dex: implement recovery mechanism (#258)

* dex: implement recovery mechanism

The DEXON recovery protocol allows us to use the Ethereum blockchain as a
fallback consensus chain to coordinate recovery.

* fix

1 files changed, 484 insertions, 0 deletions

diff --git a/dex/recovery.go b/dex/recovery.go
new file mode 100644
index 000000000..cfc8ae203
--- /dev/null
+++ b/dex/recovery.go
@@ -0,0 +1,484 @@
+// Copyright 2018 The dexon-consensus Authors
+// This file is part of the dexon-consensus library.
+//
+// The dexon-consensus library is free software: you can redistribute it
+// and/or modify it under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation, either version 3 of the License,
+// or (at your option) any later version.
+//
+// The dexon-consensus library is distributed in the hope that it will be
+// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+// General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the dexon-consensus library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package dex
+
+import (
+	"crypto/ecdsa"
+	"encoding/hex"
+	"fmt"
+	"math/big"
+	"strconv"
+	"strings"
+
+	"github.com/dexon-foundation/dexon/accounts/abi"
+	"github.com/dexon-foundation/dexon/common"
+	"github.com/dexon-foundation/dexon/core/types"
+	"github.com/dexon-foundation/dexon/crypto"
+	"github.com/dexon-foundation/dexon/params"
+	"github.com/dexon-foundation/dexon/rlp"
+	"github.com/onrik/ethrpc"
+)
+
+const numConfirmation = 1
+
+const recoveryABI = `
+[
+  {
+    "constant": true,
+    "inputs": [
+      {
+        "name": "",
+        "type": "uint256"
+      },
+      {
+        "name": "",
+        "type": "address"
+      }
+    ],
+    "name": "voted",
+    "outputs": [
+      {
+        "name": "",
+        "type": "bool"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [],
+    "name": "renounceOwnership",
+    "outputs": [],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [],
+    "name": "owner",
+    "outputs": [
+      {
+        "name": "",
+        "type": "address"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [],
+    "name": "isOwner",
+    "outputs": [
+      {
+        "name": "",
+        "type": "bool"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [],
+    "name": "depositValue",
+    "outputs": [
+      {
+        "name": "",
+        "type": "uint256"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [
+      {
+        "name": "",
+        "type": "uint256"
+      },
+      {
+        "name": "",
+        "type": "uint256"
+      }
+    ],
+    "name": "votes",
+    "outputs": [
+      {
+        "name": "",
+        "type": "address"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [
+      {
+        "name": "",
+        "type": "address"
+      }
+    ],
+    "name": "withdrawable",
+    "outputs": [
+      {
+        "name": "",
+        "type": "uint256"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [
+      {
+        "name": "newOwner",
+        "type": "address"
+      }
+    ],
+    "name": "transferOwnership",
+    "outputs": [],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  },
+  {
+    "anonymous": false,
+    "inputs": [
+      {
+        "indexed": true,
+        "name": "height",
+        "type": "uint256"
+      },
+      {
+        "indexed": false,
+        "name": "voter",
+        "type": "address"
+      }
+    ],
+    "name": "VotedForRecovery",
+    "type": "event"
+  },
+  {
+    "anonymous": false,
+    "inputs": [
+      {
+        "indexed": true,
+        "name": "owner",
+        "type": "address"
+      },
+      {
+        "indexed": false,
+        "name": "amount",
+        "type": "uint256"
+      }
+    ],
+    "name": "Withdrawn",
+    "type": "event"
+  },
+  {
+    "anonymous": false,
+    "inputs": [
+      {
+        "indexed": true,
+        "name": "previousOwner",
+        "type": "address"
+      },
+      {
+        "indexed": true,
+        "name": "newOwner",
+        "type": "address"
+      }
+    ],
+    "name": "OwnershipTransferred",
+    "type": "event"
+  },
+  {
+    "constant": false,
+    "inputs": [
+      {
+        "name": "DepositValue",
+        "type": "uint256"
+      }
+    ],
+    "name": "setDeposit",
+    "outputs": [],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [
+      {
+        "name": "height",
+        "type": "uint256"
+      },
+      {
+        "name": "value",
+        "type": "uint256"
+      }
+    ],
+    "name": "refund",
+    "outputs": [],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [],
+    "name": "withdraw",
+    "outputs": [],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [
+      {
