// returns PCR values after TPM Reset.
// NOTE: PCR_Reset() comamnd always resets PCR contents to zeroes.
// TODO: use TPM PCR properties
public static TpmHash GetPcrResetValue(TpmAlgId hashAlg, int pcrNum)
{
return(pcrNum >= 17 && pcrNum <= 22 ? TpmHash.AllOnesHash(hashAlg)
: TpmHash.ZeroHash(hashAlg));
}
/// <summary>
/// This sample demonstrates the use of the TPM Platform Configuration
/// Registers (PCR). TSS.Net provides several features to model PCR
/// semantics.
/// </summary>
/// <param name="tpm">Reference to the TPM object.</param>
static void Pcrs(Tpm2 tpm)
{
Console.WriteLine("\nPCR sample started.");
//
// Read the value of the SHA1 PCR 1 and 2
//
var valuesToRead = new PcrSelection[]
{
new PcrSelection(TpmAlgId.Sha256, new uint[] { 1, 2 })
};
PcrSelection[] valsRead;
Tpm2bDigest[] values;
tpm.PcrRead(valuesToRead, out valsRead, out values);
//
// Check that what we read is what we asked for (the TPM does not
// guarantee this)
//
if (valsRead[0] != valuesToRead[0])
{
Console.WriteLine("Unexpected PCR-set");
}
//
// Print out PCR-1
//
var pcr1 = new TpmHash(TpmAlgId.Sha256, values[0].buffer);
Console.WriteLine("PCR1: " + pcr1);
//
// Extend (event) PCR[1] in the TPM and in the external library and
// see if they match
//
var dataToExtend = new byte[] { 0, 1, 2, 3, 4 };
//
// Note that most PCR must be authorized with "null" authorization
//
tpm.PcrEvent(TpmHandle.Pcr(1), dataToExtend);
//
// And read the current value
//
tpm.PcrRead(valuesToRead, out valsRead, out values);
//
// Update the "simulated" PCR
//
pcr1.Event(dataToExtend);
//
// And see whether the PCR has the value we expect
//
if (pcr1 != values[0].buffer)
{
throw new Exception("Event did not work");
}
//
// Update a resettable PCR
//
tpm.PcrEvent(TpmHandle.Pcr(16), new byte[] { 1, 2 });
//
// And reset it
//
tpm.PcrReset(TpmHandle.Pcr(16));
//
// And check that it is indeed zero
//
tpm.PcrRead(new PcrSelection[] {
new PcrSelection(TpmAlgId.Sha256, new uint[] { 16 })
},
out valsRead,
out values);
//
// Did it reset?
//
if (TpmHash.ZeroHash(TpmAlgId.Sha256) != values[0].buffer)
{
throw new Exception("PCR did not reset");
}
Console.WriteLine("PCR sample finished.");
} // Pcrs