Skip to main content

Cross domain handling on Azure blob storage

This week a customer wanted to access the Azure blob storage from their Silverlight and Flash client applications. However due to the cross-domain restrictions of both technologies, we couldn’t access the blob storage out-of-the-box.

Let’s see how we can solve this and enable full access to blob storage through Silverlight and Flash.

ClientAccessPolicy.xml

When a Silverlight application makes a cross-domain call (other than those that are allowed by default), it first fetches a file called ClientAccessPolicy.xml from the root of the target server. For the blob storage this will be something like http://{namespace}.blob.core.windows.net/ .

Every blob in Windows Azure storage lives within a container, but there’s a special root container which lets us store blobs directly off the root of the domain. This is where we’ll put our ClientAccessPolicy.xml file. The following code creates a publicly readable root container and creates a blob named ClientAccessPolicy.xml within it:

private void CreateSilverlightPolicy()
{
var account= new CloudStorageAccount
(
new StorageCredentialsAccountAndKey("account", "key"), 
new Uri("http://sample.blob.core.windows.net"),
new Uri("http://sample.queue.core.windows.net"),
new Uri("http://sample.table.core.windows.net")
);
var client = account.CreateCloudBlobClient();
blobs.GetContainerReference("$root").CreateIfNotExist();
blobs.GetContainerReference("$root").SetPermissions(
new BlobContainerPermissions() {
PublicAccess = BlobContainerPublicAccessType.Blob
});
var blob = blobs.GetBlobReference("clientaccesspolicy.xml");
blob.Properties.ContentType = "text/xml";
blob.UploadText(@"<?xml version=""1.0"" encoding=""utf-8""?>
<access-policy>
<cross-domain-access>
<policy>
<allow-from http-methods=""*"" http-request-headers=""*"">
<domain uri=""*"" />
<domain uri=""http://*"" />
</allow-from>
<grant-to>
<resource path=""/"" include-subpaths=""true"" />
</grant-to>
</policy>
</cross-domain-access>
</access-policy>");
}
CrossDomain.xml

For the Flash the story is almost the same but instead of adding a clientpolicy file, we need to add a crossdomain.xml file.

private void CreateFlashPolicy()
{
var account= new CloudStorageAccount
(
new StorageCredentialsAccountAndKey("account", "key"), 
new Uri("http://sample.blob.core.windows.net"),
new Uri("http://sample.queue.core.windows.net"),
new Uri("http://sample.table.core.windows.net")
);

var client = account.CreateCloudBlobClient();
blobs.GetContainerReference("$root").CreateIfNotExist();
blobs.GetContainerReference("$root").SetPermissions(
new BlobContainerPermissions()
{
PublicAccess = BlobContainerPublicAccessType.Blob
});
var blob = blobs.GetBlobReference("crossdomain.xml");
blob.Properties.ContentType = "text/xml";
blob.UploadText(@"<?xml version=""1.0"" encoding=""utf-8""?>
<cross-domain-policy>
<allow-access-from domain=""*"" />
</cross-domain-policy>");
}

Popular posts from this blog

DevToys–A swiss army knife for developers

As a developer there are a lot of small tasks you need to do as part of your coding, debugging and testing activities.  DevToys is an offline windows app that tries to help you with these tasks. Instead of using different websites you get a fully offline experience offering help for a large list of tasks. Many tools are available. Here is the current list: Converters JSON <> YAML Timestamp Number Base Cron Parser Encoders / Decoders HTML URL Base64 Text & Image GZip JWT Decoder Formatters JSON SQL XML Generators Hash (MD5, SHA1, SHA256, SHA512) UUID 1 and 4 Lorem Ipsum Checksum Text Escape / Unescape Inspector & Case Converter Regex Tester Text Comparer XML Validator Markdown Preview Graphic Color B

Help! I accidently enabled HSTS–on localhost

I ran into an issue after accidently enabling HSTS for a website on localhost. This was not an issue for the original website that was running in IIS and had a certificate configured. But when I tried to run an Angular app a little bit later on http://localhost:4200 the browser redirected me immediately to https://localhost . Whoops! That was not what I wanted in this case. To fix it, you need to go the network settings of your browser, there are available at: chrome://net-internals/#hsts edge://net-internals/#hsts brave://net-internals/#hsts Enter ‘localhost’ in the domain textbox under the Delete domain security policies section and hit Delete . That should do the trick…

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.