/********************************************************************************/ /* */ /* Context Management Command Support */ /* Written by Ken Goldman */ /* IBM Thomas J. Watson Research Center */ /* $Id: Context_spt.c 1603 2020-04-03 17:48:43Z kgoldman $ */ /* */ /* Licenses and Notices */ /* */ /* 1. 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Is null for // everything but a primary object in // the Endorsement Hierarchy BYTE kdfResult[sizeof(TPMU_HA) * 2];// Value produced by the KDF TPM2B_DATA sequence2B, handle2B; // Get proof value proof = HierarchyGetProof(contextBlob->hierarchy); // Get sequence value in 2B format sequence2B.t.size = sizeof(contextBlob->sequence); cAssert(sequence2B.t.size <= sizeof(sequence2B.t.buffer)); MemoryCopy(sequence2B.t.buffer, &contextBlob->sequence, sequence2B.t.size); // Get handle value in 2B format handle2B.t.size = sizeof(contextBlob->savedHandle); cAssert(handle2B.t.size <= sizeof(handle2B.t.buffer)); MemoryCopy(handle2B.t.buffer, &contextBlob->savedHandle, handle2B.t.size); // Get the symmetric encryption key size symKey->t.size = CONTEXT_ENCRYPT_KEY_BYTES; symKeyBits = CONTEXT_ENCRYPT_KEY_BITS; // Get the size of the IV for the algorithm iv->t.size = CryptGetSymmetricBlockSize(CONTEXT_ENCRYPT_ALG, symKeyBits); // KDFa to generate symmetric key and IV value CryptKDFa(CONTEXT_INTEGRITY_HASH_ALG, &proof->b, CONTEXT_KEY, &sequence2B.b, &handle2B.b, (symKey->t.size + iv->t.size) * 8, kdfResult, NULL, FALSE); // Copy part of the returned value as the key pAssert(symKey->t.size <= sizeof(symKey->t.buffer)); MemoryCopy(symKey->t.buffer, kdfResult, symKey->t.size); // Copy the rest as the IV pAssert(iv->t.size <= sizeof(iv->t.buffer)); MemoryCopy(iv->t.buffer, &kdfResult[symKey->t.size], iv->t.size); return; } /* 7.3.2.2 ComputeContextIntegrity() */ /* Generate the integrity hash for a context It is used by TPM2_ContextSave() to create an integrity hash and by TPM2_ContextLoad() to compare an integrity hash */ void ComputeContextIntegrity( TPMS_CONTEXT *contextBlob, // IN: context blob TPM2B_DIGEST *integrity // OUT: integrity ) { HMAC_STATE hmacState; TPM2B_PROOF *proof; UINT16 integritySize; // Get proof value proof = HierarchyGetProof(contextBlob->hierarchy); // Start HMAC integrity->t.size = CryptHmacStart2B(&hmacState, CONTEXT_INTEGRITY_HASH_ALG, &proof->b); // Compute integrity size at the beginning of context blob integritySize = sizeof(integrity->t.size) + integrity->t.size; // Adding total reset counter so that the context cannot be // used after a TPM Reset CryptDigestUpdateInt(&hmacState.hashState, sizeof(gp.totalResetCount), gp.totalResetCount); // If this is a ST_CLEAR object, add the clear count // so that this contest cannot be loaded after a TPM Restart if(contextBlob->savedHandle == 0x80000002) CryptDigestUpdateInt(&hmacState.hashState, sizeof(gr.clearCount), gr.clearCount); // Adding sequence number to the HMAC to make sure that it doesn't // get changed CryptDigestUpdateInt(&hmacState.hashState, sizeof(contextBlob->sequence), contextBlob->sequence); // Protect the handle CryptDigestUpdateInt(&hmacState.hashState, sizeof(contextBlob->savedHandle), contextBlob->savedHandle); // Adding sensitive contextData, skip the leading integrity area CryptDigestUpdate(&hmacState.hashState, contextBlob->contextBlob.t.size - integritySize, contextBlob->contextBlob.t.buffer + integritySize); // Complete HMAC CryptHmacEnd2B(&hmacState, &integrity->b); return; } #if 0 /* 7.3.2.3 SequenceDataExport() */ /* This function is used scan through the sequence object and either modify the hash state data for export (contextSave) or to import it into the internal format (contextLoad). This function should only be called after the sequence object has been copied to the context buffer (contextSave) or from the context buffer into the sequence object. The presumption is that the context buffer version of the data is the same size as the internal representation so nothing outsize of the hash context area gets modified. */ void SequenceDataExport( HASH_OBJECT *object, // IN: an internal hash object HASH_OBJECT_BUFFER *exportObject // OUT: a sequence context in a buffer ) { // If the hash object is not an event, then only one hash context is needed int count = (object->attributes.eventSeq) ? HASH_COUNT : 1; for(count--; count >= 0; count--) { HASH_STATE *hash = &object->state.hashState[count]; size_t offset = (BYTE *)hash - (BYTE *)object; BYTE *exportHash = &((BYTE *)exportObject)[offset]; CryptHashExportState(hash, (EXPORT_HASH_STATE *)exportHash); } } /* 7.3.2.4 SequenceDataImport() */ /* This function is used scan through the sequence object and either modify the hash state data for export (contextSave) or to import it into the internal format (contextLoad). This function should only be called after the sequence object has been copied to the context buffer (contextSave) or from the context buffer into the sequence object. The presumption is that the context buffer version of the data is the same size as the internal representation so nothing outsize of the hash context area gets modified. */ void SequenceDataImport( HASH_OBJECT *object, // IN/OUT: an internal hash object HASH_OBJECT_BUFFER *exportObject // IN/OUT: a sequence context in a buffer ) { // If the hash object is not an event, then only one hash context is needed int count = (object->attributes.eventSeq) ? HASH_COUNT : 1; for(count--; count >= 0; count--) { HASH_STATE *hash = &object->state.hashState[count]; size_t offset = (BYTE *)hash - (BYTE *)object; BYTE *importHash = &((BYTE *)exportObject)[offset]; // CryptHashImportState(hash, (EXPORT_HASH_STATE *)importHash); } } #endif