1 files changed, 47 insertions, 0 deletions
diff --git a/internal/relay/relay.go b/internal/relay/relay.go
new file mode 100644
index 0000000..9cd0366
--- /dev/null
+++ b/internal/relay/relay.go
@@ -0,0 +1,47 @@
+package relay
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"nymdrop/internal/nym"
+)
+
+const maxPayloadBytes = 10 * 1024 * 1024 // 10 MB
+
+// Relay receives ciphertext and forwards it through Nym. Nothing is written to disk.
+type Relay struct {
+	nym *nym.Client
+}
+
+func New(client *nym.Client) *Relay {
+	return &Relay{nym: client}
+}
+
+// Forward reads ciphertext from r, sends it over Nym, then zeros the buffer.
+func (r *Relay) Forward(body io.Reader) error {
+	buf := make([]byte, maxPayloadBytes)
+	n, err := io.ReadFull(body, buf)
+	if err != nil && err != io.ErrUnexpectedEOF {
+		return fmt.Errorf("read payload: %w", err)
+	}
+	payload := buf[:n]
+	defer zeroBytes(payload)
+
+	// Prepend a random nonce so identical submissions look different on the wire.
+	nonce := make([]byte, 16)
+	if _, err := rand.Read(nonce); err != nil {
+		return fmt.Errorf("nonce: %w", err)
+	}
+	packet := append([]byte(hex.EncodeToString(nonce)+":"), payload...)
+	defer zeroBytes(packet)
+
+	return r.nym.Send(packet)
+}
+
+func zeroBytes(b []byte) {
+	for i := range b {
+		b[i] = 0
+	}
+}