examples: Add salvage_webwallet.py.

This script is meant to enable someone who has an xpriv from an old
copay wallet to move their funds to a new wallet.

decred/examples/salvage_webwallet.py

@@ -0,0 +1,300 @@
+#!/usr/bin/env python3
+"""
+Copyright (c) 2020, The Decred developers
+
+This example script will dump all funds located in an account derived from the
+supplied xpriv seed to a specified address. It is meant to be used for the
+purpose of salvaging funds from an old copay wallet.
+
+dcrd must be running on the correct network with txindex and addrindex enabled
+in dcrd.conf. rpcuser and rpcpass must also be present in the config file.
+"""
+import os
+from urllib.parse import urlunsplit
+
+from base58 import b58decode
+from decred import DecredError
+from decred.crypto import crypto
+from decred.crypto.secp256k1.curve import curve as Curve
+from decred.dcr import account, addrlib, nets, rpc, txscript
+from decred.dcr.wire import msgtx, wire
+from decred.util import helpers
+from decred.util.encode import ByteArray
+
+
+SERIALIZED_KEY_LENGTH = 4 + 1 + 4 + 4 + 32 + 33  # 78 bytes
+INTERNAL = 0
+EXTERNAL = 1
+FEE_RATE = 10000
+GAP_LIMIT = 20
+ACCT_NUM = 0
+COIN_TYPE_OLD = 20
+COIN_TYPE_TESTNET = 1
+PURPOSE = 44
+
+
+def cfg(isTestnet):
+    dcrdCfgDir = helpers.appDataDir("dcrd")
+    cfgPath = os.path.join(dcrdCfgDir, "dcrd.conf")
+    if not os.path.isfile(cfgPath):
+        return None
+    cfg = helpers.readINI(cfgPath, ["rpcuser", "rpcpass", "rpccert", "addrindex", "txindex"])
+    assert "rpcuser" in cfg
+    assert "rpcpass" in cfg
+    if "addrindex" not in cfg or cfg["addrindex"] not in ("1", "true"):
+        raise DecredError("addrindex must be enabled")
+    if "txindex" not in cfg or cfg["txindex"] not in ("1", "true"):
+        raise DecredError("txindex must be enabled")
+    if "rpccert" not in cfg:
+        cfg["rpccert"] = os.path.join(dcrdCfgDir, "rpc.cert")
+    if "rpclisten" not in cfg:
+        cfg["rpclisten"] = "localhost:9109"
+    if isTestnet:
+        cfg["rpclisten"] = "localhost:19109"
+    return cfg
+
+
+def decodeExtendedKey(netParams, key):
+    """
+    Decode an base58 ExtendedKey using the passphrase and network parameters.
+
+    Args:
+        netParams (module): The network parameters.
+        key (str): Base-58 encoded extended key.
+
+    Returns:
+        ExtendedKey: The decoded key.
+    """
+    decoded = ByteArray(b58decode(key))
+    decoded_len = len(decoded)
+    if decoded_len != SERIALIZED_KEY_LENGTH + 4:
+        raise DecredError(f"decoded private key is wrong length: {decoded_len}")
+
+    # The serialized format is:
+    #   version (4) || depth (1) || parent fingerprint (4)) ||
+    #   child num (4) || chain code (32) || key data (33) || checksum (4)
+
+    # Split the payload and checksum up and ensure the checksum matches.
+    payload = decoded[: decoded_len - 4]
+    included_cksum = decoded[decoded_len - 4 :]
+    computed_cksum = crypto.checksum(payload.b)[:4]
+    if included_cksum != computed_cksum:
+        raise DecredError("wrong checksum")
+
+    # Ensure the version encoded in the payload matches the provided network.
+    privVersion = netParams.HDPrivateKeyID
+    pubVersion = netParams.HDPublicKeyID
+    version = payload[:4]
+    if version not in (privVersion, pubVersion):
+        raise DecredError(f"Unknown versions {privVersion} {pubVersion} {version}")
+
+    # Deserialize the remaining payload fields.
