chrome/browser/supervised_user/supervised_user_url_filter.cc

// Copyright 2014 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/browser/supervised_user/supervised_user_url_filter.h"

#include <set>
#include <utility>

#include "base/containers/hash_tables.h"
#include "base/files/file_path.h"
#include "base/json/json_file_value_serializer.h"
#include "base/metrics/histogram.h"
#include "base/sha1.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "base/task_runner_util.h"
#include "base/threading/sequenced_worker_pool.h"
#include "chrome/browser/supervised_user/experimental/supervised_user_blacklist.h"
#include "components/policy/core/browser/url_blacklist_manager.h"
#include "components/url_fixer/url_fixer.h"
#include "components/url_matcher/url_matcher.h"
#include "content/public/browser/browser_thread.h"
#include "net/base/registry_controlled_domains/registry_controlled_domain.h"
#include "url/gurl.h"

using content::BrowserThread;
using net::registry_controlled_domains::EXCLUDE_UNKNOWN_REGISTRIES;
using net::registry_controlled_domains::EXCLUDE_PRIVATE_REGISTRIES;
using net::registry_controlled_domains::GetRegistryLength;
using policy::URLBlacklist;
using url_matcher::URLMatcher;
using url_matcher::URLMatcherConditionSet;

struct SupervisedUserURLFilter::Contents {
  URLMatcher url_matcher;
  std::map<URLMatcherConditionSet::ID, int> matcher_site_map;
  base::hash_multimap<std::string, int> hash_site_map;
  std::vector<SupervisedUserSiteList::Site> sites;
};

namespace {

// URL schemes not in this list (e.g., file:// and chrome://) will always be
// allowed.
const char* kFilteredSchemes[] = {
  "http",
  "https",
  "ftp",
  "gopher",
  "ws",
  "wss"
};


// This class encapsulates all the state that is required during construction of
// a new SupervisedUserURLFilter::Contents.
class FilterBuilder {
 public:
  FilterBuilder();
  ~FilterBuilder();

  // Adds a single URL pattern for the site identified by |site_id|.
  bool AddPattern(const std::string& pattern, int site_id);

  // Adds a single hostname SHA1 hash for the site identified by |site_id|.
  void AddHostnameHash(const std::string& hash, int site_id);

  // Adds all the sites in |site_list|, with URL patterns and hostname hashes.
  void AddSiteList(SupervisedUserSiteList* site_list);

  // Finalizes construction of the SupervisedUserURLFilter::Contents and returns
  // them. This method should be called before this object is destroyed.
  scoped_ptr<SupervisedUserURLFilter::Contents> Build();

 private:
  scoped_ptr<SupervisedUserURLFilter::Contents> contents_;
  URLMatcherConditionSet::Vector all_conditions_;
  URLMatcherConditionSet::ID matcher_id_;
};

FilterBuilder::FilterBuilder()
    : contents_(new SupervisedUserURLFilter::Contents()),
      matcher_id_(0) {}

FilterBuilder::~FilterBuilder() {
  DCHECK(!contents_.get());
}

bool FilterBuilder::AddPattern(const std::string& pattern, int site_id) {
  DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
  std::string scheme;
  std::string host;
  uint16 port;
  std::string path;
  std::string query;
  bool match_subdomains = true;
  URLBlacklist::SegmentURLCallback callback =
      static_cast<URLBlacklist::SegmentURLCallback>(url_fixer::SegmentURL);
  if (!URLBlacklist::FilterToComponents(
          callback, pattern,
          &scheme, &host, &match_subdomains, &port, &path, &query)) {
    LOG(ERROR) << "Invalid pattern " << pattern;
    return false;
  }

  scoped_refptr<URLMatcherConditionSet> condition_set =
      URLBlacklist::CreateConditionSet(
          &contents_->url_matcher, ++matcher_id_,
          scheme, host, match_subdomains, port, path, query, true);
  all_conditions_.push_back(condition_set);
  contents_->matcher_site_map[matcher_id_] = site_id;
  return true;
}

void FilterBuilder::AddHostnameHash(const std::string& hash, int site_id) {
  contents_->hash_site_map.insert(std::make_pair(StringToUpperASCII(hash),
                                                 site_id));
}

void FilterBuilder::AddSiteList(SupervisedUserSiteList* site_list) {
  std::vector<SupervisedUserSiteList::Site> sites;
  site_list->GetSites(&sites);
  int site_id = contents_->sites.size();
  for (const SupervisedUserSiteList::Site& site : sites) {
    contents_->sites.push_back(site);

    for (const std::string& pattern : site.patterns)
      AddPattern(pattern, site_id);

    for (const std::string& hash : site.hostname_hashes)
      AddHostnameHash(hash, site_id);

    site_id++;
  }
}

scoped_ptr<SupervisedUserURLFilter::Contents> FilterBuilder::Build() {
  DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
  contents_->url_matcher.AddConditionSets(all_conditions_);
  return contents_.Pass();
}

scoped_ptr<SupervisedUserURLFilter::Contents> CreateWhitelistFromPatterns(
    const std::vector<std::string>& patterns) {
  DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());

