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Allow user mount for verity fs 

Allow user mounting a verity fs on an existing mount by specifying mount
flags root_hash and lower_path.

PiperOrigin-RevId: 366843846
This commit is contained in:
Chong Cai 2021-04-05 11:56:07 -07:00 committed by gVisor bot
parent 58afd120d3
commit e21a71bff1
6 changed files with 183 additions and 33 deletions
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120
pkg/sentry/fsimpl/verity/verity.go
View File

@ -35,6 +35,7 @@ package verity
import (
"bytes"
"encoding/hex"
"encoding/json"
"fmt"
"math"
@ -105,6 +106,13 @@ var (
verityMu sync.RWMutex
)
// Mount option names for verityfs.
const (
moptLowerPath = "lower_path"
moptRootHash = "root_hash"
moptRootName = "root_name"
)
// HashAlgorithm is a type specifying the algorithm used to hash the file
// content.
type HashAlgorithm int
@ -171,6 +179,9 @@ type filesystem struct {
// system.
alg HashAlgorithm
// opts is the string mount options passed to opts.Data.
opts string
// renameMu synchronizes renaming with non-renaming operations in order
// to ensure consistent lock ordering between dentry.dirMu in different
// dentries.
@ -193,9 +204,6 @@ type filesystem struct {
//
// +stateify savable
type InternalFilesystemOptions struct {
// RootMerkleFileName is the name of the verity root Merkle tree file.
RootMerkleFileName string
// LowerName is the name of the filesystem wrapped by verity fs.
LowerName string
@ -203,9 +211,6 @@ type InternalFilesystemOptions struct {
// system.
Alg HashAlgorithm
// RootHash is the root hash of the overall verity file system.
RootHash []byte
// AllowRuntimeEnable specifies whether the verity file system allows
// enabling verification for files (i.e. building Merkle trees) during
// runtime.
@ -239,28 +244,99 @@ func alertIntegrityViolation(msg string) error {
// GetFilesystem implements vfs.FilesystemType.GetFilesystem.
func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
mopts := vfs.GenericParseMountOptions(opts.Data)
var rootHash []byte
if encodedRootHash, ok := mopts[moptRootHash]; ok {
delete(mopts, moptRootHash)
hash, err := hex.DecodeString(encodedRootHash)
if err != nil {
ctx.Warningf("verity.FilesystemType.GetFilesystem: Failed to decode root hash: %v", err)
return nil, nil, syserror.EINVAL
}
rootHash = hash
}
var lowerPathname string
if path, ok := mopts[moptLowerPath]; ok {
delete(mopts, moptLowerPath)
lowerPathname = path
}
rootName := "root"
if root, ok := mopts[moptRootName]; ok {
delete(mopts, moptRootName)
rootName = root
}
// Check for unparsed options.
if len(mopts) != 0 {
ctx.Warningf("verity.FilesystemType.GetFilesystem: unknown options: %v", mopts)
return nil, nil, syserror.EINVAL
}
// Handle internal options.
iopts, ok := opts.InternalData.(InternalFilesystemOptions)
if !ok {
if len(lowerPathname) == 0 && !ok {
ctx.Warningf("verity.FilesystemType.GetFilesystem: missing verity configs")
return nil, nil, syserror.EINVAL
}
if len(lowerPathname) != 0 {
if ok {
ctx.Warningf("verity.FilesystemType.GetFilesystem: unexpected verity configs with specified lower path")