+    depth = payload[4:5].int()
+    parentFP = payload[5:9]
+    childNum = payload[9:13].int()
+    chainCode = payload[13:45]
+    keyData = payload[45:78]
+
+    # The key data is a private key if it starts with 0x00. Serialized
+    # compressed pubkeys either start with 0x02 or 0x03.
+    isPrivate = keyData[0] == 0x00
+    if isPrivate:
+        # Ensure the private key is valid.  It must be within the range
+        # of the order of the secp256k1 curve and not be 0.
+        keyData = keyData[1:]
+        # if keyNum.Cmp(secp256k1.S256().N) >= 0 || keyNum.Sign() == 0 {
+        if (keyData >= Curve.N) or keyData.iszero():
+            raise DecredError("unusable key")
+        # Ensure the public key parses correctly and is actually on the
+        # secp256k1 curve.
+        Curve.publicKey(keyData.int())
+
+    return crypto.ExtendedKey(
+        privVer=privVersion,
+        pubVer=pubVersion,
+        key=keyData,
+        pubKey="",
+        chainCode=chainCode,
+        parentFP=parentFP,
+        depth=depth,
+        childNum=childNum,
+        isPrivate=isPrivate,
+    )
+
+
+def getUTXOs(node, key, net):
+    """Get a list of all unspent utxo paying to the branch within the gap limit."""
+    idx, txGap = 0, 0
+    utxos = []
+    while txGap < GAP_LIMIT:
+        try:
+            addr = addrlib.deriveChildAddress(key, idx, net)
+        except Exception:
+            # Very small chance of a bad address.
+            idx += 1
+            continue
+        try:
+            res = node.searchRawTransactions(addr, verbose=True)
+            for rawTx in res:
+                for vout in rawTx.vout:
+                    try:
+                        if addr in vout.scriptPubKey.addresses:
+                            privKey = key.child(idx)
+                            # This should throw if the output is spent.
+                            out = node.getTxOut(rawTx.txHash, vout.n)
+                            utxo = {
+                                "privKey": crypto.privKeyFromBytes(privKey.key),
+                                "hash": rawTx.txHash,
+                                "n": vout.n,
+                                "value": out.value,
+                                "script": out.scriptPubKey.script,
+                            }
+                            utxos.append(utxo)
+                    except Exception:
+                        pass
+            # txs found, reset no txs gap
+            txGap = 0
+        except Exception:
+            # No txs found.
+            txGap += 1
+        idx += 1
+    return utxos
+
+
+def signUTXOs(node, utxos, sendToAddr, totalValue, net):
+    """
+    Create one trasaction spending all the outputs to the passed address and
+    sign the inputs.
+    """
+    payToScript = txscript.payToAddrScript(sendToAddr)
+    output = msgtx.TxOut(value=0, version=0, pkScript=payToScript)
+    inputs = []
+    for utxo in utxos:
+        opCodeClass = txscript.getP2PKHOpCode(utxo["script"])
+        tree = (
+            wire.TxTreeRegular
+            if opCodeClass == txscript.opNonstake
+            else wire.TxTreeStake
+        )
+        op = msgtx.OutPoint(txHash=utxo["hash"], idx=utxo["n"], tree=tree)
+        txIn = msgtx.TxIn(previousOutPoint=op, valueIn=int(utxo["value"] * 1e8))
+        inputs.append(txIn)
+
+    newTx = msgtx.MsgTx(
+        serType=wire.TxSerializeFull,
+        version=txscript.generatedTxVersion,
+        txIn=inputs,
+        txOut=[output],
+        lockTime=0,
+        expiry=0,
+        cachedHash=None,
+    )
+
+    size = txscript.estimateSerializeSize(
+        [txscript.RedeemP2PKHSigScriptSize for _ in inputs], [output], 0
+    )
+    fee = txscript.calcMinRequiredTxRelayFee(FEE_RATE, size)
+
+    if fee > totalValue:
+        raise DecredError("Not enough funds to cover the transaction fee.")
