391 lines
12 KiB
C
391 lines
12 KiB
C
/*
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* Elliptic curve J-PAKE
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*
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* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of mbed TLS (https://tls.mbed.org)
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*/
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/*
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* We implement EC-JPAKE as defined in Chapter 7.4 of the Thread v1.0
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* Specification. References below are to this document.
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*/
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#if !defined(MBEDTLS_CONFIG_FILE)
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#include "mbedtls/config.h"
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#else
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#include MBEDTLS_CONFIG_FILE
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#endif
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#if defined(MBEDTLS_ECJPAKE_C)
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#include "mbedtls/ecjpake.h"
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#include <string.h>
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/*
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* Write a point plus its length to a buffer
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*/
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static int ecjpake_write_len_point( unsigned char **p,
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const unsigned char *end,
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const mbedtls_ecp_group *grp,
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const mbedtls_ecp_point *P )
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{
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int ret;
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size_t len;
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/* Need at least 4 for length plus 1 for point */
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if( end < *p || end - *p < 5 )
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return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
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ret = mbedtls_ecp_point_write_binary( grp, P, MBEDTLS_ECP_PF_UNCOMPRESSED,
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&len, *p + 4, end - ( *p + 4 ) );
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if( ret != 0 )
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return( ret );
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(*p)[0] = (unsigned char)( ( len >> 24 ) & 0xFF );
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(*p)[1] = (unsigned char)( ( len >> 16 ) & 0xFF );
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(*p)[2] = (unsigned char)( ( len >> 8 ) & 0xFF );
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(*p)[3] = (unsigned char)( ( len ) & 0xFF );
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*p += 4 + len;
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return( 0 );
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}
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/*
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* Size of the temporary buffer for ecjpake_hash:
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* 3 EC points plus their length, plus ID (6 bytes)
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*/
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#define ECJPAKE_HASH_BUF_LEN ( 3 * ( 4 + MBEDTLS_ECP_MAX_PT_LEN ) + 6 )
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/*
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* Compute hash for ZKP (7.4.2.2.2.1)
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*/
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static int ecjpake_hash( const mbedtls_md_info_t *md_info,
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const mbedtls_ecp_group *grp,
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const mbedtls_ecp_point *G,
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const mbedtls_ecp_point *V,
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const mbedtls_ecp_point *X,
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const char *id,
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mbedtls_mpi *h )
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{
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int ret;
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unsigned char buf[ECJPAKE_HASH_BUF_LEN];
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unsigned char *p = buf;
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const unsigned char *end = buf + sizeof( buf );
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const size_t id_len = strlen( id );
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unsigned char hash[MBEDTLS_MD_MAX_SIZE];
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/* Write things to temporary buffer */
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MBEDTLS_MPI_CHK( ecjpake_write_len_point( &p, end, grp, G ) );
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MBEDTLS_MPI_CHK( ecjpake_write_len_point( &p, end, grp, V ) );
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MBEDTLS_MPI_CHK( ecjpake_write_len_point( &p, end, grp, X ) );
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if( end < p || (size_t)( end - p ) < id_len )
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return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
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*p++ = (unsigned char)( ( id_len >> 24 ) & 0xFF );
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*p++ = (unsigned char)( ( id_len >> 16 ) & 0xFF );
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*p++ = (unsigned char)( ( id_len >> 8 ) & 0xFF );
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*p++ = (unsigned char)( ( id_len ) & 0xFF );
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memcpy( p, id, id_len );
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p += id_len;
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/* Compute hash */
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mbedtls_md( md_info, buf, p - buf, hash );
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/* Turn it into an integer mod n */
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MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( h, hash,
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mbedtls_md_get_size( md_info ) ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( h, h, &grp->N ) );
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cleanup:
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return( ret );
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}
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/*
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* Generate ZKP (7.4.2.3.2) and write it as ECSchnorrZKP (7.4.2.2.2)
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*/
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static int ecjpake_zkp_write( const mbedtls_md_info_t *md_info,
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const mbedtls_ecp_group *grp,
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const mbedtls_ecp_point *G,
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const mbedtls_mpi *x,
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const mbedtls_ecp_point *X,
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const char *id,
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unsigned char **p,
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const unsigned char *end,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng )
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{
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int ret;
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mbedtls_ecp_point V;
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mbedtls_mpi v;
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mbedtls_mpi h; /* later recycled to hold r */
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size_t len;
