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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package packet
import (
"io"
"github.com/ProtonMail/go-crypto/openpgp/errors"
)
const aeadSaltSize = 32
// SymmetricallyEncrypted represents a symmetrically encrypted byte string. The
// encrypted Contents will consist of more OpenPGP packets. See RFC 4880,
// sections 5.7 and 5.13.
type SymmetricallyEncrypted struct {
Version int
Contents io.Reader // contains tag for version 2
IntegrityProtected bool // If true it is type 18 (with MDC or AEAD). False is packet type 9
// Specific to version 1
prefix []byte
// Specific to version 2
Cipher CipherFunction
Mode AEADMode
ChunkSizeByte byte
Salt [aeadSaltSize]byte
}
const (
symmetricallyEncryptedVersionMdc = 1
symmetricallyEncryptedVersionAead = 2
)
func (se *SymmetricallyEncrypted) parse(r io.Reader) error {
if se.IntegrityProtected {
// See RFC 4880, section 5.13.
var buf [1]byte
_, err := readFull(r, buf[:])
if err != nil {
return err
}
switch buf[0] {
case symmetricallyEncryptedVersionMdc:
se.Version = symmetricallyEncryptedVersionMdc
case symmetricallyEncryptedVersionAead:
se.Version = symmetricallyEncryptedVersionAead
if err := se.parseAead(r); err != nil {
return err
}
default:
return errors.UnsupportedError("unknown SymmetricallyEncrypted version")
}
}
se.Contents = r
return nil
}
// Decrypt returns a ReadCloser, from which the decrypted Contents of the
// packet can be read. An incorrect key will only be detected after trying
// to decrypt the entire data.
func (se *SymmetricallyEncrypted) Decrypt(c CipherFunction, key []byte) (io.ReadCloser, error) {
if se.Version == symmetricallyEncryptedVersionAead {
return se.decryptAead(key)
}
return se.decryptMdc(c, key)
}
// SerializeSymmetricallyEncrypted serializes a symmetrically encrypted packet
// to w and returns a WriteCloser to which the to-be-encrypted packets can be
// written.
// If aeadSupported is set to true, SEIPDv2 is used with the indicated CipherSuite.
// Otherwise, SEIPDv1 is used with the indicated CipherFunction.
// Note: aeadSupported MUST match the value passed to SerializeEncryptedKeyAEAD
// and/or SerializeSymmetricKeyEncryptedAEADReuseKey.
// If config is nil, sensible defaults will be used.
func SerializeSymmetricallyEncrypted(w io.Writer, c CipherFunction, aeadSupported bool, cipherSuite CipherSuite, key []byte, config *Config) (Contents io.WriteCloser, err error) {
writeCloser := noOpCloser{w}
ciphertext, err := serializeStreamHeader(writeCloser, packetTypeSymmetricallyEncryptedIntegrityProtected)
if err != nil {
return
}
if aeadSupported {
return serializeSymmetricallyEncryptedAead(ciphertext, cipherSuite, config.AEADConfig.ChunkSizeByte(), config.Random(), key)
}
return serializeSymmetricallyEncryptedMdc(ciphertext, c, key, config)
}
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