diff --git a/update_check_action.cc b/update_check_action.cc
new file mode 100644
index 0000000..a4942a6
--- /dev/null
+++ b/update_check_action.cc
@@ -0,0 +1,281 @@
+// Copyright (c) 2009 The Chromium OS 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 "update_engine/update_check_action.h"
+#include <sstream>
+
+#include <libxml/parser.h>
+#include <libxml/xpath.h>
+#include <libxml/xpathInternals.h>
+
+#include "update_engine/action_pipe.h"
+
+using std::string;
+
+namespace chromeos_update_engine {
+
+const char* const UpdateCheckParams::kAppId(
+    "87efface-864d-49a5-9bb3-4b050a7c227a");
+const char* const UpdateCheckParams::kOsPlatform("Chrome OS");
+const char* const UpdateCheckParams::kOsVersion("Indy");
+
+namespace {
+
+const string kGupdateVersion("ChromeOSUpdateEngine-0.1.0.0");
+
+// This is handy for passing strings into libxml2
+#define ConstXMLStr(x) (reinterpret_cast<const xmlChar*>(x))
+
+// These are for scoped_ptr_malloc, which is like scoped_ptr, but allows
+// a custom free() function to be specified.
+class ScopedPtrXmlDocFree {
+ public:
+  inline void operator()(void* x) const {
+    xmlFreeDoc(reinterpret_cast<xmlDoc*>(x));
+  }
+};
+class ScopedPtrXmlFree {
+ public:
+  inline void operator()(void* x) const {
+    xmlFree(x);
+  }
+};
+class ScopedPtrXmlXPathObjectFree {
+ public:
+  inline void operator()(void* x) const {
+    xmlXPathFreeObject(reinterpret_cast<xmlXPathObject*>(x));
+  }
+};
+class ScopedPtrXmlXPathContextFree {
+ public:
+  inline void operator()(void* x) const {
+    xmlXPathFreeContext(reinterpret_cast<xmlXPathContext*>(x));
+  }
+};
+
+// Returns a properly formatted omaha request for an update check
+string FormatRequest(const UpdateCheckParams& params) {
+  return string("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
+      "<o:gupdate xmlns:o=\"http://www.google.com/update2/request\" "
+      "version=\"" + XmlEncode(kGupdateVersion) + "\" protocol=\"2.0\" "
+      "machineid=\"") + XmlEncode(params.machine_id) + "\" ismachine=\"1\" "
+      "userid=\"" + XmlEncode(params.user_id) + "\">\n"
+      "    <o:os version=\"" + XmlEncode(params.os_version) + "\" platform=\"" +
+      XmlEncode(params.os_platform) + "\" sp=\"" +
+      XmlEncode(params.os_sp) + "\"></o:os>\n"
+      "    <o:app appid=\"" + XmlEncode(params.app_id) + "\" version=\"" +
+      XmlEncode(params.app_version) + "\" "
+      "lang=\"" + XmlEncode(params.app_lang) + "\" track=\"" +
+      XmlEncode(params.app_track) + "\">\n"
+      "        <o:ping active=\"0\"></o:ping>\n"
+      "        <o:updatecheck></o:updatecheck>\n"
+      "    </o:app>\n"
+      "</o:gupdate>\n";
+}
+}  // namespace {}
+
+// Encodes XML entities in a given string with libxml2. input must be
+// UTF-8 formatted. Output will be UTF-8 formatted.
+string XmlEncode(const string& input) {
+//  // TODO(adlr): if allocating a new xmlDoc each time is taking up too much
+//  // cpu, considering creating one and caching it.
