/********************************************************************************/
/*										*/
/*		Process the Authorization Sessions     				*/
/*			     Written by Ken Goldman				*/
/*		       IBM Thomas J. Watson Research Center			*/
/*            $Id: SessionProcess.c 1047 2017-07-20 18:27:34Z kgoldman $		*/
/*										*/
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/*  (c) Copyright IBM Corp. and others, 2016, 2017				*/
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/********************************************************************************/

/* 6.4 SessionProcess.c */
/* 6.4.1 Introduction */
/* This file contains the subsystem that process the authorization sessions including implementation
   of the Dictionary Attack logic. ExecCommand() uses ParseSessionBuffer() to process the
   authorization session area of a command and BuildResponseSession() to create the authorization
   session area of a response */
#define SESSION_PROCESS_C
#include "Tpm.h"
/* 6.4.3.1 IsDAExempted() */
/* This function indicates if a handle is exempted from DA logic. A handle is exempted if it is */
/* a) a primary seed handle, */
/* b) an object with noDA bit SET, */
/* c) an NV Index with TPMA_NV_NO_DA bit SET, or */
/* d)	a PCR handle. */
BOOL
IsDAExempted(
	     TPM_HANDLE       handle         // IN: entity handle
	     )
{
    BOOL        result = FALSE;
    //
    switch(HandleGetType(handle))
	{
	  case TPM_HT_PERMANENT:
	    // All permanent handles, other than TPM_RH_LOCKOUT, are exempt from
	    // DA protection.
	    result = (handle != TPM_RH_LOCKOUT);
	    break;
	    // When this function is called, a persistent object will have been loaded
	    // into an object slot and assigned a transient handle.
	  case TPM_HT_TRANSIENT:
	      {
		  TPMA_OBJECT     attributes = ObjectGetPublicAttributes(handle);
		  result = IS_ATTRIBUTE(attributes, TPMA_OBJECT, noDA);
		  break;
	      }
	  case TPM_HT_NV_INDEX:
	      {
		  NV_INDEX            *nvIndex = NvGetIndexInfo(handle, NULL);
		  result = IS_ATTRIBUTE(nvIndex->publicArea.attributes, TPMA_NV, NO_DA);
		  break;
	      }
	  case TPM_HT_PCR:
	    // PCRs are always exempted from DA.
	    result = TRUE;
	    break;
	  default:
	    break;
	}
    return result;
}
/* 6.4.3.2 IncrementLockout() */
/* This function is called after an authorization failure that involves use of an authValue. If the
   entity referenced by the handle is not exempt from DA protection, then the failedTries counter
   will be incremented. */
static TPM_RC
IncrementLockout(
		 UINT32           sessionIndex
		 )
{
    TPM_HANDLE       handle = s_associatedHandles[sessionIndex];
    TPM_HANDLE       sessionHandle = s_sessionHandles[sessionIndex];
    SESSION         *session = NULL;
    //
    // Don't increment lockout unless the handle associated with the session
    // is DA protected or the session is bound to a DA protected entity.
    if(sessionHandle == TPM_RS_PW)
	{
	    if(IsDAExempted(handle))
		return TPM_RC_BAD_AUTH;
	}
    else
	{
	    session = SessionGet(sessionHandle);
	    // If the session is bound to lockout, then use that as the relevant
	    // handle. This means that an authorization failure with a bound session
	    // bound to lockoutAuth will take precedence over any other
	    // lockout check
	    if(session->attributes.isLockoutBound == SET)
		handle = TPM_RH_LOCKOUT;
	    if(session->attributes.isDaBound == CLEAR
	       && (IsDAExempted(handle) || session->attributes.includeAuth == CLEAR))
		// If the handle was changed to TPM_RH_LOCKOUT, this will not return
		// TPM_RC_BAD_AUTH
		return TPM_RC_BAD_AUTH;
	}
    if(handle == TPM_RH_LOCKOUT)
	{
	    pAssert(gp.lockOutAuthEnabled == TRUE);
	    // lockout is no longer enabled
	    gp.lockOutAuthEnabled = FALSE;
	    // For TPM_RH_LOCKOUT, if lockoutRecovery is 0, no need to update NV since
	    // the lockout authorization will be reset at startup.
	    if(gp.lockoutRecovery != 0)
		{
		    if(NV_IS_AVAILABLE)
			// Update NV.
			NV_SYNC_PERSISTENT(lockOutAuthEnabled);
		    else
			// No NV access for now. Put the TPM in pending mode.
			s_DAPendingOnNV = TRUE;
		}
	}
    else
	{
	    if(gp.recoveryTime != 0)
		{
		    gp.failedTries++;
		    if(NV_IS_AVAILABLE)
			// Record changes to NV. NvWrite will SET g_updateNV
			NV_SYNC_PERSISTENT(failedTries);
		    else
			// No NV access for now.  Put the TPM in pending mode.
			s_DAPendingOnNV = TRUE;
		}
	}
    // Register a DA failure and reset the timers.
    DARegisterFailure(handle);
    return TPM_RC_AUTH_FAIL;
}
/* 6.4.3.3 IsSessionBindEntity() */
/* This function indicates if the entity associated with the handle is the entity, to which this
   session is bound. The binding would occur by making the bind parameter in TPM2_StartAuthSession()
   not equal to TPM_RH_NULL. The binding only occurs if the session is an HMAC session. The bind
   value is a combination of the Name and the authValue of the entity. */
static BOOL
IsSessionBindEntity(
		    TPM_HANDLE       associatedHandle,  // IN: handle to be authorized
		    SESSION         *session            // IN: associated session
		    )
{
    TPM2B_NAME     entity;             // The bind value for the entity
    // If the session is not bound, return FALSE.
    if(session->attributes.isBound)
	{
	    // Compute the bind value for the entity.
	    SessionComputeBoundEntity(associatedHandle, &entity);
	    // Compare to the bind value in the session.
	    return MemoryEqual2B(&entity.b, &session->u1.boundEntity.b);
	}
    return FALSE;
}
/* 6.4.3.4 IsPolicySessionRequired() */
/* Checks if a policy session is required for a command. If a command requires DUP or ADMIN role
   authorization, then the handle that requires that role is the first handle in the command. This
   simplifies this checking. If a new command is created that requires multiple ADMIN role
   authorizations, then it will have to be special-cased in this function. A policy session is
   required if: */
/* a) the command requires the DUP role, */
/* b) the command requires the ADMIN role and the authorized entity is an object and its
   adminWithPolicy bit is SET, or */
/* c) the command requires the ADMIN role and the authorized entity is a permanent handle or an NV
   Index. */
/* d) The authorized entity is a PCR belonging to a policy group, and has its policy initialized */
/* Return Values Meaning */
/* TRUE policy session is required */
/* FALSE policy session is not required */
static BOOL
IsPolicySessionRequired(
			COMMAND_INDEX    commandIndex,  // IN: command index
			UINT32           sessionIndex   // IN: session index
			)
{
    AUTH_ROLE       role = CommandAuthRole(commandIndex, sessionIndex);
    TPM_HT          type = HandleGetType(s_associatedHandles[sessionIndex]);
    if(role == AUTH_DUP)
	return TRUE;
    if(role == AUTH_ADMIN)
	{
	    // We allow an exception for ADMIN role in a transient object. If the object
	    // allows ADMIN role actions with authorization, then policy is not
	    // required. For all other cases, there is no way to override the command
	    // requirement that a policy be used
	    if(type == TPM_HT_TRANSIENT)
		{
		    OBJECT      *object = HandleToObject(s_associatedHandles[sessionIndex]);
		    if(!IS_ATTRIBUTE(object->publicArea.objectAttributes, TPMA_OBJECT,
				     adminWithPolicy))
			return FALSE;
		}
	    return TRUE;
	}
    if(type == TPM_HT_PCR)
	{
	    if(PCRPolicyIsAvailable(s_associatedHandles[sessionIndex]))
		{
		    TPM2B_DIGEST        policy;
		    TPMI_ALG_HASH       policyAlg;
		    policyAlg = PCRGetAuthPolicy(s_associatedHandles[sessionIndex],
						 &policy);
		    if(policyAlg != TPM_ALG_NULL)
			return TRUE;
		}
	}
    return FALSE;
}
/* 6.4.3.5 IsAuthValueAvailable() */
/* This function indicates if authValue is available and allowed for USER role authorization of an
   entity. */
/* This function is similar to IsAuthPolicyAvailable() except that it does not check the size of the
   authValue as IsAuthPolicyAvailable() does (a null authValue is a valid authorization, but a null
   policy is not a valid policy). */
/* This function does not check that the handle reference is valid or if the entity is in an
   enabled hierarchy. Those checks are assumed to have been performed during the handle
   unmarshaling. */
static BOOL
IsAuthValueAvailable(
		     TPM_HANDLE       handle,        // IN: handle of entity
		     COMMAND_INDEX    commandIndex,  // IN: command index
		     UINT32           sessionIndex   // IN: session index
		     )
{
    BOOL             result = FALSE;
    //
    switch(HandleGetType(handle))
	{
	  case TPM_HT_PERMANENT:
	    switch(handle)
		{
		    // At this point hierarchy availability has already been
		    // checked so primary seed handles are always available here
		  case TPM_RH_OWNER:
		  case TPM_RH_ENDORSEMENT:
		  case TPM_RH_PLATFORM:
#ifdef VENDOR_PERMANENT
		    // This vendor defined handle associated with the
		    // manufacturer's shared secret
		  case VENDOR_PERMANENT:
#endif
		    // The DA checking has been performed on LockoutAuth but we
		    // bypass the DA logic if we are using lockout policy. The
		    // policy would allow execution to continue an lockoutAuth
		    // could be used, even if direct use of lockoutAuth is disabled
		  case TPM_RH_LOCKOUT:
		    // NullAuth is always available.
		  case TPM_RH_NULL:
		    result = TRUE;
		    break;
		  default:
		    // Otherwise authValue is not available.
		    break;
		}
	    break;
	  case TPM_HT_TRANSIENT:
	    // A persistent object has already been loaded and the internal
	    // handle changed.
