Add a config class for the settings reset prompt.

The config class encapsulates the configuration data for the settings
reset prompt experiment.

BUG=

Review-Url: https://codereview.chromium.org/2614773008
Cr-Commit-Position: refs/heads/master@{#443337}

chrome/browser/BUILD.gn

@@ -1082,6 +1082,8 @@ split_static_library("browser") {
     "resources_util.h",
     "safe_browsing/safe_browsing_tab_observer.cc",
     "safe_browsing/safe_browsing_tab_observer.h",
+    "safe_browsing/settings_reset_prompt/settings_reset_prompt_config.cc",
+    "safe_browsing/settings_reset_prompt/settings_reset_prompt_config.h",
     "safe_browsing/srt_client_info_win.cc",
     "safe_browsing/srt_client_info_win.h",
     "safe_browsing/srt_fetcher_win.cc",

chrome/browser/safe_browsing/settings_reset_prompt/settings_reset_prompt_config.cc

@@ -0,0 +1,189 @@
+// Copyright 2017 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/safe_browsing/settings_reset_prompt/settings_reset_prompt_config.h"
+
+#include <utility>
+
+#include "base/json/json_reader.h"
+#include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "base/values.h"
+#include "components/url_formatter/url_fixer.h"
+#include "components/variations/variations_associated_data.h"
+#include "crypto/sha2.h"
+#include "net/base/registry_controlled_domains/registry_controlled_domain.h"
+#include "url/gurl.h"
+
+namespace safe_browsing {
+
+namespace {
+
+const char kSettingsResetPromptFeatureName[] = "SettingsResetPrompt";
+const char kDomainHashesParamName[] = "domain_hashes";
+
+}  // namespace.
+
+const base::Feature kSettingsResetPrompt{kSettingsResetPromptFeatureName,
+                                         base::FEATURE_DISABLED_BY_DEFAULT};
+
+// static
+bool SettingsResetPromptConfig::IsPromptEnabled() {
+  // TODO(alito): Add prefs to local state to track when the user was
+  // last prompted and ensure that we only prompt once per reset prompt
+  // wave.
+  return base::FeatureList::IsEnabled(kSettingsResetPrompt);
+}
+
+// static
+std::unique_ptr<SettingsResetPromptConfig> SettingsResetPromptConfig::Create() {
+  if (!IsPromptEnabled())
+    return nullptr;
+
+  auto prompt_config = base::WrapUnique(new SettingsResetPromptConfig());
+  if (!prompt_config->Init())
+    return nullptr;
+
+  return prompt_config;
+}
+
+SettingsResetPromptConfig::SettingsResetPromptConfig() {}
+
+SettingsResetPromptConfig::~SettingsResetPromptConfig() {}
+
+int SettingsResetPromptConfig::UrlToResetDomainId(const GURL& url) const {
+  DCHECK(IsPromptEnabled());
+
+  // Do a best-effort to fix the URL before testing if it is valid.
+  GURL fixed_url =
+      url_formatter::FixupURL(url.possibly_invalid_spec(), std::string());
+  if (!fixed_url.is_valid())
+    return -1;
+
+  // Get the length of the top level domain or registry of the URL. Used
+  // to guard against trying to match the (effective) TLDs themselves.
+  size_t registry_length = net::registry_controlled_domains::GetRegistryLength(
+      fixed_url, net::registry_controlled_domains::INCLUDE_UNKNOWN_REGISTRIES,
+      net::registry_controlled_domains::INCLUDE_PRIVATE_REGISTRIES);
+  // Do not proceed, if |fixed_url| does not have a host or consists entirely of
+  // a registry or top domain.
+  if (registry_length == 0 || registry_length == std::string::npos)
+    return -1;
+
+  // The hashes in the prompt config are generally TLD+1 and identify
+  // only the topmost levels of URLs that we wish to prompt for. Try to
+  // match each sensible suffix of the URL host with the hashes in the
+  // prompt config. For example, if the host is
+  // "www.sub.domain.com", try hashes for:
+  // "www.sub.domain.com"
+  // "sub.domain.com"
+  // "domain.com"
+  // We Do not check top level or registry domains to guard against bad
+  // configuration data.
+  SHA256Hash hash(crypto::kSHA256Length, '\0');
