[tor-bugs] #13214 [Tor]: HS clients don't validate descriptor-id returned by HSDir

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#13214: HS clients don't validate descriptor-id returned by HSDir
---------------------+---------------------
 Reporter:  special  |          Owner:
     Type:  defect   |         Status:  new
 Priority:  normal   |      Milestone:
Component:  Tor      |        Version:
 Keywords:  tor-hs   |  Actual Points:
Parent ID:           |         Points:
---------------------+---------------------
 The rend descriptor cache for clients uses the permanent hostname as a
 key, instead of the descriptor-id (changed every 24 hours). When a
 descriptor is returned from a HSDir, the response is kept if the permanent
 hostname matches. The descriptor-id is not compared to the original
 request.

 {{{
 switch (rend_cache_store_v2_desc_as_client(body, conn->rend_data)) {
 ...
 rend_client_desc_trynow(conn->rend_data->onion_address);
 }}}

 HS descriptors are currently valid for 3 days (#13207). A HSDir could
 fetch and serve a days-old descriptor for the same service, and that
 response will be used by clients.

 There is no denial of service; the client will fetch from another
 directory after all introductions fail. The worst effect I can see is that
 a HSDir could briefly distract clients by serving a very old descriptor.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13214>
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