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brontide: add EphemeralGenerator as a functional arg to NewBrontideMachine

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This commit modifies the NewBrontideMachine constructor to allow a
caller to specify exactly _how_ new ephemeral private keys for the
crypto handshake are generated. This allows callers a bit more
flexibility when using brontide, and also allow test cases to insert
specific public keys for use within the hand shake.
This commit is contained in:
Olaoluwa Osuntokun 2017-08-01 17:16:13 -07:00
parent 399d9c974f
commit e375a308b9
No known key found for this signature in database
GPG Key ID: 9CC5B105D03521A2
1 changed files with 33 additions and 8 deletions
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41
brontide/noise.go
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@ -303,6 +303,16 @@ func newHandshakeState(initiator bool, prologue []byte,
return h
}
// EphemeralGenerator is a functional option that allows callers to substitute
// a custom function for use when generating ephemeral keys for ActOne or
// ActTwo. The function closure return by this function can be passed into
// NewBrontideMachine as a function option parameter.
func EphemeralGenerator(gen func() (*btcec.PrivateKey, error)) func(*Machine) {
return func(m *Machine) {
m.ephemeralGen = gen
}
}
// Machine is a state-machine which implements Brontide: an
// Authenticated-key Exchange in Three Acts. Brontide is derived from the Noise
// framework, specifically implementing the Noise_XK handshake. Once the
@ -332,20 +342,38 @@ type Machine struct {
sendCipher cipherState
recvCipher cipherState
ephemeralGen func() (*btcec.PrivateKey, error)
handshakeState
}
// NewBrontideMachine creates a new instance of the brontide state-machine. If
// the responder (listener) is creating the object, then the remotePub should
// be nil. The handshake state within brontide is initialized using the ascii
// string "bitcoin" as the prologue.
// string "bitcoin" as the prologue. The last parameter is a set of variadic
// arguments for adding additional options to the brontide Machine
// initialization.
func NewBrontideMachine(initiator bool, localPub *btcec.PrivateKey,
remotePub *btcec.PublicKey) *Machine {
remotePub *btcec.PublicKey, options ...func(*Machine)) *Machine {
handshake := newHandshakeState(initiator, []byte("lightning"), localPub,
remotePub)
return &Machine{handshakeState: handshake}
m := &Machine{handshakeState: handshake}
// With the initial base machine created, we'll assign our default
// version of the ephemeral key generator.
m.ephemeralGen = func() (*btcec.PrivateKey, error) {
return btcec.NewPrivateKey(btcec.S256())
}
// With the default options established, we'll now process all the
// options passed in as parameters.
for _, option := range options {
option(m)
}
return m
}
const (
@ -392,7 +420,7 @@ func (b *Machine) GenActOne() ([ActOneSize]byte, error) {
)
// e
b.localEphemeral, err = btcec.NewPrivateKey(btcec.S256())
b.localEphemeral, err = b.ephemeralGen()
if err != nil {
return actOne, err
}
@ -465,7 +493,7 @@ func (b *Machine) GenActTwo() ([ActTwoSize]byte, error) {
)
// e
b.localEphemeral, err = btcec.NewPrivateKey(btcec.S256())
b.localEphemeral, err = b.ephemeralGen()
if err != nil {
return actTwo, err
}
@ -570,9 +598,6 @@ func (b *Machine) RecvActThree(actThree [ActThreeSize]byte) error {
actThree[:])
}
// TODO(roasbeef): print out entire version each time, also print out
// which act the error occurred at
copy(s[:], actThree[1:33+16+1])
copy(p[:], actThree[33+16+1:])