s3api: Prevent XXE injections
Previously, clients could use XML external entities (XXEs) to read
arbitrary files from proxy-servers and inject the content into the
request. Since many S3 APIs reflect request content back to the user,
this could be used to extract any secrets that the swift user could
read, such as tempauth credentials, keymaster secrets, etc.
Now, disable entity resolution -- any unknown entities will be replaced
with an empty string. Without resolving the entities, the request is
still processed.
[CVE-2022-47950]
Closes-Bug: #1998625
Co-Authored-By: Romain de Joux <romain.de-joux@ovhcloud.com>
Change-Id: I84494123cfc85e234098c554ecd3e77981f8a096
(cherry picked from commit b8467e190f)
This commit is contained in:
Aymeric Ducroquetz
Tim Burke
parent
91144596c6
commit
70b68dbf65
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@ -130,7 +130,7 @@ class _Element(lxml.etree.ElementBase):
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parser_lookup = lxml.etree.ElementDefaultClassLookup(element=_Element)
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parser = lxml.etree.XMLParser()
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parser = lxml.etree.XMLParser(resolve_entities=False, no_network=True)
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parser.set_element_class_lookup(parser_lookup)
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Element = parser.makeelement
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@ -0,0 +1,210 @@
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#!/usr/bin/env python
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# Copyright (c) 2022 OpenStack Foundation
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import requests
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import botocore
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import test.functional as tf
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from test.functional.s3api import S3ApiBaseBoto3
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def setUpModule():
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tf.setup_package()
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def tearDownModule():
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tf.teardown_package()
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class TestS3ApiXxeInjection(S3ApiBaseBoto3):
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def setUp(self):
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super(TestS3ApiXxeInjection, self).setUp()
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self.bucket = 'test-s3api-xxe-injection'
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def _create_bucket(self, **kwargs):
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resp = self.conn.create_bucket(Bucket=self.bucket, **kwargs)
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response_metadata = resp.pop('ResponseMetadata', {})
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self.assertEqual(200, response_metadata.get('HTTPStatusCode'))
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@staticmethod
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def _clear_data(request, **_kwargs):
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if 'Content-MD5' in request.headers:
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del request.headers['Content-MD5']
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request.data = b''
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def _presign_url(self, method, key=None, **kwargs):
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params = {
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'Bucket': self.bucket
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}
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if key:
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params['Key'] = key
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params.update(kwargs)
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try:
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# https://github.com/boto/boto3/issues/2192
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self.conn.meta.events.register(
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'before-sign.s3.*', self._clear_data)
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return self.conn.generate_presigned_url(
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method, Params=params, ExpiresIn=60)
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finally:
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self.conn.meta.events.unregister(
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'before-sign.s3.*', self._clear_data)
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def test_put_bucket_acl(self):
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if not tf.cluster_info['s3api'].get('s3_acl'):
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self.skipTest('s3_acl must be enabled')
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self._create_bucket()
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url = self._presign_url('put_bucket_acl')
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resp = requests.put(url, data="""
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<!DOCTYPE foo [<!ENTITY xxe SYSTEM "file:///etc/swift/swift.conf"> ]>
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<AccessControlPolicy xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
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<Owner>
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<DisplayName>test:tester</DisplayName>
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<ID>test:tester</ID>
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</Owner>
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<AccessControlList>
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<Grant>
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<Grantee xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="CanonicalUser">
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<DisplayName>name&xxe;</DisplayName>
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<ID>id&xxe;</ID>
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</Grantee>
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<Permission>WRITE</Permission>
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</Grant>
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</AccessControlList>
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</AccessControlPolicy>
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""") # noqa: E501
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self.assertEqual(200, resp.status_code)
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self.assertNotIn(b'xxe', resp.content)
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self.assertNotIn(b'[swift-hash]', resp.content)
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acl = self.conn.get_bucket_acl(Bucket=self.bucket)
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response_metadata = acl.pop('ResponseMetadata', {})
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self.assertEqual(200, response_metadata.get('HTTPStatusCode'))
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self.assertDictEqual({
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'Owner': {
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'DisplayName': 'test:tester',
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'ID': 'test:tester'
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},
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'Grants': [
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{
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'Grantee': {
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'DisplayName': 'id',
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'ID': 'id',
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'Type': 'CanonicalUser'
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},
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'Permission': 'WRITE'
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}
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]
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}, acl)
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def test_create_bucket(self):
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url = self._presign_url('create_bucket')
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resp = requests.put(url, data="""
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<!DOCTYPE foo [<!ENTITY xxe SYSTEM "file:///etc/swift/swift.conf"> ]>
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<CreateBucketConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
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<LocationConstraint>&xxe;</LocationConstraint>
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</CreateBucketConfiguration>
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""") # noqa: E501
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self.assertEqual(400, resp.status_code)
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self.assertNotIn(b'xxe', resp.content)
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self.assertNotIn(b'[swift-hash]', resp.content)
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self.assertRaisesRegexp(
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botocore.exceptions.ClientError, 'Not Found',
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self.conn.head_bucket, Bucket=self.bucket)
