Coinbase Pro HMAC signature generation for Postman

coinbaseProSignature.js

// Computes the HMAC for requests sent to the Coinbase Pro API.
//
// - Add the following code as Postman pre-request script
// - Adapt the getPatch function an the variable names according to your needs

const timestamp = Date.now() / 1000;

function getPath(url) {
    // URL path regex works only if your URLs look like this: {{api_url}}/resource
    // If you use hardcoded URLs or any other scheme, adapt the regex pattern!
    const matches = url.match(/.+?(\/.+?)(?:#|\?|$)/);
    return (matches && matches.length > 1) ? matches[1] : ''; 
}
 
function computeSignature(request) {
    const data      = request.data;
    const method    = request.method;
    const path      = getPath(request.url);
    const body      = (method === 'GET' || !data) ? '' : JSON.stringify(data);
    const message   = timestamp + method + path + body;
    const key       = CryptoJS.enc.Base64.parse(pm.variables.get('CB-SECRET'));
    const hash      = CryptoJS.HmacSHA256(message, key).toString(CryptoJS.enc.Base64);

    return hash;
}
 
postman.setEnvironmentVariable('hmacSignature', computeSignature(request));
postman.setEnvironmentVariable('hmacTimestamp', timestamp)

Here's how I got it working for the non-pro API.

CB-SECRET is set as an environment variable, the rest I've just put directly in my request.

• Uses Math.floor instead of ceil simply because that's the example given by Coinbase
• Passes the HMAC the secret as a string rather than base64 parsing it
• Wants a hex digest rather than base64
• No need for regex for the path, postman provides an array: pm.request.url.path (needs joining with /)

const timestamp = Math.floor(Date.now() / 1000);
console.log(timestamp);
 
function computeSignature(request) {
    const data      = request.data;
    const method    = request.method;
    const path      = "/" + pm.request.url.path.join("/");
    const body      = (method === 'GET' || !data) ? '' : JSON.stringify(data);
    const message   = timestamp + method + path + body;
    const key       = pm.variables.get('CB-SECRET');
    const hash      = CryptoJS.HmacSHA256(message, key).toString(CryptoJS.enc.Hex);
    console.log("Message: " + message + " HMAC: " + hash);

    return hash;
}

pm.environment.set('CB-ACCESS-SIGN', computeSignature(request));
pm.environment.set('CB-ACCESS-TIMESTAMP', timestamp);

This works for me. I had to change this line:

const body      = (method === 'GET' || !data) ? '' : JSON.stringify(data);

to

const body      = (method === 'GET' || !data) ? '' : data;

Script:

const timestamp = Date.now() / 1000;

pm.environment.set("CB-SECRET", "your-secret");
 
function computeSignature(request) {
    const data      = request.data;
    const method    = request.method;
    const path      = "/" + pm.request.url.path.join("/");
    const body      = (method === 'GET' || !data) ? '' : data;
    const message   = timestamp + method + path + body;
    const key       = CryptoJS.enc.Base64.parse(pm.variables.get('CB-SECRET'));
    const hash      = CryptoJS.HmacSHA256(message, key).toString(CryptoJS.enc.Base64);

    return hash;
}

pm.environment.set('CB-ACCESS-SIGN', computeSignature(request));
pm.environment.set('CB-ACCESS-TIMESTAMP', timestamp);