I understand that you can grant read/write to internal AWS account resources like lambda when you turn off public access. However what if I need to be able to read an S3 object from an external host, via the S3 URL? Sure I know I could add a public API endpoint to serve up the S3 asset. However if I use something like <img src=""/> that doesn't help me. If I try to perform a GET on the S3 url at this point, I get a 403. I'm wondering in this case that I have to leave 'public access' on?
There are two ways to access objects in private Amazon S3 buckets.
Use S3 API calls
You can use API calls using the AWS CLI or an AWS SDK. These API calls require AWS credentials that have GetObject permission to access the bucket. They do not require the bucket to be public.
Use a pre-signed URL
Alternatively, you can generate an Amazon S3 pre-signed URL, which provides time-limited access to private objects in Amazon S3. The URL can be used in <img src=...> tags.
The pre-signed URL can be generated in a few lines of code without the need to call AWS. It is basically a hashed signature that uses some AWS credentials to authorise access to the private object. This option appears most suitable for your use-case.
Related
My website has some files hosted on AWS S3 buckets, but I need to restrict access to the s3 objects URL to only logged in users of the website. Something similar to how google drive works. which means that anyone trying to access the urls to any of the files on our S3 bucket needs to be logged into the website before he or she would be able to.
Is this possible?
Thanks
If you want to restrict access to the S3 objects, don't make the objects public and don't use the public URLs shown on AWS S3 console.
S3 provides an option to generate pre-signed URLs to download S3 objects. So once your users log in to your website and when they request to download the S3 object, make a request to S3 to generate this pre-signed URL. Clicking on the pre-signed URL will download the object.
With pre-signed URLs, you can configure additional options like expiry time, so that these URLs are more secure.
You can find more info about pre-signed URLs and their implementation here.
If you happen to use AWS Cognito for log in/out functionality, you can assign IAM roles to logged in users.
This way when trying to access the s3 bucket, you can restrict access using IAM roles.
AWS Amplify would be a good fit for this use-case.
I have uploaded Images in AWS S3 Bucket. How can we access those private content securely.
One possible solution is to create a lambda#edge function (possible only in the us-east-1 region) that will be triggered by your CloudFront distribution.
Specify a behavior path pattern for example "/images".
To securely access your images, add an authorizer to your lambda function,
you could use Cognito for that, and authenticate users at the front end
(sign-Up/sign-In), using AWS amplify/auth module.
Use Case:
I want to be able to:
Upload images and audio files from my backend to S3 bucket
List and view/play content on my backend
Return the objects URLs in API responses
Mobile apps can view/play the URLs with or without? authentication from the mobile side
Is that possible without making the S3 bucket public ?
Is that possible without making the S3 bucket public ?
Yes, it should be possible. Since you are using EC2 instance for backend, you, you can setup instance role to enable private and secure access of your backed application to S3. In the role, you would allow S3 read/write. This way, if your application is using AWS SDK, you can seamlessly access S3 without making S3 public.
Regarding the links to the object, the general way is to return S3 pre-signed links. This allows for temporary access to your objects without the need for public access. The alternative is to share your objects through CloudFront as explained in Amazon S3 + Amazon CloudFront: A Match Made in the Cloud. In either case, bucket can be private.
I have provided AmazonS3FullAccess policy for both the IAM user and group. Also the buket that I am trying to access says "Objects can be public". I have explicitly made the folder inside the bucket public. Despite all this I am getting access denied error when I tried to access it through its url. Any idea on this?
Objects in Amazon S3 are private by default. This means that objects are not accessible by anonymous users.
You have granted permission for your IAM User to be able to access S3. Therefore, you have access to the objects but you must identify yourself to S3 so that it can verify your identity.
You should be able to access S3 content:
Via the Amazon S3 management console
Using the AWS CLI (eg aws s3 ls s3://bucketname)
Via authenticated requests in a web browser
I suspect that you have been accessing your bucket via an unauthenticated request (eg bucketname.s3.amazonaws.com/foo.txt. Unfortunately, this does not tell Amazon S3 who you are, so it will deny the request.
To access content with this type of URL, you can generate an Amazon S3 pre-signed URLs, which appends some authentication information to the URL to prove your identity. An easy way to generate the URL is with the AWS CLI:
aws s3 presign s3://bucketname/foo.txt
It will return a URL that looks like this:
https://bucketname.s3.amazonaws.com/foo.txt?AWSAccessKeyId=AKIAxxx&Signature=xxx&Expires=1608175109
The URL will be valid for one hour by default, up to 7 days.
There are two ways I will recommend.
go to s3 dashboard, and download the object you need, one by one manually, the bucket can be kept private at the same time.
build a gateway/a small service, to handle authentication for you, set a policy and give the permission to the service container/lambda to visit the private bucket, and restrict only specific users to download the objects.
References
download from aws s3
aws policy, permission and roles
I am storing files in a S3 bucket. I want the access to the files be restricted.
Currently, anyone with the URL to the file is able to access the file.
I want a behavior where file is accessed only when it is accessed through my application. The application is hosted on EC2.
Following are 2 possible ways I could find.
Use "referer" key in bucket policy.
Change "allowed origin" in CORS configuration
Which of the above 2 should be used, given the fact that 'referer' could be spoofed in the request header.
Also can cloudfront play a role over here?
I would recommend using a Pre-Signed URL that permits access to private objects stored on Amazon S3. It is a means of keeping objects secure, yet grant temporary access to a specific object.
It is created via a hash calculation based on the object path, expiry time and a shared Secret Access Key belonging to an account that has permission to access the Amazon S3 object. The result is a time-limited URL that grants access to the object. Once the expiry time passes, the URL does not return the object.
Start by removing existing permissions that grant access to these objects. Then generate Pre-Signed URLs to grant access to private content on a per-object basis, calculated every time you reference an S3 object. (Don't worry, it's fast to do!)
See documentation: Sample code in Java
When dealing with a private S3 bucket, you'll want to use an AWS SDK appropriate for your use case.
Here lies SDKs for many different languages: http://aws.amazon.com/tools/
Within each SDK, you can find sample calls to S3.
If you are trying to make private calls via browser-side JavaScript, you can use CORS.