eden-emu/mbedtls
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Fix code review comments:

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1. variable name accoriding to the Mbed TLS coding style;
2. add a comment explaining safety of the optimization;
3. safer T2 initialization and memory zeroing on the function exit;
This commit is contained in:
Alexander K 2019-11-01 18:20:42 +03:00
parent 35d6d46169
commit d19a193738
1 changed files with 11 additions and 4 deletions
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15
library/bignum.c
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@ -1632,7 +1632,7 @@ int mbedtls_mpi_div_mpi( mbedtls_mpi *Q, mbedtls_mpi *R, const mbedtls_mpi *A,
int ret; int ret;
size_t i, n, t, k; size_t i, n, t, k;
mbedtls_mpi X, Y, Z, T1, T2; mbedtls_mpi X, Y, Z, T1, T2;
mbedtls_mpi_uint __tp2[3]; mbedtls_mpi_uint TP2[3];
MPI_VALIDATE_RET( A != NULL ); MPI_VALIDATE_RET( A != NULL );
MPI_VALIDATE_RET( B != NULL ); MPI_VALIDATE_RET( B != NULL );
@ -1641,10 +1641,16 @@ int mbedtls_mpi_div_mpi( mbedtls_mpi *Q, mbedtls_mpi *R, const mbedtls_mpi *A,
mbedtls_mpi_init( &X ); mbedtls_mpi_init( &Y ); mbedtls_mpi_init( &Z ); mbedtls_mpi_init( &X ); mbedtls_mpi_init( &Y ); mbedtls_mpi_init( &Z );
mbedtls_mpi_init( &T1 ); mbedtls_mpi_init( &T1 );
/* Avoid dynamic memory allocations for constant-size T2. */ /*
* Avoid dynamic memory allocations for constant-size T2.
*
* T2 is used for comparison only and the 3 limbs are assigned explicitly,
* so nobody increase the size of the MPI and we're safe to use an on-stack
* buffer.
*/
T2.s = 1; T2.s = 1;
T2.n = 3; T2.n = sizeof( TP2 ) / sizeof( *TP2 );
T2.p = __tp2; T2.p = TP2;
if( mbedtls_mpi_cmp_abs( A, B ) < 0 ) if( mbedtls_mpi_cmp_abs( A, B ) < 0 )
{ {
@ -1740,6 +1746,7 @@ cleanup:
mbedtls_mpi_free( &X ); mbedtls_mpi_free( &Y ); mbedtls_mpi_free( &Z ); mbedtls_mpi_free( &X ); mbedtls_mpi_free( &Y ); mbedtls_mpi_free( &Z );
mbedtls_mpi_free( &T1 ); mbedtls_mpi_free( &T1 );
mbedtls_platform_zeroize( TP2, sizeof( TP2 ) );
return( ret ); return( ret );
} }