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Merge pull request #3512 from gilles-peskine-arm/ecp-alloc-202007

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Reduce the number of allocations in ECP operations
This commit is contained in:
Gilles Peskine 2021-04-02 00:08:35 +02:00 committed by GitHub
parent 2af9641a7d b76517b764
commit d5200371ec
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 156 additions and 87 deletions
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131
library/bignum.c
View file

@ -1339,29 +1339,32 @@ cleanup:
/**
* Helper for mbedtls_mpi subtraction.
*
* Calculate d - s where d and s have the same size.
* Calculate l - r where l and r have the same size.
* This function operates modulo (2^ciL)^n and returns the carry
* (1 if there was a wraparound, i.e. if `d < s`, and 0 otherwise).
* (1 if there was a wraparound, i.e. if `l < r`, and 0 otherwise).
*
* \param n Number of limbs of \p d and \p s.
* \param[in,out] d On input, the left operand.
* On output, the result of the subtraction:
* \param[in] s The right operand.
* d may be aliased to l or r.
*
* \return 1 if `d < s`.
* 0 if `d >= s`.
* \param n Number of limbs of \p d, \p l and \p r.
* \param[out] d The result of the subtraction.
* \param[in] l The left operand.
* \param[in] r The right operand.
*
* \return 1 if `l < r`.
* 0 if `l >= r`.
*/
static mbedtls_mpi_uint mpi_sub_hlp( size_t n,
mbedtls_mpi_uint *d,
const mbedtls_mpi_uint *s )
const mbedtls_mpi_uint *l,
const mbedtls_mpi_uint *r )
{
size_t i;
mbedtls_mpi_uint c, z;
mbedtls_mpi_uint c = 0, t, z;
for( i = c = 0; i < n; i++, s++, d++ )
for( i = 0; i < n; i++ )
{
z = ( *d < c ); *d -= c;
c = ( *d < *s ) + z; *d -= *s;
z = ( l[i] < c ); t = l[i] - c;
c = ( t < r[i] ) + z; d[i] = t - r[i];
}
return( c );
@ -1372,7 +1375,6 @@ static mbedtls_mpi_uint mpi_sub_hlp( size_t n,
*/
int mbedtls_mpi_sub_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi *B )
{
mbedtls_mpi TB;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t n;
mbedtls_mpi_uint carry;
@ -1380,24 +1382,6 @@ int mbedtls_mpi_sub_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
MPI_VALIDATE_RET( A != NULL );
MPI_VALIDATE_RET( B != NULL );
mbedtls_mpi_init( &TB );
if( X == B )
{
MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &TB, B ) );
B = &TB;
}
if( X != A )
MBEDTLS_MPI_CHK( mbedtls_mpi_copy( X, A ) );
/*
* X should always be positive as a result of unsigned subtractions.
*/
X->s = 1;
ret = 0;
for( n = B->n; n > 0; n-- )
if( B->p[n - 1] != 0 )
break;
@ -1408,7 +1392,17 @@ int mbedtls_mpi_sub_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
goto cleanup;
}
carry = mpi_sub_hlp( n, X->p, B->p );
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, A->n ) );
/* Set the high limbs of X to match A. Don't touch the lower limbs
* because X might be aliased to B, and we must not overwrite the
* significant digits of B. */
if( A->n > n )
memcpy( X->p + n, A->p + n, ( A->n - n ) * ciL );
if( X->n > A->n )
memset( X->p + A->n, 0, ( X->n - A->n ) * ciL );
carry = mpi_sub_hlp( n, X->p, A->p, B->p );
if( carry != 0 )
{
/* Propagate the carry to the first nonzero limb of X. */
@ -1424,10 +1418,10 @@ int mbedtls_mpi_sub_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
--X->p[n];
}
/* X should always be positive as a result of unsigned subtractions. */
X->s = 1;
cleanup:
mbedtls_mpi_free( &TB );
return( ret );
}
@ -1537,8 +1531,21 @@ int mbedtls_mpi_sub_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_sint
return( mbedtls_mpi_sub_mpi( X, A, &_B ) );
}
/*
* Helper for mbedtls_mpi multiplication
/** Helper for mbedtls_mpi multiplication.
