Eu sou:
- Criando um aplicativo Web
- Front-end do AngularJS com upload de arquivo ng (https://github.com/danialfarid/ng-file-upload)
- Back-end do Node.js.
- Deseja fazer upload de imagens no meu bucket do Amazon S3

Estou tentando seguir este tutorial:https://github.com/danialfarid/ng-file-upload/wiki/Direct-S3-upload-and-Node-signing-example

Essencialmente, o fluxo do programa é selecionar o arquivo, clicar em um botão, solicitar assinatura do back-end e fazer o upload para o S3.

Recebo a assinatura do back-end com o código 200, mas quando o front-end tenta carregar a imagem, vejo isso no menu do desenvolvedor:
OPTIONS https://mybucket.name.s3-us-east-1.amazonaws.com/ net::ERR_NAME_NOT_RESOLVED

É o meu código que é o problema ou a maneira como configuro meu bucket?

Código adicionado, se necessário:

CORS no meu balde S3

<?xml version="1.0" encoding="UTF-8"?>
<CORSConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
    <CORSRule>
        <AllowedOrigin>*</AllowedOrigin>
        <AllowedMethod>GET</AllowedMethod>
        <MaxAgeSeconds>3000</MaxAgeSeconds>
        <AllowedHeader>Authorization</AllowedHeader>
    </CORSRule>
    <CORSRule>
        <AllowedOrigin>my.computers.IP.Address</AllowedOrigin>
        <AllowedMethod>PUT</AllowedMethod>
        <AllowedMethod>POST</AllowedMethod>
        <AllowedMethod>DELETE</AllowedMethod>
        <AllowedHeader>*</AllowedHeader>
    </CORSRule>
</CORSConfiguration>

Código de back-end do Node.js.

app.post('/signing', function(req, res) {
    var request = req.body;
    var fileName = request.filename

    var extension = fileName.substring(fileName.lastIndexOf('.'));
    var today = new Date();
    var path = '/' + today.getFullYear() + '/' + today.getMonth() + '/' + today.getDate() + '/' + uuid.v4() + extension;

    var readType = 'private';

    var expiration = moment().add(5, 'm').toDate(); //15 minutes

    var s3Policy = {
        'expiration': expiration,
        'conditions': [{
                'bucket': aws.bucket
            },
            ['starts-with', '$key', path], 
            {
                'acl': readType
            },
            {
              'success_action_status': '201'
            },
            ['starts-with', '$Content-Type', request.type],
            ['content-length-range', 2048, 10485760], //min and max
        ]
    };

    var stringPolicy = JSON.stringify(s3Policy);
    var base64Policy = new Buffer(stringPolicy, 'utf-8').toString('base64');

    // sign policy
    var signature = crypto.createHmac('sha1', aws.secret)
        .update(new Buffer(base64Policy, 'utf-8')).digest('base64');

    var credentials = {
        url: s3Url,
        fields: {
            key: path,
 ,           AWSAccessKeyId: aws.key,
            acl: readType,
            policy: base64Policy,
            signature: signature,
            'Content-Type': request.type,
            success_action_status: 201
        }
    };
    res.jsonp(credentials);
});

Código de front-end do AngularJS

App.controller('MyCtrl2', ['$scope', '$http', 'Upload', '$timeout', function ($scope, $http, Upload, $timeout) {
    $scope.uploadPic = function(file) {
        var filename = file.name;
        var type = file.type;
        var query = {
            filename: filename,
            type: type
        };
        $http.post('/signing', query)
            .success(function(result) {
                Upload.upload({
                    url: result.url, //s3Url
                    transformRequest: function(data, headersGetter) {
                        var headers = headersGetter();
                        delete headers.Authorization;
                        return data;
                    },
                    fields: result.fields, //credentials
                    method: 'POST',
                    file: file
                }).progress(function(evt) {
                    console.log('progress: ' + parseInt(100.0 * evt.loaded / evt.total));
                }).success(function(data, status, headers, config) {
                    // file is uploaded successfully
                    console.log('file ' + config.file.name + 'is uploaded successfully. Response: ' + data);
                }).error(function() {

                });
            })
            .error(function(data, status, headers, config) {
                // called asynchronously if an error occurs
                // or server returns response with an error status.
        });
    };
}]);