1 /* Support for Robot Exclusion Standard (RES).
2 Copyright (C) 2001 Free Software Foundation, Inc.
4 This file is part of Wget.
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or (at
9 your option) any later version.
11 This program is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20 In addition, as a special exception, the Free Software Foundation
21 gives permission to link the code of its release of Wget with the
22 OpenSSL project's "OpenSSL" library (or with modified versions of it
23 that use the same license as the "OpenSSL" library), and distribute
24 the linked executables. You must obey the GNU General Public License
25 in all respects for all of the code used other than "OpenSSL". If you
26 modify this file, you may extend this exception to your version of the
27 file, but you are not obligated to do so. If you do not wish to do
28 so, delete this exception statement from your version. */
30 /* This file implements the Robot Exclusion Standard (RES).
32 RES is a simple protocol that enables site admins to signalize to
33 the web crawlers that certain parts of the site should not be
34 accessed. All the admin needs to do is create a "robots.txt" file
35 in the web server root, and use simple commands to allow or
36 disallow access to certain parts of the site.
38 The first specification was written by Martijn Koster in 1994, and
39 is still available at <http://www.robotstxt.org/wc/norobots.html>.
40 In 1996, Martijn wrote an Internet Draft specifying an improved RES
41 specification; however, that work was apparently abandoned since
42 the draft has expired in 1997 and hasn't been replaced since. The
44 <http://www.robotstxt.org/wc/norobots-rfc.html>.
46 This file implements RES as specified by the draft. Note that this
47 only handles the "robots.txt" support. The META tag that controls
48 whether the links should be followed is handled in `html-url.c'.
52 * The end-of-line comment recognition is more in the spirit of the
53 Bourne Shell (as specified by RES-1994). That means that
54 "foo#bar" is taken literally, whereas "foo #bar" is interpreted
55 as "foo". The Draft apparently specifies that both should be
58 * We don't recognize sole CR as the line ending.
60 * We don't implement expiry mechanism for /robots.txt specs. I
61 consider it non-necessary for a relatively short-lived
62 application such as Wget. Besides, it is highly questionable
63 whether anyone deploys the recommended expiry scheme for
66 Entry points are functions res_parse, res_parse_from_file,
67 res_match_path, res_register_specs, res_get_specs, and
80 #endif /* HAVE_STRING_H */
94 int user_agent_exact_p;
100 struct path_info *paths;
103 /* Parsing the robot spec. */
105 /* Check whether AGENT (a string of length LENGTH) equals "wget" or
106 "*". If it is either of them, *matches is set to one. If it is
107 "wget", *exact_match is set to one. */
110 match_user_agent (const char *agent, int length,
111 int *matches, int *exact_match)
113 if (length == 1 && *agent == '*')
118 else if (BOUNDED_EQUAL_NO_CASE (agent, agent + length, "wget"))
130 /* Add a path specification between PATH_B and PATH_E as one of the
134 add_path (struct robot_specs *specs, const char *path_b, const char *path_e,
135 int allowedp, int exactp)
138 if (path_b < path_e && *path_b == '/')
139 /* Our path representation doesn't use a leading slash, so remove
142 pp.path = strdupdelim (path_b, path_e);
143 pp.allowedp = allowedp;
144 pp.user_agent_exact_p = exactp;
146 if (specs->count > specs->size)
148 if (specs->size == 0)
152 specs->paths = xrealloc (specs->paths,
153 specs->size * sizeof (struct path_info));
155 specs->paths[specs->count - 1] = pp;
158 /* Recreate SPECS->paths with only those paths that have non-zero
159 user_agent_exact_p. */
162 prune_non_exact (struct robot_specs *specs)
164 struct path_info *newpaths;
167 for (i = 0; i < specs->count; i++)
168 if (specs->paths[i].user_agent_exact_p)
170 newpaths = xmalloc (cnt * sizeof (struct path_info));
171 for (i = 0, j = 0; i < specs->count; i++)
172 if (specs->paths[i].user_agent_exact_p)
173 newpaths[j++] = specs->paths[i];
175 xfree (specs->paths);
176 specs->paths = newpaths;
181 #define EOL(p) ((p) >= lineend)
183 #define SKIP_SPACE(p) do { \
184 while (!EOL (p) && ISSPACE (*p)) \
188 #define FIELD_IS(string_literal) \
189 BOUNDED_EQUAL_NO_CASE (field_b, field_e, string_literal)
191 /* Parse textual RES specs beginning with SOURCE of length LENGTH.
