Implement the runsc verity-prepare command.

Implement a new runsc command to set up a sandbox with verityfs and
run the measure tool. This is loosely forked from the do command, and
currently requires the caller to provide the measure tool binary.

PiperOrigin-RevId: 366553769

3 files changed, 164 insertions, 51 deletions

diff --git a/runsc/cmd/BUILD b/runsc/cmd/BUILD
index 2c3b4058b..4b9987cf6 100644
--- a/runsc/cmd/BUILD
+++ b/runsc/cmd/BUILD
@@ -35,6 +35,7 @@ go_library(
         "statefile.go",
         "symbolize.go",
         "syscalls.go",
+        "verity_prepare.go",
         "wait.go",
     ],
     visibility = [
diff --git a/runsc/cmd/do.go b/runsc/cmd/do.go
index 455c57692..5485db149 100644
--- a/runsc/cmd/do.go
+++ b/runsc/cmd/do.go
@@ -126,9 +126,8 @@ func (c *Do) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) su
 		Hostname: hostname,
 	}
 
-	specutils.LogSpec(spec)
-
 	cid := fmt.Sprintf("runsc-%06d", rand.Int31n(1000000))
+
 	if conf.Network == config.NetworkNone {
 		addNamespace(spec, specs.LinuxNamespace{Type: specs.NetworkNamespace})
 
@@ -154,55 +153,7 @@ func (c *Do) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) su
 		}
 	}
 
-	out, err := json.Marshal(spec)
-	if err != nil {
-		return Errorf("Error to marshal spec: %v", err)
-	}
-	tmpDir, err := ioutil.TempDir("", "runsc-do")
-	if err != nil {
-		return Errorf("Error to create tmp dir: %v", err)
-	}
-	defer os.RemoveAll(tmpDir)
-
-	log.Infof("Changing configuration RootDir to %q", tmpDir)
-	conf.RootDir = tmpDir
-
-	cfgPath := filepath.Join(tmpDir, "config.json")
-	if err := ioutil.WriteFile(cfgPath, out, 0755); err != nil {
-		return Errorf("Error write spec: %v", err)
-	}
-
-	containerArgs := container.Args{
-		ID:        cid,
-		Spec:      spec,
-		BundleDir: tmpDir,
-		Attached:  true,
-	}
-	ct, err := container.New(conf, containerArgs)
-	if err != nil {
-		return Errorf("creating container: %v", err)
-	}
-	defer ct.Destroy()
-
-	if err := ct.Start(conf); err != nil {
-		return Errorf("starting container: %v", err)
-	}
-
-	// Forward signals to init in the container. Thus if we get SIGINT from
-	// ^C, the container gracefully exit, and we can clean up.
-	//
-	// N.B. There is a still a window before this where a signal may kill
-	// this process, skipping cleanup.
-	stopForwarding := ct.ForwardSignals(0 /* pid */, false /* fgProcess */)
-	defer stopForwarding()
-
-	ws, err := ct.Wait()
-	if err != nil {
-		return Errorf("waiting for container: %v", err)
-	}
-
-	*waitStatus = ws
-	return subcommands.ExitSuccess
+	return startContainerAndWait(spec, conf, cid, waitStatus)
 }
 
