linux-kernel - Re: [PATCH] KEYS: trusted: fix -Wvarags warning

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Message-ID: <f83893d2-ed9b-613f-2768-1a975d28fe8b@gmail.com>
Date:   Fri, 12 Oct 2018 07:29:53 -0500
From:   Denis Kenzior <denkenz@...il.com>
To:     ndesaulniers@...gle.com, jejb@...ux.vnet.ibm.com,
        dhowells@...hat.com
Cc:     natechancellor@...il.com, ebiggers@...gle.com,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KEYS: trusted: fix -Wvarags warning

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?

Regards,
-Denis