192 Return a specs objects ready to be fed to res_match_path.
194 The parsing itself is trivial, but creating a correct SPECS object
195 is trickier than it seems, because RES is surprisingly byzantine if
196 you attempt to implement it correctly.
198 A "record" is a block of one or more `User-Agent' lines followed by
199 one or more `Allow' or `Disallow' lines. Record is accepted by
200 Wget if one of the `User-Agent' lines was "wget", or if the user
203 After all the lines have been read, we examine whether an exact
204 ("wget") user-agent field was specified. If so, we delete all the
205 lines read under "User-Agent: *" blocks because we have our own
206 Wget-specific blocks. This enables the admin to say:
215 This means that to Wget and to Google, /cgi-bin is disallowed,
216 whereas for all other crawlers, everything is disallowed.
217 res_parse is implemented so that the order of records doesn't
218 matter. In the case above, the "User-Agent: *" could have come
219 after the other one. */
222 res_parse (const char *source, int length)
226 const char *p = source;
227 const char *end = source + length;
229 /* non-zero if last applicable user-agent field matches Wget. */
230 int user_agent_applies = 0;
232 /* non-zero if last applicable user-agent field *exactly* matches
234 int user_agent_exact = 0;
236 /* whether we ever encountered exact user agent. */
239 /* count of allow/disallow lines in the current "record", i.e. after
240 the last `user-agent' instructions. */
241 int record_count = 0;
243 struct robot_specs *specs = xmalloc (sizeof (struct robot_specs));
244 memset (specs, '\0', sizeof (struct robot_specs));
248 const char *lineend, *lineend_real;
249 const char *field_b, *field_e;
250 const char *value_b, *value_e;
254 lineend_real = memchr (p, '\n', end - p);
259 lineend = lineend_real;
261 /* Before doing anything else, check whether the line is empty
264 if (EOL (p) || *p == '#')
267 /* Make sure the end-of-line comments are respected by setting
268 lineend to a location preceding the first comment. Real line
269 ending remains in lineend_real. */
270 for (lineend = p; lineend < lineend_real; lineend++)
271 if ((lineend == p || ISSPACE (*(lineend - 1)))
275 /* Ignore trailing whitespace in the same way. */
276 while (lineend > p && ISSPACE (*(lineend - 1)))
282 while (!EOL (p) && (ISALNUM (*p) || *p == '-'))
287 if (field_b == field_e || EOL (p) || *p != ':')
289 DEBUGP (("Ignoring malformed line %d", line_count));
300 /* Finally, we have a syntactically valid line. */
301 if (FIELD_IS ("user-agent"))
303 /* We have to support several cases:
310 ... matching record ...
314 ... non-matching record ...
317 ... matching record, but will be pruned later ...
319 We have to respect `User-Agent' at the beginning of each
320 new record simply because we don't know if we're going to
321 encounter "Wget" among the agents or not. Hence,
322 match_user_agent is called when record_count != 0.
324 But if record_count is 0, we have to keep calling it
325 until it matches, and if that happens, we must not call
326 it any more, until the next record. Hence the other part
328 if (record_count != 0 || user_agent_applies == 0)
329 match_user_agent (value_b, value_e - value_b,
330 &user_agent_applies, &user_agent_exact);
331 if (user_agent_exact)
335 else if (FIELD_IS ("allow"))
337 if (user_agent_applies)
339 add_path (specs, value_b, value_e, 1, user_agent_exact);
343 else if (FIELD_IS ("disallow"))
345 if (user_agent_applies)
348 if (value_b == value_e)
349 /* Empty "disallow" line means everything is
352 add_path (specs, value_b, value_e, allowed, user_agent_exact);
358 DEBUGP (("Ignoring unknown field at line %d", line_count));
369 /* We've encountered an exactly matching user-agent. Throw out
370 all the stuff with user-agent: *. */
371 prune_non_exact (specs);
373 else if (specs->size > specs->count)
375 /* add_path normally over-allocates specs->paths. Reallocate it
376 to the correct size in order to conserve some memory. */
377 specs->paths = xrealloc (specs->paths,
378 specs->count * sizeof (struct path_info));
