585 lines
20 KiB
Go
585 lines
20 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package packet
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import (
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"bytes"
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"crypto"
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"crypto/rsa"
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"encoding/binary"
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"encoding/hex"
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"io"
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"math/big"
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"strconv"
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"github.com/ProtonMail/go-crypto/openpgp/ecdh"
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"github.com/ProtonMail/go-crypto/openpgp/elgamal"
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"github.com/ProtonMail/go-crypto/openpgp/errors"
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"github.com/ProtonMail/go-crypto/openpgp/internal/encoding"
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"github.com/ProtonMail/go-crypto/openpgp/x25519"
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"github.com/ProtonMail/go-crypto/openpgp/x448"
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)
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// EncryptedKey represents a public-key encrypted session key. See RFC 4880,
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// section 5.1.
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type EncryptedKey struct {
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Version int
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KeyId uint64
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KeyVersion int // v6
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KeyFingerprint []byte // v6
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Algo PublicKeyAlgorithm
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CipherFunc CipherFunction // only valid after a successful Decrypt for a v3 packet
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Key []byte // only valid after a successful Decrypt
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encryptedMPI1, encryptedMPI2 encoding.Field
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ephemeralPublicX25519 *x25519.PublicKey // used for x25519
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ephemeralPublicX448 *x448.PublicKey // used for x448
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encryptedSession []byte // used for x25519 and x448
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}
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func (e *EncryptedKey) parse(r io.Reader) (err error) {
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var buf [8]byte
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_, err = readFull(r, buf[:versionSize])
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if err != nil {
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return
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}
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e.Version = int(buf[0])
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if e.Version != 3 && e.Version != 6 {
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return errors.UnsupportedError("unknown EncryptedKey version " + strconv.Itoa(int(buf[0])))
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}
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if e.Version == 6 {
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//Read a one-octet size of the following two fields.
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if _, err = readFull(r, buf[:1]); err != nil {
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return
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}
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// The size may also be zero, and the key version and
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// fingerprint omitted for an "anonymous recipient"
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if buf[0] != 0 {
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// non-anonymous case
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_, err = readFull(r, buf[:versionSize])
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if err != nil {
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return
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}
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e.KeyVersion = int(buf[0])
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if e.KeyVersion != 4 && e.KeyVersion != 6 {
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return errors.UnsupportedError("unknown public key version " + strconv.Itoa(e.KeyVersion))
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}
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var fingerprint []byte
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if e.KeyVersion == 6 {
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fingerprint = make([]byte, fingerprintSizeV6)
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} else if e.KeyVersion == 4 {
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fingerprint = make([]byte, fingerprintSize)
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}
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_, err = readFull(r, fingerprint)
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if err != nil {
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return
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}
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e.KeyFingerprint = fingerprint
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if e.KeyVersion == 6 {
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e.KeyId = binary.BigEndian.Uint64(e.KeyFingerprint[:keyIdSize])
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} else if e.KeyVersion == 4 {
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e.KeyId = binary.BigEndian.Uint64(e.KeyFingerprint[fingerprintSize-keyIdSize : fingerprintSize])
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}
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}
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} else {
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_, err = readFull(r, buf[:8])
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if err != nil {
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return
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}
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e.KeyId = binary.BigEndian.Uint64(buf[:keyIdSize])
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}
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_, err = readFull(r, buf[:1])
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if err != nil {
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return
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}
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e.Algo = PublicKeyAlgorithm(buf[0])
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var cipherFunction byte
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switch e.Algo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
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e.encryptedMPI1 = new(encoding.MPI)
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if _, err = e.encryptedMPI1.ReadFrom(r); err != nil {
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return
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}
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case PubKeyAlgoElGamal:
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e.encryptedMPI1 = new(encoding.MPI)
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if _, err = e.encryptedMPI1.ReadFrom(r); err != nil {
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return
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}
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e.encryptedMPI2 = new(encoding.MPI)
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if _, err = e.encryptedMPI2.ReadFrom(r); err != nil {
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return
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}
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case PubKeyAlgoECDH:
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e.encryptedMPI1 = new(encoding.MPI)
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if _, err = e.encryptedMPI1.ReadFrom(r); err != nil {
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return
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}
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e.encryptedMPI2 = new(encoding.OID)
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if _, err = e.encryptedMPI2.ReadFrom(r); err != nil {
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return
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}
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case PubKeyAlgoX25519:
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e.ephemeralPublicX25519, e.encryptedSession, cipherFunction, err = x25519.DecodeFields(r, e.Version == 6)
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if err != nil {
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return
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}
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case PubKeyAlgoX448:
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e.ephemeralPublicX448, e.encryptedSession, cipherFunction, err = x448.DecodeFields(r, e.Version == 6)
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if err != nil {
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return
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}
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}
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if e.Version < 6 {
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switch e.Algo {
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case PubKeyAlgoX25519, PubKeyAlgoX448:
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e.CipherFunc = CipherFunction(cipherFunction)
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// Check for validiy is in the Decrypt method
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}
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}
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_, err = consumeAll(r)
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return
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}
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// Decrypt decrypts an encrypted session key with the given private key. The
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// private key must have been decrypted first.
