Allow golang client to be used with go 1.18

Make some small tweaks to allow the DPE client to be used with go 1.18.

In particular, go 1.18 does not allow constructing an array from a
slice. The copy must be done manually.

Additionally, fix an issue where a Digest is constructed before the
length is verified, which may panic.

verification/client/abi.go

@@ -525,14 +525,19 @@ func (c *DPEABI[_, _]) GetProfile() (*GetProfileResp, error) {
 }
 
 func (c *DPEABI[_, Digest]) CertifyKey(handle *ContextHandle, label []byte, format CertifyKeyFormat, flags CertifyKeyFlags) (*CertifiedKey, error) {
-	if len(label) != len(Digest(label)) {
+	if len(label) != DigestLen[Digest]() {
 		return nil, fmt.Errorf("invalid label length")
 	}
 
+	l, err := NewDigest[Digest](label)
+	if err != nil {
+		return nil, err
+	}
+
 	cmd := CertifyKeyReq[Digest]{
 		ContextHandle: *handle,
 		Flags:         flags,
-		Label:         Digest(label),
+		Label:         l,
 		Format:        format,
 	}
 
@@ -572,13 +577,18 @@ func (c *DPEABI[_, _]) GetCertificateChain() ([]byte, error) {
 }
 
 func (c *DPEABI[_, Digest]) DeriveChild(handle *ContextHandle, inputData []byte, flags DeriveChildFlags, tciType uint32, targetLocality uint32) (*DeriveChildResp, error) {
-	if len(inputData) != len(Digest(inputData)) {
+	if len(inputData) != DigestLen[Digest]() {
 		return nil, fmt.Errorf("invalid digest length")
 	}
 
+	input, err := NewDigest[Digest](inputData)
+	if err != nil {
+		return nil, err
+	}
+
 	cmd := DeriveChildReq[Digest]{
 		ContextHandle:  *handle,
-		InputData:      Digest(inputData),
+		InputData:      input,
 		Flags:          flags,
 		TciType:        tciType,
 		TargetLocality: targetLocality,
@@ -604,19 +614,30 @@ func (c *DPEABI[_, _]) RotateContextHandle(handle *ContextHandle, flags RotateCo
 }
 
 func (c *DPEABI[_, Digest]) Sign(handle *ContextHandle, label []byte, flags SignFlags, toBeSigned []byte) (*DPESignedHash, error) {
-	if len(label) != len(Digest(label)) {
+	dLen := DigestLen[Digest]()
+	if len(label) != dLen {
 		return nil, fmt.Errorf("invalid label length")
 	}
 
-	if len(toBeSigned) != len(Digest(toBeSigned)) {
+	if len(toBeSigned) != dLen {
 		return nil, fmt.Errorf("invalid toBeSigned length")
 	}
 
+	l, err := NewDigest[Digest](label)
+	if err != nil {
+		return nil, err
+	}
+
+	tbs, err := NewDigest[Digest](toBeSigned)
+	if err != nil {
+		return nil, err
+	}
+
 	cmd := SignReq[Digest]{
 		ContextHandle: *handle,
-		Label:         Digest(label),
+		Label:         l,
 		Flags:         flags,
-		ToBeSigned:    Digest(toBeSigned),
+		ToBeSigned:    tbs,
 	}
 	resp, err := c.SignABI(&cmd)
 	if err != nil {
@@ -634,13 +655,18 @@ func (c *DPEABI[_, Digest]) Sign(handle *ContextHandle, label []byte, flags Sign
 
 func (c *DPEABI[_, Digest]) ExtendTCI(handle *ContextHandle, inputData []byte) (*ContextHandle, error) {
 
-	if len(inputData) != len(Digest(inputData)) {
+	if len(inputData) != DigestLen[Digest]() {
 		return nil, fmt.Errorf("invalid digest length")
 	}
 
+	input, err := NewDigest[Digest](inputData)
+	if err != nil {
+		return nil, err
+	}
+
 	cmd := ExtendTCIReq[Digest]{
 		ContextHandle: *handle,
-		InputData:     Digest(inputData),
+		InputData:     input,
 	}
 
 	resp, err := c.ExtendTCIABI(&cmd)

verification/client/go.mod

@@ -1,3 +1,3 @@
 module github.com/chipsalliance/caliptra-dpe/verification/client
 
-go 1.20
+go 1.18

verification/client/profile.go

@@ -2,7 +2,10 @@
 
 package client
 
-import "fmt"
+import (
+	"fmt"
+	"reflect"
+)
 
 // Profile represents a supported algorithm profile (i.e., hash algorithm and ECC curve).
 type Profile uint32
@@ -53,6 +56,10 @@ type Curve interface {
 	Bytes() []byte
 }
 
+func CurveIntLen[C Curve]() int {
+	return reflect.TypeOf((*C)(nil)).Elem().Len()
+}
+
 // NISTP256Parameter represents a NIST P-256 curve parameter, i.e., an x, y, r, or s value.
 type NISTP256Parameter [32]byte
 
@@ -76,6 +83,24 @@ type DigestAlgorithm interface {
 	Bytes() []byte
 }
 
+func NewDigest[D DigestAlgorithm](b []byte) (D, error) {
+	var d D
+	switch tmp := any(&d).(type) {
+	case *SHA256Digest:
+		copy(tmp[:], b[:])
+	case *SHA384Digest:
+		copy(tmp[:], b[:])
+	default:
+		return d, fmt.Errorf("Invalid digest type %v", reflect.TypeOf(tmp))
+	}
+
+	return d, nil
+}
+
+func DigestLen[D DigestAlgorithm]() int {
+	return reflect.TypeOf((*D)(nil)).Elem().Len()
+}
+
 // SHA256Digest represents a SHA-256 digest value.
 type SHA256Digest [32]byte