device: uniformly check ECDH output for zeros
For some reason, this was omitted for response messages.
Reported-by: z <dzm@unexpl0.red>
Fixes: 8c34c4c
("First set of code review patches")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
parent
1e2c3e5a3c
commit
c7b76d3d9e
@ -265,7 +265,7 @@ func (device *Device) SetPrivateKey(sk NoisePrivateKey) error {
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expiredPeers := make([]*Peer, 0, len(device.peers.keyMap))
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for _, peer := range device.peers.keyMap {
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handshake := &peer.handshake
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handshake.precomputedStaticStatic = device.staticIdentity.privateKey.sharedSecret(handshake.remoteStatic)
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handshake.precomputedStaticStatic, _ = device.staticIdentity.privateKey.sharedSecret(handshake.remoteStatic)
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expiredPeers = append(expiredPeers, peer)
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}
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@ -9,6 +9,7 @@ import (
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"crypto/hmac"
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"crypto/rand"
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"crypto/subtle"
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"errors"
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"hash"
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"golang.org/x/crypto/blake2s"
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@ -94,9 +95,14 @@ func (sk *NoisePrivateKey) publicKey() (pk NoisePublicKey) {
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return
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}
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func (sk *NoisePrivateKey) sharedSecret(pk NoisePublicKey) (ss [NoisePublicKeySize]byte) {
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var errInvalidPublicKey = errors.New("invalid public key")
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func (sk *NoisePrivateKey) sharedSecret(pk NoisePublicKey) (ss [NoisePublicKeySize]byte, err error) {
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apk := (*[NoisePublicKeySize]byte)(&pk)
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ask := (*[NoisePrivateKeySize]byte)(sk)
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curve25519.ScalarMult(&ss, ask, apk)
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return ss
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if isZero(ss[:]) {
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return ss, errInvalidPublicKey
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}
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return ss, nil
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}
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@ -175,8 +175,6 @@ func init() {
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}
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func (device *Device) CreateMessageInitiation(peer *Peer) (*MessageInitiation, error) {
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errZeroECDHResult := errors.New("ECDH returned all zeros")
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device.staticIdentity.RLock()
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defer device.staticIdentity.RUnlock()
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@ -204,9 +202,9 @@ func (device *Device) CreateMessageInitiation(peer *Peer) (*MessageInitiation, e
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handshake.mixHash(msg.Ephemeral[:])
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// encrypt static key
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ss := handshake.localEphemeral.sharedSecret(handshake.remoteStatic)
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if isZero(ss[:]) {
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return nil, errZeroECDHResult
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ss, err := handshake.localEphemeral.sharedSecret(handshake.remoteStatic)
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if err != nil {
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return nil, err
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}
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var key [chacha20poly1305.KeySize]byte
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KDF2(
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@ -221,7 +219,7 @@ func (device *Device) CreateMessageInitiation(peer *Peer) (*MessageInitiation, e
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// encrypt timestamp
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if isZero(handshake.precomputedStaticStatic[:]) {
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return nil, errZeroECDHResult
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return nil, errInvalidPublicKey
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}
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KDF2(
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&handshake.chainKey,
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@ -264,11 +262,10 @@ func (device *Device) ConsumeMessageInitiation(msg *MessageInitiation) *Peer {
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mixKey(&chainKey, &InitialChainKey, msg.Ephemeral[:])
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// decrypt static key
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var err error
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var peerPK NoisePublicKey
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var key [chacha20poly1305.KeySize]byte
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ss := device.staticIdentity.privateKey.sharedSecret(msg.Ephemeral)
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if isZero(ss[:]) {
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ss, err := device.staticIdentity.privateKey.sharedSecret(msg.Ephemeral)
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if err != nil {
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return nil
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}
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KDF2(&chainKey, &key, chainKey[:], ss[:])
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@ -384,12 +381,16 @@ func (device *Device) CreateMessageResponse(peer *Peer) (*MessageResponse, error
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handshake.mixHash(msg.Ephemeral[:])
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handshake.mixKey(msg.Ephemeral[:])
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func() {
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ss := handshake.localEphemeral.sharedSecret(handshake.remoteEphemeral)
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ss, err := handshake.localEphemeral.sharedSecret(handshake.remoteEphemeral)
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if err != nil {
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return nil, err
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}
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handshake.mixKey(ss[:])
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ss = handshake.localEphemeral.sharedSecret(handshake.remoteStatic)
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ss, err = handshake.localEphemeral.sharedSecret(handshake.remoteStatic)
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if err != nil {
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return nil, err
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}
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handshake.mixKey(ss[:])
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}()
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// add preshared key
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@ -406,11 +407,9 @@ func (device *Device) CreateMessageResponse(peer *Peer) (*MessageResponse, error
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handshake.mixHash(tau[:])
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func() {
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aead, _ := chacha20poly1305.New(key[:])
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aead.Seal(msg.Empty[:0], ZeroNonce[:], nil, handshake.hash[:])
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handshake.mixHash(msg.Empty[:])
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}()
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handshake.state = handshakeResponseCreated
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@ -455,17 +454,19 @@ func (device *Device) ConsumeMessageResponse(msg *MessageResponse) *Peer {
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mixHash(&hash, &handshake.hash, msg.Ephemeral[:])
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mixKey(&chainKey, &handshake.chainKey, msg.Ephemeral[:])
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func() {
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ss := handshake.localEphemeral.sharedSecret(msg.Ephemeral)
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ss, err := handshake.localEphemeral.sharedSecret(msg.Ephemeral)
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if err != nil {
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return false
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}
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mixKey(&chainKey, &chainKey, ss[:])
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setZero(ss[:])
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}()
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func() {
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ss := device.staticIdentity.privateKey.sharedSecret(msg.Ephemeral)
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ss, err = device.staticIdentity.privateKey.sharedSecret(msg.Ephemeral)
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if err != nil {
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return false
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}
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mixKey(&chainKey, &chainKey, ss[:])
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setZero(ss[:])
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}()
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// add preshared key (psk)
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@ -483,7 +484,7 @@ func (device *Device) ConsumeMessageResponse(msg *MessageResponse) *Peer {
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// authenticate transcript
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aead, _ := chacha20poly1305.New(key[:])
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_, err := aead.Open(nil, ZeroNonce[:], msg.Empty[:], hash[:])
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_, err = aead.Open(nil, ZeroNonce[:], msg.Empty[:], hash[:])
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if err != nil {
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return false
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}
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@ -24,10 +24,10 @@ func TestCurveWrappers(t *testing.T) {
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pk1 := sk1.publicKey()
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pk2 := sk2.publicKey()
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ss1 := sk1.sharedSecret(pk2)
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ss2 := sk2.sharedSecret(pk1)
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ss1, err1 := sk1.sharedSecret(pk2)
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ss2, err2 := sk2.sharedSecret(pk1)
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if ss1 != ss2 {
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if ss1 != ss2 || err1 != nil || err2 != nil {
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t.Fatal("Failed to compute shared secet")
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}
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}
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@ -92,7 +92,7 @@ func (device *Device) NewPeer(pk NoisePublicKey) (*Peer, error) {
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// pre-compute DH
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handshake := &peer.handshake
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handshake.mutex.Lock()
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handshake.precomputedStaticStatic = device.staticIdentity.privateKey.sharedSecret(pk)
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handshake.precomputedStaticStatic, _ = device.staticIdentity.privateKey.sharedSecret(pk)
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handshake.remoteStatic = pk
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handshake.mutex.Unlock()
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