DHM: new functions to query the length of the modulus
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>
diff --git a/ChangeLog.d/dhm-fields.txt b/ChangeLog.d/dhm-fields.txt
new file mode 100644
index 0000000..620e3dc
--- /dev/null
+++ b/ChangeLog.d/dhm-fields.txt
@@ -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() .
diff --git a/include/mbedtls/dhm.h b/include/mbedtls/dhm.h
index 6c8ca03..3f7206e 100644
--- a/include/mbedtls/dhm.h
+++ b/include/mbedtls/dhm.h
@@ -96,7 +96,6 @@
*/
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. */
@@ -283,6 +282,26 @@
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.
*
diff --git a/library/dhm.c b/library/dhm.c
index accd5a8..2543be1 100644
--- a/library/dhm.c
+++ b/library/dhm.c
@@ -124,6 +124,16 @@
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 @@
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 @@
*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 @@
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_DHM_SET_GROUP_FAILED, ret ) );
}
- ctx->len = mbedtls_mpi_size( &ctx->P );
return( 0 );
}
@@ -287,7 +292,7 @@
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 @@
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 @@
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 @@
ret = 0;
- dhm->len = mbedtls_mpi_size( &dhm->P );
-
exit:
#if defined(MBEDTLS_PEM_PARSE_C)
mbedtls_pem_free( &pem );
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 12ed0fb..1bacd64 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -2553,7 +2553,7 @@
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 @@
/*
* 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 @@
/*
* 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 @@
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 )
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 4fe6b02..cf4b7c5 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -3049,7 +3049,7 @@
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 )
{
diff --git a/programs/pkey/dh_client.c b/programs/pkey/dh_client.c
index 101b0bb..d68dc24 100644
--- a/programs/pkey/dh_client.c
+++ b/programs/pkey/dh_client.c
@@ -192,7 +192,8 @@
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 @@
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 );
diff --git a/programs/pkey/dh_server.c b/programs/pkey/dh_server.c
index 745e68a..9d51c14 100644
--- a/programs/pkey/dh_server.c
+++ b/programs/pkey/dh_server.c
@@ -254,14 +254,14 @@
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;
diff --git a/programs/test/benchmark.c b/programs/test/benchmark.c
index e580fb2..148e6da 100644
--- a/programs/test/benchmark.c
+++ b/programs/test/benchmark.c
@@ -827,6 +827,7 @@
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 @@
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 ) );
diff --git a/tests/suites/test_suite_dhm.function b/tests/suites/test_suite_dhm.function
index c4d78de..7e01eb7 100644
--- a/tests/suites/test_suite_dhm.function
+++ b/tests/suites/test_suite_dhm.function
@@ -229,7 +229,8 @@
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 );