createPresignedPost upload attempt in results in 400 (Bad Request)

Question

When attempting to use a presigned post url to upload an image to s3, a 400 (Bad Request) response is returned from S3

I'm using the Vercel S3 upload [example](https://github.com/vercel/examples/blob/main/solutions/aws-s3-image-upload/pages/index.tsx) as the pattern

The Lambda function (node js) returning the [presigned](https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/modules/_aws_sdk_s3_presigned_post.html) url is using a user with Administrative Access

S3 has the following CORS policy

```
[
    {
        "AllowedHeaders": [
            "*"
        ],
        "AllowedMethods": [
            "GET",
            "PUT",
            "POST"
        ],
        "AllowedOrigins": [
            "*"
        ],
        "ExposeHeaders": []
    }
]
```
How can I resolve this issue an successfully upload to s3?

Accepted Answer

I was using a customer managed key improperly instead of the s3 managed key. That was the more specific issue

Answer

In my experience, this happens when the request doesn't **exactly** match the presigned URL that was created.

Make sure that you include the content type when signing the URL; and that the content type is the same when you send the request.

Answer

After using Postman, I found out the issue is KMS. Server side encryption was enabled on the bucket and that was causing the error

createPresignedPost upload attempt in results in 400 (Bad Request)

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