[GHC] #10940: Random number chosen by openTempFile is always 1804289383846930886

[GHC]

#10940: Random number chosen by openTempFile is always 1804289383846930886
-------------------------------------+-------------------------------------
           Reporter:  andersk        |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:                 |           Version:  7.10.2
  libraries/base                     |
           Keywords:                 |  Operating System:  Linux
       Architecture:                 |   Type of failure:  Incorrect result
  Unknown/Multiple                   |  at runtime
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |
-------------------------------------+-------------------------------------
 {{{#!hs
 import System.Directory
 import System.IO
 main = do
   (p, _) <- openTempFile "/tmp" ""
   print p
   removeFile p
 }}}

 {{{#!console
 $ runghc temp.hs
 "/tmp/1804289383846930886"
 $ runghc temp.hs
 "/tmp/1804289383846930886"
 $ runghc temp.hs
 "/tmp/1804289383846930886"
 $ runghc temp.hs
 "/tmp/1804289383846930886"
 }}}

 This “random” number is the concatenation of the first two numbers
 1804289383, 846930886 returned by glibc’s `rand()` when not seeded (or
 seeded with 1).

 This is not immediately a library security bug, I think: the file is
 created with `O_EXCL`, and if it already exists, `openTempFile` will move
 onto the next value 16816927771714636915, and so on.  However, the
 predictable filenames make a potential application security bug that much
 more likely.

 (For your amusement, [https://www.google.com/search?q=1804289383846930886
 Google 1804289383846930886].)

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10940>
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