCode();
577 }
578 }