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brontide: an authenticated key agreement protocol in three acts

Browse Source 
This commit introduces Brontide: an authenticated key agreement
protocol in three acts. Brontide is the successor to lndc within lnd,
and ultimately within the greater Lighting Network. Brontide uses the
Noise_XK handshake for initial key agreement, then implements an AEAD
scheme which encrypts+authenticates both packets, and the lengths of
the packets on the wire. The initial authentication handshake preserves
the responder’s identity by never transmitting it to the initiator and
performing mutual authentication via an incremental Triple-DH based on
ECDH of secp256k1 and an HKDF which uses SHA-256.

Bronzed isn’t yet integrated within the wider daemon yet. Full
integration will land in a future pull request.
This commit is contained in:
Olaoluwa Osuntokun 2016-10-17 19:41:20 -07:00
parent 56ab64ecab
commit ab97d9693f
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GPG Key ID: 9CC5B105D03521A2
4 changed files with 966 additions and 0 deletions
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171
brontide/conn.go Normal file
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package brontide
import (
"bytes"
"io"
"net"
"time"
"github.com/roasbeef/btcd/btcec"
)
// Conn is an implementation of net.Conn which enforces an authenticated key
// exchange and message encryption protocol dubbed "Brontide" after initial TCP
// connection establishment. In the case of a successful handshake, all
// messages sent via the .Write() method are encrypted with an AEAD cipher
// along with an encrypted length-prefix. See the BrontideMachine struct for
// additional details w.r.t to the handshake and encryption scheme.
type Conn struct {
conn net.Conn
noise *BrontideMachine
readBuf bytes.Buffer
}
// A compile-time assertion to ensure that Conn meets the net.Conn interface.
var _ net.Conn = (*Conn)(nil)
// Dial attempts to establish an encrypted+authenticated connection with the
// remote peer located at address which has remotePub as its long-term static
// public key. In the case of a handshake failure, the connection is closed and
// a non-nil error is returned.
func Dial(localPriv *btcec.PrivateKey, remotePub *btcec.PublicKey,
address string) (*Conn, error) {
conn, err := net.Dial("tcp", address)
if err != nil {
return nil, err
}
b := &Conn{
conn: conn,
noise: NewBrontideMachine(true, localPriv, remotePub),
}
// Initiate the handshake by sending the first act to the receiver.
actOne, err := b.noise.GenActOne()
if err != nil {
return nil, err
}
if _, err := conn.Write(actOne[:]); err != nil {
return nil, err
}
// If the first act was successful (we know that address is actually
// remotePub), then read the second act after which we'll be able to
// send our static public key to the remote peer with strong forward
// secrecy.
var actTwo [ActTwoSize]byte
if _, err := io.ReadFull(conn, actTwo[:]); err != nil {
return nil, err
}
if err := b.noise.RecvActTwo(actTwo); err != nil {
return nil, err
}
// Finally, complete the handshake by sending over our encrypted static
// key and execute the final ECDH operation.
actThree, err := b.noise.GenActThree()
if err != nil {
return nil, err
}
if _, err := conn.Write(actThree[:]); err != nil {
return nil, err
}
return b, nil
}
// Read reads data from the connection. Read can be made to time out and
// return a Error with Timeout() == true after a fixed time limit; see
// SetDeadline and SetReadDeadline.
//
// Part of the net.Conn interface.
func (c *Conn) Read(b []byte) (n int, err error) {
// In order to reconcile the differences between the record abstraction of
// our AEAD connection, and the stream abstraction of TCP, we maintain an
// intermediate read buffer. If this buffer becomes depleated, then we read
// the next record, and feed it into the buffer. Otherwise, we read
// directly from the buffer.
if c.readBuf.Len() == 0 {
plaintext, err := c.noise.ReadMessage(c.conn)
if err != nil {
return 0, err
}
if _, err := c.readBuf.Write(plaintext); err != nil {
return 0, err
}
}
return c.readBuf.Read(b)
}
// Write writes data to the connection. Write can be made to time out and
// return a Error with Timeout() == true after a fixed time limit; see
// SetDeadline and SetWriteDeadline.
//
// Part of the net.Conn interface.
func (c *Conn) Write(b []byte) (n int, err error) {
return len(b), c.noise.WriteMessage(c.conn, b)
}
// Close closes the connection. Any blocked Read or Write operations will be
// unblocked and return errors.
