Media.PublicUrl is wrong when using BlobStorage

[dozer75]

When using BlobStorage for media the URL that is generated in the PublicUrl is wrong. This worked in 9.1.0 (at least).

It uses a sas url and appends the filename like this:

https://<mystorage>.blob.core.windows.net/piranha-media?sv=2020-08-04&ss=b&srt=co&spr=https&st=2021-08-10T14%3A26%3A50Z&se=2025-12-30T23%3A26%3A50Z&sp=<sp>&sig=<sig>/c76c08bc-f5ba-43a4-af08-4c5bfdddc9e6/_MG_2955_210x160.jpg

The blob storage configuration is configured like this:

services.AddPiranhaBlobStorage(configuration.GetConnectionString("PiranhaBlobStorage"), "piranha-media", Piranha.Azure.BlobStorageNaming.UniqueFolderNames);

I can see in the code that in BlobStorage.GetPublicUrl that this has been changed between the versions and that the problem came with this change.

This is a bit critical error, since we're up on .NET 6.0 and thereby forced to use 10.0.x of Piranha and we cannot downgrade from .NET 6.

EDIT:

It seems that this PR broke the SAS possibility. I cannot use managed identity here, we need to have SAS possibility...

[tidyui]

Hi! Could you please provide an example of how the correct URL you are expecting should be formatted.

Regards

[dozer75]

Well, as you can see, the URL is in basically wrong, it uses the absolute URI which contains the query string of the container piranha-media with the SAS key and the folder/image appended...

The (at least) 9.1.0 version of this library did it correct, it creates a URL that is https://<mystorage>.blob.core.windows.net/piranha-media/c76c08bc-f5ba-43a4-af08-4c5bfdddc9e6/_MG_2955_210x160.jpg<querystring here>, which is correct.

[dozer75]

I checked the code now; the problem is in the GetPublicUrl method of BlobStorage.

It uses the _blobContainerClient.Uri.AbsoluteUri and just prepends the media.Id and id to it.

This is wrong in many ways (e.g. manipulating URLs should be done with UriBuilder), but a more correct way to retrieve the correct URL is to get the BlobClient from the _blobContainerClient and just return it's Uri like this:

var bc = _blobContainerClient.GetBlobClient(GetResourceName(media, id, false));

return bc.Uri.ToString();

This ensures that the correct blob URI is returned. However, the URI contains an SAS key which isn't good.

To avoid this, a shadow container that uses the _blobContainerClient.Uri (without the query string) should be created to retrieve a real public URL. Something like this:

var pubUri = new UriBuilder(_blobContainerClient.Uri) { Query = "" }.Uri;

var pubBcc = new BlobContainerClient(pubUri);

var bc = pubBcc.GetBlobClient(GetResourceName(media, id, false));

It seems that the issue only occurs if you're using a SAS key to connect, if you use managed identity or the Shared Access Key for the storage it works.

Steps to reproduce:

1. Create an azure storage
2. Create a Shared Access Signature key that gives default rights to blob container and object
3. Copy the generated connection string and use this when setting up the azure storage in Piranha in one of the example projects
4. Start the project and see that no images are shown.

EDIT: I modified this post a bit, since I found this article at Microsoft that used the URL without the SAS key to retrieve the anonymous URL (The Microsoft example itself contains an error, but that's out of scope here, my example above works but is a bit ineffective).

[martijntakken]

Hi, is the any update on this bug or a workaround?

[tidyui]

This will be released in the next minor version but we haven't started it yet. If you have the same issues as @dozer75 you can take his solution from previous comment and temporarily create your own BlobStorage implementation which you use instead of our package.

Regards