related tdf#73691 - prevent AltX creating control characters

Do nothing for numbers 0x00 - 0x1f.

Change-Id: Idda596e735c464b97dc3624253ebbea86933ff2c
Reviewed-on: https://gerrit.libreoffice.org/19654Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>

i18nutil/source/utility/unicode.cxx

@@ -1084,6 +1084,13 @@ bool ToggleUnicodeCodepoint::AllowMoreInput(sal_Unicode uChar)
                 return false;
             }
 
+            // 0 - 1f are control characters.  Do not process those.
+            if( uChar < 0x20 )
+            {
+                mbAllowMoreChars = false;
+                return false;
+            }
+
             switch( uChar )
             {
                 case 'u':
@@ -1117,9 +1124,6 @@ bool ToggleUnicodeCodepoint::AllowMoreInput(sal_Unicode uChar)
                             maInput.insertUtf32(0, uChar);
                     }
                     break;
-                case 0:
-                    mbAllowMoreChars = false;
-                    break;
                 default:
                     // + already found. Since not U, cancel further input
                     if( mbRequiresU )
@@ -1185,15 +1189,15 @@ OUString ToggleUnicodeCodepoint::StringToReplace()
     while( nUPlus != -1 )
     {
         nUnicode = sIn.copy(0, nUPlus).toString().toUInt32(16);
-        //strip out all null or invalid Unicode values
-        if( !nUnicode || nUnicode > 0x10ffff )
+        //prevent creating control characters or invalid Unicode values
+        if( nUnicode < 0x20 || nUnicode > 0x10ffff )
             maInput = sIn.copy(nUPlus);
         sIn = sIn.copy(nUPlus+2);
         nUPlus =  sIn.indexOf("U+");
     }
 
     nUnicode = sIn.toString().toUInt32(16);
-    if( !nUnicode || nUnicode > 0x10ffff )
+    if( nUnicode < 0x20 || nUnicode > 0x10ffff )
        maInput.truncate().append( sIn[sIn.getLength()-1] );
     return maInput.toString();
 }