feat: allow filters for container context

Previously it wasn't possible to filter based on container specific details since only the entire pod is available within the context. A new filter context attribute "Container" holds the currently processes container and allows more fine-grained control. fixes #32
estahn · Dec 22, 2020 · c7e4c51 · c7e4c51
1 parent 1e1c186
commit c7e4c51
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Showing 3 changed files with 30 additions and 4 deletions.
diff --git a/docs/configuration.md b/docs/configuration.md
@@ -42,6 +42,8 @@ If a condition matches, the pod will **NOT** be processed.
         ```yaml
         obj:
           <Object Spec>
+        container:
+          <Container Spec>
         ```
 
     === "Example"
@@ -59,11 +61,18 @@ If a condition matches, the pod will **NOT** be processed.
                   - name: web
                     containerPort: 80
                     protocol: TCP
+        container:
+          name: web
+          image: nginx
+          ports:
+            - name: web
+              containerPort: 80
+              protocol: TCP
         ```
 
 Below you will find a list of common queries and/or ideas:
 
-??? tip "List of common queries/ideas"
+!!! tip "List of common queries/ideas"
     * Do not process if namespace equals `kube-system` (_Helm chart default_)
       ```yaml
       source:
@@ -82,6 +91,13 @@ Below you will find a list of common queries and/or ideas:
         filters:
           - jmespath: "ends_with(obj.metadata.namespace,'-dev')"
       ```
+    * Do not process AWS ECR images
+    ```yaml
+    source:
+    filters:
+    - jmespath: "contains(container.image, `.dkr.ecr.`) && contains(container.image, `.amazonaws.com`)"
+    ```
+
 
 `k8s-image-swapper` will log the filter data and result in `debug` mode.
 This can be used in conjunction with [JMESPath.org](https://jmespath.org/) which

diff --git a/pkg/webhook/image_swapper.go b/pkg/webhook/image_swapper.go
@@ -99,7 +99,7 @@ func (p *ImageSwapper) Mutate(ctx context.Context, obj metav1.Object) (bool, err
 			continue
 		}
 
-		filterCtx := NewFilterContext(*ar, pod)
+		filterCtx := NewFilterContext(*ar, pod, pod.Spec.Containers[i])
 		if filterMatch(filterCtx, p.filters) {
 			log.Ctx(lctx).Info().Msg("skip due to filter condition")
 			continue
@@ -175,15 +175,19 @@ func (p *ImageSwapper) targetName(ref types.ImageReference) string {
 
 // FilterContext is being used by JMESPath to search and match
 type FilterContext struct {
+	// Obj contains the object submitted to the webhook (currently only pods)
 	Obj metav1.Object `json:"obj,omitempty"`
+
+	// Container contains the currently processed container
+	Container corev1.Container `json:"container,omitempty"`
 }
 
-func NewFilterContext(request v1beta1.AdmissionRequest, obj metav1.Object) FilterContext {
+func NewFilterContext(request v1beta1.AdmissionRequest, obj metav1.Object, container corev1.Container) FilterContext {
 	if obj.GetNamespace() == "" {
 		obj.SetNamespace(request.Namespace)
 	}
 
-	return FilterContext{Obj: obj}
+	return FilterContext{Obj: obj, Container: container}
 }
 
 func copyImage(src string, srcCeds string, dest string, destCreds string) error {

diff --git a/pkg/webhook/image_swapper_test.go b/pkg/webhook/image_swapper_test.go
@@ -154,14 +154,20 @@ func TestFilterMatch(t *testing.T) {
 			Spec: corev1.PodSpec{
 				Containers: []corev1.Container{
 					{
+						Name: "nginx",
 						Image: "nginx:latest",
 					},
 				},
 			},
 		},
+		Container: corev1.Container{
+			Name: "nginx",
+			Image: "nginx:latest",
+		},
 	}
 
 	assert.True(t, filterMatch(filterContext, []pkg.JMESPathFilter{{JMESPath: "obj.metadata.namespace == 'kube-system'"}}))
 	assert.False(t, filterMatch(filterContext, []pkg.JMESPathFilter{{JMESPath: "obj.metadata.namespace != 'kube-system'"}}))
 	assert.False(t, filterMatch(filterContext, []pkg.JMESPathFilter{{JMESPath: "obj"}}))
+	assert.True(t, filterMatch(filterContext, []pkg.JMESPathFilter{{JMESPath: "container.name == 'nginx'"}}))
 }