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Check timestamp of signed EC2 token request

EC2 token requests contain a signature that signs the entire request,
including the access timestamp. While the signature is checked, the
timestamp is not, and so these signed requests remain valid
indefinitely, leaving the token API vulnerable to replay attacks. This
change introduces a configurable TTL for signed token requests and
ensures that the timestamp is actually validated against it.

The check will work for either an AWS Signature v1/v2 'Timestamp'
parameter[1] or the AWS Signature v4 'X-Aws-Date' header or
parameter[2].

Although this technically adds a new feature and the default value of
the feature changes behavior, this change is required to protect
credential holders and therefore must be backported to all supported
branches.

[1] https://docs.aws.amazon.com/general/latest/gr/signature-version-2.html
[2] https://docs.aws.amazon.com/general/latest/gr/sigv4-date-handling.html

Conflicts due to six removal in e2d83ae9:
	keystone/api/_shared/EC2_S3_Resource.py
	keystone/tests/unit/test_contrib_ec2_core.py

Conflicts due to flask reorg:
	keystone/api/_shared/EC2_S3_Resource.py

Change-Id: Idb10267338b4204b435df233c636046a1ce5711f
Closes-bug: #1872737
(cherry picked from commit ab89ea7490)
(cherry picked from commit 8d5becbe4b)
(cherry picked from commit e3f65d6fbc)
(cherry picked from commit 1ef3828516)
changes/85/725385/2
Colleen Murphy 2 months ago
parent
commit
35f09e2b7c
4 changed files with 188 additions and 3 deletions
  1. +10
    -1
      keystone/conf/credential.py
  2. +27
    -0
      keystone/contrib/ec2/controllers.py
  3. +123
    -2
      keystone/tests/unit/test_contrib_ec2_core.py
  4. +28
    -0
      releasenotes/notes/bug-1872737-f8e1ad3b6705b766.yaml

+ 10
- 1
keystone/conf/credential.py View File

@@ -46,12 +46,21 @@ share this repository with the repository used to manage keys for Fernet
tokens.
"""))

auth_ttl = cfg.IntOpt(
'auth_ttl',
default=15,
help=utils.fmt("""
The length of time in minutes for which a signed EC2 or S3 token request is
valid from the timestamp contained in the token request.
"""))


GROUP_NAME = __name__.split('.')[-1]
ALL_OPTS = [
driver,
provider,
key_repository
key_repository,
auth_ttl
]




+ 27
- 0
keystone/contrib/ec2/controllers.py View File

@@ -33,11 +33,13 @@ Glance to list images needed to perform the requested task.
"""

import abc
import datetime
import sys
import uuid

from keystoneclient.contrib.ec2 import utils as ec2_utils
from oslo_serialization import jsonutils
from oslo_utils import timeutils
import six
from six.moves import http_client

@@ -87,6 +89,30 @@ class Ec2ControllerCommon(provider_api.ProviderAPIMixin, object):
raise exception.Unauthorized(
message=_('EC2 signature not supplied.'))

def _check_timestamp(self, credentials):
timestamp = (
# AWS Signature v1/v2
credentials.get('params', {}).get('Timestamp') or
# AWS Signature v4
credentials.get('headers', {}).get('X-Amz-Date') or
credentials.get('params', {}).get('X-Amz-Date')
)
if not timestamp:
# If the signed payload doesn't include a timestamp then the signer
# must have intentionally left it off
return
try:
timestamp = timeutils.parse_isotime(timestamp)
timestamp = timeutils.normalize_time(timestamp)
except Exception as e:
raise exception.Unauthorized(
_('Credential timestamp is invalid: %s') % e)
auth_ttl = datetime.timedelta(minutes=CONF.credential.auth_ttl)
current_time = timeutils.normalize_time(timeutils.utcnow())
if current_time > timestamp + auth_ttl:
raise exception.Unauthorized(
_('Credential is expired'))

