diff --git a/src/tpm2.c b/src/tpm2.c
index d8f81004..423c90d6 100644
--- a/src/tpm2.c
+++ b/src/tpm2.c
@@ -108,7 +108,7 @@ static int TPM2_CommandProcess(TPM2_CTX* ctx, TPM2_Packet* packet,
     BYTE *param, *encParam = NULL;
     int paramSz, encParamSz = 0;
     int i, authPos;
-    int tmpSz = 0; /* Used to calculate the new total size of the Auth Area */
+    int authTotalSzPos = 0;
 #ifndef WOLFTPM2_NO_WOLFCRYPT
     UINT32 handleValue1, handleValue2, handleValue3;
     int handlePos;
@@ -120,8 +120,8 @@ static int TPM2_CommandProcess(TPM2_CTX* ctx, TPM2_Packet* packet,
     /* Parse Auth */
     TPM2_Packet_ParseU32(packet, &authSz);
     packet->pos -= sizeof(authSz);
-    /* Later Auth Area size is updated */
-    TPM2_Packet_MarkU32(packet, &tmpSz);
+    /* Get position for total auth size to be updated later */
+    TPM2_Packet_MarkU32(packet, &authTotalSzPos);
     /* Mark the position of the Auth Area data */
     authPos = packet->pos;
     packet->pos += authSz;
@@ -174,11 +174,25 @@ static int TPM2_CommandProcess(TPM2_CTX* ctx, TPM2_Packet* packet,
             }
         }
 
-        /* Note: Copy between TPM2_AUTH_SESSION and TPMS_AUTH_COMMAND is allowed */
-        XMEMCPY(&authCmd, session, sizeof(TPMS_AUTH_COMMAND));
-
-        if (TPM2_IS_HMAC_SESSION(session->sessionHandle) ||
-            TPM2_IS_POLICY_SESSION(session->sessionHandle))
+        /* Build auth */
+        XMEMSET(&authCmd, 0, sizeof(authCmd));
+        authCmd.sessionHandle = session->sessionHandle;
+        authCmd.sessionAttributes = session->sessionAttributes;
+        authCmd.nonce.size = session->nonceCaller.size;
+        XMEMCPY(authCmd.nonce.buffer, session->nonceCaller.buffer,
+            authCmd.nonce.size);
+
+        /* Password Auth */
+        if (session->sessionHandle == TPM_RS_PW) {
+            authCmd.hmac.size = session->auth.size;
+            if (session->auth.size > 0) {
+                XMEMCPY(authCmd.hmac.buffer, session->auth.buffer,
+                    session->auth.size);
+            }
+        }
+        /* HMAC or Policy Session */
+        else if (TPM2_IS_HMAC_SESSION(session->sessionHandle) ||
+                 TPM2_IS_POLICY_SESSION(session->sessionHandle))
         {
         #ifndef WOLFTPM2_NO_WOLFCRYPT
             TPM2B_NAME name1, name2, name3;
@@ -240,14 +254,15 @@ static int TPM2_CommandProcess(TPM2_CTX* ctx, TPM2_Packet* packet,
         #endif /* !WOLFTPM2_NO_WOLFCRYPT && !NO_HMAC */
         }
 
-        /* Replace auth in session */
+        /* Place session auth */
         packet->pos = authPos;
         TPM2_Packet_AppendAuthCmd(packet, &authCmd);
         authPos = packet->pos; /* update auth position */
+        printf("Act auth %d\n", packet->pos);
     }
 
-    /* Update the Auth Area size in the command packet */
-    TPM2_Packet_PlaceU32(packet, tmpSz);
+    /* Update the Auth Area total size in the command packet */
+    TPM2_Packet_PlaceU32(packet, authTotalSzPos);
 
     (void)cmdCode;
     return rc;
diff --git a/src/tpm2_packet.c b/src/tpm2_packet.c
index 6d1f22b4..bfce8e7a 100644
--- a/src/tpm2_packet.c
+++ b/src/tpm2_packet.c
@@ -347,15 +347,51 @@ TPM_ST TPM2_Packet_AppendAuth(TPM2_Packet* packet, TPM2_CTX* ctx, CmdInfo_t* inf
 