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// If config is nil, sensible defaults will be used.
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func (e *EncryptedKey) Decrypt(priv *PrivateKey, config *Config) error {
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if e.Version < 6 && e.KeyId != 0 && e.KeyId != priv.KeyId {
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return errors.InvalidArgumentError("cannot decrypt encrypted session key for key id " + strconv.FormatUint(e.KeyId, 16) + " with private key id " + strconv.FormatUint(priv.KeyId, 16))
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}
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if e.Version == 6 && e.KeyVersion != 0 && !bytes.Equal(e.KeyFingerprint, priv.Fingerprint) {
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return errors.InvalidArgumentError("cannot decrypt encrypted session key for key fingerprint " + hex.EncodeToString(e.KeyFingerprint) + " with private key fingerprint " + hex.EncodeToString(priv.Fingerprint))
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}
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if e.Algo != priv.PubKeyAlgo {
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return errors.InvalidArgumentError("cannot decrypt encrypted session key of type " + strconv.Itoa(int(e.Algo)) + " with private key of type " + strconv.Itoa(int(priv.PubKeyAlgo)))
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}
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if priv.Dummy() {
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return errors.ErrDummyPrivateKey("dummy key found")
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}
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var err error
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var b []byte
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// TODO(agl): use session key decryption routines here to avoid
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// padding oracle attacks.
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switch priv.PubKeyAlgo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
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// Supports both *rsa.PrivateKey and crypto.Decrypter
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k := priv.PrivateKey.(crypto.Decrypter)
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b, err = k.Decrypt(config.Random(), padToKeySize(k.Public().(*rsa.PublicKey), e.encryptedMPI1.Bytes()), nil)
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case PubKeyAlgoElGamal:
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c1 := new(big.Int).SetBytes(e.encryptedMPI1.Bytes())
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c2 := new(big.Int).SetBytes(e.encryptedMPI2.Bytes())
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b, err = elgamal.Decrypt(priv.PrivateKey.(*elgamal.PrivateKey), c1, c2)
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case PubKeyAlgoECDH:
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vsG := e.encryptedMPI1.Bytes()
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m := e.encryptedMPI2.Bytes()
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oid := priv.PublicKey.oid.EncodedBytes()
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fp := priv.PublicKey.Fingerprint[:]
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if priv.PublicKey.Version == 5 {
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// For v5 the, the fingerprint must be restricted to 20 bytes
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fp = fp[:20]
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}
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b, err = ecdh.Decrypt(priv.PrivateKey.(*ecdh.PrivateKey), vsG, m, oid, fp)
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case PubKeyAlgoX25519:
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b, err = x25519.Decrypt(priv.PrivateKey.(*x25519.PrivateKey), e.ephemeralPublicX25519, e.encryptedSession)
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case PubKeyAlgoX448:
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b, err = x448.Decrypt(priv.PrivateKey.(*x448.PrivateKey), e.ephemeralPublicX448, e.encryptedSession)
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default:
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err = errors.InvalidArgumentError("cannot decrypt encrypted session key with private key of type " + strconv.Itoa(int(priv.PubKeyAlgo)))
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}
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if err != nil {
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return err
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}
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var key []byte
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switch priv.PubKeyAlgo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoElGamal, PubKeyAlgoECDH:
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keyOffset := 0
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if e.Version < 6 {
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e.CipherFunc = CipherFunction(b[0])
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keyOffset = 1
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if !e.CipherFunc.IsSupported() {
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return errors.UnsupportedError("unsupported encryption function")
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}
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}
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key, err = decodeChecksumKey(b[keyOffset:])
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if err != nil {
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return err
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}
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case PubKeyAlgoX25519, PubKeyAlgoX448:
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if e.Version < 6 {
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switch e.CipherFunc {
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case CipherAES128, CipherAES192, CipherAES256:
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break
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default:
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return errors.StructuralError("v3 PKESK mandates AES as cipher function for x25519 and x448")
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}
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}
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key = b[:]
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default:
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return errors.UnsupportedError("unsupported algorithm for decryption")
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}
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e.Key = key
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return nil
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}
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// Serialize writes the encrypted key packet, e, to w.
