1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "chrome/browser/search_engines/template_url_parser.h"
6
7#include <algorithm>
8#include <map>
9#include <vector>
10
11#include "base/logging.h"
12#include "base/memory/scoped_ptr.h"
13#include "base/string_number_conversions.h"
14#include "base/string_util.h"
15#include "base/utf_string_conversions.h"
16#include "chrome/browser/search_engines/template_url.h"
17#include "chrome/common/url_constants.h"
18#include "googleurl/src/gurl.h"
19#include "libxml/parser.h"
20#include "libxml/xmlwriter.h"
21
22namespace {
23
24//
25// NOTE: libxml uses the UTF-8 encoding. As 0-127 of UTF-8 corresponds
26// to that of char, the following names are all in terms of char. This avoids
27// having to convert to wide, then do comparisons
28
29// Defines for element names of the OSD document:
30static const char kURLElement[] = "Url";
31static const char kParamElement[] = "Param";
32static const char kShortNameElement[] = "ShortName";
33static const char kDescriptionElement[] = "Description";
34static const char kImageElement[] = "Image";
35static const char kOpenSearchDescriptionElement[] = "OpenSearchDescription";
36static const char kFirefoxSearchDescriptionElement[] = "SearchPlugin";
37static const char kLanguageElement[] = "Language";
38static const char kInputEncodingElement[] = "InputEncoding";
39
40// Various XML attributes used.
41static const char kURLTypeAttribute[] = "type";
42static const char kURLTemplateAttribute[] = "template";
43static const char kImageTypeAttribute[] = "type";
44static const char kImageWidthAttribute[] = "width";
45static const char kImageHeightAttribute[] = "height";
46static const char kURLIndexOffsetAttribute[] = "indexOffset";
47static const char kURLPageOffsetAttribute[] = "pageOffset";
48static const char kParamNameAttribute[] = "name";
49static const char kParamValueAttribute[] = "value";
50static const char kParamMethodAttribute[] = "method";
51
52// Mime type for search results.
53static const char kHTMLType[] = "text/html";
54
55// Mime type for as you type suggestions.
56static const char kSuggestionType[] = "application/x-suggestions+json";
57
58// Namespace identifier.
59static const char kOSDNS[] = "xmlns";
60
61// The namespace for documents we understand.
62static const char kNameSpace[] = "http://a9.com/-/spec/opensearch/1.1/";
63
64// Removes the namespace from the specified |name|, ex: os:Url -> Url.
65static void PruneNamespace(std::string* name) {
66  size_t index = name->find_first_of(":");
67  if (index != std::string::npos)
68    name->erase(0, index + 1);
69}
70
71//
72// To minimize memory overhead while parsing, a SAX style parser is used.
73// ParsingContext is used to maintain the state we're in the document
74// while parsing.
75class ParsingContext {
76 public:
77  // Enum of the known element types.
78  enum ElementType {
79    UNKNOWN,
80    OPEN_SEARCH_DESCRIPTION,
81    URL,
82    PARAM,
83    SHORT_NAME,
84    DESCRIPTION,
85    IMAGE,
86    LANGUAGE,
87    INPUT_ENCODING,
88  };
89
90  enum Method {
91    GET,
92    POST
93  };
94
95  // Key/value of a Param node.
96  typedef std::pair<std::string, std::string> Param;
97
98  ParsingContext(TemplateURLParser::ParameterFilter* parameter_filter,
99                 TemplateURL* url)
100      : url_(url),
101        parameter_filter_(parameter_filter),
102        method_(GET),
103        suggestion_method_(GET),
104        is_suggest_url_(false),
105        derive_image_from_url_(false) {
106    if (kElementNameToElementTypeMap == NULL)
107      InitMapping();
108  }
109
110  // Invoked when an element starts.
111  void PushElement(const std::string& element) {
112    ElementType type;
113    if (kElementNameToElementTypeMap->find(element) ==
114        kElementNameToElementTypeMap->end()) {
115      type = UNKNOWN;
116    } else {
117      type = (*kElementNameToElementTypeMap)[element];
118    }
119    elements_.push_back(type);
120  }
121
122  void PopElement() {
123    elements_.pop_back();
124  }
125
126  // Returns the current ElementType.