*
* Add \p b * \p s to \p d.
*
* \param i The number of limbs of \p s.
* \param[in] s A bignum to multiply, of size \p i.
* It may overlap with \p d, but only if
* \p d <= \p s.
* Its leading limb must not be \c 0.
* \param[in,out] d The bignum to add to.
* It must be sufficiently large to store the
* result of the multiplication. This means
* \p i + 1 limbs if \p d[\p i - 1] started as 0 and \p b
* is not known a priori.
* \param b A scalar to multiply.
*/
static
#if defined(__APPLE__) && defined(__arm__)
@ -1548,7 +1555,10 @@ static
*/
__attribute__ ((noinline))
#endif
void mpi_mul_hlp( size_t i, mbedtls_mpi_uint *s, mbedtls_mpi_uint *d, mbedtls_mpi_uint b )
void mpi_mul_hlp( size_t i,
const mbedtls_mpi_uint *s,
mbedtls_mpi_uint *d,
mbedtls_mpi_uint b )
{
mbedtls_mpi_uint c = 0, t = 0;
@ -1603,10 +1613,10 @@ void mpi_mul_hlp( size_t i, mbedtls_mpi_uint *s, mbedtls_mpi_uint *d, mbedtls_mp
t++;
do {
while( c != 0 )
{
*d += c; c = ( *d < c ); d++;
}
while( c != 0 );
}
/*
@ -1654,17 +1664,38 @@ cleanup:
*/
int mbedtls_mpi_mul_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_uint b )
{
mbedtls_mpi _B;
mbedtls_mpi_uint p[1];
MPI_VALIDATE_RET( X != NULL );
MPI_VALIDATE_RET( A != NULL );
_B.s = 1;
_B.n = 1;
_B.p = p;
p[0] = b;
/* mpi_mul_hlp can't deal with a leading 0. */
size_t n = A->n;
while( n > 0 && A->p[n - 1] == 0 )
--n;
return( mbedtls_mpi_mul_mpi( X, A, &_B ) );
/* The general method below doesn't work if n==0 or b==0. By chance
* calculating the result is trivial in those cases. */
if( b == 0 || n == 0 )
{
mbedtls_mpi_lset( X, 0 );
return( 0 );
}
/* Calculate A*b as A + A*(b-1) to take advantage of mpi_mul_hlp */
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
/* In general, A * b requires 1 limb more than b. If
* A->p[n - 1] * b / b == A->p[n - 1], then A * b fits in the same
* number of limbs as A and the call to grow() is not required since
* copy() will take care of the growth if needed. However, experimentally,
* making the call to grow() unconditional causes slightly fewer
* calls to calloc() in ECP code, presumably because it reuses the
* same mpi for a while and this way the mpi is more likely to directly
* grow to its final size. */
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, n + 1 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_copy( X, A ) );
mpi_mul_hlp( n, A->p, X->p, b - 1 );
cleanup:
return( ret );
}
/*
@ -1805,7 +1836,7 @@ int mbedtls_mpi_div_mpi( mbedtls_mpi *Q, mbedtls_mpi *R, const mbedtls_mpi *A,
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( &Z, A->n + 2 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &Z, 0 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( &T1, 2 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( &T1, A->n + 2 ) );
k = mbedtls_mpi_bitlen( &Y ) % biL;
if( k < biL - 1 )
@ -2071,7 +2102,7 @@ static void mpi_montmul( mbedtls_mpi *A, const mbedtls_mpi *B, const mbedtls_mpi
* do the calculation without using conditional tests. */
/* Set d to d0 + (2^biL)^n - N where d0 is the current value of d. */
d[n] += 1;
d[n] -= mpi_sub_hlp( n, d, N->p );
d[n] -= mpi_sub_hlp( n, d, d, N->p );
/* If d0 < N then d < (2^biL)^n
* so d[n] == 0 and we want to keep A as it is.
