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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

Change-Id: Idb10267338b4204b435df233c636046a1ce5711f
Closes-bug: #1872737
changes/24/724124/1
Colleen Murphy 1 year ago
parent
commit
ab89ea7490
  1. 31
      keystone/api/_shared/EC2_S3_Resource.py
  2. 11
      keystone/conf/credential.py
  3. 125
      keystone/tests/unit/test_contrib_ec2_core.py
  4. 28
      releasenotes/notes/bug-1872737-f8e1ad3b6705b766.yaml

31
keystone/api/_shared/EC2_S3_Resource.py

@ -12,15 +12,20 @@
# Common base resource for EC2 and S3 Authentication
import datetime
from oslo_serialization import jsonutils
from oslo_utils import timeutils
from werkzeug import exceptions
from keystone.common import provider_api
from keystone.common import utils
import keystone.conf
from keystone import exception as ks_exceptions
from keystone.i18n import _
from keystone.server import flask as ks_flask
CONF = keystone.conf.CONF
PROVIDERS = provider_api.ProviderAPIs
CRED_TYPE_EC2 = 'ec2'
@ -36,6 +41,31 @@ class ResourceBase(ks_flask.ResourceBase):
# the ABC module.
raise NotImplementedError()
@staticmethod
def _check_timestamp(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 ks_exceptions.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 ks_exceptions.Unauthorized(
_('Credential is expired'))
def handle_authenticate(self):
# TODO(morgan): convert this dirty check to JSON Schema validation
# this mirrors the previous behavior of the webob system where an
@ -101,6 +131,7 @@ class ResourceBase(ks_flask.ResourceBase):
except AssertionError as e:
raise ks_exceptions.Unauthorized from e
self._check_timestamp(credentials)
roles = PROVIDERS.assignment_api.get_roles_for_user_and_project(
user_ref['id'], project_ref['id'])

11
keystone/conf/credential.py

@ -61,6 +61,14 @@ Time to cache credential data in seconds. This has no effect unless global
caching is enabled.
"""))
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 = [
@ -68,7 +76,8 @@ ALL_OPTS = [
provider,
key_repository,
caching,
cache_time
cache_time,
auth_ttl
]

125
keystone/tests/unit/test_contrib_ec2_core.py

@ -12,10 +12,15 @@
# License for the specific language governing permissions and limitations
# under the License.
import datetime
import hashlib
import http.client
from keystoneclient.contrib.ec2 import utils as ec2_utils
from oslo_utils import timeutils
from keystone.common import provider_api
from keystone.common import utils
from keystone.tests import unit
from keystone.tests.unit import test_v3
@ -34,6 +39,7 @@ 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'],
@ -43,7 +49,7 @@ class EC2ContribCoreV3(test_v3.RestfulTestCase):
'params': {
'SignatureVersion': '2',
'Action': 'Test',
'Timestamp': '2007-01-31T23:59:59Z'
'Timestamp': timestamp
},
}
credentials['signature'] = signer.generate(credentials)
@ -53,6 +59,48 @@ 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',
@ -72,6 +120,7 @@ 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',
@ -81,8 +130,80 @@ 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
releasenotes/notes/bug-1872737-f8e1ad3b6705b766.yaml

@ -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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