#833: reject mutable children when *reading* an immutable dirnode
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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:
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Comment(by davidsarah):
Overnight I thought of the following additional option, which has similar
forward-compatibility advantages to FORWARD_COMPAT_METADATA but has fewer
constraints on the future URL design:
* PREFIXED_RO_URI: include a directory entry for an unknown child link of
an immutable directory, but prefix {{{ro_uri}}} with "{{{imm.}}}" (and
omit {{{rw_uri}}}).
Note that this doesn't imply that the new format would have to use
"{{{imm.}}}" -- that prefix would ''only'' occur on URLs from the past.
When we add support for the new format, the future client would see the
"{{{imm.}}}" prefix and check that the cap is immutable; if it is then it
would work correctly.
(We might end up registering both "{{{lafs:}}}" and "{{{imm.lafs:}}}" in
order to make this work in more cases, but I don't think that's a problem,
and it's not strictly necessary. Anyway, there are already
[http://www.iana.org/assignments/uri-schemes.html URI schemes] containing
'{{{.}}}'.)
In retrospect this is similar to something Zooko suggested on IRC ('mangle
the cap by prepending "I'M NOT REALLY A CAP"'), except that "{{{imm.}}}"
just means that the future client must check that it is an immutable cap.
The effect of prepending "{{{imm.}}}" with the current webapi is to
display {{{"GET unknown: can only do t=info, not t="}}}, which is safe but
ugly. We should fix that (it's ticket #884).
--
Ticket URL: <http://allmydata.org/trac/tahoe/ticket/833#comment:21>
tahoe-lafs <http://allmydata.org>
secure decentralized file storage grid
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