diff --git a/omaha_request_action.cc b/omaha_request_action.cc
index deb294a..5b69ec8 100644
--- a/omaha_request_action.cc
+++ b/omaha_request_action.cc
@@ -48,6 +48,7 @@
 #include "update_engine/connection_manager_interface.h"
 #include "update_engine/metrics_reporter_interface.h"
 #include "update_engine/metrics_utils.h"
+#include "update_engine/omaha_request_builder_xml.h"
 #include "update_engine/omaha_request_params.h"
 #include "update_engine/p2p_manager.h"
 #include "update_engine/payload_state_interface.h"
@@ -106,8 +107,6 @@
 constexpr char kValPostInstall[] = "postinstall";
 constexpr char kValNoUpdate[] = "noupdate";
 
-constexpr char kOmahaUpdaterVersion[] = "0.1.0.0";
-
 // X-Goog-Update headers.
 constexpr char kXGoogleUpdateInteractivity[] = "X-Goog-Update-Interactivity";
 constexpr char kXGoogleUpdateAppId[] = "X-Goog-Update-AppId";
@@ -119,362 +118,6 @@
 constexpr char kAttrFirmwareVersion[] = "firmware_version";
 constexpr char kAttrKernelVersion[] = "kernel_version";
 
-namespace {
-
-// Returns an XML ping element attribute assignment with attribute
-// |name| and value |ping_days| if |ping_days| has a value that needs
-// to be sent, or an empty string otherwise.
-string GetPingAttribute(const string& name, int ping_days) {
-  if (ping_days > 0 || ping_days == OmahaRequestAction::kNeverPinged)
-    return base::StringPrintf(" %s=\"%d\"", name.c_str(), ping_days);
-  return "";
-}
-
-// Returns an XML ping element if any of the elapsed days need to be
-// sent, or an empty string otherwise.
-string GetPingXml(int ping_active_days, int ping_roll_call_days) {
-  string ping_active = GetPingAttribute("a", ping_active_days);
-  string ping_roll_call = GetPingAttribute("r", ping_roll_call_days);
-  if (!ping_active.empty() || !ping_roll_call.empty()) {
-    return base::StringPrintf("        <ping active=\"1\"%s%s></ping>\n",
-                              ping_active.c_str(),
-                              ping_roll_call.c_str());
-  }
-  return "";
-}
-
-// Returns an XML that goes into the body of the <app> element of the Omaha
-// request based on the given parameters.
-string GetAppBody(const OmahaEvent* event,
-                  OmahaRequestParams* params,
-                  bool ping_only,
-                  bool include_ping,
-                  bool skip_updatecheck,
-                  int ping_active_days,
-                  int ping_roll_call_days,
-                  PrefsInterface* prefs) {
-  string app_body;
-  if (event == nullptr) {
-    if (include_ping)
-      app_body = GetPingXml(ping_active_days, ping_roll_call_days);
-    if (!ping_only) {
-      if (!skip_updatecheck) {
-        app_body += "        <updatecheck";
-        if (!params->target_version_prefix().empty()) {
-          app_body += base::StringPrintf(
-              " targetversionprefix=\"%s\"",
-              XmlEncodeWithDefault(params->target_version_prefix(), "")
-                  .c_str());
-          // Rollback requires target_version_prefix set.
-          if (params->rollback_allowed()) {
-            app_body += " rollback_allowed=\"true\"";
-          }
-        }
-        app_body += "></updatecheck>\n";
-      }
-
-      // If this is the first update check after a reboot following a previous
-      // update, generate an event containing the previous version number. If
-      // the previous version preference file doesn't exist the event is still
-      // generated with a previous version of 0.0.0.0 -- this is relevant for
-      // older clients or new installs. The previous version event is not sent
-      // for ping-only requests because they come before the client has
-      // rebooted. The previous version event is also not sent if it was already
-      // sent for this new version with a previous updatecheck.
-      string prev_version;
-      if (!prefs->GetString(kPrefsPreviousVersion, &prev_version)) {
-        prev_version = "0.0.0.0";
-      }
-      // We only store a non-empty previous version value after a successful
-      // update in the previous boot. After reporting it back to the server,
-      // we clear the previous version value so it doesn't get reported again.
