From 8d5becbe4b463f6a5a24a1929dd0f48dab6ae027 Mon Sep 17 00:00:00 2001 From: Colleen Murphy Date: Thu, 16 Apr 2020 17:05:43 -0700 Subject: [PATCH] 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 (cherry picked from commit ab89ea749013e7f2c46260f68504f5687763e019) --- keystone/api/_shared/EC2_S3_Resource.py | 31 +++++ keystone/conf/credential.py | 11 +- keystone/tests/unit/test_contrib_ec2_core.py | 125 +++++++++++++++++- .../notes/bug-1872737-f8e1ad3b6705b766.yaml | 28 ++++ 4 files changed, 192 insertions(+), 3 deletions(-) create mode 100644 releasenotes/notes/bug-1872737-f8e1ad3b6705b766.yaml diff --git a/keystone/api/_shared/EC2_S3_Resource.py b/keystone/api/_shared/EC2_S3_Resource.py index 021cf4ad5f..803254816c 100644 --- a/keystone/api/_shared/EC2_S3_Resource.py +++ b/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']) diff --git a/keystone/conf/credential.py b/keystone/conf/credential.py index 3ccf6e633c..2066fbdfbd 100644 --- a/keystone/conf/credential.py +++ b/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 ] diff --git a/keystone/tests/unit/test_contrib_ec2_core.py b/keystone/tests/unit/test_contrib_ec2_core.py index 1242142e01..4b514f8985 100644 --- a/keystone/tests/unit/test_contrib_ec2_core.py +++ b/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', @@ -81,7 +130,7 @@ class EC2ContribCoreV3(test_v3.RestfulTestCase): 'params': { 'SignatureVersion': '2', 'Action': 'Test', - 'Timestamp': '2007-01-31T23:59:59Z' + 'Timestamp': timestamp }, } credentials['signature'] = signer.generate(credentials) @@ -89,3 +138,75 @@ class EC2ContribCoreV3(test_v3.RestfulTestCase): '/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( + '/ec2tokens', + body={'credentials': credentials}, + expected_status=http.client.UNAUTHORIZED) diff --git a/releasenotes/notes/bug-1872737-f8e1ad3b6705b766.yaml b/releasenotes/notes/bug-1872737-f8e1ad3b6705b766.yaml new file mode 100644 index 0000000000..d0732ab4c3 --- /dev/null +++ b/releasenotes/notes/bug-1872737-f8e1ad3b6705b766.yaml @@ -0,0 +1,28 @@ +--- +feature: + - | + [`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 `_] + 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 `_] + 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 `_] + 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.