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def test_delete_objects(self):
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self._create_bucket()
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url = self._presign_url(
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'delete_objects',
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Delete={
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'Objects': [
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{
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'Key': 'string',
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'VersionId': 'string'
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}
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]
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})
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body = """
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<!DOCTYPE foo [<!ENTITY xxe SYSTEM "file:///etc/swift/swift.conf"> ]>
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<Delete xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
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<Object>
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<Key>&xxe;</Key>
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</Object>
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</Delete>
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"""
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body = body.encode('utf-8')
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resp = requests.post(url, data=body)
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self.assertEqual(400, resp.status_code, resp.content)
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self.assertNotIn(b'xxe', resp.content)
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self.assertNotIn(b'[swift-hash]', resp.content)
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def test_complete_multipart_upload(self):
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self._create_bucket()
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resp = self.conn.create_multipart_upload(
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Bucket=self.bucket, Key='test')
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response_metadata = resp.pop('ResponseMetadata', {})
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self.assertEqual(200, response_metadata.get('HTTPStatusCode'))
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uploadid = resp.get('UploadId')
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try:
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url = self._presign_url(
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'complete_multipart_upload',
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Key='key',
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MultipartUpload={
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'Parts': [
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{
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'ETag': 'string',
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'PartNumber': 1
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}
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],
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},
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UploadId=uploadid)
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resp = requests.post(url, data="""
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<!DOCTYPE foo [<!ENTITY xxe SYSTEM "file:///etc/swift/swift.conf"> ]>
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<CompleteMultipartUpload xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
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<Part>
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<ETag>"{uploadid}"</ETag>
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<PartNumber>&xxe;</PartNumber>
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</Part>
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</CompleteMultipartUpload>
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""") # noqa: E501
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self.assertEqual(404, resp.status_code)
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self.assertNotIn(b'xxe', resp.content)
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self.assertNotIn(b'[swift-hash]', resp.content)
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resp = requests.post(url, data="""
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<!DOCTYPE foo [<!ENTITY xxe SYSTEM "file:///etc/swift/swift.conf"> ]>
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<CompleteMultipartUpload xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
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<Part>
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<ETag>"&xxe;"</ETag>
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<PartNumber>1</PartNumber>
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</Part>
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</CompleteMultipartUpload>
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""") # noqa: E501
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self.assertEqual(404, resp.status_code)
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self.assertNotIn(b'xxe', resp.content)
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self.assertNotIn(b'[swift-hash]', resp.content)
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finally:
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resp = self.conn.abort_multipart_upload(
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Bucket=self.bucket, Key='test', UploadId=uploadid)
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response_metadata = resp.pop('ResponseMetadata', {})
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self.assertEqual(204, response_metadata.get('HTTPStatusCode'))
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@ -396,6 +396,45 @@ class TestS3ApiMultiDelete(S3ApiTestCase):
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elem = fromstring(body)
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self.assertEqual(len(elem.findall('Deleted')), len(self.keys))
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def test_object_multi_DELETE_with_system_entity(self):
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self.keys = ['Key1', 'Key2']
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self.swift.register(
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'DELETE', '/v1/AUTH_test/bucket/%s' % self.keys[0],
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swob.HTTPNotFound, {}, None)
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self.swift.register(
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'DELETE', '/v1/AUTH_test/bucket/%s' % self.keys[1],
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swob.HTTPNoContent, {}, None)
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elem = Element('Delete')
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for key in self.keys:
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obj = SubElement(elem, 'Object')
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SubElement(obj, 'Key').text = key
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body = tostring(elem, use_s3ns=False)
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body = body.replace(
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b'?>\n',
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b'?>\n<!DOCTYPE foo '
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b'[<!ENTITY ent SYSTEM "file:///etc/passwd"> ]>\n',
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).replace(b'>Key1<', b'>Key1&ent;<')
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content_md5 = (
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base64.b64encode(md5(body).digest())
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.strip())
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req = Request.blank('/bucket?delete',
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environ={'REQUEST_METHOD': 'POST'},
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headers={
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'Authorization': 'AWS test:full_control:hmac',
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'Date': self.get_date_header(),
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'Content-MD5': content_md5},
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body=body)
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req.date = datetime.now()
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req.content_type = 'text/plain'
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status, headers, body = self.call_s3api(req)
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self.assertEqual(status, '200 OK', body)
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self.assertIn(b'<Deleted><Key>Key2</Key></Deleted>', body)
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self.assertNotIn(b'root:/root', body)
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self.assertIn(b'<Deleted><Key>Key1</Key></Deleted>', body)
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def _test_no_body(self, use_content_length=False,
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use_transfer_encoding=False, string_to_md5=b''):
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content_md5 = base64.b64encode(md5(string_to_md5).digest()).strip()
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