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ceph-csi/vendor/github.com/google/fscrypt/metadata/policy.go

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/*
* policy.go - Functions for getting and setting policies on a specified
* directory or file.
*
* Copyright 2017 Google Inc.
* Author: Joe Richey (joerichey@google.com)
*
* 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 metadata
import (
"encoding/hex"
"fmt"
"log"
"math"
"os"
"os/user"
"strconv"
"unsafe"
"github.com/pkg/errors"
"golang.org/x/sys/unix"
"github.com/google/fscrypt/util"
)
var (
// ErrEncryptionNotSupported indicates that encryption is not supported
// on the given filesystem, and there is no way to enable it.
ErrEncryptionNotSupported = errors.New("encryption not supported")
// ErrEncryptionNotEnabled indicates that encryption is not supported on
// the given filesystem, but there is a way to enable it.
ErrEncryptionNotEnabled = errors.New("encryption not enabled")
)
// ErrAlreadyEncrypted indicates that the path is already encrypted.
type ErrAlreadyEncrypted struct {
Path string
}
func (err *ErrAlreadyEncrypted) Error() string {
return fmt.Sprintf("file or directory %q is already encrypted", err.Path)
}
// ErrBadEncryptionOptions indicates that unsupported encryption options were given.
type ErrBadEncryptionOptions struct {
Path string
Options *EncryptionOptions
}
func (err *ErrBadEncryptionOptions) Error() string {
return fmt.Sprintf(`cannot encrypt %q because the kernel doesn't support the requested encryption options.
The options are %s`, err.Path, err.Options)
}
// ErrDirectoryNotOwned indicates a directory can't be encrypted because it's
// owned by another user.
type ErrDirectoryNotOwned struct {
Path string
Owner uint32
}
func (err *ErrDirectoryNotOwned) Error() string {
owner := strconv.Itoa(int(err.Owner))
if u, e := user.LookupId(owner); e == nil && u.Username != "" {
owner = u.Username
}
return fmt.Sprintf(`cannot encrypt %q because it's owned by another user (%s).
Encryption can only be enabled on a directory you own, even if you have
write access to the directory.`, err.Path, owner)
}
// ErrNotEncrypted indicates that the path is not encrypted.
type ErrNotEncrypted struct {
Path string
}
func (err *ErrNotEncrypted) Error() string {
return fmt.Sprintf("file or directory %q is not encrypted", err.Path)
}
func policyIoctl(file *os.File, request uintptr, arg unsafe.Pointer) error {
_, _, errno := unix.Syscall(unix.SYS_IOCTL, file.Fd(), request, uintptr(arg))
if errno == 0 {
return nil
}
return errno
}
// Maps EncryptionOptions.Padding <-> FSCRYPT_POLICY_FLAGS
var (
paddingArray = []int64{4, 8, 16, 32}
flagsArray = []int64{unix.FSCRYPT_POLICY_FLAGS_PAD_4, unix.FSCRYPT_POLICY_FLAGS_PAD_8,
unix.FSCRYPT_POLICY_FLAGS_PAD_16, unix.FSCRYPT_POLICY_FLAGS_PAD_32}
)
// flagsToPadding returns the amount of padding specified in the policy flags.
func flagsToPadding(flags uint8) int64 {
paddingFlag := int64(flags & unix.FS_POLICY_FLAGS_PAD_MASK)
// This lookup should always succeed
padding, ok := util.Lookup(paddingFlag, flagsArray, paddingArray)
if !ok {
log.Panicf("padding flag of %x not found", paddingFlag)
}
return padding
}
func buildV1PolicyData(policy *unix.FscryptPolicyV1) *PolicyData {
return &PolicyData{
KeyDescriptor: hex.EncodeToString(policy.Master_key_descriptor[:]),
Options: &EncryptionOptions{
Padding: flagsToPadding(policy.Flags),
Contents: EncryptionOptions_Mode(policy.Contents_encryption_mode),
Filenames: EncryptionOptions_Mode(policy.Filenames_encryption_mode),
PolicyVersion: 1,
},
}
}
func buildV2PolicyData(policy *unix.FscryptPolicyV2) *PolicyData {
return &PolicyData{
KeyDescriptor: hex.EncodeToString(policy.Master_key_identifier[:]),
Options: &EncryptionOptions{
Padding: flagsToPadding(policy.Flags),
Contents: EncryptionOptions_Mode(policy.Contents_encryption_mode),
Filenames: EncryptionOptions_Mode(policy.Filenames_encryption_mode),
PolicyVersion: 2,
},
}
}
// GetPolicy returns the Policy data for the given directory or file (includes
// the KeyDescriptor and the encryption options). Returns an error if the
// path is not encrypted or the policy couldn't be retrieved.
