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SubjectRe: [PATCH] KEYS: trusted: fix -Wvarags warning
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On Fri, 2018-10-12 at 07:29 -0500, Denis Kenzior wrote:
> Hi Nick,
>
> > @@ -123,7 +123,7 @@ static int TSS_rawhmac(unsigned char *digest,
> > const unsigned char *key,
> > */
> > static int TSS_authhmac(unsigned char *digest, const unsigned
> > char *key,
> > unsigned int keylen, unsigned char *h1,
> > - unsigned char *h2, unsigned char h3, ...)
> > + unsigned char h2, unsigned char *h3, ...)
> > {
> > unsigned char paramdigest[SHA1_DIGEST_SIZE];
> > struct sdesc *sdesc;
>
> So my concern here is that this actually breaks the natural argument
> order compared to what the specification uses. This in turn
> requires
> one to perform some mental gymnastics and I'm not sure that this is
> such
> a good idea. Refer to
> https://trustedcomputinggroup.org/wp-content/uploads/TPM-Main-Part-3-
> Commands_v1.2_rev116_01032011.pdf
> for details.
>
> Note that H3 is really the 'continueAuthSession' variable which is a
> bool. In the above specification BOOL has a size of 1, and
> TSS_authhmac already assigns a h3 to 'c' which is used for the actual
> hashing.
>
> So can't we simply use 'bool' or uint32 as the type for h3 instead
> of re-ordering everything

The problem is the standard is ambiguious. The only thing that's
guaranteed to work for all time is a char *. If you want to keep the
order, what I'd suggest is inserting a dummy pointer argument which is
always expected to be NULL between the h3 and the varargs.

James

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