Get signed_request in Node.js (Express) Facebook Canvas App

Question

is there any way to get and parse signed_request in the Node.js Facebook page tab app? I need to know the page id, and if the user liked the page ...

Answer 1

I did this a bit back, and ended up writing a small library to do this. The original CoffeeScript can be found at https://gist.github.com/fbef51815ab6f062b51a#file_signed_request.coffee , there is a translation in JavaScript:

var crypto = require('crypto'); SignedRequest = (function() { function SignedRequest(secret, request) { this.secret = secret; this.request = request; this.verify = this.verify.bind(this); var parts = this.request.split('.'); this.encodedSignature = parts[0]; this.encoded = parts[1]; this.signature = this.base64decode(this.encodedSignature); this.decoded = this.base64decode(this.encoded); this.data = JSON.parse(this.decoded); } SignedRequest.prototype.verify = function() { if (this.data.algorithm !== 'HMAC-SHA256') { return false; } var hmac = crypto.createHmac('SHA256', this.secret); hmac.update(this.encoded); var result = hmac.digest('base64').replace(/\//g, '_').replace(/\+/g, '-').replace(/\=/g, ''); return result === this.encodedSignature; }; SignedRequest.prototype.base64encode = function(data) { return new Buffer(data, 'utf8').toString('base64').replace(/\//g, '_').replace(/\+/g, '-').replace(/\=/g, ''); }; SignedRequest.prototype.base64decode = function(data) { while (data.length % 4 !== 0) { data += '='; } data = data.replace(/-/g, '+').replace(/_/g, '/'); return new Buffer(data, 'base64').toString('utf-8'); }; return SignedRequest; })(); module.exports = SignedRequest; 

What you can use as follows:

 var verifier = new SignedRequest(clientSecret, signedRequest); verifier.verify() // whether or not the signed request verifies verifier.data // the data from the signed request