[tor-bugs] #5810 [Stem]: Implement verification of server descriptor

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#5810: Implement verification of server descriptor
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 Reporter:  reganeet     |          Owner:  reganeet
     Type:  enhancement  |         Status:  new     
 Priority:  normal       |      Milestone:          
Component:  Stem         |        Version:          
 Keywords:               |         Parent:          
   Points:               |   Actualpoints:          
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 We need to implement is_valid() method of
 stem.descriptor.server_descriptor.!RelayDescriptor ![1] , to do some
 verifications on the descriptor:

   1) a contained fingerprint is actually a hash of the signing key and

   2) a router signature was created using the signing key.

 There's already Java code for doing this in metrics-tasks [2]. However,
 the Java code is a standalone test, while stem's implementation is self-
 contained within the descriptor.

 We need some ssl library to read the pem-format keys in descriptors, and
 M2Crypto seems to be the best choice [3]. The problem with M2Crypto is
 that it requires SSL_v2 support from openssl, which is considered unsafe
 thus excluded from recent Ubuntu releases, and possibly Debian [4]. I
 don't know how many people run Tor in Ubuntu, and whether we should let
 users responsible for having a complete openssl library. It seems quite
 hard to work this around on Ubuntu ![5].

 [1][https://gitweb.torproject.org/stem.git/blob/HEAD:/stem/descriptor/server_descriptor.py#l624
 :]https://gitweb.torproject.org/stem.git/blob/HEAD:/stem/descriptor/server_descriptor.py#l624

 [2]: https://gitweb.torproject.org/metrics-
 tasks.git/blob/HEAD:/task-2768/VerifyDescriptors.java

 [3]: http://stackoverflow.com/a/606702/994146

 [4]: http://stackoverflow.com/a/8219807/994146

 [5]: https://discussions.nessus.org/thread/3174

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/5810>
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