Signature did not match error only occurs when SAS token is generated by deployed code

Question

I have the code below to generate a URL that can be used to download a blob. When I run the code locally and trigger it with an HTTP request, it returns a URL that works. I can use it to download the blob.

However, when I deploy the code to Azure, it returns a URL that looks similar to the one generated locally, but when I try to use that URL, I get the error mentioned in the title.

Here's the code:

def main(req: func.HttpRequest) -> func.HttpResponse:  
    region = req.params.get('region')  
    category = req.params.get('category')  
  
    if region and category:  
        blob_name = f'{category}_{region}.csv'  
        sas_token = generate_account_sas(  
            account_name = os.environ['STORAGE_ACCOUNT'],  
            account_key = os.environ['STORAGE_ACCOUNT_KEY'],  
            resource_types = ResourceTypes(object = True),   
            permission = AccountSasPermissions(read = True),  
            expiry = datetime.now() + timedelta(hours = int(os.environ['DOWNLOAD_TIME_LIMIT']))   
        )  
        return func.HttpResponse(f'{os.environ["STORAGE_CONTAINER_URI"]}/{blob_name}?{sas_token}')  
    else:  
        logging.warning('GenerateSignedUrl received a bad request')  
        return func.HttpResponse(  
             "Required parameters not found in the request.",  
             status_code=400  
        )  

When I deploy the code to Azure and trigger it with an HTTP request, it works and returns a URL. However, when I try to use that URL to download the blob, I get the error below:

<Error>
<Code>AuthenticationFailed</Code>
<Message>Server failed to authenticate the request. Make sure the value of Authorization header is formed correctly including the signature.
RequestId:c35ecfe2-801e-0015-38da-a8cc16000000
Time:2022-08-05T14:48:42.3053987Z</Message>
<AuthenticationErrorDetail>Signature did not match. String to sign used was stp20220331
r
b
o

2022-08-07T14:33:10Z

2021-06-08

</AuthenticationErrorDetail>
</Error>

Answer 1

Hello @Robson, James - I am glad that you are able to identity the issue from your end. Yeah - that particular ERROR CODE always points to either Incorrect
Storage Account Key
(or)
SAS Key
(or)
Sometimes, there might be some special characters in the SAS Key.

Answer 2

It turns out there was an error in the config settings. Specifically, the STORAGE_ACCOUNT_KEY had an incorrect value.