* If d0 >= N then d >= (2^biL)^n, and d <= (2^biL)^n + N < 2 * (2^biL)^n

54
library/ecp_curves.c
View file

@ -1000,25 +1000,20 @@ static inline void sub32( uint32_t *dst, uint32_t src, signed char *carry )
#define ADD( j ) add32( &cur, A( j ), &c );
#define SUB( j ) sub32( &cur, A( j ), &c );
#define ciL (sizeof(mbedtls_mpi_uint)) /* chars in limb */
#define biL (ciL << 3) /* bits in limb */
/*
* Helpers for the main 'loop'
* (see fix_negative for the motivation of C)
*/
#define INIT( b ) \
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; \
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; \
signed char c = 0, cc; \
uint32_t cur; \
size_t i = 0, bits = (b); \
mbedtls_mpi C; \
mbedtls_mpi_uint Cp[ (b) / 8 / sizeof( mbedtls_mpi_uint) + 1 ]; \
\
C.s = 1; \
C.n = (b) / 8 / sizeof( mbedtls_mpi_uint) + 1; \
C.p = Cp; \
memset( Cp, 0, C.n * sizeof( mbedtls_mpi_uint ) ); \
\
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( N, (b) * 2 / 8 / \
sizeof( mbedtls_mpi_uint ) ) ); \
/* N is the size of the product of two b-bit numbers, plus one */ \
/* limb for fix_negative */ \
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( N, ( b ) * 2 / biL + 1 ) ); \
LOAD32;
#define NEXT \
@ -1033,33 +1028,32 @@ static inline void sub32( uint32_t *dst, uint32_t src, signed char *carry )
STORE32; i++; \
cur = c > 0 ? c : 0; STORE32; \
cur = 0; while( ++i < MAX32 ) { STORE32; } \
if( c < 0 ) MBEDTLS_MPI_CHK( fix_negative( N, c, &C, bits ) );
if( c < 0 ) fix_negative( N, c, bits );
/*
* If the result is negative, we get it in the form
* c * 2^(bits + 32) + N, with c negative and N positive shorter than 'bits'
*/
static inline int fix_negative( mbedtls_mpi *N, signed char c, mbedtls_mpi *C, size_t bits )
static inline void fix_negative( mbedtls_mpi *N, signed char c, size_t bits )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t i;
/* C = - c * 2^(bits + 32) */
#if !defined(MBEDTLS_HAVE_INT64)
((void) bits);
#else
if( bits == 224 )
C->p[ C->n - 1 ] = ((mbedtls_mpi_uint) -c) << 32;
else
#endif
C->p[ C->n - 1 ] = (mbedtls_mpi_uint) -c;
/* N = - ( C - N ) */
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_abs( N, C, N ) );
/* Set N := N - 2^bits */
--N->p[0];
for( i = 0; i <= bits / 8 / sizeof( mbedtls_mpi_uint ); i++ )
{
N->p[i] = ~(mbedtls_mpi_uint)0 - N->p[i];
}
N->s = -1;
cleanup:
return( ret );
/* Add |c| * 2^(bits + 32) to the absolute value. Since c and N are
* negative, this adds c * 2^(bits + 32). */
mbedtls_mpi_uint msw = (mbedtls_mpi_uint) -c;
#if defined(MBEDTLS_HAVE_INT64)
if( bits == 224 )
msw <<= 32;
#endif
N->p[bits / 8 / sizeof( mbedtls_mpi_uint)] += msw;
}
#if defined(MBEDTLS_ECP_DP_SECP224R1_ENABLED)

58
programs/test/benchmark.c
View file

@ -266,6 +266,21 @@ void ecp_clear_precomputed( mbedtls_ecp_group *grp )
#define ecp_clear_precomputed( g )
#endif
#if defined(MBEDTLS_ECP_C)
static int set_ecp_curve( const char *string, mbedtls_ecp_curve_info *curve )
{
const mbedtls_ecp_curve_info *found =
mbedtls_ecp_curve_info_from_name( string );
if( found != NULL )
{
*curve = *found;
return( 1 );
}
else
return( 0 );
}