-      if (!prev_version.empty()) {
-        app_body += base::StringPrintf(
-            "        <event eventtype=\"%d\" eventresult=\"%d\" "
-            "previousversion=\"%s\"></event>\n",
-            OmahaEvent::kTypeRebootedAfterUpdate,
-            OmahaEvent::kResultSuccess,
-            XmlEncodeWithDefault(prev_version, "0.0.0.0").c_str());
-        LOG_IF(WARNING, !prefs->SetString(kPrefsPreviousVersion, ""))
-            << "Unable to reset the previous version.";
-      }
-    }
-  } else {
-    // The error code is an optional attribute so append it only if the result
-    // is not success.
-    string error_code;
-    if (event->result != OmahaEvent::kResultSuccess) {
-      error_code = base::StringPrintf(" errorcode=\"%d\"",
-                                      static_cast<int>(event->error_code));
-    }
-    app_body = base::StringPrintf(
-        "        <event eventtype=\"%d\" eventresult=\"%d\"%s></event>\n",
-        event->type,
-        event->result,
-        error_code.c_str());
-  }
-
-  return app_body;
-}
-
-// Returns the cohort* argument to include in the <app> tag for the passed
-// |arg_name| and |prefs_key|, if any. The return value is suitable to
-// concatenate to the list of arguments and includes a space at the end.
-string GetCohortArgXml(PrefsInterface* prefs,
-                       const string arg_name,
-                       const string prefs_key) {
-  // There's nothing wrong with not having a given cohort setting, so we check
-  // existence first to avoid the warning log message.
-  if (!prefs->Exists(prefs_key))
-    return "";
-  string cohort_value;
-  if (!prefs->GetString(prefs_key, &cohort_value) || cohort_value.empty())
-    return "";
-  // This is a sanity check to avoid sending a huge XML file back to Ohama due
-  // to a compromised stateful partition making the update check fail in low
-  // network environments envent after a reboot.
-  if (cohort_value.size() > 1024) {
-    LOG(WARNING) << "The omaha cohort setting " << arg_name
-                 << " has a too big value, which must be an error or an "
-                    "attacker trying to inhibit updates.";
-    return "";
-  }
-
-  string escaped_xml_value;
-  if (!XmlEncode(cohort_value, &escaped_xml_value)) {
-    LOG(WARNING) << "The omaha cohort setting " << arg_name
-                 << " is ASCII-7 invalid, ignoring it.";
-    return "";
-  }
-
-  return base::StringPrintf(
-      "%s=\"%s\" ", arg_name.c_str(), escaped_xml_value.c_str());
-}
-
-struct OmahaAppData {
-  string id;
-  string version;
-  string product_components;
-};
-
-bool IsValidComponentID(const string& id) {
-  for (char c : id) {
-    if (!isalnum(c) && c != '-' && c != '_' && c != '.')
-      return false;
-  }
-  return true;
-}
-
-// Returns an XML that corresponds to the entire <app> node of the Omaha
-// request based on the given parameters.
-string GetAppXml(const OmahaEvent* event,
-                 OmahaRequestParams* params,
-                 const OmahaAppData& app_data,
-                 bool ping_only,
-                 bool include_ping,
-                 bool skip_updatecheck,
-                 int ping_active_days,
-                 int ping_roll_call_days,
-                 int install_date_in_days,
-                 SystemState* system_state) {
-  string app_body = GetAppBody(event,
-                               params,
-                               ping_only,
-                               include_ping,
-                               skip_updatecheck,
-                               ping_active_days,
-                               ping_roll_call_days,
-                               system_state->prefs());
-  string app_versions;
-
-  // If we are downgrading to a more stable channel and we are allowed to do
-  // powerwash, then pass 0.0.0.0 as the version. This is needed to get the
-  // highest-versioned payload on the destination channel.
-  if (params->ShouldPowerwash()) {
-    LOG(INFO) << "Passing OS version as 0.0.0.0 as we are set to powerwash "
-              << "on downgrading to the version in the more stable channel";
-    app_versions = "version=\"0.0.0.0\" from_version=\"" +
-                   XmlEncodeWithDefault(app_data.version, "0.0.0.0") + "\" ";
-  } else {
-    app_versions = "version=\"" +
-                   XmlEncodeWithDefault(app_data.version, "0.0.0.0") + "\" ";
-  }
-
-  string download_channel = params->download_channel();
-  string app_channels =
-      "track=\"" + XmlEncodeWithDefault(download_channel, "") + "\" ";
-  if (params->current_channel() != download_channel) {
-    app_channels += "from_track=\"" +
-                    XmlEncodeWithDefault(params->current_channel(), "") + "\" ";
-  }
-
-  string delta_okay_str = params->delta_okay() ? "true" : "false";
-
-  // If install_date_days is not set (e.g. its value is -1 ), don't
-  // include the attribute.