	      {
		  OBJECT          *object;
		  TPMA_OBJECT      attributes;
		  //
		  object = HandleToObject(handle);
		  attributes = object->publicArea.objectAttributes;
		  // authValue is always available for a sequence object.
		  // An alternative for this is to SET
		  // object->publicArea.objectAttributes.userWithAuth when the
		  // sequence is started.
		  if(ObjectIsSequence(object))
		      {
			  result = TRUE;
			  break;
		      }
		  // authValue is available for an object if it has its sensitive
		  // portion loaded and
		  //  1. userWithAuth bit is SET, or
		  //  2. ADMIN role is required
		  if(object->attributes.publicOnly == CLEAR
		     && (IS_ATTRIBUTE(attributes, TPMA_OBJECT, userWithAuth)
			 || (CommandAuthRole(commandIndex, sessionIndex) == AUTH_ADMIN
			     && !IS_ATTRIBUTE(attributes, TPMA_OBJECT, adminWithPolicy))))
		      result = TRUE;
	      }
	      break;
	  case TPM_HT_NV_INDEX:
	    // NV Index.
	      {
		  NV_REF           locator;
		  NV_INDEX        *nvIndex = NvGetIndexInfo(handle, &locator);
		  TPMA_NV          nvAttributes;
		  //
		  pAssert(nvIndex != 0);
		  nvAttributes = nvIndex->publicArea.attributes;
		  if(IsWriteOperation(commandIndex))
		      {
			  // AuthWrite can't be set for a PIN index
			  if(IS_ATTRIBUTE(nvAttributes, TPMA_NV, AUTHWRITE))
			      result = TRUE;
		      }
		  else
		      {
			  // A "read" operation
			  // For a PIN Index, the authValue is available as long as the
			  // Index has been written and the pinCount is less than pinLimit
			  if(IsNvPinFailIndex(nvAttributes)
			     || IsNvPinPassIndex(nvAttributes))
			      {
				  NV_PIN          pin;
				  if(!IS_ATTRIBUTE(nvAttributes, TPMA_NV, WRITTEN))
				      break; // return false
				  // get the index values
				  pin.intVal = NvGetUINT64Data(nvIndex, locator);
				  if(pin.pin.pinCount < pin.pin.pinLimit)
				      result = TRUE;
			      }
			  // For non-PIN Indexes, need to allow use of the authValue
			  else if(IS_ATTRIBUTE(nvAttributes, TPMA_NV, AUTHREAD))
			      result = TRUE;
		      }
	      }
	      break;
	  case TPM_HT_PCR:
	    // PCR handle.
	    // authValue is always allowed for PCR
	    result = TRUE;
	    break;
	  default:
	    // Otherwise, authValue is not available
	    break;
	}
    return result;
}

/* 6.4.3.6	IsAuthPolicyAvailable() */
/* This function indicates if an authPolicy is available and allowed. */
/* This function does not check that the handle reference is valid or if the entity is in an enabled
   hierarchy. Those checks are assumed to have been performed during the handle unmarshaling. */
/* Return Values Meaning */
/* TRUE authPolicy is available */
/* FALSE authPolicy is not available */
static BOOL
IsAuthPolicyAvailable(
		      TPM_HANDLE       handle,        // IN: handle of entity
		      COMMAND_INDEX    commandIndex,  // IN: command index
		      UINT32           sessionIndex   // IN: session index
		      )
{
    BOOL            result = FALSE;
    //
    switch(HandleGetType(handle))
	{
	  case TPM_HT_PERMANENT:
	    switch(handle)
		{
		    // At this point hierarchy availability has already been checked.
		  case TPM_RH_OWNER:
		    if(gp.ownerPolicy.t.size != 0)
			result = TRUE;
		    break;
		  case TPM_RH_ENDORSEMENT:
		    if(gp.endorsementPolicy.t.size != 0)
			result = TRUE;
		    break;
		  case TPM_RH_PLATFORM:
		    if(gc.platformPolicy.t.size != 0)
			result = TRUE;
		    break;
		  case TPM_RH_LOCKOUT:
		    if(gp.lockoutPolicy.t.size != 0)
			result = TRUE;
		    break;
		  default:
		    break;
		}
	    break;
	  case TPM_HT_TRANSIENT:
	      {
		  // Object handle.
		  // An evict object would already have been loaded and given a
		  // transient object handle by this point.
		  OBJECT  *object = HandleToObject(handle);
		  // Policy authorization is not available for an object with only
		  // public portion loaded.
		  if(object->attributes.publicOnly == CLEAR)
		      {
			  // Policy authorization is always available for an object but
			  // is never available for a sequence.
			  if(!ObjectIsSequence(object))
			      result = TRUE;
		      }
		  break;
	      }
	  case TPM_HT_NV_INDEX:
	    // An NV Index.
	      {
		  NV_INDEX         *nvIndex = NvGetIndexInfo(handle, NULL);
		  TPMA_NV           attributes = nvIndex->publicArea.attributes;
		  //
		  // If the policy size is not zero, check if policy can be used.
		  if(nvIndex->publicArea.authPolicy.t.size != 0)
		      {
			  // If policy session is required for this handle, always
			  // uses policy regardless of the attributes bit setting
			  if(IsPolicySessionRequired(commandIndex, sessionIndex))
			      result = TRUE;
			  // Otherwise, the presence of the policy depends on the NV
			  // attributes.
			  else if(IsWriteOperation(commandIndex))
			      {
				  if(IS_ATTRIBUTE(attributes, TPMA_NV, POLICYWRITE))
				      result = TRUE;
			      }
			  else
			      {
				  if(IS_ATTRIBUTE(attributes, TPMA_NV, POLICYREAD))
				      result = TRUE;
			      }
		      }
	      }
	      break;
	  case TPM_HT_PCR:
	    // PCR handle.
	    if(PCRPolicyIsAvailable(handle))
		result = TRUE;
	    break;
	  default:
	    break;
	}
    return result;
}
/* 6.4.4 Session Parsing Functions */
/* 6.4.4.1 ClearCpRpHashes() */
void
ClearCpRpHashes(
		COMMAND         *command
		)
{
#if ALG_SHA1
    command->sha1CpHash.t.size = 0;
    command->sha1RpHash.t.size = 0;
#endif
#if ALG_SHA256
    command->sha256CpHash.t.size = 0;
    command->sha256RpHash.t.size = 0;
#endif
#if ALG_SHA384
    command->sha384CpHash.t.size = 0;
    command->sha384RpHash.t.size = 0;
#endif
#if ALG_SHA512
    command->sha512CpHash.t.size = 0;
    command->sha512RpHash.t.size = 0;
#endif
#if ALG_SM3_256
    command->sm3_256CpHash.t.size = 0;
    command->sm3_256RpHash.t.size = 0;
#endif
}
/* 6.4.4.2 GetCpHashPointer() */
/* Function to get a pointer to the cpHash of the command */
static TPM2B_DIGEST *
GetCpHashPointer(
		 COMMAND         *command,
		 TPMI_ALG_HASH    hashAlg
		 )
{
    switch(hashAlg)
	{
#if ALG_SHA1
	  case TPM_ALG_SHA1:
	    return (TPM2B_DIGEST *)&command->sha1CpHash;
#endif
#if ALG_SHA256
	  case TPM_ALG_SHA256:
	    return (TPM2B_DIGEST *)&command->sha256CpHash;
#endif
#if ALG_SHA384
	  case TPM_ALG_SHA384:
	    return (TPM2B_DIGEST *)&command->sha384CpHash;
#endif
#if ALG_SHA512
	  case TPM_ALG_SHA512:
	    return (TPM2B_DIGEST *)&command->sha512CpHash;
#endif
#if ALG_SM3_256
	  case TPM_ALG_SM3_256:
	    return (TPM2B_DIGEST *)&command->sm3_256CpHash;
#endif
	  default:
	    break;
	}
    return NULL;
}
/* 6.4.4.3 GetRpHashPointer() */
/* Function to get a pointer to the RpHash() of the command */
static TPM2B_DIGEST *
GetRpHashPointer(
		 COMMAND         *command,
		 TPMI_ALG_HASH    hashAlg
		 )
{
    switch(hashAlg)
	{
#if ALG_SHA1
	  case TPM_ALG_SHA1:
	    return (TPM2B_DIGEST *)&command->sha1RpHash;
#endif
#if ALG_SHA256
	  case TPM_ALG_SHA256:
	    return (TPM2B_DIGEST *)&command->sha256RpHash;
#endif
#if ALG_SHA384
	  case TPM_ALG_SHA384:
	    return (TPM2B_DIGEST *)&command->sha384RpHash;
#endif
#if ALG_SHA512
	  case TPM_ALG_SHA512:
	    return (TPM2B_DIGEST *)&command->sha512RpHash;
#endif
#if ALG_SM3_256
	  case TPM_ALG_SM3_256:
	    return (TPM2B_DIGEST *)&command->sm3_256RpHash;
#endif
	  default:
	    break;
	}
    return NULL;
}
/* 6.4.4.4 ComputeCpHash() */
/* This function computes the cpHash as defined in Part 2 and described in Part 1. */
static TPM2B_DIGEST *
ComputeCpHash(
	      COMMAND         *command,       // IN: command parsing structure
	      TPMI_ALG_HASH    hashAlg        // IN: hash algorithm
	      )
{
    UINT32               i;
    HASH_STATE           hashState;
    TPM2B_NAME           name;
    TPM2B_DIGEST        *cpHash;
    // cpHash = hash(commandCode [ || authName1
    //                           [ || authName2
    //                           [ || authName 3 ]]]
    //                           [ || parameters])
    // A cpHash can contain just a commandCode only if the lone session is
    // an audit session.
    // Get pointer to the hash value
    cpHash = GetCpHashPointer(command, hashAlg);
    if(cpHash->t.size == 0)
	{
	    cpHash->t.size = CryptHashStart(&hashState, hashAlg);
	    //  Add commandCode.
