feat(config): deny resources by using RESTMapper as an interceptor #149
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,40 @@ | ||
| package kubernetes | ||
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| import ( | ||
| "fmt" | ||
|
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| "k8s.io/apimachinery/pkg/runtime/schema" | ||
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| "github.com/manusa/kubernetes-mcp-server/pkg/config" | ||
| ) | ||
|
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| // isAllowed checks the resource is in denied list or not. | ||
| // If it is in denied list, this function returns false. | ||
| func isAllowed( | ||
| staticConfig *config.StaticConfig, // TODO: maybe just use the denied resource slice | ||
| gvk *schema.GroupVersionKind, | ||
| ) bool { | ||
| if staticConfig == nil { | ||
| return true | ||
| } | ||
|
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| for _, val := range staticConfig.DeniedResources { | ||
| // If kind is empty, that means Group/Version pair is denied entirely | ||
| if val.Kind == "" { | ||
| if gvk.Group == val.Group && gvk.Version == val.Version { | ||
| return false | ||
| } | ||
| } | ||
| if gvk.Group == val.Group && | ||
| gvk.Version == val.Version && | ||
| gvk.Kind == val.Kind { | ||
| return false | ||
| } | ||
| } | ||
|
|
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| return true | ||
| } | ||
|
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| func isNotAllowedError(gvk *schema.GroupVersionKind) error { | ||
| return fmt.Errorf("resource not allowed: %s", gvk.String()) | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,74 @@ | ||
| package kubernetes | ||
|
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| import ( | ||
| authorizationv1api "k8s.io/api/authorization/v1" | ||
| "k8s.io/apimachinery/pkg/runtime/schema" | ||
| "k8s.io/client-go/discovery" | ||
| "k8s.io/client-go/kubernetes" | ||
| authorizationv1 "k8s.io/client-go/kubernetes/typed/authorization/v1" | ||
| corev1 "k8s.io/client-go/kubernetes/typed/core/v1" | ||
| "k8s.io/client-go/rest" | ||
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| "github.com/manusa/kubernetes-mcp-server/pkg/config" | ||
| ) | ||
|
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| // AccessControlClientset is a limited clientset delegating interface to the standard kubernetes.Clientset | ||
| // Only a limited set of functions are implemented with a single point of access to the kubernetes API where | ||
| // apiVersion and kinds are checked for allowed access | ||
| type AccessControlClientset struct { | ||
| delegate kubernetes.Interface | ||
| discoveryClient discovery.DiscoveryInterface | ||
| staticConfig *config.StaticConfig // TODO: maybe just store the denied resource slice | ||
| } | ||
|
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| func (a *AccessControlClientset) DiscoveryClient() discovery.DiscoveryInterface { | ||
| return a.discoveryClient | ||
| } | ||
|
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| func (a *AccessControlClientset) Pods(namespace string) (corev1.PodInterface, error) { | ||
| gvk := &schema.GroupVersionKind{Group: "", Version: "v1", Kind: "Pod"} | ||
| if !isAllowed(a.staticConfig, gvk) { | ||
| return nil, isNotAllowedError(gvk) | ||
| } | ||
| return a.delegate.CoreV1().Pods(namespace), nil | ||
| } | ||
|
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| func (a *AccessControlClientset) PodsExec(namespace, name string) (*rest.Request, error) { | ||
|
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| gvk := &schema.GroupVersionKind{Group: "", Version: "v1", Kind: "Pod"} | ||
| if !isAllowed(a.staticConfig, gvk) { | ||
| return nil, isNotAllowedError(gvk) | ||
| } | ||
| // https://github.com/kubernetes/kubectl/blob/5366de04e168bcbc11f5e340d131a9ca8b7d0df4/pkg/cmd/exec/exec.go#L382-L397 | ||
| return a.delegate.CoreV1().RESTClient(). | ||
| Post(). | ||
| Resource("pods"). | ||
| Namespace(namespace). | ||
| Name(name). | ||
| SubResource("exec"), nil | ||
| } | ||
|
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| func (a *AccessControlClientset) Services(namespace string) (corev1.ServiceInterface, error) { | ||
| gvk := &schema.GroupVersionKind{Group: "", Version: "v1", Kind: "Service"} | ||
| if !isAllowed(a.staticConfig, gvk) { | ||
| return nil, isNotAllowedError(gvk) | ||
| } | ||
| return a.delegate.CoreV1().Services(namespace), nil | ||
| } | ||
|
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| func (a *AccessControlClientset) SelfSubjectAccessReviews() (authorizationv1.SelfSubjectAccessReviewInterface, error) { | ||
| gvk := &schema.GroupVersionKind{Group: authorizationv1api.GroupName, Version: authorizationv1api.SchemeGroupVersion.Version, Kind: "SelfSubjectAccessReview"} | ||
| if !isAllowed(a.staticConfig, gvk) { | ||
| return nil, isNotAllowedError(gvk) | ||
| } | ||
| return a.delegate.AuthorizationV1().SelfSubjectAccessReviews(), nil | ||
| } | ||
|
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| func NewAccessControlClientset(cfg *rest.Config, staticConfig *config.StaticConfig) (*AccessControlClientset, error) { | ||
| clientSet, err := kubernetes.NewForConfig(cfg) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return &AccessControlClientset{ | ||
| delegate: clientSet, discoveryClient: clientSet.DiscoveryClient, staticConfig: staticConfig, | ||
| }, nil | ||
| } | ||
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(not a blocker for this PR):
We have to return 403: Forbidden HTTP Status. But I'm not really sure that mcp library we use support this. If it doesn't support returning http code we have, we'll have major issue in oauth side as well.
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It just simply sets http 200 statically https://github.com/mark3labs/mcp-go/blob/1eddde7bd69b760f745a1b4064969cffcf97e935/server/streamable_http.go#L347 :(
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Yes, I don't think the library (or even the protocol) is prepared for fine-grained operation status codes yet.
As I understand it, the protocol negotiates authentication and authorization first, and then enables