AWS File Sharing Services With Temporary Storage - amazon-web-services

I am currently looking for a solution to store temporary files in AWS. I want to create a functionality on my app that allows my customers to upload a file and send it by email (something like WeTranfer or Send Anywhere).
I want to save the file temporarily on my AWS storage, for 10 hours and then remove it permanently. If the file has not expired, the user can click the link (provided by AWS) on the email and download the file.
I recently came across S3 Bucket Lifecycle rules, but I can only specify days for the expiration and not hours.
I would appreciate any suggestion. Thank you!

Amazon S3 is the appropriate place to store these files.
If you want access controls (to control which users can access the file) and fine-grained control over when the object 'expires', then you would need to code this yourself.
The files should be stored in a private Amazon S3 bucket. You would then need a back-end app that manages user authentication. When an authorized user requests access to a file, the app can generate an Amazon S3 pre-signed URL, which provides time-limited access to private objects in Amazon S3 (eg 10 hours). This is the link you would put into the email.
Deletion could still be handled by S3 Lifecycle rules, but it is less important when the file is actually deleted because the pre-signed URL would block access to the file after 10 hours anyway.

Related

AWS S3 Per Bucket Permission for non-AWS accounts

This question is in the same line of thought than Is it possible to give token access to link to amazon s3 storage?.
Basically, we are building an app where groups of users can save pictures, that should be visible only to their own group.
We are thinking of using either a folder per user group, or it could even be an independent S3 bucket per user group.
The rules are very simple:
Any member of Group A should be able to add a picture to the Group A folder (or bucket)
Any member of Group A should be able to read all pictures of the Group A folder (or bucket)
No member of Group A should not have access to any of the pictures
However, the solution used by the post mentioned above (temporary pre-signed URLs) is not usable, as we need the client to be able to write files on his bucket as well as read the files on his bucket, without having any access to any other bucket. The file write part is the difficulty here and the reason why we cannot use pre-signed URLs.
Additionally, the solution from various AWS security posts that we read (for example https://aws.amazon.com/blogs/security/writing-iam-policies-grant-access-to-user-specific-folders-in-an-amazon-s3-bucket/) do not apply because they show how to control accesses for IAM groups of for other AWS accounts. In our case, a group of users does not have an IAM account...
The only solutions that we see so far are either insecure or wasteful
Open buckets to everybody and rely on obfuscating the folder / bucket names (lots of security issues, including the ability to brute force and read / overwrite anybody's files)
Have a back-end that acts as a facade between the app and S3, validating the accesses. S3 has no public access, the bucket is only opened to an IAM role that the back-end has. However this is a big waste of bandwidth, since all the data would transit on the EC2 instance(s) of that back-end
Any better solution?
Is this kind of customized access doable with S3?
The correct way to achieve your goal is to use Amazon S3 pre-signed URLs, which are time-limited URLs that provides temporary access to a private object.
You can also Upload objects using presigned URLs - Amazon Simple Storage Service.
The flow is basically:
Users authenticate to your back-end app
When a user wants to access a private object, the back-end verifies that they are permitted to access the object (using your own business logic, such as the Groups you mention). If they are allowed to access the object, the back-end generates a pre-signed URL.
The pre-signed URL is returned to the user's browser, such as putting it in a <img src="..."> tag.
When the user's browser requests the object, S3 verifies the signature in the pre-signed URL. If it is valid and the time period has not expired, S3 provides the requested object. (Otherwise, it returns Access Denied.)
A similar process is used when users upload objects:
Users authenticate to your back-end app
They request the opportunity to upload a file
Your back-end app generates an S3 Pre-signed URL that is included in the HTML page for upload
Your back-end should track the object in a database so it knows who performed the upload and keeps track of who is permitted to access the object (eg particular users or groups)
Your back-end app is fully responsible for deciding whether particular users can upload/download objects. It then hands-off the actual upload/download process to S3 via the pre-signed URLs. This reduces load on your server because all uploads/downloads go direct to/from S3.

S3: How to grant public write access to an existing bucket file, but not the putObject permission (Private CRUD, Public Read/Update)

So, I want to have a service that creates files in an S3 bucket with specific links, and then allow anyone with a link to a file to write to the file and read it.
But it must not be a public privilege to create files, only editing/reading already existing files, given you have the link.
Is this possible with a bucket policy? Basically allowing one service CRUD privileges but having public RU privileges.
You will need to write such a service yourself.
First, please note that there is no difference between 'Create' and 'Update' in Amazon S3 -- both use a PutObject operation. Objects cannot be 'edited' -- they can only be overwritten.
You can achieve your goal for Reading, by using public objects with obfuscated URLs -- as long as somebody knows the URL, they could access the object. Not a perfect means of security, but that is your choice.
You do not want to grant public permission to create objects in a bucket, otherwise anybody would be able to upload any files to the bucket (eg copyrighted movies) and you would be paying the cost of storage and data transfer.
The safer way to permit uploads is to have users authenticate to your back-end, and then your back-end can generate an Amazon S3 pre-signed URL that can be used to upload to the bucket. This pre-signed URL can specify limitations such as file size and the filename of the upload.
For more details, see: Uploading objects using presigned URLs - Amazon Simple Storage Service

Uploading log file from client app to Amazon S3 is safe?