@abc.abstractmethod
def authenticate(self, context, credentials=None, ec2Credentials=None):
"""Validate a signed EC2 request and provide a token.
@@ -145,6 +171,7 @@ class Ec2ControllerCommon(provider_api.ProviderAPIMixin, object):
six.reraise(exception.Unauthorized, exception.Unauthorized(e),
sys.exc_info()[2])

self._check_timestamp(credentials)
roles = self.assignment_api.get_roles_for_user_and_project(
user_ref['id'], tenant_ref['id']
)


+ 123
- 2
keystone/tests/unit/test_contrib_ec2_core.py View File

@@ -12,10 +12,15 @@
# License for the specific language governing permissions and limitations
# under the License.

import datetime
import hashlib

from keystoneclient.contrib.ec2 import utils as ec2_utils
from oslo_utils import timeutils
from six.moves import http_client

from keystone.common import provider_api
from keystone.common import utils
from keystone.contrib.ec2 import controllers
from keystone.tests import unit
from keystone.tests.unit import test_v3
@@ -37,6 +42,7 @@ class EC2ContribCoreV3(test_v3.RestfulTestCase):

def test_valid_authentication_response_with_proper_secret(self):
signer = ec2_utils.Ec2Signer(self.cred_blob['secret'])
timestamp = utils.isotime(timeutils.utcnow())
credentials = {
'access': self.cred_blob['access'],
'secret': self.cred_blob['secret'],
@@ -46,7 +52,7 @@ class EC2ContribCoreV3(test_v3.RestfulTestCase):
'params': {
'SignatureVersion': '2',
'Action': 'Test',
'Timestamp': '2007-01-31T23:59:59Z'
'Timestamp': timestamp
},
}
credentials['signature'] = signer.generate(credentials)
@@ -56,6 +62,48 @@ class EC2ContribCoreV3(test_v3.RestfulTestCase):
expected_status=http_client.OK)
self.assertValidProjectScopedTokenResponse(resp, self.user)

def test_valid_authentication_response_with_signature_v4(self):
signer = ec2_utils.Ec2Signer(self.cred_blob['secret'])
timestamp = utils.isotime(timeutils.utcnow())
hashed_payload = (
'GET\n'
'/\n'
'Action=Test\n'
'host:localhost\n'
'x-amz-date:' + timestamp + '\n'
'\n'
'host;x-amz-date\n'
'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'
)
body_hash = hashlib.sha256(hashed_payload.encode()).hexdigest()
amz_credential = (
'AKIAIOSFODNN7EXAMPLE/%s/us-east-1/iam/aws4_request,' %
timestamp[:8])

credentials = {
'access': self.cred_blob['access'],
'secret': self.cred_blob['secret'],
'host': 'localhost',
'verb': 'GET',
'path': '/',
'params': {
'Action': 'Test',
'X-Amz-Algorithm': 'AWS4-HMAC-SHA256',
'X-Amz-SignedHeaders': 'host,x-amz-date,',
'X-Amz-Credential': amz_credential
},
'headers': {
'X-Amz-Date': timestamp
},
'body_hash': body_hash
}
credentials['signature'] = signer.generate(credentials)
resp = self.post(
'/ec2tokens',
body={'credentials': credentials},
expected_status=http_client.OK)
self.assertValidProjectScopedTokenResponse(resp, self.user)

def test_authenticate_with_empty_body_returns_bad_request(self):
self.post(
'/ec2tokens',
@@ -75,6 +123,7 @@ class EC2ContribCoreV3(test_v3.RestfulTestCase):