+//  scoped_ptr_malloc<xmlDoc, ScopedPtrXmlDocFree> xml_doc(
+//      xmlNewDoc(ConstXMLStr("1.0")));
+//  if (!xml_doc.get()) {
+//    LOG(ERROR) << "Unable to create xmlDoc";
+//    return "";
+//  }
+  scoped_ptr_malloc<xmlChar, ScopedPtrXmlFree> str(
+      xmlEncodeEntitiesReentrant(NULL, ConstXMLStr(input.c_str())));
+  return string(reinterpret_cast<const char *>(str.get()));
+}
+
+UpdateCheckAction::UpdateCheckAction(const UpdateCheckParams& params,
+                                     HttpFetcher* http_fetcher)
+    : params_(params), http_fetcher_(http_fetcher) {}
+
+UpdateCheckAction::~UpdateCheckAction() {}
+
+void UpdateCheckAction::PerformAction() {
+  http_fetcher_->set_delegate(this);
+  string request_post(FormatRequest(params_));
+  http_fetcher_->SetPostData(request_post.data(), request_post.size());
+  http_fetcher_->BeginTransfer("https://tools.google.com/service/update2");
+}
+
+void UpdateCheckAction::TerminateProcessing() {
+  http_fetcher_->TerminateTransfer();
+}
+
+// We just store the response in the buffer. Once we've received all bytes,
+// we'll look in the buffer and decide what to do.
+void UpdateCheckAction::ReceivedBytes(HttpFetcher *fetcher,
+                                   const char* bytes,
+                                   int length) {
+  response_buffer_.reserve(response_buffer_.size() + length);
+  response_buffer_.insert(response_buffer_.end(), bytes, bytes + length);
+}
+
+namespace {
+// A little object to call ActionComplete on the ActionProcessor when
+// it's destructed.
+class ScopedActionCompleter {
+ public:
+  explicit ScopedActionCompleter(ActionProcessor* processor,
+                                 AbstractAction* action)
+      : processor_(processor), action_(action), success_(false) {}
+  ~ScopedActionCompleter() {
+    processor_->ActionComplete(action_, success_);
+  }
+  void set_success(bool success) {
+    success_ = success;
+  }
+ private:
+  ActionProcessor* processor_;
+  AbstractAction* action_;
+  bool success_;
+  DISALLOW_COPY_AND_ASSIGN(ScopedActionCompleter);
+};
+
+// If non-NULL response, caller is responsible for calling xmlXPathFreeObject()
+// on the returned object.
+// This code is roughly based on the libxml tutorial at:
+// http://xmlsoft.org/tutorial/apd.html
+xmlXPathObject* GetNodeSet(xmlDoc* doc, const xmlChar* xpath,
+                           const xmlChar* ns, const xmlChar* ns_url) {
+  xmlXPathObject* result = NULL;
+
+  scoped_ptr_malloc<xmlXPathContext, ScopedPtrXmlXPathContextFree> context(
+      xmlXPathNewContext(doc));
+  if (!context.get()) {
+    LOG(ERROR) << "xmlXPathNewContext() returned NULL";
+    return NULL;
+  }
+  if (xmlXPathRegisterNs(context.get(), ns, ns_url) < 0) {
+    LOG(ERROR) << "xmlXPathRegisterNs() returned error";
+    return NULL;
+  }
+
+  result = xmlXPathEvalExpression(xpath, context.get());
+
+  if (result == NULL) {
+    LOG(ERROR) << "xmlXPathEvalExpression returned error";
+    return NULL;
+  }
+  if(xmlXPathNodeSetIsEmpty(result->nodesetval)){
+    LOG(INFO) << "xpath not found in doc";
+    xmlXPathFreeObject(result);
+    return NULL;
+  }
+  return result;
+}
+
+// Returns the string value of a named attribute on a node, or empty string
+// if no such node exists. If the attribute exists and has a value of
+// empty string, there's no way to distinguish that from the attribute
+// not existing.
+string XmlGetProperty(xmlNode* node, const char* name) {
+  if (!xmlHasProp(node, ConstXMLStr(name)))
+    return "";
+  scoped_ptr_malloc<xmlChar, ScopedPtrXmlFree> str(
+      xmlGetProp(node, ConstXMLStr(name)));
+  string ret(reinterpret_cast<const char *>(str.get()));
+  return ret;
+}
+
+// Parses a 64 bit base-10 int from a string and returns it. Returns 0
+// on error. If the string contains "0", that's indistinguishable from
+// error.
