ECDH: not restartable unless explicitly enabled
This is mainly for the benefit of SSL modules, which only supports restart in a limited number of cases. In the other cases (ECDHE_PSK) it would currently return ERR_ECP_IN_PROGRESS and the user would thus call ssl_handshake() again, but the SSL code wouldn't handle state properly and things would go wrong in possibly unexpected ways. This is undesirable, so it should be possible for the SSL module to choose if ECDHE should behave the old or the new way. Not that it also brings ECDHE more in line with the other modules which already have that choice available (by passing a NULL or valid restart context).
This commit is contained in:
Manuel Pégourié-Gonnard
parent
1f1f2a1ca6
commit
23e416261c
5 changed files with 68 additions and 12 deletions
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@ -53,6 +53,7 @@ typedef struct
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mbedtls_ecp_point Vf; /*!< un-blinding value (for later) */
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mbedtls_mpi _d; /*!< previous d (for later) */
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#if defined(MBEDTLS_ECP_RESTARTABLE)
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int restart_enabled; /*!< enable restartalbe EC computations? */
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mbedtls_ecp_restart_ctx rs; /*!< restart context for EC computations */
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#endif
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}
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@ -220,6 +221,22 @@ int mbedtls_ecdh_calc_secret( mbedtls_ecdh_context *ctx, size_t *olen,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng );
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#if defined(MBEDTLS_ECP_RESTARTABLE)
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/**
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* \brief Enable restartable EC computations for this context.
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* (Default: disabled.)
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*
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* \sa \c mbedtls_ecp_set_max_ops()
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*
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* \note It is not possible to safely disable restartable
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* computations once enabled, except by free-ing the context,
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* which cancels possible in-progress operations.
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*
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* \param ctx ECDH context
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*/
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void mbedtls_ecdh_enable_restart( mbedtls_ecdh_context *ctx );
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#endif /* MBEDTLS_ECP_RESTARTABLE */
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#ifdef __cplusplus
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}
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#endif
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@ -155,6 +155,16 @@ void mbedtls_ecdh_free( mbedtls_ecdh_context *ctx )
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#endif
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}
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#if defined(MBEDTLS_ECP_RESTARTABLE)
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/*
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* Enable restartable operations for context
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*/
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void mbedtls_ecdh_enable_restart( mbedtls_ecdh_context *ctx )
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{
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ctx->restart_enabled = 1;
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}
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#endif
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/*
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* Setup and write the ServerKeyExhange parameters (RFC 4492)
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* struct {
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@ -175,7 +185,8 @@ int mbedtls_ecdh_make_params( mbedtls_ecdh_context *ctx, size_t *olen,
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return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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#if defined(MBEDTLS_ECP_RESTARTABLE)
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rs_ctx = &ctx->rs;
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if( ctx->restart_enabled )
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rs_ctx = &ctx->rs;
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#endif
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if( ( ret = ecdh_gen_public_restartable( &ctx->grp, &ctx->d, &ctx->Q,
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@ -260,7 +271,8 @@ int mbedtls_ecdh_make_public( mbedtls_ecdh_context *ctx, size_t *olen,
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return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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#if defined(MBEDTLS_ECP_RESTARTABLE)
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rs_ctx = &ctx->rs;
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if( ctx->restart_enabled )
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rs_ctx = &ctx->rs;
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#endif
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if( ( ret = ecdh_gen_public_restartable( &ctx->grp, &ctx->d, &ctx->Q,
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@ -307,7 +319,8 @@ int mbedtls_ecdh_calc_secret( mbedtls_ecdh_context *ctx, size_t *olen,
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return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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#if defined(MBEDTLS_ECP_RESTARTABLE)
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rs_ctx = &ctx->rs;
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if( ctx->restart_enabled )
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rs_ctx = &ctx->rs;
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#endif
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if( ( ret = ecdh_compute_shared_restartable( &ctx->grp,
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@ -2902,6 +2902,9 @@ static int ssl_write_client_key_exchange( mbedtls_ssl_context *ssl )
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i = 4;
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#if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
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if( ssl->handshake->ec_restart_enabled)
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mbedtls_ecdh_enable_restart( &ssl->handshake->ecdh_ctx );
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if( ssl->handshake->ecrs_state == ssl_ecrs_ecdh_public_done )
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goto ecdh_calc_secret;
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#endif
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@ -38,18 +38,34 @@ ECDH exchange #2
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depends_on:MBEDTLS_ECP_DP_SECP521R1_ENABLED
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ecdh_exchange:MBEDTLS_ECP_DP_SECP521R1
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ECDH restartable rfc 5903 p256 restart disabled
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ECDH restartable rfc 5903 p256 restart enabled max_ops=0
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depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":0:0:0
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":1:0:0:0
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ECDH restartable rfc 5903 p256 restart max_ops=1
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ECDH restartable rfc 5903 p256 restart enabled max_ops=1
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depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":1:1:10000
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":1:1:1:10000
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ECDH restartable rfc 5903 p256 restart max_ops=10000
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ECDH restartable rfc 5903 p256 restart enabled max_ops=10000
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depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":10000:0:0
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":1:10000:0:0
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ECDH restartable rfc 5903 p256 restart max_ops=250
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ECDH restartable rfc 5903 p256 restart enabled max_ops=250
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depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":250:2:32
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":1:250:2:32
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ECDH restartable rfc 5903 p256 restart disabled max_ops=0
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depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":0:0:0:0
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ECDH restartable rfc 5903 p256 restart disabled max_ops=1
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depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":0:1:0:0
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ECDH restartable rfc 5903 p256 restart disabled max_ops=10000
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depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":0:10000:0:0
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ECDH restartable rfc 5903 p256 restart disabled max_ops=250
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depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
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ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":0:250:0:0
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@ -161,7 +161,7 @@ exit:
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/* BEGIN_CASE depends_on:MBEDTLS_ECP_RESTARTABLE */
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void ecdh_restart( int id, char *dA_str, char *dB_str, char *z_str,
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int max_ops, int min_restart, int max_restart )
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int enable, int max_ops, int min_restart, int max_restart )
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{
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int ret;
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mbedtls_ecdh_context srv, cli;
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@ -192,8 +192,15 @@ void ecdh_restart( int id, char *dA_str, char *dB_str, char *z_str,
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* as in ecdh_primitive_test_vec */
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TEST_ASSERT( srv.grp.nbits % 8 == 0 );
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/* set up restart parameters */
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mbedtls_ecp_set_max_ops( max_ops );
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if( enable)
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{
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mbedtls_ecdh_enable_restart( &srv );
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mbedtls_ecdh_enable_restart( &cli );
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}
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/* server writes its paramaters */
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memset( buf, 0x00, sizeof( buf ) );
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len = 0;
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