commit 71acc6e8d97dd6e4e3e3bbf5c99f1bcb2212ead7
author Gilles Peskine <Gilles.Peskine@arm.com> Thu May 27 22:50:53 2021 +0200
committer Gilles Peskine <Gilles.Peskine@arm.com> Tue Jun 15 00:12:37 2021 +0200
tree eb80a9ea87c7eb6e413f8e4dc0ae9a7edd8ac639
parent 487bbf68053143cdcb27cc60a91caf7738d86b68

New function mbedtls_dhm_get_value to copy a field of a DHM context

Reduce the need to break the DHM abstraction by accessing the context directly.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

library/dhm.c

diff --git a/library/dhm.c b/library/dhm.c
index 2543be1..cb9299f 100644
--- a/library/dhm.c
+++ b/library/dhm.c
@@ -134,6 +134,37 @@
     return( mbedtls_mpi_size( &ctx->P ) );
 }
 
+int mbedtls_dhm_get_value( mbedtls_mpi *dest,
+                           const mbedtls_dhm_context *ctx,
+                           mbedtls_dhm_parameter param )
+{
+    const mbedtls_mpi *src = NULL;
+    switch( param )
+    {
+        case MBEDTLS_DHM_PARAM_P:
+            src = &ctx->P;
+            break;
+        case MBEDTLS_DHM_PARAM_G:
+            src = &ctx->G;
+            break;
+        case MBEDTLS_DHM_PARAM_X:
+            src = &ctx->X;
+            break;
+        case MBEDTLS_DHM_PARAM_GX:
+            src = &ctx->GX;
+            break;
+        case MBEDTLS_DHM_PARAM_GY:
+            src = &ctx->GY;
+            break;
+        case MBEDTLS_DHM_PARAM_K:
+            src = &ctx->K;
+            break;
+        default:
+            return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
+    }
+    return( mbedtls_mpi_copy( dest, src ) );
+}
+
 /*
  * Parse the ServerKeyExchange parameters
  */

library/ssl_tls.c

diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 3bdc1cf..bef6864 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -3871,8 +3871,10 @@
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
-    if( ( ret = mbedtls_mpi_copy( &conf->dhm_P, &dhm_ctx->P ) ) != 0 ||
-        ( ret = mbedtls_mpi_copy( &conf->dhm_G, &dhm_ctx->G ) ) != 0 )
+    if( ( ret = mbedtls_dhm_get_value( &conf->dhm_P, dhm_ctx,
+                                       MBEDTLS_DHM_PARAM_P ) ) != 0 ||
+        ( ret = mbedtls_dhm_get_value( &conf->dhm_G, dhm_ctx,
+                                       MBEDTLS_DHM_PARAM_G ) ) != 0 )
     {
         mbedtls_mpi_free( &conf->dhm_P );
         mbedtls_mpi_free( &conf->dhm_G );