     info->authCnt = TPM2_GetCmdAuthCount(ctx, info);
     if (info->authCnt > 0) {
-        int i, tmpSz = 0;
-        TPM2_Packet_MarkU32(packet, &tmpSz);
+        int i, authTotalSzPos = 0;
+        TPM2_Packet_MarkU32(packet, &authTotalSzPos);
         for (i=0; i<info->authCnt; i++) {
-            /* Note: Casting a TPM2_AUTH_SESSION to TPMS_AUTH_COMMAND here,
-             * this is allowed because top of structure matches */
-            TPM2_Packet_AppendAuthCmd(packet, (TPMS_AUTH_COMMAND*)&ctx->session[i]);
+            TPM2_AUTH_SESSION* session = &ctx->session[i];
+
+            /* Determine auth size - appended later in TPM2_CommandProcess */
+
+            /* sessionHandle */
+            packet->pos += sizeof(UINT32);
+
+            /* Nonce size:
+             * Determined by us and TPM matches it on reply
+             * Typically use SHA2-256 digest size (16 bytes). The random nonce
+             * is populated in TPM2_CommandProcess */
+            packet->pos += sizeof(UINT16); /* nonceSz */
+            if (session->sessionHandle != TPM_RS_PW) {
+                session->nonceCaller.size =
+                    TPM2_GetHashDigestSize(WOLFTPM2_WRAP_DIGEST);
+                packet->pos += session->nonceCaller.size;
+            }
+
+            /* sessionAttributes */
+            packet->pos += sizeof(UINT8);
+
+            /* Password Auth */
+            packet->pos += sizeof(UINT16); /* hmac.size */
+            if (session->sessionHandle == TPM_RS_PW) {
+                packet->pos += session->auth.size;
+            }
+            /* HMAC or Policy Session */
+            else if ((session->sessionHandle != TPM_RS_PW &&
+                    ((session->sessionAttributes & TPMA_SESSION_encrypt) ||
+                     (session->sessionAttributes & TPMA_SESSION_decrypt)))
+                || TPM2_IS_POLICY_SESSION(session->sessionHandle))
+            {
+                UINT16 hmacSz = session->auth.size;
+                if (hmacSz == 0) {
+                    /* default is a HMAC output (using alg authHash) */
+                    hmacSz = TPM2_GetHashDigestSize(session->authHash);
+                }
+                packet->pos += hmacSz;
+            }
         }
         /* based on position difference places calculated size at marked U32 above */
-        TPM2_Packet_PlaceU32(packet, tmpSz);
+        TPM2_Packet_PlaceU32(packet, authTotalSzPos);
         st = TPM_ST_SESSIONS;
     }
     return st;
diff --git a/src/tpm2_wrap.c b/src/tpm2_wrap.c
index 9f77e322..3d50680d 100644
--- a/src/tpm2_wrap.c
+++ b/src/tpm2_wrap.c
@@ -1000,24 +1000,11 @@ int wolfTPM2_SetAuthSession(WOLFTPM2_DEV* dev, int index,
         XMEMCPY(&session->symmetric, &tpmSession->handle.symmetric,
             sizeof(TPMT_SYM_DEF));
 
-        /* fresh nonce generated in TPM2_CommandProcess based on this size */
-        session->nonceCaller.size = TPM2_GetHashDigestSize(WOLFTPM2_WRAP_DIGEST);
-
         /* Capture TPM provided nonce */
         session->nonceTPM.size = tpmSession->nonceTPM.size;
         XMEMCPY(session->nonceTPM.buffer, tpmSession->nonceTPM.buffer,
             session->nonceTPM.size);
 
-        /* Parameter Encryption or Policy session will have an HMAC added later.
-         * Reserve space, the same way it was done for nonceCaller above.
-         */
-        if ((session->sessionHandle != TPM_RS_PW &&
-                ((session->sessionAttributes & TPMA_SESSION_encrypt) ||
-                 (session->sessionAttributes & TPMA_SESSION_decrypt)))
-             || TPM2_IS_POLICY_SESSION(session->sessionHandle))
-        {
-            session->auth.size = TPM2_GetHashDigestSize(session->authHash);
-        }
     }
     return rc;
 }
diff --git a/wolftpm/tpm2.h b/wolftpm/tpm2.h
index 8332b253..74dcbc84 100644
--- a/wolftpm/tpm2.h
+++ b/wolftpm/tpm2.h
@@ -1621,13 +1621,11 @@ typedef struct TPMS_AUTH_RESPONSE {
 
 /* Implementation specific authorization session information */
 typedef struct TPM2_AUTH_SESSION {
-    /* BEGIN */
-    /* This section should match TPMS_AUTH_COMMAND */
+    /* this section is used for TPMS_AUTH_COMMAND */
     TPMI_SH_AUTH_SESSION sessionHandle;
     TPM2B_NONCE nonceCaller;
     TPMA_SESSION sessionAttributes;
     TPM2B_AUTH auth;
-    /* END */
 
     /* additional auth data required for implementation */
     TPM2B_NONCE nonceTPM;