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saltpack_decrypt.go
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saltpack_decrypt.go
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// Copyright 2015 Keybase, Inc. All rights reserved. Use of
// this source code is governed by the included BSD license.
package engine
import (
"bytes"
"io"
"github.com/keybase/client/go/kbcrypto"
"github.com/keybase/client/go/libkb"
keybase1 "github.com/keybase/client/go/protocol/keybase1"
"github.com/keybase/saltpack"
saltpackBasic "github.com/keybase/saltpack/basic"
)
type SaltpackDecryptArg struct {
Source io.Reader
Sink io.WriteCloser
Opts keybase1.SaltpackDecryptOptions
}
// SaltpackDecrypt decrypts data read from a source into a sink.
type SaltpackDecrypt struct {
arg *SaltpackDecryptArg
res keybase1.SaltpackEncryptedMessageInfo
pnymResolver saltpack.SymmetricKeyResolver
}
// NewSaltpackDecrypt creates a SaltpackDecrypt engine.
func NewSaltpackDecrypt(arg *SaltpackDecryptArg, pnymResolver saltpack.SymmetricKeyResolver) *SaltpackDecrypt {
return &SaltpackDecrypt{
arg: arg,
pnymResolver: pnymResolver,
}
}
// Name is the unique engine name.
func (e *SaltpackDecrypt) Name() string {
return "SaltpackDecrypt"
}
// GetPrereqs returns the engine prereqs.
func (e *SaltpackDecrypt) Prereqs() Prereqs {
return Prereqs{}
}
// RequiredUIs returns the required UIs.
func (e *SaltpackDecrypt) RequiredUIs() []libkb.UIKind {
return []libkb.UIKind{
libkb.SaltpackUIKind,
libkb.SecretUIKind,
}
}
// SubConsumers returns the other UI consumers for this engine.
func (e *SaltpackDecrypt) SubConsumers() []libkb.UIConsumer {
return []libkb.UIConsumer{
&SaltpackSenderIdentify{},
}
}
func (e *SaltpackDecrypt) promptForDecrypt(m libkb.MetaContext, publicKey keybase1.KID, isAnon, signed bool) (err error) {
defer m.Trace("SaltpackDecrypt#promptForDecrypt", &err)()
spsiArg := SaltpackSenderIdentifyArg{
isAnon: isAnon,
publicKey: publicKey,
interactive: e.arg.Opts.Interactive,
forceRemoteCheck: e.arg.Opts.ForceRemoteCheck,
reason: keybase1.IdentifyReason{
Reason: "Identify who encrypted this message",
Type: keybase1.IdentifyReasonType_DECRYPT,
},
}
spsiEng := NewSaltpackSenderIdentify(m.G(), &spsiArg)
if err = RunEngine2(m, spsiEng); err != nil {
return err
}
arg := keybase1.SaltpackPromptForDecryptArg{
Sender: spsiEng.Result(),
SigningKID: publicKey,
Signed: signed,
}
e.res.Sender = arg.Sender
usedDelegateUI := false
if m.G().UIRouter != nil {
if ui, err := m.G().UIRouter.GetIdentifyUI(); err == nil && ui != nil {
usedDelegateUI = true
}
}
err = m.UIs().SaltpackUI.SaltpackPromptForDecrypt(m.Ctx(), arg, usedDelegateUI)
if err != nil {
return err
}
return err
}
func (e *SaltpackDecrypt) makeMessageInfo(me *libkb.User, mki *saltpack.MessageKeyInfo) {
if mki == nil || me == nil {
return
}
ckf := me.GetComputedKeyFamily()
for _, nr := range mki.NamedReceivers {
kid := keybase1.KIDFromRawKey(nr, byte(kbcrypto.KIDNaclDH))
if dev, _ := ckf.GetDeviceForKID(kid); dev != nil {
edev := dev.ProtExport()
edev.EncryptKey = kid
e.res.Devices = append(e.res.Devices, *edev)
}
}
e.res.NumAnonReceivers = mki.NumAnonReceivers
e.res.ReceiverIsAnon = mki.ReceiverIsAnon
}
func addToKeyring(keyring *saltpackBasic.Keyring, key *libkb.NaclDHKeyPair) {
keyring.ImportBoxKey((*[libkb.NaclDHKeysize]byte)(&key.Public), (*[libkb.NaclDHKeysize]byte)(key.Private))
}
// Used when decrypting with a paper key, as in that case there is no active device/user and we cannot rely on the
// pseudonym mechanism.
