chrome/renderer/safe_browsing/threat_dom_details.cc

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chrome/renderer/safe_browsing/threat_dom_details.h"

#include <algorithm>
#include <map>
#include <unordered_set>

#include "base/compiler_specific.h"
#include "base/metrics/field_trial_params.h"
#include "base/strings/string_piece.h"
#include "base/strings/string_split.h"
#include "base/strings/stringprintf.h"
#include "components/safe_browsing/common/safebrowsing_messages.h"
#include "content/public/renderer/render_frame.h"
#include "third_party/WebKit/public/platform/WebString.h"
#include "third_party/WebKit/public/web/WebDocument.h"
#include "third_party/WebKit/public/web/WebElement.h"
#include "third_party/WebKit/public/web/WebElementCollection.h"
#include "third_party/WebKit/public/web/WebFrame.h"
#include "third_party/WebKit/public/web/WebLocalFrame.h"

namespace safe_browsing {

// A map for keeping track of the identity of DOM Elements, used to generate
// unique IDs for each element and lookup elements IDs by parent Element, to
// maintain proper parent/child relationships.
// They key is a WebNode from the DOM, which is basically a pointer so can be
// copied into the map when inserting new elements.
// The values are indices into the resource vector, and are used to retrieve IPC
// messages generated by ThreatDOMDetails.
using ElementToNodeMap = std::map<blink::WebNode, int>;

// This Feature specifies which non-resource HTML Elements to collect based on
// their tag and attributes. It's a single param containing a comma-separated
// list of pairs. For example: "tag1,id,tag1,height,tag2,foo" - this will
// collect elements with tag "tag1" that have attribute "id" or "height" set,
// and elements of tag "tag2" if they have attribute "foo" set. All tag names
// and attributes should be lower case.
const base::Feature kThreatDomDetailsTagAndAttributeFeature{
    "ThreatDomDetailsTagAttributes", base::FEATURE_DISABLED_BY_DEFAULT};

// The name of the param containing the tags and attributes list.
const char kTagAndAttributeParamName[] = "tag_attribute_csv";

namespace {

// Predicate used to search |tag_and_attributes_list_| by tag_name.
class TagNameIs {
 public:
  explicit TagNameIs(const std::string& tag) : tag_(tag) {}
  bool operator()(const TagAndAttributesItem& tag_and_attribute) {
    return tag_ == tag_and_attribute.tag_name;
  }

 private:
  std::string tag_;
};

void ParseTagAndAttributeParams(
    std::vector<TagAndAttributesItem>* tag_and_attributes_list) {
  DCHECK(tag_and_attributes_list);
  if (!base::FeatureList::IsEnabled(kThreatDomDetailsTagAndAttributeFeature)) {
    return;
  }
  tag_and_attributes_list->clear();
  const std::string& tag_attribute_csv_param =
      base::GetFieldTrialParamValueByFeature(
          kThreatDomDetailsTagAndAttributeFeature, kTagAndAttributeParamName);
  if (tag_attribute_csv_param.empty()) {
    return;
  }

  std::vector<std::string> split =
      base::SplitString(tag_attribute_csv_param, ",", base::TRIM_WHITESPACE,
                        base::SPLIT_WANT_NONEMPTY);
  // If we don't have the right number of pairs in the csv then don't bother
  // parsing further.
  if (split.size() % 2 != 0) {
    return;
  }
  for (size_t i = 0; i < split.size(); i += 2) {
    const std::string& tag_name = split[i];
    const std::string& attribute = split[i + 1];
    auto item_iter =
        std::find_if(tag_and_attributes_list->begin(),
                     tag_and_attributes_list->end(), TagNameIs(tag_name));
    if (item_iter == tag_and_attributes_list->end()) {
      TagAndAttributesItem item;
      item.tag_name = tag_name;
      item.attributes.push_back(attribute);
      tag_and_attributes_list->push_back(item);
    } else {
      item_iter->attributes.push_back(attribute);
    }
  }

  std::sort(tag_and_attributes_list->begin(), tag_and_attributes_list->end(),
            [](const TagAndAttributesItem& a, const TagAndAttributesItem& b) {
              return a.tag_name < b.tag_name;
            });
}

SafeBrowsingHostMsg_ThreatDOMDetails_Node* GetNodeForElement(
    const blink::WebNode& element,
    const safe_browsing::ElementToNodeMap& element_to_node_map,
    std::vector<SafeBrowsingHostMsg_ThreatDOMDetails_Node>* resources) {
  DCHECK(element_to_node_map.count(element) > 0);
  int resource_index = element_to_node_map.at(element);
  return &(resources->at(resource_index));
}

// Handler for the various HTML elements that we extract URLs from.
void HandleElement(
    const blink::WebElement& element,
    SafeBrowsingHostMsg_ThreatDOMDetails_Node* summary_node,
    std::vector<SafeBrowsingHostMsg_ThreatDOMDetails_Node>* resources,
    safe_browsing::ElementToNodeMap* element_to_node_map) {
  // Retrieve the link and resolve the link in case it's relative.
  blink::WebURL full_url =
      element.document().completeURL(element.getAttribute("src"));

  const GURL& child_url = GURL(full_url);
  if (!child_url.is_empty() && child_url.is_valid()) {
    summary_node->children.push_back(child_url);
  }

  SafeBrowsingHostMsg_ThreatDOMDetails_Node child_node;
  child_node.url = child_url;
  child_node.tag_name = element.tagName().utf8();
  child_node.parent = summary_node->url;

