If there are files to be uploaded, we need pre-signed URLs. To learn about different ways of splitting a list into smaller sublists, check this article. Now that we have created our batches, the next step is to generate pre-signed URL. For simplicity, I am just generating pre-signed URLs for one list of files.
Therefore, ensure we provide only file names to the pre-signed URL generation service. If you provide an absolute path, the uploaded file names will be the respective absolute paths.
Now that we have the pre-signed URLs, we shall upload them to s3 bucket. So now that we have prepared all our files to upload, only task pending is to post the files using the pre-signed URLs. If you wish to display progress bar for your uploads, please refer here. Posted in Tech. Posted by By dineshkumarkb September 8, Introduction: This article explains how to upload multiple files to aws s3 in batches using pre-signed URL.
The objective is to ensure that every pre signed URL is only ever used once, and becomes unavailable after the first use. I had a few different ideas for the implementation until I settled on one that seemed to be the most efficient at achieving our objective.
Figure 1. Presigned URL creation. A hash is then created from the URL and saved to the bucket step 4, Figure 1 as a valid signature. The Lambda function creates a response which contains the URL step 5, Figure 1 and returns it to the user step 6, Figure 1.
Figure 2. Verification of the presigned URL. The user then uses that URL to upload the file step 1, Figure 2. A Cloudfront viewer request triggers a Lambda function step 2, Figure 2 which verifies that the hashed URL is indexed as a valid token and is not indexed as an expired token step 3, Figure 2.
If we have a match from both conditions, the current hash is written to the expired signatures index step 4, Figure 2. In addition to that, the version of the expired signature object is checked. If this is the first version of this particular expired hash everything is ok step 5, Figure 2. This check is meant to prevent someone intercepting the original response with a signed URL and using it before the legitimate client has had a chance to. After all the verifications have successfully passed, the original request is returned to Cloudfront step 6, Figure 2 and to the bucket step 7, Figure 2 , which then decides if the presigned URL is valid for PUTting the object.
The S3 bucket will contain the uploaded files and an index of used signatures. There no need for bucket policy, ACLs, or anything else; the bucket is private and cannot be accessed from outside without a pre signed URL. Functions have a role which allows them to generate the presigned URL, check if the URL hash is in the valid index and add it if not. The bucket and CloudFront distribution are defined in the resources block of the serverless. Since we cannot pass configuration values via environment variables since Lambda Edge functions cannot access environment variables , the bucket name is stored and fetched from an external json file.
S3 allows files up to 5 gigabytes to be uploaded with that method, although it is better to use multipart upload for files bigger than megabytes.
For simplicity, this example uses only PUT. Cloudfront should also forward the query string which contains the signature and token for the upload. The origin contains only the domain name, which is the bucket name, and id. The S3OriginConfig is an empty object because the bucket will be private. Active Oldest Votes. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.
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