http interaction verification

interaction.go

@@ -2,9 +2,12 @@ package discord
 
 import (
 	"bytes"
+	"crypto/ed25519"
+	"encoding/hex"
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"net/http"
 )
 
@@ -131,3 +134,29 @@ type InteractionResponse[T any] struct {
 	Type InteractionResponseType `json:"type"`
 	Data T                       `json:"data,omitempty"`
 }
+
+func VerifyHTTPInteraction(publicKey ed25519.PublicKey, r *http.Request) (*Interaction[any], []byte, error) {
+	sigHeader := r.Header.Get("X-Signature-Ed25519")
+	signature, err := hex.DecodeString(sigHeader)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	timestamp := []byte(r.Header.Get("X-Signature-Timestamp"))
+
+	bs, err := io.ReadAll(r.Body)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	ok := ed25519.Verify(publicKey, append(timestamp, bs...), signature)
+
+	if !ok {
+		return nil, nil, errors.New("unable to verify ed25519 signature")
+	}
+
+	req := Interaction[any]{}
+
+	err = json.Unmarshal(bs, &req)
+	return &req, bs, err
+}