Generate a pre-signed S3 URL (valid for 20 years) with nothing but the standard library.

s3_presign.py

#!/usr/bin/env python

"""
Generates a pre-signed S3 URL using a valid key pair that lasts for 20 years.

Reference: http://forrst.com/posts/Python_method_for_creating_authenticated_s3_URLs-uUM
"""


import base64, hmac, os, sha, sys, time, urllib


if len(sys.argv) < 2:
    print 'USAGE: python s3_presign.py "</bucket-name/path/to/resource"> <seconds-alive>'
    exit(1)


# Declarations:
TWENTY_YEARS_IN_SECONDS = 60 * 60 * 24 * 365 * 20
aws_access_key_id = os.environ.get('AWS_ACCESS_KEY_ID')
aws_secret_access_key = os.environ.get('AWS_SECRET_ACCESS_KEY')
resource = sys.argv[1]
seconds_alive = TWENTY_YEARS_IN_SECONDS if len(sys.argv) < 3 else int(sys.argv[2])


# Computations:
expires = int(time.time()) + seconds_alive
resource = urllib.quote(resource)
raw_value = "GET\n\n\n{0}\n{1}".format(expires, resource)
signature = base64.b64encode(hmac.new(aws_secret_access_key, raw_value, sha).digest())


# Result:
print "https://s3.amazonaws.com{0}?AWSAccessKeyId={1}&Expires={2}&Signature={3}".format(
    resource, urllib.quote(aws_access_key_id), expires, urllib.quote(signature))