diff options
Diffstat (limited to 'library/ecp.c')
-rw-r--r-- | library/ecp.c | 229 |
1 files changed, 226 insertions, 3 deletions
diff --git a/library/ecp.c b/library/ecp.c index 9522edf77..7b205160a 100644 --- a/library/ecp.c +++ b/library/ecp.c @@ -105,6 +105,16 @@ #include "mbedtls/ecp_internal.h" +#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG) +#if defined(MBEDTLS_HMAC_DRBG_C) +#include "mbedtls/hmac_drbg.h" +#elif defined(MBEDTLS_CTR_DRBG_C) +#include "mbedtls/ctr_drbg.h" +#else +#error "Invalid configuration detected. Include check_config.h to ensure that the configuration is valid." +#endif +#endif /* MBEDTLS_ECP_NO_INTERNAL_RNG */ + #if ( defined(__ARMCC_VERSION) || defined(_MSC_VER) ) && \ !defined(inline) && !defined(__cplusplus) #define inline __inline @@ -118,6 +128,144 @@ static unsigned long add_count, dbl_count, mul_count; #endif +#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG) +/* + * Currently ecp_mul() takes a RNG function as an argument, used for + * side-channel protection, but it can be NULL. The initial reasoning was + * that people will pass non-NULL RNG when they care about side-channels, but + * unfortunately we have some APIs that call ecp_mul() with a NULL RNG, with + * no opportunity for the user to do anything about it. + * + * The obvious strategies for addressing that include: + * - change those APIs so that they take RNG arguments; + * - require a global RNG to be available to all crypto modules. + * + * Unfortunately those would break compatibility. So what we do instead is + * have our own internal DRBG instance, seeded from the secret scalar. + * + * The following is a light-weight abstraction layer for doing that with + * HMAC_DRBG (first choice) or CTR_DRBG. + */ + +#if defined(MBEDTLS_HMAC_DRBG_C) + +/* DRBG context type */ +typedef mbedtls_hmac_drbg_context ecp_drbg_context; + +/* DRBG context init */ +static inline void ecp_drbg_init( ecp_drbg_context *ctx ) +{ + mbedtls_hmac_drbg_init( ctx ); +} + +/* DRBG context free */ +static inline void ecp_drbg_free( ecp_drbg_context *ctx ) +{ + mbedtls_hmac_drbg_free( ctx ); +} + +/* DRBG function */ +static inline int ecp_drbg_random( void *p_rng, + unsigned char *output, size_t output_len ) +{ + return( mbedtls_hmac_drbg_random( p_rng, output, output_len ) ); +} + +/* DRBG context seeding */ +static int ecp_drbg_seed( ecp_drbg_context *ctx, + const mbedtls_mpi *secret, size_t secret_len ) +{ + int ret; + unsigned char secret_bytes[MBEDTLS_ECP_MAX_BYTES]; + /* The list starts with strong hashes */ + const mbedtls_md_type_t md_type = mbedtls_md_list()[0]; + const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type( md_type ); + + if( secret_len > MBEDTLS_ECP_MAX_BYTES ) + { + ret = MBEDTLS_ERR_ECP_RANDOM_FAILED; + goto cleanup; + } + + MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( secret, + secret_bytes, secret_len ) ); + + ret = mbedtls_hmac_drbg_seed_buf( ctx, md_info, secret_bytes, secret_len ); + +cleanup: + mbedtls_platform_zeroize( secret_bytes, secret_len ); + + return( ret ); +} + +#elif defined(MBEDTLS_CTR_DRBG_C) + +/* DRBG context type */ +typedef mbedtls_ctr_drbg_context ecp_drbg_context; + +/* DRBG context init */ +static inline void ecp_drbg_init( ecp_drbg_context *ctx ) +{ + mbedtls_ctr_drbg_init( ctx ); +} + +/* DRBG context free */ +static inline void ecp_drbg_free( ecp_drbg_context *ctx ) +{ + mbedtls_ctr_drbg_free( ctx ); +} + +/* DRBG function */ +static inline int ecp_drbg_random( void *p_rng, + unsigned char *output, size_t output_len ) +{ + return( mbedtls_ctr_drbg_random( p_rng, output, output_len ) ); +} + +/* + * Since CTR_DRBG doesn't have a seed_buf() function the way HMAC_DRBG does, + * we need to pass an entropy function when seeding. So we use a dummy + * function for that, and pass the actual entropy as customisation string. + * (During seeding of CTR_DRBG the entropy input and customisation string are + * concatenated before being used to update the secret state.) + */ +static int ecp_ctr_drbg_null_entropy(void *ctx, unsigned char *out, size_t len) +{ + (void) ctx; + memset( out, 0, len ); + return( 0 ); +} + +/* DRBG context seeding */ +static int ecp_drbg_seed( ecp_drbg_context *ctx, + const mbedtls_mpi *secret, size_t secret_len ) +{ + int ret; + unsigned char secret_bytes[MBEDTLS_ECP_MAX_BYTES]; + + if( secret_len > MBEDTLS_ECP_MAX_BYTES ) + { + ret = MBEDTLS_ERR_ECP_RANDOM_FAILED; + goto cleanup; + } + + MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( secret, + secret_bytes, secret_len ) ); + + ret = mbedtls_ctr_drbg_seed( ctx, ecp_ctr_drbg_null_entropy, NULL, + secret_bytes, secret_len ); + +cleanup: + mbedtls_platform_zeroize( secret_bytes, secret_len ); + + return( ret ); +} + +#else +#error "Invalid configuration detected. Include check_config.h to ensure that the configuration is valid." +#endif /* DRBG modules */ +#endif /* MBEDTLS_ECP_NO_INTERNAL_RNG */ + #if defined(MBEDTLS_ECP_RESTARTABLE) /* * Maximum number of "basic operations" to be done in a row. @@ -165,6 +313,10 @@ struct mbedtls_ecp_restart_mul ecp_rsm_comb_core, /* ecp_mul_comb_core() */ ecp_rsm_final_norm, /* do the final normalization */ } state; +#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG) + ecp_drbg_context drbg_ctx; + unsigned char drbg_seeded; +#endif }; /* @@ -177,6 +329,10 @@ static void ecp_restart_rsm_init( mbedtls_ecp_restart_mul_ctx *ctx ) ctx->T = NULL; ctx->T_size = 0; ctx->state = ecp_rsm_init; +#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG) + ecp_drbg_init( &ctx->drbg_ctx ); + ctx->drbg_seeded = 0; +#endif } /* @@ -198,6 +354,10 @@ static void ecp_restart_rsm_free( mbedtls_ecp_restart_mul_ctx *ctx ) mbedtls_free( ctx->T ); } +#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG) + ecp_drbg_free( &ctx->drbg_ctx ); +#endif + ecp_restart_rsm_init( ctx ); } @@ -1897,7 +2057,9 @@ static int ecp_mul_comb_core( const mbedtls_ecp_group *grp, mbedtls_ecp_point *R i = d; MBEDTLS_MPI_CHK( ecp_select_comb( grp, R, T, T_size, x[i] ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &R->Z, 1 ) ); +#if defined(MBEDTLS_ECP_NO_INTERNAL_RNG) if( f_rng != 0 ) +#endif MBEDTLS_MPI_CHK( ecp_randomize_jac( grp, R, f_rng, p_rng ) ); } @@ -2018,6 +2180,7 @@ static int ecp_mul_comb_after_precomp( const mbedtls_ecp_group *grp, rs_ctx->rsm->state = ecp_rsm_final_norm; final_norm: + MBEDTLS_ECP_BUDGET( MBEDTLS_ECP_OPS_INV ); #endif /* * Knowledge of the jacobian coordinates may leak the last few bits of the @@ -2030,10 +2193,11 @@ final_norm: * * Avoid the leak by randomizing coordinates before we normalize them. */ +#if defined(MBEDTLS_ECP_NO_INTERNAL_RNG) if( f_rng != 0 ) +#endif MBEDTLS_MPI_CHK( ecp_randomize_jac( grp, RR, f_rng, p_rng ) ); - MBEDTLS_ECP_BUDGET( MBEDTLS_ECP_OPS_INV ); MBEDTLS_MPI_CHK( ecp_normalize_jac( grp, RR ) ); #if defined(MBEDTLS_ECP_RESTARTABLE) @@ -2104,11 +2268,44 @@ static int ecp_mul_comb( mbedtls_ecp_group *grp, mbedtls_ecp_point *R, int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char w, p_eq_g, i; size_t d; - unsigned char T_size, T_ok; - mbedtls_ecp_point *T; + unsigned char T_size = 0, T_ok = 0; + mbedtls_ecp_point *T = NULL; +#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG) + ecp_drbg_context drbg_ctx; + + ecp_drbg_init( &drbg_ctx ); +#endif ECP_RS_ENTER( rsm ); +#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG) + if( f_rng == NULL ) + { + /* Adjust pointers */ + f_rng = &ecp_drbg_random; +#if defined(MBEDTLS_ECP_RESTARTABLE) + if( rs_ctx != NULL && rs_ctx->rsm != NULL ) + p_rng = &rs_ctx->rsm->drbg_ctx; + else +#endif + p_rng = &drbg_ctx; + + /* Initialize internal DRBG if necessary */ +#if defined(MBEDTLS_ECP_RESTARTABLE) + if( rs_ctx == NULL || rs_ctx->rsm == NULL || + rs_ctx->rsm->drbg_seeded == 0 ) +#endif + { + const size_t m_len = ( grp->nbits + 7 ) / 8; + MBEDTLS_MPI_CHK( ecp_drbg_seed( p_rng, m, m_len ) ); + } +#if defined(MBEDTLS_ECP_RESTARTABLE) + if( rs_ctx != NULL && rs_ctx->rsm != NULL ) + rs_ctx->rsm->drbg_seeded = 1; +#endif + } +#endif /* !MBEDTLS_ECP_NO_INTERNAL_RNG */ + /* Is P the base point ? */ #if MBEDTLS_ECP_FIXED_POINT_OPTIM == 1 p_eq_g = ( mbedtls_mpi_cmp_mpi( &P->Y, &grp->G.Y ) == 0 && @@ -2180,6 +2377,10 @@ static int ecp_mul_comb( mbedtls_ecp_group *grp, mbedtls_ecp_point *R, cleanup: +#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG) + ecp_drbg_free( &drbg_ctx ); +#endif + /* does T belong to the group? */ if( T == grp->T ) T = NULL; @@ -2370,9 +2571,23 @@ static int ecp_mul_mxz( mbedtls_ecp_group *grp, mbedtls_ecp_point *R, unsigned char b; mbedtls_ecp_point RP; mbedtls_mpi PX; +#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG) + ecp_drbg_context drbg_ctx; + ecp_drbg_init( &drbg_ctx ); +#endif mbedtls_ecp_point_init( &RP ); mbedtls_mpi_init( &PX ); +#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG) + if( f_rng == NULL ) + { + const size_t m_len = ( grp->nbits + 7 ) / 8; + MBEDTLS_MPI_CHK( ecp_drbg_seed( &drbg_ctx, m, m_len ) ); + f_rng = &ecp_drbg_random; + p_rng = &drbg_ctx; + } +#endif /* !MBEDTLS_ECP_NO_INTERNAL_RNG */ + /* Save PX and read from P before writing to R, in case P == R */ MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &PX, &P->X ) ); MBEDTLS_MPI_CHK( mbedtls_ecp_copy( &RP, P ) ); @@ -2386,7 +2601,9 @@ static int ecp_mul_mxz( mbedtls_ecp_group *grp, mbedtls_ecp_point *R, MOD_ADD( RP.X ); /* Randomize coordinates of the starting point */ +#if defined(MBEDTLS_ECP_NO_INTERNAL_RNG) if( f_rng != NULL ) +#endif MBEDTLS_MPI_CHK( ecp_randomize_mxz( grp, &RP, f_rng, p_rng ) ); /* Loop invariant: R = result so far, RP = R + P */ @@ -2419,12 +2636,18 @@ static int ecp_mul_mxz( mbedtls_ecp_group *grp, mbedtls_ecp_point *R, * * Avoid the leak by randomizing coordinates before we normalize them. */ +#if defined(MBEDTLS_ECP_NO_INTERNAL_RNG) if( f_rng != NULL ) +#endif MBEDTLS_MPI_CHK( ecp_randomize_mxz( grp, R, f_rng, p_rng ) ); MBEDTLS_MPI_CHK( ecp_normalize_mxz( grp, R ) ); cleanup: +#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG) + ecp_drbg_free( &drbg_ctx ); +#endif + mbedtls_ecp_point_free( &RP ); mbedtls_mpi_free( &PX ); return( ret ); |