From 10b16ce9e9643fe973f6fa1208d62ba255198ab3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Petazzoni?= <jerome.petazzoni@gmail.com>
Date: Thu, 4 Nov 2021 21:40:08 +0100
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Fix=20issues=20in=20Kyverno=20po?=
 =?UTF-8?q?licies?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 k8s/kyverno-pod-color-2.yaml |  8 +++---
 k8s/kyverno-pod-color-3.yaml | 19 ++++++++------
 slides/k8s/kyverno.md        | 48 +++++++++++++++++++++++-------------
 3 files changed, 46 insertions(+), 29 deletions(-)

diff --git a/k8s/kyverno-pod-color-2.yaml b/k8s/kyverno-pod-color-2.yaml
index ae98f43f..484abfb3 100644
--- a/k8s/kyverno-pod-color-2.yaml
+++ b/k8s/kyverno-pod-color-2.yaml
@@ -16,11 +16,11 @@ spec:
       operator: Equals
       value: UPDATE
     - key: "{{ request.oldObject.metadata.labels.color }}"
-      operator: Equals
-      value: "*"
+      operator: NotEquals
+      value: ""
     - key: "{{ request.object.metadata.labels.color }}"
-      operator: Equals
-      value: "*"
+      operator: NotEquals
+      value: ""
     validate:
       message: "Once label color has been added, it cannot be changed."
       deny:
diff --git a/k8s/kyverno-pod-color-3.yaml b/k8s/kyverno-pod-color-3.yaml
index 1a15e8be..2f7e9794 100644
--- a/k8s/kyverno-pod-color-3.yaml
+++ b/k8s/kyverno-pod-color-3.yaml
@@ -6,20 +6,23 @@ spec:
   validationFailureAction: enforce
   background: false
   rules:
-  - name: prevent-color-removal
+  - name: prevent-color-change
     match:
       resources:
         kinds:
         - Pod
-        selector:
-          matchExpressions:
-          - key: color
-            operator: DoesNotExist
+    preconditions:
+    - key: "{{ request.operation }}"
+      operator: Equals
+      value: UPDATE
+    - key: "{{ request.oldObject.metadata.labels.color }}"
+      operator: NotEquals
+      value: ""
+    - key: "{{ request.object.metadata.labels.color }}"
+      operator: Equals
+      value: ""
     validate:
       message: "Once label color has been added, it cannot be removed."
       deny:
         conditions:
-        - key: "{{ request.oldObject.metadata.labels.color }}"
-          operator: NotIn
-          value: []
 
diff --git a/slides/k8s/kyverno.md b/slides/k8s/kyverno.md
index 14c23f4a..b0ed828f 100644
--- a/slides/k8s/kyverno.md
+++ b/slides/k8s/kyverno.md
@@ -100,11 +100,11 @@
 
   - Policy and ClusterPolicy (per-namespace and cluster-scope policies)
 
-  - PolicyViolation and ClusterPolicyViolation (used in audit mode)
+  - PolicyReport and ClusterPolicyReport (used in audit mode)
 
   - GenerateRequest (used internally when generating resources asynchronously)
 
-- We will be able to do e.g. `kubectl get policyviolations --all-namespaces`
+- We will be able to do e.g. `kubectl get clusterpolicyreports --all-namespaces`
 
   (to see policy violations across all namespaces)
 
@@ -266,16 +266,34 @@
 
   - *match* all pods
 
+  - add a *precondition* matching pods that have a `color` label
+    <br/>
+    (both in their "before" and "after" states)
+
   - *deny* these pods if their `color` label has changed
 
+- Again, other approaches are possible!
+
+---
+
+## Invalid references
+
+- We can access the `color` label through `{{ request.object.metadata.labels.color }}`
+
+- If we reference a label (or any field) that doesn't exist, the policy fails
+
+- Except in *preconditions*: it then evaluates to an empty string
+
+- We use a *precondition* to makes sure the label exists in both "old" and "new" objects
+
+- Then in the *deny* block we can compare the old and new values
+
+  (and reject changes)
+
 - "Old" and "new" versions of the pod can be referenced through
 
   `{{ request.oldObject }}` and `{{ request.object }}`
 
-- Our label is available through `{{ request.object.metadata.labels.color }}`
-
-- Again, other approaches are possible!
-
 ---
 
 ## Our second Kyverno policy
@@ -351,9 +369,7 @@
 
   (the `AdmissionRequest` object is the thing that gets submitted to the webhook)
 
-- Kyverno lets us access the `AdmissionRequest` object
-
-  (and in particular, `{{ request.object }}` and `{{ request.oldObject }}`)
+- We access the `AdmissionRequest` object through `{{ request }}`
 
 --
 
@@ -373,19 +389,17 @@
 
 ---
 
-<!--
-
 ## Immutable primary colors, take 3
 
 - New rule: once a `color` label has been added, it cannot be removed
 
-- Our approach:
+- Our approach is to match all pods that:
 
-  - *match* all pods that *do not* have a `color` label
+  - *had* a `color` label (in `request.oldObject`)
 
-  - *deny* these pods if they had a `color` label before
+  - *don't have* a `color` label (in `request.Object`)
 
-  - "before" can be referenced through `{{ request.oldObject }}`
+- And *deny* these pods
 
 - Again, other approaches are possible!
 
@@ -426,8 +440,6 @@
 
 ---
 
--->
-
 ## Background checks
 
 - What about the `test-color-0` pod that we create initially?
@@ -451,6 +463,8 @@
 
 ]
 
+(Sometimes it takes a little while for the infringement to show up, though.)
+
 ---
 
 ## Generating objects