Siemens: Can I access a locked PLC with an unlocked program?

harryting said:

You provided no info on the type of PLC, even if you did, this is really a legal question which none of us can really answer for you.

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i have been neck-deep in a "battle" with a foreign oem trying to get access to the plcs in all our equipment which they have locked down so that they are the only ones who can diagnose it. What do i mean by "locked down"? Every single fb and db in the plc(s) is password protected. I cannot upload, download, or view them in any way that i'm aware of. I was not even able to view the hw config iirc.

At first i asked politely for the passwords and they flat-out said "no way" they would give them to me. So i escalated the issue on their end and then my end, and now it's with the owner of the company who is in negotiations with this oem to purchase a few $$m worth of more machinery from them and he basically made the deal contingent upon the release of the passwords for new machinery and existing machinery. So now they are in starts and fits of being begrudgingly "cooperative," or some approximation thereof. Giving only one breadcrumb at a time, i think to stall the issue, kick the can along, and hopefully make the sale before full cooperation has been reached.

In today's episode they have sent me a bunch of plc programs (not all of them, not even close), which i am able to open without a password, and actually see some of the logic. Keyword some. It would seem they have unlocked a handful of inconsequential dbs for me to pacify myself with while the meat of the program remains locked. So one of the coming battles will be getting those others unlocked as well, but before we get there i want to know, does this even help me?

I tried going online with one of the programs they provided and view of the b.s. Fbs they unlocked in online mode, and i'm still prompted for a password which they still refuse to hand over. Am i doing something wrong? Should i be able to view a locked fb online if i have the unlocked version of the fb in my laptop? Is there some action i need to take in order to be able for this to work? I feel like i'm being bamboozled (again) and i am preparing to launch another volley of emails as if that were fact, but i want to make sure i'm not being an idiot first.

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mk42 said:

1) The PLC might have a password, in addition to the code. PLC password prevents access to the PLC. DIfferent PLCs have differnt numbers of password levels, but at the least could prevent reading (going online) or writing (downloading to PLC)


2) I've never tried it, but I would expect to have to download the unlocked block before you could view it online. I think with/without password would cause the online/offline to not match, and therefore you couldn't monitor.



In the older software versions, there is literally a flag set in the code that makes it so the software won't connect. In the newer software, it can be encrypted, which I'm sure provides additional hurdles.

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parky said:

As the later versions of IDE's & PLC's there seems to be more security options.
Some manufacturers have many different ways of password protection. originally source code was not so very often not supplied by the OEM, however now there are ways to lock the source code i.e. protect blocks so they cannot be viewed, or protected so that they cannot be edited. This allowed OEM's to supply source code either for monitoring (fault finding) or allow download in situations if the PLC lost the program. Also password protection on the PLC can be in various forms i.e. totally locked (No download or monitor), locked so that on-line monitoring is allowed but program changes or download is protected.
Password protection on PLC's to be honest is a thorn in the side of many engineers who are expected to maintain plant at their premises.
I have worked as an OEM & for a production facility so know both sides of the story.
I can sort of understand OEM's locking code (sort of), however even though I spent over 20 years doing OEM work I never locked the code or PLC unless it was requested by the user and then supplied documented code & passwords.
The excuse of "Your engineers don't know what they are doing" is a poor excuse as far as I'm concerned, If they $%^&£ it up then that's their fault, then they will call you in to sort it. The other excuse of we spent lots of time developing this code & we don't want anyone else to pinch it also does not wash with me. I have been called to many situations where either the supplier has gone to the wall etc. and in most cases it is just as quick to re-write the code than to try & decode what the programmer has done.
In my time working for a production facility I managed to negotiate with virtually all suppliers copies of the source code & PLC passwords locked or unlocked. In some cases it took a bit of persuasion others were very willing. I even signed agreements not to pass on source code to others.
If we could not get a response from a supplier we would go elsewhere and in some cases just replaced the PLC & re-wrote it.
"My rant for the day"

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