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Fix bug in mpi_tdiv_q_2exp.

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* mpi/mpi-internal.h (MPN_COPY_INCR): Make it work.
--

This bug has been with us since the version 0.0.0 of GnuPG.
Fortunately it only affects an optimized code path which is rarely
used in practice: If the shift size matches the size of a
limb (i.e.. 32 or 64); this is is_prime in primegen.c.  Over there the
Rabin-Miller test may fail with a probability of 2^-31 (that is if the
to be tested prime - 1 has the low 32 bits cleared).  In practice the
probability is even much less because we first do a Fermat test on the
randomly generated candidates which sorts out the majority of
composite numbers.

The bug in MPN_COPY_INCR was found by Sven Bjorn.

Signed-off-by: Werner Koch <wk@gnupg.org>

(back ported from Libgcrypt
 commit 7f7a5ef59962ae1a819b5060f9b781469bfe27d5)
This commit is contained in:
Werner Koch 2013-09-16 15:57:01 +02:00
parent 45efde9557
commit 9dc6dd0572
1 changed files with 1 additions and 1 deletions
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2
mpi/mpi-internal.h
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@ -104,7 +104,7 @@ typedef int mpi_size_t; /* (must be a signed type) */
do { \ do { \
mpi_size_t _i; \ mpi_size_t _i; \
for( _i = 0; _i < (n); _i++ ) \ for( _i = 0; _i < (n); _i++ ) \
(d)[_i] = (d)[_i]; \ (d)[_i] = (s)[_i]; \
} while (0) } while (0)
#define MPN_COPY_DECR( d, s, n ) \ #define MPN_COPY_DECR( d, s, n ) \