RE: [Dev-C++] Help with application security (hiding strings in compiled binaries)

[Ed C. <em...@ed...>]

P.D., Pete, etc -

Thanks for the suggestions. I'll probably go with the XOR method or some
other bit manipulation. (The man-in-the-middle is not a problem - I
personally control most of the servers involved and have them locked =
down
awfully tight; it's the app that is the weak link).=20

Anyway, thanks for the help.

-Ed

-----Original Message-----
From: P.D. van Zelst [mailto:pa...@my...]=20
Sent: Saturday, August 16, 2003 8:25 PM
To: 'Ed Cottrell'; dev...@li...
Subject: RE: [Dev-C++] Help with application security (hiding strings in
compiled binaries)


Yeah, you're right... I only checked the executable for the string =
literal
(in either ASCII or Unicode) using a hex editor, didn't spend much time
checking for any other patterns. Another option would be to use (or =
write) a
string encoding program, which emits a (reversible) string that you then =
use
as a literal in your application. Then when you need the plain-text =
string,
you decode it using some decoding function (could be anything simple, =
bit
inversion would even suffice). I know it's a bit more work, but it will
effectively get rid of your problem. Doesn't get rid of the plain-text
string existing in memory at some point, but that's not your problem as =
far
as I understood.

I'll send along a simple example of what I mean. This is just some =
really
basic 'encoding', and not quite safe in any way.. using bit inversion...
simplest I could think of to effectively garble text (have no idea if =
it'd
work correctly at all, this is off the top of my head).

[for encoding your strings for use in your application, don't think =
you'd
want to do that by hand :P]:

#include <iostream>
using std::cout;
using std::endl;

int main(int argc, char* argv[])
{
	if (argc !=3D 2)
		return 1;
=09
	for (int i =3D 0; i < strlen(argv[1]); ++i)
		cout << ~argv[1][i];
	cout << endl;
}


[decoding function for use in your application]

#include <iostream>
using std::cout;
using std::endl;

void decodepass(char* pDest, const char* pSrc, int iLen)
{
	if (!pDest || !pSrc)
		return;
=09
	for (int i =3D 0; i < iLen; ++i)
		pDest[i] =3D ~pSrc[i];
	pDest[i] =3D '\0';
}

int main()
{
	const char* pszSomePass =3D "<some encoded string>";
	char szDecoded[256];
=09
	decodepass(szDecoded, pszSomePass);
	cout << "My decoded string is: " << szDecoded << endl;
=09
	return 0;
}


-----Original Message-----
From: dev...@li...
[mailto:dev...@li...] On Behalf Of Ed =
Cottrell
Sent: Sunday, August 17, 2003 1:22 AM
To: dev...@li...
Subject: RE: [Dev-C++] Help with application security (hiding strings in
compiled binaries)


Hi -

That's certainly an improvement. However, it still shows up somewhat
predictably. It looks like this in a text editor (I doubt this will =
display
correctly):

  =
=FA=FF=FFj=C6=85=A9=FA=FF=FFi=C6=85=AA=FA=FF=FFl=C6=85=AB=FA=FF=FFl=C6=85=
=AC=FA=FF=FF =C6=85
     ^      ^      ^      ^      ^

It's a little weird, but you can see the pretty regular repetition, =
there.
It MIGHT be sufficient to my purposes to do it this way, but it's not
ideal...

Other ideas?

-Ed


-----Original Message-----
From: dev...@li...
[mailto:dev...@li...] On Behalf Of P.D. van
Zelst
Sent: Saturday, August 16, 2003 6:45 PM
To: 'Ed Cottrell'; 'Michael D. Smith'; =
dev...@li...
Subject: RE: [Dev-C++] Help with application security (hiding strings in
compiled binaries)


Well, it appears that if you specify your passwords as separate =
characters
in a character array, it won't turn up in the executable as a string
literal. I just tested this, as I was curious myself... The following =
code
will generate an executable with the string literal "jack" in it, but =
"jill"
won't show up as a literal (at least, not on my compiler... GCC 3.2 =
[Dev-C++
4.9.8.2]):

#include <iostream>
using std::cout;
using std::endl;


int main()
{
	char szUser[] =3D "jack";
	char szPass[] =3D { 'j', 'i', 'l', 'l', '\0'};
	cout << szUser << endl;
	cout << szPass << endl;
	return 0;
}


Hope this helps you somewhat,


Paul

-----Original Message-----
From: dev...@li...
[mailto:dev...@li...] On Behalf Of Ed =
Cottrell
Sent: Sunday, August 17, 2003 12:02 AM
To: 'Michael D. Smith'; dev...@li...
Subject: RE: [Dev-C++] Help with application security (hiding strings in
compiled binaries)


Hi Mike & others,

I know I can't make it impossible to find, but I'd like it to be more
difficult than it is. The user logging in to the database will have =
limited
capabilities, of course, but one (the trickiest to secure) is SELECT
capability, by necessity...

