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1 // Copyright 2013 The Chromium Authors
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifdef UNSAFE_BUFFERS_BUILD
6 // TODO(crbug.com/350788890): Remove this and spanify to fix the errors.
7 #pragma allow_unsafe_buffers
8 #endif
9 
10 // Canonicalizer functions for working with and resolving relative URLs.
11 
12 #include <algorithm>
13 #include <ostream>
14 #include <string_view>
15 
16 #include "base/check_op.h"
17 #include "base/strings/string_util.h"
18 #include "url/url_canon.h"
19 #include "url/url_canon_internal.h"
20 #include "url/url_constants.h"
21 #include "url/url_features.h"
22 #include "url/url_file.h"
23 #include "url/url_parse_internal.h"
24 #include "url/url_util.h"
25 #include "url/url_util_internal.h"
26 
27 namespace url {
28 
29 namespace {
30 
31 // Firefox does a case-sensitive compare (which is probably wrong--Mozilla bug
32 // 379034), whereas IE is case-insensitive.
33 //
34 // We choose to be more permissive like IE. We don't need to worry about
35 // unescaping or anything here: neither IE or Firefox allow this. We also
36 // don't have to worry about invalid scheme characters since we are comparing
37 // against the canonical scheme of the base.
38 //
39 // The base URL should always be canonical, therefore it should be ASCII.
40 template<typename CHAR>
AreSchemesEqual(const char * base,const Component & base_scheme,const CHAR * cmp,const Component & cmp_scheme)41 bool AreSchemesEqual(const char* base,
42                      const Component& base_scheme,
43                      const CHAR* cmp,
44                      const Component& cmp_scheme) {
45   if (base_scheme.len != cmp_scheme.len)
46     return false;
47   for (int i = 0; i < base_scheme.len; i++) {
48     // We assume the base is already canonical, so we don't have to
49     // canonicalize it.
50     if (CanonicalSchemeChar(cmp[cmp_scheme.begin + i]) !=
51         base[base_scheme.begin + i])
52       return false;
53   }
54   return true;
55 }
56 
57 #ifdef WIN32
58 
59 // Here, we also allow Windows paths to be represented as "/C:/" so we can be
60 // consistent about URL paths beginning with slashes. This function is like
61 // DoesBeginWindowsDrivePath except that it also requires a slash at the
62 // beginning.
63 template<typename CHAR>
DoesBeginSlashWindowsDriveSpec(const CHAR * spec,int start_offset,int spec_len)64 bool DoesBeginSlashWindowsDriveSpec(const CHAR* spec, int start_offset,
65                                     int spec_len) {
66   if (start_offset >= spec_len)
67     return false;
68   return IsSlashOrBackslash(spec[start_offset]) &&
69          DoesBeginWindowsDriveSpec(spec, start_offset + 1, spec_len);
70 }
71 
72 #endif  // WIN32
73 
74 template <typename CHAR>
IsValidScheme(const CHAR * url,const Component & scheme)75 bool IsValidScheme(const CHAR* url, const Component& scheme) {
76   // Caller should ensure that the |scheme| is not empty.
77   DCHECK_NE(0, scheme.len);
78 
79   // From https://url.spec.whatwg.org/#scheme-start-state:
80   //   scheme start state:
81   //     1. If c is an ASCII alpha, append c, lowercased, to buffer, and set
82   //        state to scheme state.
83   //     2. Otherwise, if state override is not given, set state to no scheme
84   //        state, and decrease pointer by one.
85   //     3. Otherwise, validation error, return failure.
86   // Note that both step 2 and step 3 mean that the scheme was not valid.
87   if (!base::IsAsciiAlpha(url[scheme.begin]))
88     return false;
89 
90   // From https://url.spec.whatwg.org/#scheme-state:
91   //   scheme state:
92   //     1. If c is an ASCII alphanumeric, U+002B (+), U+002D (-), or U+002E
93   //        (.), append c, lowercased, to buffer.
94   //     2. Otherwise, if c is U+003A (:), then [...]
