如何在 Go 中向 AWS S3 预签名 URL 添加标头？

Question

I'm uploading a file to an AWS S3 bucket using a presigned URL. This works fine, but if I try to add a x-amz-tagging header I get the error "There were headers present in the request which were not signed".

The backend generating the presigned URL is written in Go:

// Upload generates a new URL where a file can be uploaded
func (s *S3) Upload(key string, c Config) (string, error) {
    req, _ := s.client.PutObjectRequest(&s3.PutObjectInput{
        Bucket: aws.String(s.bucketName),
        Key:    aws.String(key),
    })

    return req.Presign(c.ExpiresIn)
}

The answer to S3 presigned upload url error suggests that we need to declare the header as part of the presigned URL. How can I add a header declaration to this? The examples given on Creating Pre-Signed URLs for Amazon S3 Buckets don't cover this.

Answer 1

If i remember correctly, you can add metadata like this:

  'Bucket': 'bucket',
  'Key': 'signed.json',
  'Metadata': {
    'x-amz-tagging': 'whatever'
  },

So it'll look something like this:

// Upload generates a new URL where a file can be uploaded
func (s *S3) Upload(key string, c Config) (string, error) {
    req, _ := s.client.PutObjectRequest(&s3.PutObjectInput{
        Bucket: aws.String(s.bucketName),
        Key:    aws.String(key),
        Body: {
                'x-amz-tagging': 'whatever'
       },
    })

    return req.Presign(c.ExpiresIn)
}

I wrote this on the fly, so it might not work and need a bit of tweaking. Refer to the docs - but it should look like this. Test it out and let me know.

Read more here: https://docs.aws.amazon.com/sdk-for-go/api/service/s3/#PutObjectInput

Answer 2

The presigned URL request just needs the tags under the Tagging field. When you use this URL to make a request, that's when you pass the header with "x-amz-tagging" as the key and the tags (eg, "temp=true&public=yes").

Below is an example of uploading an image with tags (through the headers) using a presigned url that was also requested with tags (with Tagging).

  const uploadImage = async (filepath, presignedURL) => {
    const headers = new Headers();
    headers.append('x-amz-tagging', 'temp=true&public=yes');
    const response = await fetch(filepath);
    const blob = await response.blob();
    return await fetch(
      presignedURL,
      {
        method: 'PUT',
        body: blob,
        headers,
      },
    );
};