From 139a35c219cf1b76ca906e11cd8203402f5641ec Mon Sep 17 00:00:00 2001
From: Sarah Jamie Lewis <sarah@openprivacy.ca>
Date: Mon, 24 Oct 2022 13:00:45 -0700
Subject: [PATCH] Expose token.T in json + fix issue with new auth protocol

---
 primitives/privacypass/token.go | 14 ++++++++++++++
 utils/crypto.go                 | 10 +++++-----
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/primitives/privacypass/token.go b/primitives/privacypass/token.go
index a91db76..ee5abf4 100644
--- a/primitives/privacypass/token.go
+++ b/primitives/privacypass/token.go
@@ -3,6 +3,7 @@ package privacypass
 import (
 	"crypto/hmac"
 	"crypto/rand"
+	"encoding/json"
 	"fmt"
 	"git.openprivacy.ca/cwtch.im/tapir/primitives/core"
 	"git.openprivacy.ca/openprivacy/log"
@@ -122,3 +123,16 @@ func UnblindSignedTokenBatch(tokens []*Token, blindedTokens []BlindedToken, sign
 	}
 	return true
 }
+
+// MarshalJSON - in order to store tokens in a serialized form we need to expose the private, unexported value
+// `t`. Note that `r` is not needed to spend the token, and as such we effectively destroy it when we serialize.
+// Ideally, go would let us do this with an annotation, alas.
+func (t Token) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		T []byte `json:"t"`
+		W *ristretto.Element
+	}{
+		T: t.t,
+		W: t.W,
+	})
+}
diff --git a/utils/crypto.go b/utils/crypto.go
index fd5f0d6..e3cdb6f 100644
--- a/utils/crypto.go
+++ b/utils/crypto.go
@@ -16,16 +16,16 @@ func EDH(privateKey ed25519.PrivateKey, remotePublicKey ed25519.PublicKey) ([]by
 	var curve25519priv [32]byte
 
 	PrivateKeyToCurve25519(&curve25519priv, &privKeyBytes)
-	curve25519pub, err := ed25519PublicKeyToCurve25519(remotePublicKey)
-	if err == nil {
-		return nil, err
+	remoteCurve25519pub, err := ed25519PublicKeyToCurve25519New(remotePublicKey)
+	if err != nil {
+		return []byte{}, err
 	}
-	secret, err := curve25519.X25519(curve25519priv[:], curve25519pub[:])
+	secret, err := curve25519.X25519(curve25519priv[:], remoteCurve25519pub[:])
 	return secret, err
 }
 
 // reproduced from https://github.com/FiloSottile/age/blob/main/agessh/agessh.go#L190
-func ed25519PublicKeyToCurve25519(pk ed25519.PublicKey) ([]byte, error) {
+func ed25519PublicKeyToCurve25519New(pk ed25519.PublicKey) ([]byte, error) {
 	// See https://blog.filippo.io/using-ed25519-keys-for-encryption and
 	// https://pkg.go.dev/filippo.io/edwards25519#Point.BytesMontgomery.
 	p, err := new(edwards25519.Point).SetBytes(pk)