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Reuse Bignum helper functions

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Signed-off-by: Janos Follath <janos.follath@arm.com>
This commit is contained in:
Janos Follath 2022-07-21 18:25:42 +01:00
parent 4614b9ad1b
commit 4670f88991
3 changed files with 18 additions and 131 deletions
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128
library/bignum.c
View file

@ -337,41 +337,12 @@ size_t mbedtls_mpi_lsb( const mbedtls_mpi *X )
return( 0 );
}
/*
* Count leading zero bits in a given integer
*/
static size_t mbedtls_clz( const mbedtls_mpi_uint x )
{
size_t j;
mbedtls_mpi_uint mask = (mbedtls_mpi_uint) 1 << (biL - 1);
for( j = 0; j < biL; j++ )
{
if( x & mask ) break;
mask >>= 1;
}
return j;
}
/*
* Return the number of bits
*/
size_t mbedtls_mpi_bitlen( const mbedtls_mpi *X )
{
size_t i, j;
if( X->n == 0 )
return( 0 );
for( i = X->n - 1; i > 0; i-- )
if( X->p[i] != 0 )
break;
j = biL - mbedtls_clz( X->p[i] );
return( ( i * biL ) + j );
return mbedtls_mpi_core_bitlen( X->p, X->n );
}
/*
@ -678,97 +649,6 @@ cleanup:
}
#endif /* MBEDTLS_FS_IO */
/* Convert a big-endian byte array aligned to the size of mbedtls_mpi_uint
* into the storage form used by mbedtls_mpi. */
static mbedtls_mpi_uint mpi_uint_bigendian_to_host_c( mbedtls_mpi_uint x )
{
uint8_t i;
unsigned char *x_ptr;
mbedtls_mpi_uint tmp = 0;
for( i = 0, x_ptr = (unsigned char*) &x; i < ciL; i++, x_ptr++ )
{
tmp <<= CHAR_BIT;
tmp |= (mbedtls_mpi_uint) *x_ptr;
}
return( tmp );
}
static mbedtls_mpi_uint mpi_uint_bigendian_to_host( mbedtls_mpi_uint x )
{
#if defined(__BYTE_ORDER__)
/* Nothing to do on bigendian systems. */
#if ( __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ )
return( x );
#endif /* __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ */
#if ( __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ )
/* For GCC and Clang, have builtins for byte swapping. */
#if defined(__GNUC__) && defined(__GNUC_PREREQ)
#if __GNUC_PREREQ(4,3)
#define have_bswap
#endif
#endif
#if defined(__clang__) && defined(__has_builtin)
#if __has_builtin(__builtin_bswap32) && \
__has_builtin(__builtin_bswap64)
#define have_bswap
#endif
#endif
#if defined(have_bswap)
/* The compiler is hopefully able to statically evaluate this! */
switch( sizeof(mbedtls_mpi_uint) )
{
case 4:
return( __builtin_bswap32(x) );
case 8:
return( __builtin_bswap64(x) );
}
#endif
#endif /* __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ */
#endif /* __BYTE_ORDER__ */
/* Fall back to C-based reordering if we don't know the byte order
* or we couldn't use a compiler-specific builtin. */
return( mpi_uint_bigendian_to_host_c( x ) );
}
static void mpi_bigendian_to_host( mbedtls_mpi_uint * const p, size_t limbs )
{
mbedtls_mpi_uint *cur_limb_left;
mbedtls_mpi_uint *cur_limb_right;
if( limbs == 0 )
return;
/*
* Traverse limbs and
* - adapt byte-order in each limb
* - swap the limbs themselves.
* For that, simultaneously traverse the limbs from left to right
* and from right to left, as long as the left index is not bigger
* than the right index (it's not a problem if limbs is odd and the
* indices coincide in the last iteration).
*/
for( cur_limb_left = p, cur_limb_right = p + ( limbs - 1 );
cur_limb_left <= cur_limb_right;
cur_limb_left++, cur_limb_right-- )
{
mbedtls_mpi_uint tmp;
/* Note that if cur_limb_left == cur_limb_right,
* this code effectively swaps the bytes only once. */
tmp = mpi_uint_bigendian_to_host( *cur_limb_left );
*cur_limb_left = mpi_uint_bigendian_to_host( *cur_limb_right );
*cur_limb_right = tmp;
}
}
/*
* Import X from unsigned binary data, little endian
*
@ -824,7 +704,7 @@ int mbedtls_mpi_read_binary( mbedtls_mpi *X, const unsigned char *buf, size_t bu
Xp = (unsigned char*) X->p;
memcpy( Xp + overhead, buf, buflen );
mpi_bigendian_to_host( X->p, limbs );
mbedtls_mpi_core_bigendian_to_host( X->p, limbs );
}
cleanup:
@ -1530,7 +1410,7 @@ static mbedtls_mpi_uint mbedtls_int_div_int( mbedtls_mpi_uint u1,
/*
* Normalize the divisor, d, and dividend, u0, u1
*/
s = mbedtls_clz( d );
s = mbedtls_mpi_core_clz( d );
d = d << s;
u1 = u1 << s;
@ -2319,7 +2199,7 @@ static int mpi_fill_random_internal(
memset( X->p, 0, overhead );
memset( (unsigned char *) X->p + limbs * ciL, 0, ( X->n - limbs ) * ciL );
MBEDTLS_MPI_CHK( f_rng( p_rng, (unsigned char *) X->p + overhead, n_bytes ) );
mpi_bigendian_to_host( X->p, limbs );
mbedtls_mpi_core_bigendian_to_host( X->p, limbs );
cleanup:
return( ret );

