From: Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
To: Ken Goldman <kgold-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Cc: tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Subject: Re: TPM2 resource manager context save
Date: Tue, 13 Jun 2017 23:17:51 +0300 [thread overview]
Message-ID: <20170613201751.exrwn4nfizbvw7ng@intel.com> (raw)
In-Reply-To: <9679ee72-15db-0f20-2610-60672868bba1-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Hi
I'm sorry for such a long delay!
On Fri, Jun 09, 2017 at 10:29:24AM -0400, Ken Goldman wrote:
> At least a question, maybe a bug ...
>
> What is the expected behavior for the resource manager when it receives
> contextsave for a transient object?
> ]
> ~~
>
> Use case:
>
> Creating an RSA primary key can take a long time. I've seen it take 90
> seconds. The SRK will probably be made persistent. However, there are a
> limited number of persistent object slots. So the less frequently used EK
> will likely be created on demand.
>
> To improve performance, an application can context save the EK, and then
> context load it when needed. This is a symmetric key operation, and is much
> faster. This can work even for a new connection.
>
> ~~
>
> When I try the command, write() returns 22, EINVAL
>
> The RM seems to have some special handling for context save in
> tpm2_cmd.c:tpm2_get_cc_attrs_tbl(). Later, the write() returns EINVAL (22),
It's done so that we do not need a special for it: treat it like it was
part of the handle area.
> probably because tpm2_map_command() does not find TPM2_CC_CONTEXT_SAVE in
> the attribute table.
>
> ~~
>
> Question: Is this expected? Is it the desired design?
Nope but should never happen if there was TPMA_CC for ContextSave.
> Bug: IMHO, EINVAL is a poor choice, as the application thinks the write()
> failed. In fact, the TPM write() didn't even occur. Better would be to
> construct the standard TPM response to an unimplemented command:
> TPM_RC_COMMAND_CODE. This tells the application more accurately what failed
> - the command code is not permitted.
Not sure about this.
/Jarkko
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prev parent reply other threads:[~2017-06-13 20:17 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-09 14:29 TPM2 resource manager context save Ken Goldman
[not found] ` <9679ee72-15db-0f20-2610-60672868bba1-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-06-13 20:17 ` Jarkko Sakkinen [this message]
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