Fix sandbox chroot

Sandbox was setting chroot, but was not chaging the working
dir. Added test to ensure this doesn't happen in the future.

PiperOrigin-RevId: 215676270
Change-Id: I14352d3de64a4dcb90e50948119dc8328c9c15e1

3 files changed, 146 insertions, 0 deletions

diff --git a/runsc/test/root/BUILD b/runsc/test/root/BUILD
new file mode 100644
index 000000000..dbc0f1d26
--- /dev/null
+++ b/runsc/test/root/BUILD
@@ -0,0 +1,27 @@
+package(licenses = ["notice"])  # Apache 2.0
+
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "root",
+    srcs = ["root.go"],
+    importpath = "gvisor.googlesource.com/gvisor/runsc/test/root",
+)
+
+go_test(
+    name = "root_test",
+    size = "small",
+    srcs = ["chroot_test.go"],
+    embed = [":root"],
+    tags = [
+        # Requires docker and runsc to be configured before the test runs.
+        # Also test only runs as root.
+        "manual",
+        "local",
+    ],
+    deps = [
+        "//runsc/specutils",
+        "//runsc/test/testutil",
+        "@com_github_syndtr_gocapability//capability:go_default_library",
+    ],
+)
diff --git a/runsc/test/root/chroot_test.go b/runsc/test/root/chroot_test.go
new file mode 100644
index 000000000..5c59e7451
--- /dev/null
+++ b/runsc/test/root/chroot_test.go
@@ -0,0 +1,103 @@
+// Copyright 2018 Google Inc.
+//
+// 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 root is used for tests that requires sysadmin privileges run. First,
+// follow the setup instruction in runsc/test/README.md. To run these test:
+//
+//     bazel build //runsc/test/root:root_test
+//     root_test=$(find -L ./bazel-bin/ -executable -type f -name root_test | grep __main__)
+//     sudo RUNSC_RUNTIME=runsc-test ${root_test}
+package root
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"reflect"
+	"sort"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/syndtr/gocapability/capability"
+	"gvisor.googlesource.com/gvisor/runsc/specutils"
+	"gvisor.googlesource.com/gvisor/runsc/test/testutil"
+)
+
+// TestChroot verifies that the sandbox is chroot'd and that mounts are cleaned
+// up after the sandbox is destroyed.
+func TestChroot(t *testing.T) {
+	d := testutil.MakeDocker("chroot-test")
+	if err := d.Run("alpine", "sleep", "10000"); err != nil {
+		t.Fatalf("docker run failed: %v", err)
+	}
+	defer d.CleanUp()
+
+	pid, err := d.SandboxPid()
+	if err != nil {
+		t.Fatalf("Docker.SandboxPid(): %v", err)
+	}
+
+	// Check that sandbox is chroot'ed.
+	chroot, err := filepath.EvalSymlinks(filepath.Join("/proc", strconv.Itoa(pid), "root"))
+	if err != nil {
+		t.Fatalf("error resolving /proc/<pid>/root symlink: %v", err)
+	}
+	if want := "/tmp/runsc-sandbox-chroot-"; !strings.HasPrefix(chroot, want) {
+		t.Errorf("sandbox is not chroot'd, it should be inside: %q, got: %q", want, chroot)
+	}
+
+	path, err := filepath.EvalSymlinks(filepath.Join("/proc", strconv.Itoa(pid), "cwd"))
+	if err != nil {
+		t.Fatalf("error resolving /proc/<pid>/cwd symlink: %v", err)
+	}
+	if chroot != path {
+		t.Errorf("sandbox current dir is wrong, want: %q, got: %q", chroot, path)
+	}
+
+	fi, err := ioutil.ReadDir(chroot)
+	if err != nil {
+		t.Fatalf("error listing %q: %v", chroot, err)
+	}
+	if want, got := 2, len(fi); want != got {
+		t.Fatalf("chroot dir got %d entries, want %d", want, got)
+	}
+
+	// chroot dir is prepared by runsc and should contains only the executable
+	// and /proc.
+	files := []string{fi[0].Name(), fi[1].Name()}
+	sort.Strings(files)
+	if want := []string{"proc", "runsc"}; !reflect.DeepEqual(files, want) {
+		t.Errorf("chroot got children %v, want %v", files, want)
+	}
+
+	d.CleanUp()
+
+	// Check that chroot directory was cleaned up.
+	if _, err := os.Stat(chroot); err == nil || !os.IsNotExist(err) {
+		t.Errorf("chroot directory %q was not deleted: %v", chroot, err)
+	}
+}
+
+func TestMain(m *testing.M) {
+	testutil.EnsureSupportedDockerVersion()
+
+	if !specutils.HasCapabilities(capability.CAP_SYS_ADMIN, capability.CAP_DAC_OVERRIDE) {
+		fmt.Println("Test requires sysadmin privileges to run. Try again with sudo.")
+		os.Exit(1)
+	}
+
+	os.Exit(m.Run())
+}
diff --git a/runsc/test/root/root.go b/runsc/test/root/root.go
new file mode 100644
index 000000000..790f62c29
--- /dev/null
+++ b/runsc/test/root/root.go
@@ -0,0 +1,16 @@
+// Copyright 2018 Google Inc.
+//
+// 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 root is empty. See chroot_test.go for description.
+package root