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Allow T to be computed in multiple steps

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Previously there were only two states:
- T unallocated
- T allocated and valid

Now there are three:
- T unallocated
- T allocated and in progress
- T allocated and valid

Introduce new bool T_ok to distinguish the last two states.
This commit is contained in:
Manuel Pégourié-Gonnard 2017-03-16 16:56:04 +01:00
parent c9c0aa6306
commit 085b1dff40
1 changed files with 32 additions and 6 deletions
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38
library/ecp.c
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@ -113,6 +113,8 @@ struct mbedtls_ecp_restart {
unsigned char T_size; /* number of points in table T */ unsigned char T_size; /* number of points in table T */
enum { /* what's the next step ? */ enum { /* what's the next step ? */
ecp_rs_init = 0, /* just getting started */ ecp_rs_init = 0, /* just getting started */
ecp_rs_tmp_dummy, /* temporary for incremental testing */
ecp_rs_T_done, /* call ecp_mul_comb_after_precomp() */
ecp_rs_final_norm, /* do the final normalization */ ecp_rs_final_norm, /* do the final normalization */
} state; } state;
}; };
@ -1334,6 +1336,15 @@ static int ecp_precompute_comb( const mbedtls_ecp_group *grp,
size_t j; size_t j;
mbedtls_ecp_point *cur, *TT[COMB_MAX_PRE - 1]; mbedtls_ecp_point *cur, *TT[COMB_MAX_PRE - 1];
#if defined(MBEDTLS_ECP_EARLY_RETURN)
/* XXX: dummy "in_progress" return for testing caller */
if( grp->rs != NULL && grp->rs->state == ecp_rs_init )
{
grp->rs->state++;
return( MBEDTLS_ERR_ECP_IN_PROGRESS );
}
#endif
/* /*
* Set T[0] = P and * Set T[0] = P and
* T[2^{l-1}] = 2^{dl} P for l = 1 .. w-1 (this is not the final value) * T[2^{l-1}] = 2^{dl} P for l = 1 .. w-1 (this is not the final value)
@ -1370,6 +1381,11 @@ static int ecp_precompute_comb( const mbedtls_ecp_group *grp,
MBEDTLS_MPI_CHK( ecp_normalize_jac_many( grp, TT, k ) ); MBEDTLS_MPI_CHK( ecp_normalize_jac_many( grp, TT, k ) );
#if defined(MBEDTLS_ECP_EARLY_RETURN)
if( grp->rs != NULL )
grp->rs->state++;
#endif
cleanup: cleanup:
return( ret ); return( ret );
@ -1613,7 +1629,7 @@ static int ecp_mul_comb( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
int ret; int ret;
unsigned char w, p_eq_g = 0, i; unsigned char w, p_eq_g = 0, i;
size_t d; size_t d;
unsigned char pre_len = 0; unsigned char pre_len = 0, T_ok = 0;
mbedtls_ecp_point *T = NULL; mbedtls_ecp_point *T = NULL;
#if defined(MBEDTLS_ECP_EARLY_RETURN) #if defined(MBEDTLS_ECP_EARLY_RETURN)
@ -1657,22 +1673,28 @@ static int ecp_mul_comb( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
pre_len = 1U << ( w - 1 ); pre_len = 1U << ( w - 1 );
d = ( grp->nbits + w - 1 ) / w; d = ( grp->nbits + w - 1 ) / w;
/* /* Pre-computed table: do we have it already for the base point? */
* Prepare precomputed points: if P == G we want to if( p_eq_g && grp->T != NULL )
* use grp->T if already initialized, or initialize it. {
*/ T = grp->T;
T = p_eq_g ? grp->T : NULL; T_ok = 1;
}
#if defined(MBEDTLS_ECP_EARLY_RETURN) #if defined(MBEDTLS_ECP_EARLY_RETURN)
/* Pre-computed table: do we have one in progress? complete? */
if( grp->rs != NULL && grp->rs->T != NULL && T == NULL ) if( grp->rs != NULL && grp->rs->T != NULL && T == NULL )
{ {
/* transfer "ownership" of T from rs to local function */ /* transfer "ownership" of T from rs to local function */
T = grp->rs->T; T = grp->rs->T;
grp->rs->T = NULL; grp->rs->T = NULL;
grp->rs->T_size = 0; grp->rs->T_size = 0;
if( grp->rs->state >= ecp_rs_T_done )
T_ok = 1;
} }
#endif #endif
/* Allocate table if we didn't have any */
if( T == NULL ) if( T == NULL )
{ {
T = mbedtls_calloc( pre_len, sizeof( mbedtls_ecp_point ) ); T = mbedtls_calloc( pre_len, sizeof( mbedtls_ecp_point ) );
@ -1681,7 +1703,11 @@ static int ecp_mul_comb( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
ret = MBEDTLS_ERR_ECP_ALLOC_FAILED; ret = MBEDTLS_ERR_ECP_ALLOC_FAILED;
goto cleanup; goto cleanup;
} }
}
/* Compute table (or finish computing it) if not done already */
if( !T_ok )
{
MBEDTLS_MPI_CHK( ecp_precompute_comb( grp, T, P, w, d ) ); MBEDTLS_MPI_CHK( ecp_precompute_comb( grp, T, P, w, d ) );
if( p_eq_g ) if( p_eq_g )