mirror of
https://github.com/nbd-wtf/go-nostr.git
synced 2025-03-18 13:53:03 +01:00
ebe3d61484
changed variable names in ComputeSharedSecret to emphasize that it is agnostic about who is sender and who is receiver.
109 lines
3.5 KiB
Go
109 lines
3.5 KiB
Go
package nip04
|
|
|
|
import (
|
|
"bytes"
|
|
"crypto/aes"
|
|
"crypto/cipher"
|
|
"crypto/rand"
|
|
"encoding/base64"
|
|
"encoding/hex"
|
|
"fmt"
|
|
"strings"
|
|
|
|
"github.com/btcsuite/btcd/btcec/v2"
|
|
)
|
|
|
|
// ComputeSharedSecret returns a shared secret key used to encrypt messages.
|
|
// The private and public keys should be hex encoded.
|
|
// Uses the Diffie-Hellman key exchange (ECDH) (RFC 4753).
|
|
func ComputeSharedSecret(pub string, sk string) (sharedSecret []byte, err error) {
|
|
privKeyBytes, err := hex.DecodeString(sk)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("Error decoding sender private key: %s. \n", err)
|
|
}
|
|
privKey, _ := btcec.PrivKeyFromBytes(privKeyBytes)
|
|
|
|
// adding 02 to signal that this is a compressed public key (33 bytes)
|
|
pubKeyBytes, err := hex.DecodeString("02" + pub)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("Error decoding hex string of receiver public key: %s. \n", err)
|
|
}
|
|
pubKey, err := btcec.ParsePubKey(pubKeyBytes)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("Error parsing receiver public key: %s. \n", err)
|
|
}
|
|
|
|
return btcec.GenerateSharedSecret(privKey, pubKey), nil
|
|
}
|
|
|
|
// Encrypt encrypts message with key using aes-256-cbc.
|
|
// key should be the shared secret generated by ComputeSharedSecret.
|
|
// Returns: base64(encrypted_bytes) + "?iv=" + base64(initialization_vector).
|
|
func Encrypt(message string, key []byte) (string, error) {
|
|
// block size is 16 bytes
|
|
iv := make([]byte, 16)
|
|
// can probably use a less expensive lib since IV has to only be unique; not perfectly random; math/rand?
|
|
_, err := rand.Read(iv)
|
|
if err != nil {
|
|
return "", fmt.Errorf("Error creating initization vector: %s. \n", err.Error())
|
|
}
|
|
|
|
// automatically picks aes-256 based on key length (32 bytes)
|
|
block, err := aes.NewCipher(key)
|
|
if err != nil {
|
|
return "", fmt.Errorf("Error creating block cipher: %s. \n", err.Error())
|
|
}
|
|
mode := cipher.NewCBCEncrypter(block, iv)
|
|
|
|
plaintext := []byte(message)
|
|
|
|
// add padding
|
|
base := len(plaintext)
|
|
|
|
// this will be a number between 1 and 16 (including), never 0
|
|
padding := block.BlockSize() - base%block.BlockSize()
|
|
|
|
// encode the padding in all the padding bytes themselves
|
|
padtext := bytes.Repeat([]byte{byte(padding)}, padding)
|
|
|
|
paddedMsgBytes := append(plaintext, padtext...)
|
|
|
|
ciphertext := make([]byte, len(paddedMsgBytes))
|
|
mode.CryptBlocks(ciphertext, paddedMsgBytes)
|
|
|
|
return base64.StdEncoding.EncodeToString(ciphertext) + "?iv=" + base64.StdEncoding.EncodeToString(iv), nil
|
|
}
|
|
|
|
// Decrypt decrypts a content string using the shared secret key.
|
|
// The inverse operation to message -> Encrypt(message, key).
|
|
func Decrypt(content string, key []byte) (string, error) {
|
|
parts := strings.Split(content, "?iv=")
|
|
if len(parts) < 2 {
|
|
return "", fmt.Errorf("Error parsing encrypted message: no initilization vector. \n")
|
|
}
|
|
|
|
ciphertext, err := base64.StdEncoding.DecodeString(parts[0])
|
|
if err != nil {
|
|
return "", fmt.Errorf("Error decoding ciphertext from base64: %s. \n", err)
|
|
}
|
|
|
|
iv, err := base64.StdEncoding.DecodeString(parts[1])
|
|
if err != nil {
|
|
return "", fmt.Errorf("Error decoding iv from base64: %s. \n", err)
|
|
}
|
|
|
|
block, err := aes.NewCipher(key)
|
|
if err != nil {
|
|
return "", fmt.Errorf("Error creating block cipher: %s. \n", err.Error())
|
|
}
|
|
mode := cipher.NewCBCDecrypter(block, iv)
|
|
plaintext := make([]byte, len(ciphertext))
|
|
mode.CryptBlocks(plaintext, ciphertext)
|
|
|
|
// remove padding
|
|
padding := int(plaintext[len(plaintext)-1]) // the padding amount is encoded in the padding bytes themselves
|
|
message := string(plaintext[0 : len(plaintext)-padding])
|
|
|
|
return message, nil
|
|
}
|