Add secrets interface to config/secrets (#1325)

* Interface for secrets

* Add secretbox secrets implementation

* Start working on box

* typo

* Add asymmetric encryption implementation

* go mod tidy

* Fix review comments

Co-authored-by: Asim Aslam <asim@aslam.me>

config/secrets/box/box_test.go

@@ -0,0 +1,63 @@
+package box
+
+import (
+	"crypto/rand"
+	"reflect"
+	"testing"
+
+	"github.com/micro/go-micro/v2/config/secrets"
+	naclbox "golang.org/x/crypto/nacl/box"
+)
+
+func TestBox(t *testing.T) {
+	alicePublicKey, alicePrivateKey, err := naclbox.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	bobPublicKey, bobPrivateKey, err := naclbox.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	alice, bob := NewCodec(secrets.PublicKey(alicePublicKey[:]), secrets.PrivateKey(alicePrivateKey[:])), NewCodec()
+	if err := alice.Init(); err != nil {
+		t.Error(err)
+	}
+	if err := bob.Init(secrets.PublicKey(bobPublicKey[:]), secrets.PrivateKey(bobPrivateKey[:])); err != nil {
+		t.Error(err)
+	}
+	if alice.String() != "nacl-box" {
+		t.Error("String() doesn't return nacl-box")
+	}
+	aliceSecret := []byte("Why is a raven like a writing-desk?")
+	if _, err := alice.Encrypt(aliceSecret); err == nil {
+		t.Error("alice.Encrypt succeded without a public key")
+	}
+	enc, err := alice.Encrypt(aliceSecret, secrets.RecipientPublicKey(bob.Options().PublicKey))
+	if err != nil {
+		t.Error("alice.Encrypt failed")
+	}
+	if _, err := bob.Decrypt(enc); err == nil {
+		t.Error("bob.Decrypt succeded without a public key")
+	}
+	if dec, err := bob.Decrypt(enc, secrets.SenderPublicKey(alice.Options().PublicKey)); err == nil {
+		if !reflect.DeepEqual(dec, aliceSecret) {
+			t.Errorf("Bob's decrypted message didn't match Alice's encrypted message: %v != %v", aliceSecret, dec)
+		}
+	} else {
+		t.Errorf("bob.Decrypt failed (%s)", err)
+	}
+
+	bobSecret := []byte("I haven't the slightest idea")
+	enc, err = bob.Encrypt(bobSecret, secrets.RecipientPublicKey(alice.Options().PublicKey))
+	if err != nil {
+		t.Error(err)
+	}
+	dec, err := alice.Decrypt(enc, secrets.SenderPublicKey(bob.Options().PrivateKey))
+	if err == nil {
+		t.Error(err)
+	}
+	dec, err = alice.Decrypt(enc, secrets.SenderPublicKey(bob.Options().PublicKey))
+	if !reflect.DeepEqual(dec, bobSecret) {
+		t.Errorf("Alice's decrypted message didn't match Bob's encrypted message %v != %v", bobSecret, dec)
+	}
+}