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Use mbedtls_mpi_core_sub_int() in mbedtls_mpi_sub_abs()

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Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
This commit is contained in:
Tom Cosgrove 2022-08-25 10:07:07 +01:00
parent f7ff4c9a11
commit 452c99c173
1 changed files with 5 additions and 7 deletions
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12
library/bignum.c
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@ -968,17 +968,15 @@ int mbedtls_mpi_sub_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
carry = mbedtls_mpi_core_sub( X->p, A->p, B->p, n );
if( carry != 0 )
{
/* Propagate the carry to the first nonzero limb of X. */
for( ; n < X->n && X->p[n] == 0; n++ )
--X->p[n];
/* If we ran out of space for the carry, it means that the result
* is negative. */
if( n == X->n )
/* Propagate the carry through the rest of X. */
carry = mbedtls_mpi_core_sub_int( X->p + n, X->p + n, carry, X->n - n );
/* If we have further carry/borrow, the result is negative. */
if( carry != 0 )
{
ret = MBEDTLS_ERR_MPI_NEGATIVE_VALUE;
goto cleanup;
}
--X->p[n];
}
/* X should always be positive as a result of unsigned subtractions. */