Add tetra policyfilter listpolicies command

It is useful to have a debug command to indentify which Kubernetes
Identity Aware policies should be applied on a specific container. An
example can be found here:

Create a pod with "app: ubuntu" and "usage: dev" labels.

$ cat << EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: ubuntu
  labels:
    app: ubuntu
    usage: dev
spec:
  containers:
  - name: ubuntu
    image: ubuntu:24.10
    command: ["/bin/sleep", "3650d"]
    imagePullPolicy: IfNotPresent
  restartPolicy: Always
EOF

And apply several policies where some of them match while others don't.

$ cat << EOF | kubectl apply -f -
apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: "lseek-podfilter-app"
spec:
  podSelector:
    matchLabels:
      app: "ubuntu"
  kprobes:
    [...]
EOF
$ cat << EOF | kubectl apply -f -
apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: "lseek-podfilter-usage"
spec:
  podSelector:
    matchLabels:
      usage: "dev"
  kprobes:
    [...]
EOF
$ cat << EOF | kubectl apply -f -
apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: "lseek-podfilter-prod"
spec:
  podSelector:
    matchLabels:
      prod: "true"
  kprobes:
    [...]
EOF
$ cat << EOF | kubectl apply -f -
apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: "lseek-podfilter-info"
spec:
  podSelector:
    matchLabels:
      info: "broken"
  kprobes:
    [...]
EOF
$ cat << EOF | kubectl apply -f -
apiVersion: cilium.io/v1alpha1
kind: TracingPolicy
metadata:
  name: "lseek-podfilter-global"
spec:
  kprobes:
    [...]
EOF

Based on the labels we expect that policies lseek-podfilter-app and
lseek-podfilter-usage to match on that pod. lseek-podfilter-global is
not a Kubernetes Identity Aware policy so this will be applied in all
cases and we do not report that.

First step is to find the container ID that we care about.

$ kubectl describe pod/ubuntu | grep containerd
    Container ID:  containerd://ff433e9e16467787a60ac853d9b313150091968731f620776d6d7c514b1e8d6c

And then use it to report all Kubernetes Identity Aware policies that
match.

$ kubectl exec -it ds/tetragon -n kube-system -c tetragon -- tetra policyfilter -r "unix:///procRoot/1/root/run/containerd/containerd.sock" listpolicies ff433e9e16467787a60ac853d9b313150091968731f620776d6d7c514b1e8d6c
ID   NAME                    STATE     FILTERID   NAMESPACE   SENSORS          KERNELMEMORY
5    lseek-podfilter-usage   enabled   5          (global)    generic_kprobe   1.72 MB
1    lseek-podfilter-app     enabled   1          (global)    generic_kprobe   1.72 MB

We also provide --debug flag to provide more details i.e.:

$ kubectl exec -it ds/tetragon -n kube-system -c tetragon -- tetra policyfilter -r "unix:///procRoot/1/root/run/containerd/containerd.sock" listpolicies ff433e9e16467787a60ac853d9b313150091968731f620776d6d7c514b1e8d6c --debug
time="2024-12-13T09:47:38Z" level=info msg=cgroup path=/run/tetragon/cgroup2/kubepods.slice/kubepods-besteffort.slice/kubepods-besteffort-pod189a8053_9f36_4250_bcae_9ed167172920.slice/cri-containerd-ff433e9e16467787a60ac853d9b313150091968731f620776d6d7c514b1e8d6c.scope
time="2024-12-13T09:47:38Z" level=info msg=cgroup id=5695
time="2024-12-13T09:47:39Z" level=debug msg="resolved server address using info file" InitInfoFile=/var/run/tetragon/tetragon-info.json ServerAddress="localhost:54321"
ID   NAME                    STATE     FILTERID   NAMESPACE   SENSORS          KERNELMEMORY
1    lseek-podfilter-app     enabled   1          (global)    generic_kprobe   1.72 MB
5    lseek-podfilter-usage   enabled   5          (global)    generic_kprobe   1.72 MB

This uses a reverse policy filter map that introduced in a previous
commit and maps cgroupIds to policyIds.

Signed-off-by: Anastasios Papagiannis <anastasios.papagiannis@isovalent.com>

Author: tpapagian

cmd/tetra/policyfilter/policyfilter.go

@@ -4,12 +4,20 @@
 package policyfilter
 
 import (
+	"context"
 	"fmt"
+	"os"
+	"path"
 	"path/filepath"
 	"strconv"
+	"strings"
+	"text/tabwriter"
 
+	"github.com/cilium/tetragon/api/v1/tetragon"
+	"github.com/cilium/tetragon/cmd/tetra/common"
 	"github.com/cilium/tetragon/cmd/tetra/debug"
 	"github.com/cilium/tetragon/pkg/cgroups"
+	"github.com/cilium/tetragon/pkg/cri"
 	"github.com/cilium/tetragon/pkg/defaults"
 	"github.com/cilium/tetragon/pkg/logger"
 	"github.com/cilium/tetragon/pkg/policyfilter"
@@ -29,6 +37,7 @@ func New() *cobra.Command {
 		addCommand(),
 		cgroupGetIDCommand(),
 		dumpDebugCmd(),
+		listPoliciesForContainer(),
 	)
 
 	return ret
@@ -138,3 +147,131 @@ func addCgroup(fname string, polID policyfilter.PolicyID, cgID policyfilter.Cgro
 	}
 
