From 1028b74cff9607cdbcd3635378bb90a7c7a6153e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Manuel=20P=C3=A9gouri=C3=A9-Gonnard?= <mpg@elzevir.fr>
Date: Wed, 6 May 2015 17:33:07 +0100
Subject: [PATCH] Upgrade default DHM params size

---
 ChangeLog                  |  1 +
 include/mbedtls/ssl.h      |  4 ++--
 library/ssl_srv.c          |  6 ++++++
 library/ssl_tls.c          | 36 ++++++++++++++++++++----------------
 programs/ssl/ssl_server2.c |  4 ----
 5 files changed, 29 insertions(+), 22 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 28093ae01..2e5a54f89 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -84,6 +84,7 @@ Default behavior changes
    * Support for RSA_ALT contexts in the PK layer is now optional. Since is is
      enabled in the default configuration, this is only noticeable if using a
      custom config.h
+   * Default DHM parameters server-side upgraded from 1024 to 2048 bits.
 
 Reauirement changes
    * The minimum MSVC version required is now 2010 (better C99 support).
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 92420b533..4782cd539 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1621,11 +1621,11 @@ void mbedtls_ssl_set_psk_cb( mbedtls_ssl_config *conf,
                      void *p_psk );
 #endif /* MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED */
 
-#if defined(MBEDTLS_DHM_C)
+#if defined(MBEDTLS_DHM_C) && defined(MBEDTLS_SSL_SRV_C)
 /**
  * \brief          Set the Diffie-Hellman public P and G values,
  *                 read as hexadecimal strings (server-side only)
- *                 (Default: MBEDTLS_DHM_RFC5114_MODP_1024_[PG])
+ *                 (Default: MBEDTLS_DHM_RFC5114_MODP_2048_[PG])
  *
  * \param conf     SSL configuration
  * \param dhm_P    Diffie-Hellman-Merkle modulus
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 59fce958b..c537fe4b2 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -2871,6 +2871,12 @@ static int ssl_write_server_key_exchange( mbedtls_ssl_context *ssl )
     if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_RSA ||
         ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_PSK )
     {
+        if( ssl->conf->dhm_P.p == NULL || ssl->conf->dhm_G.p == NULL )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "no DH parameters set" ) );
+            return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+        }
+
         /*
          * Ephemeral DH parameters:
          *
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 229536dd3..114f5ae30 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -5400,11 +5400,13 @@ int mbedtls_ssl_set_dh_param( mbedtls_ssl_config *conf, const char *dhm_P, const
 {
     int ret;
 
-    if( ( ret = mbedtls_mpi_read_string( &conf->dhm_P, 16, dhm_P ) ) != 0 )
-        return( ret );
-
-    if( ( ret = mbedtls_mpi_read_string( &conf->dhm_G, 16, dhm_G ) ) != 0 )
+    if( ( ret = mbedtls_mpi_read_string( &conf->dhm_P, 16, dhm_P ) ) != 0 ||
+        ( ret = mbedtls_mpi_read_string( &conf->dhm_G, 16, dhm_G ) ) != 0 )
+    {
+        mbedtls_mpi_free( &conf->dhm_P );
+        mbedtls_mpi_free( &conf->dhm_G );
         return( ret );
+    }
 
     return( 0 );
 }
@@ -5413,11 +5415,13 @@ int mbedtls_ssl_set_dh_param_ctx( mbedtls_ssl_config *conf, mbedtls_dhm_context
 {
     int ret;
 
-    if( ( ret = mbedtls_mpi_copy( &conf->dhm_P, &dhm_ctx->P ) ) != 0 )
-        return( ret );
-
-    if( ( ret = mbedtls_mpi_copy( &conf->dhm_G, &dhm_ctx->G ) ) != 0 )
+    if( ( ret = mbedtls_mpi_copy( &conf->dhm_P, &dhm_ctx->P ) ) != 0 ||
+        ( ret = mbedtls_mpi_copy( &conf->dhm_G, &dhm_ctx->G ) ) != 0 )
+    {
+        mbedtls_mpi_free( &conf->dhm_P );
+        mbedtls_mpi_free( &conf->dhm_G );
         return( ret );
+    }
 
     return( 0 );
 }
@@ -6667,15 +6671,15 @@ int mbedtls_ssl_config_defaults( mbedtls_ssl_config *conf,
     conf->renego_period[7] = 0x00;
 #endif
 
-#if defined(MBEDTLS_DHM_C)
-    if( ( ret = mbedtls_mpi_read_string( &conf->dhm_P, 16,
-                                 MBEDTLS_DHM_RFC5114_MODP_1024_P) ) != 0 ||
-        ( ret = mbedtls_mpi_read_string( &conf->dhm_G, 16,
-                                 MBEDTLS_DHM_RFC5114_MODP_1024_G) ) != 0 )
+#if defined(MBEDTLS_DHM_C) && defined(MBEDTLS_SSL_SRV_C)
+    if( endpoint == MBEDTLS_SSL_IS_SERVER )
     {
-        mbedtls_mpi_free( &conf->dhm_P );
-        mbedtls_mpi_free( &conf->dhm_G );
-        return( ret );
+        if( ( ret = mbedtls_ssl_set_dh_param( conf,
+                        MBEDTLS_DHM_RFC5114_MODP_2048_P,
+                        MBEDTLS_DHM_RFC5114_MODP_2048_G ) ) != 0 )
+        {
+            return( ret );
+        }
     }
 #endif
 
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index 6f6836d9c..17aa9ff9f 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -1727,11 +1727,7 @@ int main( int argc, char *argv[] )
 #if defined(MBEDTLS_FS_IO)
     if( opt.dhm_file != NULL )
         ret = mbedtls_ssl_set_dh_param_ctx( &conf, &dhm );
-    else
 #endif
-        ret = mbedtls_ssl_set_dh_param( &conf, MBEDTLS_DHM_RFC5114_MODP_2048_P,
-                                               MBEDTLS_DHM_RFC5114_MODP_2048_G );
-
     if( ret != 0 )
     {
         mbedtls_printf( "  failed\n  mbedtls_ssl_set_dh_param returned -0x%04X\n\n", - ret );