+  base::StringPiece host = fixed_url.host_piece();
+  while (host.size() > registry_length) {
+    crypto::SHA256HashString(host, hash.data(), crypto::kSHA256Length);
+    auto iter = domain_hashes_.find(hash);
+    if (iter != domain_hashes_.end())
+      return iter->second;
+
+    size_t next_start_pos = host.find('.');
+    next_start_pos = next_start_pos == base::StringPiece::npos
+                         ? base::StringPiece::npos
+                         : next_start_pos + 1;
+    host = host.substr(next_start_pos);
+  }
+
+  return -1;
+}
+
+// Implements the hash function for SHA256Hash objects. Simply uses the
+// first bytes of the SHA256 hash as its own hash.
+size_t SettingsResetPromptConfig::SHA256HashHasher::operator()(
+    const SHA256Hash& key) const {
+  DCHECK_EQ(crypto::kSHA256Length, key.size());
+  // This is safe because |key| contains 32 bytes while a size_t is
+  // either 4 or 8 bytes.
+  return *reinterpret_cast<const size_t*>(key.data());
+}
+
+// These values are written to logs. New enum values can be added, but
+// existing enums must never be renumbered or deleted and reused. If you
+// do add values, also update the corresponding enum definition in the
+// histograms.xml file.
+enum SettingsResetPromptConfig::ConfigError : int {
+  CONFIG_ERROR_OK = 1,
+  CONFIG_ERROR_MISSING_DOMAIN_HASHES_PARAM = 2,
+  CONFIG_ERROR_BAD_DOMAIN_HASHES_PARAM = 3,
+  CONFIG_ERROR_BAD_DOMAIN_HASH = 4,
+  CONFIG_ERROR_BAD_DOMAIN_ID = 5,
+  CONFIG_ERROR_DUPLICATE_DOMAIN_HASH = 6,
+  CONFIG_ERROR_MAX
+};
+
+bool SettingsResetPromptConfig::Init() {
+  if (!IsPromptEnabled())
+    return false;
+
+  std::string domain_hashes_json = variations::GetVariationParamValueByFeature(
+      kSettingsResetPrompt, kDomainHashesParamName);
+  ConfigError error = ParseDomainHashes(domain_hashes_json);
+  UMA_HISTOGRAM_ENUMERATION("SettingsResetPrompt.ConfigError", error,
+                            CONFIG_ERROR_MAX);
+  return error == CONFIG_ERROR_OK;
+}
+
+SettingsResetPromptConfig::ConfigError
+SettingsResetPromptConfig::ParseDomainHashes(
+    const std::string& domain_hashes_json) {
+  if (domain_hashes_json.empty())
+    return CONFIG_ERROR_MISSING_DOMAIN_HASHES_PARAM;
+
+  // Is the input parseable JSON?
+  std::unique_ptr<base::DictionaryValue> domains_dict =
+      base::DictionaryValue::From(base::JSONReader::Read(domain_hashes_json));
+  if (!domains_dict || domains_dict->empty())
+    return CONFIG_ERROR_BAD_DOMAIN_HASHES_PARAM;
+
+  // The input JSON should be a hash object with hex-encoded 32-byte
+  // hashes as keys and integer IDs as values. For example,
+  //
+  // {"2714..D7": "1", "2821..CB": "2", ...}
+  //
+  // Each key in the hash should be a 64-byte long string and each
+  // integer ID should fit in an int.
+  domain_hashes_.clear();
+  for (base::DictionaryValue::Iterator iter(*domains_dict); !iter.IsAtEnd();
+       iter.Advance()) {
+    const std::string& hash_string = iter.key();
+    if (hash_string.size() != crypto::kSHA256Length * 2)
+      return CONFIG_ERROR_BAD_DOMAIN_HASH;
+
+    // Convert hex-encoded hash string to its numeric value as bytes.
+    SHA256Hash hash;
+    hash.reserve(crypto::kSHA256Length);
+    if (!base::HexStringToBytes(hash_string, &hash))
+      return CONFIG_ERROR_BAD_DOMAIN_HASH;
+
+    // Convert the ID string to an integer.
+    std::string domain_id_string;
+    int domain_id = -1;
+    if (!iter.value().GetAsString(&domain_id_string) ||
+        !base::StringToInt(domain_id_string, &domain_id) || domain_id < 0) {
+      return CONFIG_ERROR_BAD_DOMAIN_ID;
+    }
+
+    if (!domain_hashes_.insert(std::make_pair(std::move(hash), domain_id))
+             .second)
+      return CONFIG_ERROR_DUPLICATE_DOMAIN_HASH;
+  }
+
+  return CONFIG_ERROR_OK;
+}
+
+}  // namespace safe_browsing.

