From 687c500da335d0082f7e310c3f8b3cabc2d48a6c Mon Sep 17 00:00:00 2001
From: Hanno Becker <hanno.becker@arm.com>
Date: Fri, 29 Jun 2018 09:04:46 +0100
Subject: [PATCH] Return from debugging functions if SSL context is unset

The debugging functions
- mbedtls_debug_print_ret,
- mbedtls_debug_print_buf,
- mbedtls_debug_print_mpi, and
- mbedtls_debug_print_crt
return immediately if the SSL configuration bound to the
passed SSL context is NULL, has no debugging functions
configured, or if the debug threshold is below the debugging
level.
However, they do not check whether the provided SSL context
is not NULL before accessing the SSL configuration bound to it,
therefore leading to a segmentation fault if it is.
In contrast, the debugging function
- mbedtls_debug_print_msg
does check for ssl != NULL before accessing ssl->conf.

This commit unifies the checks by always returning immediately
if ssl == NULL.
---
 library/debug.c | 44 ++++++++++++++++++++++++++++++++++++++------
 1 file changed, 38 insertions(+), 6 deletions(-)

diff --git a/library/debug.c b/library/debug.c
index db3924ac5..30c8c7bb8 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -86,8 +86,13 @@ void mbedtls_debug_print_msg( const mbedtls_ssl_context *ssl, int level,
     char str[DEBUG_BUF_SIZE];
     int ret;
 
-    if( NULL == ssl || NULL == ssl->conf || NULL == ssl->conf->f_dbg || level > debug_threshold )
+    if( NULL == ssl              ||
+        NULL == ssl->conf        ||
+        NULL == ssl->conf->f_dbg ||
+        level > debug_threshold )
+    {
         return;
+    }
 
     va_start( argp, format );
 #if defined(_WIN32)
@@ -121,8 +126,13 @@ void mbedtls_debug_print_ret( const mbedtls_ssl_context *ssl, int level,
 {
     char str[DEBUG_BUF_SIZE];
 
-    if( ssl->conf == NULL || ssl->conf->f_dbg == NULL || level > debug_threshold )
+    if( NULL == ssl              ||
+        NULL == ssl->conf        ||
+        NULL == ssl->conf->f_dbg ||
+        level > debug_threshold )
+    {
         return;
+    }
 
     /*
      * With non-blocking I/O and examples that just retry immediately,
@@ -146,8 +156,13 @@ void mbedtls_debug_print_buf( const mbedtls_ssl_context *ssl, int level,
     char txt[17];
     size_t i, idx = 0;
 
-    if( ssl->conf == NULL || ssl->conf->f_dbg == NULL || level > debug_threshold )
+    if( NULL == ssl              ||
+        NULL == ssl->conf        ||
+        NULL == ssl->conf->f_dbg ||
+        level > debug_threshold )
+    {
         return;
+    }
 
     mbedtls_snprintf( str + idx, sizeof( str ) - idx, "dumping '%s' (%u bytes)\n",
               text, (unsigned int) len );
@@ -199,8 +214,13 @@ void mbedtls_debug_print_ecp( const mbedtls_ssl_context *ssl, int level,
 {
     char str[DEBUG_BUF_SIZE];
 
-    if( ssl->conf == NULL || ssl->conf->f_dbg == NULL || level > debug_threshold )
+    if( NULL == ssl              ||
+        NULL == ssl->conf        ||
+        NULL == ssl->conf->f_dbg ||
+        level > debug_threshold )
+    {
         return;
+    }
 
     mbedtls_snprintf( str, sizeof( str ), "%s(X)", text );
     mbedtls_debug_print_mpi( ssl, level, file, line, str, &X->X );
@@ -219,8 +239,14 @@ void mbedtls_debug_print_mpi( const mbedtls_ssl_context *ssl, int level,
     int j, k, zeros = 1;
     size_t i, n, idx = 0;
 
-    if( ssl->conf == NULL || ssl->conf->f_dbg == NULL || X == NULL || level > debug_threshold )
+    if( NULL == ssl              ||
+        NULL == ssl->conf        ||
+        NULL == ssl->conf->f_dbg ||
+        NULL == X                ||
+        level > debug_threshold )
+    {
         return;
+    }
 
     for( n = X->n - 1; n > 0; n-- )
         if( X->p[n] != 0 )
@@ -345,8 +371,14 @@ void mbedtls_debug_print_crt( const mbedtls_ssl_context *ssl, int level,
     char str[DEBUG_BUF_SIZE];
     int i = 0;
 
-    if( ssl->conf == NULL || ssl->conf->f_dbg == NULL || crt == NULL || level > debug_threshold )
+    if( NULL == ssl              ||
+        NULL == ssl->conf        ||
+        NULL == ssl->conf->f_dbg ||
+        NULL == crt              ||
+        level > debug_threshold )
+    {
         return;
+    }
 
     while( crt != NULL )
     {