	    CryptDigestUpdateInt(&hashState, sizeof(TPM_CC), command->code);
	    //  Add authNames for each of the handles.
	    for(i = 0; i < command->handleNum; i++)
		CryptDigestUpdate2B(&hashState, &EntityGetName(command->handles[i],
							       &name)->b);
	    //  Add the parameters.
	    CryptDigestUpdate(&hashState, command->parameterSize,
			      command->parameterBuffer);
	    //  Complete the hash.
	    CryptHashEnd2B(&hashState, &cpHash->b);
	}
    return cpHash;
}
/* 6.4.4.5 GetCpHash() */
/* This function is used to access a precomputed cpHash. */
static TPM2B_DIGEST *
GetCpHash(
	  COMMAND         *command,
	  TPMI_ALG_HASH    hashAlg
	  )
{
    TPM2B_DIGEST        *cpHash = GetCpHashPointer(command, hashAlg);
    //
    pAssert(cpHash->t.size != 0);
    return cpHash;
}
/* 6.4.4.6 CompareTemplateHash() */
/* This function computes the template hash and compares it to the session templateHash. It is the
   hash of the second parameter assuming that the command is TPM2_Create(), TPM2_CreatePrimary(), or
   TPM2_CreateLoaded() */
static BOOL
CompareTemplateHash(
		    COMMAND         *command,       // IN: parsing structure
		    SESSION         *session        // IN: session data
		    )
{
    BYTE                *pBuffer = command->parameterBuffer;
    INT32                pSize = command->parameterSize;
    TPM2B_DIGEST         tHash;
    UINT16               size;
    //
    // Only try this for the three commands for which it is intended
    if(command->code != TPM_CC_Create
       && command->code != TPM_CC_CreatePrimary
#ifdef TPM_CC_CreateLoaded
       && command->code != TPM_CC_CreateLoaded
#endif
       )
	return FALSE;
    // Assume that the first parameter is a TPM2B and unmarshal the size field
    // Note: this will not affect the parameter buffer and size in the calling
    // function.
    if(UINT16_Unmarshal(&size, &pBuffer, &pSize) != TPM_RC_SUCCESS)
	return FALSE;
    // reduce the space in the buffer.
    // NOTE: this could make pSize go negative if the parameters are not correct but
    // the unmarshaling code does not try to unmarshal if the remaining size is
    // negative.
    pSize -= size;
    // Advance the pointer
    pBuffer += size;
    // Get the size of what should be the template
    if(UINT16_Unmarshal(&size, &pBuffer, &pSize) != TPM_RC_SUCCESS)
	return FALSE;
    // See if this is reasonable
    if(size > pSize)
	return FALSE;
    // Hash the template data
    tHash.t.size = CryptHashBlock(session->authHashAlg, size, pBuffer,
				  sizeof(tHash.t.buffer), tHash.t.buffer);
    return(MemoryEqual2B(&session->u1.templateHash.b, &tHash.b));
}
/* 6.4.4.7 CompareNameHash() */
/* This function computes the name hash and compares it to the nameHash in the session data. */
BOOL
CompareNameHash(
		COMMAND         *command,       // IN: main parsing structure
		SESSION         *session        // IN: session structure with nameHash
		)
{
    HASH_STATE           hashState;
    TPM2B_DIGEST         nameHash;
    UINT32               i;
    TPM2B_NAME           name;
    //
    nameHash.t.size = CryptHashStart(&hashState, session->authHashAlg);
    //  Add names.
    for(i = 0; i < command->handleNum; i++)
	CryptDigestUpdate2B(&hashState, &EntityGetName(command->handles[i],
						       &name)->b);
    //  Complete hash.
    CryptHashEnd2B(&hashState, &nameHash.b);
    // and compare
    return MemoryEqual(session->u1.nameHash.t.buffer, nameHash.t.buffer,
		       nameHash.t.size);
}
/* 6.4.4.8 CheckPWAuthSession() */
/* This function validates the authorization provided in a PWAP session. It compares the input value
   to authValue of the authorized entity. Argument sessionIndex is used to get handles handle of the
   referenced entities from s_inputAuthValues[] and s_associatedHandles[]. */
/* Error Returns Meaning */
/* TPM_RC_AUTH_FAIL authorization fails and increments DA failure count */
/* TPM_RC_BAD_AUTH authorization fails but DA does not apply */
static TPM_RC
CheckPWAuthSession(
		   UINT32           sessionIndex   // IN: index of session to be processed
		   )
{
    TPM2B_AUTH      authValue;
    TPM_HANDLE      associatedHandle = s_associatedHandles[sessionIndex];
    // Strip trailing zeros from the password.
    MemoryRemoveTrailingZeros(&s_inputAuthValues[sessionIndex]);
    // Get the authValue with trailing zeros removed
    EntityGetAuthValue(associatedHandle, &authValue);
    // Success if the values are identical.
    if(MemoryEqual2B(&s_inputAuthValues[sessionIndex].b, &authValue.b))
	{
	    return TPM_RC_SUCCESS;
	}
    else                    // if the digests are not identical
	{
	    // Invoke DA protection if applicable.
	    return IncrementLockout(sessionIndex);
	}
}
/* 6.4.4.9 ComputeCommandHMAC() */
/* This function computes the HMAC for an authorization session in a command. */
static TPM2B_DIGEST *
ComputeCommandHMAC(
		   COMMAND         *command,       // IN: primary control structure
		   UINT32           sessionIndex,  // IN: index of session to be processed
		   TPM2B_DIGEST    *hmac           // OUT: authorization HMAC
		   )
{
    TPM2B_TYPE(KEY, (sizeof(AUTH_VALUE) * 2));
    TPM2B_KEY        key;
    BYTE             marshalBuffer[sizeof(TPMA_SESSION)];
    BYTE            *buffer;
    UINT32           marshalSize;
    HMAC_STATE       hmacState;
    TPM2B_NONCE     *nonceDecrypt;
    TPM2B_NONCE     *nonceEncrypt;
    SESSION         *session;
    nonceDecrypt = NULL;
    nonceEncrypt = NULL;
    // Determine if extra nonceTPM values are going to be required.
    // If this is the first session (sessionIndex = 0) and it is an authorization
    // session that uses an HMAC, then check if additional session nonces are to be
    // included.
    if(sessionIndex == 0
       && s_associatedHandles[sessionIndex] != TPM_RH_UNASSIGNED)
	{
	    // If there is a decrypt session and if this is not the decrypt session,
	    // then an extra nonce may be needed.
	    if(s_decryptSessionIndex != UNDEFINED_INDEX
	       && s_decryptSessionIndex != sessionIndex)
		{
		    // Will add the nonce for the decrypt session.
		    SESSION *decryptSession
			= SessionGet(s_sessionHandles[s_decryptSessionIndex]);
		    nonceDecrypt = &decryptSession->nonceTPM;
		}
	    // Now repeat for the encrypt session.
	    if(s_encryptSessionIndex != UNDEFINED_INDEX
	       && s_encryptSessionIndex != sessionIndex
	       && s_encryptSessionIndex != s_decryptSessionIndex)
		{
		    // Have to have the nonce for the encrypt session.
		    SESSION *encryptSession
			= SessionGet(s_sessionHandles[s_encryptSessionIndex]);
		    nonceEncrypt = &encryptSession->nonceTPM;
		}
	}
    // Continue with the HMAC processing.
    session = SessionGet(s_sessionHandles[sessionIndex]);
    // Generate HMAC key.
    MemoryCopy2B(&key.b, &session->sessionKey.b, sizeof(key.t.buffer));
    // Check if the session has an associated handle and if the associated entity
    // is the one to which the session is bound. If not, add the authValue of
    // this entity to the HMAC key.
    // If the session is bound to the object or the session is a policy session
    // with no authValue required, do not include the authValue in the HMAC key.
    // Note: For a policy session, its isBound attribute is CLEARED.
    // Include the entity authValue if it is needed
    if(session->attributes.includeAuth == SET)
	{
	    TPM2B_AUTH          authValue;
	    // Get the entity authValue with trailing zeros removed
	    EntityGetAuthValue(s_associatedHandles[sessionIndex], &authValue);
	    // add the authValue to the HMAC key
	    MemoryConcat2B(&key.b, &authValue.b, sizeof(key.t.buffer));
	}
    // if the HMAC key size is 0, a NULL string HMAC is allowed
    if(key.t.size == 0
       && s_inputAuthValues[sessionIndex].t.size == 0)
	{
	    hmac->t.size = 0;
	    return hmac;
	}
    // Start HMAC
    hmac->t.size = CryptHmacStart2B(&hmacState, session->authHashAlg, &key.b);
    //  Add cpHash
    CryptDigestUpdate2B(&hmacState.hashState,
			&ComputeCpHash(command, session->authHashAlg)->b);
    //  Add nonces as required
    CryptDigestUpdate2B(&hmacState.hashState, &s_nonceCaller[sessionIndex].b);
    CryptDigestUpdate2B(&hmacState.hashState, &session->nonceTPM.b);
    if(nonceDecrypt != NULL)
	CryptDigestUpdate2B(&hmacState.hashState, &nonceDecrypt->b);
    if(nonceEncrypt != NULL)
	CryptDigestUpdate2B(&hmacState.hashState, &nonceEncrypt->b);
    //  Add sessionAttributes
    buffer = marshalBuffer;
    marshalSize = TPMA_SESSION_Marshal(&(s_attributes[sessionIndex]),
				       &buffer, NULL);
    CryptDigestUpdate(&hmacState.hashState, marshalSize, marshalBuffer);
    // Complete the HMAC computation
    CryptHmacEnd2B(&hmacState, &hmac->b);
    return hmac;
}
/* 6.4.4.10 CheckSessionHMAC() */
/* This function checks the HMAC of in a session. It uses ComputeCommandHMAC() to compute the
   expected HMAC value and then compares the result with the HMAC in the authorization session. The
   authorization is successful if they are the same. */
/* If the authorizations are not the same, IncrementLockout() is called. It will return
   TPM_RC_AUTH_FAIL if the failure caused the failureCount to increment. Otherwise, it will return
   TPM_RC_BAD_AUTH. */
/* Error Returns Meaning */
/* TPM_RC_AUTH_FAIL authorization failure caused failureCount increment */
/* TPM_RC_BAD_AUTH authorization failure did not cause failureCount increment */
static TPM_RC
CheckSessionHMAC(
		 COMMAND         *command,       // IN: primary control structure
		 UINT32           sessionIndex   // IN: index of session to be processed
		 )
{
    TPM2B_DIGEST        hmac;           // authHMAC for comparing
    // Compute authHMAC
   ComputeCommandHMAC(command, sessionIndex, &hmac);
    // Compare the input HMAC with the authHMAC computed above.
    if(!MemoryEqual2B(&s_inputAuthValues[sessionIndex].b, &hmac.b))
	{
	    // If an HMAC session has a failure, invoke the anti-hammering
	    // if it applies to the authorized entity or the session.