+
+    output.value = totalValue - int(fee)
+
+    if txscript.isDustOutput(output, FEE_RATE):
+        raise DecredError("Transaction is considered dust. Not sending.")
+
+    for idx, utxo in enumerate(utxos):
+        signatureScript, _, _, _ = txscript.sign(
+            net,
+            newTx,
+            idx,
+            utxo["script"],
+            txscript.SigHashAll,
+            account.KeySource(priv=lambda _: utxo["privKey"], internal=None),
+            crypto.STEcdsaSecp256k1,
+        )
+        newTx.txIn[idx].signatureScript = signatureScript
+
+    return newTx
+
+
+def main():
+    net = None
+    isTestnet = False
+    tString = ""
+    netStr = input("Is this mainnet or testnet? (m/t)\n")
+    if netStr in ("testnet", "test", "t"):
+        net = nets.testnet
+        isTestnet = True
+        tString = "t"
+    elif netStr in ("mainnet", "main", "m"):
+        net = nets.mainnet
+    else:
+        raise DecredError("Unknown network entered.")
+
+    xprivStr = input("Enter xpriv: ")
+    xpriv = decodeExtendedKey(net, xprivStr)
+    # Double check that we can reproduce the xpriv.
+    if xpriv.string() != xprivStr:
+        raise DecredError("unknown xpriv parsing error")
+
+    # Printing a newline.
+    print()
+    coinType = COIN_TYPE_OLD
+    if isTestnet:
+        coinType = COIN_TYPE_TESTNET
+    purpose = xpriv.child(crypto.HARDENED_KEY_START + PURPOSE)
+    cointype = purpose.child(crypto.HARDENED_KEY_START + coinType)
+    acct = cointype.child(crypto.HARDENED_KEY_START + ACCT_NUM)
+    internal = acct.child(INTERNAL)
+    external = acct.child(EXTERNAL)
+
+    dcrdConfig = cfg(isTestnet)
+    node = rpc.Client(
+        urlunsplit(("https", dcrdConfig["rpclisten"], "/", "", "")),
+        dcrdConfig["rpcuser"],
+        dcrdConfig["rpcpass"],
+        dcrdConfig["rpccert"],
+    )
+
+    utxos = getUTXOs(node, internal, net) + getUTXOs(node, external, net)
+    totalValue = sum((utxo["value"] for utxo in utxos))
+
+    if totalValue == 0:
+        print("No funds found to send.")
+        return
+
+    print(f"Found {len(utxos)} outputs totalling {totalValue} {tString}dcr.\n")
+
+    while True:
+        sendToAddrStr = input("Input address to send funds: ")
+        print()
+        try:
+            # Will throw if bad addr.
+            sendToAddr = addrlib.decodeAddress(sendToAddrStr, net)
+            break
+        except Exception as e:
+            print(e)
+            tryAgain = input("\nBad address. Try again? (y/n)\n")
+            if tryAgain not in ("y", "yes"):
+                print("Aborted")
+                return
+
+    signedTx = signUTXOs(node, utxos, sendToAddr, int(totalValue * 1e8), net)
+
+    # Double check output script address.
+    _, gotAddrs, _ = txscript.extractPkScriptAddrs(0, signedTx.txOut[0].pkScript, net)
+    if gotAddrs[0].address() != sendToAddrStr:
+        raise DecredError("unknown output address parsing error")
+
+    print(f"Got the raw hex: {signedTx.serialize().hex()}")
+    print(f"{repr(signedTx)}\n")
+    doIt = input(f"Really send funds to {sendToAddrStr}? (y/n)\n")
+    if doIt in ("yes", "y"):
+        txid = node.sendRawTransaction(signedTx)
+        print(f"\nSent transaction: {reversed(txid).hex()}")
+    else:
+        print("Aborted.")
+
+
+main()