Boto3 ListObject Forbidden for Admin User - python-3.x

Question

I have been trying to write a small script to download to lambda /tmp all the content of a S3 folder. To do this I need to list all Objects in a specific bucket. Unfortunately I keep getting the following error;
An error occurred (403) when calling the HeadObject operation: Forbidden
Here is how I try to download all the files from a folder:
#initialize S3
try:
s3 = boto3.resource('s3',
aws_access_key_id=os.getenv('S3USERACCESSKEY'),
aws_secret_access_key=os.getenv('S3USERSECRETKEY')
)
s3_client = boto3.client('s3',
aws_access_key_id=os.getenv('S3USERACCESSKEY'),
aws_secret_access_key=os.getenv('S3USERSECRETKEY')
)
except Exception as e:
logger.error("Could not connect to s3 bucket: " + str(e))
#Function to download whole folders from s3
for s3_key in s3_client.list_objects(Bucket=os.getenv('S3BUCKETNAME'))['Contents']:
s3_object = s3_key['Key']
if not s3_object.endswith("/"):
s3_client.download_file('bucket', s3_object, s3_object)
else:
import os
if not os.path.exists(s3_object):
os.makedirs(s3_object)
The access keys above have full admin rights:
EDIT
Still no success after removing my manual keys, here are the right i attached to Lambda:
Here is the actual error from cloudwatch:
The code now looks like so:
#initialize S3
try:
s3 = boto3.resource('s3')
s3_client = boto3.client('s3')
except Exception as e:
[....]
Seems like "Forbidden" might be another issue then permission but I can't find any doc on it.

Answer 1

Make sure the access key belongs to the user with the IAM role that has rights to access the s3 bucket.
If you run from lambda, there's no need to use an access key, just attach the IAM role to lambda
https://docs.aws.amazon.com/lambda/latest/dg/accessing-resources.html
Did you import boto?
Try to run execute only this:
UPDATE
import boto3
s3 = boto3.resource('s3')
for bucket in s3.buckets.all():
print(bucket.name)