  FilterBuilder builder;
  for (const std::string& pattern : patterns) {
    // TODO(bauerb): We should create a fake site for the whitelist.
    builder.AddPattern(pattern, -1);
  }

  return builder.Build();
}

scoped_ptr<SupervisedUserURLFilter::Contents>
LoadWhitelistsOnBlockingPoolThread(
    ScopedVector<SupervisedUserSiteList> site_lists) {
  DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());

  FilterBuilder builder;
  for (SupervisedUserSiteList* site_list : site_lists)
    builder.AddSiteList(site_list);

  return builder.Build();
}

}  // namespace

SupervisedUserURLFilter::SupervisedUserURLFilter()
    : default_behavior_(ALLOW),
      contents_(new Contents()),
      blacklist_(NULL) {
  // Detach from the current thread so we can be constructed on a different
  // thread than the one where we're used.
  DetachFromThread();
}

SupervisedUserURLFilter::~SupervisedUserURLFilter() {
  DCHECK(CalledOnValidThread());
}

// static
SupervisedUserURLFilter::FilteringBehavior
SupervisedUserURLFilter::BehaviorFromInt(int behavior_value) {
  DCHECK_GE(behavior_value, ALLOW);
  DCHECK_LE(behavior_value, BLOCK);
  return static_cast<FilteringBehavior>(behavior_value);
}

// static
GURL SupervisedUserURLFilter::Normalize(const GURL& url) {
  GURL normalized_url = url;
  GURL::Replacements replacements;
  // Strip username, password, query, and ref.
  replacements.ClearUsername();
  replacements.ClearPassword();
  replacements.ClearQuery();
  replacements.ClearRef();
  return url.ReplaceComponents(replacements);
}

// static
bool SupervisedUserURLFilter::HasFilteredScheme(const GURL& url) {
  for (size_t i = 0; i < arraysize(kFilteredSchemes); ++i) {
    if (url.scheme() == kFilteredSchemes[i])
      return true;
  }
  return false;
}

std::string GetHostnameHash(const GURL& url) {
  std::string hash = base::SHA1HashString(url.host());
  return base::HexEncode(hash.data(), hash.length());
}

// static
bool SupervisedUserURLFilter::HostMatchesPattern(const std::string& host,
                                                 const std::string& pattern) {
  std::string trimmed_pattern = pattern;
  std::string trimmed_host = host;
  if (EndsWith(pattern, ".*", true)) {
    size_t registry_length = GetRegistryLength(
        trimmed_host, EXCLUDE_UNKNOWN_REGISTRIES, EXCLUDE_PRIVATE_REGISTRIES);
    // A host without a known registry part does not match.
    if (registry_length == 0)
      return false;

    trimmed_pattern.erase(trimmed_pattern.length() - 2);
    trimmed_host.erase(trimmed_host.length() - (registry_length + 1));
  }

  if (StartsWithASCII(trimmed_pattern, "*.", true)) {
    trimmed_pattern.erase(0, 2);

    // The remaining pattern should be non-empty, and it should not contain
    // further stars. Also the trimmed host needs to end with the trimmed
    // pattern.
    if (trimmed_pattern.empty() ||
        trimmed_pattern.find('*') != std::string::npos ||
        !EndsWith(trimmed_host, trimmed_pattern, true)) {
      return false;
    }

    // The trimmed host needs to have a dot separating the subdomain from the
    // matched pattern piece, unless there is no subdomain.
    int pos = trimmed_host.length() - trimmed_pattern.length();
    DCHECK_GE(pos, 0);
    return (pos == 0) || (trimmed_host[pos - 1] == '.');
  }

  return trimmed_host == trimmed_pattern;
}

SupervisedUserURLFilter::FilteringBehavior
SupervisedUserURLFilter::GetFilteringBehaviorForURL(const GURL& url) const {
  DCHECK(CalledOnValidThread());

  // URLs with a non-standard scheme (e.g. chrome://) are always allowed.
  if (!HasFilteredScheme(url))
    return ALLOW;

  // Check manual overrides for the exact URL.
  std::map<GURL, bool>::const_iterator url_it = url_map_.find(Normalize(url));
  if (url_it != url_map_.end())
    return url_it->second ? ALLOW : BLOCK;

  // Check manual overrides for the hostname.
  std::string host = url.host();
  std::map<std::string, bool>::const_iterator host_it = host_map_.find(host);
  if (host_it != host_map_.end())
    return host_it->second ? ALLOW : BLOCK;

