AuroraMiddleware/mbedtls
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

More logical parameter order for mpi_sub_hlp

Browse Source 
mpi_sub_hlp performs a subtraction A - B, but took parameters in the
order (B, A). Swap the parameters so that they match the usual
mathematical syntax.

This has the additional benefit of putting the output parameter (A)
first, which is the normal convention in this module.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2020-06-08 22:05:13 +02:00
parent 026f555df3
commit 37ecc61836
1 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
library/bignum.c
View File

@ -1347,8 +1347,8 @@ cleanup:
* d -= s where d and s have the same size and d >= s.
*/
static void mpi_sub_hlp( size_t n,
const mbedtls_mpi_uint *s,
mbedtls_mpi_uint *d )
mbedtls_mpi_uint *d,
const mbedtls_mpi_uint *s )
{
size_t i;
mbedtls_mpi_uint c, z;
@ -1403,7 +1403,7 @@ int mbedtls_mpi_sub_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
if( B->p[n - 1] != 0 )
break;
mpi_sub_hlp( n, B->p, X->p );
mpi_sub_hlp( n, X->p, B->p );
cleanup:
@ -2047,7 +2047,7 @@ static void mpi_montmul( mbedtls_mpi *A, const mbedtls_mpi *B, const mbedtls_mpi
* timing attacks. */
/* Set d to A + (2^biL)^n - N. */
d[n] += 1;
mpi_sub_hlp( n, N->p, d );
mpi_sub_hlp( n, d, N->p );
/* Now d - (2^biL)^n = A - N so d >= (2^biL)^n iff A >= N.
* So we want to copy the result of the subtraction iff d->p[n] != 0.
* Note that d->p[n] is either 0 or 1 since A - N <= N <= (2^biL)^n. */