From a5f1a208acc3dcb926c28697cf3be316f21ab7e7 Mon Sep 17 00:00:00 2001
From: Anton Perkov <anton.perkov@block.one>
Date: Mon, 28 May 2018 16:19:35 -0400
Subject: [PATCH] don't fall into forever loop in zero byty in json #3500

---
 libraries/fc/src/io/json.cpp | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/libraries/fc/src/io/json.cpp b/libraries/fc/src/io/json.cpp
index 5980cbf732d..281634c3853 100644
--- a/libraries/fc/src/io/json.cpp
+++ b/libraries/fc/src/io/json.cpp
@@ -77,6 +77,9 @@ namespace fc
                 skipped = true;
                 in.get();
                 break;
+             case '\0':
+                FC_THROW_EXCEPTION( eof_exception, "unexpected end of file" );
+                break;
              default:
                 return skipped;
           }
@@ -136,10 +139,11 @@ namespace fc
                   break;
                case '\t':
                case ' ':
-               case '\0':
                case '\n':
                   in.get();
                   return token.str();
+               case '\0':
+                  FC_THROW_EXCEPTION( eof_exception, "unexpected end of file" );
                default:
                 if( isalnum( c ) || c == '_' || c == '-' || c == '.' || c == ':' || c == '/' )
                 {
@@ -263,10 +267,9 @@ namespace fc
 
       try
       {
-        char c;
-        while((c = in.peek()) && !done)
+        while( !done )
         {
-
+          char c = in.peek();
           switch( c )
           {
               case '.':
@@ -285,6 +288,8 @@ namespace fc
               case '9':
                  ss.put( in.get() );
                  break;
+              case '\0':
+                 FC_THROW_EXCEPTION( eof_exception, "unexpected end of file" );
               default:
                  if( isalnum( c ) )
                  {
@@ -387,8 +392,9 @@ namespace fc
    {
       skip_white_space(in);
       variant var;
-      while( signed char c = in.peek() )
+      while( 1 )
       {
+         signed char c = in.peek();
          switch( c )
          {
             case ' ':
@@ -423,7 +429,7 @@ namespace fc
               return token_from_stream( in );
             case 0x04: // ^D end of transmission
             case EOF:
-            case 0:
+            case '\0':
               FC_THROW_EXCEPTION( eof_exception, "unexpected end of file" );
             default:
               FC_THROW_EXCEPTION( parse_error_exception, "Unexpected char '${c}' in \"${s}\"",