existing.go

/*
Copyright (C) 2018 Expedia Group.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

// Package existing handles the checking of Graffiti rules against already existing objects within Kubernetes.
package existing

import (
	"encoding/json"
	"fmt"
	"strings"

	"github.com/HotelsDotCom/kube-graffiti/pkg/config"
	"github.com/HotelsDotCom/kube-graffiti/pkg/graffiti"
	"github.com/HotelsDotCom/kube-graffiti/pkg/log"
	"github.com/HotelsDotCom/kube-graffiti/pkg/webhook"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/client-go/discovery"
	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/rest"
)

const (
	componentName = "existing"
	// itemLimit is used to constrain the number of items returned in a kubernetes List call.
	itemLimit = 100
)

var (
	// package level discovery client to share when looking up available kubernetes objects/versions/resources
	discoveryClient     apiDiscoverer
	discoveredAPIGroups = make(map[string]metav1.APIGroup)
	discoveredResources = make(map[string][]metav1.APIResource)
	dynamicClient       dynamic.Interface
	nsCache             namespaceCache
)

// interface used to mock out the client-go discovery client for testing...
type apiDiscoverer interface {
	ServerGroups() (apiGroupList *metav1.APIGroupList, err error)
	ServerResources() ([]*metav1.APIResourceList, error)
}

// InitKubeClients sets up the package for working with kubernetes api and discovers
// and caches known api groups/versions and resource types
func InitKubeClients(rest *rest.Config) error {
	mylog := log.ComponentLogger(componentName, "InitKubeClients")
	mylog.Debug().Msg("setting up kubernetes discovery and dynamic clients")
	var err error

	discoveryClient, err = discovery.NewDiscoveryClientForConfig(rest)
	if err != nil {
		return fmt.Errorf("can't get a kubernetes discovery client: %v", err)
	}
	dynamicClient, err = dynamic.NewForConfig(rest)
	if err != nil {
		return fmt.Errorf("can't get a kubernetes dynamic client: %v", err)
	}
	nsCache, err = NewNamespaceCache(rest)
	if err != nil {
		return fmt.Errorf("could not create the namespace cache: %v", err)
	}

	return discoverAPIsAndResources()
}

// discoverAPIsAndResources loads information about known apis and resources
// into our cache so we can use them without making lots of calls to kubernetes
func discoverAPIsAndResources() error {
	mylog := log.ComponentLogger(componentName, "discoverAPIsAndResources")

	mylog.Debug().Msg("discovering kubernetes api groups")
	sg, err := discoveryClient.ServerGroups()
	if err != nil {
		mylog.Error().Err(err).Msg("failed to look up kubernetes apigroups")
		return fmt.Errorf("failed to discover kubernetes api groups/versions: %v", err)
	}
	for _, group := range sg.Groups {
		discoveredAPIGroups[group.Name] = group
	}

	mylog.Debug().Msg("discovering kubernetes resources")
	sliceOfResourceLists, err := discoveryClient.ServerResources()
	if err != nil {
		mylog.Error().Err(err).Msg("failed to look up kubernetes resources")
	}
	for _, gv := range sliceOfResourceLists {
		discoveredResources[gv.GroupVersion] = gv.APIResources
	}

	return nil
}

// ApplyRulesAgainstExistingObjects interates over the graffiti rules and targets, apply each rule to existing kubernetes objects.
func ApplyRulesAgainstExistingObjects(rules []config.Rule) {
	mylog := log.ComponentLogger(componentName, "ApplyRulesAgainstExistingObjects")

	// start the namespace cache reflector to populate it with values
	stop := make(chan struct{})
	defer close(stop)
	nsCache.StartNamespaceReflector(stop)
	mylog.Info().Msg("checking existing objects against graffiti rules")
	for _, rule := range rules {
		ApplyRuleAgainstExistingObjects(rule)
	}
}

// ApplyRuleAgainstExistingObjects checks a single graffiti rule against existing kubernetes objects
func ApplyRuleAgainstExistingObjects(rule config.Rule) {
	mylog := log.ComponentLogger(componentName, "ApplyRuleAgainstExistingObjects")
	mylog.Debug().Str("rule", rule.Registration.Name).Msg("applying rule to existing objects")
	for _, target := range rule.Registration.Targets {
		applyToTargetttedAPIGroupsAndVersions(&rule, target)
	}
}

