How to create SAS url for azure blob storage using java How to generate azure blob storage SAS url using java?
do we have any api where i can expire any existing sas url?
Requirement: Generate any sas url with expiry time as 7 days and i want some api where i can reset this sas url at any point of time within expiry time limit.
but looks like we don't have this i guess and every time it will create new sas url but we can expire any existing sas url at any point of time.
You can create an access policy on the container with set start and end date. Then create a SAS token on the container or an individual blob using that policy. Once the policy is deleted it will also invalidate all SAS tokens that were generated with it.
public BlobServiceSasSignatureValues(String identifier)
//Where identifier is the name of the access policy
It's limited to 5 access policies on a table, but if you are a bit flexible on the expiration date you could make one each week, so every blob would be available for at least a week and up to two at most. It also implies that once you remove the policy all url's for that week no longer work.
I don't think there's any other way you are able to invalidate the generated url's apart from generating new accesss keys.
Related
We are using Azure blob storage for storing unstructured content.
Our setup is as follows
Our Browser client(accessing files) -> Our Backend (our cloud platform) -> Proxy managing Azure account (our cloud platform)-> Azure blob storage.
The proxy managing the Azure account has the account credentials. It generates a SAS token and gives to the consumers like our backend. This SAS token has infinite expiry time.
Now we from our backend want to generate a pre-signed url (similar concept of S3) with an expiration time and give to the browser client. This is required since we want to download the content directly from the browser bypassing our backend for large files.
It seems the generated signed url will always have unlimited expiry time as our SAS token.
Please note we (our backend ) does not have access to the Azure storage so we cannot generate an access token.
Is there any way our problem could be solved ?
Best Regards,
Saurav
If I understand correctly, you get a SAS Token that never expires. However you would want to specify an expiry date when you use this token in your SAS URL. This is not possible.
Essentially a SAS URL for a blob is base blob URL (https://account.blob.core.windows.net/container/blob) + SAS Token.
You cannot change any of the parameters of the SAS Token when using it in SAS URL because the sig portion of SAS URL is computed based on the other parameters in your SAS Token like se, st etc. Doing so will invalidate the SAS Token.
Furthermore, you can't create a new SAS Token using another SAS Token.
Only solution to your problem is to have your proxy service create a SAS Token with predefined expiry time.
I am generating a shared access signature(SAS) for one of the blob containers which is v 2 using the Azure portal. I am trying to upload a file from frontend for which SAS is required. The problem is SAS is expiring every day. Is there a way to update the SAS automatically using the code or is there a way to do the authentication using Azure AD.
So Basically I have a front end where user logs in using Azure AD, now i want to utilize his session to allow him to upload to Azure storage. As he is already authorized, i feel there should be a way to generate SAS on the fly for his session.
Shared access signatures are useful for providing limited permissions to your storage account to clients that should not have the account key.
If you are the one writing data to the storage account, do so server side. If you do that, you can validate the user is logged in. If that's the case, allow your backend to write in the storage account using one of the access keys (or better yet, a managed identity.
Of course, you could have your front-end request a SAS token from the back-end, for instance from an API. This could simply be implemented, for instance using an Azure Function. And the SAS token could use near-term expiration times. In the end, you're still opening up parts of the storage account to anyone who can access the frontend.
With near-term expiration, even if a SAS is compromised, it's valid only for a short time. This practice is especially important if you cannot reference a stored access policy. Near-term expiration times also limit the amount of data that can be written to a blob by limiting the time available to upload to it
Source: Using shared access signatures (SAS)
Taken from that same article:
The following code example creates an account SAS that is valid for the Blob and File services, and gives the client permissions read, write, and list permissions to access service-level APIs. The account SAS restricts the protocol to HTTPS, so the request must be made with HTTPS.
static string GetAccountSASToken()
{
// To create the account SAS, you need to use your shared key credentials. Modify for your account.
const string ConnectionString = "DefaultEndpointsProtocol=https;AccountName=account-name;AccountKey=account-key";
CloudStorageAccount storageAccount = CloudStorageAccount.Parse(ConnectionString);
// Create a new access policy for the account.
SharedAccessAccountPolicy policy = new SharedAccessAccountPolicy()
{
Permissions = SharedAccessAccountPermissions.Read | SharedAccessAccountPermissions.Write | SharedAccessAccountPermissions.List,
Services = SharedAccessAccountServices.Blob | SharedAccessAccountServices.File,
ResourceTypes = SharedAccessAccountResourceTypes.Service,
SharedAccessExpiryTime = DateTime.UtcNow.AddHours(24),
Protocols = SharedAccessProtocol.HttpsOnly
};
// Return the SAS token.
return storageAccount.GetSharedAccessSignature(policy);
}
I am trying to use Azure Managed storage account keys. I succeeded in setting up a managed storage account with 1 day regeneration period for testing purposes. My questions are
Is it possible for me to access this storage account from any other application e.g Storage Explorer, Cloud Explorer, Power BI Desktop etc. If yes, how to get the key?
I still see keys for this storage account in azure portal. Are they invalid ? or will they change every time keyvault regenerates keys for this storage account?
I had set -ActiveKeyName Key2. Each time i regenerate the key Key1 is being regenerated. If Key1 is regenerated then is Key2 still valid even after 1 day? This active key concept is not so clear in the documentation. Can someone explain it.
