Basic Callback Handler Code Example

Request payload example

This example demonstrates the raw and decoded JWT payload sent by the Co-Signer to the Callback Handler.

Additionally, it includes a test private key that signed the payload and the corresponding public key that should be used for signature validation:

🚧
The provided Private Key is for example purposes only and should not be used in your production system.

📘
The provided example may contain properties that are not sent by default. Customers should ensure they DO NOT expect to receive values that are not documented in the Approve Transactions and Approve Configuration Changes sections.

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{
  "txId": "9c794cee-7e27-46c9-9e9a-ed68295ff06b",
  "operation": "TRANSFER",
  "sourceType": "VAULT",
  "sourceId": "0",
  "destType": "VAULT",
  "destId": "1",
  "asset": "ETH",
  "amount": 0.01,
  "amountStr": "0.010000000000000000",
  "requestedAmount": 0.01,
  "requestedAmountStr": "0.01",
  "fee": "0.000597803762241000",
  "destAddressType": "WHITELISTED",
  "destAddress": "0x5dC69B1Fbb13Bafd09af88a782F0F285772Ad5f8",
  "destinations": [
    {
      "amountNative": 0.01,
      "amountNativeStr": "0.01",
      "amountUSD": 18.74292937,
      "dstAddressType": "WHITELISTED",
      "dstId": "1",
      "dstWalletId": "",
      "dstName": "Network Deposits",
      "dstSubType": "",
      "dstType": "VAULT",
      "displayDstAddress": "0x5dC69B1Fbb13Bafd09af88a782F0F285772Ad5f8",
      "action": "ALLOW",
      "actionInfo": {
        "capturedRuleNum": 5,
        "rulesSnapshotId": 8164,
        "byGlobalPolicy": false,
        "byRule": true,
        "capturedRule": "{\"type\":\"TRANSFER\",\"transactionType\":\"TRANSFER\",\"asset\":\"*\",\"amount\":0,\"operators\":{\"wildcard\":\"*\"},\"applyForApprove\":true,\"action\":\"ALLOW\",\"src\":{\"ids\":[[\"*\"]]},\"dst\":{\"ids\":[[\"*\"]]},\"dstAddressType\":\"*\",\"amountCurrency\":\"USD\",\"amountScope\":\"SINGLE_TX\",\"periodSec\":0}"
      }
    }
  ],
  "rawTx": [
    {
      "keyDerivationPath": "[ 44, 60, 0, 0, 0 ]",
      "rawTx": "02ef0104843b9aca008506a0c1987d825208945dc69b1fbb13bafd09af88a782f0f285772ad5f8872386f26fc1000080c0",
      "payload": "77b4e74099ce90c08503c0e0bb6e672dbe1c5e3e127ce333bf22eb581cd3f6ce"
    }
  ],
  "players": [
    "21926ecc-4a8a-4614-bbac-7c591aa7efdd",
    "27900737-46f6-4097-a169-d0ff45649ed5",
    "f89cac50-c656-4e74-879f-041aff8d01b5"
  ],
  "requestId": "9c794cee-7e27-46c9-9e9a-ed68295ff06b"
}

Response payload example

This example demonstrates the raw and decoded JWT response returned from the Callback Handler to the Co-signer. The response is signed using the Callback Handler's private key. The Co-signer then verifies the signature using the predefined public key configured during the Co-signer installation phase.

For simplicity, the examples use the same private/public key pair as in the Request Example section:

📘
Please note that the iat value is not required in the actual response and will be ignored by the Co-Signer. It is included here because the JWT signature library automatically adds this field.

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{
  "action": "REJECT",
  "requestId": "9c794cee-7e27-46c9-9e9a-ed68295ff06b",
  "rejectionReason": "Logic returned false",
  "iat": 1720472594
}

API Co-Signer basic Callback Handler server example

Here is a code example for a basic Callback Handler application. The application is designed to handle POST requests from the Co-signer at the endpoint /v2/tx_sign_request.

