Fix addition group ids.

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/containerd/opts/spec.go

@@ -0,0 +1,51 @@
+/*
+Copyright 2018 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 opts
+
+import (
+	"context"
+
+	"github.com/containerd/containerd/containers"
+	"github.com/containerd/containerd/oci"
+	runtimespec "github.com/opencontainers/runtime-spec/specs-go"
+)
+
+// WithAdditionalGIDs adds any additional groups listed for a particular user in the
+// /etc/groups file of the image's root filesystem to the OCI spec's additionalGids array.
+func WithAdditionalGIDs(userstr string) oci.SpecOpts {
+	return func(ctx context.Context, client oci.Client, c *containers.Container, s *runtimespec.Spec) (err error) {
+		gids := s.Process.User.AdditionalGids
+		if err := oci.WithAdditionalGIDs(userstr)(ctx, client, c, s); err != nil {
+			return err
+		}
+		// Merge existing gids and new gids.
+		s.Process.User.AdditionalGids = mergeGids(s.Process.User.AdditionalGids, gids)
+		return nil
+	}
+}
+
+func mergeGids(gids1, gids2 []uint32) []uint32 {
+	for _, gid1 := range gids1 {
+		for i, gid2 := range gids2 {
+			if gid1 == gid2 {
+				gids2 = append(gids2[:i], gids2[i+1:]...)
+				break
+			}
+		}
+	}
+	return append(gids1, gids2...)
+}

pkg/containerd/opts/spec_test.go

@@ -0,0 +1,29 @@
+/*
+Copyright 2018 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 opts
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMergeGids(t *testing.T) {
+	gids1 := []uint32{3, 2, 1}
+	gids2 := []uint32{2, 3, 4}
+	assert.Equal(t, []uint32{3, 2, 1, 4}, mergeGids(gids1, gids2))
+}

pkg/server/container_create.go

@@ -229,6 +229,15 @@ func (c *criService) CreateContainer(ctx context.Context, r *runtime.CreateConta
 		specOpts = append(specOpts, oci.WithUser(userstr))
 	}
 
+	if securityContext.GetRunAsUsername() != "" {
+		userstr = securityContext.GetRunAsUsername()
+	} else {
+		// Even if RunAsUser is not set, we still call `GetValue` to get uid 0.
+		// Because it is still useful to get additional gids for uid 0.
+		userstr = strconv.FormatInt(securityContext.GetRunAsUser().GetValue(), 10)
+	}
+	specOpts = append(specOpts, customopts.WithAdditionalGIDs(userstr))
+
 	apparmorSpecOpts, err := generateApparmorSpecOpts(
 		securityContext.GetApparmorProfile(),
 		securityContext.GetPrivileged(),