Upgrade cros_image_to_target.py to support Omaha v3 protocol.

As part of the efforts to support HTTP-based downloads for autoupdate,
we are upgrading update_engine from Omaha v2 to v3. So, we need to
update cros_image_to_target.py to also understand the v3 XML.

BUG=chromium-os:35930
TEST=Successfully updated my ZGB which was running the v3 update_engine.

Change-Id: I2b4831c1e87ccf064e79cd6d34205f19aedc9d57
Reviewed-on: https://gerrit.chromium.org/gerrit/37065
Reviewed-by: Chris Sosa <sosa@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Ready: Chris Sosa <sosa@chromium.org>
Tested-by: Chris Sosa <sosa@chromium.org>

bin/cros_image_to_target.py

@@ -39,6 +39,42 @@ STATEFUL_FILENAME = 'stateful.tgz'
 # How long do we wait for the server to start before launching client
 SERVER_STARTUP_WAIT = 1
 
+UPDATE_RESPONSE = """<?xml version="1.0" encoding="UTF-8"?>
+  <response protocol="3.0">
+    <daystart elapsed_seconds="%(time_elapsed)s"/>
+    <app appid="{%(appid)s}" status="ok">
+      <ping status="ok"/>
+      <updatecheck status="ok">
+        <urls>
+          <url codebase="%(codebase)s/"/>
+        </urls>
+        <manifest version="9999.0.0">
+          <packages>
+            <package hash="%(sha1)s" name="%(filename)s" size="%(size)s"
+                     required="true"/>
+          </packages>
+          <actions>
+            <action event="postinstall"
+              ChromeOSVersion="9999.0.0"
+              sha256="%(sha256)s"
+              needsadmin="false"
+              IsDelta="%(is_delta_format)s"
+              %(extra_attr)s />
+          </actions>
+        </manifest>
+      </updatecheck>
+    </app>
+  </response>
+  """
+NO_UPDATE_RESPONSE = """<?xml version="1.0" encoding="UTF-8"?>
+  <response" protocol="3.0">
+    <daystart elapsed_seconds="%(time_elapsed)s"/>
+    <app appid="{%(appid)s}" status="ok">
+      <ping status="ok"/>
+      <updatecheck status="noupdate"/>
+    </app>
+  </response>
+  """
 
 class Command(object):
   """Shell command ease-ups for Python."""
@@ -449,34 +485,6 @@ class StringUpdateResponse(UpdateResponse):
 class PingUpdateResponse(StringUpdateResponse):
   """Respond to a client ping with pre-fab XML response."""
 
-  app_id = '87efface-864d-49a5-9bb3-4b050a7c227a'
-  xmlns = 'http://www.google.com/update2/response'
-  payload_success_template = """<?xml version="1.0" encoding="UTF-8"?>
-    <gupdate xmlns="%s" protocol="2.0">
-    <daystart elapsed_seconds="%s"/>
-    <app appid="{%s}" status="ok">
-      <ping status="ok"/>
-      <updatecheck
-      codebase="%s"
-      hash="%s"
-      sha256="%s"
-      IsDelta="true"
-      needsadmin="false"
-      size="%s"
-      status="ok"/>
-    </app>
-    </gupdate>
-  """
-  payload_failure_template = """<?xml version="1.0" encoding="UTF-8"?>
-      <gupdate xmlns="%s" protocol="2.0">
-        <daystart elapsed_seconds="%s"/>
-        <app appid="{%s}" status="ok">
-          <ping status="ok"/>
-          <updatecheck status="noupdate"/>
-        </app>
-      </gupdate>
-    """
-
   def __init__(self):
     self.content_type = 'text/xml'
 
@@ -486,25 +494,90 @@ class PingUpdateResponse(StringUpdateResponse):
     PingUpdateResponse.file_sha256 = filesha256
     PingUpdateResponse.file_size = filesize
 
+  def GetCommonResponseValues(self):
+    """Returns a dictionary of default values that'll be substituted in the
+    response irrespective of the protocol version."""
+    response_values = {}
+    response_values['appid'] = '87efface-864d-49a5-9bb3-4b050a7c227a'
+    response_values['time_elapsed'] = self.SecondsSinceMidnight()
+    return response_values
+
+  def GetSubstitutedResponse(self, response_template, response_values):
+    """Substitutes the response template with response_values.
+
+    Args:
+      response_dict: Canned response template
+      response_values: Values to be substituted in the canned template.
+    Returns:
+      Xml string to be passed back to client.
+    Raises:
+      AutoupdateError if required response values are not present.
+    """
+    try:
+      response_xml = response_template % response_values
+      return response_xml
+    except KeyError as e:
+      self.Fatal('Missing response value: %s' % e)
+
+  def GetUpdateResponse(self, sha1, sha256, size, url, is_delta_format):
+    """Returns a response to the client corresponding to a new update.
+
+    Args:
+      sha1: SHA1 hash of update blob
+      sha256: SHA256 hash of update blob
+      size: size of update blob
+      url: where to find update blob
+      is_delta_format: true if url refers to a delta payload
+    Returns:
+      Xml string to be passed back to client.
+    """
+    response_values = self.GetCommonResponseValues()
+    response_values['sha1'] = sha1
+    response_values['sha256'] = sha256
+    response_values['size'] = size
+    response_values['url'] = url
+    (codebase, filename) = os.path.split(url)
+    response_values['codebase'] = codebase
+    response_values['filename'] = filename
+    response_values['is_delta_format'] = is_delta_format
+    response_values['extra_attr'] = ''
+    response_xml = self.GetSubstitutedResponse(UPDATE_RESPONSE,
+                                               response_values)
+    return response_xml
+
+  def GetNoUpdateResponse(self):
+    """Returns a response to the client corresponding to no update."""
+    response_values = self.GetCommonResponseValues()
+    response_xml = self.GetSubstitutedResponse(NO_UPDATE_RESPONSE,
+                                               response_values)
+    return response_xml
+
+
   def Reply(self, handler, send_content=True, post_data=None):
     """Return (using StringResponse) an XML reply to ForcedUpdate clients."""
 
     if not post_data:
       return UpdateResponse.Reply(self, handler)
 
-    request_version = (minidom.parseString(post_data).firstChild.
+    root = minidom.parseString(post_data)
-                       getElementsByTagName('o:app')[0].
+    protocol = root.firstChild.getAttribute('protocol')
-                       getAttribute('version'))
+    if (protocol != '3.0'):
+      raise BaseException('You first need to update your device to a build '
+          'that uses Omaha v3 protocol for the update_engine.')
+
+    app = root.firstChild.getElementsByTagName('app')[0]
+    request_version = app.getAttribute('version')
 
     if request_version == 'ForcedUpdate':
       host, pdict = cgi.parse_header(handler.headers.getheader('Host'))
-      self.string = (self.payload_success_template %
+      url = 'http://%s/%s' % (host, UPDATE_FILENAME)
-                     (self.xmlns, self.SecondsSinceMidnight(),
+      self.string = self.GetUpdateResponse(self.file_hash,
-                      self.app_id, 'http://%s/%s' % (host, UPDATE_FILENAME),
+                                           self.file_sha256,
-                      self.file_hash, self.file_sha256, self.file_size))
+                                           self.file_size,
+                                           url,
+                                           False) # is_delta_format
     else:
-      self.string = (self.payload_failure_template %
+      self.string = (self.GetNoUpdateResponse())
-                     (self.xmlns, self.SecondsSinceMidnight(), self.app_id))
 
     StringUpdateResponse.Reply(self, handler, send_content)