// applyToTargetttedAPIGroupsAndVersions starts evaluating a target by getting a list of APIGroups which are listed.
// If the target APIGroups is ["*"] then we will check through *all* discoverd apigroups.
func applyToTargetttedAPIGroupsAndVersions(rule *config.Rule, target webhook.Target) {
	mylog := log.ComponentLogger(componentName, "applyToTargetttedAPIGroupsAndVersions")
	rlog := mylog.With().Str("rule", rule.Registration.Name).Str("target-apigroups", strings.Join(target.APIGroups, ",")).Str("target-versions", strings.Join(target.APIVersions, ",")).Str("target-resources", strings.Join(target.Resources, ",")).Logger()
	rlog.Debug().Msg("evaluating target")

	// handle wildcard '*'
	var targetGroups []string
	if len(target.APIGroups) == 1 && target.APIGroups[0] == "*" {
		rlog.Debug().Msg("found target with APIGroup * wildcard")
		// check *all* discovered groups
		for _, g := range discoveredAPIGroups {
			targetGroups = append(targetGroups, g.Name)
		}
	} else {
		targetGroups = target.APIGroups
	}

	// check each group/version is targetted and check
	for _, g := range targetGroups {
		if isTargetted(discoveredAPIGroups[g].PreferredVersion.Version, target.APIVersions) {
			applyToAllResourcesInAGroupVersion(rule, target, discoveredAPIGroups[g].PreferredVersion)
		} else {
			rlog.Warn().Str("group", g).Str("preffered-version", discoveredAPIGroups[g].PreferredVersion.Version).Msg("targetted APIVersions do not match either wildcard or the preferred api version - therefore we will not use this rule to update existing objects for this group")
		}
	}
}

// isTargetted checks that an element is present in a target list or matches a wildcard '*'
func isTargetted(element string, targets []string) bool {
	for _, target := range targets {
		if target == "*" || element == target {
			return true
		}
	}
	return false
}

// applyToAllResourcesInAGroupVersion checks all the resources in an group/version that are targetted.
// If the target is ["*"] then all resources are checked, otherwise each discovered resource is
// checked against the target list.
func applyToAllResourcesInAGroupVersion(rule *config.Rule, target webhook.Target, gv metav1.GroupVersionForDiscovery) {
	mylog := log.ComponentLogger(componentName, "applyToAllResourcesInAGroupVersion")
	rlog := mylog.With().Str("rule", rule.Registration.Name).Str("group-version", gv.GroupVersion).Str("version", gv.Version).Logger()
	rlog.Debug().Msg("evaluating group version")

	if len(target.Resources) == 1 && (target.Resources[0] == "*" || target.Resources[0] == "*/*") {
		rlog.Debug().Msg("found target with Resources * wildcard")
		for _, r := range discoveredResources[gv.GroupVersion] {
			applyToAllResourcesOfType(rule, gv.GroupVersion, r)
		}
		return
	}

	// create a list of resources without any subtypes
	var resourceTargets []string
	for _, r := range target.Resources {
		rlog.Debug().Str("resource", r).Msg("adding resource for match")
		x, _ := splitSlashedResourceString(r)
		if x == "*" {
			rlog.Error().Msg("you shouldn't have a wildcard '*' in a list of resources, ignoring")
			continue
		}
		resourceTargets = append(resourceTargets, x)
	}

	// for each resource in the group/version check if it is targetted list and check
	for _, resource := range discoveredResources[gv.GroupVersion] {
		rlog.Debug().Str("resource", resource.Name).Msg("calling isTargetted on resource")
		if isTargetted(resource.Name, resourceTargets) {
			rlog.Debug().Str("resource", resource.Name).Msg("resorce is targetted")
			applyToAllResourcesOfType(rule, gv.GroupVersion, resource)
		} else {
			rlog.Debug().Str("resource", resource.Name).Msg("resource is not targetted")
		}
	}
}

func splitSlashedResourceString(s string) (first, second string) {
	parts := strings.SplitN(s, "/", 2)
	if len(parts) == 2 {
		return parts[0], parts[1]
	}
	return parts[0], ""
}

func splitGroupVersionString(s string) (group, version string) {
	parts := strings.SplitN(s, "/", 2)
	if len(parts) == 2 {
		return parts[0], parts[1]
	}
	return "", parts[0]
}