//
// Part of the net.Conn interface.
func (c *Conn) Close() error {
// TODO(roasbeef): reset brontide state?
return c.conn.Close()
}
// LocalAddr returns the local network address.
//
// Part of the net.Conn interface.
func (c *Conn) LocalAddr() net.Addr {
return c.conn.LocalAddr()
}
// RemoteAddr returns the remote network address.
//
// Part of the net.Conn interface.
func (c *Conn) RemoteAddr() net.Addr {
return c.conn.RemoteAddr()
}
// SetDeadline sets the read and write deadlines associated with the
// connection. It is equivalent to calling both SetReadDeadline and
// SetWriteDeadline.
//
// Part of the net.Conn interface.
func (c *Conn) SetDeadline(t time.Time) error {
return c.conn.SetDeadline(t)
}
// SetReadDeadline sets the deadline for future Read calls. A zero value for t
// means Read will not time out.
//
// Part of the net.Conn interface.
func (c *Conn) SetReadDeadline(t time.Time) error {
return c.conn.SetReadDeadline(t)
}
// SetWriteDeadline sets the deadline for future Write calls. Even if write
// times out, it may return n > 0, indicating that some of the data was
// successfully written. A zero value for t means Write will not time out.
//
// Part of the net.Conn interface.
func (c *Conn) SetWriteDeadline(t time.Time) error {
return c.conn.SetWriteDeadline(t)
}
// RemotePub returns the remote peer's static public key.
func (c *Conn) RemotePub() *btcec.PublicKey {
return c.noise.remoteStatic
}
// LocalPub returns the local peer's static public key.
func (c *Conn) LocalPub() *btcec.PublicKey {
return c.noise.localStatic.PubKey()
}

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package brontide
import (
"io"
"net"
"github.com/roasbeef/btcd/btcec"
)
// Listener is an implementation of a net.Conn which executes an authenticated
// key exchange and message encryption protocol dubeed "BrontideMachine" after
// initial connection acceptance. See the BrontideMachine struct for additional
// details w.r.t the handshake and encryption scheme used within the
// connection.
type Listener struct {
localStatic *btcec.PrivateKey
tcp *net.TCPListener
}
// A compile-time assertion to ensure that Conn meets the net.Listener interface.
var _ net.Listener = (*Listener)(nil)
// NewListener returns a new net.Listener which enforces the Brontide scheme
// during both initial connection establishment and data transfer.
func NewListener(localStatic *btcec.PrivateKey, listenAddr string) (*Listener,
error) {
addr, err := net.ResolveTCPAddr("tcp", listenAddr)
if err != nil {
return nil, err
}
l, err := net.ListenTCP("tcp", addr)
if err != nil {
return nil, err
}
return &Listener{
localStatic: localStatic,
tcp: l,
}, nil
}
// Accept waits for and returns the next connection to the listener. All
// incoming connections are authenticated via the three act Brontide
// key-exchange scheme. This funciton will fail with a non-nil error in the
// case that either the handhska breaks down, or the remote peer doesn't know
// our static public key.
//
// Part of the net.Listener interface.
func (l *Listener) Accept() (net.Conn, error) {
conn, err := l.tcp.Accept()
if err != nil {
return nil, err
}
brontideConn := &Conn{
conn: conn,
noise: NewBrontideMachine(false, l.localStatic, nil),
}
// Attempt to carry out the first act of the handshake protocol. If the
// connecting node doesn't know our long-term static public key, then
// this portion will fail with a non-nil error.
var actOne [ActOneSize]byte
if _, err := io.ReadFull(conn, actOne[:]); err != nil {
return nil, err
}
if err := brontideConn.noise.RecvActOne(actOne); err != nil {
return nil, err
}
// Next, progress the handshake processes by sending over our ephemeral
// key for the session along with an authenticating tag.
actTwo, err := brontideConn.noise.GenActTwo()
if err != nil {
return nil, err
}
if _, err := conn.Write(actTwo[:]); err != nil {
return nil, err
}
// Finally, finish the handhskae processes by reading and decrypting
// the conneciton peer's static public key. If this succeeeds then both
// sides have mutually authenticated each other.
var actThree [ActThreeSize]byte
if _, err := io.ReadFull(conn, actThree[:]); err != nil {
return nil, err
}
if err := brontideConn.noise.RecvActThree(actThree); err != nil {
return nil, err
}
return brontideConn, nil
}
// Close closes the listener. Any blocked Accept operations will be unblocked
// and return errors.