127  ElementType GetKnownType() {
128    if (elements_.size() == 2 && elements_[0] == OPEN_SEARCH_DESCRIPTION)
129      return elements_[1];
130
131    // We only expect PARAM nodes under the Url node
132    if (elements_.size() == 3 && elements_[0] == OPEN_SEARCH_DESCRIPTION &&
133        elements_[1] == URL && elements_[2] == PARAM)
134      return PARAM;
135
136    return UNKNOWN;
137  }
138
139  TemplateURL* template_url() { return url_; }
140
141  void AddImageRef(const std::string& type, int width, int height) {
142    if (width > 0 && height > 0)
143      current_image_.reset(new TemplateURL::ImageRef(type, width, height));
144  }
145
146  void EndImage() {
147    current_image_.reset();
148  }
149
150  void SetImageURL(const GURL& url) {
151    if (current_image_.get()) {
152      current_image_->url = url;
153      url_->add_image_ref(*current_image_);
154      current_image_.reset();
155    }
156  }
157
158  void ResetString() {
159    string_.clear();
160  }
161
162  void AppendString(const string16& string) {
163    string_ += string;
164  }
165
166  const string16& GetString() {
167    return string_;
168  }
169
170  void ResetExtraParams() {
171    extra_params_.clear();
172  }
173
174  void AddExtraParams(const std::string& key, const std::string& value) {
175    if (parameter_filter_ && !parameter_filter_->KeepParameter(key, value))
176      return;
177    extra_params_.push_back(Param(key, value));
178  }
179
180  const std::vector<Param>& extra_params() const { return extra_params_; }
181
182  void set_is_suggestion(bool value) { is_suggest_url_ = value; }
183  bool is_suggestion() const { return is_suggest_url_; }
184
185  TemplateURLParser::ParameterFilter* parameter_filter() const {
186    return parameter_filter_;
187  }
188
189  void set_derive_image_from_url(bool derive_image_from_url) {
190    derive_image_from_url_ = derive_image_from_url;
191  }
192
193  void set_method(Method method) { method_ = method; }
194  Method method() { return method_; }
195
196  void set_suggestion_method(Method method) { suggestion_method_ = method; }
197  Method suggestion_method() { return suggestion_method_; }
198
199  // Builds the image URL from the Template search URL if no image URL has been
200  // set.
201  void DeriveImageFromURL() {
202    if (derive_image_from_url_ &&
203        url_->GetFaviconURL().is_empty() && url_->url()) {
204      GURL url(url_->url()->url());  // More url's please...
205      url_->SetFaviconURL(TemplateURL::GenerateFaviconURL(url));
206    }
207  }
208
209 private:
210  static void InitMapping() {
211    kElementNameToElementTypeMap = new std::map<std::string, ElementType>;
212    (*kElementNameToElementTypeMap)[kURLElement] = URL;
213    (*kElementNameToElementTypeMap)[kParamElement] = PARAM;
214    (*kElementNameToElementTypeMap)[kShortNameElement] = SHORT_NAME;
215    (*kElementNameToElementTypeMap)[kDescriptionElement] = DESCRIPTION;
216    (*kElementNameToElementTypeMap)[kImageElement] = IMAGE;
217    (*kElementNameToElementTypeMap)[kOpenSearchDescriptionElement] =
218        OPEN_SEARCH_DESCRIPTION;
219    (*kElementNameToElementTypeMap)[kFirefoxSearchDescriptionElement] =
220        OPEN_SEARCH_DESCRIPTION;
221    (*kElementNameToElementTypeMap)[kLanguageElement] =
222        LANGUAGE;
223    (*kElementNameToElementTypeMap)[kInputEncodingElement] =
224        INPUT_ENCODING;
225  }
226
227  // Key is UTF8 encoded.
228  static std::map<std::string, ElementType>* kElementNameToElementTypeMap;
229  // TemplateURL supplied to Read method. It's owned by the caller, so we
230  // don't need to free it.
231  TemplateURL* url_;
232  std::vector<ElementType> elements_;
233  scoped_ptr<TemplateURL::ImageRef> current_image_;
234
235  // Character content for the current element.
236  string16 string_;
237
238  TemplateURLParser::ParameterFilter* parameter_filter_;
239
240  // The list of parameters parsed in the Param nodes of a Url node.
241  std::vector<Param> extra_params_;
242
243  // The HTTP methods used.
