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78 lines
2.0 KiB
78 lines
2.0 KiB
// SPDX-License-Identifier: MIT
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package main
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import (
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"crypto/rand"
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"encoding/hex"
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"errors"
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"fmt"
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"golang.org/x/crypto/chacha20"
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)
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const (
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wrapNonceLen = 12
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wrapKeyLen = 32
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)
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func genWrapKeyHex() (string, error) {
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key := make([]byte, wrapKeyLen)
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if _, err := rand.Read(key); err != nil {
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return "", fmt.Errorf("wrap: key gen: %w", err)
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}
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return hex.EncodeToString(key), nil
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}
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func decodeWrapKey(enabled bool, raw string) ([]byte, error) {
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if !enabled {
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return nil, nil
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}
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if raw == "" {
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return nil, errors.New("-wrap requires -wrap-key")
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}
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key, err := hex.DecodeString(raw)
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if err != nil {
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return nil, fmt.Errorf("-wrap-key invalid hex: %w", err)
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}
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if len(key) != wrapKeyLen {
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return nil, fmt.Errorf("-wrap-key must decode to %d bytes (got %d)", wrapKeyLen, len(key))
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}
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return key, nil
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}
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func wrapPacket(key, payload []byte) ([]byte, error) {
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if len(key) != wrapKeyLen {
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return nil, fmt.Errorf("wrap: key must be %d bytes (got %d)", wrapKeyLen, len(key))
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}
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out := make([]byte, wrapNonceLen+len(payload))
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if _, err := rand.Read(out[:wrapNonceLen]); err != nil {
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return nil, fmt.Errorf("wrap: nonce gen: %w", err)
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}
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cipher, err := chacha20.NewUnauthenticatedCipher(key, out[:wrapNonceLen])
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if err != nil {
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return nil, fmt.Errorf("wrap: cipher init: %w", err)
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}
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cipher.XORKeyStream(out[wrapNonceLen:], payload)
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return out, nil
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}
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func unwrapPacket(key, wire, dst []byte) (int, error) {
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if len(key) != wrapKeyLen {
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return 0, fmt.Errorf("wrap: key must be %d bytes (got %d)", wrapKeyLen, len(key))
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}
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if len(wire) < wrapNonceLen {
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return 0, errors.New("wrap: short packet (no nonce)")
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}
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nonce := wire[:wrapNonceLen]
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ciphertext := wire[wrapNonceLen:]
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if len(ciphertext) > len(dst) {
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return 0, errors.New("wrap: dst buffer too small")
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}
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cipher, err := chacha20.NewUnauthenticatedCipher(key, nonce)
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if err != nil {
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return 0, fmt.Errorf("wrap: cipher init: %w", err)
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}
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cipher.XORKeyStream(dst[:len(ciphertext)], ciphertext)
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return len(ciphertext), nil
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}
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