Is Sas token the only way to get access to storage account resources. I just want to have full access to storage account for the regeneration period. is it possible without using Sas token?
I created SAS Definition from powershell and create SAS token out of it whenever i want to access Storage account. I think SAS Token would be invalidated but not SAS Definion. I am assuming i don't have to handle expiry in the code because i always get new SAS Token. Am i doing it correctly?
I know it's been 11 months, and you either abandoned this or figured it out for yourself. I will answer your question in case anyone finds this question.
Yes! Any application that you use should talk to the KeyVault to get a SAS token. Avoid using the storage account keys, they are still valid, but may change at any time. If you just need one time access you can use powershell to get a sas token that you can use.
They are valid, but will change whenever KeyVault rotates them, so don't use them, and don't change them yourself.
There are two valid keys at any one time. Only one of the keys are used to issue SAS tokens at any one time. This is the active key. When it is time to rotate, KeyVault regenerates the key that is not active, and then sets the newly created key as active.
Lets do an example. Lets say the keys are called key1 and key2. key1 is equal to 'A' and key2 is equal to 'b'. Let key1 be the active key.
Regenerate key2. key2 is now equal to 'c'
Set key2 as active. New sas tokens are now generated with key2.
Now the keys have been rotated, but key1 is still valid. It will be changed next time the keys are rotated. This way, as long as the rotation period is longer than the lifetime of the tokens, no token will become invalid before it expires.
No the keys are still valid so they can also be used, but you don't know when they will change.
The SAS definition is where the lifetime of a token is declared. When you created it, a secret was created in KeyVault. Every time you get that secret, you get a new token. If you do not store the token, but ask for a new every time you will always get a valid one. But you might want to cache the token, as going to KeyVault every time is slow.
How to create the managed storage account
How create the SAS definition
I am planning to use keyVault to manage Storage Account Keys.
My question is, when the keys get rotated, would the SAS token previously served by the keyVault get invalidated ?
For example, if I request a SAS for a blob with 30days validity but the key rotation period I set is 3 days, then effectively the validity of the SAS would be 3 days or 30 days ?
PS: I asked this query in the MS doc but did not get a reply for this. That is why I am asking you good people of SO.
My question is, when the keys get rotated, would the SAS token
previously served by the keyVault get invalidated ?
By default, the answer is yes, the keyvault will get invalidated.
If the SAS token is about to expire, we should get sasToken again from keyvault and update it.
More information about keyvault and storage account, please refer to this link.
For example, if I request a SAS for a blob with 30days validity but
the key rotation period I set is 3 days, then effectively the validity
of the SAS would be 3 days or 30 days ?
As far as I know, if we follow official article, the answer is 3 days.
We can use keyvault to manage Azure storage account, update storage account key or get storage account key.
For example, we can use this command Update-AzureKeyVaultManagedStorageAccountKey to update storage account key.
That's actually a bit more complicated than another answer presents.
For starters, storage accounts have two storage account keys, both of which would give access to that account.
SAS tokens are derived from either of those keys. They will keep working until they expire on their own OR until they key they derived from is rotated (whichever is sooner).
Key vault managed storage accounts have a notion of "active key". Whenever you request a SAS token from KV, it will use currently active key to generate the SAS token it returns.
Whenever auto-rotation happens, KV will rotate the key that is NOT currently active and make it active key. The previously active key will become "inactive" but it will stay until next auto-rotation, which means that any SAS tokens generated before rotation will continue working until they expire or another rotation happens.
All that does not matter of course if you use Update-AzureKeyVaultManagedStorageAccountKey and rotate currently active key. In that case all previously produced SAS tokens will immediately become invalid.
So, as long as you stick to auto-rotation only AND the duration on your SAS tokens is less that auto-rotation period, SAS tokens should not get invalid because of storage key change.
Earlier i was getting a blob without using a sas authorization.
But now I want only those users to be able to access a blob who has the sas token.
Lets say i want to access a file at
https://storageaccount.blob.core.windows.net/sascontainer/sasblob.txt
Now i have the SAS token too. So the new url would be
https://storageaccount.blob.core.windows.net/sascontainer/sasblob.txt?sv=2012-02-12&st=2013-04-12T23%3A37%3A08Z&se=2013-04-13T00%3A12%3A08Z&sr=b&sp=rw&sig=dF2064yHtc8RusQLvkQFPItYdeOz3zR8zHsDMBi4S30%3D
What do I do next so that only those with the second link can go and get the "sasblob.txt" file?
What changes do i have to make in the azure portal?
I guess the only change i have to make in the client side is the URL. I need to replace the URl without the sas token with the URl containing the sas token.
As long as the blob is private (which can be set at the container level), nobody will have access without the SAS-augmented URI. Even if you kept giving out the public URI, it wouldn't work if the container was marked as private.
Also, in your example, you've created a fictitious sascontainer. Note that shared access signatures work on any blob in any container. You don't need a special designated container.
With a SAS-based URI, it will be a valid URI until such time as the time expires (or you delete the blob). If you wanted more control, such as disabling a URI, you'd need to use a Shared Access Policy. Just something for you to consider looking into. And plenty of documentation on that, should you go that route.