//
// Part of the net.Listener interface.
func (l *Listener) Close() error {
return l.tcp.Close()
}
// Addr returns the listener's network address.
//
// Part of the net.Listener interface.
func (l *Listener) Addr() net.Addr {
return l.tcp.Addr()
}

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brontide/noise.go Normal file
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package brontide
import (
"crypto/cipher"
"crypto/sha256"
"encoding/binary"
"io"
"golang.org/x/crypto/hkdf"
"github.com/aead/chacha20"
"github.com/roasbeef/btcd/btcec"
)
const (
// protocolName is the precise instantiation of the Noise protocol
// handshake at the center of Brontide. This value will be used as part
// of the prologue. If the initiator and responder aren't using the
// exact same string for this value, along with prologue of the Bitcoin
// network, then the initial handshake will fail.
protocolName = "Noise_XK_secp256k1_ChaChaPoly_SHA256"
)
// TODO(roasbeef): free buffer pool?
// cipherState encapsulates the state for the AEAD which will be used to
// encrypt+authenticate any payloads sent during the handshake, and messages
// sent once the handshake has completed.
type cipherState struct {
// nonce is the nonce passed into the chacha20-poly1305 instance for
// encryption+decryption. The nonce is incremented after each succesful
// encryption/decryption.
//
// TODO(roasbeef): this should actually be 96 bit
nonce uint64
// secretKey is the shared symmetric key which will be used to
// instantiate the cipher.
//
// TODO(roasbeef): m-lock??
secretKey [32]byte
// cipher is an instance of the ChaCha20-Poly1305 AEAD construction
// created using the secretKey above.
cipher cipher.AEAD
}
// Encrypt returns a ciphertext which is the encryption of the plainText
// observing the passed associatedData within the AEAD construction.
func (c *cipherState) Encrypt(associatedData, cipherText, plainText []byte) []byte {
defer func() {
c.nonce++
}()
var nonce [12]byte
binary.LittleEndian.PutUint64(nonce[:], c.nonce)
return c.cipher.Seal(cipherText, nonce[:], plainText, associatedData)
}
// Decrypt attempts to decrypt the passed ciphertext observing the specified
// associatedData within the AEAD construction. In the case that the final MAC
// check fails, then a non-nil error will be returned.
func (c *cipherState) Decrypt(associatedData, plainText, cipherText []byte) ([]byte, error) {
defer func() {
c.nonce++
}()
var nonce [12]byte
binary.LittleEndian.PutUint64(nonce[:], c.nonce)
return c.cipher.Open(plainText, nonce[:], cipherText, associatedData)
}
// InitializeKey initializes the secret key and AEAD cipher scheme based off of
// the passed key.
func (c *cipherState) InitializeKey(key [32]byte) {
c.secretKey = key
c.nonce = 0
c.cipher = chacha20.NewChaCha20Poly1305(&c.secretKey)
}
// symmetricState encapsulates a cipherState object and houses the ephemeral
// handshake digest state. This struct is used during the handshake to derive
// new shared secrets based off of the result of ECDH operations. Ultimately,
// the final key yielded by this struct is the result of an incremental
// Triple-DH operation.
type symmetricState struct {
cipherState
// chainingKey is used as the salt to the HKDF function to derive a new
// chaining key as well as a new tempKey which is used for
// encryption/decryption.
chainingKey [32]byte
// tempKey is the latter 32 bytes resulted from the latest HKDF
// iteration. This key is used to encrypt/decrypt any handshake
// messages or payloads sent until the next DH operation is executed.
tempKey [32]byte
// handshakeDigest is the cummulative hash digest of all handshake
// messages sent from start to finish. This value is never transmitted
// to the other side, but will be used as the AD when
// encrypting/decrypting messages using our AEAD construction.
handshakeDigest [32]byte
}
// mixKey is implements a basic HKDF-based key rachet. This method is called
// with the result of each DH output generated during the handshake process.