  // Update the ID mapping. First generate the ID for the current node.
  // Then, if its parent is available, set the current node's parent ID, and
  // also update the parent's children with the current node's ID.
  const int child_id = element_to_node_map->size() + 1;
  child_node.node_id = child_id;
  blink::WebNode cur_parent_element = element.parentNode();
  while (!cur_parent_element.isNull()) {
    if (element_to_node_map->count(cur_parent_element) > 0) {
      SafeBrowsingHostMsg_ThreatDOMDetails_Node* parent_node =
          GetNodeForElement(cur_parent_element, *element_to_node_map,
                            resources);
      child_node.parent_node_id = parent_node->node_id;
      parent_node->child_node_ids.push_back(child_id);

      // TODO(lpz): Consider also updating the URL-level parent/child mapping
      // here. Eg: child_node.parent=parent_node.url, and
      // parent_node.children.push_back(child_url).
      break;
    } else {
      // It's possible that the direct parent of this node wasn't handled, so it
      // isn't represented in |element_to_node_map|. Try walking up the
      // hierarchy to see if a parent further up was handled.
      cur_parent_element = cur_parent_element.parentNode();
    }
  }
  // Add the child node to the list of resources.
  resources->push_back(child_node);
  // .. and remember which index it was inserted at so we can look it up later.
  (*element_to_node_map)[element] = resources->size() - 1;
}

bool ShouldHandleElement(
    const blink::WebElement& element,
    const std::vector<TagAndAttributesItem>& tag_and_attributes_list) {
  // Resources with a SRC are always handled.
  if ((element.hasHTMLTagName("iframe") || element.hasHTMLTagName("frame") ||
       element.hasHTMLTagName("embed") || element.hasHTMLTagName("script")) &&
      element.hasAttribute("src")) {
    return true;
  }

  std::string tag_name_lower = base::ToLowerASCII(element.tagName().ascii());
  const auto& tag_attribute_iter =
      std::find_if(tag_and_attributes_list.begin(),
                   tag_and_attributes_list.end(), TagNameIs(tag_name_lower));
  if (tag_attribute_iter == tag_and_attributes_list.end()) {
    return false;
  }

  const std::vector<std::string>& valid_attributes =
      tag_attribute_iter->attributes;
  for (const std::string& attribute : valid_attributes) {
    if (element.hasAttribute(blink::WebString::fromASCII(attribute))) {
      return true;
    }
  }
  return false;
}
}  // namespace

TagAndAttributesItem::TagAndAttributesItem() {}
TagAndAttributesItem::TagAndAttributesItem(const TagAndAttributesItem& item)
    : tag_name(item.tag_name), attributes(item.attributes) {}
TagAndAttributesItem::~TagAndAttributesItem() {}

// An upper limit on the number of nodes we collect.
uint32_t ThreatDOMDetails::kMaxNodes = 500;

// static
ThreatDOMDetails* ThreatDOMDetails::Create(content::RenderFrame* render_frame) {
  // Private constructor and public static Create() method to facilitate
  // stubbing out this class for binary-size reduction purposes.
  return new ThreatDOMDetails(render_frame);
}

ThreatDOMDetails::ThreatDOMDetails(content::RenderFrame* render_frame)
    : content::RenderFrameObserver(render_frame) {
  ParseTagAndAttributeParams(&tag_and_attributes_list_);
}

ThreatDOMDetails::~ThreatDOMDetails() {}

bool ThreatDOMDetails::OnMessageReceived(const IPC::Message& message) {
  bool handled = true;
  IPC_BEGIN_MESSAGE_MAP(ThreatDOMDetails, message)
    IPC_MESSAGE_HANDLER(SafeBrowsingMsg_GetThreatDOMDetails,
                        OnGetThreatDOMDetails)
    IPC_MESSAGE_UNHANDLED(handled = false)
  IPC_END_MESSAGE_MAP()
  return handled;
}

void ThreatDOMDetails::OnGetThreatDOMDetails() {
  std::vector<SafeBrowsingHostMsg_ThreatDOMDetails_Node> resources;
  ExtractResources(&resources);
  // Notify the browser.
  Send(new SafeBrowsingHostMsg_ThreatDOMDetails(routing_id(), resources));
}

void ThreatDOMDetails::ExtractResources(
    std::vector<SafeBrowsingHostMsg_ThreatDOMDetails_Node>* resources) {
  blink::WebFrame* frame = render_frame()->GetWebFrame();
  if (!frame)
    return;
  SafeBrowsingHostMsg_ThreatDOMDetails_Node details_node;
  blink::WebDocument document = frame->document();
  details_node.url = GURL(document.url());
  if (document.isNull()) {
    // Nothing in this frame. Just report its URL.
    resources->push_back(details_node);
    return;
  }

  ElementToNodeMap element_to_node_map;
  blink::WebElementCollection elements = document.all();
  blink::WebElement element = elements.firstItem();
  for (; !element.isNull(); element = elements.nextItem()) {
    if (ShouldHandleElement(element, tag_and_attributes_list_)) {
      HandleElement(element, &details_node, resources, &element_to_node_map);
      if (resources->size() >= kMaxNodes) {
        // We have reached kMaxNodes, exit early.
        resources->push_back(details_node);
        return;
      }
    }
  }
  resources->push_back(details_node);
}

void ThreatDOMDetails::OnDestruct() {
  delete this;
}

}  // namespace safe_browsing