[GHC] #8058: If .ghci is a symlink, permissions aren't read correctly

[GHC]

#8058: If .ghci is a symlink, permissions aren't read correctly
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        Reporter:  berdario    |            Owner:
            Type:  bug         |           Status:  new
        Priority:  low         |        Milestone:
       Component:  GHCi        |          Version:  7.6.2
      Resolution:              |         Keywords:
Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple             |       Difficulty:  Easy (less than 1 hour)
 Type of failure:  Other       |       Blocked By:
       Test Case:              |  Related Tickets:
        Blocking:              |
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Comment (by berdario):

 {{{
 dario at macbook ~> ls -l .ghci lrwxrwxrwx 1 dario dario 40 Jul 14 15:27
 .ghci -> /home/dario/.dotfiles/dotfiles/ghci.conf
 dario at macbook ~> ls -l (readlink -f .ghci) -rw-r--r-- 1 dario dario 10 Jul
 14 15:25 /home/dario/.dotfiles/dotfiles/ghci.conf
 dario at macbook ~> ghci GHCi, version 7.6.2: http://www.haskell.org/ghc/ :?
 for help
 Loading package ghc-prim ... linking ... done.
 Loading package integer-gmp ... linking ... done.
 Loading package base ... linking ... done.
 *** WARNING: /home/dario/.dotfiles/dotfiles is writable by someone else,
 IGNORING!
 Prelude>
 }}}

 Obviously, /home/dario/.dotfiles/dotfiles isn't writable by someone
 else...

 Someone else could actually delete the symlink and maybe recreate it...
 but it couldn't inject malicious commands in the .ghci, unless the file
 pointed by the symlink was also writable by the attacker, in which case,
 checking the permissions of the target of the symlink would still prevent
 any wrongdoing

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8058#comment:1>
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