95   //
96   // We begin at |scheme.begin + 1|, because the character at |scheme.begin| has
97   // already been checked by base::IsAsciiAlpha above.
98   int scheme_end = scheme.end();
99   for (int i = scheme.begin + 1; i < scheme_end; i++) {
100     if (!CanonicalSchemeChar(url[i]))
101       return false;
102   }
103 
104   return true;
105 }
106 
107 // See IsRelativeURL in the header file for usage.
108 template<typename CHAR>
DoIsRelativeURL(const char * base,const Parsed & base_parsed,const CHAR * url,int url_len,bool is_base_hierarchical,bool * is_relative,Component * relative_component)109 bool DoIsRelativeURL(const char* base,
110                      const Parsed& base_parsed,
111                      const CHAR* url,
112                      int url_len,
113                      bool is_base_hierarchical,
114                      bool* is_relative,
115                      Component* relative_component) {
116   *is_relative = false;  // So we can default later to not relative.
117 
118   // Trim whitespace and construct a new range for the substring.
119   int begin = 0;
120   TrimURL(url, &begin, &url_len);
121   if (begin >= url_len) {
122     // Empty URLs are relative, but do nothing.
123     if (!is_base_hierarchical) {
124       // Don't allow relative URLs if the base scheme doesn't support it.
125       return false;
126     }
127     *relative_component = Component(begin, 0);
128     *is_relative = true;
129     return true;
130   }
131 
132 #ifdef WIN32
133   // We special case paths like "C:\foo" so they can link directly to the
134   // file on Windows (IE compatibility). The security domain stuff should
135   // prevent a link like this from actually being followed if its on a
136   // web page.
137   //
138   // We treat "C:/foo" as an absolute URL. We can go ahead and treat "/c:/"
139   // as relative, as this will just replace the path when the base scheme
140   // is a file and the answer will still be correct.
141   //
142   // We require strict backslashes when detecting UNC since two forward
143   // slashes should be treated a a relative URL with a hostname.
144   if (DoesBeginWindowsDriveSpec(url, begin, url_len) ||
145       DoesBeginUNCPath(url, begin, url_len, true))
146     return true;
147 #endif  // WIN32
148 
149   // See if we've got a scheme, if not, we know this is a relative URL.
150   // BUT, just because we have a scheme, doesn't make it absolute.
151   // "http:foo.html" is a relative URL with path "foo.html". If the scheme is
152   // empty, we treat it as relative (":foo"), like IE does.
153   Component scheme;
154   const bool scheme_is_empty =
155       !ExtractScheme(url, url_len, &scheme) || scheme.len == 0;
156   if (scheme_is_empty) {
157     if (url[begin] == '#') {
158       // |url| is a bare fragment (e.g. "#foo"). This can be resolved against
159       // any base. Fall-through.
160     } else if (!is_base_hierarchical) {
161       // Don't allow relative URLs if the base scheme doesn't support it.
162       return false;
163     }
164 
165     *relative_component = MakeRange(begin, url_len);
166     *is_relative = true;
167     return true;
168   }
169 
170   // If the scheme isn't valid, then it's relative.
171   if (!IsValidScheme(url, scheme)) {
172     if (url[begin] == '#') {
173       // |url| is a bare fragment (e.g. "#foo:bar"). This can be resolved
174       // against any base. Fall-through.
175     } else if (!is_base_hierarchical) {
176       // Don't allow relative URLs if the base scheme doesn't support it.
177       return false;
178     }
179     *relative_component = MakeRange(begin, url_len);
180     *is_relative = true;
181     return true;
182   }
183 
184   // If base scheme is not standard, or the schemes are different, we can't
185   // count it as relative.
186   //
187   // URL Standard: https://url.spec.whatwg.org/#scheme-state
188   //
189   // scheme state:
190   // > 2.6. Otherwise, if url is special, base is non-null, and base’s scheme is
191   // >      url’s scheme:
192   if ((IsUsingStandardCompliantNonSpecialSchemeURLParsing() &&
193        !IsStandard(base, base_parsed.scheme)) ||
194       !AreSchemesEqual(base, base_parsed.scheme, url, scheme)) {
195     return true;
196   }
197 
198   // When the scheme that they both share is not hierarchical, treat the
199   // incoming scheme as absolute (this way with the base of "data:foo",
200   // "data:bar" will be reported as absolute.
