[tahoe-dev] [tahoe-lafs] #833: reject mutable children when *reading* an immutable dirnode

[tahoe-lafs]

#833: reject mutable children when *reading* an immutable dirnode
---------------------------------------------+------------------------------
 Reporter:  warner                           |           Owner:  warner  
     Type:  defect                           |          Status:  assigned
 Priority:  critical                         |       Milestone:  1.6.0   
Component:  code-dirnodes                    |         Version:  1.5.0   
 Keywords:  integrity forward-compatibility  |   Launchpad_bug:          
---------------------------------------------+------------------------------

Comment(by zooko):

 So in addition to whatever plan we settle on for reliably excluding known-
 mutable children, is there any use in predicting what format caps from the
 future might use to indicate read-only, read-write, and immutable?  In my
 Tahoe-LAFS plugin for TiddlyWiki I made it recognize the current cap
 format and also:

 {{{
 // This is speculative: maybe in the future there will be a version of
 Tahoe where caps
 // start with these symbols, and if so then this JavaScript code will
 magically work with
 // that version of Tahoe.
 TAHOE_FUTURE_IMMUTABLE_CAP_RE_STR = "i_" + ALPHANUMERIC_STRING;
 TAHOE_FUTURE_READONLY_CAP_RE_STR = "r_" + ALPHANUMERIC_STRING;
 TAHOE_FUTURE_WRITABLE_CAP_RE_STR = "W_" + ALPHANUMERIC_STRING;
 }}}

 http://allmydata.org/source/tiddly_on_tahoe/trunk/tahoe_tiddly/TahoePlugin.js

 I'm not sure that does any good, in particular because we may end up using
 different indicators for cap-type, maybe in part because having a
 separator char there, while good for human eyeballs, is bad for selecting
 with double-click of a mouse...

 Anyway, if you could think for a minute about forward-compatibility and
 make sure that such things are not of use in this case and state
 conclusively that Tahoe-LAFS v1.6 should treat ''all'' unrecognized caps
 (whether from the future, corrupted, or malicious) that it finds as the
 children of immutable directories as mutable and unreadable that would
 make me feel better.  :-)

-- 
Ticket URL: <http://allmydata.org/trac/tahoe/ticket/833#comment:12>
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