ceph-csi/vendor/github.com/google/fscrypt/actions/config.go
Marcel Lauhoff f8faffac89 vendor: vendor fscrypt integration dependencies
Signed-off-by: Marcel Lauhoff <marcel.lauhoff@suse.com>
2022-10-17 17:33:52 +00:00

294 lines
9.3 KiB
Go

/*
* config.go - Actions for creating a new config file, which includes new
* hashing costs and the config file's location.
*
* 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 actions
import (
"bytes"
"fmt"
"log"
"os"
"runtime"
"time"
"golang.org/x/sys/unix"
"github.com/google/fscrypt/crypto"
"github.com/google/fscrypt/filesystem"
"github.com/google/fscrypt/metadata"
"github.com/google/fscrypt/util"
)
// ConfigFileLocation is the location of fscrypt's global settings. This can be
// overridden by the user of this package.
var ConfigFileLocation = "/etc/fscrypt.conf"
// ErrBadConfig is an internal error that indicates that the config struct is invalid.
type ErrBadConfig struct {
Config *metadata.Config
UnderlyingError error
}
func (err *ErrBadConfig) Error() string {
return fmt.Sprintf(`internal error: config is invalid: %s
The invalid config is %s`, err.UnderlyingError, err.Config)
}
// ErrBadConfigFile indicates that the config file is invalid.
type ErrBadConfigFile struct {
Path string
UnderlyingError error
}
func (err *ErrBadConfigFile) Error() string {
return fmt.Sprintf("%q is invalid: %s", err.Path, err.UnderlyingError)
}
// ErrConfigFileExists indicates that the config file already exists.
type ErrConfigFileExists struct {
Path string
}
func (err *ErrConfigFileExists) Error() string {
return fmt.Sprintf("%q already exists", err.Path)
}
// ErrNoConfigFile indicates that the config file doesn't exist.
type ErrNoConfigFile struct {
Path string
}
func (err *ErrNoConfigFile) Error() string {
return fmt.Sprintf("%q doesn't exist", err.Path)
}
const (
// Permissions of the config file (global readable)
configPermissions = 0644
// Config file should be created for writing and not already exist
createFlags = os.O_CREATE | os.O_WRONLY | os.O_EXCL
// 128 MiB is a large enough amount of memory to make the password hash
// very difficult to brute force on specialized hardware, but small
// enough to work on most GNU/Linux systems.
maxMemoryBytes = 128 * 1024 * 1024
)
var (
timingPassphrase = []byte("I am a fake passphrase")
timingSalt = bytes.Repeat([]byte{42}, metadata.SaltLen)
)
// CreateConfigFile creates a new config file at the appropriate location with
// the appropriate hashing costs and encryption parameters. The hashing will be
// configured to take as long as the specified time target. In addition, the
// version of encryption policy to use may be overridden from the default of v1.
func CreateConfigFile(target time.Duration, policyVersion int64) error {
// Create the config file before computing the hashing costs, so we fail
// immediately if the program has insufficient permissions.
configFile, err := filesystem.OpenFileOverridingUmask(ConfigFileLocation,
createFlags, configPermissions)
switch {
case os.IsExist(err):
return &ErrConfigFileExists{ConfigFileLocation}
case err != nil:
return err
}
defer configFile.Close()
config := &metadata.Config{
Source: metadata.DefaultSource,
Options: metadata.DefaultOptions,
}
if policyVersion != 0 {
config.Options.PolicyVersion = policyVersion
}
if config.HashCosts, err = getHashingCosts(target); err != nil {
return err
}
log.Printf("Creating config at %q with %v\n", ConfigFileLocation, config)
return metadata.WriteConfig(config, configFile)
}
// getConfig returns the current configuration struct. Any fields not specified
// in the config file use the system defaults. An error is returned if the
// config file hasn't been setup with CreateConfigFile yet or the config
// contains invalid data.