-  string install_date_in_days_str = "";
-  if (install_date_in_days >= 0) {
-    install_date_in_days_str =
-        base::StringPrintf("installdate=\"%d\" ", install_date_in_days);
-  }
-
-  string app_cohort_args;
-  app_cohort_args +=
-      GetCohortArgXml(system_state->prefs(), "cohort", kPrefsOmahaCohort);
-  app_cohort_args += GetCohortArgXml(
-      system_state->prefs(), "cohorthint", kPrefsOmahaCohortHint);
-  app_cohort_args += GetCohortArgXml(
-      system_state->prefs(), "cohortname", kPrefsOmahaCohortName);
-
-  string fingerprint_arg;
-  if (!params->os_build_fingerprint().empty()) {
-    fingerprint_arg = "fingerprint=\"" +
-                      XmlEncodeWithDefault(params->os_build_fingerprint(), "") +
-                      "\" ";
-  }
-
-  string buildtype_arg;
-  if (!params->os_build_type().empty()) {
-    buildtype_arg = "os_build_type=\"" +
-                    XmlEncodeWithDefault(params->os_build_type(), "") + "\" ";
-  }
-
-  string product_components_args;
-  if (!params->ShouldPowerwash() && !app_data.product_components.empty()) {
-    brillo::KeyValueStore store;
-    if (store.LoadFromString(app_data.product_components)) {
-      for (const string& key : store.GetKeys()) {
-        if (!IsValidComponentID(key)) {
-          LOG(ERROR) << "Invalid component id: " << key;
-          continue;
-        }
-        string version;
-        if (!store.GetString(key, &version)) {
-          LOG(ERROR) << "Failed to get version for " << key
-                     << " in product_components.";
-          continue;
-        }
-        product_components_args +=
-            base::StringPrintf("_%s.version=\"%s\" ",
-                               key.c_str(),
-                               XmlEncodeWithDefault(version, "").c_str());
-      }
-    } else {
-      LOG(ERROR) << "Failed to parse product_components:\n"
-                 << app_data.product_components;
-    }
-  }
-
-  // clang-format off
-  string app_xml = "    <app "
-      "appid=\"" + XmlEncodeWithDefault(app_data.id, "") + "\" " +
-      app_cohort_args +
-      app_versions +
-      app_channels +
-      product_components_args +
-      fingerprint_arg +
-      buildtype_arg +
-      "lang=\"" + XmlEncodeWithDefault(params->app_lang(), "en-US") + "\" " +
-      "board=\"" + XmlEncodeWithDefault(params->os_board(), "") + "\" " +
-      "hardware_class=\"" + XmlEncodeWithDefault(params->hwid(), "") + "\" " +
-      "delta_okay=\"" + delta_okay_str + "\" "
-      "fw_version=\"" + XmlEncodeWithDefault(params->fw_version(), "") + "\" " +
-      "ec_version=\"" + XmlEncodeWithDefault(params->ec_version(), "") + "\" " +
-      install_date_in_days_str +
-      ">\n" +
-         app_body +
-      "    </app>\n";
-  // clang-format on
-  return app_xml;
-}
-
-// Returns an XML that corresponds to the entire <os> node of the Omaha
-// request based on the given parameters.
-string GetOsXml(OmahaRequestParams* params) {
-  string os_xml =
-      "    <os "
-      "version=\"" +
-      XmlEncodeWithDefault(params->os_version(), "") + "\" " + "platform=\"" +
-      XmlEncodeWithDefault(params->os_platform(), "") + "\" " + "sp=\"" +
-      XmlEncodeWithDefault(params->os_sp(), "") +
-      "\">"
-      "</os>\n";
-  return os_xml;
-}
-
-// Returns an XML that corresponds to the entire Omaha request based on the
-// given parameters.
