S3 Presigned URLs Flashcards
What is an S3 Presigned URL?
An S3 Presigned URL is a URL generated by someone with S3 access permissions, which grants temporary access to a private object in a bucket. This URL contains a signature and token to authenticate the request without needing AWS credentials.
How are S3 Presigned URLs created?
S3 Presigned URLs are created using AWS SDKs or the AWS CLI by specifying the bucket and object name, along with an expiration time after which the URL becomes invalid. The process involves signing the request with the credentials of an authorized AWS account.
For what operations can S3 Presigned URLs be used?
S3 Presigned URLs can be used for both uploading to and downloading from an S3 bucket, making them versatile for temporary access to S3 objects in a secure manner.
What is the default expiration time of an S3 Presigned URL, and how can it be adjusted?
The default expiration time for an S3 Presigned URL is 3600 seconds (1 hour). This can be adjusted by specifying the desired time (in seconds) when generating the URL, up to a maximum of 7 days for a presigned URL created with AWS Signature Version 4.
Can S3 Presigned URLs be used to access objects in a versioned bucket?
Yes, S3 Presigned URLs can access specific versions of an object in a versioned bucket if the version ID of the object is included in the URL parameters during its creation.
How does providing an S3 Presigned URL ensure security?
Providing an S3 Presigned URL ensures security by limiting access to a specified object for a set duration and optionally restricting operations (upload/download). Authentication parameters in the URL verify the request without exposing AWS secret access keys.
Can the expiration time of an existing S3 Presigned URL be modified after it’s been generated?
No, the expiration time of an S3 Presigned URL cannot be modified after it’s been generated. A new URL must be created if a different expiration time is needed.
Are there any limitations or considerations when using S3 Presigned URLs with S3 bucket policies or IAM policies?
Yes, even when using S3 Presigned URLs, the underlying S3 bucket policies and IAM policies still apply. The entity generating the URL must have the necessary permissions, and access will be denied if policies explicitly block it.
What happens when an S3 Presigned URL expires?
When an S3 Presigned URL expires, any request made with that URL will fail with a 403 Forbidden error, indicating that the signature or the provided access credentials are no longer valid.
Can you restrict IP addresses or perform other condition-based restrictions with S3 Presigned URLs?
While the S3 Presigned URL itself does not inherently support IP restrictions or condition-based access directly in the URL, such restrictions can be enforced through S3 bucket policies that evaluate conditions like aws:SourceIp for requests.
