nCipher HSM kernel driver submission feedback request

Hi Herbert,

We've been working on getting this driver code upstreamed into drivers/misc since the end of last year but things stalled a bit on our end. However, we are still interested in getting our submission approved and would please like your assistance and feedback on this.

The driver code for the hardware is straightforward and does not contain any cryptographic components as the cryptography is handled within the hardware's secure boundary. We have no plans to use the linux kernel crypto APIs as our customers require compliance to the FIPS 140 standard or the eIDAS regulations.

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The driver code for the hardware is straightforward and does not contain any cryptographic components as the cryptography is handled within the hardware's secure boundary. We have no plans to use the linux kernel crypto APIs as our customers require compliance to the FIPS

140 standard or the eIDAS regulations.

But what I said was, you NEED to use the linux kernel crypto apis as you need to not try to create your own.

Just because this is the way you did it before, does not mean it is the correct thing to do.

So what is wrong if you do use the existing apis? What is preventing you from doing that?

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The driver code for the hardware is straightforward and does not contain any cryptographic components as the cryptography is handled within the hardware's secure boundary. We have no plans to use the linux kernel crypto APIs as our customers require compliance to the FIPS

140 standard or the eIDAS regulations.

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But what I said was, you NEED to use the linux kernel crypto apis as you need to not try to create your own.

Just because this is the way you did it before, does not mean it is the correct thing to do.

So what is wrong if you do use the existing apis? What is preventing you from doing that?

Sorry Greg but I'm not understanding what the issue is. Can you please explain a bit more what you mean with the apis?

Our driver code is just a tube between proprietary code on the host machine and proprietary code on the HSM. We are not trying to create our own linux crypto apis because all the crypto stuff is happening in the existing proprietary code.

Our driver code is just a tube between proprietary code on the host machine and proprietary code on the HSM.

It looks like this is some sort of PCIe HSM device. As far as I know, Linux doesn't have a standardized API for HSM devices (somebody correct me if I'm wrong), and probably that doesn't quite make sense, either, seeing as most HSMs are accessed anyway through userspace "drivers" -- that is, via libusb or over some networking protocol, or something else. Your situation is different in that it uses PCIe, so you need some kernel mediation in order to give access to your userspace components. And, different manufacturers' HSMs expose very different pieces of functionality, and I'm not sure a unified API for them would even make sense.

It looks like this driver exposes some device file, with a few IOCTLs and then support for reading and writing from and to the device. Besides some driver control things, what actually goes into the device -- that is, the protocol one must use to talk to the thing -- isn't actually described by the driver. You're just shuffling bytes in and out with some mediation around that.

Can you confirm to me whether or not the above is accurate?

If so, then I'm not sure this belongs in the purview of the crypto list or has anything much to do with Linux crypto. This is a PCIe driver for some hardware that userspace has to talk to in order to do some stuff with it.

However, there's something else that you wrote that might make people less inclined to merge this:

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Our driver code is just a tube between proprietary code on the host

machine and proprietary code on the HSM.

It sounds like you need the kernel to expose your PCIe device in a way userspace can access, so that you can talk to it using proprietary code. In other words, this is a kernel driver that exists only to support closed source components. I have no idea about "official policy" on this matter, but I could imagine some people howling about it. On the other hand, the driver _is_ doing something, and it seems like your hardware is somewhat complicated to interface with, and who wouldn't want an open source driver for that, even if it's just the low-level kernel/PCIe components?

Anyway, if my suppositions above are indeed correct, I'd encourage you to submit your driver to whoever maintains drivers/misc/ (Greg and Arnd, IIRC), and ignore the fact that your hardware has something to do with cryptography (though little to do with the Linux crypto API's range of responsibilities).

Hi Jason,

Thanks for your reply and helpful summary of the current discussion.

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It looks like this is some sort of PCIe HSM device. As far as I know, Linux doesn't have a standardized API for HSM devices (somebody correct me if I'm wrong), and probably that doesn't quite make sense, either, seeing as most HSMs are accessed anyway through userspace "drivers" -- that is, via libusb or over some networking protocol, or something else. Your situation is different in that it uses PCIe, so you need some kernel mediation in order to give access to your userspace components. And, different manufacturers' HSMs expose very different pieces of functionality, and I'm not sure a unified API for them would even make sense.

Yes, that's correct. There are currently no standardised APIs for HSM devices in Linux and our PCIe device needs the kernel to facilitate operation.

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It looks like this driver exposes some device file, with a few IOCTLs and then support for reading and writing from and to the device. Besides some driver control things, what actually goes into the device -- that is, the protocol one must use to talk to the thing -- isn't actually described by the driver. You're just shuffling bytes in and out with some mediation around that.

Can you confirm to me whether or not the above is accurate?

Yes, this is accurate.

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If so, then I'm not sure this belongs in the purview of the crypto list or has anything much to do with Linux crypto. This is a PCIe driver for some hardware that userspace has to talk to in order to do some stuff with it.

Again, you are correct. Although it is cryptographic hardware, the driver code does not do anything cryptographic. It is just a PCIe driver.

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Again, you are correct. Although it is cryptographic hardware, the driver code does not do anything cryptographic. It is just a PCIe driver.

If this is "just" a PCIe driver, can you use the UIO interface and just talk to your hardware directly from userspace without any kernel driver needed?

What exactly does the kernel driver need to do here?