-string GetRequestXml(const OmahaEvent* event,
-                     OmahaRequestParams* params,
-                     bool ping_only,
-                     bool include_ping,
-                     int ping_active_days,
-                     int ping_roll_call_days,
-                     int install_date_in_days,
-                     SystemState* system_state) {
-  string os_xml = GetOsXml(params);
-  OmahaAppData product_app = {
-      .id = params->GetAppId(),
-      .version = params->app_version(),
-      .product_components = params->product_components()};
-  // Skips updatecheck for platform app in case of an install operation.
-  string app_xml = GetAppXml(event,
-                             params,
-                             product_app,
-                             ping_only,
-                             include_ping,
-                             params->is_install(), /* skip_updatecheck */
-                             ping_active_days,
-                             ping_roll_call_days,
-                             install_date_in_days,
-                             system_state);
-  if (!params->system_app_id().empty()) {
-    OmahaAppData system_app = {.id = params->system_app_id(),
-                               .version = params->system_version()};
-    app_xml += GetAppXml(event,
-                         params,
-                         system_app,
-                         ping_only,
-                         include_ping,
-                         false, /* skip_updatecheck */
-                         ping_active_days,
-                         ping_roll_call_days,
-                         install_date_in_days,
-                         system_state);
-  }
-  // Create APP ID according to |dlc_module_id| (sticking the current AppID to
-  // the DLC module ID with an underscode).
-  for (const auto& dlc_module_id : params->dlc_module_ids()) {
-    OmahaAppData dlc_module_app = {
-        .id = params->GetAppId() + "_" + dlc_module_id,
-        .version = params->app_version()};
-    app_xml += GetAppXml(event,
-                         params,
-                         dlc_module_app,
-                         ping_only,
-                         include_ping,
-                         false, /* skip_updatecheck */
-                         ping_active_days,
-                         ping_roll_call_days,
-                         install_date_in_days,
-                         system_state);
-  }
-
-  string request_xml = base::StringPrintf(
-      "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
-      "<request protocol=\"3.0\" updater=\"%s\" updaterversion=\"%s\""
-      " installsource=\"%s\" ismachine=\"1\">\n%s%s</request>\n",
-      constants::kOmahaUpdaterID,
-      kOmahaUpdaterVersion,
-      params->interactive() ? "ondemandupdate" : "scheduler",
-      os_xml.c_str(),
-      app_xml.c_str());
-
-  return request_xml;
-}
-
-}  // namespace
-
 // Struct used for holding data obtained when parsing the XML.
 struct OmahaParserData {
   explicit OmahaParserData(XML_Parser _xml_parser) : xml_parser(_xml_parser) {}
@@ -638,49 +281,6 @@
 
 }  // namespace
 
-bool XmlEncode(const string& input, string* output) {
-  if (std::find_if(input.begin(), input.end(), [](const char c) {
-        return c & 0x80;
-      }) != input.end()) {
-    LOG(WARNING) << "Invalid ASCII-7 string passed to the XML encoder:";
-    utils::HexDumpString(input);
-    return false;
-  }
-  output->clear();
-  // We need at least input.size() space in the output, but the code below will
-  // handle it if we need more.
-  output->reserve(input.size());
-  for (char c : input) {
-    switch (c) {
-      case '\"':
-        output->append("&quot;");
-        break;
-      case '\'':
-        output->append("&apos;");
-        break;
-      case '&':
-        output->append("&amp;");
-        break;
-      case '<':
-        output->append("&lt;");
-        break;
-      case '>':
-        output->append("&gt;");
-        break;
-      default:
-        output->push_back(c);
-    }
-  }
-  return true;
-}
-
-string XmlEncodeWithDefault(const string& input, const string& default_value) {
-  string output;
-  if (XmlEncode(input, &output))
-    return output;
-  return default_value;
-}
-
 OmahaRequestAction::OmahaRequestAction(
     SystemState* system_state,
     OmahaEvent* event,
@@ -732,8 +332,8 @@
 }
 
 bool OmahaRequestAction::ShouldPing() const {
-  if (ping_active_days_ == OmahaRequestAction::kNeverPinged &&
-      ping_roll_call_days_ == OmahaRequestAction::kNeverPinged) {
+  if (ping_active_days_ == kNeverPinged &&
+      ping_roll_call_days_ == kNeverPinged) {
     int powerwash_count = system_state_->hardware()->GetPowerwashCount();
     if (powerwash_count > 0) {
       LOG(INFO) << "Not sending ping with a=-1 r=-1 to omaha because "