+off_t ParseInt(const string& str) {
+  off_t ret = 0;
+
+  int rc = sscanf(str.c_str(), "%lld", &ret);
+  if (rc < 1) {
+    // failure
+    return 0;
+  }
+  return ret;
+}
+}  // namespace {}
+
+// If the transfer was successful, this uses libxml2 to parse the response
+// and fill in the appropriate fields of the output object. Also, notifies
+// the processor that we're done.
+void UpdateCheckAction::TransferComplete(HttpFetcher *fetcher,
+                                         bool successful) {
+  ScopedActionCompleter completer(processor_, this);
+  if (!successful)
+    return;
+  if (!HasOutputPipe()) {
+    // Just set success to whether or not the http transfer succeeded,
+    // which must be true at this point in the code.
+    completer.set_success(true);
+    return;
+  }
+
+  // parse our response and fill the fields in the output object
+  scoped_ptr_malloc<xmlDoc, ScopedPtrXmlDocFree> doc(
+      xmlParseMemory(&response_buffer_[0], response_buffer_.size()));
+  if (!doc.get()) {
+    LOG(ERROR) << "Omaha response not valid XML";
+    return;
+  }
+
+  static const char* kNamespace("x");
+  static const char* kUpdatecheckNodeXpath("/x:gupdate/x:app/x:updatecheck");
+  static const char* kNsUrl("http://www.google.com/update2/response");
+
+  scoped_ptr_malloc<xmlXPathObject, ScopedPtrXmlXPathObjectFree>
+      xpath_nodeset(GetNodeSet(doc.get(),
+                               ConstXMLStr(kUpdatecheckNodeXpath),
+                               ConstXMLStr(kNamespace),
+                               ConstXMLStr(kNsUrl)));
+  if (!xpath_nodeset.get()) {
+    return;
+  }
+  xmlNodeSet* nodeset = xpath_nodeset->nodesetval;
+  CHECK(nodeset) << "XPath missing NodeSet";
+  CHECK_GE(nodeset->nodeNr, 1);
+
+  xmlNode* updatecheck_node = nodeset->nodeTab[0];
+  // get status
+  if (!xmlHasProp(updatecheck_node, ConstXMLStr("status"))) {
+    LOG(ERROR) << "Response missing status";
+    return;
+  }
+
+  const string status(XmlGetProperty(updatecheck_node, "status"));
+  UpdateCheckResponse output_object;
+  if (status == "noupdate") {
+    LOG(INFO) << "No update.";
+    output_object.update_exists = false;
+    SetOutputObject(output_object);
+    completer.set_success(true);
+    return;
+  }
+
+  if (status != "ok") {
+    LOG(ERROR) << "Unknown status: " << status;
+    return;
+  }
+
+  // In best-effort fashion, fetch the rest of the expected attributes
+  // from the updatecheck node, then return the object
+  output_object.update_exists = true;
+  completer.set_success(true);
+
+  output_object.display_version =
+      XmlGetProperty(updatecheck_node, "DisplayVersion");
+  output_object.codebase = XmlGetProperty(updatecheck_node, "codebase");
+  output_object.more_info_url = XmlGetProperty(updatecheck_node, "MoreInfo");
+  output_object.hash = XmlGetProperty(updatecheck_node, "hash");
+  output_object.size = ParseInt(XmlGetProperty(updatecheck_node, "size"));
+  output_object.needs_admin =
+      XmlGetProperty(updatecheck_node, "needsadmin") == "true";
+  output_object.prompt = XmlGetProperty(updatecheck_node, "Prompt") == "true";
+  SetOutputObject(output_object);
+  return;
+}
+
+};  // namespace chromeos_update_engine