I'm not sure how I could separate the logon program from the main =
program
(and put it in a secured directory) without losing functionality; the =
end
user HAS to be able to login to the database servers from the program
itself, but without having access other than through the program's own
controls. In other words, when he/she runs my app, he/she should then =
have
limited access to the database, but without knowing the authentication =
used
to get there. If the user is going to somehow invoke a separate login
program, that requires yet another layer of security, right? The user =
will
be accessing some of the data over the net, and I don't want just =
anybody to
run a login script... (NOTE: traffic sniffing isn't a concern with this =
data
- no credit cards or anything; somebody logging in and getting lots at =
once,
though, is).

NOTE: I don't mind encrypting it, somehow; I'm just not thrilled about =
it,
because it would result in definite penalties in file size, execution =
speed,
and development time.

How else can I make this more discrete?

-Ed

-----Original Message-----
From: Michael D. Smith [mailto:for...@hi...]=20
Sent: Friday, August 15, 2003 10:14 PM
To: Ed Cottrell
Subject: Re: [Dev-C++] Help with application security (hiding strings in
compiled binaries)



I've done a good bit of computer security work over the years, I first=20
programmed a UNIVAC 9200 in 1969, but I'm just now learning C, so from =
that=20
perspective...

The situation is that you can't make it impossible to the truly =
determined.=20
You might could make it take 200 people 3 years though, which is no =
doubt=20
much, much, much better than "anyone" and "notepad"

It depends on the specifics which of course you don't want to give for=20
obvious reasons. The first thing that comes to my mind is you should ask

yourself "why do people logging on have access to the logon program?" If

you could stop that, that alone would go a long way towards making you =
more=20
secure. See if you can't do something with the file/directory =
permissions=20
to make that impossible.

YOu could store it packed (as binary) but anyone can read that as well =
if=20
it's in a known code. I'm not 100% sure but I think putting it in a=20
"struct" does that in C. If not, there's certainly someway to convert =
it.=20
They would have to be a "little"  (very little) more determined to crack =
it=20
but it could still be done. Still it's better than "anyone" and =
"notepad."

Even though you don't like encoding, it certainly could work. There's a=20
world of possibilities out there. Just be aware, a "good" code is going =
to=20
cost you in processing time. Maybe as much as 30 seconds per user. If=20
you're already at, or close to capacity that could be a hit. Of course =
with=20
processing speed doubling every few months "they say" you're not =
supposed=20
to worry about that. Of course with everyone not worrying about that ...
:)

And of course the current hot programming thinking is OOP (object =
oriented=20
programming). For some reason, the way they push OOP these days leaves =
out=20
the fact that it's purpose was/is security. But it too has security =
holes=20
for those in the know. I guess they figure that if you don't know that's

it's purpose, you don't make it your purpose to find the security holes.

You give the users an object that only allows them to use your method=20
(subroutine) to access/change the database or perhaps to logon to start=20
with. Your subroutine of course only does access/changes that you =
approve=20
of. I suspect this would involve rewriting the whole program which, if =
your=20
not interested in encoding, you're probably not interested in rewriting =
the=20
whole thing either. That too very much depends on your program being in =
a=20
directory they don't have permission to access.

By necessity, as I don't know much C, and don't have any specifics, I've

been rather vague but if there's anything else I can do to help (yea=20
right:) -- write anytime.

Good luck.

ms





At 04:10 PM 8/15/03, you wrote:
>Hi,
>
>I have an application that, as one of its primary features, connects to

>numerous databases with semi-sensitive to highly sensitive info in
>them. The end users of this will be employees of a large organization,=20
>and they should not have ANY direct access to the databases,=20
>themselves. So, rather than giving them a username and password, I want

>to hard-code that into the application.
>
>This is currently being done like this (simplified pseudo code):
>
>     char myconnectionstring =3D
> =
"DSN=3Dsomething;server=3Dmyserver;username=3Dmyname;password=3Dmypass";
>     MyConnectionFunction(myconnectionstring);
>
>The compiled file (binary), though, contains this info in plain text.
>I.e., anybody can open it up in Notepad, find the usernames and=20
>passwords, and go hack the databases. That won't work.
>
>So, how can I hide those strings in the compiled code, other than=20
>building in some sort of encryption? Would building the passwords from
individual=20
>characters (ASCII values) work? Other ideas?
>
>Thanks!
>
>-Ed





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