bugThe GNU Hurd - Bugs: bug #26960, firmlink opens target with client...


bug #26960: firmlink opens target with client specified flags

Submitter:  Carl Fredrik Hammar <hammy>
Submitted:  Sat 04 Jul 2009 04:05:50 PM UTC
Category:  Hurd Servers Severity:  3 - Normal
Priority:  5 - Normal Item Group:  None
Status:  None Privacy:  Public
Assigned to:  None Originator Name: 
Open/Closed:  Open Reproducibility:  None
Size (loc):  None Planned Release:  None
Effort:  0.00
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Tue 20 Sep 2016 10:54:09 PM UTC, comment #1: 

Someone should write test cases for whether the patch causes problems with the following flags.

  • O_APPEND: Open a firmlink with O_APPEND and then use io_get_openmodes and verify that the O_APPEND bit is there.
  • O_NOATIME: Open a firmlink with O_NOATIME, use io_read, close the file_t and check that the atime of the target file remains unchanged.
  • others?

If the firmlink translator doesn't pass O_APPEND to the dir_lookup call, but its caller ends up doing another dir_lookup and setting O_APPEND there, then it's okay, provided that the RPC responses from the firmlink translator are such that the caller cannot expect the file_t to work right if it omits the second dir_lookup.

Kalle Olavi Niemitalo <kon>
Sat 04 Jul 2009 04:05:50 PM UTC, original submission:  

firmlink opens its target file with any client specified open
flags, except O_CREAT.  This makes it is possible for a client
to read or write to the target of a firmlink using the firmlink's
authority (io_restrict_auth is not enough).  It is also possible
for the client to halt firmlink's look-up midway through, using

A patch that fixes it has been attached.  Also a program that
exploits the security-hole, just run it on a firmlink to a target
that it should not be permitted to read.

Carl Fredrik Hammar <hammy>
Group Member


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Attach Files:

Attached Files
file #18368:  firmlink-read.c added by hammy (757B - text/x-csrc)


Depends on the following items: None found

Items that depend on this one: None found


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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2009-07-04 hammy Attached File- Added 0001-Don-t-pass-client-flags-to-internal-firmlink-look-up.patch, #18367
        Attached File- Added firmlink-read.c, #18368

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