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func (e *EncryptedKey) Serialize(w io.Writer) error {
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var encodedLength int
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switch e.Algo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
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encodedLength = int(e.encryptedMPI1.EncodedLength())
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case PubKeyAlgoElGamal:
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encodedLength = int(e.encryptedMPI1.EncodedLength()) + int(e.encryptedMPI2.EncodedLength())
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case PubKeyAlgoECDH:
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encodedLength = int(e.encryptedMPI1.EncodedLength()) + int(e.encryptedMPI2.EncodedLength())
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case PubKeyAlgoX25519:
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encodedLength = x25519.EncodedFieldsLength(e.encryptedSession, e.Version == 6)
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case PubKeyAlgoX448:
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encodedLength = x448.EncodedFieldsLength(e.encryptedSession, e.Version == 6)
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default:
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return errors.InvalidArgumentError("don't know how to serialize encrypted key type " + strconv.Itoa(int(e.Algo)))
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}
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packetLen := versionSize /* version */ + keyIdSize /* key id */ + algorithmSize /* algo */ + encodedLength
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if e.Version == 6 {
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packetLen = versionSize /* version */ + algorithmSize /* algo */ + encodedLength + keyVersionSize /* key version */
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if e.KeyVersion == 6 {
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packetLen += fingerprintSizeV6
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} else if e.KeyVersion == 4 {
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packetLen += fingerprintSize
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}
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}
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err := serializeHeader(w, packetTypeEncryptedKey, packetLen)
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if err != nil {
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return err
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}
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_, err = w.Write([]byte{byte(e.Version)})
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if err != nil {
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return err
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}
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if e.Version == 6 {
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_, err = w.Write([]byte{byte(e.KeyVersion)})
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if err != nil {
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return err
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}
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// The key version number may also be zero,
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// and the fingerprint omitted
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if e.KeyVersion != 0 {
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_, err = w.Write(e.KeyFingerprint)
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if err != nil {
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return err
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}
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}
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} else {
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// Write KeyID
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err = binary.Write(w, binary.BigEndian, e.KeyId)
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if err != nil {
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return err
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}
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}
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_, err = w.Write([]byte{byte(e.Algo)})
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if err != nil {
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return err
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}
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switch e.Algo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
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_, err := w.Write(e.encryptedMPI1.EncodedBytes())
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return err
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case PubKeyAlgoElGamal:
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if _, err := w.Write(e.encryptedMPI1.EncodedBytes()); err != nil {
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return err
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}
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_, err := w.Write(e.encryptedMPI2.EncodedBytes())
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return err
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case PubKeyAlgoECDH:
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if _, err := w.Write(e.encryptedMPI1.EncodedBytes()); err != nil {
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return err
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}
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_, err := w.Write(e.encryptedMPI2.EncodedBytes())
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return err
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case PubKeyAlgoX25519:
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err := x25519.EncodeFields(w, e.ephemeralPublicX25519, e.encryptedSession, byte(e.CipherFunc), e.Version == 6)
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return err
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case PubKeyAlgoX448:
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err := x448.EncodeFields(w, e.ephemeralPublicX448, e.encryptedSession, byte(e.CipherFunc), e.Version == 6)
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return err
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default:
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panic("internal error")
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}
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}
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// SerializeEncryptedKeyAEAD serializes an encrypted key packet to w that contains
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// key, encrypted to pub.