return nil, nil, syserror.EINVAL
}
iopts = InternalFilesystemOptions{
AllowRuntimeEnable: len(rootHash) == 0,
Action: ErrorOnViolation,
}
}
action = iopts.Action
// Mount the lower file system. The lower file system is wrapped inside
// verity, and should not be exposed or connected.
mopts := &vfs.MountOptions{
GetFilesystemOptions: iopts.LowerGetFSOptions,
InternalMount: true,
}
mnt, err := vfsObj.MountDisconnected(ctx, creds, "", iopts.LowerName, mopts)
if err != nil {
return nil, nil, err
var lowerMount *vfs.Mount
var mountedLowerVD vfs.VirtualDentry
// Use an existing mount if lowerPath is provided.
if len(lowerPathname) != 0 {
vfsroot := vfs.RootFromContext(ctx)
if vfsroot.Ok() {
defer vfsroot.DecRef(ctx)
}
lowerPath := fspath.Parse(lowerPathname)
if !lowerPath.Absolute {
ctx.Infof("verity.FilesystemType.GetFilesystem: lower_path %q must be absolute", lowerPathname)
return nil, nil, syserror.EINVAL
}
var err error
mountedLowerVD, err = vfsObj.GetDentryAt(ctx, creds, &vfs.PathOperation{
Root: vfsroot,
Start: vfsroot,
Path: lowerPath,
FollowFinalSymlink: true,
}, &vfs.GetDentryOptions{
CheckSearchable: true,
})
if err != nil {
ctx.Infof("verity.FilesystemType.GetFilesystem: failed to resolve lower_path %q: %v", lowerPathname, err)
return nil, nil, err
}
lowerMount = mountedLowerVD.Mount()
defer mountedLowerVD.DecRef(ctx)
} else {
// Mount the lower file system. The lower file system is wrapped inside
// verity, and should not be exposed or connected.
mountOpts := &vfs.MountOptions{
GetFilesystemOptions: iopts.LowerGetFSOptions,
InternalMount: true,
}
mnt, err := vfsObj.MountDisconnected(ctx, creds, "", iopts.LowerName, mountOpts)
if err != nil {
return nil, nil, err
}
lowerMount = mnt
}
fs := &filesystem{
creds: creds.Fork(),
alg: iopts.Alg,
lowerMount: mnt,
lowerMount: lowerMount,
opts: opts.Data,
allowRuntimeEnable: iopts.AllowRuntimeEnable,
}
fs.vfsfs.Init(vfsObj, &fstype, fs)
@ -268,11 +344,11 @@ func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt
// Construct the root dentry.
d := fs.newDentry()
d.refs = 1
lowerVD := vfs.MakeVirtualDentry(mnt, mnt.Root())
lowerVD := vfs.MakeVirtualDentry(lowerMount, lowerMount.Root())
lowerVD.IncRef()
d.lowerVD = lowerVD
rootMerkleName := merkleRootPrefix + iopts.RootMerkleFileName
rootMerkleName := merkleRootPrefix + rootName
lowerMerkleVD, err := vfsObj.GetDentryAt(ctx, fs.creds, &vfs.PathOperation{
Root: lowerVD,
@ -352,7 +428,7 @@ func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt
d.mode = uint32(stat.Mode)
d.uid = stat.UID
d.gid = stat.GID
d.hash = make([]byte, len(iopts.RootHash))
d.hash = make([]byte, len(rootHash))
d.childrenNames = make(map[string]struct{})
if !d.isDir() {
@ -427,7 +503,7 @@ func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt
}
d.hashMu.Lock()
copy(d.hash, iopts.RootHash)
copy(d.hash, rootHash)
d.hashMu.Unlock()
d.vfsd.Init(d)
@ -443,7 +519,7 @@ func (fs *filesystem) Release(ctx context.Context) {
// MountOptions implements vfs.FilesystemImpl.MountOptions.
func (fs *filesystem) MountOptions() string {
return ""
return fs.opts
}
// dentry implements vfs.DentryImpl.

