func decrypt(sender, recipient *uid.Message, r io.Reader, recipientTemp *uid.KeyEntry,
privateKey string, sign bool, chkMsg bool) error {
// decrypt
var res bytes.Buffer
identities := []*uid.Message{recipient}
input := base64.NewDecoder(r)
version, preHeader, err := ReadFirstOuterHeader(input)
if err != nil {
return err
}
if version != Version {
return errors.New("wrong version")
}
ms := memstore.New()
if err := recipientTemp.SetPrivateKey(privateKey); err != nil {
return err
}
ms.AddPrivateKeyEntry(recipientTemp)
args := &DecryptArgs{
Writer: &res,
Identities: identities,
PreHeader: preHeader,
Reader: input,
Rand: cipher.RandReader,
KeyStore: ms,
}
_, sig, err := Decrypt(args)
if err != nil {
return err
}
// do not compare messages when fuzzing, because messages have to be different!
if chkMsg && res.String() != msgs.Message1 {
return errors.New("messages differ")
}
if sign {
contentHash := cipher.SHA512(res.Bytes())
decSig, err := base64.Decode(sig)
if err != nil {
return err
}
if len(decSig) != ed25519.SignatureSize {
return errors.New("signature has wrong length")
}
var sigBuf [ed25519.SignatureSize]byte
copy(sigBuf[:], decSig)
if !ed25519.Verify(sender.PublicSigKey32(), contentHash, &sigBuf) {
return errors.New("signature verification failed")
}
}
return nil
}
