awsauth.py

# awsauth.py for Interoute Object Storage
# See the repo: https://github.com/Interoute/object-storage-api
#
# Source for this file: https://pypi.python.org/pypi/requests-aws/0.1.8
# See also: https://github.com/tax/python-requests-aws
#
# This code provides a class S3Auth to generate authorisation data which can be used with 
# the Python Requests module  (http://docs.python-requests.org).
#
# The code uses AWS Signature Version 2 from the S3 API standard.
#
# Use of the code is explained in the Interoute Object Storage API User Guide:
#  https://cloudstore.interoute.com/knowledge-centre/library/object-storage-api-user-guide
#
# The value of 'service_base_url' has been modified to set a default for
# Interoute Object Storage


# Original License Statement:
'''
Copyright (c) 2012-2013 Paul Tax <paultax@gmail.com> All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

  1. Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
   
  2. Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in
     the documentation and/or other materials provided with the
     distribution.

  3. Neither the name of Infrae nor the names of its contributors may
     be used to endorse or promote products derived from this software
     without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INFRAE OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
'''

import hmac

from hashlib import sha1 as sha
import urllib

py3k = False
try:
    from urlparse import urlparse, unquote
    from base64 import encodestring
except:
    py3k = True
    from urllib.parse import urlparse, unquote
    from base64 import encodebytes as encodestring

from email.utils import formatdate

from requests.auth import AuthBase


class S3Auth(AuthBase):

    """Attaches AWS Authentication to the given Request object."""

    service_base_url = 's3-eu.object.vdc.interoute.com'
    # List of Query String Arguments of Interest
    special_params = [
        'acl', 'location', 'logging', 'partNumber', 'policy', 'requestPayment',
        'torrent', 'versioning', 'versionId', 'versions', 'website', 'uploads',
        'uploadId', 'response-content-type', 'response-content-language',
        'response-expires', 'response-cache-control', 'delete', 'lifecycle',
        'response-content-disposition', 'response-content-encoding', 'tagging',
        'notification', 'cors'
    ]

    def __init__(self, access_key, secret_key, service_url=None):
        if service_url:
            self.service_base_url = service_url
        self.access_key = str(access_key)
        self.secret_key = str(secret_key)

    def __call__(self, r):
        # Create date header if it is not created yet.
        if 'date' not in r.headers and 'x-amz-date' not in r.headers:
            r.headers['date'] = formatdate(
                timeval=None,
                localtime=False,
                usegmt=True)
        signature = self.get_signature(r)
        if py3k:
            signature = signature.decode('utf-8')
        r.headers['Authorization'] = 'AWS %s:%s' % (self.access_key, signature)
        return r

    def get_signature(self, r):
        canonical_string = self.get_canonical_string(
            r.url, r.headers, r.method)
        if py3k:
            key = self.secret_key.encode('utf-8')
            msg = canonical_string.encode('utf-8')
        else:
            key = self.secret_key
            msg = canonical_string
        h = hmac.new(key, msg, digestmod=sha)
        return encodestring(h.digest()).strip()

    def get_canonical_string(self, url, headers, method):
        parsedurl = urlparse(url)
        objectkey = parsedurl.path[1:]
        query_args = sorted(parsedurl.query.split('&'))

        bucket = parsedurl.netloc[:-len(self.service_base_url)]
        if len(bucket) > 1:
            # remove last dot
            bucket = bucket[:-1]

        interesting_headers = {
            'content-md5': '',
            'content-type': '',
            'date': ''}
        for key in headers:
            lk = key.lower()
            try:
                lk = lk.decode('utf-8')
            except:
                pass
            if headers[key] and (lk in interesting_headers.keys()
                                 or lk.startswith('x-amz-')):
                interesting_headers[lk] = headers[key].strip()

        # If x-amz-date is used it supersedes the date header.
        if not py3k:
            if 'x-amz-date' in interesting_headers:
                interesting_headers['date'] = ''
        else:
            if 'x-amz-date' in interesting_headers:
                interesting_headers['date'] = ''

        buf = '%s\n' % method
        for key in sorted(interesting_headers.keys()):
            val = interesting_headers[key]
            if key.startswith('x-amz-'):
                buf += '%s:%s\n' % (key, val)
            else:
                buf += '%s\n' % val

        # append the bucket if it exists
        if bucket != '':
            buf += '/%s' % bucket

        # add the objectkey. even if it doesn't exist, add the slash
        buf += '/%s' % objectkey

        params_found = False

        # handle special query string arguments
        for q in query_args:
            k = q.split('=')[0]
            if k in self.special_params:
                buf += '&' if params_found else '?'
                params_found = True

                try:
                    k, v = q.split('=', 1)

                except ValueError:
                    buf += q

                else:
                    # Riak CS multipart upload ids look like this, `TFDSheOgTxC2Tsh1qVK73A==`,
                    # is should be escaped to be included as part of a query string.
                    #
                    # A requests mp upload part request may look like
                    # resp = requests.put(
                    #     'https://url_here',
                    #     params={
                    #         'partNumber': 1,
                    #         'uploadId': 'TFDSheOgTxC2Tsh1qVK73A=='
                    #     },
                    #     data='some data',
                    #     auth=S3Auth('access_key', 'secret_key')
                    # )
                    #
                    # Requests automatically escapes the values in the `params` dict, so now
                    # our uploadId is `TFDSheOgTxC2Tsh1qVK73A%3D%3D`,
                    # if we sign the request with the encoded value the signature will
                    # not be valid, we'll get 403 Access Denied.
                    # So we unquote, this is no-op if the value isn't encoded.
                    buf += '{key}={value}'.format(key=k, value=unquote(v))

        return buf