+        "name": "height",
+        "type": "uint256"
+      }
+    ],
+    "name": "voteForSkipBlock",
+    "outputs": [],
+    "payable": true,
+    "stateMutability": "payable",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [
+      {
+        "name": "height",
+        "type": "uint256"
+      }
+    ],
+    "name": "numVotes",
+    "outputs": [
+      {
+        "name": "",
+        "type": "uint256"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  }
+]
+`
+
+var abiObject abi.ABI
+
+func init() {
+	var err error
+	abiObject, err = abi.JSON(strings.NewReader(recoveryABI))
+	if err != nil {
+		panic(err)
+	}
+}
+
+type Recovery struct {
+	gov          *DexconGovernance
+	contract     common.Address
+	confirmation int
+	privateKey   *ecdsa.PrivateKey
+	nodeAddress  common.Address
+	client       *ethrpc.EthRPC
+}
+
+func NewRecovery(config *params.RecoveryConfig, networkRPC string,
+	gov *DexconGovernance, privKey *ecdsa.PrivateKey) *Recovery {
+	client := ethrpc.New(networkRPC)
+	return &Recovery{
+		gov:          gov,
+		contract:     config.Contract,
+		confirmation: config.Confirmation,
+		privateKey:   privKey,
+		nodeAddress:  crypto.PubkeyToAddress(privKey.PublicKey),
+		client:       client,
+	}
+}
+
+func (r *Recovery) genVoteForSkipBlockTx(height uint64) (*types.Transaction, error) {
+	netVersion, err := r.client.NetVersion()
+	if err != nil {
+		return nil, err
+	}
+
+	networkID, err := strconv.Atoi(netVersion)
+	if err != nil {
+		return nil, err
+	}
+
+	data, err := abiObject.Pack("depositValue")
+	if err != nil {
+		return nil, err
+	}
+
+	res, err := r.client.EthCall(ethrpc.T{
+		From: r.nodeAddress.String(),
+		To:   r.contract.String(),
+		Data: "0x" + hex.EncodeToString(data),
+	}, "latest")
+	if err != nil {
+		return nil, err
+	}
+
+	resBytes, err := hex.DecodeString(res[2:])
+	if err != nil {
+		return nil, err
+	}
+
+	var depositValue *big.Int
+	err = abiObject.Unpack(&depositValue, "depositValue", resBytes)
+	if err != nil {
+		return nil, err
+	}
+
+	data, err = abiObject.Pack("voteForSkipBlock", new(big.Int).SetUint64(height))
+	if err != nil {
+		return nil, err
+	}
+
+	gasPrice, err := r.client.EthGasPrice()
+	if err != nil {
+		return nil, err
+	}
+
+	nonce, err := r.client.EthGetTransactionCount(r.nodeAddress.String(), "pending")
+	if err != nil {
+		return nil, err
+	}
+
+	// Increase gasPrice to 3 times of suggested gas price to make sure it will
+	// be included in time.
+	useGasPrice := new(big.Int).Mul(&gasPrice, big.NewInt(3))
+
+	tx := types.NewTransaction(
+		uint64(nonce),
+		r.contract,
+		depositValue,
+		uint64(100000),
+		useGasPrice,
+		data)
+
+	signer := types.NewEIP155Signer(big.NewInt(int64(networkID)))
+	return types.SignTx(tx, signer, r.privateKey)
+}
+
+func (r *Recovery) ProposeSkipBlock(height uint64) error {
+	tx, err := r.genVoteForSkipBlockTx(height)
+	if err != nil {
+		return err
+	}
+
+	txData, err := rlp.EncodeToBytes(tx)
+	if err != nil {
+		return err
+	}
+	_, err = r.client.EthSendRawTransaction("0x" + hex.EncodeToString(txData))
+	return err
+}
+
+func (r *Recovery) Votes(height uint64) (uint64, error) {
+	data, err := abiObject.Pack("numVotes", new(big.Int).SetUint64(height))
+	if err != nil {
+		return 0, err
+	}
+
+	bn, err := r.client.EthBlockNumber()
+	if err != nil {
+		return 0, err
+	}
+
+	snapshotHeight := bn - numConfirmation
+
+	res, err := r.client.EthCall(ethrpc.T{
+		From: r.nodeAddress.String(),
+		To:   r.contract.String(),
+		Data: "0x" + hex.EncodeToString(data),
+	}, fmt.Sprintf("0x%x", snapshotHeight))
+	if err != nil {
+		return 0, err
+	}
+
+	resBytes, err := hex.DecodeString(res[2:])
+	if err != nil {
+		return 0, err
+	}
+
+	votes := new(big.Int)
+	err = abiObject.Unpack(&votes, "numVotes", resBytes)
+	if err != nil {
+		return 0, err
+	}
+
+	notarySet, err := r.gov.NotarySetAddresses(r.gov.Round())
+	if err != nil {
+		return 0, err
+	}
+
+	count := uint64(0)
+
+	for i := uint64(0); i < votes.Uint64(); i++ {
+		data, err = abiObject.Pack(
+			"votes", new(big.Int).SetUint64(height), new(big.Int).SetUint64(i))
+		if err != nil {
+			return 0, err
+		}
+
+		res, err = r.client.EthCall(ethrpc.T{
+			From: r.nodeAddress.String(),
+			To:   r.contract.String(),
+			Data: "0x" + hex.EncodeToString(data),
+		}, fmt.Sprintf("0x%x", snapshotHeight))
+		if err != nil {
+			return 0, err
+		}
+
+		resBytes, err := hex.DecodeString(res[2:])
+		if err != nil {
+			return 0, err
+		}
+
+		var addr common.Address
+		err = abiObject.Unpack(&addr, "votes", resBytes)
+		if err != nil {
+			return 0, err
+		}
+
+		if _, ok := notarySet[addr]; ok {
+			count += 1
+		}
+	}
+	return count, nil
+}