From 511fdb2520d865841546f624e1ff7a1d370375ac Mon Sep 17 00:00:00 2001
From: nsa <elzeigel@gmail.com>
Date: Thu, 30 Jan 2020 13:35:27 -0500
Subject: [PATCH] fuzz/brontide: add fuzzing helper utilities

---
 fuzz/brontide/fuzz_utils.go | 137 ++++++++++++++++++++++++++++++++++++
 1 file changed, 137 insertions(+)
 create mode 100644 fuzz/brontide/fuzz_utils.go

diff --git a/fuzz/brontide/fuzz_utils.go b/fuzz/brontide/fuzz_utils.go
new file mode 100644
index 00000000..48388dc0
--- /dev/null
+++ b/fuzz/brontide/fuzz_utils.go
@@ -0,0 +1,137 @@
+// +build gofuzz
+
+package brontidefuzz
+
+import (
+	"encoding/hex"
+	"fmt"
+
+	"github.com/btcsuite/btcd/btcec"
+	"github.com/davecgh/go-spew/spew"
+	"github.com/lightningnetwork/lnd/brontide"
+)
+
+var (
+	initBytes = []byte{
+		0x81, 0xb6, 0x37, 0xd8, 0xfc, 0xd2, 0xc6, 0xda,
+		0x63, 0x59, 0xe6, 0x96, 0x31, 0x13, 0xa1, 0x17,
+		0xd, 0xe7, 0x95, 0xe4, 0xb7, 0x25, 0xb8, 0x4d,
+		0x1e, 0xb, 0x4c, 0xfd, 0x9e, 0xc5, 0x8c, 0xe9,
+	}
+
+	respBytes = []byte{
+		0xaa, 0xb6, 0x37, 0xd9, 0xfc, 0xd2, 0xc6, 0xda,
+		0x63, 0x59, 0xe6, 0x99, 0x31, 0x13, 0xa1, 0x17,
+		0xd, 0xe7, 0x95, 0xe9, 0xb7, 0x25, 0xb8, 0x4d,
+		0x1e, 0xb, 0x4c, 0xf9, 0x9e, 0xc5, 0x8c, 0xe9,
+	}
+
+	// Returns the initiator's ephemeral private key.
+	initEphemeral = brontide.EphemeralGenerator(func() (*btcec.PrivateKey, error) {
+		e := "121212121212121212121212121212121212121212121212121212" +
+			"1212121212"
+		eBytes, err := hex.DecodeString(e)
+		if err != nil {
+			return nil, err
+		}
+
+		priv, _ := btcec.PrivKeyFromBytes(btcec.S256(), eBytes)
+		return priv, nil
+	})
+
+	// Returns the responder's ephemeral private key.
+	respEphemeral = brontide.EphemeralGenerator(func() (*btcec.PrivateKey, error) {
+		e := "222222222222222222222222222222222222222222222222222" +
+			"2222222222222"
+		eBytes, err := hex.DecodeString(e)
+		if err != nil {
+			return nil, err
+		}
+
+		priv, _ := btcec.PrivKeyFromBytes(btcec.S256(), eBytes)
+		return priv, nil
+	})
+)
+
+// completeHandshake takes two brontide machines (initiator, responder)
+// and completes the brontide handshake between them. If any part of the
+// handshake fails, this function will panic.
+func completeHandshake(initiator, responder *brontide.Machine) {
+	if err := handshake(initiator, responder); err != nil {
+		nilAndPanic(initiator, responder, err)
+	}
+}
+
+// handshake actually completes the brontide handshake and bubbles up
+// an error to the calling function.
+func handshake(initiator, responder *brontide.Machine) error {
+	// Generate ActOne and send to the responder.
+	actOne, err := initiator.GenActOne()
+	if err != nil {
+		return err
+	}
+
+	if err := responder.RecvActOne(actOne); err != nil {
+		return err
+	}
+
+	// Generate ActTwo and send to initiator.
+	actTwo, err := responder.GenActTwo()
+	if err != nil {
+		return err
+	}
+
+	if err := initiator.RecvActTwo(actTwo); err != nil {
+		return err
+	}
+
+	// Generate ActThree and send to responder.
+	actThree, err := initiator.GenActThree()
+	if err != nil {
+		return err
+	}
+
+	return responder.RecvActThree(actThree)
+}
+
+// nilAndPanic first nils the initiator and responder's Curve fields and then
+// panics.
+func nilAndPanic(initiator, responder *brontide.Machine, err error) {
+	if initiator != nil {
+		initiator.SetCurveToNil()
+	}
+	if responder != nil {
+		responder.SetCurveToNil()
+	}
+	panic(fmt.Errorf("error: %v, initiator: %v, responder: %v", err,
+		spew.Sdump(initiator), spew.Sdump(responder)))
+}
+
+// getBrontideMachines returns two brontide machines that use random keys
+// everywhere.
+func getBrontideMachines() (*brontide.Machine, *brontide.Machine) {
+	initPriv, _ := btcec.NewPrivateKey(btcec.S256())
+	respPriv, _ := btcec.NewPrivateKey(btcec.S256())
+	respPub := (*btcec.PublicKey)(&respPriv.PublicKey)
+
+	initiator := brontide.NewBrontideMachine(true, initPriv, respPub)
+	responder := brontide.NewBrontideMachine(false, respPriv, nil)
+
+	return initiator, responder
+}
+
+// getStaticBrontideMachines returns two brontide machines that use static keys
+// everywhere.
+func getStaticBrontideMachines() (*brontide.Machine, *brontide.Machine) {
+	initPriv, _ := btcec.PrivKeyFromBytes(btcec.S256(), initBytes)
+	respPriv, respPub := btcec.PrivKeyFromBytes(btcec.S256(), respBytes)
+
+	initiator := brontide.NewBrontideMachine(
+		true, initPriv, respPub, initEphemeral,
+	)
+	responder := brontide.NewBrontideMachine(
+		false, respPriv, nil, respEphemeral,
+	)
+
+	return initiator, responder
+}