  // Look for patterns matching the hostname, with a value that is different
  // from the default (a value of true in the map meaning allowed).
  for (const std::pair<std::string, bool>& host_entry : host_map_) {
    if ((host_entry.second == (default_behavior_ == BLOCK)) &&
        HostMatchesPattern(host, host_entry.first)) {
      return host_entry.second ? ALLOW : BLOCK;
    }
  }

  // If there's no blacklist and the default behavior is to allow, we don't need
  // to check anything else.
  if (!blacklist_ && default_behavior_ == ALLOW)
    return ALLOW;

  // Check the list of URL patterns.
  std::set<URLMatcherConditionSet::ID> matching_ids =
      contents_->url_matcher.MatchURL(url);
  if (!matching_ids.empty())
    return ALLOW;

  // Check the list of hostname hashes.
  if (contents_->hash_site_map.count(GetHostnameHash(url)))
    return ALLOW;

  // Check the static blacklist.
  if (blacklist_ && blacklist_->HasURL(url))
    return BLOCK;

  // Fall back to the default behavior.
  return default_behavior_;
}

void SupervisedUserURLFilter::GetSites(
    const GURL& url,
    std::vector<SupervisedUserSiteList::Site*>* sites) const {
  std::set<URLMatcherConditionSet::ID> matching_ids =
      contents_->url_matcher.MatchURL(url);
  for (const URLMatcherConditionSet::ID& id : matching_ids) {
    std::map<URLMatcherConditionSet::ID, int>::const_iterator entry =
        contents_->matcher_site_map.find(id);
    if (entry == contents_->matcher_site_map.end()) {
      NOTREACHED();
      continue;
    }
    sites->push_back(&contents_->sites[entry->second]);
  }

  typedef base::hash_multimap<std::string, int>::const_iterator
      hash_site_map_iterator;
  std::pair<hash_site_map_iterator, hash_site_map_iterator> bounds =
      contents_->hash_site_map.equal_range(GetHostnameHash(url));
  for (hash_site_map_iterator hash_it = bounds.first;
       hash_it != bounds.second; hash_it++) {
    sites->push_back(&contents_->sites[hash_it->second]);
  }
}

void SupervisedUserURLFilter::SetDefaultFilteringBehavior(
    FilteringBehavior behavior) {
  DCHECK(CalledOnValidThread());
  default_behavior_ = behavior;
}

void SupervisedUserURLFilter::LoadWhitelists(
    ScopedVector<SupervisedUserSiteList> site_lists) {
  DCHECK(CalledOnValidThread());

  base::PostTaskAndReplyWithResult(
      BrowserThread::GetBlockingPool(),
      FROM_HERE,
      base::Bind(&LoadWhitelistsOnBlockingPoolThread,
                 base::Passed(&site_lists)),
      base::Bind(&SupervisedUserURLFilter::SetContents, this));
}

void SupervisedUserURLFilter::SetBlacklist(SupervisedUserBlacklist* blacklist) {
  blacklist_ = blacklist;
}

void SupervisedUserURLFilter::SetFromPatterns(
    const std::vector<std::string>& patterns) {
  DCHECK(CalledOnValidThread());

  base::PostTaskAndReplyWithResult(
      BrowserThread::GetBlockingPool(),
      FROM_HERE,
      base::Bind(&CreateWhitelistFromPatterns, patterns),
      base::Bind(&SupervisedUserURLFilter::SetContents, this));
}

void SupervisedUserURLFilter::SetManualHosts(
    const std::map<std::string, bool>* host_map) {
  DCHECK(CalledOnValidThread());
  host_map_ = *host_map;
  UMA_HISTOGRAM_CUSTOM_COUNTS("ManagedMode.ManualHostsEntries",
                              host_map->size(), 1, 1000, 50);
}

void SupervisedUserURLFilter::SetManualURLs(
    const std::map<GURL, bool>* url_map) {
  DCHECK(CalledOnValidThread());
  url_map_ = *url_map;
  UMA_HISTOGRAM_CUSTOM_COUNTS("ManagedMode.ManualURLsEntries",
                              url_map->size(), 1, 1000, 50);
}

void SupervisedUserURLFilter::AddObserver(Observer* observer) {
  observers_.AddObserver(observer);
}

void SupervisedUserURLFilter::RemoveObserver(Observer* observer) {
  observers_.RemoveObserver(observer);
}

void SupervisedUserURLFilter::SetContents(scoped_ptr<Contents> contents) {
  DCHECK(CalledOnValidThread());
  contents_ = contents.Pass();
  FOR_EACH_OBSERVER(Observer, observers_, OnSiteListUpdated());
}