Allows to check multi trusted certificates.

Actually, the user can configure the buildout.cfg and set multiples
certificates files.

It means that libnetworkcache must be able to check if the signature
which comes from shadir is trustable or not, based on these certificates.

A given signature can not appear twice in the same directory-key, if it
happens a DiretoryNotFound error must be raised.

slapos/libnetworkcache.py

@@ -24,7 +24,7 @@ import urlparse
 import M2Crypto
 
 
-_MARKER = (None, '')
+_MARKER = ([], [''], None, '')
 
 
 class NetworkcacheClient(object):
@@ -53,7 +53,8 @@ class NetworkcacheClient(object):
     return return_dict
 
   def __init__(self, shacache, shadir,
-               signature_private_file=None, signature_public_file=None):
+               signature_private_key_file=None,
+               signature_certificate_file_list=None):
     ''' Set the initial values. '''
     # ShaCache Properties
     for k, v in self.parseUrl(shacache).iteritems():
@@ -64,8 +65,8 @@ class NetworkcacheClient(object):
     for k, v in self.parseUrl(shadir).iteritems():
       setattr(self, 'shadir_%s' % k, v)
 
-    self.signature_private_file = signature_private_file
-    self.signature_public_file = signature_public_file
+    self.signature_private_key_file = signature_private_key_file
+    self.signature_certificate_file_list = signature_certificate_file_list
 
   def upload(self, file_descriptor, directory_key=None, **kw):
     ''' Upload the file to the server.
@@ -163,52 +164,56 @@ class NetworkcacheClient(object):
     if result.status != 200:
       raise DirectoryNotFound(result.read())
 
+    # Filtering...
     data_list = json.loads(data)
-    if len(data_list) > 1 and self.signature_public_file in _MARKER:
+    if len(data_list) > 1 and self.signature_certificate_file_list in _MARKER:
       raise DirectoryNotFound('Too many entries for a given directory. ' \
                'Directory: %s. Entries: %s.' % (directory_key, str(data_list)))
 
-    sha512 = None
-    if self.signature_public_file not in _MARKER:
-      for information_dict, signature in data_list:
-        if self._verifySignature(signature):
-          sha512 = information_dict.get('sha512')
-          break
-      if sha512 is None:
-        raise DirectoryNotFound('Could not find a trustable entry.')
+    if self.signature_certificate_file_list not in _MARKER:
+      method = self._verifySignatureInCertificateList
+      data_list = filter(lambda x: method(x[1]), data_list)
+      if len(data_list) > 1:
+        raise DirectoryNotFound('Too many entries for a given key. ' \
+               'Directory: %s. Entries: %s.' %(directory_key, str(data_list)))
 
-    else:
-      information_dict, signature = data_list[0]
-      sha512 = information_dict.get('sha512')
+      if not data_list:
+        raise DirectoryNotFound('Could not find a trustable entry.')
 
+    information_dict, signature = data_list[0]
+    sha512 = information_dict.get('sha512')
     return self.download(sha512)
 
   def _getSignatureString(self):
     """
       Return the signature based on certification file.
     """
-    if self.signature_private_file in _MARKER:
+    if self.signature_private_key_file in _MARKER:
       return ''
 
-    SignEVP = M2Crypto.EVP.load_key(self.signature_private_file)
+    SignEVP = M2Crypto.EVP.load_key(self.signature_private_key_file)
     SignEVP.sign_init()
     SignEVP.sign_update('')
     StringSignature = SignEVP.sign_final()
     return StringSignature.encode('base64')
 
-  def _verifySignature(self, signature_string):
+  def _verifySignatureInCertificateList(self, signature_string):
     """
-      Check if the signature is valid.
+      Returns true if it can find any valid certificate.
     """
-    if self.signature_public_file in _MARKER:
+    if self.signature_certificate_file_list in _MARKER:
       return 0
 
-    PubKey = M2Crypto.X509.load_cert(self.signature_public_file)
-    VerifyEVP = M2Crypto.EVP.PKey()
-    VerifyEVP.assign_rsa(PubKey.get_pubkey().get_rsa())
-    VerifyEVP.verify_init()
-    VerifyEVP.verify_update('')
-    return VerifyEVP.verify_final(signature_string.decode('base64'))
+    for certificate_path in self.signature_certificate_file_list:
+      PubKey = M2Crypto.X509.load_cert(certificate_path)
+      VerifyEVP = M2Crypto.EVP.PKey()
+      VerifyEVP.assign_rsa(PubKey.get_pubkey().get_rsa())
+      VerifyEVP.verify_init()
+      VerifyEVP.verify_update('')
+      if VerifyEVP.verify_final(signature_string.decode('base64')):
+        return True
+
+    return False
 
 
 class DirectoryNotFound(Exception):