	    // Otherwise, just indicate that the authorization is bad.
	    return IncrementLockout(sessionIndex);
	}
    return TPM_RC_SUCCESS;
}
/* 6.4.4.11 CheckPolicyAuthSession() */
/* This function is used to validate the authorization in a policy session. This function performs
   the following comparisons to see if a policy authorization is properly provided. The check
   are: */
/* a) compare policyDigest in session with authPolicy associated with the entity to be
   authorized; */
/* b) compare timeout if applicable; */
/* c) compare commandCode if applicable; */
/* d) compare cpHash if applicable; and */
/* e) see if PCR values have changed since computed. */
/* If all the above checks succeed, the handle is authorized. The order of these comparisons is not
   important because any failure will result in the same error code. */
/* Error Returns Meaning */
/* TPM_RC_PCR_CHANGED PCR value is not current */
/* TPM_RC_POLICY_FAIL policy session fails */
/* TPM_RC_LOCALITY command locality is not allowed */
/* TPM_RC_POLICY_CC CC doesn't match */
/* TPM_RC_EXPIRED policy session has expired */
/* TPM_RC_PP PP is required but not asserted */
/* TPM_RC_NV_UNAVAILABLE NV is not available for write */
/* TPM_RC_NV_RATE NV is rate limiting */
static TPM_RC
CheckPolicyAuthSession(
		       COMMAND         *command,       // IN: primary parsing structure
		       UINT32           sessionIndex   // IN: index of session to be processed
		       )
{
    SESSION             *session;
    TPM2B_DIGEST         authPolicy;
    TPMI_ALG_HASH        policyAlg;
    UINT8                locality;
    // Initialize pointer to the authorization session.
    session = SessionGet(s_sessionHandles[sessionIndex]);
    // If the command is TPM2_PolicySecret(), make sure that
    // either password or authValue is required
    if(command->code == TPM_CC_PolicySecret
       &&  session->attributes.isPasswordNeeded == CLEAR
       &&  session->attributes.isAuthValueNeeded == CLEAR)
	return TPM_RC_MODE;
    // See if the PCR counter for the session is still valid.
    if(!SessionPCRValueIsCurrent(session))
	return TPM_RC_PCR_CHANGED;
    // Get authPolicy.
    policyAlg = EntityGetAuthPolicy(s_associatedHandles[sessionIndex],
				    &authPolicy);
    // Compare authPolicy.
    if(!MemoryEqual2B(&session->u2.policyDigest.b, &authPolicy.b))
	return TPM_RC_POLICY_FAIL;
    // Policy is OK so check if the other factors are correct
    // Compare policy hash algorithm.
    if(policyAlg != session->authHashAlg)
	return TPM_RC_POLICY_FAIL;
    // Compare timeout.
    if(session->timeout != 0)
	{
	    // Cannot compare time if clock stop advancing.  An TPM_RC_NV_UNAVAILABLE
	    // or TPM_RC_NV_RATE error may be returned here. This doesn't mean that
	    // a new nonce will be created just that, because TPM time can't advance
	    // we can't do time-based operations.
	    RETURN_IF_NV_IS_NOT_AVAILABLE;
	    if((session->timeout < g_time)
	       || (session->epoch != g_timeEpoch))
		return TPM_RC_EXPIRED;
	}
    // If command code is provided it must match
    if(session->commandCode != 0)
	{
	    if(session->commandCode != command->code)
		return TPM_RC_POLICY_CC;
	}
    else
	{
	    // If command requires a DUP or ADMIN authorization, the session must have
	    // command code set.
	    AUTH_ROLE   role = CommandAuthRole(command->index, sessionIndex);
	    if(role == AUTH_ADMIN || role == AUTH_DUP)
		return TPM_RC_POLICY_FAIL;
	}
    // Check command locality.
    {
	BYTE         sessionLocality[sizeof(TPMA_LOCALITY)];
	BYTE        *buffer = sessionLocality;
	// Get existing locality setting in canonical form
	sessionLocality[0] = 0;
	TPMA_LOCALITY_Marshal(&session->commandLocality, &buffer, NULL);
	// See if the locality has been set
	if(sessionLocality[0] != 0)
	    {
		// If so, get the current locality
		locality = _plat__LocalityGet();
		if(locality < 5)
		    {
			if(((sessionLocality[0] & (1 << locality)) == 0)
			   || sessionLocality[0] > 31)
			    return TPM_RC_LOCALITY;
		    }
		else if(locality > 31)
		    {
			if(sessionLocality[0] != locality)
			    return TPM_RC_LOCALITY;
		    }
		else
		    {
			// Could throw an assert here but a locality error is just
			// as good. It just means that, whatever the locality is, it isn't
			// the locality requested so...
			return TPM_RC_LOCALITY;
		    }
	    }
    } // end of locality check
    // Check physical presence.
    if(session->attributes.isPPRequired == SET
       && !_plat__PhysicalPresenceAsserted())
	return TPM_RC_PP;
    // Compare cpHash/nameHash if defined, or if the command requires an ADMIN or
    // DUP role for this handle.
    if(session->u1.cpHash.b.size != 0)
	{
	    BOOL        OK;
	    if(session->attributes.isCpHashDefined)
		// Compare cpHash.
		OK = MemoryEqual2B(&session->u1.cpHash.b,
				   &ComputeCpHash(command, session->authHashAlg)->b);
	    else if(session->attributes.isTemplateSet)
		OK = CompareTemplateHash(command, session);
	    else
		OK = CompareNameHash(command, session);
	    if(!OK)
		return TPM_RCS_POLICY_FAIL;
	}
    if(session->attributes.checkNvWritten)
	{
	    NV_REF           locator;
	    NV_INDEX        *nvIndex;
	    // If this is not an NV index, the policy makes no sense so fail it.
	    if(HandleGetType(s_associatedHandles[sessionIndex]) != TPM_HT_NV_INDEX)
		return TPM_RC_POLICY_FAIL;
	    // Get the index data
	    nvIndex = NvGetIndexInfo(s_associatedHandles[sessionIndex], &locator);
	    // Make sure that the TPMA_WRITTEN_ATTRIBUTE has the desired state
	    if((IS_ATTRIBUTE(nvIndex->publicArea.attributes, TPMA_NV, WRITTEN))
	       != (session->attributes.nvWrittenState == SET))
		return TPM_RC_POLICY_FAIL;
	}
    return TPM_RC_SUCCESS;
}
/* 6.4.4.12 RetrieveSessionData() */
/* This function will unmarshal the sessions in the session area of a command. The values are placed
   in the arrays that are defined at the beginning of this file. The normal unmarshaling errors are
   possible. */
/* Error Returns Meaning */
/* TPM_RC_SUCCSS unmarshaled without error */
/* TPM_RC_SIZE the number of bytes unmarshaled is not the same as the value for authorizationSize in
   the command */
static TPM_RC
RetrieveSessionData(
		    COMMAND         *command        // IN: main parsing structure for command
		    )
{
    int              i;
    TPM_RC           result;
    SESSION         *session;
    TPMA_SESSION     sessionAttributes;
    TPM_HT           sessionType;
    INT32            sessionIndex;
    TPM_RC           errorIndex;
    s_decryptSessionIndex = UNDEFINED_INDEX;
    s_encryptSessionIndex = UNDEFINED_INDEX;
    s_auditSessionIndex = UNDEFINED_INDEX;
    for(sessionIndex = 0; command->authSize > 0; sessionIndex++)
	{
	    errorIndex = TPM_RC_S + g_rcIndex[sessionIndex];
	    // If maximum allowed number of sessions has been parsed, return a size
	    // error with a session number that is larger than the number of allowed
	    // sessions
	    if(sessionIndex == MAX_SESSION_NUM)
		return TPM_RCS_SIZE + errorIndex;
	    // make sure that the associated handle for each session starts out
	    // unassigned
	    s_associatedHandles[sessionIndex] = TPM_RH_UNASSIGNED;
	    // First parameter: Session handle.
	    result = TPMI_SH_AUTH_SESSION_Unmarshal(
						    &s_sessionHandles[sessionIndex],
						    &command->parameterBuffer,
						    &command->authSize, TRUE);
	    if(result != TPM_RC_SUCCESS)
		return result + TPM_RC_S + g_rcIndex[sessionIndex];
	    // Second parameter: Nonce.
	    result = TPM2B_NONCE_Unmarshal(&s_nonceCaller[sessionIndex],
					   &command->parameterBuffer,
					   &command->authSize);
	    if(result != TPM_RC_SUCCESS)
		return result + TPM_RC_S + g_rcIndex[sessionIndex];
	    // Third parameter: sessionAttributes.
	    result = TPMA_SESSION_Unmarshal(&s_attributes[sessionIndex],
					    &command->parameterBuffer,
					    &command->authSize);
	    if(result != TPM_RC_SUCCESS)
		return result + TPM_RC_S + g_rcIndex[sessionIndex];
	    // Fourth parameter: authValue (PW or HMAC).
	    result = TPM2B_AUTH_Unmarshal(&s_inputAuthValues[sessionIndex],
					  &command->parameterBuffer,
					  &command->authSize);
	    if(result != TPM_RC_SUCCESS)
		return result + errorIndex;
	    sessionAttributes = s_attributes[sessionIndex];
	    if(s_sessionHandles[sessionIndex] == TPM_RS_PW)
		{
		    // A PWAP session needs additional processing.