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// If aeadSupported is set, PKESK v6 is used, otherwise v3.
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// Note: aeadSupported MUST match the value passed to SerializeSymmetricallyEncrypted.
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// If config is nil, sensible defaults will be used.
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func SerializeEncryptedKeyAEAD(w io.Writer, pub *PublicKey, cipherFunc CipherFunction, aeadSupported bool, key []byte, config *Config) error {
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return SerializeEncryptedKeyAEADwithHiddenOption(w, pub, cipherFunc, aeadSupported, key, false, config)
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}
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// SerializeEncryptedKeyAEADwithHiddenOption serializes an encrypted key packet to w that contains
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// key, encrypted to pub.
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// Offers the hidden flag option to indicated if the PKESK packet should include a wildcard KeyID.
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// If aeadSupported is set, PKESK v6 is used, otherwise v3.
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// Note: aeadSupported MUST match the value passed to SerializeSymmetricallyEncrypted.
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// If config is nil, sensible defaults will be used.
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func SerializeEncryptedKeyAEADwithHiddenOption(w io.Writer, pub *PublicKey, cipherFunc CipherFunction, aeadSupported bool, key []byte, hidden bool, config *Config) error {
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var buf [36]byte // max possible header size is v6
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lenHeaderWritten := versionSize
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version := 3
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if aeadSupported {
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version = 6
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}
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// An implementation MUST NOT generate ElGamal v6 PKESKs.
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if version == 6 && pub.PubKeyAlgo == PubKeyAlgoElGamal {
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return errors.InvalidArgumentError("ElGamal v6 PKESK are not allowed")
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}
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// In v3 PKESKs, for x25519 and x448, mandate using AES
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if version == 3 && (pub.PubKeyAlgo == PubKeyAlgoX25519 || pub.PubKeyAlgo == PubKeyAlgoX448) {
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switch cipherFunc {
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case CipherAES128, CipherAES192, CipherAES256:
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break
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default:
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return errors.InvalidArgumentError("v3 PKESK mandates AES for x25519 and x448")
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}
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}
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buf[0] = byte(version)
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// If hidden is set, the key should be hidden
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// An implementation MAY accept or use a Key ID of all zeros,
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// or a key version of zero and no key fingerprint, to hide the intended decryption key.
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// See Section 5.1.8. in the open pgp crypto refresh
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if version == 6 {
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if !hidden {
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// A one-octet size of the following two fields.
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buf[1] = byte(keyVersionSize + len(pub.Fingerprint))
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// A one octet key version number.
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buf[2] = byte(pub.Version)
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lenHeaderWritten += keyVersionSize + 1
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// The fingerprint of the public key
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copy(buf[lenHeaderWritten:lenHeaderWritten+len(pub.Fingerprint)], pub.Fingerprint)
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lenHeaderWritten += len(pub.Fingerprint)
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} else {
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// The size may also be zero, and the key version
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// and fingerprint omitted for an "anonymous recipient"
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buf[1] = 0
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lenHeaderWritten += 1
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}
