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rbac.go
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rbac.go
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package rbac
import (
"context"
"fmt"
"time"
"github.com/casbin/casbin"
"github.com/casbin/casbin/model"
jwt "github.com/dgrijalva/jwt-go"
"github.com/gobuffalo/packr"
scas "github.com/qiangmzsx/string-adapter"
log "github.com/sirupsen/logrus"
apiv1 "k8s.io/api/core/v1"
apierr "k8s.io/apimachinery/pkg/api/errors"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/fields"
v1 "k8s.io/client-go/informers/core/v1"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/cache"
)
const (
ConfigMapPolicyCSVKey = "policy.csv"
ConfigMapPolicyDefaultKey = "policy.default"
builtinModelFile = "model.conf"
defaultRBACSyncPeriod = 10 * time.Minute
)
// Enforcer is a wrapper around an Casbin enforcer that:
// * is backed by a kubernetes config map
// * has a predefined RBAC model
// * supports a built-in policy
// * supports a user-defined bolicy
// * supports a custom JWT claims enforce function
type Enforcer struct {
*casbin.Enforcer
adapter *scas.Adapter
clientset kubernetes.Interface
namespace string
configmap string
claimsEnforcerFunc ClaimsEnforcerFunc
model model.Model
defaultRole string
builtinPolicy string
userDefinedPolicy string
}
// ClaimsEnforcerFunc is func template to enforce a JWT claims. The subject is replaced
type ClaimsEnforcerFunc func(claims jwt.Claims, rvals ...interface{}) bool
var (
modelConf string
)
func init() {
box := packr.NewBox(".")
modelConf = box.String(builtinModelFile)
}
func NewEnforcer(clientset kubernetes.Interface, namespace, configmap string, claimsEnforcer ClaimsEnforcerFunc) *Enforcer {
adapter := scas.NewAdapter("")
builtInModel := newBuiltInModel()
enf := casbin.NewEnforcer(builtInModel, adapter)
enf.EnableLog(false)
return &Enforcer{
Enforcer: enf,
adapter: adapter,
clientset: clientset,
namespace: namespace,
configmap: configmap,
model: builtInModel,
claimsEnforcerFunc: claimsEnforcer,
}
}
// SetDefaultRole sets a default role to use during enforcement. Will fall back to this role if
// normal enforcement fails
func (e *Enforcer) SetDefaultRole(roleName string) {
e.defaultRole = roleName
}
// SetClaimsEnforcerFunc sets a claims enforce function during enforcement. The claims enforce function
// can extract claims from JWT token and do the proper enforcement based on user, group or any information
// available in the input parameter list
func (e *Enforcer) SetClaimsEnforcerFunc(claimsEnforcer ClaimsEnforcerFunc) {
e.claimsEnforcerFunc = claimsEnforcer
}
// Enforce is a wrapper around casbin.Enforce to additionally enforce a default role and a custom
// claims function
func (e *Enforcer) Enforce(rvals ...interface{}) bool {
return enforce(e.Enforcer, e.defaultRole, e.claimsEnforcerFunc, rvals...)
}
// EnforceRuntimePolicy enforces a policy defined at run-time which augments the built-in and
// user-defined policy. This allows any explicit denies of the built-in, and user-defined policies
// to override the run-time policy. Runs normal enforcement if run-time policy is empty.
func (e *Enforcer) EnforceRuntimePolicy(policy string, rvals ...interface{}) bool {
var enf *casbin.Enforcer
var err error
if policy == "" {
enf = e.Enforcer
} else {
policies := fmt.Sprintf("%s\n%s\n%s", e.builtinPolicy, e.userDefinedPolicy, policy)
adapter := scas.NewAdapter(policies)
enf, err = casbin.NewEnforcerSafe(newBuiltInModel(), adapter)
if err != nil {
log.Warnf("invalid runtime policy: %s", policy)
enf = e.Enforcer
}
}
return enforce(enf, e.defaultRole, e.claimsEnforcerFunc, rvals...)