		    //     Can't have any attributes set other than continueSession bit
		    if(IS_ATTRIBUTE(sessionAttributes, TPMA_SESSION, encrypt)
		       || IS_ATTRIBUTE(sessionAttributes, TPMA_SESSION, decrypt)
		       || IS_ATTRIBUTE(sessionAttributes, TPMA_SESSION, audit)
		       || IS_ATTRIBUTE(sessionAttributes, TPMA_SESSION, auditExclusive)
		       || IS_ATTRIBUTE(sessionAttributes, TPMA_SESSION, auditReset))
			return TPM_RCS_ATTRIBUTES + errorIndex;
		    //     The nonce size must be zero.
		    if(s_nonceCaller[sessionIndex].t.size != 0)
			return TPM_RCS_NONCE + errorIndex;
		    continue;
		}
	    // For not password sessions...
	    // Find out if the session is loaded.
	    if(!SessionIsLoaded(s_sessionHandles[sessionIndex]))
		return TPM_RC_REFERENCE_S0 + sessionIndex;
	    sessionType = HandleGetType(s_sessionHandles[sessionIndex]);
	    session = SessionGet(s_sessionHandles[sessionIndex]);
	    // Check if the session is an HMAC/policy session.
	    if((session->attributes.isPolicy == SET
		&& sessionType == TPM_HT_HMAC_SESSION)
	       || (session->attributes.isPolicy == CLEAR
		   && sessionType == TPM_HT_POLICY_SESSION))
		return TPM_RCS_HANDLE + errorIndex;
	    // Check that this handle has not previously been used.
	    for(i = 0; i < sessionIndex; i++)
		{
		    if(s_sessionHandles[i] == s_sessionHandles[sessionIndex])
			return TPM_RCS_HANDLE + errorIndex;
		}
	    // If the session is used for parameter encryption or audit as well, set
	    // the corresponding Indexes.
	    // First process decrypt.
	    if(IS_ATTRIBUTE(sessionAttributes, TPMA_SESSION, decrypt))
		{
		    // Check if the commandCode allows command parameter encryption.
		    if(DecryptSize(command->index) == 0)
			return TPM_RCS_ATTRIBUTES + errorIndex;
		    // Encrypt attribute can only appear in one session
		    if(s_decryptSessionIndex != UNDEFINED_INDEX)
			return TPM_RCS_ATTRIBUTES + errorIndex;
		    // Can't decrypt if the session's symmetric algorithm is TPM_ALG_NULL
		    if(session->symmetric.algorithm == TPM_ALG_NULL)
			return TPM_RCS_SYMMETRIC + errorIndex;
		    // All checks passed, so set the index for the session used to decrypt
		    // a command parameter.
		    s_decryptSessionIndex = sessionIndex;
		}
	    // Now process encrypt.
	    if(IS_ATTRIBUTE(sessionAttributes, TPMA_SESSION, encrypt))
		{
		    // Check if the commandCode allows response parameter encryption.
		    if(EncryptSize(command->index) == 0)
			return TPM_RCS_ATTRIBUTES + errorIndex;
		    // Encrypt attribute can only appear in one session.
		    if(s_encryptSessionIndex != UNDEFINED_INDEX)
			return TPM_RCS_ATTRIBUTES + errorIndex;
		    // Can't encrypt if the session's symmetric algorithm is TPM_ALG_NULL
		    if(session->symmetric.algorithm == TPM_ALG_NULL)
			return TPM_RCS_SYMMETRIC + errorIndex;
		    // All checks passed, so set the index for the session used to encrypt
		    // a response parameter.
		    s_encryptSessionIndex = sessionIndex;
		}
	    // At last process audit.
	    if(IS_ATTRIBUTE(sessionAttributes, TPMA_SESSION, audit))
		{
		    // Audit attribute can only appear in one session.
		    if(s_auditSessionIndex != UNDEFINED_INDEX)
			return TPM_RCS_ATTRIBUTES + errorIndex;
		    // An audit session can not be policy session.
		    if(HandleGetType(s_sessionHandles[sessionIndex])
		       == TPM_HT_POLICY_SESSION)
			return TPM_RCS_ATTRIBUTES + errorIndex;
		    // If this is a reset of the audit session, or the first use
		    // of the session as an audit session, it doesn't matter what
		    // the exclusive state is. The session will become exclusive.
		    if(!IS_ATTRIBUTE(sessionAttributes, TPMA_SESSION, auditReset)
		       && session->attributes.isAudit == SET)
			{
			    // Not first use or reset. If auditExlusive is SET, then this
			    // session must be the current exclusive session.
			    if(IS_ATTRIBUTE(sessionAttributes, TPMA_SESSION, auditExclusive)
			       && g_exclusiveAuditSession != s_sessionHandles[sessionIndex])
				return TPM_RC_EXCLUSIVE;
			}
		    s_auditSessionIndex = sessionIndex;
		}
	    // Initialize associated handle as undefined. This will be changed when
	    // the handles are processed.
	    s_associatedHandles[sessionIndex] = TPM_RH_UNASSIGNED;
	}
    command->sessionNum = sessionIndex;
    return TPM_RC_SUCCESS;
}
/* 6.4.4.13 CheckLockedOut() */
/* This function checks to see if the TPM is in lockout. This function should only be called if the
   entity being checked is subject to DA protection. The TPM is in lockout if the NV is not
   available and a DA write is pending. Otherwise the TPM is locked out if checking for lockoutAuth
   (lockoutAuthCheck == TRUE) and use of lockoutAuth is disabled, or failedTries >= maxTries */
/* Error Returns Meaning */
/* TPM_RC_NV_RATE NV is rate limiting */
/* TPM_RC_NV_UNAVAILABLE NV is not available at this time */
/* TPM_RC_LOCKOUT TPM is in lockout */
static TPM_RC
CheckLockedOut(
	       BOOL             lockoutAuthCheck   // IN: TRUE if checking is for lockoutAuth
	       )
{
    // If NV is unavailable, and current cycle state recorded in NV is not
    // SU_NONE_VALUE, refuse to check any authorization because we would
    // not be able to handle a DA failure.
    if(!NV_IS_AVAILABLE && NV_IS_ORDERLY)
	return g_NvStatus;
    // Check if DA info needs to be updated in NV.
    if(s_DAPendingOnNV)
	{
	    // If NV is accessible,
	    RETURN_IF_NV_IS_NOT_AVAILABLE;
	    // ... write the pending DA data and proceed.
	    NV_SYNC_PERSISTENT(lockOutAuthEnabled);
	    NV_SYNC_PERSISTENT(failedTries);
	    s_DAPendingOnNV = FALSE;
	}
    // Lockout is in effect if checking for lockoutAuth and use of lockoutAuth
    // is disabled...
    if(lockoutAuthCheck)
	{
	    if(gp.lockOutAuthEnabled == FALSE)
		return TPM_RC_LOCKOUT;
	}
    else
	{
	    // ... or if the number of failed tries has been maxed out.
	    if(gp.failedTries >= gp.maxTries)
		return TPM_RC_LOCKOUT;
#ifdef USE_DA_USED
	    // If the daUsed flag is not SET, then no DA validation until the
	    // daUsed state is written to NV
	    if(!g_daUsed)
		{
		    RETURN_IF_NV_IS_NOT_AVAILABLE;
		    g_daUsed = TRUE;
		    gp.orderlyState = SU_DA_USED_VALUE;
		    NV_SYNC_PERSISTENT(orderlyState);
		    return TPM_RC_RETRY;
		}
#endif
	}
    return TPM_RC_SUCCESS;
}
/* 6.4.4.14 CheckAuthSession() */
/* This function checks that the authorization session properly authorizes the use of the associated
   handle. */
/* Error Returns Meaning */
/* TPM_RC_LOCKOUT entity is protected by DA and TPM is in lockout, or TPM is locked out on NV update
   pending on DA parameters */
/* TPM_RC_PP Physical Presence is required but not provided */
/* TPM_RC_AUTH_FAIL HMAC or PW authorization failed with DA side-effects (can be a policy
   session) */
/* TPM_RC_BAD_AUTH HMAC or PW authorization failed without DA side-effects (can be a policy
   session) */
/* TPM_RC_POLICY_FAIL if policy session fails */
/* TPM_RC_POLICY_CC command code of policy was wrong */
/* TPM_RC_EXPIRED the policy session has expired */
/* TPM_RC_PCR ??? */
/* TPM_RC_AUTH_UNAVAILABLE authValue or authPolicy unavailable */
static TPM_RC
CheckAuthSession(
		 COMMAND         *command,       // IN: primary parsing structure
		 UINT32           sessionIndex   // IN: index of session to be processed
		 )
{
    TPM_RC           result = TPM_RC_SUCCESS;
    SESSION         *session = NULL;
    TPM_HANDLE       sessionHandle = s_sessionHandles[sessionIndex];
    TPM_HANDLE       associatedHandle = s_associatedHandles[sessionIndex];
    TPM_HT           sessionHandleType = HandleGetType(sessionHandle);
    pAssert(sessionHandle != TPM_RH_UNASSIGNED);
    // Take care of physical presence
    if(associatedHandle == TPM_RH_PLATFORM)
	{
	    // If the physical presence is required for this command, check for PP
	    // assertion. If it isn't asserted, no point going any further.
	    if(PhysicalPresenceIsRequired(command->index)
	       && !_plat__PhysicalPresenceAsserted())
		return TPM_RC_PP;
	}
    if(sessionHandle != TPM_RS_PW)
	{
	    session = SessionGet(sessionHandle);
	    // Set includeAuth to indicate if DA checking will be required and if the
	    // authValue will be included in any HMAC.
	    if(sessionHandleType == TPM_HT_POLICY_SESSION)
		{
		    // For a policy session, will check the DA status of the entity if either
		    // isAuthValueNeeded or isPasswordNeeded is SET.
		    session->attributes.includeAuth =
			session->attributes.isAuthValueNeeded
			|| session->attributes.isPasswordNeeded;
		}
	    else
		{
		    // For an HMAC session, need to check unless the session
		    // is bound.
		    session->attributes.includeAuth =
			!IsSessionBindEntity(s_associatedHandles[sessionIndex], session);
		}
	}
    // If the authorization session is going to use an authValue, then make sure
    // that access to that authValue isn't locked out.