#endif
unsigned char buf[BUFSIZE];
typedef struct {
@ -289,6 +304,17 @@ int main( int argc, char *argv[] )
#if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
unsigned char alloc_buf[HEAP_SIZE] = { 0 };
#endif
#if defined(MBEDTLS_ECP_C)
mbedtls_ecp_curve_info single_curve[2] = {
{ MBEDTLS_ECP_DP_NONE, 0, 0, NULL },
{ MBEDTLS_ECP_DP_NONE, 0, 0, NULL },
};
const mbedtls_ecp_curve_info *curve_list = mbedtls_ecp_curve_list( );
#endif
#if defined(MBEDTLS_ECP_C)
(void) curve_list; /* Unused in some configurations where no benchmark uses ECC */
#endif
if( argc <= 1 )
{
@ -356,6 +382,10 @@ int main( int argc, char *argv[] )
todo.ecdsa = 1;
else if( strcmp( argv[i], "ecdh" ) == 0 )
todo.ecdh = 1;
#if defined(MBEDTLS_ECP_C)
else if( set_ecp_curve( argv[i], single_curve ) )
curve_list = single_curve;
#endif
else
{
mbedtls_printf( "Unrecognized option: %s\n", argv[i] );
@ -845,7 +875,7 @@ int main( int argc, char *argv[] )
memset( buf, 0x2A, sizeof( buf ) );
for( curve_info = mbedtls_ecp_curve_list();
for( curve_info = curve_list;
curve_info->grp_id != MBEDTLS_ECP_DP_NONE;
curve_info++ )
{
@ -867,7 +897,7 @@ int main( int argc, char *argv[] )
mbedtls_ecdsa_free( &ecdsa );
}
for( curve_info = mbedtls_ecp_curve_list();
for( curve_info = curve_list;
curve_info->grp_id != MBEDTLS_ECP_DP_NONE;
curve_info++ )
{
@ -911,8 +941,23 @@ int main( int argc, char *argv[] )
};
const mbedtls_ecp_curve_info *curve_info;
size_t olen;
const mbedtls_ecp_curve_info *selected_montgomery_curve_list =
montgomery_curve_list;
for( curve_info = mbedtls_ecp_curve_list();
if( curve_list == (const mbedtls_ecp_curve_info*) &single_curve )
{
mbedtls_ecp_group grp;
mbedtls_ecp_group_init( &grp );
if( mbedtls_ecp_group_load( &grp, curve_list->grp_id ) != 0 )
mbedtls_exit( 1 );
if( mbedtls_ecp_get_type( &grp ) == MBEDTLS_ECP_TYPE_MONTGOMERY )
selected_montgomery_curve_list = single_curve;
else /* empty list */
selected_montgomery_curve_list = single_curve + 1;
mbedtls_ecp_group_free( &grp );
}
for( curve_info = curve_list;
curve_info->grp_id != MBEDTLS_ECP_DP_NONE;
curve_info++ )
{
@ -938,7 +983,7 @@ int main( int argc, char *argv[] )
}
/* Montgomery curves need to be handled separately */
for ( curve_info = montgomery_curve_list;
for ( curve_info = selected_montgomery_curve_list;
curve_info->grp_id != MBEDTLS_ECP_DP_NONE;
curve_info++ )
{
@ -960,7 +1005,7 @@ int main( int argc, char *argv[] )
mbedtls_mpi_free( &z );
}
for( curve_info = mbedtls_ecp_curve_list();
for( curve_info = curve_list;
curve_info->grp_id != MBEDTLS_ECP_DP_NONE;
curve_info++ )
{
@ -986,7 +1031,7 @@ int main( int argc, char *argv[] )
}
/* Montgomery curves need to be handled separately */
for ( curve_info = montgomery_curve_list;
for ( curve_info = selected_montgomery_curve_list;
curve_info->grp_id != MBEDTLS_ECP_DP_NONE;
curve_info++)
{
@ -1015,7 +1060,6 @@ int main( int argc, char *argv[] )
{
mbedtls_ecdh_context ecdh_srv, ecdh_cli;
unsigned char buf_srv[BUFSIZE], buf_cli[BUFSIZE];
const mbedtls_ecp_curve_info * curve_list = mbedtls_ecp_curve_list();
const mbedtls_ecp_curve_info *curve_info;
size_t olen;