201   if (!is_base_hierarchical)
202     return true;
203 
204   int colon_offset = scheme.end();
205 
206   // If it's a filesystem URL, the only valid way to make it relative is not to
207   // supply a scheme. There's no equivalent to e.g. http:index.html.
208   if (CompareSchemeComponent(url, scheme, kFileSystemScheme))
209     return true;
210 
211   // ExtractScheme guarantees that the colon immediately follows what it
212   // considers to be the scheme. CountConsecutiveSlashes will handle the
213   // case where the begin offset is the end of the input.
214   int num_slashes = CountConsecutiveSlashes(url, colon_offset + 1, url_len);
215 
216   if (num_slashes == 0 || num_slashes == 1) {
217     // No slashes means it's a relative path like "http:foo.html". One slash
218     // is an absolute path. "http:/home/foo.html"
219     *is_relative = true;
220     *relative_component = MakeRange(colon_offset + 1, url_len);
221     return true;
222   }
223 
224   // Two or more slashes after the scheme we treat as absolute.
225   return true;
226 }
227 
228 // Copies all characters in the range [begin, end) of |spec| to the output,
229 // up until and including the last slash. There should be a slash in the
230 // range, if not, nothing will be copied.
231 //
232 // For stardard URLs the input should be canonical, but when resolving relative
233 // URLs on a non-standard base (like "data:") the input can be anything.
CopyToLastSlash(const char * spec,int begin,int end,CanonOutput * output)234 void CopyToLastSlash(const char* spec,
235                      int begin,
236                      int end,
237                      CanonOutput* output) {
238   // Find the last slash.
239   int last_slash = -1;
240   for (int i = end - 1; i >= begin; i--) {
241     if (spec[i] == '/' || spec[i] == '\\') {
242       last_slash = i;
243       break;
244     }
245   }
246   if (last_slash < 0)
247     return;  // No slash.
248 
249   // Copy.
250   for (int i = begin; i <= last_slash; i++)
251     output->push_back(spec[i]);
252 }
253 
254 // Copies a single component from the source to the output. This is used
255 // when resolving relative URLs and a given component is unchanged. Since the
256 // source should already be canonical, we don't have to do anything special,
257 // and the input is ASCII.
CopyOneComponent(const char * source,const Component & source_component,CanonOutput * output,Component * output_component)258 void CopyOneComponent(const char* source,
259                       const Component& source_component,
260                       CanonOutput* output,
261                       Component* output_component) {
262   if (!source_component.is_valid()) {
263     // This component is not present.
264     *output_component = Component();
265     return;
266   }
267 
268   output_component->begin = output->length();
269   int source_end = source_component.end();
270   for (int i = source_component.begin; i < source_end; i++)
271     output->push_back(source[i]);
272   output_component->len = output->length() - output_component->begin;
273 }
274 
275 #ifdef WIN32
276 
277 // Called on Windows when the base URL is a file URL, this will copy the "C:"
278 // to the output, if there is a drive letter and if that drive letter is not
279 // being overridden by the relative URL. Otherwise, do nothing.
280 //
281 // It will return the index of the beginning of the next character in the
282 // base to be processed: if there is a "C:", the slash after it, or if
283 // there is no drive letter, the slash at the beginning of the path, or
284 // the end of the base. This can be used as the starting offset for further
285 // path processing.
286 template<typename CHAR>
CopyBaseDriveSpecIfNecessary(const char * base_url,int base_path_begin,int base_path_end,const CHAR * relative_url,int path_start,int relative_url_len,CanonOutput * output)287 int CopyBaseDriveSpecIfNecessary(const char* base_url,
288                                  int base_path_begin,
289                                  int base_path_end,
290                                  const CHAR* relative_url,
291                                  int path_start,
292                                  int relative_url_len,
293                                  CanonOutput* output) {
294   if (base_path_begin >= base_path_end)
295     return base_path_begin;  // No path.