// The first 32 bytes extract from the HKDF reader is the next chaining key,
// then latter 32 bytes become the temp secret key using within any future AEAD
// operations until another DH operation is performed.
func (s *symmetricState) mixKey(input []byte) {
var info []byte
secret := input
salt := s.chainingKey
h := hkdf.New(sha256.New, secret, salt[:], info)
// hkdf(input, ck, zero)
// |
// | \
// | \
// ck k
h.Read(s.chainingKey[:])
h.Read(s.tempKey[:])
// cipher.k = temp_key
s.InitializeKey(s.tempKey)
}
// mixHash hashes the passed input data into the cummulative handshake digest.
// The running result of this value (h) is used as the associated data in all
// decryption/encryption operations.
func (s *symmetricState) mixHash(data []byte) {
h := sha256.New()
h.Write(s.handshakeDigest[:])
h.Write(data)
copy(s.handshakeDigest[:], h.Sum(nil))
}
// EncryptAndHash returns the authenticated encryption of the passed plaintext.
// When encrypting the handshake digest (h) is used as the associated data to
// the AEAD cipher.
func (s *symmetricState) EncryptAndHash(plaintext []byte) []byte {
ciphertext := s.Encrypt(s.handshakeDigest[:], nil, plaintext)
s.mixHash(ciphertext)
return ciphertext
}
// DecryptAndHash returns the authenticated decryption of the passed
// ciphertext. When encrypting the handshake digest (h) is used as the
// associated data to the AEAD cipher.
func (s *symmetricState) DecryptAndHash(ciphertext []byte) ([]byte, error) {
plaintext, err := s.Decrypt(s.handshakeDigest[:], nil, ciphertext)
if err != nil {
return nil, err
}
s.mixHash(ciphertext)
return plaintext, nil
}
// InitializeSymmetric initializes the symmetric state by setting the handshake
// digest (h) and the chaining key (ck) to protocol name.
func (s *symmetricState) InitializeSymmetric(protocolName []byte) {
var empty [32]byte
s.handshakeDigest = sha256.Sum256(protocolName)
s.chainingKey = s.handshakeDigest
s.InitializeKey(empty)
}
// handshakeState encapsulates the symmetricState and keeps track of all the
// public keys (static and ephemeral) for both sides during the handshake
// transscript. If the handshake completes successfuly, then two instances of a
// cipherState are emitted: one to encrypt messages from initiator to
// responder, and the other for the opposite direction.
type handshakeState struct {
symmetricState
initiator bool
localStatic *btcec.PrivateKey
localEphemeral *btcec.PrivateKey
remoteStatic *btcec.PublicKey
remoteEphemeral *btcec.PublicKey
}
// newHandshakeState returns a new instance of the handshake state initialized
// with the prologue and protocol name. If this is the respodner's handshake
// state, then the remotePub can be nil.
func newHandshakeState(initiator bool, prologue []byte,
localPub *btcec.PrivateKey, remotePub *btcec.PublicKey) handshakeState {
h := handshakeState{
initiator: initiator,
localStatic: localPub,
remoteStatic: remotePub,
}
// Set the current chainking key and handshake digest to the hash of
// the protocol name, and additionally mix in the prologue. If either
// sides disagree about the prologue or protocol name, then the
// handshake will fail.
h.InitializeSymmetric([]byte(protocolName))
h.mixHash(prologue)
// In Noise_XK, then initiator should know the responder's static
// public key, therefore we include the responder's static key in the
// handshake digest. If the initiator gets this value wrong, then the
// handshake will fail.
if initiator {
h.mixHash(remotePub.SerializeCompressed())
} else {
h.mixHash(localPub.PubKey().SerializeCompressed())
}
return h
}
// BrontideMachine 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
// initial 3-act handshake has completed all messages are encrypted with a
// chacha20 AEAD cipher. On the wire, all messages are prefixed with an
// authenticated+encrypted length field. Additionally, the encrypted+auth'd
// length prefix is used as the AD when encrypting+decryption messages. This
// construction provides confidentiallity of packet length, avoids introducing
// a padding-oracle, and binds the encrypted packet length to the packet
// itself.
//
// The acts proceeds the following order (initiator on the left):
// GenActOne() ->
// RecvActOne()
// <- GenActTwo()
// RecvActTwo()
// GenActThree() ->
// RecvActThree()
//
// This exchange corresponds to the following Noise handshake:
// <- s
// ...
