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Make verify_restartable() actually restartable

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This commit is contained in:
Manuel Pégourié-Gonnard
2017-04-21 12:36:59 +02:00
parent a0c5bcc2bc
commit 5314f234ca
4 changed files with 56 additions and 9 deletions
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46
library/ecdsa.c
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@ -51,12 +51,17 @@
#endif
#if defined(MBEDTLS_ECP_RESTARTABLE)
/*
* Sub-contect for ecdsa_verify()
*/
struct mbedtls_ecdsa_restart_ver
{
int state; /* dummy */
mbedtls_mpi u1, u2; /* intermediate values */
enum { /* what to do next? */
ecdsa_ver_init = 0, /* getting started */
ecdsa_ver_muladd, /* muladd step */
} state;
};
/*
@ -75,15 +80,24 @@ static void ecdsa_restart_ver_free( mbedtls_ecdsa_restart_ver_ctx *ctx )
if( ctx == NULL )
return;
mbedtls_mpi_free( &ctx->u1 );
mbedtls_mpi_free( &ctx->u2 );
memset( ctx, 0, sizeof( *ctx ) );
}
#define ECDSA_RS_ECP &rs_ctx->ecp
/* Utility macro for checking and updating ops budget */
#define ECDSA_BUDGET( ops ) \
MBEDTLS_MPI_CHK( mbedtls_ecp_check_budget( grp, &rs_ctx->ecp, ops ) );
#else /* MBEDTLS_ECP_RESTARTABLE */
#define ECDSA_RS_ECP NULL
#define ECDSA_BUDGET( ops ) /* no-op; for compatibility */
#endif /* MBEDTLS_ECP_RESTARTABLE */
/*
@ -249,6 +263,7 @@ static int ecdsa_verify_restartable( mbedtls_ecp_group *grp,
int ret;
mbedtls_mpi e, s_inv, u1, u2;
mbedtls_ecp_point R;
mbedtls_mpi *pu1 = &u1, *pu2 = &u2;
#if !defined(MBEDTLS_ECP_RESTARTABLE)
(void) rs_ctx;
@ -276,6 +291,17 @@ static int ecdsa_verify_restartable( mbedtls_ecp_group *grp,
ecdsa_restart_ver_init( rs_ctx->ver );
}
if( rs_ctx != NULL && rs_ctx->ver != NULL )
{
/* redirect to our context */
pu1 = &rs_ctx->ver->u1;
pu2 = &rs_ctx->ver->u2;
/* jump to current step */
if( rs_ctx->ver->state == ecdsa_ver_muladd )
goto muladd;
}
#endif /* MBEDTLS_ECP_RESTARTABLE */
/*
@ -290,7 +316,9 @@ static int ecdsa_verify_restartable( mbedtls_ecp_group *grp,
/*
* Additional precaution: make sure Q is valid
* For ops count, group that together with step 4
*/
ECDSA_BUDGET( MBEDTLS_ECP_OPS_CHK + MBEDTLS_ECP_OPS_INV + 2 );
MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, Q ) );
/*
@ -303,17 +331,23 @@ static int ecdsa_verify_restartable( mbedtls_ecp_group *grp,
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &s_inv, s, &grp->N ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u1, &e, &s_inv ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u1, &u1, &grp->N ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pu1, &e, &s_inv ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pu1, pu1, &grp->N ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u2, r, &s_inv ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u2, &u2, &grp->N ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pu2, r, &s_inv ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pu2, pu2, &grp->N ) );
#if defined(MBEDTLS_ECP_RESTARTABLE)
if( rs_ctx != NULL && rs_ctx->ver != NULL )
rs_ctx->ver->state++;
muladd:
#endif
/*
* Step 5: R = u1 G + u2 Q
*/
MBEDTLS_MPI_CHK( mbedtls_ecp_muladd_restartable( grp,
&R, &u1, &grp->G, &u2, Q, ECDSA_RS_ECP ) );
&R, pu1, &grp->G, pu2, Q, ECDSA_RS_ECP ) );
if( mbedtls_ecp_is_zero( &R ) )
{