paypal-ipn/README.md

Package for verifying Paypal IPN messages

# PayPal IPN Verification

A simple NodeJS package for verifying PayPal IPN messages.

## Installation
```sh
$ npm install paypal-ipn
```

## Usage
There is only one function, `verify`, which is used to verify any IPN messages you receive:

```javascript
ipn.verify(ipn_params, [settings], callback);
```

`ipn_params` is the dictionary of POST values sent to your IPN script by PayPal. Don't modify the dict in any way, just pass it directly to `ipn.verify` to check if the IPN message is valid.


Example code:

```javascript
// Must respond to PayPal IPN request with an empty 200 first
// If using Express, uncomment the following:
// res.send(200);

var ipn = require('paypal-ipn');

ipn.verify(params, function callback(err, msg) {
  if (err) {
    console.error(err);
  } else {
    // Do stuff with original params here

    if (params.payment_status == 'Completed') {
      // Payment has been confirmed as completed
    }
  }
});

//You can also pass a settings object to the verify function:
ipn.verify(params, {'allow_sandbox': true}, function callback(err, mes) {
  //The library will attempt to verify test payments instead of blocking them
});
```

Note that all the package does is confirm that the IPN message is valid. After this, you will still need to make some more checks:

* Confirm that the `payment_status` is `Completed`.

* Use the transaction ID to verify that the transaction has not already been processed, which prevents duplicate transactions from being processed.

* Validate that the receiver's email address is registered to you.

* Verify that the price, item description, and so on, match the transaction on your website.

You can find more information on the [PayPal documentation for IPN](https://cms.paypal.com/cgi-bin/marketingweb?cmd=_render-content&content_ID=developer/e_howto_admin_IPNIntro).

### Settings

Optional settings:

```
{
  'allow_sandbox': false
}
```

#### allow_sandbox

If this is true, the library will attempt to verify sandbox requests at PayPal's sandbox URL.

If this is false, the library will callback with an error without checking PayPal. (This is the default value.)

**You should set this to false on production servers.**

### The callback
The callback has two parameters, `err` and `msg`.

If `err` is null then the IPN is valid and you can continue processing the payment. `msg` is always `VERIFIED` then.

In case IPN was invalid or the http request failed `err` holds the Error object.

### Express
`paypal-ipn` works fine with [Express](http://expressjs.com/) or any other web framework.

All you need to do is pass in the request parameters to `ipn.verify`.

In Express, the request parameters are in `req.body`:

```javascript
ipn.verify(req.body, callback_function);
```