296 
297   // If the relative begins with a drive spec, don't do anything. The existing
298   // drive spec in the base will be replaced.
299   if (DoesBeginWindowsDriveSpec(relative_url, path_start, relative_url_len)) {
300     return base_path_begin;  // Relative URL path is "C:/foo"
301   }
302 
303   // The path should begin with a slash (as all canonical paths do). We check
304   // if it is followed by a drive letter and copy it.
305   if (DoesBeginSlashWindowsDriveSpec(base_url,
306                                      base_path_begin,
307                                      base_path_end)) {
308     // Copy the two-character drive spec to the output. It will now look like
309     // "file:///C:" so the rest of it can be treated like a standard path.
310     output->push_back('/');
311     output->push_back(base_url[base_path_begin + 1]);
312     output->push_back(base_url[base_path_begin + 2]);
313     return base_path_begin + 3;
314   }
315 
316   return base_path_begin;
317 }
318 
319 #endif  // WIN32
320 
321 // A subroutine of DoResolveRelativeURL, this resolves the URL knowning that
322 // the input is a relative path or less (query or ref).
323 template <typename CHAR>
DoResolveRelativePath(const char * base_url,const Parsed & base_parsed,bool base_is_file,const CHAR * relative_url,const Component & relative_component,CharsetConverter * query_converter,CanonMode canon_mode,CanonOutput * output,Parsed * out_parsed)324 bool DoResolveRelativePath(const char* base_url,
325                            const Parsed& base_parsed,
326                            bool base_is_file,
327                            const CHAR* relative_url,
328                            const Component& relative_component,
329                            CharsetConverter* query_converter,
330                            CanonMode canon_mode,
331                            CanonOutput* output,
332                            Parsed* out_parsed) {
333   bool success = true;
334 
335   // We know the authority section didn't change, copy it to the output. We
336   // also know we have a path so can copy up to there.
337   Component path, query, ref;
338   ParsePathInternal(relative_url, relative_component, &path, &query, &ref);
339 
340   // Canonical URLs always have a path, so we can use that offset. Reserve
341   // enough room for the base URL, the new path, and some extra bytes for
342   // possible escaped characters.
343   output->ReserveSizeIfNeeded(base_parsed.path.begin +
344                               std::max({path.end(), query.end(), ref.end()}));
345 
346   // Append a base URL up to the beginning of base URL's path.
347   if (base_parsed.path.is_empty()) {
348     // A non-special URL may have an empty path (e.g. "git://host"). In these
349     // cases, attempting to use `base_parsed.path` is invalid.
350     output->Append(base_url, base_parsed.Length());
351   } else if (url::IsUsingStandardCompliantNonSpecialSchemeURLParsing() &&
352              !base_parsed.host.is_valid() &&
353              // Exclude a file URL and an URL with an inner-path because we are
354              // interested in only non-special URLs here.
355              //
356              // If we don't exclude a file URL here, for example, `new
357              // URL("test", "file:///tmp").href` will result in
358              // "file:/tmp/mock/test" instead of "file:///tmp/mock/test".
359              !base_is_file && !base_parsed.inner_parsed()) {
360     // The URL is a path-only non-special URL. e.g. "git:/path".
361     //
362     // In this case, we can't use `base_parsed.path.begin` because it may append
363     // "/." wrongly if the URL is, for example, "git:/.//a", where
364     // `base_parsed.path` represents "//a", instead of "/.//a". We want to
365     // append "git:", instead of "git:/.".
366     //
367     // Fortunately, we can use `base_parsed.scheme.end()` here because we don't
368     // need to append a user, a password, a host, nor a port when a host is
369     // invalid.
370     output->Append(base_url, base_parsed.scheme.end());
371     output->Append(":");
372   } else {
373     output->Append(base_url, base_parsed.path.begin);
374   }
375 
376   if (path.is_nonempty()) {
377     // The path is replaced or modified.
