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Add derive_pms, completing first working version

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This commit is contained in:
Manuel Pégourié-Gonnard 2015-08-14 10:52:39 +02:00
parent 6449391852
commit 5f18829609
2 changed files with 104 additions and 2 deletions
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18
include/mbedtls/ecjpake.h
View File

@ -219,6 +219,24 @@ int mbedtls_ecjpake_tls_read_client_params( mbedtls_ecjpake_context *ctx,
const unsigned char *buf,
size_t len );
/*
* \brief Derive the Pre-Master Secret used by TLS
*
* \param ctx
* \param buf Buffer to write the contents to
* \param len Buffer size
* \param olen Will be updated with the number of bytes written
* \param f_rng RNG function
* \param p_rng RNG parameter
*
* \return 0 if successfull,
* a negative error code otherwise
*/
int mbedtls_ecjpake_tls_derive_pms( mbedtls_ecjpake_context *ctx,
unsigned char *buf, size_t len, size_t *olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng );
/*
* \brief Free a context's content
*

88
library/ecjpake.c
View File

@ -745,6 +745,59 @@ cleanup:
return( ret );
}
/*
* Derive PMS (7.4.2.7 / 7.4.2.8)
*/
int mbedtls_ecjpake_tls_derive_pms( mbedtls_ecjpake_context *ctx,
unsigned char *buf, size_t len, size_t *olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret;
mbedtls_ecp_point K, *X42;
mbedtls_mpi xbs, one;
unsigned char kx[MBEDTLS_ECP_MAX_BYTES];
size_t x_bytes;
*olen = mbedtls_md_get_size( ctx->md_info );
if( len < *olen )
return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
mbedtls_ecp_point_init( &K );
mbedtls_mpi_init( &xbs );
mbedtls_mpi_init( &one );
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &one, 1 ) );
X42 = ctx->role == MBEDTLS_ECJPAKE_CLIENT ? &ctx->X4 : &ctx->X2;
/*
* Client: K = ( Xs - X4 * x2 * s ) * x2
* Server: K = ( Xc - X2 * x4 * s ) * x4
* Unified: K = ( Xp - X42 * xb * x ) * xb
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &xbs, &ctx->xb, &ctx->s ) );
xbs.s *= -1;
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &xbs, &xbs, &ctx->grp.N ) );
MBEDTLS_MPI_CHK( mbedtls_ecp_muladd( &ctx->grp, &K,
&one, &ctx->Xp,
&xbs, X42 ) );
MBEDTLS_MPI_CHK( mbedtls_ecp_mul( &ctx->grp, &K, &ctx->xb, &K,
f_rng, p_rng ) );
/* PMS = SHA-256( K.X ) */
x_bytes = ( ctx->grp.pbits + 7 ) / 8;
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &K.X, kx, x_bytes ) );
MBEDTLS_MPI_CHK( mbedtls_md( ctx->md_info, kx, x_bytes, buf ) );
cleanup:
mbedtls_ecp_point_free( &K );
mbedtls_mpi_free( &xbs );
mbedtls_mpi_free( &one );
return( ret );
}
#if defined(MBEDTLS_SELF_TEST)
#if defined(MBEDTLS_PLATFORM_C)
@ -888,6 +941,12 @@ static const unsigned char ecjpake_test_cli_kx[] = {
0xcc, 0x38, 0xdb, 0xdc, 0xae, 0x60, 0xd9, 0xc5, 0x4c
};
static const unsigned char ecjpake_test_pms[] = {
0xf3, 0xd4, 0x7f, 0x59, 0x98, 0x44, 0xdb, 0x92, 0xa5, 0x69, 0xbb, 0xe7,
0x98, 0x1e, 0x39, 0xd9, 0x31, 0xfd, 0x74, 0x3b, 0xf2, 0x2e, 0x98, 0xf9,
0xb4, 0x38, 0xf7, 0x19, 0xd3, 0xc4, 0xf3, 0x51
};
/* For tests we don't need a secure RNG;
* use the LGC from Numerical Recipes for simplicity */
static int ecjpake_lgc( void *p, unsigned char *out, size_t len )
@ -926,8 +985,8 @@ int mbedtls_ecjpake_self_test( int verbose )
int ret;
mbedtls_ecjpake_context cli;
mbedtls_ecjpake_context srv;
unsigned char buf[512];
size_t len;
unsigned char buf[512], pms[32];
size_t len, pmslen;
mbedtls_ecjpake_init( &cli );
mbedtls_ecjpake_init( &srv );
@ -966,11 +1025,20 @@ int mbedtls_ecjpake_self_test( int verbose )
TEST_ASSERT( mbedtls_ecjpake_tls_read_server_params( &cli, buf, len ) == 0 );
TEST_ASSERT( mbedtls_ecjpake_tls_derive_pms( &cli,
pms, sizeof( pms ), &pmslen, ecjpake_lgc, NULL ) == 0 );
TEST_ASSERT( mbedtls_ecjpake_tls_write_client_params( &cli,
buf, sizeof( buf ), &len, ecjpake_lgc, NULL ) == 0 );
TEST_ASSERT( mbedtls_ecjpake_tls_read_client_params( &srv, buf, len ) == 0 );
TEST_ASSERT( mbedtls_ecjpake_tls_derive_pms( &srv,
buf, sizeof( buf ), &len, ecjpake_lgc, NULL ) == 0 );
TEST_ASSERT( len == pmslen );
TEST_ASSERT( memcmp( buf, pms, len ) == 0 );
if( verbose != 0 )
mbedtls_printf( "passed\n" );
@ -1016,6 +1084,22 @@ int mbedtls_ecjpake_self_test( int verbose )
ecjpake_test_cli_kx,
sizeof( ecjpake_test_cli_kx ) ) == 0 );
/* Server derives PMS */
TEST_ASSERT( mbedtls_ecjpake_tls_derive_pms( &srv,
buf, sizeof( buf ), &len, ecjpake_lgc, NULL ) == 0 );
TEST_ASSERT( len == sizeof( ecjpake_test_pms ) );
TEST_ASSERT( memcmp( buf, ecjpake_test_pms, len ) == 0 );
memset( buf, 0, len ); /* Avoid interferences with next step */
/* Client derives PMS */
TEST_ASSERT( mbedtls_ecjpake_tls_derive_pms( &cli,
buf, sizeof( buf ), &len, ecjpake_lgc, NULL ) == 0 );
TEST_ASSERT( len == sizeof( ecjpake_test_pms ) );
TEST_ASSERT( memcmp( buf, ecjpake_test_pms, len ) == 0 );
if( verbose != 0 )
mbedtls_printf( "passed\n" );