Re: [PATCH 2/6] tpm: add policy sessions

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On Tue, 2024-07-16 at 17:07 +0300, Jarkko Sakkinen wrote:
> On Tue Jul 16, 2024 at 2:53 PM EEST, Jarkko Sakkinen wrote:
> > > -       u8 name[AUTH_MAX_NAMES][2 + SHA512_DIGEST_SIZE];
> > > +       u8 name[AUTH_MAX_NAMES][2 + HASH_MAX_DIGESTSIZE];
> 
> Ouch, we definitely do not want 2-dimensional arrays. I missed this
> in the hmac review.
> 
> Why this is based on count (AUTH_MAX_NAMES) rather than space? Is
> that value from the specs?

Yes, it's based on the maximum number of session handles a command can
have.  It's architecturally defined in Trusted Platform Module Library
Part 1: Architecture chapter 18 (TPM Command/Response Structure) where
it says in 18.1 "an Authorization Area containing one to three session
structures"

Although if I look at our code we really only use a maximum of two for
all the commands the kernel does.

> You could just as well replace name and name_h with a single tpm_buf
> instance in "sized" mode and return -E2BIG from the functions that
> use it. Right, those don't return anything but void, which should be
> also fixed.

I'll look into that: it would get us out of the buf->handles spat.

James





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