378     int true_path_begin = output->length();
379 
380     // For file: URLs on Windows, we don't want to treat the drive letter and
381     // colon as part of the path for relative file resolution when the
382     // incoming URL does not provide a drive spec. We save the true path
383     // beginning so we can fix it up after we are done.
384     int base_path_begin = base_parsed.path.begin;
385 #ifdef WIN32
386     if (base_is_file) {
387       base_path_begin = CopyBaseDriveSpecIfNecessary(
388           base_url, base_parsed.path.begin, base_parsed.path.end(),
389           relative_url, relative_component.begin, relative_component.end(),
390           output);
391       // Now the output looks like either "file://" or "file:///C:"
392       // and we can start appending the rest of the path. |base_path_begin|
393       // points to the character in the base that comes next.
394     }
395 #endif  // WIN32
396 
397     if (IsSlashOrBackslash(relative_url[path.begin])) {
398       // Easy case: the path is an absolute path on the server, so we can
399       // just replace everything from the path on with the new versions.
400       // Since the input should be canonical hierarchical URL, we should
401       // always have a path.
402       success &= CanonicalizePath(relative_url, path,
403                                   output, &out_parsed->path);
404     } else {
405       // Relative path, replace the query, and reference. We take the
406       // original path with the file part stripped, and append the new path.
407       // The canonicalizer will take care of resolving ".." and "."
408       size_t path_begin = output->length();
409 
410       if (base_parsed.path.is_empty() && !path.is_empty()) {
411         // Ensure a leading "/" is present before appending a non-empty relative
412         // path when the base URL's path is empty, as can occur with non-special
413         // URLs. This prevents incorrect path concatenation, such as resolving
414         // "path" based on "git://host" resulting in "git://hostpath" instead of
415         // the intended "git://host/path".
416         output->push_back('/');
417       }
418 
419       CopyToLastSlash(base_url, base_path_begin, base_parsed.path.end(),
420                       output);
421       success &= CanonicalizePartialPathInternal(relative_url, path, path_begin,
422                                                  canon_mode, output);
423       out_parsed->path = MakeRange(path_begin, output->length());
424 
425       // Copy the rest of the stuff after the path from the relative path.
426     }
427 
428     // To avoid path being treated as the host, prepend "/." to the path".
429     //
430     // Example:
431     //
432     // > const url = new URL("/.//path", "git:/");
433     // > url.href
434     // => The result should be "git:/.//path", instead of "git://path".
435     if (IsUsingStandardCompliantNonSpecialSchemeURLParsing() &&
436         !base_parsed.host.is_valid() && out_parsed->path.is_valid() &&
437         out_parsed->path.as_string_view_on(output->view().data())
438             .starts_with("//")) {
439       size_t prior_output_length = output->length();
440       output->Insert(out_parsed->path.begin, "/.");
441       // Adjust path.
442       out_parsed->path.begin += output->length() - prior_output_length;
443       true_path_begin = out_parsed->path.begin;
444     }
445     // Finish with the query and reference part (these can't fail).
446     CanonicalizeQuery(relative_url, query, query_converter,
447                       output, &out_parsed->query);
448     CanonicalizeRef(relative_url, ref, output, &out_parsed->ref);
449 
450     // Fix the path beginning to add back the "C:" we may have written above.
451     out_parsed->path = MakeRange(true_path_begin, out_parsed->path.end());
452     return success;
453   }
454 
455   // If we get here, the path is unchanged: copy to output.
456   CopyOneComponent(base_url, base_parsed.path, output, &out_parsed->path);
457 
458   if (query.is_valid()) {
459     // Just the query specified, replace the query and reference (ignore
460     // failures for refs)
461     CanonicalizeQuery(relative_url, query, query_converter,
462                       output, &out_parsed->query);
463     CanonicalizeRef(relative_url, ref, output, &out_parsed->ref);
464     return success;
465   }
466 
467   // If we get here, the query is unchanged: copy to output. Note that the
468   // range of the query parameter doesn't include the question mark, so we
469   // have to add it manually if there is a component.
