Initial poc for RSA Accumulator snapshot: client side

This is missing test data for the client

Signed-off-by: Marina Moore <mnm678@gmail.com>

Author: mnm678

tests/test_updater.py

@@ -1779,29 +1779,29 @@ def test_13__targets_of_role(self):
 
 
 
-  def test_snapshot_merkle(self):
-    # replace timestamp with a merkle timestamp and create the updater
-    merkle_timestamp = os.path.join(self.repository_directory, 'metadata', 'timestamp-merkle.json')
+  def test_snapshot_rsa_acc(self):
+    # replace timestamp with an RSA accumulator timestamp and create the updater
+    rsa_acc_timestamp = os.path.join(self.repository_directory, 'metadata', 'timestamp-rsa.json')
     timestamp = os.path.join(self.repository_directory, 'metadata', 'timestamp.json')
 
-    shutil.move(merkle_timestamp, timestamp)
+    shutil.move(rsa_acc_timestamp, timestamp)
 
     repository_updater = updater.Updater(self.repository_name,
                                       self.repository_mirrors)
     repository_updater.refresh()
 
-    # Test verify merkle path
-    snapshot_info = repository_updater.verify_merkle_path('targets')
+    # Test verify RSA accumulator proof
+    snapshot_info = repository_updater.verify_rsa_acc_proof('targets')
     self.assertEqual(snapshot_info['version'], 1)
 
-    snapshot_info = repository_updater.verify_merkle_path('role1')
+    snapshot_info = repository_updater.verify_rsa_acc_proof('role1')
     self.assertEqual(snapshot_info['version'], 1)
 
-    # verify merkle path with invalid role
+    # verify RSA accumulator with invalid role
     self.assertRaises(tuf.exceptions.NoWorkingMirrorError,
-        repository_updater.verify_merkle_path, 'foo')
+        repository_updater.verify_rsa_acc_proof, 'foo')
 
-    # Test get_one_valid_targetinfo with snapshot merkle
+    # Test get_one_valid_targetinfo with snapshot RSA accumulator
     repository_updater.get_one_valid_targetinfo('file1.txt')
 
 

tuf/client/updater.py

@@ -1081,9 +1081,9 @@ def refresh(self, unsafely_update_root_if_necessary=True):
     # require strict checks on its required length.
     self._update_metadata('timestamp', DEFAULT_TIMESTAMP_UPPERLENGTH)
 
-    if 'merkle_root' not in self.metadata['current']['timestamp']:
-      # If merkle root is set, do not update snapshot metadata. Instead,
-      # we will download the relevant merkle path later when downloading
+    if 'rsa_acc' not in self.metadata['current']['timestamp']:
+      # If an RSA Accumulator is defined, do not update snapshot metadata. Instead,
+      # we will download the relevant proof files later when downloading
       # a target.
       self._update_metadata_if_changed('snapshot',
           referenced_metadata='timestamp')
@@ -1489,11 +1489,6 @@ def _get_metadata_file(self, metadata_role, remote_filename,
         The expected and required version number of the 'metadata_role' file
         downloaded.  'expected_version' is an integer.
 
-      snapshot_merkle:
-        Is the metadata file a snapshot merkle file? Snapshot merkle files
-        are not signed and so should skip some of the verification steps here.
-        Instead, they must be verified using verify_merkle_path.
-
     <Exceptions>
       tuf.exceptions.NoWorkingMirrorError:
         The metadata could not be fetched. This is raised only when all known
@@ -1631,29 +1626,29 @@ def signable_verification(self, metadata_role, file_object, expected_version):
 
 
 
-  def _update_merkle_metadata(self, merkle_filename, upperbound_filelength,
+  def _update_rsa_acc_metadata(self, proof_filename, upperbound_filelength,
       version=None):
     """
     <Purpose>
-      Non-public method that downloads, verifies, and 'installs' the merkle
-      metadata belonging to 'merkle_filename'.  Calling this method implies
-      that the 'merkle_filename' on the repository is newer than the client's,
+      Non-public method that downloads, verifies, and 'installs' the proof
+      metadata belonging to 'proof_filename'.  Calling this method implies
+      that the 'proof_filename' on the repository is newer than the client's,
       and thus needs to be re-downloaded.  The current and previous metadata
       stores are updated if the newly downloaded metadata is successfully
       downloaded and verified.  This method also assumes that the store of
       top-level metadata is the latest and exists.
 