    // Note: session == NULL for a PW session.
    if(session == NULL || session->attributes.includeAuth)
	{
	    // See if entity is subject to lockout.
	    if(!IsDAExempted(associatedHandle))
		{
		    // See if in lockout
		    result = CheckLockedOut(associatedHandle == TPM_RH_LOCKOUT);
		    if(result != TPM_RC_SUCCESS)
			return result;
		}
	}
    // Policy or HMAC+PW?
    if(sessionHandleType != TPM_HT_POLICY_SESSION)
	{
	    // for non-policy session make sure that a policy session is not required
	    if(IsPolicySessionRequired(command->index, sessionIndex))
		return TPM_RC_AUTH_TYPE;
	    // The authValue must be available.
	    // Note: The authValue is going to be "used" even if it is an EmptyAuth.
	    // and the session is bound.
	    if(!IsAuthValueAvailable(associatedHandle, command->index, sessionIndex))
		return TPM_RC_AUTH_UNAVAILABLE;
	}
    else
	{
	    // ... see if the entity has a policy, ...
	    // Note: IsAutPolciyAvalable will return FALSE if the sensitive area of the
	    // object is not loaded
	    if(!IsAuthPolicyAvailable(associatedHandle, command->index, sessionIndex))
		return TPM_RC_AUTH_UNAVAILABLE;
	    // ... and check the policy session.
	    result = CheckPolicyAuthSession(command, sessionIndex);
	    if(result != TPM_RC_SUCCESS)
		return result;
	}
    // Check authorization according to the type
    if(session == NULL || session->attributes.isPasswordNeeded == SET)
	result = CheckPWAuthSession(sessionIndex);
    else
	result = CheckSessionHMAC(command, sessionIndex);
    // Do processing for PIN Indexes are only three possibilities for 'result' at
    // this point.
    //  TPM_RC_SUCCESS
    //  TPM_RC_AUTH_FAIL
    //  TPM_RC_BAD_AUTH
    // For all these cases, we would have to process a PIN index if the
    // authValue of the index was used for authorization.
    // See if we need to do anything to a PIN index
    if(TPM_HT_NV_INDEX == HandleGetType(associatedHandle))
	{
	    NV_REF           locator;
	    NV_INDEX        *nvIndex = NvGetIndexInfo(associatedHandle, &locator);
	    NV_PIN           pinData;
	    TPMA_NV          nvAttributes;
	    pAssert(nvIndex != NULL);
	    nvAttributes = nvIndex->publicArea.attributes;
	    // If this is a PIN FAIL index and the value has been written
	    // then we can update the counter (increment or clear)
	    if(IsNvPinFailIndex(nvAttributes)
	       && IS_ATTRIBUTE(nvAttributes, TPMA_NV, WRITTEN))
		{
		    pinData.intVal = NvGetUINT64Data(nvIndex, locator);
		    if(result != TPM_RC_SUCCESS)
			pinData.pin.pinCount++;
		    else
			pinData.pin.pinCount = 0;
		    NvWriteUINT64Data(nvIndex, pinData.intVal);
		}
	    // If this is a PIN PASS Index, increment if we have used the
	    // authorization value for anything other than NV_Read.
	    // NOTE: If the counter has already hit the limit, then we
	    // would not get here because the authorization value would not
	    // be available and the TPM would have returned before it gets here
	    else if(IsNvPinPassIndex(nvAttributes)
		    && IS_ATTRIBUTE(nvAttributes, TPMA_NV, WRITTEN)
		    && result == TPM_RC_SUCCESS)
		{
		    // If the access is valid, then increment the use counter
		    pinData.intVal = NvGetUINT64Data(nvIndex, locator);
		    pinData.pin.pinCount++;
		    NvWriteUINT64Data(nvIndex, pinData.intVal);
		}
	}
    return result;
}
#ifdef  TPM_CC_GetCommandAuditDigest
/* 6.4.4.15 CheckCommandAudit() */
/* This function is called before the command is processed if audit is enabled for the command. It
   will check to see if the audit can be performed and will ensure that the cpHash is available for
   the audit. */
/* Error Returns Meaning */
/* TPM_RC_NV_UNAVAILABLE NV is not available for write */
/* TPM_RC_NV_RATE NV is rate limiting */
static TPM_RC
CheckCommandAudit(
		  COMMAND         *command
		  )
{
    // If the audit digest is clear and command audit is required, NV must be
    // available so that TPM2_GetCommandAuditDigest() is able to increment
    // audit counter. If NV is not available, the function bails out to prevent
    // the TPM from attempting an operation that would fail anyway.
    if(gr.commandAuditDigest.t.size == 0
       || GetCommandCode(command->index) == TPM_CC_GetCommandAuditDigest)
	{
	    RETURN_IF_NV_IS_NOT_AVAILABLE;
	}
    // Make sure that the cpHash is computed for the algorithm
    ComputeCpHash(command, gp.auditHashAlg);
    return TPM_RC_SUCCESS;
}
#endif
/* 6.4.4.16 ParseSessionBuffer() */
/* This function is the entry function for command session processing. It iterates sessions in
   session area and reports if the required authorization has been properly provided. It also
   processes audit session and passes the information of encryption sessions to parameter encryption
   module. */
/* Error Returns Meaning */
/* various parsing failure or authorization failure */
TPM_RC
ParseSessionBuffer(
		   COMMAND         *command        // IN: the structure that contains
		   )
{
    TPM_RC               result;
    UINT32               i;
    INT32                size = 0;
    TPM2B_AUTH           extraKey;
    UINT32               sessionIndex;
    TPM_RC               errorIndex;
    SESSION             *session = NULL;
    // Check if a command allows any session in its session area.
    if(!IsSessionAllowed(command->index))
	return TPM_RC_AUTH_CONTEXT;
    // Default-initialization.
    command->sessionNum = 0;
    result = RetrieveSessionData(command);
    if(result != TPM_RC_SUCCESS)
	return result;
    // There is no command in the TPM spec that has more handles than
    // MAX_SESSION_NUM.
    pAssert(command->handleNum <= MAX_SESSION_NUM);
    // Associate the session with an authorization handle.
    for(i = 0; i < command->handleNum; i++)
	{
	    if(CommandAuthRole(command->index, i) != AUTH_NONE)
		{
		    // If the received session number is less than the number of handles
		    // that requires authorization, an error should be returned.
		    // Note: for all the TPM 2.0 commands, handles requiring
		    // authorization come first in a command input and there are only ever
		    // two values requiring authorization
		    if(i > (command->sessionNum - 1))
			return TPM_RC_AUTH_MISSING;
		    // Record the handle associated with the authorization session
		    s_associatedHandles[i] = command->handles[i];
		}
	}
    // Consistency checks are done first to avoid authorization failure when the
    // command will not be executed anyway.
    for(sessionIndex = 0; sessionIndex < command->sessionNum; sessionIndex++)
	{
	    errorIndex = TPM_RC_S + g_rcIndex[sessionIndex];
	    // PW session must be an authorization session
	    if(s_sessionHandles[sessionIndex] == TPM_RS_PW)
		{
		    if(s_associatedHandles[sessionIndex] == TPM_RH_UNASSIGNED)
			return TPM_RCS_HANDLE + errorIndex;
		    // a password session can't be audit, encrypt or decrypt
		    if(IS_ATTRIBUTE(s_attributes[sessionIndex], TPMA_SESSION, audit)
		       || IS_ATTRIBUTE(s_attributes[sessionIndex], TPMA_SESSION, encrypt)
		       || IS_ATTRIBUTE(s_attributes[sessionIndex], TPMA_SESSION, decrypt))
			return TPM_RCS_ATTRIBUTES + errorIndex;
		    session = NULL;
		}
	    else
		{
		    session = SessionGet(s_sessionHandles[sessionIndex]);
		    // A trial session can not appear in session area, because it cannot
		    // be used for authorization, audit or encrypt/decrypt.
		    if(session->attributes.isTrialPolicy == SET)
			return TPM_RCS_ATTRIBUTES + errorIndex;
		    // See if the session is bound to a DA protected entity
		    // NOTE: Since a policy session is never bound, a policy is still
		    // usable even if the object is DA protected and the TPM is in
		    // lockout.
		    if(session->attributes.isDaBound == SET)
			{
			    result = CheckLockedOut(session->attributes.isLockoutBound == SET);
			    if(result != TPM_RC_SUCCESS)
				return result;
			}
		    // If this session is for auditing, make sure the cpHash is computed.
		    if(IS_ATTRIBUTE(s_attributes[sessionIndex], TPMA_SESSION, audit))
			ComputeCpHash(command, session->authHashAlg);
		}
	    // if the session has an associated handle, check the authorization
	    if(s_associatedHandles[sessionIndex] != TPM_RH_UNASSIGNED)
		{
		    result = CheckAuthSession(command, sessionIndex);
		    if(result != TPM_RC_SUCCESS)
			return RcSafeAddToResult(result, errorIndex);
		}
	    else
		{
		    // a session that is not for authorization must either be encrypt,
		    // decrypt, or audit
		    if(!IS_ATTRIBUTE(s_attributes[sessionIndex], TPMA_SESSION, audit)
		       &&  !IS_ATTRIBUTE(s_attributes[sessionIndex], TPMA_SESSION, encrypt)
		       &&  !IS_ATTRIBUTE(s_attributes[sessionIndex], TPMA_SESSION, decrypt))
			return TPM_RCS_ATTRIBUTES + errorIndex;
		    // no authValue included in any of the HMAC computations
		    pAssert(session != NULL);
		    session->attributes.includeAuth = CLEAR;
		    // check HMAC for encrypt/decrypt/audit only sessions
		    result = CheckSessionHMAC(command, sessionIndex);
		    if(result != TPM_RC_SUCCESS)
			return RcSafeAddToResult(result, errorIndex);
		}
	}
#ifdef  TPM_CC_GetCommandAuditDigest
    // Check if the command should be audited. Need to do this before any parameter
    // encryption so that the cpHash for the audit is correct
    if(CommandAuditIsRequired(command->index))
	{
	    result = CheckCommandAudit(command);
	    if(result != TPM_RC_SUCCESS)
		return result;              // No session number to reference
	}
#endif
    // Decrypt the first parameter if applicable. This should be the last operation
    // in session processing.