func GetPolicy(path string) (*PolicyData, error) {
file, err := os.Open(path)
if err != nil {
return nil, err
}
defer file.Close()
// First try the new version of the ioctl. This works for both v1 and v2 policies.
var arg unix.FscryptGetPolicyExArg
arg.Size = uint64(unsafe.Sizeof(arg.Policy))
policyPtr := util.Ptr(arg.Policy[:])
err = policyIoctl(file, unix.FS_IOC_GET_ENCRYPTION_POLICY_EX, unsafe.Pointer(&arg))
if err == unix.ENOTTY {
// Fall back to the old version of the ioctl. This works for v1 policies only.
err = policyIoctl(file, unix.FS_IOC_GET_ENCRYPTION_POLICY, policyPtr)
arg.Size = uint64(unsafe.Sizeof(unix.FscryptPolicyV1{}))
}
switch err {
case nil:
break
case unix.ENOTTY:
return nil, ErrEncryptionNotSupported
case unix.EOPNOTSUPP:
return nil, ErrEncryptionNotEnabled
case unix.ENODATA, unix.ENOENT:
// ENOENT was returned instead of ENODATA on some filesystems before v4.11.
return nil, &ErrNotEncrypted{path}
default:
return nil, errors.Wrapf(err, "failed to get encryption policy of %q", path)
}
switch arg.Policy[0] { // arg.policy.version
case unix.FSCRYPT_POLICY_V1:
if arg.Size != uint64(unsafe.Sizeof(unix.FscryptPolicyV1{})) {
// should never happen
return nil, errors.New("unexpected size for v1 policy")
}
return buildV1PolicyData((*unix.FscryptPolicyV1)(policyPtr)), nil
case unix.FSCRYPT_POLICY_V2:
if arg.Size != uint64(unsafe.Sizeof(unix.FscryptPolicyV2{})) {
// should never happen
return nil, errors.New("unexpected size for v2 policy")
}
return buildV2PolicyData((*unix.FscryptPolicyV2)(policyPtr)), nil
default:
return nil, errors.Errorf("unsupported encryption policy version [%d]",
arg.Policy[0])
}
}
// For improved performance, use the DIRECT_KEY flag when using ciphers that
// support it, e.g. Adiantum. It is safe because fscrypt won't reuse the key
// for any other policy. (Multiple directories with same policy are okay.)
func shouldUseDirectKeyFlag(options *EncryptionOptions) bool {
// Contents and filenames encryption modes must be the same
if options.Contents != options.Filenames {
return false
}
// Currently only Adiantum supports DIRECT_KEY.
return options.Contents == EncryptionOptions_Adiantum
}
func buildPolicyFlags(options *EncryptionOptions) uint8 {
// This lookup should always succeed (as policy is valid)
flags, ok := util.Lookup(options.Padding, paddingArray, flagsArray)
if !ok {
log.Panicf("padding of %d was not found", options.Padding)
}
if shouldUseDirectKeyFlag(options) {
flags |= unix.FSCRYPT_POLICY_FLAG_DIRECT_KEY
}
return uint8(flags)
}
func setV1Policy(file *os.File, options *EncryptionOptions, descriptorBytes []byte) error {
policy := unix.FscryptPolicyV1{
Version: unix.FSCRYPT_POLICY_V1,
Contents_encryption_mode: uint8(options.Contents),
Filenames_encryption_mode: uint8(options.Filenames),
Flags: uint8(buildPolicyFlags(options)),
}
// The descriptor should always be the correct length (as policy is valid)
if len(descriptorBytes) != unix.FSCRYPT_KEY_DESCRIPTOR_SIZE {
log.Panic("wrong descriptor size for v1 policy")
}
copy(policy.Master_key_descriptor[:], descriptorBytes)
return policyIoctl(file, unix.FS_IOC_SET_ENCRYPTION_POLICY, unsafe.Pointer(&policy))
}
func setV2Policy(file *os.File, options *EncryptionOptions, descriptorBytes []byte) error {
policy := unix.FscryptPolicyV2{
Version: unix.FSCRYPT_POLICY_V2,
Contents_encryption_mode: uint8(options.Contents),
Filenames_encryption_mode: uint8(options.Filenames),
Flags: uint8(buildPolicyFlags(options)),
}
// The descriptor should always be the correct length (as policy is valid)
if len(descriptorBytes) != unix.FSCRYPT_KEY_IDENTIFIER_SIZE {
log.Panic("wrong descriptor size for v2 policy")
}
copy(policy.Master_key_identifier[:], descriptorBytes)
return policyIoctl(file, unix.FS_IOC_SET_ENCRYPTION_POLICY, unsafe.Pointer(&policy))
}
// SetPolicy sets up the specified directory to be encrypted with the specified
// policy. Returns an error if we cannot set the policy for any reason (not a
// directory, invalid options or KeyDescriptor, etc).