My application runs on the client PC. It produces log files including error reports and user's action.
To collect and analyze log files, I try to upload log files to Amazon S3 from the client PC.
But is it safe? My app has no authentication so that users can upload unlimited number of files. I am concerned with maricious user upload a fake error report and huge file. I'd like s3 bucket not to exceed free quota. Is there any best practice for this task?
Just make sure that the files you are uploading to Amazon S3 are kept as Private and the Amazon S3 bucket is kept as private. These are the default settings and are enforced by Amazon S3 block public access unless somebody has specifically changed the settings.
With this configuration, the files are only accessible to people with AWS credentials that have been granted permission to access the S3 bucket.
Additionally to John's answer you can use AWS KMS (https://aws.amazon.com/kms/?nc1=h_ls) to encrypt your data at rest.
With regards of the file size, you should limit the size of the uploaded file in your application I would say.

How can I allow a 3rd party file upload to a private S3 bucket without using IAM?

Can I allow a 3rd party file upload to an S3 bucket without using IAM? I would like to avoid the hassle of sending them credentials for an AWS account, but still take advantage of the S3 UI. I have only found solutions for one or the other.
The pre-signed url option sounded great but appears to only work with their SDKs and I'm not about to tell my client to install python on their computer to upload a file.
The browser based upload requires me to make my own front end html form and run in on a server just to upload (lol).
Can I not simply create a pre-signed url which navigates the user to the S3 console and allows them to upload before expiration time? Of course, making the bucket public is not an option either. Why is this so complicated!
Management Console
The Amazon S3 management console will only display S3 buckets that are associated with the AWS account of the user. Also, it is not possible to limit the buckets displayed (it will display all buckets in the account, even if the user cannot access them).
Thus, you certainly don't want to give them access to your AWS management console.
Pre-Signed URL
Your user does not require the AWS SDK to use a pre-signed URL. Rather, you must run your own system that generates the pre-signed URL and makes it available to the user (eg through a web page or API call).
Web page
You can host a static upload page on Amazon S3, but it will not be able to authenticate the user. Since you only wish to provide access to specific people, you'll need some code running on the back-end to authenticate them.
Generate...
You ask: "Can I not simply create a pre-signed url which navigates the user to the S3 console and allows them to upload before expiration time?"
Yes and no. Yes, you can generate a pre-signed URL. However, it cannot be used with the S3 console (see above).
Why is this so complicated?
Because security is important.
So, what to do?
A few options:
Make a bucket publicly writable, but not publicly readable. Tell your customer how to upload. The downside is that anyone could upload to the bucket (if they know about it), so it is only security by obscurity. But, it might be a simple solution for you.
Generate a very long-lived pre-signed URL. You can create a URL that works for months or years. Provide this to them, and they can upload (eg via a static HTML page that you give them).
Generate some IAM User credentials for them, then have them use a utility like the AWS Command-Line Interface (CLI) or Cloudberry. Give them just enough credentials for upload access. This assumes you only have a few customers that need access.
Bottom line: Security is important. Yet, you wish to "avoid the hassle of sending them credentials", nor do you wish to run a system to perform the authentication checks. You can't have security without doing some work, and the cost of poor security will be much more than the cost of implementing good security.
you could deploy a lambda function to call "signed URL" then use that URL to upload the file. here is an example
https://aws.amazon.com/blogs/compute/uploading-to-amazon-s3-directly-from-a-web-or-mobile-application/

How to limit access in Amazon S3 files to specific people?

I work on a SaaS application where Creators can create Groups and invite others to their Group to share files, chat and so on. Only people within specific group should have access to this group's files.
People from other group must not have access to not their group's files.
And of course all files permission should be set to 'Private', i.e. they should not be searchable/visible/accessable by anonymous users of Internet since information in those files is for personal use only.
I am new to Amazon S3 and don't know how to achieve it... Should I create only 1 main bucket? Or create for each group a new Amazon Bucket?
It is not recommended to use AWS Identity and Access Management (IAM) for storing application users. Application users should be maintained in a separate database (or LDAP, Active directory, etc).
Therefore, creating "one bucket per group" is not feasible, since it is not possible to assign your applications users to permissions within Amazon S3.
The better method would be to manage permissions within your application. When a user requests access to a file, the application can determine whether they should be permitted access. If they are permitted, then the application can generate a Pre-Signed URL.
A Pre-Signed URL permits access to private objects stored on Amazon S3. It is a means of keeping objects secure, yet granting temporary access to a specific object.
When listing available files, your application would generate links that include the pre-signed URL. Then, when a user clicks the link, they can access the file. Then, after a certain time has expired (eg 10 minutes), the link will no longer function. So, if a user shares a link with somebody else, it will probably have timed-out.
See: Creating a pre-signed URL in Ruby