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From: Jarkko Sakkinen <jarkko@kernel.org>
To: linux-integrity@vger.kernel.org, tpm2@lists.linux.dev
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>
Subject: Re: tpm2key.asn1 parent identification
Date: Sun, 14 Sep 2025 19:23:33 +0300	[thread overview]
Message-ID: <aMbsBX2uq6zOixSA@kernel.org> (raw)
In-Reply-To: <aMboFXNNX7WZaOaS@kernel.org>

On Sun, Sep 14, 2025 at 07:08:37PM +0300, Jarkko Sakkinen wrote:
> Hi,
> 
> In practice, while implementing tpm2sh and its self-contained TPM emulator
> called "MockTPM", I've noticed that 'tpm2key.asn1.' has a major bottleneck,
> but luckily it is easy to squash.
> 
> Parent handle should never be persisted, as it defies the existential
> reason of having a file format in the first place.
> 
> To address this issue I just added couple of optional fields to TPMKey:
> 
>   parentName   [6] EXPLICIT OCTET STRING OPTIONAL,
>   parentPubkey [7] EXPLICIT OCTET STRING OPTIONAL
> 
> By persisting this information TPM2_GetCapability + TPM2_ReadPublic can
> be used to acquire an appropriate handle.
> 
> I'd highly recommend to add this quirk to anything that processes this
> ASN.1 format.


Here's a proof of concept:

https://github.com/puavo-org/tpm2sh/commit/18ec3c2169b23523d8866c58fa7b8a89a79bd3d4

BR, Jarkko

  reply	other threads:[~2025-09-14 16:23 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-09-14 16:08 tpm2key.asn1 parent identification Jarkko Sakkinen
2025-09-14 16:23 ` Jarkko Sakkinen [this message]
2025-09-22 21:42   ` James Bottomley
2025-09-15  3:24 ` James Bottomley
2025-09-15 14:50   ` Jarkko Sakkinen
2025-09-15 18:08     ` Jarkko Sakkinen
2025-09-16  2:10       ` Jarkko Sakkinen
2025-09-16  2:19         ` Jarkko Sakkinen
2025-09-17  2:33       ` James Bottomley
2025-09-18 15:48         ` Jarkko Sakkinen
2025-09-18 17:35           ` Jarkko Sakkinen
2025-09-22  8:56             ` Jarkko Sakkinen
2025-09-22 21:31               ` James Bottomley
2025-09-23 14:25                 ` Jarkko Sakkinen
2025-09-23 14:37                   ` James Bottomley
2025-09-23 15:08                     ` Jarkko Sakkinen

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