Add ECC AIK template and cache; Work around for CertifyCreation

[jkl73]

Certain TPM (the one on my Lenovo X1 carbon) cannot handle CeritfyCreation with a null signing handle correctly. It will throw a TPM_RC_INSUFFICIENT error when we trying to do that.

One work around is that we pass in a non-null signing handle into CertifyCreation.
This PR implement this work around as well as add a ECC AIK template.

AIK ECC key will be cached for performance concerns.
I picked the handle 0x81008FFF (I picked randomly from "Storage -> Available" from Table 11 from https://trustedcomputinggroup.org/wp-content/uploads/RegistryOfReservedTPM2HandlesAndLocalities_v1p1_pub.pdf

[josephlr]

For the most part this looks good, just some comment nits.

[josephlr]

Looks good, just fix the formatting/structure comments, and then submit.

[savely-krasovsky]

@jkl73 I understand that this is PR is from 2020, but I catch this issue even with your patch on Lenovo X1 Yoga 3rd Gen (Windows 10). Still getting TPM_RC_INSUFFICENT error: failed to certify creation: handle 0, error code 0x1a : the TPM was unable to unmarshal a value because there were not enough octets in the input buffer. I am trying to use it without admit rights if that important.

I am not a TPM expert, but I observe that I cannot get ECC SRK without administrative rights, probably because after reboot Windows initializes only RSA one by default. Maybe it's connected, because this patch tries to use ECC cached key.

[jkl73]

@jkl73 I understand that this is PR is from 2020, but I catch this issue even with your patch on Lenovo X1 Yoga 3rd Gen (Windows 10). Still getting TPM_RC_INSUFFICENT error: failed to certify creation: handle 0, error code 0x1a : the TPM was unable to unmarshal a value because there were not enough octets in the input buffer. I am trying to use it without admit rights if that important.

I'm not familiar with how admin rights affecting TPM on windows, does it work with admin rights?

I am not a TPM expert, but I observe that I cannot get ECC SRK without administrative rights, probably because after reboot Windows initializes only RSA one by default. Maybe it's connected, because this patch tries to use ECC cached key.

Also maybe your TPM doesn't support the default AIKTemplateECC parameter (CurveNISTP256)? Or maybe you can try to use the RSA SRK to do the workaround.

[savely-krasovsky]

I'm not familiar with how admin rights affecting TPM on windows, does it work with admin rights?

Basically Windows doesn't allow you to get ECC SRK without admin rights for some reason. But after getting it for the first time (for example by spawning one-shot Windows service which just calling client.StorageRootKeyECC()), it will be available for other users without requiring admin rights, weird.

I didn't try with admin rights with production-ready piece of software because it does not meant to run under admin.

Also maybe your TPM doesn't support the default AIKTemplateECC parameter (CurveNISTP256)?

Probably, but it successfully passing those lines:

signer, err := AttestationKeyECC(k.rw)
if err != nil {
	return nil, fmt.Errorf("failed to create fallback signing key: %w", err)
}

Otherwise it would return error here, isn't it?

Or maybe you can try to use the RSA SRK to do the workaround.

We are already using RSA SRK and for the majority of users it works flawlessly, sealing, unsealing, etc. But during testing getting error at unsealing stage with this Lenovo Yoga.

Does it worth a try to change this line from: signer, err := AttestationKeyECC(k.rw) to signer, err := AttestationKeyRSA(k.rw)?

[jkl73]

I'm not familiar with how admin rights affecting TPM on windows, does it work with admin rights?

Basically Windows doesn't allow you to get ECC SRK without admin rights for some reason. But after getting it for the first time (for example by spawning one-shot Windows service which just calling client.StorageRootKeyECC()), it will be available for other users without requiring admin rights, weird.

I didn't try with admin rights with production-ready piece of software because it does not meant to run under admin.

Also maybe your TPM doesn't support the default AIKTemplateECC parameter (CurveNISTP256)?

Probably, but it successfully passing those lines:

signer, err := AttestationKeyECC(k.rw)
if err != nil {
	return nil, fmt.Errorf("failed to create fallback signing key: %w", err)
}

Otherwise it would return error here, isn't it?

Or maybe you can try to use the RSA SRK to do the workaround.

We are already using RSA SRK and for the majority of users it works flawlessly, sealing, unsealing, etc. But during testing getting error at unsealing stage with this Lenovo Yoga.

Does it worth a try to change this line from: signer, err := AttestationKeyECC(k.rw) to signer, err := AttestationKeyRSA(k.rw)?

Yes, I think it's worth to try, at least it should reveal if the problem is related to the ecc algo or not.