In general, the completed image-upload process follows these steps:. This guide includes information on how to implement the client-side and server-side code to form the complete system. After following the guide, you should have a working barebones system, allowing your users to upload files to S3. However, it is usually worth adding extra functionality to help improve the security of the system and to tailor it for your own particular uses.
Pointers for this are mentioned in the appropriate parts of the guide. During the first few hours after a bucket has been created S3 may return redirects in response to upload requests. If you notice this behaviour, then waiting a short while for your new bucket to completely settle should fix the problem. In order for your application to access the AWS credentials for signing upload requests, they will need to be added as configuration variables in Heroku:.
Using config vars is preferable over configuration files for security reasons. You will now need to edit some of the permissions properties of the target S3 bucket so that the final request has sufficient privileges to write to the bucket. In a web-browser, sign in to the AWS console and select the S3 section. Select the appropriate bucket and click the Permissions tab.
Setting up the bucket in this way allows us to read its contents without signed URLs, but this may not be suitable for services running in production. Each rule should specify a set of domains from which access to the bucket is granted and also the methods and headers permitted from those domains. This tells S3 to allow any domain access to the bucket and that requests can contain any headers.
If you wish to use S3 credentials specifically for this application, then more keys can be generated in the AWS account pages. This provides further security, since you can designate a very specific set of requests that this set of keys are able to perform. If this is preferable to you, then you will need to also set up an IAM user in the Edit bucket policy option in your S3 bucket.
The processes and steps required to accomplish a direct upload to S3 will be demonstrated through the use of a simple profile-editing scenario for the purposes of this article. This example will involve the user being permitted to select an avatar image to upload and enter some basic information to be stored as part of their account. If you're on Rails 4, you should use 1.
Check out this file for some hints on how you can customize your uploader. It should look something like this:. CarrierWave gives you a store for permanent storage, and a cache for temporary storage.
You can use different stores, including filesystem and cloud storage. It is quite simple to mount uploaders on columns in your model, so you can simply assign files and get going:. Make sure you are loading CarrierWave after loading your ORM, otherwise you'll need to require the relevant extension manually, e.
Add a string column to the model you want to mount the uploader by creating a migration:. Now you can cache files by assigning them to the attribute, they will automatically be stored when the record is saved. Note : u. To check if a photo was saved to the model, use u. There are more extensions listed in the wiki. Add a column which can store an array. This could be an array column or a JSON column for example. Your choice depends on what your database supports.
For example, create a migration like this:. Make sure your file input fields are set up as multiple file fields. For example in Rails you'll want to do something like this:. Also, make sure your upload controller permits the multiple file upload attribute, pointing to an empty array in a hash. For example:. Now you can select multiple files in the upload dialog e.
Certain files might be dangerous if uploaded to the wrong location, such as PHP files or other script files. CarrierWave allows you to specify an allowlist of allowed extensions or content types. If you're mounting the uploader, uploading a file with the wrong extension will make the record invalid instead. Otherwise, an error is raised. The same thing could be done using content types.
Let's say we need an uploader that accepts only images. This can be done like this. You can use a denylist to reject content types. Let's say we need an uploader that reject JSON files. A valid allowlist that will restrict your uploader to images only, and mitigate the CVE is:.
By default, CarrierWave provides only English letters, arabic numerals and some symbols as allowlisted characters in the file name. It should return regular expression which would match all non -allowed symbols.
Also make sure that allowing non-latin characters won't cause a compatibility issue with a third-party plugins or client-side software. As of v0. You no longer need to do this manually. Often you'll want to add different versions of the same file. The classic example is image thumbnails. You no longer have to convert the contents to binary before writing to the file in S3.
The following example creates a new text file called newfile. Now you can use json. A cleaner and concise version which I use to upload files on the fly to a given S3 bucket and sub-folder-. You may use the below code to write, for example an image to S3 in To be able to connect to S3 you will have to install AWS CLI using command pip install awscli , then enter few credentials using command aws configure :.
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Learn more. How to write a file or data to an S3 object using boto3 Ask Question. Asked 5 years ago. Active 10 months ago.
Viewed k times. In boto 2, you can write to an S3 object using these methods: Key. Add a comment. Active Oldest Votes. In boto 3, the 'Key. Take a look at the picture, you see the word "FAIL".
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