3
pkg/sentry/fsimpl/verity/verity_test.go
View File

@ -89,10 +89,11 @@ func newVerityRoot(t *testing.T, hashAlg HashAlgorithm) (*vfs.VirtualFilesystem,
AllowUserMount: true,
})
data := "root_name=" + rootMerkleFilename
mntns, err := vfsObj.NewMountNamespace(ctx, auth.CredentialsFromContext(ctx), "", "verity", &vfs.MountOptions{
GetFilesystemOptions: vfs.GetFilesystemOptions{
Data: data,
InternalData: InternalFilesystemOptions{
RootMerkleFileName: rootMerkleFilename,
LowerName: "tmpfs",
Alg: hashAlg,
AllowRuntimeEnable: true,

22
runsc/boot/vfs.go
View File

@ -92,7 +92,7 @@ func registerFilesystems(k *kernel.Kernel) error {
})
vfsObj.MustRegisterFilesystemType(verity.Name, &verity.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
AllowUserList: true,
AllowUserMount: false,
AllowUserMount: true,
})
// Setup files in devtmpfs.
@ -483,7 +483,7 @@ func (c *containerMounter) getMountNameAndOptionsVFS2(conf *config.Config, m *mo
var data []string
var iopts interface{}
verityOpts, verityRequested, remainingMOpts, err := parseVerityMountOptions(m.Options)
verityData, verityOpts, verityRequested, remainingMOpts, err := parseVerityMountOptions(m.Options)
if err != nil {
return "", nil, false, err
}
@ -555,13 +555,13 @@ func (c *containerMounter) getMountNameAndOptionsVFS2(conf *config.Config, m *mo
}
if verityRequested {
verityOpts.RootMerkleFileName = path.Base(m.Mount.Destination)
verityData = verityData + "root_name=" + path.Base(m.Mount.Destination)
verityOpts.LowerName = fsName
verityOpts.LowerGetFSOptions = opts.GetFilesystemOptions
fsName = verity.Name
opts = &vfs.MountOptions{
GetFilesystemOptions: vfs.GetFilesystemOptions{
Data: strings.Join(data, ","),
Data: verityData,
InternalData: verityOpts,
},
InternalMount: true,
@ -582,9 +582,10 @@ func parseKeyValue(s string) (string, string, bool) {
// parseAndFilterOptions scans the provided mount options for verity-related
// mount options. It returns the parsed set of verity mount options, as well as
// the filtered set of mount options unrelated to verity.
func parseVerityMountOptions(mopts []string) (verity.InternalFilesystemOptions, bool, []string, error) {
func parseVerityMountOptions(mopts []string) (string, verity.InternalFilesystemOptions, bool, []string, error) {
nonVerity := []string{}
found := false
var rootHash string
verityOpts := verity.InternalFilesystemOptions{
Action: verity.PanicOnViolation,
}
@ -596,13 +597,13 @@ func parseVerityMountOptions(mopts []string) (verity.InternalFilesystemOptions,
k, v, ok := parseKeyValue(o)
if !ok {
return verityOpts, found, nonVerity, fmt.Errorf("invalid verity mount option with no value: %q", o)
return "", verityOpts, found, nonVerity, fmt.Errorf("invalid verity mount option with no value: %q", o)
}
found = true
switch k {
case "verity.roothash":
verityOpts.RootHash = []byte(v)
rootHash = v
case "verity.action":
switch v {
case "error":
@ -614,11 +615,12 @@ func parseVerityMountOptions(mopts []string) (verity.InternalFilesystemOptions,
verityOpts.Action = verity.PanicOnViolation
}
default:
return verityOpts, found, nonVerity, fmt.Errorf("unknown verity mount option: %q", k)
return "", verityOpts, found, nonVerity, fmt.Errorf("unknown verity mount option: %q", k)
}
}
verityOpts.AllowRuntimeEnable = len(verityOpts.RootHash) == 0
return verityOpts, found, nonVerity, nil
verityOpts.AllowRuntimeEnable = len(rootHash) == 0
verityData := "root_hash=" + rootHash + ","
return verityData, verityOpts, found, nonVerity, nil
}
// mountTmpVFS2 mounts an internal tmpfs at '/tmp' if it's safe to do so.

4
test/syscalls/BUILD
View File

@ -317,6 +317,10 @@ syscall_test(
test = "//test/syscalls/linux:mount_test",
)
syscall_test(
test = "//test/syscalls/linux:verity_mount_test",
)
syscall_test(
size = "medium",
test = "//test/syscalls/linux:mremap_test",

14
test/syscalls/linux/BUILD
View File

@ -1303,6 +1303,20 @@ cc_binary(
],
)
cc_binary(
name = "verity_mount_test",
testonly = 1,
srcs = ["verity_mount.cc"],
linkstatic = 1,
deps = [
gtest,
"//test/util:capability_util",
"//test/util:temp_path",
"//test/util:test_main",
"//test/util:test_util",
],
)
cc_binary(
name = "mremap_test",
testonly = 1,

53
test/syscalls/linux/verity_mount.cc Normal file
View File

@ -0,0 +1,53 @@
// 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.
#include <sys/mount.h>
#include <iomanip>
#include <sstream>
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "test/util/capability_util.h"
#include "test/util/temp_path.h"
#include "test/util/test_util.h"
namespace gvisor {
namespace testing {
namespace {
// Mount verity file system on an existing gofer mount.
TEST(MountTest, MountExisting) {
// Verity is implemented in VFS2.
SKIP_IF(IsRunningWithVFS1());
SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SYS_ADMIN)));
// Mount a new tmpfs file system.
auto const tmpfs_dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
ASSERT_THAT(mount("", tmpfs_dir.path().c_str(), "tmpfs", 0, ""),
SyscallSucceeds());
// Mount a verity file system on the existing gofer mount.
auto const verity_dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
std::string opts = "lower_path=" + tmpfs_dir.path();
EXPECT_THAT(mount("", verity_dir.path().c_str(), "verity", 0, opts.c_str()),
SyscallSucceeds());
}
} // namespace
} // namespace testing
} // namespace gvisor