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-rw-r--r--mpi/mpih-const-time.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/mpi/mpih-const-time.c b/mpi/mpih-const-time.c
index 5ebb8d11..96899505 100644
--- a/mpi/mpih-const-time.c
+++ b/mpi/mpih-const-time.c
@@ -170,12 +170,13 @@ _gcry_mpih_mod (mpi_ptr_t vp, mpi_size_t vsize,
mpi_limb_t limb = vp[limbno];
unsigned int the_bit = ((limb & (A_LIMB_1 << bitno)) ? 1 : 0);
mpi_limb_t underflow;
+ mpi_limb_t overflow;
- _gcry_mpih_lshift (rp, rp, usize, 1);
+ overflow = _gcry_mpih_lshift (rp, rp, usize, 1);
rp[0] |= the_bit;
underflow = _gcry_mpih_sub_n (rp, rp, up, usize);
- mpih_add_n_cond (rp, rp, up, usize, underflow);
+ mpih_add_n_cond (rp, rp, up, usize, overflow ^ underflow);
}
return rp;