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DHM: new functions to query the length of the modulus

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Add two functions mbedtls_dhm_get_len() and mbedtls_dhm_get_bitlen() to
query the length of the modulus in bytes or bits.

Remove the len field: the cost of calling mbedtls_dhm_get_len() each time
it's needed is negligible, and this improves the abstraction of the DHM
module.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2021-05-27 22:17:07 +02:00
parent 85b1bc65a0
commit 487bbf6805
9 changed files with 58 additions and 26 deletions
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7
ChangeLog.d/dhm-fields.txt Normal file
View File

@ -0,0 +1,7 @@
Features
* The new functions mbedtls_dhm_get_len() and mbedtls_dhm_get_bitlen()
query the size of the modulus in a Diffie-Hellman context.
API changes
* Instead of accessing the len field of a DHM context, which is no longer
supported, use the new function mbedtls_dhm_get_len() .

21
include/mbedtls/dhm.h
View File

@ -96,7 +96,6 @@ extern "C" {
*/
typedef struct mbedtls_dhm_context
{
size_t MBEDTLS_PRIVATE(len); /*!< The size of \p P in Bytes. */
mbedtls_mpi MBEDTLS_PRIVATE(P); /*!< The prime modulus. */
mbedtls_mpi MBEDTLS_PRIVATE(G); /*!< The generator. */
mbedtls_mpi MBEDTLS_PRIVATE(X); /*!< Our secret value. */
@ -282,6 +281,26 @@ int mbedtls_dhm_calc_secret( mbedtls_dhm_context *ctx,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng );
/**
* \brief This function returns the size of the prime modulus in bits.
*
* \param ctx The DHM context to query.
*
* \return The size of the prime modulus in bits,
* i.e. the number n such that 2^(n-1) <= P < 2^n.
*/
size_t mbedtls_dhm_get_bitlen( const mbedtls_dhm_context *ctx );
/**
* \brief This function returns the size of the prime modulus in bytes.
*
* \param ctx The DHM context to query.
*
* \return The size of the prime modulus in bytes,
* i.e. the number n such that 2^(8*(n-1)) <= P < 2^(8*n).
*/
size_t mbedtls_dhm_get_len( const mbedtls_dhm_context *ctx );
/**
* \brief This function frees and clears the components
* of a DHM context.

23
library/dhm.c
View File

@ -124,6 +124,16 @@ void mbedtls_dhm_init( mbedtls_dhm_context *ctx )
memset( ctx, 0, sizeof( mbedtls_dhm_context ) );
}
size_t mbedtls_dhm_get_bitlen( const mbedtls_dhm_context *ctx )
{
return( mbedtls_mpi_bitlen( &ctx->P ) );
}
size_t mbedtls_dhm_get_len( const mbedtls_dhm_context *ctx )
{
return( mbedtls_mpi_size( &ctx->P ) );
}
/*
* Parse the ServerKeyExchange parameters
*/
@ -144,8 +154,6 @@ int mbedtls_dhm_read_params( mbedtls_dhm_context *ctx,
if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
return( ret );
ctx->len = mbedtls_mpi_size( &ctx->P );
return( 0 );
}
@ -247,8 +255,6 @@ int mbedtls_dhm_make_params( mbedtls_dhm_context *ctx, int x_size,
*olen = p - output;
ctx->len = n1;
cleanup:
if( ret != 0 && ret > -128 )
ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED, ret );
@ -273,7 +279,6 @@ int mbedtls_dhm_set_group( mbedtls_dhm_context *ctx,
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_DHM_SET_GROUP_FAILED, ret ) );
}
ctx->len = mbedtls_mpi_size( &ctx->P );
return( 0 );
}
@ -287,7 +292,7 @@ int mbedtls_dhm_read_public( mbedtls_dhm_context *ctx,
DHM_VALIDATE_RET( ctx != NULL );
DHM_VALIDATE_RET( input != NULL );
if( ilen < 1 || ilen > ctx->len )
if( ilen < 1 || ilen > mbedtls_dhm_get_len( ctx ) )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
if( ( ret = mbedtls_mpi_read_binary( &ctx->GY, input, ilen ) ) != 0 )
@ -309,7 +314,7 @@ int mbedtls_dhm_make_public( mbedtls_dhm_context *ctx, int x_size,
DHM_VALIDATE_RET( output != NULL );
DHM_VALIDATE_RET( f_rng != NULL );
if( olen < 1 || olen > ctx->len )
if( olen < 1 || olen > mbedtls_dhm_get_len( ctx ) )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
ret = dhm_make_common( ctx, x_size, f_rng, p_rng );
@ -408,7 +413,7 @@ int mbedtls_dhm_calc_secret( mbedtls_dhm_context *ctx,
DHM_VALIDATE_RET( output != NULL );
DHM_VALIDATE_RET( olen != NULL );
if( output_size < ctx->len )
if( output_size < mbedtls_dhm_get_len( ctx ) )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
@ -564,8 +569,6 @@ int mbedtls_dhm_parse_dhm( mbedtls_dhm_context *dhm, const unsigned char *dhmin,
ret = 0;
dhm->len = mbedtls_mpi_size( &dhm->P );
exit:
#if defined(MBEDTLS_PEM_PARSE_C)
mbedtls_pem_free( &pem );

