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