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[Bug libc/15813] Multiple issues in __gen_tempname


https://sourceware.org/bugzilla/show_bug.cgi?id=15813

Ondrej Bilka <neleai at seznam dot cz> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |neleai at seznam dot cz
           Severity|normal                      |enhancement

--- Comment #1 from Ondrej Bilka <neleai at seznam dot cz> ---
I do not see how could attacker use __gen_tempname weakness, worst he could do
is dos/ cause mkxtemp to fail which should be handled correctly. If you want
this fixed write a patch.

keeping value is more entropic than calculating anew as entropy of sum of
uncorrelated variables is at least maximum of entropies of variables. Without
that we would call clock_gettime twice in quick succession which has almost
same entropy as calling it once.

As __gen_tempname call does disk access we can affort on linux just read 64bits
from /dev/urandom.

If attacker can guess that we have bigger worries than temporary files.

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