Azure Blob Storage SAS Token dose not expire as expected - azure

Question

My application generates SAS tokens to access existing blobs within my container. However, my SAS token dose not look like it is expiring. I am able to view and get blob from container way past expiration time I am claiming.
Here is the code :
public string GenerateSasToken([NotNull] string containerName, [NotNull] string blobName)
{
var startTime = DateTimeOffset.UtcNow
var expiredTime = startTime.AddSeconds(20);
var blobClient = new BlobClient(_options.Value.ConnectionString, containerName, blobName);
var sasBuilder = new BlobSasBuilder(BlobContainerSasPermissions.Read, expiredTime)
{
BlobName = blobName,
BlobContainerName = containerName,
StartsOn = startTime,
ExpiresOn = expiredTime
};
var uri = blobClient.GenerateSasUri(sasBuilder);
return uri.ToString();
}
Token been generated is valid and I am able to use it, but it dose not expire after 20 seconds in fact it dose not expire even after 15 minutes.
Am I missing something within this API?
Thank you!
Edit:
I am attaching SAS token that was generated.
?sv=2020-08-04&st=2022-01-24T21%3A20%3A41Z&se=2022-01-24T21%3A21%3A01Z&sr=b&sp=r&sig=signature-here

Answer 1

Even though the SAS token is expired, because of the browser caching, you would still be able to access the blob storage using the same SAS token
In order to avoid this, you can override the cache-control header in the SAS token as suggested by #Gaurav Mantri
You need to set CacheControl value in your BlobSasBuilder function to override the cache-control header
Your BlobSasBuilder function can be as below:
var sasBuilder = new BlobSasBuilder(BlobContainerSasPermissions.Read, expiredTime)
{
BlobName = blobName,
BlobContainerName = containerName,
StartsOn = startTime,
ExpiresOn = expiredTime,
CacheControl = "max-age=" + expiredTime
};