470   if (base_parsed.query.is_valid())
471     output->push_back('?');
472   CopyOneComponent(base_url, base_parsed.query, output, &out_parsed->query);
473 
474   if (ref.is_valid()) {
475     // Just the reference specified: replace it (ignoring failures).
476     CanonicalizeRef(relative_url, ref, output, &out_parsed->ref);
477     return success;
478   }
479 
480   // We should always have something to do in this function, the caller checks
481   // that some component is being replaced.
482   DCHECK(false) << "Not reached";
483   return success;
484 }
485 
486 // Resolves a relative URL that contains a host. Typically, these will
487 // be of the form "//www.google.com/foo/bar?baz#ref" and the only thing which
488 // should be kept from the original URL is the scheme.
489 template<typename CHAR>
DoResolveRelativeHost(const char * base_url,const Parsed & base_parsed,const CHAR * relative_url,const Component & relative_component,CharsetConverter * query_converter,CanonOutput * output,Parsed * out_parsed)490 bool DoResolveRelativeHost(const char* base_url,
491                            const Parsed& base_parsed,
492                            const CHAR* relative_url,
493                            const Component& relative_component,
494                            CharsetConverter* query_converter,
495                            CanonOutput* output,
496                            Parsed* out_parsed) {
497   SchemeType scheme_type = SCHEME_WITH_HOST_PORT_AND_USER_INFORMATION;
498   const bool is_standard_scheme =
499       GetStandardSchemeType(base_url, base_parsed.scheme, &scheme_type);
500 
501   // Parse the relative URL, just like we would for anything following a
502   // scheme.
503   Parsed relative_parsed;  // Everything but the scheme is valid.
504 
505   if (IsUsingStandardCompliantNonSpecialSchemeURLParsing() &&
506       !is_standard_scheme) {
507     ParseAfterNonSpecialScheme(relative_url, relative_component.end(),
508                                relative_component.begin, &relative_parsed);
509   } else {
510     ParseAfterSpecialScheme(relative_url, relative_component.end(),
511                             relative_component.begin, &relative_parsed);
512   }
513 
514   // Now we can just use the replacement function to replace all the necessary
515   // parts of the old URL with the new one.
516   Replacements<CHAR> replacements;
517   replacements.SetUsername(relative_url, relative_parsed.username);
518   replacements.SetPassword(relative_url, relative_parsed.password);
519   replacements.SetHost(relative_url, relative_parsed.host);
520   replacements.SetPort(relative_url, relative_parsed.port);
521   replacements.SetPath(relative_url, relative_parsed.path);
522   replacements.SetQuery(relative_url, relative_parsed.query);
523   replacements.SetRef(relative_url, relative_parsed.ref);
524 
525   // Length() does not include the old scheme, so make sure to add it from the
526   // base URL.
527   output->ReserveSizeIfNeeded(
528       replacements.components().Length() +
529       base_parsed.CountCharactersBefore(Parsed::USERNAME, false));
530   if (!is_standard_scheme) {
531     if (IsUsingStandardCompliantNonSpecialSchemeURLParsing()) {
532       return ReplaceNonSpecialURL(base_url, base_parsed, replacements,
533                                   query_converter, *output, *out_parsed);
534     }
535     // A path with an authority section gets canonicalized under standard URL
536     // rules, even though the base was not known to be standard.
537     scheme_type = SCHEME_WITH_HOST_PORT_AND_USER_INFORMATION;
538   }
539   return ReplaceStandardURL(base_url, base_parsed, replacements, scheme_type,
540                             query_converter, output, out_parsed);
541 }
542 
543 // Resolves a relative URL that happens to be an absolute file path. Examples
544 // include: "//hostname/path", "/c:/foo", and "//hostname/c:/foo".
545 template <typename CharT>
DoResolveAbsoluteFile(const CharT * relative_url,const Component & relative_component,CharsetConverter * query_converter,CanonOutput * output,Parsed * out_parsed)546 bool DoResolveAbsoluteFile(const CharT* relative_url,
547                            const Component& relative_component,
548                            CharsetConverter* query_converter,
549                            CanonOutput* output,
550                            Parsed* out_parsed) {
551   // Parse the file URL. The file URL parsing function uses the same logic
552   // as we do for determining if the file is absolute, in which case it will
553   // not bother to look for a scheme.
