Signed URLs for private objects in Spaces

Posted on September 20, 2017

Hi,

I currently have a set of files on S3 that are private. I need to temporarily generate a public, signed URL. This works with the boto API (see the code at the end). How can I do this programmatically with Spaces?

Code example:

conn = S3Connection(access_key, secret_key)

return conn.generate_url(
    expires_in=expiry_in_sec,
    method='GET',
    bucket=MediaService.__find_bucket_name_from_url(raw_url),
    key=MediaService.__find_path_from_url(raw_url),
    query_auth=True,
    force_http=(not https)
)

Does the S3 compatibility work for generate_url?

Thanks, Michael

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Andrew SB

September 21, 2017

Accepted Answer

Currently pre-signed URLs generated using the AWS v4 signature type are not supported. Unfortunately, v4 signatures are the default in most places, so this can cause some issues. Luckily, most clients allow you to override this.

Using boto3, you can configure your session to use the v2 signature type with:

import boto3
from botocore.client import Config

session = boto3.session.Session()

client = session.client('s3',
                        region_name='nyc3',
                        endpoint_url='https://nyc3.digitaloceanspaces.com',
                        aws_access_key_id='MYACCESSKEY',
                        aws_secret_access_key='MYSECRETKEY',
                        config=Config(signature_version='s3'))

(Passing s3 as the value for signature_version will force v3 signature. While v4 is the defualt, you can explicitly use it by passing s3v4.)

Then you can generate a functioning pre-signed url using:

url = client.generate_presigned_url(ClientMethod='get_object', 
                                    Params={'Bucket': 'my-bucket',
                                            'Key': 'my-object'},
                                    ExpiresIn=300)

Note the ExpiresIn argument. By default, pre-signed URLs will expire in an hour (3600 seconds). This example sets it to expire in 5 minutes. See the boto3 docs for more info.