Adding comments to TestReadPublicKey

direct/tpm2/read_public_test.go

@@ -13,14 +13,21 @@ import (
 	"github.com/google/go-tpm/direct/transport/simulator"
 )
 
+// TestReadPublicKey compares the CreatePrimary reponse parameter outPublic with the output of ReadPublic outPublic.
 func TestReadPublicKey(t *testing.T) {
-
+	// Open simulated TPM for testing.
 	thetpm, err := simulator.OpenSimulator()
 	if err != nil {
 		t.Fatalf("could not connect to TPM simulator: %v", err)
 	}
+
+	// Defer the close of the simulated TPM to after use.
+	// Without this, other programs/tests may not be able to get a handle to the TPM.
 	defer thetpm.Close()
 
+	// Fill in the CreatePrimary struct.
+	// See definition in Part 3, Commands, section 24.1.
+	// See direct/templates/templates.go for more tpmt.Public examples.
 	createPrimary := CreatePrimary{
 		PrimaryHandle: tpm.RHOwner,
 		InPublic: tpm2b.Public{
@@ -51,26 +58,44 @@ func TestReadPublicKey(t *testing.T) {
 		},
 	}
 
+	// Executing the command uses reflection to pack the bytes into a
+	// TPM2_CreatePrimary command, returns a TPM2_CreatePrimary Response.
+	// This response is also decoded so you are again working with structs
+	// that can be found in Part 3, Commands, section 24.1.
 	rspCP, err := createPrimary.Execute(thetpm)
 	if err != nil {
 		t.Fatalf("CreatePrimary failed: %v", err)
 	}
 
+	// The TPM can only hold so much in nonvolatile memory, thus we must
+	// flush the handle after we are done using it to prevent overloading.
+	// Again we defer the flush to after we are done using the object.
+	// It is generally good practice to defer the cleanup immediately
+	// after loading an object or creating an Authorization Session.
+	// See Part 1, Architecture, section 30.4
 	flushContext := FlushContext{FlushHandle: rspCP.ObjectHandle}
 	defer flushContext.Execute(thetpm)
 
+	// Fill in the ReadPublic struct.
+	// See definition in Part 3, Commands, section 12.4.
 	readPublic := ReadPublic{
 		ObjectHandle: rspCP.ObjectHandle,
 	}
 
+	// Executing the command uses reflection to pack the bytes into a
+	// TPM2_ReadPublic command, returns a TPM2_ReadPublic Response.
+	// This response is also decoded so you are again working with structs
+	// that can be found in Part 3, Commands, section 12.4.
 	rspRP, err := readPublic.Execute(thetpm)
 	if err != nil {
 		t.Fatalf("ReadPublic failed: %v", err)
 	}
 
+	// PublicArea.Unique represents the unique identifier of the TPMT.Public.
+	// Notice how this test uses verification of another TPM command that is
+	// able to produce similar results to validate the response.
 	rspCPUnique := rspCP.OutPublic.PublicArea.Unique
 	rspRPUnique := rspRP.OutPublic.PublicArea.Unique
-
 	if !cmp.Equal(rspCPUnique, rspRPUnique) {
 		t.Error("Mismatch between public returned from CreatePrimary & ReadPublic")
 	}