diff --git a/library/bignum.c b/library/bignum.c index 8ed9804f91..9dcd0f895d 100644 --- a/library/bignum.c +++ b/library/bignum.c @@ -262,6 +262,17 @@ void mbedtls_mpi_swap( mbedtls_mpi *X, mbedtls_mpi *Y ) memcpy( Y, &T, sizeof( mbedtls_mpi ) ); } +static inline mbedtls_mpi_uint mpi_sint_abs( mbedtls_mpi_sint z ) +{ + if( z >= 0 ) + return( z ); + /* Take care to handle the most negative value (-2^(biL-1)) correctly. + * A naive -z would have undefined behavior. + * Write this in a way that makes popular compilers happy (GCC, Clang, + * MSVC). */ + return( (mbedtls_mpi_uint) 0 - (mbedtls_mpi_uint) z ); +} + /* * Set value from integer */ @@ -273,7 +284,7 @@ int mbedtls_mpi_lset( mbedtls_mpi *X, mbedtls_mpi_sint z ) MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, 1 ) ); memset( X->p, 0, X->n * ciL ); - X->p[0] = ( z < 0 ) ? -(mbedtls_mpi_uint)z : z; + X->p[0] = mpi_sint_abs( z ); X->s = ( z < 0 ) ? -1 : 1; cleanup: @@ -1093,7 +1104,7 @@ int mbedtls_mpi_cmp_int( const mbedtls_mpi *X, mbedtls_mpi_sint z ) mbedtls_mpi_uint p[1]; MPI_VALIDATE_RET( X != NULL ); - *p = ( z < 0 ) ? -(mbedtls_mpi_uint)z : z; + *p = mpi_sint_abs( z ); Y.s = ( z < 0 ) ? -1 : 1; Y.n = 1; Y.p = p; @@ -1334,7 +1345,7 @@ int mbedtls_mpi_add_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_sint MPI_VALIDATE_RET( X != NULL ); MPI_VALIDATE_RET( A != NULL ); - p[0] = ( b < 0 ) ? -(mbedtls_mpi_uint)b : b; + p[0] = mpi_sint_abs( b ); B.s = ( b < 0 ) ? -1 : 1; B.n = 1; B.p = p; @@ -1352,7 +1363,7 @@ int mbedtls_mpi_sub_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_sint MPI_VALIDATE_RET( X != NULL ); MPI_VALIDATE_RET( A != NULL ); - p[0] = ( b < 0 ) ? -(mbedtls_mpi_uint)b : b; + p[0] = mpi_sint_abs( b ); B.s = ( b < 0 ) ? -1 : 1; B.n = 1; B.p = p; @@ -1773,7 +1784,7 @@ int mbedtls_mpi_div_int( mbedtls_mpi *Q, mbedtls_mpi *R, mbedtls_mpi_uint p[1]; MPI_VALIDATE_RET( A != NULL ); - p[0] = ( b < 0 ) ? -(mbedtls_mpi_uint)b : b; + p[0] = mpi_sint_abs( b ); B.s = ( b < 0 ) ? -1 : 1; B.n = 1; B.p = p;