
MicroDescriptor
***************

Parsing for Tor microdescriptors, which contain a distilled version of
a relay's server descriptor. As of Tor version 0.2.3.3-alpha Tor no
longer downloads server descriptors by default, opting for
microdescriptors instead.

Unlike most descriptor documents these aren't available on the metrics
site (since they don't contain any information that the server
descriptors don't).

The limited information in microdescriptors make them rather clunky to
use compared with server descriptors. For instance microdescriptors
lack the relay's fingerprint, making it difficut to use them to look
up the relay's other descriptors.

To do so you need to match the microdescriptor's digest against its
corresponding router status entry. For added fun as of this writing
the controller doesn't even surface those router status entries
(ticket 7953).

For instance, here's an example that prints the nickname and
fignerprints of the exit relays.

   import os

   from stem.control import Controller
   from stem.descriptor import parse_file

   with Controller.from_port(port = 9051) as controller:
     controller.authenticate()

     exit_digests = set()
     data_dir = controller.get_conf('DataDirectory')

     for desc in controller.get_microdescriptors():
       if desc.exit_policy.is_exiting_allowed():
         exit_digests.add(desc.digest)

     print 'Exit Relays:'

     for desc in parse_file(os.path.join(data_dir, 'cached-microdesc-consensus')):
       if desc.digest in exit_digests:
         print '  %s (%s)' % (desc.nickname, desc.fingerprint)

Doing the same is trivial with server descriptors...

   from stem.descriptor import parse_file

   print 'Exit Relays:'

   for desc in parse_file('/home/atagar/.tor/cached-descriptors'):
     if desc.exit_policy.is_exiting_allowed():
       print '  %s (%s)' % (desc.nickname, desc.fingerprint)

**Module Overview:**

   Microdescriptor - Tor microdescriptor.

class class stem.descriptor.microdescriptor.Microdescriptor(raw_contents, validate=False, annotations=None)

   Bases: "stem.descriptor.Descriptor"

   Microdescriptor (descriptor specification)

   Variables:
      * **digest** (*str*) -- ***** hex digest for this
        microdescriptor, this can be used to match against the
        corresponding digest attribute of a "RouterStatusEntryMicroV3"

      * **onion_key** (*str*) -- ***** key used to encrypt EXTEND
        cells

      * **ntor_onion_key** (*str*) -- base64 key used to encrypt
        EXTEND in the ntor protocol

      * **or_addresses** (*list*) -- ***** alternative for our
        address/or_port attributes, each entry is a tuple of the form
        (address (**str**), port (**int**), is_ipv6 (**bool**))

      * **family** (*list*) -- ***** nicknames or fingerprints of
        declared family

      * **exit_policy** (*stem.exit_policy.MicroExitPolicy*) -- *****
        relay's exit policy

      * **exit_policy_v6** (*stem.exit_policy.MicroExitPolicy*) --
        ***** exit policy for IPv6

      * **identifier_type** (*str*) -- identity digest key type

      * **identifier** (*str*) -- base64 encoded identity digest, this
        is only used for collision prevention (ticket 11743)

   ***** attribute is required when we're parsed with validation

   Changed in version 1.1.0: Added the identifier and identifier_type
   attributes.

   get_annotations(*args, **kwds)

      Provides content that appeared prior to the descriptor. If this
      comes from the cached-microdescs then this commonly contains
      content like...

         @last-listed 2013-02-24 00:18:30

      Returns:
         **dict** with the key/value pairs in our annotations

   get_annotation_lines()

      Provides the lines of content that appeared prior to the
      descriptor. This is the same as the "get_annotations()" results,
      but with the unparsed lines and ordering retained.

      Returns:
         **list** with the lines of annotation that came before this
         descriptor