func getConfig() (*metadata.Config, error) {
configFile, err := os.Open(ConfigFileLocation)
switch {
case os.IsNotExist(err):
return nil, &ErrNoConfigFile{ConfigFileLocation}
case err != nil:
return nil, err
}
defer configFile.Close()
log.Printf("Reading config from %q\n", ConfigFileLocation)
config, err := metadata.ReadConfig(configFile)
if err != nil {
return nil, &ErrBadConfigFile{ConfigFileLocation, err}
}
// Use system defaults if not specified
if config.Source == metadata.SourceType_default {
config.Source = metadata.DefaultSource
log.Printf("Falling back to source of %q", config.Source.String())
}
if config.Options.Padding == 0 {
config.Options.Padding = metadata.DefaultOptions.Padding
log.Printf("Falling back to padding of %d", config.Options.Padding)
}
if config.Options.Contents == metadata.EncryptionOptions_default {
config.Options.Contents = metadata.DefaultOptions.Contents
log.Printf("Falling back to contents mode of %q", config.Options.Contents)
}
if config.Options.Filenames == metadata.EncryptionOptions_default {
config.Options.Filenames = metadata.DefaultOptions.Filenames
log.Printf("Falling back to filenames mode of %q", config.Options.Filenames)
}
if config.Options.PolicyVersion == 0 {
config.Options.PolicyVersion = metadata.DefaultOptions.PolicyVersion
log.Printf("Falling back to policy version of %d", config.Options.PolicyVersion)
}
if err := config.CheckValidity(); err != nil {
return nil, &ErrBadConfigFile{ConfigFileLocation, err}
}
return config, nil
}
// getHashingCosts returns hashing costs so that hashing a password will take
// approximately the target time. This is done using the total amount of RAM,
// the number of CPUs present, and by running the passphrase hash many times.
func getHashingCosts(target time.Duration) (*metadata.HashingCosts, error) {
log.Printf("Finding hashing costs that take %v\n", target)
// Start out with the minimal possible costs that use all the CPUs.
nCPUs := int64(runtime.NumCPU())
costs := &metadata.HashingCosts{
Time: 1,
Memory: 8 * nCPUs,
Parallelism: nCPUs,
}
// If even the minimal costs are not fast enough, just return the
// minimal costs and log a warning.
t, err := timeHashingCosts(costs)
if err != nil {
return nil, err
}
log.Printf("Min Costs={%v}\t-> %v\n", costs, t)
if t > target {
log.Printf("time exceeded the target of %v.\n", target)
return costs, nil
}
// Now we start doubling the costs until we reach the target.
memoryKiBLimit := memoryBytesLimit() / 1024
for {
// Store a copy of the previous costs
costsPrev := *costs
tPrev := t
// Double the memory up to the max, then double the time.
if costs.Memory < memoryKiBLimit {
costs.Memory = util.MinInt64(2*costs.Memory, memoryKiBLimit)
} else {
costs.Time *= 2
}
// If our hashing failed, return the last good set of costs.
if t, err = timeHashingCosts(costs); err != nil {
log.Printf("Hashing with costs={%v} failed: %v\n", costs, err)
return &costsPrev, nil
}
log.Printf("Costs={%v}\t-> %v\n", costs, t)
// If we have reached the target time, we return a set of costs
// based on the linear interpolation between the last two times.
if t >= target {
f := float64(target-tPrev) / float64(t-tPrev)
return &metadata.HashingCosts{
Time: betweenCosts(costsPrev.Time, costs.Time, f),
Memory: betweenCosts(costsPrev.Memory, costs.Memory, f),
Parallelism: costs.Parallelism,
}, nil
}
}
}
// memoryBytesLimit returns the maximum amount of memory we will use for
// passphrase hashing. This will never be more than a reasonable maximum (for
// compatibility) or an 8th the available system RAM.
func memoryBytesLimit() int64 {
// The sysinfo syscall only fails if given a bad address
var info unix.Sysinfo_t
err := unix.Sysinfo(&info)
util.NeverError(err)
totalRAMBytes := int64(info.Totalram)
return util.MinInt64(totalRAMBytes/8, maxMemoryBytes)
}
// betweenCosts returns a cost between a and b. Specifically, it returns the
// floor of a + f*(b-a). This way, f=0 returns a and f=1 returns b.
func betweenCosts(a, b int64, f float64) int64 {
return a + int64(f*float64(b-a))
}
// timeHashingCosts runs the passphrase hash with the specified costs and
// returns the time it takes to hash the passphrase.
func timeHashingCosts(costs *metadata.HashingCosts) (time.Duration, error) {
passphrase, err := crypto.NewKeyFromReader(bytes.NewReader(timingPassphrase))
if err != nil {
return 0, err
}
defer passphrase.Wipe()
// Be sure to measure CPU time, not wall time (time.Now)
begin := cpuTimeInNanoseconds()
hash, err := crypto.PassphraseHash(passphrase, timingSalt, costs)
if err == nil {
hash.Wipe()
}
end := cpuTimeInNanoseconds()
// This uses a lot of memory, run the garbage collector
runtime.GC()
return time.Duration((end - begin) / costs.Parallelism), nil
}
// cpuTimeInNanoseconds returns the nanosecond count based on the process's CPU usage.
// This number has no absolute meaning, only relative meaning to other calls.
func cpuTimeInNanoseconds() int64 {
var ts unix.Timespec
err := unix.ClockGettime(unix.CLOCK_PROCESS_CPUTIME_ID, &ts)
// ClockGettime fails if given a bad address or on a VERY old system.
util.NeverError(err)
return unix.TimespecToNsec(ts)
}