554   return CanonicalizeFileURL(
555       &relative_url[relative_component.begin], relative_component.len,
556       ParseFileURL(std::basic_string_view(
557           &relative_url[relative_component.begin], relative_component.len)),
558       query_converter, output, out_parsed);
559 }
560 
561 // TODO(brettw) treat two slashes as root like Mozilla for FTP?
562 template<typename CHAR>
DoResolveRelativeURL(const char * base_url,const Parsed & base_parsed,bool base_is_file,const CHAR * relative_url,const Component & relative_component,CharsetConverter * query_converter,CanonOutput * output,Parsed * out_parsed)563 bool DoResolveRelativeURL(const char* base_url,
564                           const Parsed& base_parsed,
565                           bool base_is_file,
566                           const CHAR* relative_url,
567                           const Component& relative_component,
568                           CharsetConverter* query_converter,
569                           CanonOutput* output,
570                           Parsed* out_parsed) {
571   // |base_parsed| is the starting point for our output. Since we may have
572   // removed whitespace from |relative_url| before entering this method, we'll
573   // carry over the |potentially_dangling_markup| flag.
574   bool potentially_dangling_markup = out_parsed->potentially_dangling_markup;
575   *out_parsed = base_parsed;
576   if (potentially_dangling_markup)
577     out_parsed->potentially_dangling_markup = true;
578 
579   // A flag-dependent condition check is necessary here because non-special URLs
580   // may have an empty path if StandardCompliantNonSpecialSchemeURLParsing flag
581   // is enabled.
582   //
583   // TODO(crbug.com/40063064): Remove the following comment when we enable the
584   // flag. The comment makes sense only when the flag is disabled.
585   //
586   // > Sanity check: the input should have a host or we'll break badly below.
587   // > We can only resolve relative URLs with base URLs that have hosts and
588   // > paths (even the default path of "/" is OK).
589   // >
590   // > We allow hosts with no length so we can handle file URLs, for example.
591   if (IsUsingStandardCompliantNonSpecialSchemeURLParsing()
592           ? base_parsed.scheme.is_empty()
593           : base_parsed.path.is_empty()) {
594     // On error, return the input (resolving a relative URL on a
595     // non-relative base = the base).
596     int base_len = base_parsed.Length();
597     for (int i = 0; i < base_len; i++) {
598       output->push_back(base_url[i]);
599     }
600     return false;
601   }
602 
603   if (relative_component.is_empty()) {
604     // Empty relative URL, leave unchanged, only removing the ref component.
605     int base_len = base_parsed.Length();
606     base_len -= base_parsed.ref.len + 1;
607     out_parsed->ref.reset();
608     output->Append(base_url, base_len);
609     return true;
610   }
611 
612   int num_slashes = CountConsecutiveSlashes(
613       relative_url, relative_component.begin, relative_component.end());
614 
615 #ifdef WIN32
616   // On Windows, two slashes for a file path (regardless of which direction
617   // they are) means that it's UNC. Two backslashes on any base scheme mean
618   // that it's an absolute UNC path (we use the base_is_file flag to control
619   // how strict the UNC finder is).
620   //
621   // We also allow Windows absolute drive specs on any scheme (for example
622   // "c:\foo") like IE does. There must be no preceding slashes in this
623   // case (we reject anything like "/c:/foo") because that should be treated
624   // as a path. For file URLs, we allow any number of slashes since that would
625   // be setting the path.
626   //
627   // This assumes the absolute path resolver handles absolute URLs like this
628   // properly. DoCanonicalize does this.