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if( end < *p )
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return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
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mbedtls_ecp_point_init( &V );
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mbedtls_mpi_init( &v );
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mbedtls_mpi_init( &h );
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/* Compute signature */
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MBEDTLS_MPI_CHK( mbedtls_ecp_gen_keypair_base( (mbedtls_ecp_group *) grp,
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G, &v, &V, f_rng, p_rng ) );
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MBEDTLS_MPI_CHK( ecjpake_hash( md_info, grp, G, &V, X, id, &h ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &h, &h, x ) ); /* x*h */
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MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &h, &v, &h ) ); /* v - x*h */
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MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &h, &h, &grp->N ) ); /* r */
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/* Write it out */
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MBEDTLS_MPI_CHK( mbedtls_ecp_tls_write_point( grp, &V,
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MBEDTLS_ECP_PF_UNCOMPRESSED, &len, *p, end - *p ) );
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*p += len;
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len = mbedtls_mpi_size( &h ); /* actually r */
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if( end < *p || (size_t)( end - *p ) < 1 + len || len > 255 )
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return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
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*(*p)++ = (unsigned char)( len & 0xFF );
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MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &h, *p, len ) ); /* r */
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*p += len;
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cleanup:
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mbedtls_ecp_point_free( &V );
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mbedtls_mpi_free( &v );
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mbedtls_mpi_free( &h );
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return( ret );
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}
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/*
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* Parse a ECShnorrZKP (7.4.2.2.2) and verify it (7.4.2.3.3)
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*/
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static int ecjpake_zkp_read( const mbedtls_md_info_t *md_info,
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const mbedtls_ecp_group *grp,
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const mbedtls_ecp_point *G,
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const mbedtls_ecp_point *X,
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const char *id,
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unsigned char **p,
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const unsigned char *end )
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{
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int ret;
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mbedtls_ecp_point V, VV;
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mbedtls_mpi r, h;
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size_t r_len;
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mbedtls_ecp_point_init( &V );
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mbedtls_ecp_point_init( &VV );
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mbedtls_mpi_init( &r );
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mbedtls_mpi_init( &h );
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/*
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* struct {
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* ECPoint V;
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* opaque r<1..2^8-1>;
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* } ECSchnorrZKP;
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*/
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if( end < *p )
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return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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MBEDTLS_MPI_CHK( mbedtls_ecp_tls_read_point( grp, &V,
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(const unsigned char **) p, end - *p ) );
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if( end < *p || (size_t)( end - *p ) < 1 )
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return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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r_len = *(*p)++;
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if( end < *p || (size_t)( end - *p ) < r_len )
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return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &r, *p, r_len ) );
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*p += r_len;
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/*
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* Verification
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*/
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MBEDTLS_MPI_CHK( ecjpake_hash( md_info, grp, G, &V, X, id, &h ) );
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MBEDTLS_MPI_CHK( mbedtls_ecp_muladd( (mbedtls_ecp_group *) grp,
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&VV, &h, X, &r, G ) );
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if( mbedtls_ecp_point_cmp( &VV, &V ) != 0 )
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return( MBEDTLS_ERR_ECP_VERIFY_FAILED );
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cleanup:
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mbedtls_ecp_point_free( &V );
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mbedtls_ecp_point_free( &VV );
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mbedtls_mpi_free( &r );
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mbedtls_mpi_free( &h );
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return( ret );
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}
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#if defined(MBEDTLS_SELF_TEST)
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#if defined(MBEDTLS_PLATFORM_C)
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#include "mbedtls/platform.h"
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#else
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#include <stdio.h>
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#define mbedtls_printf printf
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#endif
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#if !defined(MBEDTLS_ECP_DP_SECP256R1_ENABLED) || \
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!defined(MBEDTLS_SHA256_C)
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int mbedtls_ecjpake_self_test( int verbose )
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{
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(void) verbose;
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return( 0 );
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}
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#else
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static const unsigned char ecjpake_test_X[] = {
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0x04, 0xac, 0xcf, 0x01, 0x06, 0xef, 0x85, 0x8f, 0xa2, 0xd9, 0x19, 0x33,
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0x13, 0x46, 0x80, 0x5a, 0x78, 0xb5, 0x8b, 0xba, 0xd0, 0xb8, 0x44, 0xe5,
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0xc7, 0x89, 0x28, 0x79, 0x14, 0x61, 0x87, 0xdd, 0x26, 0x66, 0xad, 0xa7,
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0x81, 0xbb, 0x7f, 0x11, 0x13, 0x72, 0x25, 0x1a, 0x89, 0x10, 0x62, 0x1f,
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0x63, 0x4d, 0xf1, 0x28, 0xac, 0x48, 0xe3, 0x81, 0xfd, 0x6e, 0xf9, 0x06,
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0x07, 0x31, 0xf6, 0x94, 0xa4