244  Method method_;
245  Method suggestion_method_;
246
247  // If true, we are currently parsing a suggest URL, otherwise it is an HTML
248  // search.  Note that we don't need a stack as Url nodes cannot be nested.
249  bool is_suggest_url_;
250
251  // Whether we should derive the image from the URL (when images are data
252  // URLs).
253  bool derive_image_from_url_;
254
255  DISALLOW_COPY_AND_ASSIGN(ParsingContext);
256};
257
258// static
259std::map<std::string, ParsingContext::ElementType>*
260    ParsingContext::kElementNameToElementTypeMap = NULL;
261
262string16 XMLCharToUTF16(const xmlChar* value, int length) {
263  return UTF8ToUTF16(std::string((const char*)value, length));
264}
265
266std::string XMLCharToString(const xmlChar* value) {
267  return std::string((const char*)value);
268}
269
270// Returns true if input_encoding contains a valid input encoding string. This
271// doesn't verify that we have a valid encoding for the string, just that the
272// string contains characters that constitute a valid input encoding.
273bool IsValidEncodingString(const std::string& input_encoding) {
274  if (input_encoding.empty())
275    return false;
276
277  if (!IsAsciiAlpha(input_encoding[0]))
278    return false;
279
280  for (size_t i = 1, max = input_encoding.size(); i < max; ++i) {
281    char c = input_encoding[i];
282    if (!IsAsciiAlpha(c) && !IsAsciiDigit(c) && c != '.' && c != '_' &&
283        c != '-') {
284      return false;
285    }
286  }
287  return true;
288}
289
290void ParseURL(const xmlChar** atts, ParsingContext* context) {
291  if (!atts)
292    return;
293
294  TemplateURL* turl = context->template_url();
295  const xmlChar** attributes = atts;
296  std::string template_url;
297  bool is_post = false;
298  bool is_html_url = false;
299  bool is_suggest_url = false;
300  int index_offset = 1;
301  int page_offset = 1;
302
303  while (*attributes) {
304    std::string name(XMLCharToString(*attributes));
305    const xmlChar* value = attributes[1];
306    if (name == kURLTypeAttribute) {
307      std::string type = XMLCharToString(value);
308      is_html_url = (type == kHTMLType);
309      is_suggest_url = (type == kSuggestionType);
310    } else if (name == kURLTemplateAttribute) {
311      template_url = XMLCharToString(value);
312    } else if (name == kURLIndexOffsetAttribute) {
313      base::StringToInt(XMLCharToString(value), &index_offset);
314      index_offset = std::max(1, index_offset);
315    } else if (name == kURLPageOffsetAttribute) {
316      base::StringToInt(XMLCharToString(value), &page_offset);
317      page_offset = std::max(1, page_offset);
318    } else if (name == kParamMethodAttribute) {
319      is_post = LowerCaseEqualsASCII(XMLCharToString(value), "post");
320    }
321    attributes += 2;
322  }
323  if (is_html_url) {
324    turl->SetURL(template_url, index_offset, page_offset);
325    context->set_is_suggestion(false);
326    if (is_post)
327      context->set_method(ParsingContext::POST);
328  } else if (is_suggest_url) {
329    turl->SetSuggestionsURL(template_url, index_offset, page_offset);
330    context->set_is_suggestion(true);
331    if (is_post)
332      context->set_suggestion_method(ParsingContext::POST);
333  }
334}
335
336void ParseImage(const xmlChar** atts, ParsingContext* context) {
337  if (!atts)
338    return;
339
340  const xmlChar** attributes = atts;
341  int width = 0;
342  int height = 0;
343  std::string type;
344  while (*attributes) {
345    std::string name(XMLCharToString(*attributes));
346    const xmlChar* value = attributes[1];
347    if (name == kImageTypeAttribute) {
348      type = XMLCharToString(value);
349    } else if (name == kImageWidthAttribute) {
350      base::StringToInt(XMLCharToString(value), &width);
351    } else if (name == kImageHeightAttribute) {
352      base::StringToInt(XMLCharToString(value), &height);
353    }
354    attributes += 2;
355  }
356  if (width > 0 && height > 0 && !type.empty()) {
357    // Valid Image URL.