    // If the encrypt session is associated with a handle and the handle's
    // authValue is available, then authValue is concatenated with sessionKey to
    // generate encryption key, no matter if the handle is the session bound entity
    // or not.
    if(s_decryptSessionIndex != UNDEFINED_INDEX)
	{
	    // If this is an authorization session, include the authValue in the
	    // generation of the decryption key
	    if(s_associatedHandles[s_decryptSessionIndex] != TPM_RH_UNASSIGNED)
		{
		    EntityGetAuthValue(s_associatedHandles[s_decryptSessionIndex],
				       &extraKey);
		}
	    else
		{
		    extraKey.b.size = 0;
		}
	    size = DecryptSize(command->index);
	    result = CryptParameterDecryption(s_sessionHandles[s_decryptSessionIndex],
					      &s_nonceCaller[s_decryptSessionIndex].b,
					      command->parameterSize, (UINT16)size,
					      &extraKey,
					      command->parameterBuffer);
	    if(result != TPM_RC_SUCCESS)
		return RcSafeAddToResult(result,
					 TPM_RC_S + g_rcIndex[s_decryptSessionIndex]);
	}
    return TPM_RC_SUCCESS;
}
/* 6.4.4.17 CheckAuthNoSession() */
/* Function to process a command with no session associated. The function makes sure all the handles
   in the command require no authorization. */
/* Error Returns Meaning */
/* TPM_RC_AUTH_MISSING failure - one or more handles require authorization */
TPM_RC
CheckAuthNoSession(
		   COMMAND         *command        // IN: command parsing structure
		   )
{
    UINT32 i;
    TPM_RC           result = TPM_RC_SUCCESS;
    // Check if the command requires authorization
    for(i = 0; i < command->handleNum; i++)
	{
	    if(CommandAuthRole(command->index, i) != AUTH_NONE)
		return TPM_RC_AUTH_MISSING;
	}
#ifdef  TPM_CC_GetCommandAuditDigest
    // Check if the command should be audited.
    if(CommandAuditIsRequired(command->index))
	{
	    result = CheckCommandAudit(command);
	    if(result != TPM_RC_SUCCESS)
		return result;
	}
#endif
    // Initialize number of sessions to be 0
    command->sessionNum = 0;
    return TPM_RC_SUCCESS;
}
/* 6.4.5 Response Session Processing */
/* 6.4.5.1 Introduction */
/* The following functions build the session area in a response, and handle the audit sessions (if
   present). */
/* 6.4.5.2 ComputeRpHash() */
/* Function to compute rpHash (Response Parameter Hash). The rpHash is only computed if there is an
   HMAC authorization session and the return code is TPM_RC_SUCCESS. */
static TPM2B_DIGEST *
ComputeRpHash(
	      COMMAND         *command,       // IN: command structure
	      TPM_ALG_ID       hashAlg        // IN: hash algorithm to compute rpHash
	      )
{
    TPM2B_DIGEST    *rpHash = GetRpHashPointer(command, hashAlg);
    HASH_STATE       hashState;
    if(rpHash->t.size == 0)
	{
	    //   rpHash := hash(responseCode || commandCode || parameters)
	    // Initiate hash creation.
	    rpHash->t.size = CryptHashStart(&hashState, hashAlg);
	    // Add hash constituents.
	    CryptDigestUpdateInt(&hashState, sizeof(TPM_RC), TPM_RC_SUCCESS);
	    CryptDigestUpdateInt(&hashState, sizeof(TPM_CC), command->code);
	    CryptDigestUpdate(&hashState, command->parameterSize,
			      command->parameterBuffer);
	    // Complete hash computation.
	    CryptHashEnd2B(&hashState, &rpHash->b);
	}
    return rpHash;
}
/* 6.4.5.3 InitAuditSession() */
/* This function initializes the audit data in an audit session. */
static void
InitAuditSession(
		 SESSION         *session        // session to be initialized
		 )
{
    // Mark session as an audit session.
    session->attributes.isAudit = SET;
    // Audit session can not be bound.
    session->attributes.isBound = CLEAR;
    // Size of the audit log is the size of session hash algorithm digest.
    session->u2.auditDigest.t.size = CryptHashGetDigestSize(session->authHashAlg);
    // Set the original digest value to be 0.
    MemorySet(&session->u2.auditDigest.t.buffer,
	      0,
	      session->u2.auditDigest.t.size);
    return;
}
/* 6.4.5.4 UpdateAuditDigest */
/* Function to update an audit digest */
static void
UpdateAuditDigest(
		  COMMAND         *command,
		  TPMI_ALG_HASH    hashAlg,
		  TPM2B_DIGEST    *digest
		  )
{
    HASH_STATE       hashState;
    TPM2B_DIGEST    *cpHash = GetCpHash(command, hashAlg);
    TPM2B_DIGEST    *rpHash = ComputeRpHash(command, hashAlg);
    //
    pAssert(cpHash != NULL);
    // digestNew :=  hash (digestOld || cpHash || rpHash)
    // Start hash computation.
    digest->t.size = CryptHashStart(&hashState, hashAlg);
    // Add old digest.
    CryptDigestUpdate2B(&hashState, &digest->b);
    // Add cpHash
    CryptDigestUpdate2B(&hashState, &cpHash->b);
    // Add rpHash
    CryptDigestUpdate2B(&hashState, &rpHash->b);
    // Finalize the hash.
    CryptHashEnd2B(&hashState, &digest->b);
}
/* 6.4.5.5 Audit() */
/* This function updates the audit digest in an audit session. */
static void
Audit(
      COMMAND         *command,       // IN: primary control structure
      SESSION         *auditSession   // IN: loaded audit session
      )
{
    UpdateAuditDigest(command, auditSession->authHashAlg,
		      &auditSession->u2.auditDigest);
    return;
}
#ifdef  TPM_CC_GetCommandAuditDigest
/* 6.4.5.6 CommandAudit() */
/* This function updates the command audit digest. */
static void
CommandAudit(
	     COMMAND         *command        // IN:
	     )
{
    // If the digest.size is one, it indicates the special case of changing
    // the audit hash algorithm. For this case, no audit is done on exit.
    // NOTE: When the hash algorithm is changed, g_updateNV is set in order to
    // force an update to the NV on exit so that the change in digest will
    // be recorded. So, it is safe to exit here without setting any flags
    // because the digest change will be written to NV when this code exits.
    if(gr.commandAuditDigest.t.size == 1)
	{
	    gr.commandAuditDigest.t.size = 0;
	    return;
	}
    // If the digest size is zero, need to start a new digest and increment
    // the audit counter.
    if(gr.commandAuditDigest.t.size == 0)
	{
	    gr.commandAuditDigest.t.size = CryptHashGetDigestSize(gp.auditHashAlg);
	    MemorySet(gr.commandAuditDigest.t.buffer,
		      0,
		      gr.commandAuditDigest.t.size);
	    // Bump the counter and save its value to NV.
	    gp.auditCounter++;
	    NV_SYNC_PERSISTENT(auditCounter);
	}
    UpdateAuditDigest(command, gp.auditHashAlg, &gr.commandAuditDigest);
    return;
}
#endif
/* 6.4.5.7 UpdateAuditSessionStatus() */
/* Function to update the internal audit related states of a session. It */
/* a) initializes the session as audit session and sets it to be exclusive if this is the first time
   it is used for audit or audit reset was requested; */
/* b) reports exclusive audit session; */
/* c) extends audit log; and */
/* d) clears exclusive audit session if no audit session found in the command. */
static void
UpdateAuditSessionStatus(
			 COMMAND         *command        // IN: primary control structure
			 )
{
    UINT32           i;
    TPM_HANDLE       auditSession = TPM_RH_UNASSIGNED;
    // Iterate through sessions
    for(i = 0; i < command->sessionNum; i++)
	{
	    SESSION     *session;
	    // PW session do not have a loaded session and can not be an audit
	    // session either.  Skip it.
	    if(s_sessionHandles[i] == TPM_RS_PW)
		continue;
	    session = SessionGet(s_sessionHandles[i]);
	    // If a session is used for audit
	    if(IS_ATTRIBUTE(s_attributes[i], TPMA_SESSION, audit))
		{
		    // An audit session has been found
		    auditSession = s_sessionHandles[i];
		    // If the session has not been an audit session yet, or
		    // the auditSetting bits indicate a reset, initialize it and set
		    // it to be the exclusive session
		    if(session->attributes.isAudit == CLEAR
		       || IS_ATTRIBUTE(s_attributes[i], TPMA_SESSION, auditReset))
			{
			    InitAuditSession(session);
			    g_exclusiveAuditSession = auditSession;
			}
		    else
			{
			    // Check if the audit session is the current exclusive audit
			    // session and, if not, clear previous exclusive audit session.
			    if(g_exclusiveAuditSession != auditSession)
				g_exclusiveAuditSession = TPM_RH_UNASSIGNED;
			}
		    // Report audit session exclusivity.
		    if(g_exclusiveAuditSession == auditSession)
			{
			    SET_ATTRIBUTE(s_attributes[i], TPMA_SESSION, auditExclusive);
			}
		    else
			{
			    CLEAR_ATTRIBUTE(s_attributes[i], TPMA_SESSION, auditExclusive);
			}
		    // Extend audit log.