10
library/ssl_cli.c
View File

@ -2553,7 +2553,7 @@ static int ssl_parse_server_dh_params( mbedtls_ssl_context *ssl,
return( ret );
}
dhm_actual_bitlen = mbedtls_mpi_bitlen( &ssl->handshake->dhm_ctx.P );
dhm_actual_bitlen = mbedtls_dhm_get_bitlen( &ssl->handshake->dhm_ctx );
if( dhm_actual_bitlen < ssl->conf->dhm_min_bitlen )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "DHM prime too short: %" MBEDTLS_PRINTF_SIZET " < %u",
@ -3588,14 +3588,14 @@ static int ssl_write_client_key_exchange( mbedtls_ssl_context *ssl )
/*
* DHM key exchange -- send G^X mod P
*/
content_len = ssl->handshake->dhm_ctx.len;
content_len = mbedtls_dhm_get_len( &ssl->handshake->dhm_ctx );
ssl->out_msg[4] = (unsigned char)( content_len >> 8 );
ssl->out_msg[5] = (unsigned char)( content_len );
header_len = 6;
ret = mbedtls_dhm_make_public( &ssl->handshake->dhm_ctx,
(int) mbedtls_mpi_size( &ssl->handshake->dhm_ctx.P ),
(int) mbedtls_dhm_get_len( &ssl->handshake->dhm_ctx ),
&ssl->out_msg[header_len], content_len,
ssl->conf->f_rng, ssl->conf->p_rng );
if( ret != 0 )
@ -3848,7 +3848,7 @@ ecdh_calc_secret:
/*
* ClientDiffieHellmanPublic public (DHM send G^X mod P)
*/
content_len = ssl->handshake->dhm_ctx.len;
content_len = mbedtls_dhm_get_len( &ssl->handshake->dhm_ctx );
if( header_len + 2 + content_len >
MBEDTLS_SSL_OUT_CONTENT_LEN )
@ -3862,7 +3862,7 @@ ecdh_calc_secret:
ssl->out_msg[header_len++] = (unsigned char)( content_len );
ret = mbedtls_dhm_make_public( &ssl->handshake->dhm_ctx,
(int) mbedtls_mpi_size( &ssl->handshake->dhm_ctx.P ),
(int) mbedtls_dhm_get_len( &ssl->handshake->dhm_ctx ),
&ssl->out_msg[header_len], content_len,
ssl->conf->f_rng, ssl->conf->p_rng );
if( ret != 0 )

2
library/ssl_srv.c
View File

@ -3049,7 +3049,7 @@ static int ssl_prepare_server_key_exchange( mbedtls_ssl_context *ssl,
if( ( ret = mbedtls_dhm_make_params(
&ssl->handshake->dhm_ctx,
(int) mbedtls_mpi_size( &ssl->handshake->dhm_ctx.P ),
(int) mbedtls_dhm_get_len( &ssl->handshake->dhm_ctx ),
ssl->out_msg + ssl->out_msglen, &len,
ssl->conf->f_rng, ssl->conf->p_rng ) ) != 0 )
{

