Conversation
jarkko

Jarkko Sakkinen

I’m planning to iteratively make tpm2sh policy subcommand to compile policy expressions first into eBPF i.e., --mode ebpf option.

We can use this to address bottleneck in trusted keys in kernel: TPMKey ASN.1 provides key blob but not steps how to create policy session that authorizes the key.

Today: TpmKey ASN.1 with auth value and policy digest can be passed but really only auth value (+ PCR selection in TPM2_Create) can be used for authentication.

My vision for policy protected keys is basically:

  1. Key data is passed as TPMKey ASN.1 just like today.
  2. In addition eBPF program for creation policy session is passed when policy digest is used.

It’s perfectly secure given that a malicious eBPF program would end up to a different policy digest than what is associated with the key.

#linux #kernel #tpm

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