From d837630ff6b7d1592d9e4095d6ae7877205be394 Mon Sep 17 00:00:00 2001
From: Keith Petkus <keith@keithp.net>
Date: Fri, 7 May 2021 12:27:53 -0400
Subject: [PATCH] remove libsodium dependency in favor of the native go/crypto
 ed25519 library

---
 CONTRIBUTING.md            |  1 -
 lib/common/fuzz/Dockerfile |  3 +-
 lib/crypto/ed25519.go      | 79 ++++++++++++--------------------------
 lib/crypto/ed25519_test.go | 33 ++++++++++++++++
 4 files changed, 59 insertions(+), 57 deletions(-)

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 23b96b6..6dec5c7 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -9,7 +9,6 @@ Install required dependencies
 This example assumes Ubuntu 16.04
 
 ```sh
-sudo apt-get install pkg-config libsodium-dev
 go get github.com/hkparker/go-i2p
 go get github.com/Sirupsen/logrus
 go get github.com/stretchr/testify/assert
diff --git a/lib/common/fuzz/Dockerfile b/lib/common/fuzz/Dockerfile
index 12bc288..284cedc 100644
--- a/lib/common/fuzz/Dockerfile
+++ b/lib/common/fuzz/Dockerfile
@@ -1,8 +1,7 @@
 FROM golang
 
 RUN apt-get update && \
-    apt-get upgrade -y && \
-    apt-get install libsodium-dev -y
+    apt-get upgrade -y
 
 RUN go get github.com/dvyukov/go-fuzz/go-fuzz
 RUN go get github.com/dvyukov/go-fuzz/go-fuzz-build
diff --git a/lib/crypto/ed25519.go b/lib/crypto/ed25519.go
index 040a10c..3a2db82 100644
--- a/lib/crypto/ed25519.go
+++ b/lib/crypto/ed25519.go
@@ -1,54 +1,37 @@
 package crypto
 
-/*
-#cgo pkg-config: libsodium
-#include <sodium.h>
-#include <stdint.h>
-*/
-import "C"
-
 import (
+	"crypto/ed25519"
 	"crypto/sha512"
 	"errors"
-	"fmt"
 )
 
-type Ed25519PublicKey [32]byte
+type Ed25519PublicKey []byte
 
 type Ed25519Verifier struct {
-	k [32]C.uchar
+	k []byte
 }
 
 func (k Ed25519PublicKey) NewVerifier() (v Verifier, err error) {
-	ev := new(Ed25519Verifier)
-	for i, b := range k {
-		ev.k[i] = C.uchar(b)
-	}
-	v = ev
-	return
+	temp := new(Ed25519Verifier)
+	temp.k = k
+	v = temp
+	return temp, nil
 }
 
 func (v *Ed25519Verifier) VerifyHash(h, sig []byte) (err error) {
-	if len(sig) == C.crypto_sign_BYTES {
-		// valid size of sig
-		// copy signature and hash
-		var csig, ch [32]C.uchar
-		for i, b := range h {
-			ch[i] = C.uchar(b)
-		}
-		for i, b := range sig {
-			csig[i] = C.uchar(b)
-		}
-		// verify
-		if C.crypto_sign_verify_detached(&csig[0], &ch[0], C.ulonglong(32), &v.k[0]) == 0 {
-			// valid signature
-		} else {
-			// bad signature
-			err = ErrInvalidSignature
-		}
-	} else {
-		// bad size of sig
+	if len(sig) != ed25519.SignatureSize {
 		err = ErrBadSignatureSize
+		return
+	}
+	if len(v.k) != ed25519.PublicKeySize {
+		err = errors.New("failed to verify: invalid ed25519 public key size")
+		return
+	}
+
+	ok := ed25519.Verify(v.k, h, sig)
+	if !ok {
+		err = errors.New("failed to verify: invalid signature")
 	}
 	return
 }
@@ -59,35 +42,23 @@ func (v *Ed25519Verifier) Verify(data, sig []byte) (err error) {
 	return
 }
 
-type Ed25519PrivateKey [32]byte
+type Ed25519PrivateKey ed25519.PrivateKey
 
 type Ed25519Signer struct {
-	k [32]C.uchar
+	k []byte
 }
 
 func (s *Ed25519Signer) Sign(data []byte) (sig []byte, err error) {
+	if len(s.k) != ed25519.PrivateKeySize {
+		err = errors.New("failed to sign: invalid ed25519 private key size")
+		return
+	}
 	h := sha512.Sum512(data)
 	sig, err = s.SignHash(h[:])
 	return
 }
 
 func (s *Ed25519Signer) SignHash(h []byte) (sig []byte, err error) {
-	var ch [32]C.uchar
-	for i, b := range h {
-		ch[i] = C.uchar(b)
-	}
-	var csig [32]C.uchar
-	var smlen_p C.ulonglong
-	res := C.crypto_sign_detached(&csig[0], &smlen_p, &ch[0], C.ulonglong(32), &s.k[0])
-	if res == 0 {
-		// success signing
-		sig = make([]byte, 32)
-		for i, b := range csig {
-			sig[i] = byte(b)
-		}
-	} else {
-		// failed signing
-		err = errors.New(fmt.Sprintf("failed to sign: crypto_sign_detached exit code %d", int(res)))
-	}
+	sig = ed25519.Sign(s.k, h)
 	return
 }
diff --git a/lib/crypto/ed25519_test.go b/lib/crypto/ed25519_test.go
index e746c7a..c6507b9 100644
--- a/lib/crypto/ed25519_test.go
+++ b/lib/crypto/ed25519_test.go
@@ -1,9 +1,42 @@
 package crypto
 
 import (
+	"crypto/ed25519"
+	"crypto/rand"
+	"io"
 	"testing"
 )
 
 func TestEd25519(t *testing.T) {
+	var pubKey Ed25519PublicKey
 
+	signer := new(Ed25519Signer)
+	pub, priv, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Log("Failed to generate ed25519 test key")
+		t.Fail()
+	}
+	pubKey = []byte(pub)
+	signer.k = []byte(priv)
+
+	message := make([]byte, 123)
+	io.ReadFull(rand.Reader, message)
+
+	sig, err := signer.Sign(message)
+	if err != nil {
+		t.Log("Failed to sign message")
+		t.Fail()
+	}
+
+	verifier, err := pubKey.NewVerifier()
+	if err != nil {
+		t.Logf("Error from verifier: %s", err)
+		t.Fail()
+	}
+
+	err = verifier.Verify(message, sig)
+	if err != nil {
+		t.Log("Failed to verify message")
+		t.Fail()
+	}
 }