commit 487bbf68053143cdcb27cc60a91caf7738d86b68
author Gilles Peskine <Gilles.Peskine@arm.com> Thu May 27 22:17:07 2021 +0200
committer Gilles Peskine <Gilles.Peskine@arm.com> Tue Jun 15 00:12:37 2021 +0200
tree ecad368d220314fbe6134c3bf3cfc6664096a7bd
parent 85b1bc65a0f84aa6e453f316ce73e778b2cf8717

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>

programs/pkey/dh_client.c

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 );

programs/pkey/dh_server.c

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;

programs/test/benchmark.c

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 ) );