type nilPseudonymResolver struct{}
func (t *nilPseudonymResolver) ResolveKeys(identifiers [][]byte) ([]*saltpack.SymmetricKey, error) {
return make([]*saltpack.SymmetricKey, len(identifiers)), nil
}
// Run starts the engine.
func (e *SaltpackDecrypt) Run(m libkb.MetaContext) (err error) {
defer m.Trace("SaltpackDecrypt::Run", &err)()
// We don't load this in the --paperkey case.
var me *libkb.User
keyring := saltpackBasic.NewKeyring()
if e.arg.Opts.UsePaperKey {
// Prompt the user for a paper key. This doesn't require you to be
// logged in.
keypair, _, err := getPaperKey(m, nil, nil)
if err != nil {
return err
}
encryptionNaclKeyPair := keypair.EncryptionKey().(libkb.NaclDHKeyPair)
addToKeyring(keyring, &encryptionNaclKeyPair)
// If a paper key is used, we do not have PUK or an active session, so we cannot talk to the server to resolve pseudonym.
m.Debug("substituting the default PseudonymResolver as a paper key is being used for decryption")
e.pnymResolver = &nilPseudonymResolver{}
} else {
// This does require you to be logged in.
if !m.G().ActiveDevice.HaveKeys() {
return libkb.LoginRequiredError{}
}
// Only used in the makeMessageInfo call, which is helpful for old messages (one cannot encrypt messages with visible recipients any more).
me, err = libkb.LoadMe(libkb.NewLoadUserArgWithMetaContext(m))
if err != nil {
return err
}
// Get the device encryption key and per user keys.
var key *libkb.NaclDHKeyPair
var err error
key, err = m.G().ActiveDevice.NaclEncryptionKey()
if err != nil {
return err
}
m.Debug("adding device key for decryption: %v", key.GetKID())
addToKeyring(keyring, key)
perUserKeyring, err := m.G().GetPerUserKeyring(m.Ctx())
if err != nil {
return err
}
pukGen := perUserKeyring.CurrentGeneration()
for i := 1; i <= int(pukGen); i++ {
key, err = perUserKeyring.GetEncryptionKeyByGeneration(m, keybase1.PerUserKeyGeneration(i))
m.Debug("adding per user key at generation %v for decryption: %v", i, key.GetKID())
if err != nil {
return err
}
addToKeyring(keyring, key)
}
}
// For DH mode.
hookMki := func(mki *saltpack.MessageKeyInfo) error {
kidToIdentify := libkb.BoxPublicKeyToKeybaseKID(mki.SenderKey)
return e.promptForDecrypt(m, kidToIdentify, mki.SenderIsAnon, false /* not signed */)
}
// For signcryption mode.
hookSenderSigningKey := func(senderSigningKey saltpack.SigningPublicKey) error {
kidToIdentify := libkb.SigningPublicKeyToKeybaseKID(senderSigningKey)
// See if the sender signing key is nil or all zeroes.
isAnon := false
signed := true
if senderSigningKey == nil || bytes.Equal(senderSigningKey.ToKID(), make([]byte, len(senderSigningKey.ToKID()))) {
isAnon = true
signed = false
}
return e.promptForDecrypt(m, kidToIdentify, isAnon, signed)
}
m.Debug("| SaltpackDecrypt")
var mki *saltpack.MessageKeyInfo
mki, err = libkb.SaltpackDecrypt(m, e.arg.Source, e.arg.Sink, keyring, hookMki, hookSenderSigningKey, e.pnymResolver)
if decErr, ok := err.(libkb.DecryptionError); ok && decErr.Cause.Err == saltpack.ErrNoDecryptionKey {
m.Debug("switching cause of libkb.DecryptionError from saltpack.ErrNoDecryptionKey to more specific libkb.NoDecryptionKeyError")
if e.arg.Opts.UsePaperKey {
return libkb.DecryptionError{Cause: libkb.ErrorCause{Err: libkb.NoDecryptionKeyError{Msg: "this message was not directly encrypted for the given paper key. In some cases, you might still be able to decrypt the message from a device provisioned with this key."}, StatusCode: libkb.SCDecryptionKeyNotFound}}
}
err = libkb.DecryptionError{Cause: libkb.ErrorCause{Err: libkb.NoDecryptionKeyError{Msg: "no suitable key found"}, StatusCode: libkb.SCDecryptionKeyNotFound}}
}
// Since messages recipients are never public any more, this is only meaningful for messages generated by
// very old clients (or potentially saltpack messages generated for a keybase user by some other app).
// It's ok if me is nil here.
e.makeMessageInfo(me, mki)
return err
}
func (e *SaltpackDecrypt) MessageInfo() keybase1.SaltpackEncryptedMessageInfo {
return e.res
}