[tahoe-lafs-trac-stream] [tahoe-lafs] #795: add-only sets

[tahoe-lafs]

#795: add-only sets
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     Reporter:  warner        |      Owner:
         Type:  enhancement   |     Status:  new
     Priority:  major         |  Milestone:  undecided
    Component:  code-mutable  |    Version:  1.5.0
   Resolution:                |   Keywords:  newcaps revocation research
Launchpad Bug:                |
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Comment (by joepie91):

 While #796 is my particular usecase, this seems to be the canonical thread
 for the base implementation, so I'll comment here; I was also looking for
 write-only caps (in particular append-only directories where you can only
 append files and not change, move/rename or remove files), for a write-
 only backup mechanism where no single server has the ability to remove any
 backups.

 In my case, the threat model would be an attacker gaining (full or
 partial) access to a server that is being automatically backed up with
 Duplicity, intending to irrevocably wipe all data he can. A write-only cap
 would make the attacker unable to remove existing backups; only I
 personally would be able to do so, using a writecap that is not stored on
 any server.

 I should also note that there'd be a potential confidentiality issue with
 non-read write-only caps (that I expect at least zooko to have already
 thought of): if you have a cap that is supposedly intended to prevent any
 discovery of data (including a directory listing), how would you reject an
 attempt at overwriting an entry (ie. a conflict) without revealing that
 the original entry exists, thus causing an information leak and
 confidentiality breach?

 Either way, I very strongly +1 this write-only-cap suggestion - and I
 believe 'appendcap' would be an apt name for it :)

-- 
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/795#comment:14>
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