 func addNamespace(spec *specs.Spec, ns specs.LinuxNamespace) {
@@ -397,3 +348,58 @@ func calculatePeerIP(ip string) (string, error) {
 	}
 	return fmt.Sprintf("%s.%s.%s.%d", parts[0], parts[1], parts[2], n), nil
 }
+
+func startContainerAndWait(spec *specs.Spec, conf *config.Config, cid string, waitStatus *unix.WaitStatus) subcommands.ExitStatus {
+	specutils.LogSpec(spec)
+
+	out, err := json.Marshal(spec)
+	if err != nil {
+		return Errorf("Error to marshal spec: %v", err)
+	}
+	tmpDir, err := ioutil.TempDir("", "runsc-do")
+	if err != nil {
+		return Errorf("Error to create tmp dir: %v", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	log.Infof("Changing configuration RootDir to %q", tmpDir)
+	conf.RootDir = tmpDir
+
+	cfgPath := filepath.Join(tmpDir, "config.json")
+	if err := ioutil.WriteFile(cfgPath, out, 0755); err != nil {
+		return Errorf("Error write spec: %v", err)
+	}
+
+	containerArgs := container.Args{
+		ID:        cid,
+		Spec:      spec,
+		BundleDir: tmpDir,
+		Attached:  true,
+	}
+
+	ct, err := container.New(conf, containerArgs)
+	if err != nil {
+		return Errorf("creating container: %v", err)
+	}
+	defer ct.Destroy()
+
+	if err := ct.Start(conf); err != nil {
+		return Errorf("starting container: %v", err)
+	}
+
+	// Forward signals to init in the container. Thus if we get SIGINT from
+	// ^C, the container gracefully exit, and we can clean up.
+	//
+	// N.B. There is a still a window before this where a signal may kill
+	// this process, skipping cleanup.
+	stopForwarding := ct.ForwardSignals(0 /* pid */, false /* fgProcess */)
+	defer stopForwarding()
+
+	ws, err := ct.Wait()
+	if err != nil {
+		return Errorf("waiting for container: %v", err)
+	}
+
+	*waitStatus = ws
+	return subcommands.ExitSuccess
+}
diff --git a/runsc/cmd/verity_prepare.go b/runsc/cmd/verity_prepare.go
new file mode 100644
index 000000000..2197cd3f8
--- /dev/null
+++ b/runsc/cmd/verity_prepare.go
@@ -0,0 +1,106 @@
+// Copyright 2021 The gVisor 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 cmd
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"os"
+
+	"github.com/google/subcommands"
+	specs "github.com/opencontainers/runtime-spec/specs-go"
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/runsc/config"
+	"gvisor.dev/gvisor/runsc/flag"
+	"gvisor.dev/gvisor/runsc/specutils"
+)
+
+// VerityPrepare implements subcommands.Commands for the "verity-prepare"
+// command. It sets up a sandbox with a writable verity mount mapped to "--dir",
+// and executes the verity measure tool specified by "--tool" in the sandbox. It
+// is intended to prepare --dir to be mounted as a verity filesystem.
+type VerityPrepare struct {
+	root string
+	tool string
+	dir  string
+}
+
+// Name implements subcommands.Command.Name.
+func (*VerityPrepare) Name() string {
+	return "verity-prepare"
+}
+
+// Synopsis implements subcommands.Command.Synopsis.
+func (*VerityPrepare) Synopsis() string {
+	return "Generates the data structures necessary to enable verityfs on a filesystem."
+}
+
+// Usage implements subcommands.Command.Usage.
+func (*VerityPrepare) Usage() string {
+	return "verity-prepare --tool=<measure_tool> --dir=<path>"
+}
+
+// SetFlags implements subcommands.Command.SetFlags.
+func (c *VerityPrepare) SetFlags(f *flag.FlagSet) {
+	f.StringVar(&c.root, "root", "/", `path to the root directory, defaults to "/"`)
+	f.StringVar(&c.tool, "tool", "", "path to the verity measure_tool")
+	f.StringVar(&c.dir, "dir", "", "path to the directory to be hashed")
+}
+
+// Execute implements subcommands.Command.Execute.
+func (c *VerityPrepare) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	conf := args[0].(*config.Config)
+	waitStatus := args[1].(*unix.WaitStatus)
+
+	hostname, err := os.Hostname()
+	if err != nil {
+		return Errorf("Error to retrieve hostname: %v", err)
+	}
+
+	// Map the entire host file system.
+	absRoot, err := resolvePath(c.root)
+	if err != nil {
+		return Errorf("Error resolving root: %v", err)
+	}
+
+	spec := &specs.Spec{
+		Root: &specs.Root{
+			Path: absRoot,
+		},
+		Process: &specs.Process{
+			Cwd:          absRoot,
+			Args:         []string{c.tool, "--path", "/verityroot"},
+			Env:          os.Environ(),
+			Capabilities: specutils.AllCapabilities(),
+		},
+		Hostname: hostname,
+		Mounts: []specs.Mount{
+			specs.Mount{
+				Source:      c.dir,
+				Destination: "/verityroot",
+				Type:        "bind",
+				Options:     []string{"verity.roothash="},
+			},
+		},
+	}
+
+	cid := fmt.Sprintf("runsc-%06d", rand.Int31n(1000000))
+
+	// Force no networking, it is not necessary to run the verity measure tool.
+	conf.Network = config.NetworkNone
+
+	return startContainerAndWait(spec, conf, cid, waitStatus)
+}