CloudFront Functions

AWSTemplateFormatVersion: 2010-09-09
Description: Creates a Base CloudFront Function for Authentification
Metadata:
  Author:
    Description: David Krohn

Parameters:
  CloudFrountUsername:
    Description: Username CloudFront
    Type: String
  CloudFrountPassword:
    Description: Password CloudFront
    Type: String
    NoEcho: true
Ressources:
  CloudFrontFunctionBasicAuth:
    Type: AWS::CloudFront::Function
    Properties: 
      AutoPublish: true
      FunctionCode: !Sub |
        var USERS = {
            Website: [{
                username: '${CloudFrountUsername}',
                password: '${CloudFrountPassword}',
            }],
        };

        //Response when auth is not valid.
        var response401 = { 
            statusCode: 401,
            statusDescription: 'Unauthorized',
            headers: {
                'www-authenticate': {
                    value: 'Basic'
                },
            },
        };

        var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

        function btoa(input) {
            input = String(input);
            var bitmap, a, b, c,
                result = "",
                i = 0,
                rest = input.length % 3; // To determine the final padding

            for (; i < input.length;) {
                if ((a = input.charCodeAt(i++)) > 255 ||
                    (b = input.charCodeAt(i++)) > 255 ||
                    (c = input.charCodeAt(i++)) > 255)
                    throw new TypeError("Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range.");

                bitmap = (a << 16) | (b << 8) | c;
                result += b64.charAt(bitmap >> 18 & 63) + b64.charAt(bitmap >> 12 & 63) +
                    b64.charAt(bitmap >> 6 & 63) + b64.charAt(bitmap & 63);
            }

            // If there's need of padding, replace the last 'A's with equal signs
            return rest ? result.slice(0, rest - 3) + "===".substring(rest) : result;
        }

        function handler(event) {
            var request = event.request;
            var headers = request.headers;

            var auth = request.headers.authorization && request.headers.authorization.value;


            var users = USERS['Website'];

            if (users) {
                if (!auth || !auth.startsWith('Basic ')) {
                    return response401;
                }
                if(!users.find(function(user) {

                        // Construct the Basic Auth string
                        var authString = 'Basic ' + btoa(user.username + ':' + user.password);

                        return authString === auth;
                    })) {
                    return response401;
                }
            }
            return request;
        }

      FunctionConfig:
        Comment: !Sub 'Basic Auth for S3 Bucket ${MyWebsiteBucket}'
        Runtime: cloudfront-js-1.0