It validates that the received payload is signed with the correct private key.
If the verification is successful, it responds with a 200 status code, the REJECT action, and the rejectionReason in the response body.
If the verification fails, it responds with a 401 status code.

const express = require("express");
const bodyParser = require("body-parser");
const fs = require("fs");
const jwt = require("jsonwebtoken");
const privateKey = fs.readFileSync("callback_private.pem");
const cosignerPubKey = fs.readFileSync("cosigner_public.pem");
const app = express();

app.use(
  express.urlencoded({
    extended: true
  })
);
app.use(express.json());

app.use(function (req) {
  req.rawBody = "";
  req.setEncoding("utf8");
  req.on("data", function(chunk) {
    req.rawBody += chunk;
  });
  req.on("end", function () {
   req.next();
  });
});

app.post("/v2/tx_sign_request", async (req, res) => {
  let verified;
  try {
  const tx = jwt.decode(req.rawBody);
  const { requestId } = tx;
  verified = jwt.verify(req.rawBody, cosignerPubKey);
  if (verified) {
    let action = "REJECT";
    let rejectionReason = "Logic returned false";
    const signedRes = jwt.sign(
      {
        action,
        requestId,
        rejectionReason
      },
      privateKey,
      { algorithm: "RS256" }
    );
    res.send(signedRes);
  }
  } catch (e) {
    res.sendStatus(401);
  }
});
app.listen(3000);

from pathlib import Path
from wsgiref.simple_server import make_server
import falcon
import jwt
callback_handler_prikey = None
cosigner_pubkey = None

# Load keys.
f1 = Path("callback_private.pem")
if f1.is_file(): callback_handler_prikey = f1.read_bytes()
f2 = Path("cosigner_public.pem")
if f2.is_file(): cosigner_pubkey = f2.read_bytes()

class JWTTransferRequest(object):
    def on_post(self, req, resp):
        raw_req = req.bounded_stream.read()
        req = jwt.decode(raw_req, cosigner_pubkey, algorithms=["RS256"])
        resp.body = jwt.encode({'action': 'APPROVE', 'requestId': req['requestId']}, callback_handler_prikey, algorithm="RS256")
        resp.status = falcon.HTTP_200

# Create falcon app
app = falcon.App()
app.add_route('/v2/tx_sign_request', JWTTransferRequest())
app.add_route('/v2/config_change_sign_request', JWTTransferRequest())
if __name__ == '__main__':
    with make_server('', 80, app) as httpd:
        print('Serving on port 80...')
        # Serve until process is killed
        httpd.serve_forever()
JWTTransferRequest()

Basic Callback Handler Code Example

Request payload example

🚧
The provided Private Key is for example purposes only and should not be used in your production system.

📘
The provided example may contain properties that are not sent by default. Customers should ensure they DO NOT expect to receive values that are not documented in the Approve Transactions and Approve Configuration Changes sections.

Response payload example

📘
Please note that the `iat` value is not required in the actual response and will be ignored by the Co-Signer. It is included here because the JWT signature library automatically adds this field.

API Co-Signer basic Callback Handler server example

Request payload example

🚧The provided Private Key is for example purposes only and should not be used in your production system.

📘The provided example may contain properties that are not sent by default. Customers should ensure they DO NOT expect to receive values that are not documented in the Approve Transactions and Approve Configuration Changes sections.

Response payload example

📘Please note that the iat value is not required in the actual response and will be ignored by the Co-Signer. It is included here because the JWT signature library automatically adds this field.

API Co-Signer basic Callback Handler server example

🚧
The provided Private Key is for example purposes only and should not be used in your production system.

📘
The provided example may contain properties that are not sent by default. Customers should ensure they DO NOT expect to receive values that are not documented in the Approve Transactions and Approve Configuration Changes sections.

📘
Please note that the `iat` value is not required in the actual response and will be ignored by the Co-Signer. It is included here because the JWT signature library automatically adds this field.