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};
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static const unsigned char ecjpake_test_zkp[] = {
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0x41, 0x04, 0x1d, 0xd0, 0xbd, 0x5d, 0x45, 0x66, 0xc9, 0xbe, 0xd9, 0xce,
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0x7d, 0xe7, 0x01, 0xb5, 0xe8, 0x2e, 0x08, 0xe8, 0x4b, 0x73, 0x04, 0x66,
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0x01, 0x8a, 0xb9, 0x03, 0xc7, 0x9e, 0xb9, 0x82, 0x17, 0x22, 0x36, 0xc0,
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0xc1, 0x72, 0x8a, 0xe4, 0xbf, 0x73, 0x61, 0x0d, 0x34, 0xde, 0x44, 0x24,
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0x6e, 0xf3, 0xd9, 0xc0, 0x5a, 0x22, 0x36, 0xfb, 0x66, 0xa6, 0x58, 0x3d,
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0x74, 0x49, 0x30, 0x8b, 0xab, 0xce, 0x20, 0x72, 0xfe, 0x16, 0x66, 0x29,
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0x92, 0xe9, 0x23, 0x5c, 0x25, 0x00, 0x2f, 0x11, 0xb1, 0x50, 0x87, 0xb8,
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0x27, 0x38, 0xe0, 0x3c, 0x94, 0x5b, 0xf7, 0xa2, 0x99, 0x5d, 0xda, 0x1e,
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0x98, 0x34, 0x58
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};
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/* For tests we don't need a secure RNG;
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* use the LGC from Numerical Recipes for simplicity */
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static int ecjpake_lgc( void *p, unsigned char *out, size_t len )
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{
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static uint32_t x = 42;
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(void) p;
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while( len > 0 )
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{
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size_t use_len = len > 4 ? 4 : len;
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x = 1664525 * x + 1013904223;
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memcpy( out, &x, use_len );
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out += use_len;
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len -= use_len;
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}
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return( 0 );
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}
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/*
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* Checkup routine
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*/
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int mbedtls_ecjpake_self_test( int verbose )
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{
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int ret;
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mbedtls_ecp_group grp;
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mbedtls_ecp_point X;
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mbedtls_mpi x;
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const mbedtls_md_info_t *md_info;
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unsigned char buf[1000];
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unsigned char *p;
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const unsigned char *end;
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mbedtls_ecp_group_init( &grp );
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mbedtls_ecp_point_init( &X );
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mbedtls_mpi_init( &x );
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/* Common to all tests */
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md_info = mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 );
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MBEDTLS_MPI_CHK( mbedtls_ecp_group_load( &grp, MBEDTLS_ECP_DP_SECP256R1 ) );
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if( verbose != 0 )
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mbedtls_printf( " ECJPAKE test #1 (zkp read): " );
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MBEDTLS_MPI_CHK( mbedtls_ecp_point_read_binary( &grp, &X,
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ecjpake_test_X,
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sizeof( ecjpake_test_X ) ) );
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p = (unsigned char *) ecjpake_test_zkp;
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end = ecjpake_test_zkp + sizeof( ecjpake_test_zkp );
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MBEDTLS_MPI_CHK( ecjpake_zkp_read( md_info, &grp, &grp.G, &X, "client",
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&p, end ) );
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/* Corrupt proof */
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memcpy( buf, ecjpake_test_zkp, sizeof( ecjpake_test_zkp ) );
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buf[sizeof( ecjpake_test_zkp ) - 1]--;
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p = buf;
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end = buf + sizeof( ecjpake_test_zkp );
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ret = ecjpake_zkp_read( md_info, &grp, &grp.G, &X, "client", &p, end );
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if( ret != MBEDTLS_ERR_ECP_VERIFY_FAILED )
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{
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ret = 1;
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goto cleanup;
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}
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ret = 0;
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if( verbose != 0 )
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mbedtls_printf( "passed\n" );
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if( verbose != 0 )
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mbedtls_printf( " ECJPAKE test #2 (zkp write/read): " );
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MBEDTLS_MPI_CHK( mbedtls_ecp_gen_keypair_base( &grp, &grp.G, &x, &X,
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ecjpake_lgc, NULL ) );
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p = buf;
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MBEDTLS_MPI_CHK( ecjpake_zkp_write( md_info, &grp, &grp.G, &x, &X, "client",
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&p, buf + sizeof( buf ),
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ecjpake_lgc, NULL ) );
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p = buf;
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MBEDTLS_MPI_CHK( ecjpake_zkp_read( md_info, &grp, &grp.G, &X, "client",
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&p, buf + sizeof( buf ) ) );
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if( verbose != 0 )
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mbedtls_printf( "passed\n" );
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cleanup:
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mbedtls_ecp_group_free( &grp );
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mbedtls_ecp_point_free( &X );
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mbedtls_mpi_free( &x );
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if( ret != 0 )
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{
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if( verbose != 0 )
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mbedtls_printf( "failed\n" );
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ret = 1;
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}
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if( verbose != 0 )
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mbedtls_printf( "\n" );
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return( ret );
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}
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#endif /* MBEDTLS_ECP_DP_SECP256R1_ENABLED && MBEDTLS_SHA256_C */
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#endif /* MBEDTLS_SELF_TEST */
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#endif /* MBEDTLS_ECJPAKE_C */
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