     <Arguments>
-      merkle_filename:
-        The name of the metadata. This is a merkle tree file and should
-        not end in '.json'.  Examples: 'role1-merkle', 'targets-merkle'
+      proof_filename:
+        The name of the metadata. This is an RSA accumulator proof file and should
+        not end in '.json'.  Examples: 'role1-snapshot', 'targets-snapshot'
 
       upperbound_filelength:
         The expected length, or upper bound, of the metadata file to be
         downloaded.
 
       version:
-        The expected and required version number of the 'merkle_filename' file
+        The expected and required version number of the 'proof_filename' file
         downloaded.  'version' is an integer.
 
     <Exceptions>
@@ -1663,7 +1658,7 @@ def _update_merkle_metadata(self, merkle_filename, upperbound_filelength,
         metadata have been tried and failed.
 
     <Side Effects>
-      The metadata file belonging to 'merkle_filenaem' is downloaded from a
+      The metadata file belonging to 'proof_filename' is downloaded from a
       repository mirror.  If the metadata is valid, it is stored in the
       metadata store.
 
@@ -1673,7 +1668,7 @@ def _update_merkle_metadata(self, merkle_filename, upperbound_filelength,
 
     # Construct the metadata filename as expected by the download/mirror
     # modules.
-    metadata_filename = merkle_filename + '.json'
+    metadata_filename = proof_filename + '.json'
 
     # Attempt a file download from each mirror until the file is downloaded and
     # verified.  If the signature of the downloaded file is valid, proceed,
@@ -1703,7 +1698,7 @@ def _update_merkle_metadata(self, merkle_filename, upperbound_filelength,
     verification_fn = None
 
     metadata_file_object = \
-      self._get_metadata_file(merkle_filename, remote_filename,
+      self._get_metadata_file(proof_filename, remote_filename,
         upperbound_filelength, version, verification_fn)
 
     # The metadata has been verified. Move the metadata file into place.
@@ -1732,16 +1727,16 @@ def _update_merkle_metadata(self, merkle_filename, upperbound_filelength,
 
     # Extract the metadata object so we can store it to the metadata store.
     # 'current_metadata_object' set to 'None' if there is not an object
-    # stored for 'merkle_filename'.
-    current_metadata_object = self.metadata['current'].get(merkle_filename)
+    # stored for 'proof_filename'.
+    current_metadata_object = self.metadata['current'].get(proof_filename)
 
     # Finally, update the metadata and fileinfo stores, and rebuild the
-    # key and role info for the top-level roles if 'merkle_filename' is root.
+    # key and role info for the top-level roles if 'proof_filename' is root.
     # Rebuilding the key and role info is required if the newly-installed
     # root metadata has revoked keys or updated any top-level role information.
     logger.debug('Updated ' + repr(current_filepath) + '.')
-    self.metadata['previous'][merkle_filename] = current_metadata_object
-    self.metadata['current'][merkle_filename] = updated_metadata_object
+    self.metadata['previous'][proof_filename] = current_metadata_object
+    self.metadata['current'][proof_filename] = updated_metadata_object
 
 
 
@@ -1865,39 +1860,52 @@ def _update_metadata(self, metadata_role, upperbound_filelength, version=None):
 
 
 
