Fix bug in ssl_write_supported_elliptic_curves_extarchive/iotssl-580-invalid-curves-crash-1.3

Passing invalid curves to mbedtls_ssl_conf_curves caused a crash later
in ssl_write_supported_elliptic_curves_ext. #373

2 files changed, 8 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index f3e6d1d..20d623a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -7,6 +7,8 @@ Bugfix
      arguments where the same (in-place doubling). Found and fixed by Janos
      Follath. #309
    * Fix issue in Makefile that prevented building using armar. #386
+   * Fix issue that caused a crash if invalid curves were passed to
+     mbedtls_ssl_conf_curves. #373
 
 Changes
    * On ARM platforms, when compiling with -O0 with GCC, Clang or armcc5,
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index b1cd7cb..e1cebbf 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -330,6 +330,12 @@ static void ssl_write_supported_elliptic_curves_ext( ssl_context *ssl,
     for( info = ecp_curve_list(); info->grp_id != POLARSSL_ECP_DP_NONE; info++ )
     {
 #endif
+        if( info == NULL )
+        {
+            SSL_DEBUG_MSG( 1, ( "invalid curve in ssl configuration" ) );
+            return;
+        }
+
         elliptic_curve_len += 2;
     }