7
programs/pkey/dh_client.c
View File

@ -192,7 +192,8 @@ int main( void )
goto exit;
}
if( dhm.MBEDTLS_PRIVATE(len) < 64 || dhm.MBEDTLS_PRIVATE(len) > 512 )
n = mbedtls_dhm_get_len( &dhm );
if( n < 64 || n > 512 )
{
mbedtls_printf( " failed\n ! Invalid DHM modulus size\n\n" );
goto exit;
@ -232,8 +233,8 @@ int main( void )
mbedtls_printf( "\n . Sending own public value to server" );
fflush( stdout );
n = dhm.MBEDTLS_PRIVATE(len);
if( ( ret = mbedtls_dhm_make_public( &dhm, (int) dhm.MBEDTLS_PRIVATE(len), buf, n,
n = mbedtls_dhm_get_len( &dhm );
if( ( ret = mbedtls_dhm_make_public( &dhm, (int) n, buf, n,
mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_dhm_make_public returned %d\n\n", ret );

4
programs/pkey/dh_server.c
View File

@ -254,14 +254,14 @@ int main( void )
memset( buf, 0, sizeof( buf ) );
n = dhm.MBEDTLS_PRIVATE(len);
n = mbedtls_dhm_get_len( &dhm );
if( ( ret = mbedtls_net_recv( &client_fd, buf, n ) ) != (int) n )
{
mbedtls_printf( " failed\n ! mbedtls_net_recv returned %d\n\n", ret );
goto exit;
}
if( ( ret = mbedtls_dhm_read_public( &dhm, buf, dhm.MBEDTLS_PRIVATE(len) ) ) != 0 )
if( ( ret = mbedtls_dhm_read_public( &dhm, buf, n ) ) != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_dhm_read_public returned %d\n\n", ret );
goto exit;

7
programs/test/benchmark.c
View File

@ -827,6 +827,7 @@ int main( int argc, char *argv[] )
mbedtls_dhm_context dhm;
size_t olen;
size_t n;
for( i = 0; (size_t) i < sizeof( dhm_sizes ) / sizeof( dhm_sizes[0] ); i++ )
{
mbedtls_dhm_init( &dhm );
@ -839,14 +840,14 @@ int main( int argc, char *argv[] )
mbedtls_exit( 1 );
}
dhm.len = mbedtls_mpi_size( &dhm.P );
mbedtls_dhm_make_public( &dhm, (int) dhm.len, buf, dhm.len, myrand, NULL );
n = mbedtls_mpi_size( &dhm.P );
mbedtls_dhm_make_public( &dhm, (int) n, buf, n, myrand, NULL );
if( mbedtls_mpi_copy( &dhm.GY, &dhm.GX ) != 0 )
mbedtls_exit( 1 );
mbedtls_snprintf( title, sizeof( title ), "DHE-%d", dhm_sizes[i] );
TIME_PUBLIC( title, "handshake",
ret |= mbedtls_dhm_make_public( &dhm, (int) dhm.len, buf, dhm.len,
ret |= mbedtls_dhm_make_public( &dhm, (int) n, buf, n,
myrand, NULL );
ret |= mbedtls_dhm_calc_secret( &dhm, buf, sizeof( buf ), &olen, myrand, NULL ) );

3
tests/suites/test_suite_dhm.function
View File

@ -229,7 +229,8 @@ void dhm_file( char * filename, char * p, char * g, int len )
TEST_ASSERT( mbedtls_dhm_parse_dhmfile( &ctx, filename ) == 0 );
TEST_ASSERT( ctx.len == (size_t) len );
TEST_EQUAL( mbedtls_dhm_get_len( &ctx ), (size_t) len );
TEST_EQUAL( mbedtls_dhm_get_bitlen( &ctx ), mbedtls_mpi_bitlen( &P ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &ctx.P, &P ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &ctx.G, &G ) == 0 );