-  def verify_merkle_path(self, metadata_role, version=None, merkle_root=None):
+  def verify_rsa_acc_proof(self, metadata_role, version=None, rsa_acc=None):
     """
     <Purpose>
-      Download the merkle path associated with metadata_role and verify the hashes.
+      Download the RSA accumulator proof associated with metadata_role and verify the hashes.
     <Arguments>
       metadata_role:
         The name of the metadata role. This should not include a file extension.
     <Exceptions>
       tuf.exceptions.RepositoryError:
-        If the snapshot merkle file is invalid or the verification fails
+        If the snapshot rsa accumulator file is invalid or the verification fails
     <Returns>
       A dictionary containing the snapshot information about metadata role,
       conforming to VERSIONINFO_SCHEMA or METADATA_FILEINFO_SCHEMA
     """
-    if not merkle_root:
-      merkle_root = self.metadata['current']['timestamp']['merkle_root']
+
+    # Modulus from https://en.wikipedia.org/wiki/RSA_numbers#RSA-2048
+    # We will want to generate a new one
+    # This is duplicate code from repo lib, should live somewhere else
+    Modulus = "2519590847565789349402718324004839857142928212620403202777713783604366202070759555626401852588078" + \
+      "4406918290641249515082189298559149176184502808489120072844992687392807287776735971418347270261896375014971" + \
+      "8246911650776133798590957000973304597488084284017974291006424586918171951187461215151726546322822168699875" + \
+      "4918242243363725908514186546204357679842338718477444792073993423658482382428119816381501067481045166037730" + \
+      "6056201619676256133844143603833904414952634432190114657544454178424020924616515723350778707749817125772467" + \
+      "962926386356373289912154831438167899885040445364023527381951378636564391212010397122822120720357"
+    m = int(Modulus, 10)
+
+
+    if not rsa_acc:
+      rsa_acc = self.metadata['current']['timestamp']['rsa_acc']
 
     metadata_rolename = metadata_role + '-snapshot'
 
-    # Download Merkle path
+    # Download RSA accumulator proof
     upperbound_filelength = tuf.settings.MERKLE_FILELENGTH
-    self._update_merkle_metadata(metadata_rolename, upperbound_filelength, version)
+    self._update_rsa_acc_metadata(metadata_rolename, upperbound_filelength, version)
     metadata_directory = self.metadata_directory['current']
     metadata_filename = metadata_rolename + '.json'
     metadata_filepath = os.path.join(metadata_directory, metadata_filename)
 
     # Ensure the metadata path is valid/exists, else ignore the call.
     if not os.path.exists(metadata_filepath):
-      # No merkle path found
-      raise tuf.exceptions.RepositoryError('No snapshot merkle file for ' +
+      # No RSA accumulator proof found
+      raise tuf.exceptions.RepositoryError('No snapshot rsa accumulator proof file for ' +
           metadata_role)
     try:
-      snapshot_merkle = securesystemslib.util.load_json_file(
+      snapshot_rsa_acc_proof = securesystemslib.util.load_json_file(
           metadata_filepath)
 
     # Although the metadata file may exist locally, it may not
@@ -1907,46 +1915,23 @@ def verify_merkle_path(self, metadata_role, version=None, merkle_root=None):
     except securesystemslib.exceptions.Error:
       return
 
-    # verify the Merkle path
-    tuf.formats.SNAPSHOT_MERKLE_SCHEMA.check_match(snapshot_merkle)
+    # check the format
+    tuf.formats.SNAPSHOT_RSA_ACC_SCHEMA.check_match(snapshot_rsa_acc_proof)
 
-    # hash the contents to determine the leaf hash in the merkle tree
-    contents = snapshot_merkle['leaf_contents']
+    # canonicalize the contents to determine the RSA accumulator prime
+    contents = snapshot_rsa_acc_proof['leaf_contents']
     json_contents = securesystemslib.formats.encode_canonical(contents)
-    digest_object = securesystemslib.hash.digest()
-    digest_object.update((json_contents).encode('utf-8'))
-    node_hash = "a" + digest_object.hexdigest()
-
-    # For each hash in the merkle_path, determine if the current node is
-    # a left of a right node using the path_directions, then combine
-    # the hash from merkle_path with the current node_hash to determine
-    # the next node_hash. At the end, the node_hash should match the hash
-    # in merkle_root
-    merkle_path = snapshot_merkle['merkle_path']
-    path_directions = snapshot_merkle['path_directions']
-
-    # If merkle_path and path_directions have different lengths,
-    # the verification will not be possible
-    if len(merkle_path) != len(path_directions):
-      raise tuf.exceptions.RepositoryError('Invalid merkle path for ' +
-          metadata_role)
 