358    context->AddImageRef(type, width, height);
359  }
360}
361
362void ParseParam(const xmlChar** atts, ParsingContext* context) {
363  if (!atts)
364    return;
365
366  const xmlChar** attributes = atts;
367  std::string key, value;
368  while (*attributes) {
369    std::string name(XMLCharToString(*attributes));
370    const xmlChar* val = attributes[1];
371    if (name == kParamNameAttribute) {
372      key = XMLCharToString(val);
373    } else if (name == kParamValueAttribute) {
374      value = XMLCharToString(val);
375    }
376    attributes += 2;
377  }
378  if (!key.empty())
379    context->AddExtraParams(key, value);
380}
381
382static void AppendParamToQuery(const std::string& key,
383                               const std::string& value,
384                               std::string* query) {
385  if (!query->empty())
386    query->append("&");
387  if (!key.empty()) {
388    query->append(key);
389    query->append("=");
390  }
391  query->append(value);
392}
393
394void ProcessURLParams(ParsingContext* context) {
395  TemplateURL* t_url = context->template_url();
396  const TemplateURLRef* t_url_ref =
397      context->is_suggestion() ? t_url->suggestions_url() :
398                                 t_url->url();
399  if (!t_url_ref)
400    return;
401
402  if (!context->parameter_filter() && context->extra_params().empty())
403    return;
404
405  GURL url(t_url_ref->url());
406  // If there is a parameter filter, parse the existing URL and remove any
407  // unwanted parameter.
408  TemplateURLParser::ParameterFilter* filter = context->parameter_filter();
409  std::string new_query;
410  bool modified = false;
411  if (filter) {
412    url_parse::Component query = url.parsed_for_possibly_invalid_spec().query;
413    url_parse::Component key, value;
414    const char* url_spec = url.spec().c_str();
415    while (url_parse::ExtractQueryKeyValue(url_spec, &query, &key, &value)) {
416      std::string key_str(url_spec, key.begin, key.len);
417      std::string value_str(url_spec, value.begin, value.len);
418      if (filter->KeepParameter(key_str, value_str)) {
419        AppendParamToQuery(key_str, value_str, &new_query);
420      } else {
421        modified = true;
422      }
423    }
424  }
425  if (!modified)
426    new_query = url.query();
427
428  // Add the extra parameters if any.
429  const std::vector<ParsingContext::Param>& params = context->extra_params();
430  if (!params.empty()) {
431    modified = true;
432    std::vector<ParsingContext::Param>::const_iterator iter;
433    for (iter = params.begin(); iter != params.end(); ++iter)
434      AppendParamToQuery(iter->first, iter->second, &new_query);
435  }
436
437  if (modified) {
438    GURL::Replacements repl;
439    repl.SetQueryStr(new_query);
440    url = url.ReplaceComponents(repl);
441    if (context->is_suggestion()) {
442      t_url->SetSuggestionsURL(url.spec(),
443                               t_url_ref->index_offset(),
444                               t_url_ref->page_offset());
445    } else {
446      t_url->SetURL(url.spec(),
447                    t_url_ref->index_offset(),
448                    t_url_ref->page_offset());
449    }
450  }
451}
452
453void StartElementImpl(void *ctx, const xmlChar *name, const xmlChar **atts) {
454  ParsingContext* context = reinterpret_cast<ParsingContext*>(ctx);
455  std::string node_name((const char*)name);
456  PruneNamespace(&node_name);
457  context->PushElement(node_name);
458  switch (context->GetKnownType()) {
459    case ParsingContext::URL:
460      context->ResetExtraParams();
461      ParseURL(atts, context);
462      break;
463    case ParsingContext::IMAGE:
464      ParseImage(atts, context);
465      break;
466    case ParsingContext::PARAM:
467      ParseParam(atts, context);
468      break;
469    default:
470      break;
471  }
472  context->ResetString();
473}
474
475void EndElementImpl(void *ctx, const xmlChar *name) {
476  ParsingContext* context = reinterpret_cast<ParsingContext*>(ctx);
477  switch (context->GetKnownType()) {
478    case ParsingContext::SHORT_NAME:
479      context->template_url()->set_short_name(context->GetString());
480      break;
481    case ParsingContext::DESCRIPTION:
482      context->template_url()->set_description(context->GetString());
483      break;
484    case ParsingContext::IMAGE: {
485      GURL image_url(UTF16ToUTF8(context->GetString()));
486      if (image_url.SchemeIs(chrome::kDataScheme)) {
487        // TODO (jcampan): bug 1169256: when dealing with data URL, we need to
488        // decode the data URL in the renderer. For now, we'll just point to the
489        // favicon from the URL.
490        context->set_derive_image_from_url(true);
491      } else {
492        context->SetImageURL(image_url);
493      }
494      context->EndImage();
495      break;
496    }
497    case ParsingContext::LANGUAGE:
498      context->template_url()->add_language(context->GetString());
499      break;
500    case ParsingContext::INPUT_ENCODING: {
501      std::string input_encoding = UTF16ToASCII(context->GetString());
502      if (IsValidEncodingString(input_encoding))
503        context->template_url()->add_input_encoding(input_encoding);
504      break;
505    }
506    case ParsingContext::URL:
507      ProcessURLParams(context);
508      break;
509    default:
510      break;
511  }
512  context->ResetString();
513  context->PopElement();
514}
515
516void CharactersImpl(void *ctx, const xmlChar *ch, int len) {
517  ParsingContext* context = reinterpret_cast<ParsingContext*>(ctx);
518  context->AppendString(XMLCharToUTF16(ch, len));
519}
520
521// Returns true if the ref is null, or the url wrapped by ref is
522// valid with a spec of http/https.
523bool IsHTTPRef(const TemplateURLRef* ref) {
524  if (ref == NULL)
525    return true;
526  GURL url(ref->url());
527  return (url.is_valid() && (url.SchemeIs(chrome::kHttpScheme) ||
528                             url.SchemeIs(chrome::kHttpsScheme)));
529}
530
531// Returns true if the TemplateURL is legal. A legal TemplateURL is one
532// where all URLs have a spec of http/https.
533bool IsLegal(TemplateURL* url) {
534  if (!IsHTTPRef(url->url()) || !IsHTTPRef(url->suggestions_url()))
535    return false;
536  // Make sure all the image refs are legal.
537  const std::vector<TemplateURL::ImageRef>& image_refs = url->image_refs();
538  for (size_t i = 0; i < image_refs.size(); i++) {
539    GURL image_url(image_refs[i].url);
540    if (!image_url.is_valid() ||
541        !(image_url.SchemeIs(chrome::kHttpScheme) ||
542          image_url.SchemeIs(chrome::kHttpsScheme))) {
543      return false;
544    }
545  }
546  return true;
547}
548
549}  // namespace
550
551// static
552bool TemplateURLParser::Parse(const unsigned char* data, size_t length,
553                              TemplateURLParser::ParameterFilter* param_filter,
554                              TemplateURL* url) {
555  DCHECK(url);
556  // xmlSubstituteEntitiesDefault(1) makes it so that &amp; isn't mapped to
557  // &#38; . Unfortunately xmlSubstituteEntitiesDefault effects global state.
558  // If this becomes problematic we'll need to provide our own entity
559  // type for &amp;, or strip out &#34; by hand after parsing.
560  int last_sub_entities_value = xmlSubstituteEntitiesDefault(1);
561  ParsingContext context(param_filter, url);
562  xmlSAXHandler sax_handler;
563  memset(&sax_handler, 0, sizeof(sax_handler));
564  sax_handler.startElement = &StartElementImpl;
565  sax_handler.endElement = &EndElementImpl;
566  sax_handler.characters = &CharactersImpl;
567  xmlSAXUserParseMemory(&sax_handler, &context,
568                        reinterpret_cast<const char*>(data),
569                        static_cast<int>(length));
570  xmlSubstituteEntitiesDefault(last_sub_entities_value);
571  // If the image was a data URL, use the favicon from the search URL instead.
572  // (see TODO inEndElementImpl()).
573  context.DeriveImageFromURL();
574
575  // TODO(jcampan): http://b/issue?id=1196285 we do not support search engines
576  //                that use POST yet.
577  if (context.method() == ParsingContext::POST)
578    return false;
579  if (context.suggestion_method() == ParsingContext::POST)
580    url->SetSuggestionsURL("", 0, 0);
581
582  if (!url->short_name().empty() && !url->description().empty()) {
583    // So far so good, make sure the urls are http.
584    return IsLegal(url);
585  }
586  return false;
587}
588