Sahil Rihan wrote on 2013-01-31: > Hi list, > > Like a few before me, I'm trying to calculate in software the value of PCR17 > after SENTER. I'm taking the value of the first extend as a given (from > SinitMleData.SinitHash) and am trying to reconstruct the value at the end of > the second extend. > > I took Jonathan McCune's Perl script as a starting point and was able to > reproduce his result (which I'm assuming is for SinitMleData.Version 6, given > his computation of the first PCR17 extend in his Perl script) using a Python > script I wrote. I then modified my script to use the value from > SinitMleData.SinitHash directly, since my understanding is that it contains the > value of PCR17 after the first extend for SinitMleData.Version 8). > > So my computation is now identical to the one in the MLE Developer's Guide. > > SHA-1 ( SinitMleData.SinitHash | SHA-1 ( SinitMleData.BiosAcm.ID | > SinitMleData.MsegValid | SinitMleData.StmHash | > SinitMleData.PolicyControl | SinitMleData.LcpPolicyHash | > (OsSinitData.Capabilities, 0) | SinitMleData.ProcessorSCRTMStatus) ) > > Unfortunately, I'm not able to get to the value for PCR 17 that tboot dumps, > before it performs its own extend to PCR17. > > If anyone has successfully computed PCR 17 or has thoughts on what I might be > doing wrong, I'd appreciate your input.
Please make sure the data length you used for PCR17 value calculation is right: SinitMleData.MsegValid 8bytes SinitMleData.PolicyControl 4bytes (OsSinitData.Capabilities, 0) 4bytes SinitMleData.ProcessorSCRTMStatus 4bytes And (OsSinitData.Capabilities,0) means: if SinitMleData.PolicyControl.bit2 is 1, use value of OsSinitData.Capabilities if SinitMleData.PolicyControl.bit2 is 0, use a 4-byte 0s. Wish those will help. Jimmy
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