-    for index in range(len(merkle_path)):
-      i = str(index)
-      if path_directions[i] < 0:
-        # The current node is a left node
-        digest_object = securesystemslib.hash.digest()
-        digest_object.update((node_hash + merkle_path[i]).encode('utf-8'))
-      else:
-        # The current node is a right node
-        digest_object = securesystemslib.hash.digest()
-        digest_object.update((merkle_path[i] + node_hash).encode('utf-8'))
-      node_hash = "b" + digest_object.hexdigest()
+    prime = repository_lib.hash_to_prime(json_contents)
+
+    # RSA accumulator proof
+    proof = snapshot_rsa_acc_proof['rsa_acc_proof']
+    rsa_acc_proof_test = pow(proof, prime, m)
 
-    # Does the result match the merkle root?
-    if node_hash != merkle_root:
-      raise tuf.exceptions.RepositoryError('The merkle root ' + merkle_root +
-          ' does not match the hash ' + node_hash + ' for ' + metadata_role)
+    # Does the result match the RSA accumulator?
+    if rsa_acc_proof_test != rsa_acc:
+      raise tuf.exceptions.RepositoryError('RSA accumulator ' + rsa_acc +
+          ' does not match the proof ' + proof + ' for ' + metadata_role)
 
     # return the verified snapshot contents
     return contents
@@ -2025,9 +2010,9 @@ def _update_metadata_if_changed(self, metadata_role,
 
     # Ensure the referenced metadata has been loaded.  The 'root' role may be
     # updated without having 'snapshot' available.
-    # When snapshot merkle trees are used, there will not be a snapshot file.
-    # Instead, if the snapshot merkle file is missing, this will error below.
-    if 'merkle_root' not in self.metadata['current']['timestamp'] and referenced_metadata not in self.metadata['current']:
+    # When a snapshot rsa accumulator is used, there will not be a snapshot file.
+    # Instead, if the snapshot rsa proof is missing, this will error below.
+    if 'rsa_acc' not in self.metadata['current']['timestamp'] and referenced_metadata not in self.metadata['current']:
       raise tuf.exceptions.RepositoryError('Cannot update'
         ' ' + repr(metadata_role) + ' because ' + referenced_metadata + ' is'
         ' missing.')
@@ -2039,9 +2024,9 @@ def _update_metadata_if_changed(self, metadata_role,
         repr(referenced_metadata)+ '.  ' + repr(metadata_role) +
         ' may be updated.')
 
-    if 'merkle_root' in self.metadata['current']['timestamp']:
-      # Download version information from merkle tree
-      contents = self.verify_merkle_path(metadata_role)
+    if 'rsa_acc' in self.metadata['current']['timestamp']:
+      # Download version information from RSA accumulator proof
+      contents = self.verify_rsa_acc_proof(metadata_role)
       expected_versioninfo = contents
 
     else:
@@ -2621,10 +2606,10 @@ def _refresh_targets_metadata(self, rolename='targets',
 
     roles_to_update = []
 
-    # Add the role if it is listed in snapshot. If snapshot merkle
-    # trees are used, the snapshot check will be done later when
-    # the merkle tree is verified
-    if 'merkle_root' in self.metadata['current']['timestamp'] or rolename + '.json' in self.metadata['current']['snapshot']['meta']:
+    # Add the role if it is listed in snapshot. If a snapshot rsa
+    # accumulator is used, the snapshot check will be done later when
+    # the proof is verified
+    if 'rsa_acc' in self.metadata['current']['timestamp'] or rolename + '.json' in self.metadata['current']['snapshot']['meta']:
       roles_to_update.append(rolename)
 
     if refresh_all_delegated_roles: