oci.WithPrivileged: set the current caps, not the known caps

This change is needed for running the latest containerd inside Docker
that is not aware of the recently added caps (BPF, PERFMON, CHECKPOINT_RESTORE).

Without this change, containerd inside Docker fails to run containers with
"apply caps: operation not permitted" error.

See kubernetes-sigs/kind 2058

NOTE: The caller process of this function is now assumed to be as
privileged as possible.

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

oci/spec_opts.go

@@ -38,7 +38,6 @@ import (
 	"github.com/opencontainers/runc/libcontainer/user"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/pkg/errors"
-	"github.com/syndtr/gocapability/capability"
 )
 
 // SpecOpts sets spec specific information to a newly generated OCI spec
@@ -776,29 +775,6 @@ func WithCapabilities(caps []string) SpecOpts {
 	}
 }
 
-// WithAllCapabilities sets all linux capabilities for the process
-var WithAllCapabilities = func(ctx context.Context, client Client, c *containers.Container, s *Spec) error {
-	return WithCapabilities(GetAllCapabilities())(ctx, client, c, s)
-}
-
-// GetAllCapabilities returns all caps up to CAP_LAST_CAP
-// or CAP_BLOCK_SUSPEND on RHEL6
-func GetAllCapabilities() []string {
-	last := capability.CAP_LAST_CAP
-	// hack for RHEL6 which has no /proc/sys/kernel/cap_last_cap
-	if last == capability.Cap(63) {
-		last = capability.CAP_BLOCK_SUSPEND
-	}
-	var caps []string
-	for _, cap := range capability.List() {
-		if cap > last {
-			continue
-		}
-		caps = append(caps, "CAP_"+strings.ToUpper(cap.String()))
-	}
-	return caps
-}
-
 func capsContain(caps []string, s string) bool {
 	for _, c := range caps {
 		if c == s {
@@ -1132,7 +1108,7 @@ func WithDefaultUnixDevices(_ context.Context, _ Client, _ *containers.Container
 
 // WithPrivileged sets up options for a privileged container
 var WithPrivileged = Compose(
-	WithAllCapabilities,
+	WithAllCurrentCapabilities,
 	WithMaskedPaths(nil),
 	WithReadonlyPaths(nil),
 	WithWriteableSysfs,

oci/spec_opts_linux.go

@@ -25,6 +25,7 @@ import (
 	"path/filepath"
 
 	"github.com/containerd/containerd/containers"
+	"github.com/containerd/containerd/pkg/cap"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"golang.org/x/sys/unix"
 )
@@ -180,3 +181,19 @@ func WithCPUCFS(quota int64, period uint64) SpecOpts {
 		return nil
 	}
 }
+
+// WithAllCurrentCapabilities propagates the effective capabilities of the caller process to the container process.
+// The capability set may differ from WithAllKnownCapabilities when running in a container.
+var WithAllCurrentCapabilities = func(ctx context.Context, client Client, c *containers.Container, s *Spec) error {
+	caps, err := cap.Current()
+	if err != nil {
+		return err
+	}
+	return WithCapabilities(caps)(ctx, client, c, s)
+}
+
+// WithAllKnownCapabilities sets all the the known linux capabilities for the container process
+var WithAllKnownCapabilities = func(ctx context.Context, client Client, c *containers.Container, s *Spec) error {
+	caps := cap.Known()
+	return WithCapabilities(caps)(ctx, client, c, s)
+}

oci/spec_opts_nonlinux.go

@@ -0,0 +1,38 @@
+// +build !linux
+
+/*
+   Copyright The containerd Authors.
+
+   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 oci
+
+import (
+	"context"
+
+	"github.com/containerd/containerd/containers"
+)
+
+// WithAllCurrentCapabilities propagates the effective capabilities of the caller process to the container process.
+// The capability set may differ from WithAllKnownCapabilities when running in a container.
+//nolint: deadcode, unused
+var WithAllCurrentCapabilities = func(ctx context.Context, client Client, c *containers.Container, s *Spec) error {
+	return WithCapabilities(nil)(ctx, client, c, s)
+}
+
+// WithAllKnownCapabilities sets all the the known linux capabilities for the container process
+//nolint: deadcode, unused
+var WithAllKnownCapabilities = func(ctx context.Context, client Client, c *containers.Container, s *Spec) error {
+	return WithCapabilities(nil)(ctx, client, c, s)
+}

oci/spec_opts_test.go

@@ -574,7 +574,7 @@ func TestDropCaps(t *testing.T) {
 
 	var s specs.Spec
 
-	if err := WithAllCapabilities(context.Background(), nil, nil, &s); err != nil {
+	if err := WithAllKnownCapabilities(context.Background(), nil, nil, &s); err != nil {
 		t.Fatal(err)
 	}
 	if err := WithDroppedCapabilities([]string{"CAP_CHOWN"})(context.Background(), nil, nil, &s); err != nil {
@@ -593,7 +593,7 @@ func TestDropCaps(t *testing.T) {
 	}
 
 	// Add all capabilities back and drop a different cap.
-	if err := WithAllCapabilities(context.Background(), nil, nil, &s); err != nil {
+	if err := WithAllKnownCapabilities(context.Background(), nil, nil, &s); err != nil {
 		t.Fatal(err)
 	}
 	if err := WithDroppedCapabilities([]string{"CAP_FOWNER"})(context.Background(), nil, nil, &s); err != nil {

oci/spec_test.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/containerd/containerd/containers"
 	"github.com/containerd/containerd/namespaces"
+	"github.com/containerd/containerd/pkg/testutil"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 )
 
@@ -251,6 +252,10 @@ func TestPopulateDefaultUnixSpec(t *testing.T) {
 
 func TestWithPrivileged(t *testing.T) {
 	t.Parallel()
+	if runtime.GOOS == "linux" {
+		// because WithPrivileged depends on CapEff in /proc/self/status
+		testutil.RequiresRoot(t)
+	}
 
 	ctx := namespaces.WithNamespace(context.Background(), "testing")
 
@@ -272,6 +277,10 @@ func TestWithPrivileged(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	if runtime.GOOS != "linux" {
+		return
+	}
+
 	if len(s.Process.Capabilities.Bounding) == 0 {
 		t.Error("Expected capabilities to be set with privileged")
 	}