 }
+
+func listPoliciesForContainer() *cobra.Command {
+	var endpoint, cgroupMnt string
+	mapFname := filepath.Join(defaults.DefaultMapRoot, defaults.DefaultMapPrefix, policyfilter.MapName)
+	ret := &cobra.Command{
+		Use:   "listpolicies [container id]",
+		Short: "list all Kubernetes Identity Aware policies that apply to a specific container",
+		Args:  cobra.ExactArgs(1),
+		RunE: func(_ *cobra.Command, args []string) error {
+			ctx := context.Background()
+			client, err := cri.NewClient(ctx, endpoint)
+			if err != nil {
+				return err
+			}
+
+			cgroupPath, err := cri.CgroupPath(ctx, client, args[0])
+			if err != nil {
+				return err
+			}
+
+			if cgroupMnt == "" {
+				cgroupMnt = defaults.Cgroup2Dir
+			}
+			fullCgroupPath := path.Join(cgroupMnt, cgroupPath)
+			if common.Debug {
+				logger.GetLogger().WithField("path", fullCgroupPath).Info("cgroup")
+			}
+
+			cgID, err := cgroups.GetCgroupIdFromPath(fullCgroupPath)
+			if err != nil {
+				logger.GetLogger().WithError(err).Fatal("Failed to parse cgroup")
+			}
+
+			if common.Debug {
+				logger.GetLogger().WithField("id", cgID).Info("cgroup")
+			}
+
+			m, err := policyfilter.OpenMap(mapFname)
+			if err != nil {
+				logger.GetLogger().WithError(err).Fatal("Failed to open policyfilter map")
+				return err
+			}
+			defer m.Close()
+
+			data, err := m.Dump()
+			if err != nil {
+				logger.GetLogger().WithError(err).Fatal("Failed to open policyfilter map")
+				return err
+			}
+
+			policyIds, ok := data.Reverse[policyfilter.CgroupID(cgID)]
+			if !ok {
+				return nil
+			}
+
+			c, err := common.NewClientWithDefaultContextAndAddress()
+			if err != nil {
+				return fmt.Errorf("failed create gRPC client: %w", err)
+			}
+			defer c.Close()
+
+			res, err := c.Client.ListTracingPolicies(c.Ctx, &tetragon.ListTracingPoliciesRequest{})
+			if err != nil || res == nil {
+				return fmt.Errorf("failed to list tracing policies: %w", err)
+			}
+
+			// tabwriter config imitates kubectl default output, i.e. 3 spaces padding
+			w := tabwriter.NewWriter(os.Stdout, 0, 0, 3, ' ', 0)
+			fmt.Fprintln(w, "ID\tNAME\tSTATE\tFILTERID\tNAMESPACE\tSENSORS\tKERNELMEMORY")
+
+			for _, pol := range res.Policies {
+				namespace := pol.Namespace
+				if namespace == "" {
+					namespace = "(global)"
+				}
+
+				sensors := strings.Join(pol.Sensors, ",")
+
+				// From v0.11 and before, enabled, filterID and error were
+				// bundled in a string. To have a retro-compatible tetra
+				// command, we scan the string. If the scan fails, it means
+				// something else might be in Info and we print it.
+				//
+				// we can drop the following block (and comment) when we
+				// feel tetra should support only version after v0.11
+				if pol.Info != "" {
+					var parsedEnabled bool
+					var parsedFilterID uint64
+					var parsedError string
+					var parsedName string
+					str := strings.NewReader(pol.Info)
+					_, err := fmt.Fscanf(str, "%253s enabled:%t filterID:%d error:%512s", &parsedName, &parsedEnabled, &parsedFilterID, &parsedError)
+					if err == nil {
+						if parsedEnabled {
+							pol.State = tetragon.TracingPolicyState_TP_STATE_ENABLED
+						}
+						pol.FilterId = parsedFilterID
+						pol.Error = parsedError
+						pol.Info = ""
+					}
+				}
+
+				if _, ok := policyIds[policyfilter.PolicyID(pol.FilterId)]; !ok {
+					continue
+				}
+
+				fmt.Fprintf(w, "%d\t%s\t%s\t%d\t%s\t%s\t%s\t\n",
+					pol.Id,
+					pol.Name,
+					strings.TrimPrefix(strings.ToLower(pol.State.String()), "tp_state_"),
+					pol.FilterId,
+					namespace,
+					sensors,
+					common.HumanizeByteCount(int(pol.KernelMemoryBytes)),
+				)
+			}
+			w.Flush()
+
+			return nil
+		},
+	}
+
+	flags := ret.Flags()
+	flags.StringVarP(&endpoint, "runtime-endpoint", "r", "", "CRI endpoint")
+	flags.StringVar(&mapFname, "map-fname", mapFname, "policyfilter map filename")
+	flags.StringVar(&cgroupMnt, "cgroup-mount", cgroupMnt, "cgroupFS mount point")
+	return ret
+}