		    Audit(command, session);
		}
	}
    // If no audit session is found in the command, and the command allows
    // a session then, clear the current exclusive
    // audit session.
    if(auditSession == TPM_RH_UNASSIGNED && IsSessionAllowed(command->index))
	{
	    g_exclusiveAuditSession = TPM_RH_UNASSIGNED;
	}
    return;
}
/* 6.4.5.8 ComputeResponseHMAC() */
/* Function to compute HMAC for authorization session in a response. */
static void
ComputeResponseHMAC(
		    COMMAND         *command,       // IN: command structure
		    UINT32           sessionIndex,  // IN: session index to be processed
		    SESSION         *session,       // IN: loaded session
		    TPM2B_DIGEST    *hmac           // OUT: authHMAC
		    )
{
    TPM2B_TYPE(KEY, (sizeof(AUTH_VALUE) * 2));
    TPM2B_KEY        key;       // HMAC key
    BYTE             marshalBuffer[sizeof(TPMA_SESSION)];
    BYTE            *buffer;
    UINT32           marshalSize;
    HMAC_STATE       hmacState;
    TPM2B_DIGEST    *rpHash = ComputeRpHash(command, session->authHashAlg);
    // Generate HMAC key
    MemoryCopy2B(&key.b, &session->sessionKey.b, sizeof(key.t.buffer));
    // Add the object authValue if required
    if(session->attributes.includeAuth == SET)
	{
	    // Note: includeAuth may be SET for a policy that is used in
	    // UndefineSpaceSpecial(). At this point, the Index has been deleted
	    // so the includeAuth will have no meaning. However, the
	    // s_associatedHandles[] value for the session is now set to TPM_RH_NULL so
	    // this will return the authValue associated with TPM_RH_NULL and that is
	    // and empty buffer.
	    TPM2B_AUTH          authValue;
	    // Get the authValue with trailing zeros removed
	    EntityGetAuthValue(s_associatedHandles[sessionIndex], &authValue);
	    // Add it to the key
	    MemoryConcat2B(&key.b, &authValue.b, sizeof(key.t.buffer));
	}
    // if the HMAC key size is 0, the response HMAC is computed according to the
    // input HMAC
    if(key.t.size == 0
       && s_inputAuthValues[sessionIndex].t.size == 0)
	{
	    hmac->t.size = 0;
	    return;
	}
    // Start HMAC computation.
    hmac->t.size = CryptHmacStart2B(&hmacState, session->authHashAlg, &key.b);
    // Add hash components.
    CryptDigestUpdate2B(&hmacState.hashState, &rpHash->b);
    CryptDigestUpdate2B(&hmacState.hashState, &session->nonceTPM.b);
    CryptDigestUpdate2B(&hmacState.hashState, &s_nonceCaller[sessionIndex].b);
    // Add session attributes.
    buffer = marshalBuffer;
    marshalSize = TPMA_SESSION_Marshal(&s_attributes[sessionIndex], &buffer, NULL);
    CryptDigestUpdate(&hmacState.hashState, marshalSize, marshalBuffer);
    // Finalize HMAC.
    CryptHmacEnd2B(&hmacState, &hmac->b);
    return;
}
/* 6.4.5.9 UpdateInternalSession() */
/* Updates internal sessions: */
/* a) Restarts session time. */
/* b) Clears a policy session since nonce is rolling. */
static void
UpdateInternalSession(
		      SESSION         *session,       // IN: the session structure
		      UINT32           i              // IN: session number
		      )
{
    // If nonce is rolling in a policy session, the policy related data
    // will be re-initialized.
    if(HandleGetType(s_sessionHandles[i]) == TPM_HT_POLICY_SESSION
       && IS_ATTRIBUTE(s_attributes[i], TPMA_SESSION, continueSession))
	{
	    // When the nonce rolls it starts a new timing interval for the
	    // policy session.
	    SessionResetPolicyData(session);
	    SessionSetStartTime(session);
	}
    return;
}
/* 6.4.5.10 BuildSingleResponseAuth() */
/* Function to compute response HMAC value for a policy or HMAC session. */
static TPM2B_NONCE *
BuildSingleResponseAuth(
			COMMAND         *command,       // IN: command structure
			UINT32           sessionIndex,  // IN: session index to be processed
			TPM2B_AUTH      *auth           // OUT: authHMAC
			)
{
    // Fill in policy/HMAC based session response.
    SESSION     *session = SessionGet(s_sessionHandles[sessionIndex]);
    // If the session is a policy session with isPasswordNeeded SET, the
    // authorization field is empty.
    if(HandleGetType(s_sessionHandles[sessionIndex]) == TPM_HT_POLICY_SESSION
       && session->attributes.isPasswordNeeded == SET)
	auth->t.size = 0;
    else
	// Compute response HMAC.
	ComputeResponseHMAC(command, sessionIndex, session, auth);
    UpdateInternalSession(session, sessionIndex);
    return &session->nonceTPM;
}
/* 6.4.5.11 UpdateAllNonceTPM() */
/* Updates TPM nonce for all sessions in command. */
static void
UpdateAllNonceTPM(
		  COMMAND         *command        // IN: controlling structure
		  )
{
    UINT32      i;
    SESSION     *session;
    for(i = 0; i < command->sessionNum; i++)
	{
	    // If not a PW session, compute the new nonceTPM.
	    if(s_sessionHandles[i] != TPM_RS_PW)
		{
		    session = SessionGet(s_sessionHandles[i]);
		    // Update nonceTPM in both internal session and response.
		    CryptRandomGenerate(session->nonceTPM.t.size,
					session->nonceTPM.t.buffer);
		}
	}
    return;
}
/* 6.4.5.12 BuildResponseSession() */
/* Function to build Session buffer in a response. The authorization data is added to the end of
   command->responseBuffer. The size of the authorization area is accumulated in
   command->authSize. When this is called, command->responseBuffer is pointing at the next location
   in the response buffer to be filled. This is where the authorization sessions will go, if
   any. command->parameterSize is the number of bytes that have been marshaled as parameters in the
   output buffer. */
void
BuildResponseSession(
		     COMMAND         *command        // IN: structure that has relevant command
		     //     information
		     )
{
    pAssert(command->authSize == 0);
    // Reset the parameter buffer to point to the start of the parameters so that
    // there is a starting point for any rpHash that might be generated and so there
    // is a place where parameter encryption would start
    command->parameterBuffer = command->responseBuffer - command->parameterSize;
    // Session nonces should be updated before parameter encryption
    if(command->tag == TPM_ST_SESSIONS)
	{
	    UpdateAllNonceTPM(command);
	    // Encrypt first parameter if applicable. Parameter encryption should
	    // happen after nonce update and before any rpHash is computed.
	    // If the encrypt session is associated with a handle, the authValue of
	    // this handle will be concatenated with sessionKey to generate
	    // encryption key, no matter if the handle is the session bound entity
	    // or not. The authValue is added to sessionKey only when the authValue
	    // is available.
	    if(s_encryptSessionIndex != UNDEFINED_INDEX)
		{
		    UINT32          size;
		    TPM2B_AUTH      extraKey;
		    extraKey.b.size = 0;
		    // If this is an authorization session, include the authValue in the
		    // generation of the encryption key
		    if(s_associatedHandles[s_encryptSessionIndex] != TPM_RH_UNASSIGNED)
			{
			    EntityGetAuthValue(s_associatedHandles[s_encryptSessionIndex],
					       &extraKey);
			}
		    size = EncryptSize(command->index);
		    CryptParameterEncryption(s_sessionHandles[s_encryptSessionIndex],
					     &s_nonceCaller[s_encryptSessionIndex].b,
					     (UINT16)size,
					     &extraKey,
					     command->parameterBuffer);
		}
	}
    // Audit sessions should be processed regardless of the tag because
    // a command with no session may cause a change of the exclusivity state.
    UpdateAuditSessionStatus(command);
#ifdef TPM_CC_GetCommandAuditDigest
    // Command Audit
    if(CommandAuditIsRequired(command->index))
	CommandAudit(command);
#endif
    // Process command with sessions.
    if(command->tag == TPM_ST_SESSIONS)
	{
	    UINT32           i;
	    pAssert(command->sessionNum > 0);
	    // Iterate over each session in the command session area, and create
	    // corresponding sessions for response.
	    for(i = 0; i < command->sessionNum; i++)
		{
		    TPM2B_NONCE     *nonceTPM;
		    TPM2B_DIGEST     responseAuth;
		    // Make sure that continueSession is SET on any Password session.
		    // This makes it marginally easier for the management software
		    // to keep track of the closed sessions.
		    if(s_sessionHandles[i] == TPM_RS_PW)
			{
			    SET_ATTRIBUTE(s_attributes[i], TPMA_SESSION, continueSession);
			    responseAuth.t.size = 0;
			    nonceTPM = (TPM2B_NONCE *)&responseAuth;
			}
		    else
			{
			    // Compute the response HMAC and get a pointer to the nonce used.
			    // This function will also update the values if needed. Note, the
			    nonceTPM = BuildSingleResponseAuth(command, i, &responseAuth);
			}
		    command->authSize += TPM2B_NONCE_Marshal(nonceTPM,
							     &command->responseBuffer,
							     NULL);
		    command->authSize += TPMA_SESSION_Marshal(&s_attributes[i],
							      &command->responseBuffer,
							      NULL);
		    command->authSize += TPM2B_DIGEST_Marshal(&responseAuth,
							      &command->responseBuffer,
							      NULL);
		    if(!IS_ATTRIBUTE(s_attributes[i], TPMA_SESSION, continueSession))
			SessionFlush(s_sessionHandles[i]);
		}
	}
    return;
}
/* 6.4.5.13 SessionRemoveAssociationToHandle() */
/* This function deals with the case where an entity associated with an authorization is deleted
   during command processing. The primary use of this is to support UndefineSpaceSpecial(). */
void
SessionRemoveAssociationToHandle(
				 TPM_HANDLE       handle
				 )
{
    UINT32               i;
    for(i = 0; i < MAX_SESSION_NUM; i++)
	{
	    if(s_associatedHandles[i] == handle)
		{
		    s_associatedHandles[i] = TPM_RH_NULL;
		}
	}
}