629   int after_slashes = relative_component.begin + num_slashes;
630   if (DoesBeginUNCPath(relative_url, relative_component.begin,
631                        relative_component.end(), !base_is_file) ||
632       ((num_slashes == 0 || base_is_file) &&
633        DoesBeginWindowsDriveSpec(
634            relative_url, after_slashes, relative_component.end()))) {
635     return DoResolveAbsoluteFile(relative_url, relative_component,
636                                  query_converter, output, out_parsed);
637   }
638 #else
639   // Other platforms need explicit handling for file: URLs with multiple
640   // slashes because the generic scheme parsing always extracts a host, but a
641   // file: URL only has a host if it has exactly 2 slashes. Even if it does
642   // have a host, we want to use the special host detection logic for file
643   // URLs provided by DoResolveAbsoluteFile(), as opposed to the generic host
644   // detection logic, for consistency with parsing file URLs from scratch.
645   if (base_is_file && num_slashes >= 2) {
646     return DoResolveAbsoluteFile(relative_url, relative_component,
647                                  query_converter, output, out_parsed);
648   }
649 #endif
650 
651   // Any other double-slashes mean that this is relative to the scheme.
652   if (num_slashes >= 2) {
653     return DoResolveRelativeHost(base_url, base_parsed,
654                                  relative_url, relative_component,
655                                  query_converter, output, out_parsed);
656   }
657 
658   // When we get here, we know that the relative URL is on the same host.
659   return DoResolveRelativePath(
660       base_url, base_parsed, base_is_file, relative_url, relative_component,
661       query_converter,
662       // TODO(crbug.com/40063064): Support Non-special URLs
663       CanonMode::kSpecialURL, output, out_parsed);
664 }
665 
666 }  // namespace
667 
IsRelativeURL(const char * base,const Parsed & base_parsed,const char * fragment,int fragment_len,bool is_base_hierarchical,bool * is_relative,Component * relative_component)668 bool IsRelativeURL(const char* base,
669                    const Parsed& base_parsed,
670                    const char* fragment,
671                    int fragment_len,
672                    bool is_base_hierarchical,
673                    bool* is_relative,
674                    Component* relative_component) {
675   return DoIsRelativeURL<char>(
676       base, base_parsed, fragment, fragment_len, is_base_hierarchical,
677       is_relative, relative_component);
678 }
679 
IsRelativeURL(const char * base,const Parsed & base_parsed,const char16_t * fragment,int fragment_len,bool is_base_hierarchical,bool * is_relative,Component * relative_component)680 bool IsRelativeURL(const char* base,
681                    const Parsed& base_parsed,
682                    const char16_t* fragment,
683                    int fragment_len,
684                    bool is_base_hierarchical,
685                    bool* is_relative,
686                    Component* relative_component) {
687   return DoIsRelativeURL<char16_t>(base, base_parsed, fragment, fragment_len,
688                                    is_base_hierarchical, is_relative,
689                                    relative_component);
690 }
691 
ResolveRelativeURL(const char * base_url,const Parsed & base_parsed,bool base_is_file,const char * relative_url,const Component & relative_component,CharsetConverter * query_converter,CanonOutput * output,Parsed * out_parsed)692 bool ResolveRelativeURL(const char* base_url,
693                         const Parsed& base_parsed,
694                         bool base_is_file,
695                         const char* relative_url,
696                         const Component& relative_component,
697                         CharsetConverter* query_converter,
698                         CanonOutput* output,
699                         Parsed* out_parsed) {
700   return DoResolveRelativeURL<char>(
701       base_url, base_parsed, base_is_file, relative_url,
702       relative_component, query_converter, output, out_parsed);
703 }
704 
ResolveRelativeURL(const char * base_url,const Parsed & base_parsed,bool base_is_file,const char16_t * relative_url,const Component & relative_component,CharsetConverter * query_converter,CanonOutput * output,Parsed * out_parsed)705 bool ResolveRelativeURL(const char* base_url,
706                         const Parsed& base_parsed,
707                         bool base_is_file,
708                         const char16_t* relative_url,
709                         const Component& relative_component,
710                         CharsetConverter* query_converter,
711                         CanonOutput* output,
712                         Parsed* out_parsed) {
713   return DoResolveRelativeURL<char16_t>(base_url, base_parsed, base_is_file,
714                                         relative_url, relative_component,
715                                         query_converter, output, out_parsed);
716 }
717 
718 }  // namespace url
719