Re: [edk2-devel] [PATCH V3 3/9] OvmfPkg/IntelTdx: Add SecTdxHelperLib

["Min Xu" <min.m.xu@intel.com>]

Ah, yes. We can call Sha384HashAll(). Thanks for reminder!

> -----Original Message-----
> From: Yao, Jiewen <jiewen.yao@intel.com>
> Sent: Thursday, January 26, 2023 10:02 AM
> To: Xu, Min M <min.m.xu@intel.com>; devel@edk2.groups.io;
> kraxel@redhat.com
> Cc: Aktas, Erdem <erdemaktas@google.com>; James Bottomley
> <jejb@linux.ibm.com>; Tom Lendacky <thomas.lendacky@amd.com>;
> Michael Roth <michael.roth@amd.com>
> Subject: RE: [edk2-devel] [PATCH V3 3/9] OvmfPkg/IntelTdx: Add
> SecTdxHelperLib
> 
> Hey
> I don't think it is a good idea to define a context size here, because that will
> assume the openssl implementation. Please don't do that.
> 
> Could you please just use Sha384HashAll() API, if you don't like to allocate
> memory?
> 
> Thank you
> Yao, Jiewen
> 
> > -----Original Message-----
> > From: Xu, Min M <min.m.xu@intel.com>
> > Sent: Thursday, January 26, 2023 9:57 AM
> > To: devel@edk2.groups.io; kraxel@redhat.com
> > Cc: Aktas, Erdem <erdemaktas@google.com>; James Bottomley
> > <jejb@linux.ibm.com>; Yao, Jiewen <jiewen.yao@intel.com>; Tom
> Lendacky
> > <thomas.lendacky@amd.com>; Michael Roth <michael.roth@amd.com>
> > Subject: RE: [edk2-devel] [PATCH V3 3/9] OvmfPkg/IntelTdx: Add
> > SecTdxHelperLib
> >
> > On January 25, 2023 8:16 PM, Gerd Hoffmann wrote:
> > > > +//
> > > > +// SHA512_CTX is defined in <openssl/sha.h> and its size is 216 bytes.
> > > > +// It can be built successfully with GCC5 compiler but failed with
> VS2019.
> > > > +// The error code showed in VS2019 is that "openssl/sha.h" cannot
> > > > +be
> > found.
> > > > +// To overcome this error SHA512_CTX_SIZE is defined.
> > > > +//
> > > > +#define SHA512_CTX_SIZ  216
> > >
> > > There is Sha384GetContextSize()
> > >
> > HashAndExtendToRtmr is designed to be run in very early stage and at
> > that stage Memory allocation service is not ready. So we have to
> > declare an array with size of SHA512_CTX_SIZE(216).
> >
> > Variable-length automatic arrays are allowed in C99.
> > https://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html So if ovmf is
> > built with GCC, then the code below works:
> >   UINT8       Sha384Ctx[Sha384GetContextSize ()];
> >
> > But unfortunately it is not supported in VS series. (I test it with
> > VS2017) Building ...
> >
> tdvf2\EmbeddedPkg\Library\PrePiMemoryAllocationLib\PrePiMemoryAllocat
> i
> > on
> > Lib.inf [X64]
> > tdvf2\OvmfPkg\IntelTdx\TdxHelperLib\SecTdxHelper.c(839): error C2057:
> > expected constant expression
> > tdvf2\OvmfPkg\IntelTdx\TdxHelperLib\SecTdxHelper.c(839): error C2466:
> > cannot allocate an array of constant size 0
> > tdvf2\OvmfPkg\IntelTdx\TdxHelperLib\SecTdxHelper.c(839): error C2133:
> > 'Sha384Ctx': unknown size
> >
> > So Sha384GetContextSize() cannot be used here.
> >
> > Thanks
> > Min