}
// enforce is a helper to additionally check a default role and invoke a custom claims enforcement function
func enforce(enf *casbin.Enforcer, defaultRole string, claimsEnforcerFunc ClaimsEnforcerFunc, rvals ...interface{}) bool {
// check the default role
if defaultRole != "" && len(rvals) >= 2 {
if enf.Enforce(append([]interface{}{defaultRole}, rvals[1:]...)...) {
return true
}
}
// check if subject is jwt.Claims vs. a normal subject string and run custom claims
// enforcement func (if set)
sub := rvals[0]
switch sub.(type) {
case string:
// noop
case jwt.Claims:
if claimsEnforcerFunc != nil && claimsEnforcerFunc(sub.(jwt.Claims), rvals...) {
return true
}
rvals = append([]interface{}{""}, rvals[1:]...)
default:
rvals = append([]interface{}{""}, rvals[1:]...)
}
return enf.Enforce(rvals...)
}
// SetBuiltinPolicy sets a built-in policy, which augments any user defined policies
func (e *Enforcer) SetBuiltinPolicy(policy string) error {
e.builtinPolicy = policy
e.adapter.Line = fmt.Sprintf("%s\n%s", e.builtinPolicy, e.userDefinedPolicy)
return e.LoadPolicy()
}
// SetUserPolicy sets a user policy, augmenting the built-in policy
func (e *Enforcer) SetUserPolicy(policy string) error {
e.userDefinedPolicy = policy
e.adapter.Line = fmt.Sprintf("%s\n%s", e.builtinPolicy, e.userDefinedPolicy)
return e.LoadPolicy()
}
// newInformers returns an informer which watches updates on the rbac configmap
func (e *Enforcer) newInformer() cache.SharedIndexInformer {
tweakConfigMap := func(options *metav1.ListOptions) {
cmFieldSelector := fields.ParseSelectorOrDie(fmt.Sprintf("metadata.name=%s", e.configmap))
options.FieldSelector = cmFieldSelector.String()
}
return v1.NewFilteredConfigMapInformer(e.clientset, e.namespace, defaultRBACSyncPeriod, cache.Indexers{}, tweakConfigMap)
}
// RunPolicyLoader runs the policy loader which watches policy updates from the configmap and reloads them
func (e *Enforcer) RunPolicyLoader(ctx context.Context) error {
cm, err := e.clientset.CoreV1().ConfigMaps(e.namespace).Get(e.configmap, metav1.GetOptions{})
if err != nil {
if !apierr.IsNotFound(err) {
return err
}
} else {
err = e.syncUpdate(cm)
if err != nil {
return err
}
}
e.runInformer(ctx)
return nil
}
func (e *Enforcer) runInformer(ctx context.Context) {
cmInformer := e.newInformer()
cmInformer.AddEventHandler(
cache.ResourceEventHandlerFuncs{
AddFunc: func(obj interface{}) {
if cm, ok := obj.(*apiv1.ConfigMap); ok {
err := e.syncUpdate(cm)
if err != nil {
log.Error(err)
} else {
log.Infof("RBAC ConfigMap '%s' added", e.configmap)
}
}
},
UpdateFunc: func(old, new interface{}) {
oldCM := old.(*apiv1.ConfigMap)
newCM := new.(*apiv1.ConfigMap)
if oldCM.ResourceVersion == newCM.ResourceVersion {
return
}
err := e.syncUpdate(newCM)
if err != nil {
log.Error(err)
} else {
log.Infof("RBAC ConfigMap '%s' updated", e.configmap)
}
},
},
)
log.Info("Starting rbac config informer")
cmInformer.Run(ctx.Done())
log.Info("rbac configmap informer cancelled")
}
// syncUpdate updates the enforcer
func (e *Enforcer) syncUpdate(cm *apiv1.ConfigMap) error {
e.SetDefaultRole(cm.Data[ConfigMapPolicyDefaultKey])
policyCSV, ok := cm.Data[ConfigMapPolicyCSVKey]
if !ok {
policyCSV = ""
}
return e.SetUserPolicy(policyCSV)
}
// ValidatePolicy verifies a policy string is acceptable to casbin
func ValidatePolicy(policy string) error {
adapter := scas.NewAdapter(policy)
_, err := casbin.NewEnforcerSafe(newBuiltInModel(), adapter)
if err != nil {
return fmt.Errorf("policy syntax error: %s", policy)
}
return nil
}
// newBuiltInModel is a helper to return a brand new casbin model from the built-in model string.
// This is needed because it is not safe to re-use the same casbin Model when instantiating new
// casbin enforcers.
func newBuiltInModel() model.Model {
return casbin.NewModel(modelConf)
}