func SetPolicy(path string, data *PolicyData) error {
file, err := os.Open(path)
if err != nil {
return err
}
defer file.Close()
if err = data.CheckValidity(); err != nil {
return errors.Wrap(err, "invalid policy")
}
descriptorBytes, err := hex.DecodeString(data.KeyDescriptor)
if err != nil {
return errors.New("invalid key descriptor: " + data.KeyDescriptor)
}
switch data.Options.PolicyVersion {
case 1:
err = setV1Policy(file, data.Options, descriptorBytes)
case 2:
err = setV2Policy(file, data.Options, descriptorBytes)
default:
err = errors.Errorf("policy version of %d is invalid", data.Options.PolicyVersion)
}
if err == unix.EINVAL {
// Before kernel v4.11, many different errors all caused unix.EINVAL to be returned.
// We try to disambiguate this error here. This disambiguation will not always give
// the correct error due to a potential race condition on path.
if info, statErr := os.Stat(path); statErr != nil || !info.IsDir() {
// Checking if the path is not a directory
err = unix.ENOTDIR
} else if _, policyErr := GetPolicy(path); policyErr == nil {
// Checking if a policy is already set on this directory
err = unix.EEXIST
}
}
switch err {
case nil:
return nil
case unix.EACCES:
var stat unix.Stat_t
if statErr := unix.Stat(path, &stat); statErr == nil && stat.Uid != uint32(os.Geteuid()) {
return &ErrDirectoryNotOwned{path, stat.Uid}
}
case unix.EEXIST:
return &ErrAlreadyEncrypted{path}
case unix.EINVAL:
return &ErrBadEncryptionOptions{path, data.Options}
case unix.ENOTTY:
return ErrEncryptionNotSupported
case unix.EOPNOTSUPP:
return ErrEncryptionNotEnabled
}
return errors.Wrapf(err, "failed to set encryption policy on %q", path)
}
// CheckSupport returns an error if the filesystem containing path does not
// support filesystem encryption. This can be for many reasons including an
// incompatible kernel or filesystem or not enabling the right feature flags.
func CheckSupport(path string) error {
file, err := os.Open(path)
if err != nil {
return err
}
defer file.Close()
// On supported directories, giving a bad policy will return EINVAL
badPolicy := unix.FscryptPolicyV1{
Version: math.MaxUint8,
Contents_encryption_mode: math.MaxUint8,
Filenames_encryption_mode: math.MaxUint8,
Flags: math.MaxUint8,
}
err = policyIoctl(file, unix.FS_IOC_SET_ENCRYPTION_POLICY, unsafe.Pointer(&badPolicy))
switch err {
case nil:
log.Panicf(`FS_IOC_SET_ENCRYPTION_POLICY succeeded when it should have failed.
Please open an issue, filesystem %q may be corrupted.`, path)
case unix.EINVAL, unix.EACCES:
return nil
case unix.ENOTTY:
return ErrEncryptionNotSupported
case unix.EOPNOTSUPP:
return ErrEncryptionNotEnabled
}
return errors.Wrapf(err, "unexpected error checking for encryption support on filesystem %q", path)
}