A script to iterate through a bucket and change object acl's.

s3_object_acl.py

#!/usr/bin/env python
import boto3

client = boto3.client('s3')
bucket = 'your-bucket'
prefix = 'a-path-in-s3'
NextContinuationToken = True

while NextContinuationToken:
	if NextContinuationToken == True:
		response = client.list_objects_v2(Bucket=bucket,Prefix=prefix)
	else:
		response = client.list_objects_v2(Bucket=bucket,Prefix=prefix,ContinuationToken=NextContinuationToken)
	NextContinuationToken = response['NextContinuationToken']
	contents = response['Contents']
	for k in contents:
		try:
			client.put_object_acl(Bucket=bucket,Key=k['Key'],ACL='bucket-owner-full-control')
		except:
			print response['NextContinuationToken']
			print "Couldn't change permissions for key {}".format(k)