// -> e, es
// <- e, ee
// -> s, se
type BrontideMachine struct {
sendCipher cipherState
recvCipher cipherState
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.
func NewBrontideMachine(initiator bool, localPub *btcec.PrivateKey,
remotePub *btcec.PublicKey) *BrontideMachine {
handshake := newHandshakeState(initiator, []byte("bitcoin"), localPub,
remotePub)
return &BrontideMachine{handshakeState: handshake}
}
const (
// ActOneSize is the size of the packet sent from initiator to
// responder in ActOne. The packet consists of an ephemeral key in
// compressed format, and a 16-byte poly1305 tag.
//
// 33 + 16
ActOneSize = 49
// ActTwoSize is the size the packet sent from responder to initiator
// in ActTwo. The packet consists of an ephemeral key in compressed
// format and a 16-byte poly1305 tag.
//
// 33 + 16
ActTwoSize = 49
// ActThreeSize is the size of the packet sent from initiator to
// responder in ActThree. The packet consists of the initiators static
// key encrypted with strong forward secrecy and a 16-byte poly1035
// tag.
//
// 33 + 16 + 16
ActThreeSize = 65
)
// GenActOne generates the initial packet (act one) to be sent from initiator
// to responder. During act one the initiator generates a fresh ephemeral key,
// hashes it into the handshake digest, and performs an ECDH between this key
// and the responder's static key. Future payloads are encrypted with a key
// dervied from this result.
//
// -> e, es
func (b *BrontideMachine) GenActOne() ([ActOneSize]byte, error) {
var (
err error
actOne [ActOneSize]byte
)
// e
b.localEphemeral, err = btcec.NewPrivateKey(btcec.S256())
if err != nil {
return actOne, err
}
ephemeral := b.localEphemeral.PubKey().SerializeCompressed()
b.mixHash(ephemeral)
// es
s := btcec.GenerateSharedSecret(b.localEphemeral, b.remoteStatic)
b.mixKey(s)
authPayload := b.EncryptAndHash([]byte{})
copy(actOne[:33], ephemeral)
copy(actOne[33:], authPayload)
return actOne, nil
}
// RecvActOne processes the act one packet sent by the initiator. The responder
// executes the mirroed actions to that of the initiator extending the
// handshake digest and deriving a new shared secret based on a ECDH with the
// initiator's ephemeral key and reponder's static key.
func (b *BrontideMachine) RecvActOne(actOne [ActOneSize]byte) error {
var (
err error
e [33]byte
p [16]byte
)
copy(e[:], actOne[:33])
copy(p[:], actOne[33:])
// e
b.remoteEphemeral, err = btcec.ParsePubKey(e[:], btcec.S256())
if err != nil {
return err
}
b.mixHash(b.remoteEphemeral.SerializeCompressed())
// es
s := btcec.GenerateSharedSecret(b.localStatic, b.remoteEphemeral)
b.mixKey(s)
// If the initiator doesn't know our static key, then this operation
// will fail.
if _, err := b.DecryptAndHash(p[:]); err != nil {
return err
}
return nil
}
// GenActTwo generates the second packet (act two) to be sent from the
// responder to the initiator. The packet for act two is identify to that of
// act one, but then results in a different ECDH operation between the
// initiator's and responder's ephemeral keys.
//
// <- e, ee
func (b *BrontideMachine) GenActTwo() ([ActTwoSize]byte, error) {
var (
err error
actTwo [ActTwoSize]byte
)
// e
b.localEphemeral, err = btcec.NewPrivateKey(btcec.S256())
if err != nil {
return actTwo, err
}
ephemeral := b.localEphemeral.PubKey().SerializeCompressed()
b.mixHash(b.localEphemeral.PubKey().SerializeCompressed())
// ee
s := btcec.GenerateSharedSecret(b.localEphemeral, b.remoteEphemeral)
b.mixKey(s)
authPayload := b.EncryptAndHash([]byte{})
copy(actTwo[:33], ephemeral)
copy(actTwo[33:], authPayload)
return actTwo, nil
}
// RecvActTwo processes the second packet (act two) sent from the responder to
// the initiator. A succesful processing of this packet authenticates the
// initiator to the responder.
