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author | Thomas Schwinge <thomas@codesourcery.com> | 2012-05-24 23:08:09 +0200 |
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committer | Thomas Schwinge <thomas@codesourcery.com> | 2012-05-24 23:08:09 +0200 |
commit | 2910b7c5b1d55bc304344b584a25ea571a9075fb (patch) | |
tree | bfbfbc98d4c0e205d2726fa44170a16e8421855e /open_issues/dir-lookup_authority.mdwn | |
parent | 35b719f54c96778f571984065579625bc9f15bf5 (diff) |
Prepare toolchain/logs/master branch.
Diffstat (limited to 'open_issues/dir-lookup_authority.mdwn')
-rw-r--r-- | open_issues/dir-lookup_authority.mdwn | 68 |
1 files changed, 0 insertions, 68 deletions
diff --git a/open_issues/dir-lookup_authority.mdwn b/open_issues/dir-lookup_authority.mdwn deleted file mode 100644 index 64866eb5..00000000 --- a/open_issues/dir-lookup_authority.mdwn +++ /dev/null @@ -1,68 +0,0 @@ -[[!meta copyright="Copyright © 2010 Free Software Foundation, Inc."]] - -[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable -id="license" text="Permission is granted to copy, distribute and/or modify this -document under the terms of the GNU Free Documentation License, Version 1.2 or -any later version published by the Free Software Foundation; with no Invariant -Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license -is included in the section entitled [[GNU Free Documentation -License|/fdl]]."]]"""]] - -[[!tag open_issue_hurd]] - -IRC, unknown channel, unknown date. - - <cfhammar> I have discovered a bug in the dir-lookup protocol though - <cfhammar> Currently, I'm investigating the bug a bit further - <cfhammar> when doing dir-lookups with several path components, the look-up is done with the authority of the user who opened the directory, as opposed to the user doing the lookup - <cfhammar> e.g, consider foo/bar/baz, where bar can only be used by its owner and foo and baz are world readable - <cfhammar> if foo is opened, then transferred to another user, he can open baz, which he shouldn't be able to - <cfhammar> this is possible where foo/bar/baz is within a single translator, and the lookup is done in a single dir-lookup - <antrik> cfhammar: I'm not sure this is a bug - <cfhammar> I have a test case that triggers the bug, and another that doesn't which currently confuses me - <antrik> cfhammar: it's probably not very usual to pass around open directory ports; but if somebody does it, it's probably actually desired that it keeps the authority - <antrik> it's kinda consistent with passing normal FDs - <cfhammar> antrik: it should only allow accesses to entries not sub-entries - <cfhammar> antrik: it isn't allowed in Linux atleast, and I'm guessing it's mandated by posix - <cfhammar> also note that a more common scenario is a process that opens a directory and then drops authority - <cfhammar> probably more common, that is - <antrik> cfhammar: I'm not really familiar with directory access functions... I wasn't even aware that it's possible to pass around directory FDs - <antrik> but if it is, it would indeed be good to know what POSIX says about this - <antrik> cfhammar: I don't see how this is related?... - <cfhammar> antrik: after the process has dropped authority it can still make lookups in directories that it should no longer be able to - <antrik> cfhammar: interesting point... - <antrik> cfhammar: do you think this is fixable? - <cfhammar> antrik: Not without (defacto) changing the interface - <cfhammar> e.g only looking up a singe path component at a time - <cfhammar> or doing the auth check lazily on io_reauthenticate - <antrik> cfhammar: yeah, obviously it's not possible without an API change. I just wonder whether it's possible without throwing the current auth/lookup mechanism overboard alltogether... - <cfhammar> antrik: both my solutions are only minor changes to the API, but fairly major in the sense that we need to change all callers :-( - <cfhammar> diskfs_S_dir_lookup is a very large function, for example - <antrik> cfhammar: OK - <antrik> cfhammar: I wonder whether there is a possible transition path without breaking all existing installations... - <cfhammar> we could provide a new RPC while supporting the old one - <cfhammar> note that changing fs.defs only affects glibc and the Hurd, normal apps should be fine - <antrik> cfhammar: have you posted your findings to the ML yet? - <cfhammar> No, I'm still investigating why my second test-case doesn't trigger the bug - <cfhammar> Intrestingly it's the one using all POSIX functions... - <cfhammar> Perhaps its a bug that maskes the lookup bug ;-) - <antrik> I guess there is some quirk which you do not fully understand yet :-) - <cfhammar> Oh, there's always a new quirk to find in the Hurd :-) - <cfhammar> antrik: seems that dir_lookup isn't buggy after all - <cfhammar> antrik: as all FDs are reauthenticated on setauth - <antrik> ah - <cfhammar> antrik: and (presumably) ports are unauthenticated and reauthenticated when transfered - <antrik> yeah, that's the idea behind the auth protocol... - <antrik> users obtain specific capabilities by authenticating generic ports against their own ID - <cfhammar> I didn't really have a coherent view on how open flags are handled on reauth - <cfhammar> it seems open flags always win, so that a O_READ port that is unauthed is still readable - <antrik> not sure what you mean - <cfhammar> if I open a file to read it, then reauth it with a user that isn't permitted to read it, I can still read from it - <cfhammar> (as it should be) - <cfhammar> by contrast permission to do lookups in a directory is determined by who authed it - <cfhammar> so I won't be able to do lookups after a reauth, if it's not permitted by the file bits - <youpi> Mmm, openat should however be able to - <youpi> since you've first opened the directory with the auth - <cfhammar> it isn't since open FDs are reauthed on setauth - <cfhammar> not sure whether it should though, Linux behaves the same way atleast - <cfhammar> though it could be done with POSIX.2008's O_SEARCH open flag |