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} else {
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if !hidden {
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binary.BigEndian.PutUint64(buf[versionSize:(versionSize+keyIdSize)], pub.KeyId)
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}
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lenHeaderWritten += keyIdSize
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}
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buf[lenHeaderWritten] = byte(pub.PubKeyAlgo)
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lenHeaderWritten += algorithmSize
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var keyBlock []byte
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switch pub.PubKeyAlgo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoElGamal, PubKeyAlgoECDH:
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lenKeyBlock := len(key) + 2
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if version < 6 {
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lenKeyBlock += 1 // cipher type included
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}
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keyBlock = make([]byte, lenKeyBlock)
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keyOffset := 0
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if version < 6 {
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keyBlock[0] = byte(cipherFunc)
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keyOffset = 1
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}
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encodeChecksumKey(keyBlock[keyOffset:], key)
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case PubKeyAlgoX25519, PubKeyAlgoX448:
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// algorithm is added in plaintext below
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keyBlock = key
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}
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switch pub.PubKeyAlgo {
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case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
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return serializeEncryptedKeyRSA(w, config.Random(), buf[:lenHeaderWritten], pub.PublicKey.(*rsa.PublicKey), keyBlock)
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case PubKeyAlgoElGamal:
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return serializeEncryptedKeyElGamal(w, config.Random(), buf[:lenHeaderWritten], pub.PublicKey.(*elgamal.PublicKey), keyBlock)
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case PubKeyAlgoECDH:
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return serializeEncryptedKeyECDH(w, config.Random(), buf[:lenHeaderWritten], pub.PublicKey.(*ecdh.PublicKey), keyBlock, pub.oid, pub.Fingerprint)
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case PubKeyAlgoX25519:
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return serializeEncryptedKeyX25519(w, config.Random(), buf[:lenHeaderWritten], pub.PublicKey.(*x25519.PublicKey), keyBlock, byte(cipherFunc), version)
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case PubKeyAlgoX448:
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return serializeEncryptedKeyX448(w, config.Random(), buf[:lenHeaderWritten], pub.PublicKey.(*x448.PublicKey), keyBlock, byte(cipherFunc), version)
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case PubKeyAlgoDSA, PubKeyAlgoRSASignOnly:
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return errors.InvalidArgumentError("cannot encrypt to public key of type " + strconv.Itoa(int(pub.PubKeyAlgo)))
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}
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return errors.UnsupportedError("encrypting a key to public key of type " + strconv.Itoa(int(pub.PubKeyAlgo)))
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}
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// SerializeEncryptedKey serializes an encrypted key packet to w that contains
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// key, encrypted to pub.
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// PKESKv6 is used if config.AEAD() is not nil.
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// If config is nil, sensible defaults will be used.
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// Deprecated: Use SerializeEncryptedKeyAEAD instead.
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func SerializeEncryptedKey(w io.Writer, pub *PublicKey, cipherFunc CipherFunction, key []byte, config *Config) error {
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return SerializeEncryptedKeyAEAD(w, pub, cipherFunc, config.AEAD() != nil, key, config)
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}
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// SerializeEncryptedKeyWithHiddenOption serializes an encrypted key packet to w that contains
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// key, encrypted to pub. PKESKv6 is used if config.AEAD() is not nil.
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// The hidden option controls if the packet should be anonymous, i.e., omit key metadata.
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// If config is nil, sensible defaults will be used.
