Beispiel #1
0
// SymmetricallyEncrypt acts like gpg -c: it encrypts a file with a passphrase.
// The resulting WriteCloser must be closed after the contents of the file have
// been written.
func SymmetricallyEncrypt(ciphertext io.Writer, passphrase []byte, hints *FileHints) (plaintext io.WriteCloser, err error) {
	if hints == nil {
		hints = &FileHints{}
	}

	key, err := packet.SerializeSymmetricKeyEncrypted(ciphertext, rand.Reader, passphrase, packet.CipherAES128)
	if err != nil {
		return
	}
	w, err := packet.SerializeSymmetricallyEncrypted(ciphertext, packet.CipherAES128, key)
	if err != nil {
		return
	}
	return packet.SerializeLiteral(w, hints.IsBinary, hints.FileName, hints.EpochSeconds)
}
Beispiel #2
0
// Encrypt encrypts a message to a number of recipients and, optionally, signs
// it. hints contains optional information, that is also encrypted, that aids
// the recipients in processing the message. The resulting WriteCloser must
// be closed after the contents of the file have been written.
func Encrypt(ciphertext io.Writer, to []*Entity, signed *Entity, hints *FileHints) (plaintext io.WriteCloser, err error) {
	var signer *packet.PrivateKey
	if signed != nil {
		signer = signed.signingKey().PrivateKey
		if signer == nil || signer.Encrypted {
			return nil, error_.InvalidArgumentError("signing key must be decrypted")
		}
	}

	// These are the possible ciphers that we'll use for the message.
	candidateCiphers := []uint8{
		uint8(packet.CipherAES128),
		uint8(packet.CipherAES256),
		uint8(packet.CipherCAST5),
	}
	// These are the possible hash functions that we'll use for the signature.
	candidateHashes := []uint8{
		hashToHashId(crypto.SHA256),
		hashToHashId(crypto.SHA512),
		hashToHashId(crypto.SHA1),
		hashToHashId(crypto.RIPEMD160),
	}
	// In the event that a recipient doesn't specify any supported ciphers
	// or hash functions, these are the ones that we assume that every
	// implementation supports.
	defaultCiphers := candidateCiphers[len(candidateCiphers)-1:]
	defaultHashes := candidateHashes[len(candidateHashes)-1:]

	encryptKeys := make([]Key, len(to))
	for i := range to {
		encryptKeys[i] = to[i].encryptionKey()
		if encryptKeys[i].PublicKey == nil {
			return nil, error_.InvalidArgumentError("cannot encrypt a message to key id " + strconv.Uitob64(to[i].PrimaryKey.KeyId, 16) + " because it has no encryption keys")
		}

		sig := to[i].primaryIdentity().SelfSignature

		preferredSymmetric := sig.PreferredSymmetric
		if len(preferredSymmetric) == 0 {
			preferredSymmetric = defaultCiphers
		}
		preferredHashes := sig.PreferredHash
		if len(preferredHashes) == 0 {
			preferredHashes = defaultHashes
		}
		candidateCiphers = intersectPreferences(candidateCiphers, preferredSymmetric)
		candidateHashes = intersectPreferences(candidateHashes, preferredHashes)
	}

	if len(candidateCiphers) == 0 || len(candidateHashes) == 0 {
		return nil, error_.InvalidArgumentError("cannot encrypt because recipient set shares no common algorithms")
	}

	cipher := packet.CipherFunction(candidateCiphers[0])
	hash, _ := s2k.HashIdToHash(candidateHashes[0])
	symKey := make([]byte, cipher.KeySize())
	if _, err := io.ReadFull(rand.Reader, symKey); err != nil {
		return nil, err
	}

	for _, key := range encryptKeys {
		if err := packet.SerializeEncryptedKey(ciphertext, rand.Reader, key.PublicKey, cipher, symKey); err != nil {
			return nil, err
		}
	}

	encryptedData, err := packet.SerializeSymmetricallyEncrypted(ciphertext, cipher, symKey)
	if err != nil {
		return
	}

	if signer != nil {
		ops := &packet.OnePassSignature{
			SigType:    packet.SigTypeBinary,
			Hash:       hash,
			PubKeyAlgo: signer.PubKeyAlgo,
			KeyId:      signer.KeyId,
			IsLast:     true,
		}
		if err := ops.Serialize(encryptedData); err != nil {
			return nil, err
		}
	}

	if hints == nil {
		hints = &FileHints{}
	}

	w := encryptedData
	if signer != nil {
		// If we need to write a signature packet after the literal
		// data then we need to stop literalData from closing
		// encryptedData.
		w = noOpCloser{encryptedData}

	}
	literalData, err := packet.SerializeLiteral(w, hints.IsBinary, hints.FileName, hints.EpochSeconds)
	if err != nil {
		return nil, err
	}

	if signer != nil {
		return signatureWriter{encryptedData, literalData, hash, hash.New(), signer}, nil
	}
	return literalData, nil
}