[Monotone-devel] popen from a hook

[William Uther]

Hi,
  After a bit of digging I discovered that io.popen has been  
disabled in mtn's lua because it is considered a security risk (if  
you pass a file name into it, then it might do weird things in the  
shell).  I find this ironic, because the workaround for lack of a  
popen in my use-case is to save a password to a file in cleartext...  
also a security a risk.

  So, I've made two patches.  The first does two things:
   - adds some error messages to make it clear that popen was  
deliberately disabled.
   - leaves io.unsafepopen as a replacement for popen.  This makes  
it clear that it is considered a security risk in some situations,  
but allows its use where there is no security problem (e.g. if you're  
not passing versioned filenames on the command line).

  The second version leaves 'popen' available unrenamed, but wraps  
it in a fairly strict check to make sure it isn't a security hole (no  
characters except [a-zA-Z0-9 ] are allowed in the command).

  You only need to apply one of these patches.  If you apply both,  
they'll conflict :).

Be well,

Will       :-}

lua_hooks.cc-1.diff
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lua_hooks.cc-2.diff
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