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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
}
}
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