7
library/bignum_core.h
View file

@ -42,6 +42,13 @@
#define BITS_TO_LIMBS(i) ( (i) / biL + ( (i) % biL != 0 ) )
#define CHARS_TO_LIMBS(i) ( (i) / ciL + ( (i) % ciL != 0 ) )
size_t mbedtls_mpi_core_clz( const mbedtls_mpi_uint x );
size_t mbedtls_mpi_core_bitlen( const mbedtls_mpi_uint *X, size_t nx );
void mbedtls_mpi_core_bigendian_to_host( mbedtls_mpi_uint * const X,
size_t limbs );
int mbedtls_mpi_core_read_le( mbedtls_mpi_uint *X,
size_t nx,
const unsigned char *buf,

14
library/bignum_new.c
View file

@ -43,7 +43,7 @@
/*
* Count leading zero bits in a given integer
*/
static size_t mpi_clz( const mbedtls_mpi_uint x )
size_t mbedtls_mpi_core_clz( const mbedtls_mpi_uint x )
{
size_t j;
mbedtls_mpi_uint mask = (mbedtls_mpi_uint) 1 << (biL - 1);
@ -61,7 +61,7 @@ static size_t mpi_clz( const mbedtls_mpi_uint x )
/*
* Return the number of bits
*/
static size_t mpi_bitlen( const mbedtls_mpi_uint *X, size_t nx )
size_t mbedtls_mpi_core_bitlen( const mbedtls_mpi_uint *X, size_t nx )
{
size_t i, j;
@ -72,7 +72,7 @@ static size_t mpi_bitlen( const mbedtls_mpi_uint *X, size_t nx )
if( X[i] != 0 )
break;
j = biL - mpi_clz( X[i] );
j = biL - mbedtls_mpi_core_clz( X[i] );
return( ( i * biL ) + j );
}
@ -150,7 +150,7 @@ int mbedtls_mpi_mod_modulus_setup( mbedtls_mpi_mod_modulus *m,
m->p = X;
m->n = nx;
m->plen = mpi_bitlen( X, nx );
m->plen = mbedtls_mpi_core_bitlen( X, nx );
switch( ext_rep )
{
@ -264,8 +264,8 @@ static mbedtls_mpi_uint mpi_bigendian_to_host( mbedtls_mpi_uint x )
return( mpi_bigendian_to_host_c( x ) );
}
static void mpi_core_bigendian_to_host( mbedtls_mpi_uint * const X,
size_t limbs )
void mbedtls_mpi_core_bigendian_to_host( mbedtls_mpi_uint * const X,
size_t limbs )
{
mbedtls_mpi_uint *cur_limb_left;
mbedtls_mpi_uint *cur_limb_right;
@ -350,7 +350,7 @@ int mbedtls_mpi_core_read_be( mbedtls_mpi_uint *X,
Xp = (unsigned char*) X;
memcpy( Xp + overhead, buf, buflen );
mpi_core_bigendian_to_host( X, nx );
mbedtls_mpi_core_bigendian_to_host( X, nx );
}
cleanup: