feat(eddsa): add support for EdDSA varsigs - and common Ed25519 and Ed448 algorithms

eddsa.go

@@ -0,0 +1,116 @@
+package varsig
+
+import (
+	"bytes"
+	"crypto/ed25519"
+	"encoding/binary"
+
+	"github.com/multiformats/go-multicodec"
+)
+
+const (
+	SignAlgorithmEdDSA   = SignAlgorithm(multicodec.Ed25519Pub)
+	SignAlgorithmEd25519 = SignAlgorithm(multicodec.Ed25519Pub)
+	SignAlgorithmEd448   = SignAlgorithm(multicodec.Ed448Pub)
+)
+
+type EdDSACurve uint64
+
+const (
+	CurveEd25519 = EdDSACurve(multicodec.Ed25519Pub)
+	CurveEd448   = EdDSACurve(multicodec.Ed448Pub)
+)
+
+var _ Varsig = (*EdDSAVarsig)(nil)
+
+type EdDSAVarsig struct {
+	varsig[EdDSAVarsig]
+
+	curve   EdDSACurve
+	hashAlg HashAlgorithm
+}
+
+func NewEdDSAVarsig(curve EdDSACurve, hashAlgorithm HashAlgorithm, payloadEncoding PayloadEncoding, opts ...Option) (*EdDSAVarsig, error) {
+	options := newOptions(opts...)
+
+	var (
+		vers    = Version1
+		signAlg = SignAlgorithmEdDSA
+		sig     = []byte{}
+	)
+
+	if options.ForceVersion0() {
+		vers = Version0
+		signAlg = SignAlgorithm(curve)
+		sig = options.Signature()
+	}
+
+	v := &EdDSAVarsig{
+		varsig: varsig[EdDSAVarsig]{
+			vers:    vers,
+			signAlg: signAlg,
+			payEnc:  payloadEncoding,
+			sig:     sig,
+		},
+		curve:   curve,
+		hashAlg: hashAlgorithm,
+	}
+
+	return v.validateSig(v, ed25519.PrivateKeySize)
+}
+
+func (v *EdDSAVarsig) Curve() EdDSACurve {
+	return v.curve
+}
+
+func (v *EdDSAVarsig) HashAlgorithm() HashAlgorithm {
+	return v.hashAlg
+}
+
+func (v EdDSAVarsig) Encode() []byte {
+	buf := v.encode()
+
+	if v.vers != Version0 {
+		buf = binary.AppendUvarint(buf, uint64(v.curve))
+	}
+
+	buf = binary.AppendUvarint(buf, uint64(v.hashAlg))
+	buf = binary.AppendUvarint(buf, uint64(v.payEnc))
+	buf = append(buf, v.Signature()...)
+
+	return buf
+}
+
+func decodeEd25519(r *bytes.Reader, vers Version, signAlg SignAlgorithm) (Varsig, error) {
+	curve := uint64(signAlg)
+	if vers != Version0 {
+		u, err := binary.ReadUvarint(r)
+
+		if err != nil {
+			return nil, err // TODO: wrap error?
+		}
+
+		curve = u
+	}
+
+	hashAlg, err := binary.ReadUvarint(r)
+	if err != nil {
+		return nil, err // TODO: wrap error?
+	}
+
+	v := &EdDSAVarsig{
+		varsig: varsig[EdDSAVarsig]{
+			vers:    vers,
+			signAlg: signAlg,
+		},
+		curve:   EdDSACurve(curve),
+		hashAlg: HashAlgorithm(hashAlg),
+	}
+
+	return v.decodePayEncAndSig(r, v, ed25519.PrivateKeySize)
+}
+
+// TODO: remove this when parseEd25519 is added to the DefaultRegistry.
+func Junk() {
+	_, _ = decodeEd25519(nil, 0, 0)
+}