// applyToAllResourcesOfType checks all of the resources of particular group/version type.
// It lists the resources in batches of itemLimit in order to preserve memory when there are
// many kubernetes objects of the type in the cluster.
func applyToAllResourcesOfType(rule *config.Rule, gv string, resource metav1.APIResource) {
	mylog := log.ComponentLogger(componentName, "applyToAllResourcesOfType")
	rlog := mylog.With().Str("rule", rule.Registration.Name).Str("group-version", gv).Str("resource", resource.Name).Logger()
	rlog.Debug().Msg("looking at resources of type")

	g, v := splitGroupVersionString(gv)
	// get a dynamic client resource interface
	grv := schema.GroupVersionResource{
		Group:    g,
		Version:  v,
		Resource: resource.Name,
	}
	ri := dynamicClient.Resource(grv)

	// get first list of items up to our limit
	list, err := ri.List(metav1.ListOptions{Limit: itemLimit})
	if err != nil {
		rlog.Error().Err(err).Msg("failed to list resources")
		return
	}
	if list == nil {
		rlog.Debug().Msg("no resources found")
		return
	}
	rlog.Debug().Int("number-resources", len(list.Items)).Msg("processing batch of resources")
	for _, item := range list.Items {
		_ = applyToObject(rule, gv, resource.Name, item)
	}

	// if we only got a partial list we need to continue until we have seen them all
	meta := list.Object["metadata"].(map[string]interface{})
	for cont, ok := meta["continue"]; ok; {
		list, err = ri.List(metav1.ListOptions{Limit: itemLimit, Continue: cont.(string)})
		if err != nil {
			rlog.Error().Err(err).Msg("failed to list resources")
			return
		}
		if list == nil {
			rlog.Debug().Msg("no resources found")
			return
		}
		rlog.Debug().Int("number-resources", len(list.Items)).Msg("processing batch of resources")
		for _, item := range list.Items {
			applyToObject(rule, gv, resource.Name, item)
		}
		meta = list.Object["metadata"].(map[string]interface{})
		cont, ok = meta["continue"]
	}
}

// applyToObject takes a single kubernete object and decides whether to graffiti it or not.
func applyToObject(rule *config.Rule, gv, resource string, object unstructured.Unstructured) (patched bool) {
	mylog := log.ComponentLogger(componentName, "applyToObject")
	kind := object.GetKind()
	name := object.GetName()
	namespace := object.GetNamespace()
	rlog := mylog.With().Str("rule", rule.Registration.Name).Str("group-version", gv).Str("kind", kind).Str("name", name).Str("namespace", namespace).Logger()
	rlog.Debug().Msg("checking object")

	// match against optional rule namespace selector
	if rule.Registration.NamespaceSelector != "" {
		match, err := objectsNamespaceMatchesProvidedSelector(object.Object, rule.Registration.NamespaceSelector, nsCache)
		if err != nil {
			rlog.Error().Err(err).Msg("error checking object against namespace selector")
		}
		if !match {
			rlog.Debug().Msg("object does not match namespace selector")
			return false
		}
	}

	rlog.Info().Msg("applying graffiti mutate rule to existing object")
	gr := graffiti.Rule{
		Name:     rule.Registration.Name,
		Matchers: rule.Matchers,
		Payload:  rule.Payload,
	}
	raw, err := json.Marshal(object.Object)
	if err != nil {
		rlog.Error().Err(err).Msg("could not marshal object")
		return false
	}
	// call the graffiti package to evaluation the graffiti rule...
	patch, err := gr.Mutate(raw)
	if err != nil {
		rlog.Error().Err(err).Msg("could not mutate object")
		return false
	}
	if patch == nil {
		rlog.Info().Msg("mutate did not create a patch")
		return false
	}

	rlog.Debug().Str("patch", string(patch)).Msg("mutate produced a patch")
	g, v := splitGroupVersionString(gv)
	grv := schema.GroupVersionResource{
		Group:    g,
		Version:  v,
		Resource: resource,
	}
	ri := dynamicClient.Resource(grv)
	if namespace == "" {
		rlog.Debug().Msg("patching cluster level object")
		_, err = ri.Patch(name, types.JSONPatchType, patch, metav1.PatchOptions{FieldManager: "kube-graffiti"})
	} else {
		rlog.Debug().Msg("patching namespaced object")
		nri := ri.Namespace(namespace)
		_, err = nri.Patch(name, types.JSONPatchType, patch, metav1.PatchOptions{FieldManager: "kube-graffiti"})
	}
	if err != nil {
		rlog.Error().Err(err).Msg("failed to patch object")
		return false
	}
	rlog.Info().Str("patch", string(patch)).Msg("successfully patched object")
	return true
}