Ignore downstream version flag (#181)

* Ignore downstream version flag

This commit adds `--ignore-downstream` flag to kube-hunter.
Enabling the flag will make kube-hunter considering patched versions
as not vulnerable.
Resolves #179

* Add test cases and refine argument description

kube-hunter.py

@@ -9,6 +9,7 @@ parser.add_argument('--list', action="store_true", help="displays all tests in k
 parser.add_argument('--interface', action="store_true", help="set hunting of all network interfaces")
 parser.add_argument('--pod', action="store_true", help="set hunter as an insider pod")
 parser.add_argument('--quick', action="store_true", help="Prefer quick scan (subnet 24)")
+parser.add_argument('--ignore-downstream', action="store_true", help="Ignore patched kubernetes versions")
 parser.add_argument('--cidr', type=str, help="set an ip range to scan, example: 192.168.0.0/16")
 parser.add_argument('--mapping', action="store_true", help="outputs only a mapping of the cluster's nodes")
 parser.add_argument('--remote', nargs='+', metavar="HOST", default=list(), help="one or more remote ip/dns to hunt")

runtest.py

@@ -6,6 +6,7 @@ parser.add_argument('--list', action="store_true", help="displays all tests in k
 parser.add_argument('--interface', action="store_true", help="set hunting of all interface network interfaces")
 parser.add_argument('--pod', action="store_true", help="set hunter as an insider pod")
 parser.add_argument('--quick', action="store_true", help="Prefer quick scan (subnet 24)")
+parser.add_argument('--ignore-downstream', action="store_true", help="Ignore patched kubernetes versions")
 parser.add_argument('--cidr', type=str, help="set an ip range to scan, example: 192.168.0.0/16")
 parser.add_argument('--mapping', action="store_true", help="outputs only a mapping of the cluster's nodes")
 parser.add_argument('--remote', nargs='+', metavar="HOST", default=list(), help="one or more remote ip/dns to hunt")

src/modules/hunting/cves.py

@@ -2,6 +2,8 @@ import logging
 import json
 import requests
 
+from __main__ import config
+
 from ...core.events import handler
 from ...core.events.types import Vulnerability, Event, K8sVersionDisclosure
 from ...core.types import Hunter, ActiveHunter, KubernetesCluster, RemoteCodeExec, AccessRisk, InformationDisclosure, \
@@ -95,8 +97,15 @@ class CveUtils:
         return (v1>v2)-(v1<v2)
 
     @staticmethod
-    def is_vulnerable(fix_versions, check_version):
+    def is_downstream_version(version):
+        return any(c in version for c in '+-~')
+
+    @staticmethod
+    def is_vulnerable(fix_versions, check_version, ignore_downstream=False):
         """Function determines if a version is vulnerable, by comparing to given fix versions by base release"""
+        if ignore_downstream and CveUtils.is_downstream_version(check_version):
+            return False
+
         vulnerable = False
         check_v = version.parse(check_version)
         base_check_v = CveUtils.get_base_release(check_v)
@@ -146,7 +155,7 @@ class K8sClusterCveHunter(Hunter):
             ServerApiClusterScopedResourcesAccess: ["1.13.9", "1.14.5", "1.15.2"]
         }        
         for vulnerability, fix_versions in cve_mapping.items():
-            if CveUtils.is_vulnerable(fix_versions, self.event.version):
+            if CveUtils.is_vulnerable(fix_versions, self.event.version, config.ignore_downstream):
                 self.publish_event(vulnerability(self.event.version))
 
 
@@ -165,5 +174,5 @@ class KubectlCVEHunter(Hunter):
         }
         logging.debug('Kubectl Cve Hunter determining vulnerable version: {}'.format(self.event.version))
         for vulnerability, fix_versions in cve_mapping.items():
-            if CveUtils.is_vulnerable(fix_versions, self.event.version):
+            if CveUtils.is_vulnerable(fix_versions, self.event.version, config.ignore_downstream):
                 self.publish_event(vulnerability(binary_version=self.event.version))

tests/hunting/test_cvehunting.py

@@ -3,7 +3,7 @@ import requests_mock
 
 from src.core.events import handler
 from src.core.events.types import K8sVersionDisclosure
-from src.modules.hunting.cves import K8sClusterCveHunter, ServerApiVersionEndPointAccessPE, ServerApiVersionEndPointAccessDos
+from src.modules.hunting.cves import K8sClusterCveHunter, ServerApiVersionEndPointAccessPE, ServerApiVersionEndPointAccessDos, CveUtils
 
 cve_counter = 0
 
@@ -49,4 +49,41 @@ class test_CVE_2018_1002105(object):
 class test_CVE_2019_1002100(object):
     def __init__(self, event):
         global cve_counter
-        cve_counter += 1
+        cve_counter += 1
+
+class test_CveUtils(object):
+    def test_is_downstream():
+        test_cases = (
+            ('1', False),
+            ('1.2', False),
+            ('1.2-3', True),
+            ('1.2-r3', True),
+            ('1.2+3', True),
+            ('1.2~3', True),
+            ('1.2+a3f5cb2', True),
+            ('1.2-9287543', True),
+            ('v1', False),
+            ('v1.2', False),
+            ('v1.2-3', True),
+            ('v1.2-r3', True),
+            ('v1.2+3', True),
+            ('v1.2~3', True),
+            ('v1.2+a3f5cb2', True),
+            ('v1.2-9287543', True),
+            ('v1.13.9-gke.3', True)
+        )
+
+        for version, expected in test_cases:
+            actual = CveUtils.is_downstream_version(version)
+            assert actual == expected
+
+    def test_ignore_downstream():
+        test_cases = (
+            ('v2.2-abcd', ['v1.1', 'v2.3'], False),
+            ('v2.2-abcd', ['v1.1', 'v2.2'], False),
+            ('v1.13.9-gke.3', ['v1.14.8'], False)
+        )
+
+        for check_version, fix_versions, expected in test_cases:
+            actual = CveUtils.is_vulnerable(check_version, fix_versions, True)
+            assert actual == expected