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// Deprecated: Use SerializeEncryptedKeyAEADwithHiddenOption instead.
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func SerializeEncryptedKeyWithHiddenOption(w io.Writer, pub *PublicKey, cipherFunc CipherFunction, key []byte, hidden bool, config *Config) error {
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return SerializeEncryptedKeyAEADwithHiddenOption(w, pub, cipherFunc, config.AEAD() != nil, key, hidden, config)
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}
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func serializeEncryptedKeyRSA(w io.Writer, rand io.Reader, header []byte, pub *rsa.PublicKey, keyBlock []byte) error {
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|
cipherText, err := rsa.EncryptPKCS1v15(rand, pub, keyBlock)
|
|
if err != nil {
|
|
return errors.InvalidArgumentError("RSA encryption failed: " + err.Error())
|
|
}
|
|
|
|
cipherMPI := encoding.NewMPI(cipherText)
|
|
packetLen := len(header) /* header length */ + int(cipherMPI.EncodedLength())
|
|
|
|
err = serializeHeader(w, packetTypeEncryptedKey, packetLen)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
_, err = w.Write(header[:])
|
|
if err != nil {
|
|
return err
|
|
}
|
|
_, err = w.Write(cipherMPI.EncodedBytes())
|
|
return err
|
|
}
|
|
|
|
func serializeEncryptedKeyElGamal(w io.Writer, rand io.Reader, header []byte, pub *elgamal.PublicKey, keyBlock []byte) error {
|
|
c1, c2, err := elgamal.Encrypt(rand, pub, keyBlock)
|
|
if err != nil {
|
|
return errors.InvalidArgumentError("ElGamal encryption failed: " + err.Error())
|
|
}
|
|
|
|
packetLen := len(header) /* header length */
|
|
packetLen += 2 /* mpi size */ + (c1.BitLen()+7)/8
|
|
packetLen += 2 /* mpi size */ + (c2.BitLen()+7)/8
|
|
|
|
err = serializeHeader(w, packetTypeEncryptedKey, packetLen)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
_, err = w.Write(header[:])
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if _, err = w.Write(new(encoding.MPI).SetBig(c1).EncodedBytes()); err != nil {
|
|
return err
|
|
}
|
|
_, err = w.Write(new(encoding.MPI).SetBig(c2).EncodedBytes())
|
|
return err
|
|
}
|
|
|
|
func serializeEncryptedKeyECDH(w io.Writer, rand io.Reader, header []byte, pub *ecdh.PublicKey, keyBlock []byte, oid encoding.Field, fingerprint []byte) error {
|
|
vsG, c, err := ecdh.Encrypt(rand, pub, keyBlock, oid.EncodedBytes(), fingerprint)
|
|
if err != nil {
|
|
return errors.InvalidArgumentError("ECDH encryption failed: " + err.Error())
|
|
}
|
|
|
|
g := encoding.NewMPI(vsG)
|
|
m := encoding.NewOID(c)
|
|
|
|
packetLen := len(header) /* header length */
|
|
packetLen += int(g.EncodedLength()) + int(m.EncodedLength())
|
|
|
|
err = serializeHeader(w, packetTypeEncryptedKey, packetLen)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
_, err = w.Write(header[:])
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if _, err = w.Write(g.EncodedBytes()); err != nil {
|
|
return err
|
|
}
|
|
_, err = w.Write(m.EncodedBytes())
|
|
return err
|
|
}
|
|
|
|
func serializeEncryptedKeyX25519(w io.Writer, rand io.Reader, header []byte, pub *x25519.PublicKey, keyBlock []byte, cipherFunc byte, version int) error {
|
|
ephemeralPublicX25519, ciphertext, err := x25519.Encrypt(rand, pub, keyBlock)
|
|
if err != nil {
|
|
return errors.InvalidArgumentError("x25519 encryption failed: " + err.Error())
|
|
}
|
|
|
|
packetLen := len(header) /* header length */
|
|
packetLen += x25519.EncodedFieldsLength(ciphertext, version == 6)
|
|
|
|
err = serializeHeader(w, packetTypeEncryptedKey, packetLen)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
_, err = w.Write(header[:])
|
|
if err != nil {
|
|
return err
|
|
}
|
|
return x25519.EncodeFields(w, ephemeralPublicX25519, ciphertext, cipherFunc, version == 6)
|
|
}
|
|
|
|
func serializeEncryptedKeyX448(w io.Writer, rand io.Reader, header []byte, pub *x448.PublicKey, keyBlock []byte, cipherFunc byte, version int) error {
|
|
ephemeralPublicX448, ciphertext, err := x448.Encrypt(rand, pub, keyBlock)
|
|
if err != nil {
|
|
return errors.InvalidArgumentError("x448 encryption failed: " + err.Error())
|
|
}
|
|
|
|
packetLen := len(header) /* header length */
|
|
packetLen += x448.EncodedFieldsLength(ciphertext, version == 6)
|
|
|
|
err = serializeHeader(w, packetTypeEncryptedKey, packetLen)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
_, err = w.Write(header[:])
|
|
if err != nil {
|
|
return err
|
|
}
|
|
return x448.EncodeFields(w, ephemeralPublicX448, ciphertext, cipherFunc, version == 6)
|
|
}
|
|
|
|
func checksumKeyMaterial(key []byte) uint16 {
|
|
var checksum uint16
|
|
for _, v := range key {
|
|
checksum += uint16(v)
|
|
}
|
|
return checksum
|
|
}
|
|
|
|
func decodeChecksumKey(msg []byte) (key []byte, err error) {
|
|
key = msg[:len(msg)-2]
|
|
expectedChecksum := uint16(msg[len(msg)-2])<<8 | uint16(msg[len(msg)-1])
|
|
checksum := checksumKeyMaterial(key)
|
|
if checksum != expectedChecksum {
|
|
err = errors.StructuralError("session key checksum is incorrect")
|
|
}
|
|
return
|
|
}
|
|
|
|
func encodeChecksumKey(buffer []byte, key []byte) {
|
|
copy(buffer, key)
|
|
checksum := checksumKeyMaterial(key)
|
|
buffer[len(key)] = byte(checksum >> 8)
|
|
buffer[len(key)+1] = byte(checksum)
|
|
}
|