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So now we're talking about

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S3 pre-signed URLs, and so we've seen them before,

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but now we're going to do hands-on.

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So we can generate pre-signed URL

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using either the SDK or the CLI.

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And the easy thing to do is for downloads

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you can just use a CLI, but for uploads,

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it's a bit harder and you must use the SDK to use them.

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Nonetheless, it's quite easy

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and we'll do downloads in this lecture.

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Now, when you generate a pre-signed URL,

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by default it will have an expiration of 3,600 seconds,

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which is one hour.

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And you can change that timeout

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using an expires-in parameter, argument,

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and you specify the time in seconds.

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And when the user you give it,

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you give him a pre-signed URL.

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Basically they will inherit your permissions.

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So the one permission that created the object,

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so they can do, get, or put accordingly.

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So why would you do this?

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Well, there's many reasons,

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maybe you want to allow only logged-in users

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to download a premium video on your S3 bucket.

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So you only wanna give a downloading for maybe 15 minutes

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to a premium user that is logged in.

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Maybe you have an ever changing list of users

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that need to download files, and so,

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you don't wanna give them access directly to your bucket

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because it could be very dangerous or it's not maintainable

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because there's so many new users all the time.

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So maybe you want to generate URLs dynamically

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and give them the URLs over time,

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all by pre signing them all of them.

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And then maybe you want to allow temporarily a user

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to upload a file to a precise location in our buckets.

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For example, maybe you want to allow a user to upload

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a profile picture directly onto our S3 bucket.

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And so for this, we would generate a pre-signed URL,

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so there could be a lot of use cases.

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But let's go ahead and see how we can generate

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a pre-signed URL for a download.