func DecryptData(key, ciphertextaddnonce []byte) ([]byte, error) {
if len(key) != C.crypto_aead_chacha20poly1305_KEYBYTES {
return nil, errors.New("key must be 32 bytes!")
}
clen := len(ciphertextaddnonce) - C.crypto_aead_chacha20poly1305_NPUBBYTES
if clen-C.crypto_aead_chacha20poly1305_ABYTES <= 0 {
return nil, errors.New("Illegal ciphertext")
}
nonce := ciphertextaddnonce[clen:]
ciphertext := ciphertextaddnonce[:clen]
plaintext := make([]byte, clen-C.crypto_aead_chacha20poly1305_ABYTES)
var mlen C.ulonglong
r, err := C.crypto_aead_chacha20poly1305_decrypt((*C.uchar)(&plaintext[0]), &mlen, nil,
(*C.uchar)(&ciphertext[0]), (C.ulonglong)(clen), nil, 0, (*C.uchar)(&nonce[0]),
(*C.uchar)(&key[0]))
if err != nil {
return nil, errors.New(fmt.Sprintf("call decrypt function error : %v", err))
}
if r != 0 {
return nil, errors.New("decrypt data error")
}
return plaintext[:mlen], nil
}
func (ctx *natrAEAD) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
out := make([]byte, len(ciphertext)-_AEADOverheadBytes)
rv := C.crypto_aead_chacha20poly1305_decrypt(g2cbt(out), nil, nil,
g2cbt(ciphertext), C.ulonglong(len(ciphertext)), g2cbt(data), C.ulonglong(len(data)),
g2cbt(nonce), g2cbt(ctx.key[:]))
if rv != 0 {
return nil, errors.New("MAC error")
}
return append(dst, out...), nil
}