def test_authenticate_without_proper_secret_returns_unauthorized(self):
signer = ec2_utils.Ec2Signer('totally not the secret')
timestamp = utils.isotime(timeutils.utcnow())
credentials = {
'access': self.cred_blob['access'],
'secret': 'totally not the secret',
@@ -84,8 +133,80 @@ class EC2ContribCoreV3(test_v3.RestfulTestCase):
'params': {
'SignatureVersion': '2',
'Action': 'Test',
'Timestamp': '2007-01-31T23:59:59Z'
'Timestamp': timestamp
},
}
credentials['signature'] = signer.generate(credentials)
self.post(
'/ec2tokens',
body={'credentials': credentials},
expected_status=http_client.UNAUTHORIZED)

def test_authenticate_expired_request(self):
self.config_fixture.config(
group='credential',
auth_ttl=5
)
signer = ec2_utils.Ec2Signer(self.cred_blob['secret'])
past = timeutils.utcnow() - datetime.timedelta(minutes=10)
timestamp = utils.isotime(past)
credentials = {
'access': self.cred_blob['access'],
'secret': self.cred_blob['secret'],
'host': 'localhost',
'verb': 'GET',
'path': '/',
'params': {
'SignatureVersion': '2',
'Action': 'Test',
'Timestamp': timestamp
},
}
credentials['signature'] = signer.generate(credentials)
self.post(
'/ec2tokens',
body={'credentials': credentials},
expected_status=http_client.UNAUTHORIZED)

def test_authenticate_expired_request_v4(self):
self.config_fixture.config(
group='credential',
auth_ttl=5
)
signer = ec2_utils.Ec2Signer(self.cred_blob['secret'])
past = timeutils.utcnow() - datetime.timedelta(minutes=10)
timestamp = utils.isotime(past)
hashed_payload = (
'GET\n'
'/\n'
'Action=Test\n'
'host:localhost\n'
'x-amz-date:' + timestamp + '\n'
'\n'
'host;x-amz-date\n'
'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'
)
body_hash = hashlib.sha256(hashed_payload.encode()).hexdigest()
amz_credential = (
'AKIAIOSFODNN7EXAMPLE/%s/us-east-1/iam/aws4_request,' %
timestamp[:8])

credentials = {
'access': self.cred_blob['access'],
'secret': self.cred_blob['secret'],
'host': 'localhost',
'verb': 'GET',
'path': '/',
'params': {
'Action': 'Test',
'X-Amz-Algorithm': 'AWS4-HMAC-SHA256',
'X-Amz-SignedHeaders': 'host,x-amz-date,',
'X-Amz-Credential': amz_credential
},
'headers': {
'X-Amz-Date': timestamp
},
'body_hash': body_hash
}
credentials['signature'] = signer.generate(credentials)
self.post(


+ 28
- 0
releasenotes/notes/bug-1872737-f8e1ad3b6705b766.yaml View File

@@ -0,0 +1,28 @@
---
feature:
- |
[`bug 1872737 <https://bugs.launchpad.net/keystone/+bug/1872737>`_]
Added a new config option ``auth_ttl`` in the ``[credential]`` config
section to allow configuring the period for which a signed token request
from AWS is valid. The default is 15 minutes in accordance with the AWS
Signature V4 API reference.
upgrade:
- |
[`bug 1872737 <https://bugs.launchpad.net/keystone/+bug/1872737>`_]
Added a default TTL of 15 minutes for signed EC2 credential requests,
where previously an EC2 signed token request was valid indefinitely. This
change in behavior is needed to protect against replay attacks.
security:
- |
[`bug 1872737 <https://bugs.launchpad.net/keystone/+bug/1872737>`_]
Fixed an incorrect EC2 token validation implementation in which the
timestamp of the signed request was ignored, which made EC2 and S3 token
requests vulnerable to replay attacks. The default TTL is 15 minutes but
is configurable.
fixes:
- |
[`bug 1872737 <https://bugs.launchpad.net/keystone/+bug/1872737>`_]
Fixed an incorrect EC2 token validation implementation in which the
timestamp of the signed request was ignored, which made EC2 and S3 token
requests vulnerable to replay attacks. The default TTL is 15 minutes but
is configurable.

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