adds ability to create keys from crypto.PrivateKey types

.gitignore

@@ -0,0 +1 @@
+*.swp

crypto/key.go

@@ -4,9 +4,12 @@
 package crypto
 
 import (
+	"crypto"
+	"crypto/ecdsa"
 	"crypto/elliptic"
 	"crypto/hmac"
 	"crypto/rand"
+	"crypto/rsa"
 	"crypto/sha1"
 	"crypto/sha512"
 	"crypto/subtle"
@@ -15,11 +18,14 @@ import (
 	"fmt"
 	"hash"
 	"io"
+	"log"
 
 	pb "github.com/libp2p/go-libp2p-core/crypto/pb"
 
+	btcec "github.com/btcsuite/btcd/btcec"
 	"github.com/gogo/protobuf/proto"
 	sha256 "github.com/minio/sha256-simd"
+	"golang.org/x/crypto/ed25519"
 )
 
 const (
@@ -174,6 +180,42 @@ func GenerateEKeyPair(curveName string) ([]byte, GenSharedKey, error) {
 	return pubKey, done, nil
 }
 
+// KeyPairFromKey generates a new private and public key from an input private key
+func KeyPairFromKey(priv crypto.PrivateKey) (PrivKey, PubKey, error) {
+	if priv == nil {
+		return nil, nil, ErrNilPrivateKey
+	}
+
+	switch priv.(type) {
+	case *rsa.PrivateKey:
+		log.Println("1")
+		rPriv, _ := priv.(*rsa.PrivateKey)
+		return &RsaPrivateKey{*rPriv}, &RsaPublicKey{rPriv.PublicKey}, nil
+
+	case *ecdsa.PrivateKey:
+		log.Println("2")
+		ePriv, _ := priv.(*ecdsa.PrivateKey)
+		return &ECDSAPrivateKey{ePriv}, &ECDSAPublicKey{&ePriv.PublicKey}, nil
+
+	case *ed25519.PrivateKey:
+		log.Println("3")
+		ePriv, _ := priv.(*ed25519.PrivateKey)
+		pubIfc := ePriv.Public()
+		pub, _ := pubIfc.(ed25519.PublicKey)
+		return &Ed25519PrivateKey{*ePriv}, &Ed25519PublicKey{pub}, nil
+
+	case *btcec.PrivateKey:
+		log.Println("4")
+		bPriv, _ := priv.(*btcec.PrivateKey)
+		sPriv := Secp256k1PrivateKey(*bPriv)
+		sPub := Secp256k1PublicKey(*bPriv.PubKey())
+		return &sPriv, &sPub, nil
+
+	default:
+		return nil, nil, ErrBadKeyType
+	}
+}
+
 // StretchedKeys ...
 type StretchedKeys struct {
 	IV        []byte

crypto/key_test.go

@@ -2,12 +2,20 @@ package crypto_test
 
 import (
 	"bytes"
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/elliptic"
 	"crypto/rand"
+	"crypto/rsa"
+	"fmt"
 	"testing"
 
+	btcec "github.com/btcsuite/btcd/btcec"
 	. "github.com/libp2p/go-libp2p-core/crypto"
 	pb "github.com/libp2p/go-libp2p-core/crypto/pb"
 	"github.com/libp2p/go-libp2p-core/test"
+	sha256 "github.com/minio/sha256-simd"
+	"golang.org/x/crypto/ed25519"
 )
 
 func TestKeys(t *testing.T) {
@@ -16,6 +24,97 @@ func TestKeys(t *testing.T) {
 	}
 }
 
+func TestKeyPairFromKey(t *testing.T) {
+	var (
+		data   = []byte(`hello world`)
+		hashed = sha256.Sum256(data)
+	)
+
+	privk, err := btcec.NewPrivateKey(btcec.S256())
+	if err != nil {
+		t.Fatalf("err generating btcec priv key:\n%v", err)
+	}
+	sigK, err := privk.Sign(hashed[:])
+	if err != nil {
+		t.Fatalf("err generating btcec sig:\n%v", err)
+	}
+
+	eKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatalf("err generating ecdsa priv key:\n%v", err)
+	}
+	sigE, err := eKey.Sign(rand.Reader, hashed[:], crypto.SHA256)
+	if err != nil {
+		t.Fatalf("err generating ecdsa sig:\n%v", err)
+	}
+
+	rKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		t.Fatalf("err generating rsa priv key:\n%v", err)
+	}
+	sigR, err := rKey.Sign(rand.Reader, hashed[:], crypto.SHA256)
+	if err != nil {
+		t.Fatalf("err generating rsa sig:\n%v", err)
+	}
+
+	_, edKey, err := ed25519.GenerateKey(rand.Reader)
+	sigEd := ed25519.Sign(edKey, data[:])
+	if err != nil {
+		t.Fatalf("err generating ed25519 sig:\n%v", err)
+	}
+
+	for i, tt := range []struct {
+		in  crypto.PrivateKey
+		typ pb.KeyType
+		sig []byte
+	}{
+		{
+			eKey,
+			ECDSA,
+			sigE,
+		},
+		{
+			privk,
+			Secp256k1,
+			sigK.Serialize(),
+		},
+		{
+			rKey,
+			RSA,
+			sigR,
+		},
+		{
+			&edKey,
+			Ed25519,
+			sigEd,
+		},
+	} {
+		t.Run(fmt.Sprintf("%v", i), func(t *testing.T) {
+			priv, pub, err := KeyPairFromKey(tt.in)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if priv == nil || pub == nil {
+				t.Errorf("received nil private key or public key: %v, %v", priv, pub)
+			}
+
+			if priv == nil || priv.Type() != tt.typ {
+				t.Errorf("want %v; got %v", tt.typ, priv.Type())
+			}
+
+			v, err := pub.Verify(data[:], tt.sig)
+			if err != nil {
+				t.Error(err)
+			}
+
+			if !v {
+				t.Error("signature was not verified")
+			}
+		})
+	}
+}
+
 func testKeyType(typ int, t *testing.T) {
 	bits := 512
 	if typ == RSA {