chrome/browser/safe_browsing/settings_reset_prompt/settings_reset_prompt_config.h

@@ -0,0 +1,65 @@
+// Copyright 2017 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.
+
+#ifndef CHROME_BROWSER_SAFE_BROWSING_SETTINGS_RESET_PROMPT_SETTINGS_RESET_PROMPT_CONFIG_H_
+#define CHROME_BROWSER_SAFE_BROWSING_SETTINGS_RESET_PROMPT_SETTINGS_RESET_PROMPT_CONFIG_H_
+
+#include <cstddef>
+#include <memory>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include "base/feature_list.h"
+#include "base/macros.h"
+
+class GURL;
+
+namespace safe_browsing {
+
+// Exposed for testing.
+extern const base::Feature kSettingsResetPrompt;
+
+// Encapsulates the state of the reset prompt experiment as well as
+// associated data.
+class SettingsResetPromptConfig {
+ public:
+  // Returns true if the settings reset prompt study is enabled.
+  static bool IsPromptEnabled();
+  // Factory method for creating instances of SettingsResetPromptConfig.
+  // Returns nullptr if |IsPromptEnabled()| is false or if something is wrong
+  // with the config parameters.
+  static std::unique_ptr<SettingsResetPromptConfig> Create();
+
+  ~SettingsResetPromptConfig();
+
+  // Returns a non-negative integer ID if |url| should trigger a
+  // settings reset prompt and a negative integer otherwise. The IDs
+  // identify the domains or entities that we want to prompt the user
+  // for and can be used for metrics reporting.
+  int UrlToResetDomainId(const GURL& url) const;
+
+  // TODO(alito): parameterize the set of things that we want to reset
+  // for so that we can control it from the finch config. For example,
+  // with functions like HomepageResetAllowed() etc.
+ private:
+  typedef std::vector<uint8_t> SHA256Hash;
+  struct SHA256HashHasher {
+    size_t operator()(const SHA256Hash& key) const;
+  };
+  enum ConfigError : int;
+
+  SettingsResetPromptConfig();
+  bool Init();
+  ConfigError ParseDomainHashes(const std::string& domain_hashes_json);
+
+  // Map of 32 byte SHA256 hashes to integer domain IDs.
+  std::unordered_map<SHA256Hash, int, SHA256HashHasher> domain_hashes_;
+
+  DISALLOW_COPY_AND_ASSIGN(SettingsResetPromptConfig);
+};
+
+}  // namespace safe_browsing
+
+#endif  // CHROME_BROWSER_SAFE_BROWSING_SETTINGS_RESET_PROMPT_SETTINGS_RESET_PROMPT_CONFIG_H_