func (b *BrontideMachine) RecvActTwo(actTwo [ActTwoSize]byte) error {
var (
err error
e [33]byte
p [16]byte
)
copy(e[:], actTwo[:33])
copy(p[:], actTwo[33:])
// e
b.remoteEphemeral, err = btcec.ParsePubKey(e[:], btcec.S256())
if err != nil {
return err
}
b.mixHash(b.remoteEphemeral.SerializeCompressed())
// ee
s := btcec.GenerateSharedSecret(b.localEphemeral, b.remoteEphemeral)
b.mixKey(s)
if _, err := b.DecryptAndHash(p[:]); err != nil {
return err
}
return nil
}
// GenActThree creates the final (act three) packet of the handshake. Act three
// is to be sent from the initiator to the responder. The purpose of act three
// is to transmit the initiator's public key under strong forwad secrecy to the
// responder. This act also includes the final ECDH operation which yields the
// final session.
//
// -> s, se
func (b *BrontideMachine) GenActThree() ([ActThreeSize]byte, error) {
var actThree [ActThreeSize]byte
ourPubkey := b.localStatic.PubKey().SerializeCompressed()
ciphertext := b.EncryptAndHash(ourPubkey)
s := btcec.GenerateSharedSecret(b.localStatic, b.remoteEphemeral)
b.mixKey(s)
authPayload := b.EncryptAndHash([]byte{})
copy(actThree[:49], ciphertext)
copy(actThree[49:], authPayload)
// With the final ECDH operation complete, derive the session sending
// and receiving keys.
b.split()
return actThree, nil
}
// RecvActThree processes the final act (act three) sent from the initiator to
// the responder. After processing this act, the responder learns of the
// initiators's static public key. Decryption of the static key serves to
// authenticate the initiator to the responder.
func (b *BrontideMachine) RecvActThree(actThree [ActThreeSize]byte) error {
var (
err error
s [33 + 16]byte
p [16]byte
)
copy(s[:], actThree[:33+16])
copy(p[:], actThree[33+16:])
// s
remotePub, err := b.DecryptAndHash(s[:])
if err != nil {
return err
}
b.remoteStatic, err = btcec.ParsePubKey(remotePub, btcec.S256())
if err != nil {
return err
}
// se
se := btcec.GenerateSharedSecret(b.localEphemeral, b.remoteStatic)
b.mixKey(se)
if _, err := b.DecryptAndHash(p[:]); err != nil {
return err
}
// With the final ECDH operation complete, derive the session sending
// and receiving keys.
b.split()
return nil
}
// split is the final wrap-up act to be executed at the end of a succesful
// three act handshake. This function creates to internal cipherState
// instances: one which is used to encrypt messages from the initiator to the
// responder, and another which is used to encrypt message for the opposite
// direction.
func (b *BrontideMachine) split() {
var (
empty []byte
sendKey [32]byte
recvKey [32]byte
)
h := hkdf.New(sha256.New, b.chainingKey[:], empty, empty)
// If we're the initiator the the frist 32 bytes are used to encrypt
// our messages and the second 32-bytes to decrypt their messages. For
// the responder the opposite is true.
if b.initiator {
h.Read(sendKey[:])
b.sendCipher = cipherState{}
b.sendCipher.InitializeKey(sendKey)
h.Read(recvKey[:])
b.recvCipher = cipherState{}
b.recvCipher.InitializeKey(recvKey)
} else {
h.Read(recvKey[:])
b.recvCipher = cipherState{}
b.recvCipher.InitializeKey(recvKey)
h.Read(sendKey[:])
b.sendCipher = cipherState{}
b.sendCipher.InitializeKey(sendKey)
}
}
// WriteMessage writes the next message p to the passed io.Writer. The
// ciphertext of the message is pre-pended with an encrypt+auth'd length which
// must be used as the AD to the AEAD construction when being decrypted by the
// other side.
func (b *BrontideMachine) WriteMessage(w io.Writer, p []byte) error {
// The full length of the packet includes the 16 byte MAC.
fullLength := uint64(len(p) + 16)
// TODO(roasbeef): The Summit decided on 24 bits?
var pktLen [8]byte
binary.BigEndian.PutUint64(pktLen[:], fullLength)
// First, write out the encrypted+MAC'd length prefix for the packet.
