Hex Editor & VB6
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From: Jerry West on 19 Feb 2010 13:52 I have a old VB6 exe that is important to a client for continued use. The source code is not available. A hard coded string within the source code needs to be changed, otherwise the exe is no longer of use to them. Is it possible to use a HexEditor to open the exe and change the string and resave the exe? Would this idea be a viable solution? The string is not a constant. It is a hard coded string in the source. I did try opening the file in a Hex editor but only found it showed the strings that were declared as constants --I could not see any strings that were actually in the code itself. Can anybody shed some light on this? Thanks! JW
From: Karl E. Peterson on 19 Feb 2010 14:12 Jerry West wrote: > I have a old VB6 exe that is important to a client for continued use. The > source code is not available. A hard coded string within the source code > needs to be changed, otherwise the exe is no longer of use to them. Is it > possible to use a HexEditor to open the exe and change the string and resave > the exe? As long as you just overwrite it. I imagine it could get very dicey if you tried changing the length of it. Especially if you tried to lengthen it. You could fairly easily shorten it, for most purposes, by filling the end of it with null chars. > Would this idea be a viable solution? I can't see why not. > The string is not a constant. > It is a hard coded string in the source. I did try opening the file in a Hex > editor but only found it showed the strings that were declared as constants > --I could not see any strings that were actually in the code itself. Maybe I don't understand your "in the code" comment, then? Something like this? Private Sub Timer1_Timer() Label1.Caption = Format$(Now, "long time") End Sub I just compiled that, opened the EXE in a hex editor (Cygnus), and had no problem finding the "long time" string. Are you doing a Unicode search? -- ..NET: It's About Trust! http://vfred.mvps.org
From: Karl E. Peterson on 19 Feb 2010 14:16 Karl E. Peterson wrote: > Jerry West wrote: >> I have a old VB6 exe that is important to a client for continued use. The >> source code is not available. A hard coded string within the source code >> needs to be changed, otherwise the exe is no longer of use to them. Is it >> possible to use a HexEditor to open the exe and change the string and >> resave the exe? > > As long as you just overwrite it. I imagine it could get very dicey if you > tried changing the length of it. Especially if you tried to lengthen it. > You could fairly easily shorten it, for most purposes, by filling the end of > it with null chars. Just confirmed this. I changed the text in a MsgBox string, and it worked just fine. I even truncated it by padding it out with 00's. But, when I inserted new bytes, to try extending it, the program blew chunks when starting. So, there ya go. -- ..NET: It's About Trust! http://vfred.mvps.org
From: dpb on 19 Feb 2010 14:17 Jerry West wrote: > I have a old VB6 exe that is important to a client for continued use. > The source code is not available. A hard coded string within the source > code needs to be changed, otherwise the exe is no longer of use to them. > Is it possible to use a HexEditor to open the exe and change the string > and resave the exe? Would this idea be a viable solution? The string is > not a constant. It is a hard coded string in the source. I did try > opening the file in a Hex editor but only found it showed the strings > that were declared as constants --I could not see any strings that were > actually in the code itself. > > Can anybody shed some light on this? The string is embedded in the executable if it is a constant string. It will be unicode though, so a simple ASCII search won't find it easily. But, if you can change it to a usable string in the same length constraints, sure, you can hack on the executable. In olden days, much code was maintained this way for lack of easier tools and/or the high cost of rebuilding that is a way long forgotten (thankfully)... Just be careful to have backups before you start. --
From: DanS on 19 Feb 2010 14:31
"Jerry West" <jw(a)comcast.net> wrote in news:_cWdne91_6KZQ-PWnZ2dnUVZ_h2dnZ2d(a)giganews.com: > I have a old VB6 exe that is important to a client for continued use. > The source code is not available. A hard coded string within the > source code needs to be changed, otherwise the exe is no longer of use > to them. Is it possible to use a HexEditor to open the exe and change > the string and resave the exe? Would this idea be a viable solution? > The string is not a constant. It is a hard coded string in the source. > I did try opening the file in a Hex editor but only found it showed > the strings that were declared as constants --I could not see any > strings that were actually in the code itself. I've not had to do any replacements like this on a VB6 app. Caveat.....the new string needs to be the same length as the original string. If it's shorter, you can pad it with spaces at the end (if that's not going to affect 'something'). But you can;t put a longer string in there. Are strings stored in Unicode in a VB app ? I think so, so search for the strings characters with zero's too...... "test" = &h74 &h65 &h73 &h74 Unicode "test" = &h74 &h0 &h65 &h0 &h73 &h0 &h74 &h0 I don't think VB is big-endian (but I may be corrected). |