379 specs->size = specs->count;
385 /* The same like res_parse, but first map the FILENAME into memory,
386 and then parse it. */
389 res_parse_from_file (const char *filename)
391 struct robot_specs *specs;
392 struct file_memory *fm = read_file (filename);
395 logprintf (LOG_NOTQUIET, "Cannot open %s: %s",
396 filename, strerror (errno));
399 specs = res_parse (fm->content, fm->length);
405 free_specs (struct robot_specs *specs)
408 for (i = 0; i < specs->count; i++)
409 xfree (specs->paths[i].path);
410 FREE_MAYBE (specs->paths);
414 /* Matching of a path according to the specs. */
416 /* If C is '%' and (ptr[1], ptr[2]) form a hexadecimal number, and if
417 that number is not a numerical representation of '/', decode C and
418 advance the pointer. */
420 #define DECODE_MAYBE(c, ptr) do { \
421 if (c == '%' && ISXDIGIT (ptr[1]) && ISXDIGIT (ptr[2])) \
423 char decoded = X2DIGITS_TO_NUM (ptr[1], ptr[2]); \
424 if (decoded != '/') \
432 /* The inner matching engine: return non-zero if RECORD_PATH matches
433 URL_PATH. The rules for matching are described at
434 <http://www.robotstxt.org/wc/norobots-rfc.txt>, section 3.2.2. */
437 matches (const char *record_path, const char *url_path)
439 const char *rp = record_path;
440 const char *up = url_path;
450 DECODE_MAYBE(rc, rp);
451 DECODE_MAYBE(uc, up);
457 /* Iterate through all paths in SPECS. For the first one that
458 matches, return its allow/reject status. If none matches,
459 retrieval is by default allowed. */
462 res_match_path (const struct robot_specs *specs, const char *path)
467 for (i = 0; i < specs->count; i++)
468 if (matches (specs->paths[i].path, path))
470 int allowedp = specs->paths[i].allowedp;
471 DEBUGP (("%s path %s because of rule `%s'.\n",
472 allowedp ? "Allowing" : "Rejecting",
473 path, specs->paths[i].path));
479 /* Registering the specs. */
481 static struct hash_table *registered_specs;
483 /* Stolen from cookies.c. */
484 #define SET_HOSTPORT(host, port, result) do { \
485 int HP_len = strlen (host); \
486 result = alloca (HP_len + 1 + numdigit (port) + 1); \
487 memcpy (result, host, HP_len); \
488 result[HP_len] = ':'; \
489 number_to_string (result + HP_len + 1, port); \
492 /* Register RES specs that below to server on HOST:PORT. They will
493 later be retrievable using res_get_specs. */
496 res_register_specs (const char *host, int port, struct robot_specs *specs)
498 struct robot_specs *old;
500 SET_HOSTPORT (host, port, hp);
502 if (!registered_specs)
503 registered_specs = make_nocase_string_hash_table (0);
505 /* Required to shut up the compiler. */
509 if (hash_table_get_pair (registered_specs, hp, hp_old, old))
513 hash_table_put (registered_specs, hp_old, specs);
517 hash_table_put (registered_specs, xstrdup (hp), specs);
521 /* Get the specs that belong to HOST:PORT. */
524 res_get_specs (const char *host, int port)
527 SET_HOSTPORT (host, port, hp);
528 if (!registered_specs)
530 return hash_table_get (registered_specs, hp);
533 /* Loading the robots file. */
535 #define RES_SPECS_LOCATION "/robots.txt"
537 /* Retrieve the robots.txt from the server root of the server that
538 serves URL. The file will be named according to the currently
539 active rules, and the file name will be returned in *file.
541 Return non-zero if robots were retrieved OK, zero otherwise. */
544 res_retrieve_file (const char *url, char **file)
547 char *robots_url = uri_merge (url, RES_SPECS_LOCATION);
549 logputs (LOG_VERBOSE, _("Loading robots.txt; please ignore errors.\n"));
551 err = retrieve_url (robots_url, file, NULL, NULL, NULL);
554 if (err != RETROK && *file != NULL)
556 /* If the file is not retrieved correctly, but retrieve_url
557 allocated the file name, deallocate is here so that the
558 caller doesn't have to worry about it. */
562 return err == RETROK;
566 cleanup_hash_table_mapper (void *key, void *value, void *arg_ignored)
576 if (registered_specs)
578 hash_table_map (registered_specs, cleanup_hash_table_mapper, NULL);
579 hash_table_destroy (registered_specs);
580 registered_specs = NULL;