cipherLen := b.sendCipher.Encrypt(nil, nil, pktLen[:])
if _, err := w.Write(cipherLen); err != nil {
return err
}
// Next, write out the encrypted packet itself. We use the encrypted
// packet length above as the AD to the cipher in order to bind both
// messages together thwarting an active attack.
cipherText := b.sendCipher.Encrypt(cipherLen, nil, p)
if _, err := w.Write(cipherText); err != nil {
return err
}
return nil
}
// ReadMessage attemps to read the next message from the passed io.Reader. In
// the case of an authentication error, a non-nil error is returned.
func (b *BrontideMachine) ReadMessage(r io.Reader) ([]byte, error) {
var cipherLen [8 + 16]byte
if _, err := io.ReadFull(r, cipherLen[:]); err != nil {
return nil, err
}
// Attempt to decrypt+auth the packet length present in the stream.
pktLenBytes, err := b.recvCipher.Decrypt(nil, nil, cipherLen[:])
if err != nil {
return nil, err
}
// Next, using the length read from the packet header, read the
// encrypted packet itself.
pktLen := binary.BigEndian.Uint64(pktLenBytes)
ciperText := make([]byte, pktLen)
if _, err := io.ReadFull(r, ciperText[:]); err != nil {
return nil, err
}
// Finally, return the decrypted packet ensuring that the encrypted
// packet length is authenticated along with the packet itself.
return b.recvCipher.Decrypt(cipherLen[:], nil, ciperText)
}
// TODO(roasbeef): key rotation

98
brontide/noise_test.go Normal file
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@ -0,0 +1,98 @@
package brontide
import (
"bytes"
"net"
"testing"
"github.com/roasbeef/btcd/btcec"
)
func TestConnectionCorrectness(t *testing.T) {
// First, generate the long-term private keys both ends of the connection
// within our test.
localPriv, err := btcec.NewPrivateKey(btcec.S256())
if err != nil {
t.Fatalf("unable to generate local priv key: %v", err)
}
remotePriv, err := btcec.NewPrivateKey(btcec.S256())
if err != nil {
t.Fatalf("unable to generate remote priv key: %v", err)
}
// Having a port of ":0" means a random port, and interface will be
// chosen for our listener.
addr := ":0"
// Our listener will be local, and the connection remote.
listener, err := NewListener(localPriv, addr)
if err != nil {
t.Fatalf("unable to create listener: %v", err)
}
defer listener.Close()
listenAddr := listener.Addr().String()
// Initiate a connection with a separate goroutine, and listen with our
// main one. If both errors are nil, then encryption+auth was succesful.
errChan := make(chan error)
connChan := make(chan net.Conn)
go func() {
conn, err := Dial(remotePriv, localPriv.PubKey(), listenAddr)
errChan <- err
connChan <- conn
}()
localConn, listenErr := listener.Accept()
if listenErr != nil {
t.Fatalf("unable to accept connection: %v", listenErr)
}
if dialErr := <-errChan; err != nil {
t.Fatalf("unable to establish connection: %v", dialErr)
}
conn := <-connChan
// Test out some message full-message reads.
for i := 0; i < 10; i++ {
msg := []byte("hello" + string(i))
if _, err := conn.Write(msg); err != nil {
t.Fatalf("remote conn failed to write: %v", err)
}
readBuf := make([]byte, len(msg))
if _, err := localConn.Read(readBuf); err != nil {
t.Fatalf("local conn failed to read: %v", err)
}
if !bytes.Equal(readBuf, msg) {
t.Fatalf("messages don't match, %v vs %v",
string(readBuf), string(msg))
}
}
// Now try incremental message reads. This simulates first writing a
// message header, then a message body.
outMsg := []byte("hello world")
if _, err := conn.Write(outMsg); err != nil {
t.Fatalf("remote conn failed to write: %v", err)
}
readBuf := make([]byte, len(outMsg))
if _, err := localConn.Read(readBuf[:len(outMsg)/2]); err != nil {
t.Fatalf("local conn failed to read: %v", err)
}
if _, err := localConn.Read(readBuf[len(outMsg)/2:]); err != nil {
t.Fatalf("local conn failed to read: %v", err)
}
if !bytes.Equal(outMsg, readBuf) {
t.Fatalf("messages don't match, %v vs %v",
string(readBuf), string(outMsg))
}
}
func TestNoiseIdentityHiding(t *testing.T) {
// TODO(roasbeef): fin
}