/* * Elliptic curve Diffie-Hellman * * Copyright (C) 2006-2014, Brainspark B.V. * * This file is part of mbed TLS (http://www.polarssl.org) * Lead Maintainer: Paul Bakker * * All rights reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ /* * References: * * SEC1 http://www.secg.org/index.php?action=secg,docs_secg * RFC 4492 */ #if !defined(POLARSSL_CONFIG_FILE) #include "polarssl/config.h" #else #include POLARSSL_CONFIG_FILE #endif #if defined(POLARSSL_ECDH_C) #include "polarssl/ecdh.h" /* * Generate public key: simple wrapper around ecp_gen_keypair */ int ecdh_gen_public( ecp_group *grp, mpi *d, ecp_point *Q, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { return ecp_gen_keypair( grp, d, Q, f_rng, p_rng ); } /* * Compute shared secret (SEC1 3.3.1) */ int ecdh_compute_shared( ecp_group *grp, mpi *z, const ecp_point *Q, const mpi *d, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { int ret; ecp_point P; ecp_point_init( &P ); /* * Make sure Q is a valid pubkey before using it */ MPI_CHK( ecp_check_pubkey( grp, Q ) ); MPI_CHK( ecp_mul( grp, &P, d, Q, f_rng, p_rng ) ); if( ecp_is_zero( &P ) ) { ret = POLARSSL_ERR_ECP_BAD_INPUT_DATA; goto cleanup; } MPI_CHK( mpi_copy( z, &P.X ) ); cleanup: ecp_point_free( &P ); return( ret ); } /* * Initialize context */ void ecdh_init( ecdh_context *ctx ) { memset( ctx, 0, sizeof( ecdh_context ) ); } /* * Free context */ void ecdh_free( ecdh_context *ctx ) { if( ctx == NULL ) return; ecp_group_free( &ctx->grp ); ecp_point_free( &ctx->Q ); ecp_point_free( &ctx->Qp ); ecp_point_free( &ctx->Vi ); ecp_point_free( &ctx->Vf ); mpi_free( &ctx->d ); mpi_free( &ctx->z ); mpi_free( &ctx->_d ); } /* * Setup and write the ServerKeyExhange parameters (RFC 4492) * struct { * ECParameters curve_params; * ECPoint public; * } ServerECDHParams; */ int ecdh_make_params( ecdh_context *ctx, size_t *olen, unsigned char *buf, size_t blen, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { int ret; size_t grp_len, pt_len; if( ctx == NULL || ctx->grp.pbits == 0 ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); if( ( ret = ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) ) != 0 ) return( ret ); if( ( ret = ecp_tls_write_group( &ctx->grp, &grp_len, buf, blen ) ) != 0 ) return( ret ); buf += grp_len; blen -= grp_len; if( ( ret = ecp_tls_write_point( &ctx->grp, &ctx->Q, ctx->point_format, &pt_len, buf, blen ) ) != 0 ) return( ret ); *olen = grp_len + pt_len; return( 0 ); } /* * Read the ServerKeyExhange parameters (RFC 4492) * struct { * ECParameters curve_params; * ECPoint public; * } ServerECDHParams; */ int ecdh_read_params( ecdh_context *ctx, const unsigned char **buf, const unsigned char *end ) { int ret; if( ( ret = ecp_tls_read_group( &ctx->grp, buf, end - *buf ) ) != 0 ) return( ret ); if( ( ret = ecp_tls_read_point( &ctx->grp, &ctx->Qp, buf, end - *buf ) ) != 0 ) return( ret ); return( 0 ); } /* * Get parameters from a keypair */ int ecdh_get_params( ecdh_context *ctx, const ecp_keypair *key, ecdh_side side ) { int ret; if( ( ret = ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 ) return( ret ); /* If it's not our key, just import the public part as Qp */ if( side == POLARSSL_ECDH_THEIRS ) return( ecp_copy( &ctx->Qp, &key->Q ) ); /* Our key: import public (as Q) and private parts */ if( side != POLARSSL_ECDH_OURS ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); if( ( ret = ecp_copy( &ctx->Q, &key->Q ) ) != 0 || ( ret = mpi_copy( &ctx->d, &key->d ) ) != 0 ) return( ret ); return( 0 ); } /* * Setup and export the client public value */ int ecdh_make_public( ecdh_context *ctx, size_t *olen, unsigned char *buf, size_t blen, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { int ret; if( ctx == NULL || ctx->grp.pbits == 0 ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); if( ( ret = ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) ) != 0 ) return( ret ); return ecp_tls_write_point( &ctx->grp, &ctx->Q, ctx->point_format, olen, buf, blen ); } /* * Parse and import the client's public value */ int ecdh_read_public( ecdh_context *ctx, const unsigned char *buf, size_t blen ) { int ret; const unsigned char *p = buf; if( ctx == NULL ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); if( ( ret = ecp_tls_read_point( &ctx->grp, &ctx->Qp, &p, blen ) ) != 0 ) return( ret ); if( (size_t)( p - buf ) != blen ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); return( 0 ); } /* * Derive and export the shared secret */ int ecdh_calc_secret( ecdh_context *ctx, size_t *olen, unsigned char *buf, size_t blen, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { int ret; if( ctx == NULL ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); if( ( ret = ecdh_compute_shared( &ctx->grp, &ctx->z, &ctx->Qp, &ctx->d, f_rng, p_rng ) ) != 0 ) { return( ret ); } if( mpi_size( &ctx->z ) > blen ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); *olen = ctx->grp.pbits / 8 + ( ( ctx->grp.pbits % 8 ) != 0 ); return mpi_write_binary( &ctx->z, buf, *olen ); } #if defined(POLARSSL_SELF_TEST) /* * Checkup routine */ int ecdh_self_test( int verbose ) { ((void) verbose ); return( 0 ); } #endif /* POLARSSL_SELF_TEST */ #endif /* POLARSSL_ECDH_C */