storj/pkg/encryption/path.go

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2019-01-24 20:15:10 +00:00
// Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.
package encryption
import (
"crypto/hmac"
"crypto/sha512"
"strings"
"github.com/zeebo/errs"
"storj.io/storj/pkg/paths"
"storj.io/storj/pkg/storj"
)
var (
emptyComponentPrefix = byte('\x01')
notEmptyComponentPrefix = byte('\x02')
emptyComponent = []byte{emptyComponentPrefix}
escapeSlash = byte('\x2e')
escapeFF = byte('\xfe')
escape01 = byte('\x01')
)
// EncryptPath encrypts the path using the provided cipher and looking up
// keys from the provided store and bucket.
func EncryptPath(bucket string, path paths.Unencrypted, cipher storj.CipherSuite, store *Store) (
encPath paths.Encrypted, err error) {
// Invalid paths map to invalid paths
if !path.Valid() {
return paths.Encrypted{}, nil
}
if cipher == storj.EncNull {
return paths.NewEncrypted(path.Raw()), nil
}
_, consumed, base := store.LookupUnencrypted(bucket, path)
if base == nil {
return paths.Encrypted{}, errs.New("unable to find encryption base for: %s/%q", bucket, path)
}
remaining, ok := path.Consume(consumed)
if !ok {
return paths.Encrypted{}, errs.New("unable to encrypt bucket path: %s/%q", bucket, path)
}
// if we didn't consume any path, we're at the root of the bucket, and so we have
// to fold the bucket name into the key.
key := &base.Key
if !consumed.Valid() {
key, err = derivePathKeyComponent(key, bucket)
if err != nil {
return paths.Encrypted{}, errs.Wrap(err)
}
}
encrypted, err := EncryptPathRaw(remaining.Raw(), cipher, key)
if err != nil {
return paths.Encrypted{}, errs.Wrap(err)
}
var builder strings.Builder
builder.WriteString(base.Encrypted.Raw())
if len(encrypted) > 0 {
if builder.Len() > 0 {
builder.WriteByte('/')
}
builder.WriteString(encrypted)
}
return paths.NewEncrypted(builder.String()), nil
}
// EncryptPathRaw encrypts the path using the provided key directly. EncryptPath should be
// preferred if possible.
func EncryptPathRaw(raw string, cipher storj.CipherSuite, key *storj.Key) (string, error) {
if cipher == storj.EncNull {
return raw, nil
}
var builder strings.Builder
for iter, i := paths.NewIterator(raw), 0; !iter.Done(); i++ {
component := iter.Next()
encComponent, err := encryptPathComponent(component, cipher, key)
if err != nil {
return "", errs.Wrap(err)
}
key, err = derivePathKeyComponent(key, component)
if err != nil {
return "", errs.Wrap(err)
}
if i > 0 {
builder.WriteByte('/')
}
builder.WriteString(encComponent)
}
return builder.String(), nil
}
// DecryptPath decrypts the path using the provided cipher and looking up
// keys from the provided store and bucket.
func DecryptPath(bucket string, path paths.Encrypted, cipher storj.CipherSuite, store *Store) (
unencPath paths.Unencrypted, err error) {
// Invalid paths map to invalid paths
if !path.Valid() {
return paths.Unencrypted{}, nil
}
if cipher == storj.EncNull {
return paths.NewUnencrypted(path.Raw()), nil
}
_, consumed, base := store.LookupEncrypted(bucket, path)
if base == nil {
return paths.Unencrypted{}, errs.New("unable to find decryption base for: %q", path)
}
remaining, ok := path.Consume(consumed)
if !ok {
return paths.Unencrypted{}, errs.New("unable to decrypt bucket path: %q", path)
}
// if we didn't consume any path, we're at the root of the bucket, and so we have
// to fold the bucket name into the key.
key := &base.Key
if !consumed.Valid() {
key, err = derivePathKeyComponent(key, bucket)
if err != nil {
return paths.Unencrypted{}, errs.Wrap(err)
}
}
decrypted, err := DecryptPathRaw(remaining.Raw(), cipher, key)
if err != nil {
return paths.Unencrypted{}, errs.Wrap(err)
}
var builder strings.Builder
builder.WriteString(base.Unencrypted.Raw())
if len(decrypted) > 0 {
if builder.Len() > 0 {
builder.WriteByte('/')
}
builder.WriteString(decrypted)
}
return paths.NewUnencrypted(builder.String()), nil
}
// DecryptPathRaw decrypts the path using the provided key directly. DecryptPath should be
// preferred if possible.
func DecryptPathRaw(raw string, cipher storj.CipherSuite, key *storj.Key) (string, error) {
if cipher == storj.EncNull {
return raw, nil
}
var builder strings.Builder
for iter, i := paths.NewIterator(raw), 0; !iter.Done(); i++ {
component := iter.Next()
unencComponent, err := decryptPathComponent(component, cipher, key)
if err != nil {
return "", errs.Wrap(err)
}
key, err = derivePathKeyComponent(key, unencComponent)
if err != nil {
return "", errs.Wrap(err)
}
if i > 0 {
builder.WriteByte('/')
}
builder.WriteString(unencComponent)
}
return builder.String(), nil
}
// DeriveContentKey returns the content key for the passed in path by looking up
// the appropriate base key from the store and bucket and deriving the rest.
func DeriveContentKey(bucket string, path paths.Unencrypted, store *Store) (key *storj.Key, err error) {
key, err = DerivePathKey(bucket, path, store)
if err != nil {
return nil, errs.Wrap(err)
}
key, err = DeriveKey(key, "content")
return key, errs.Wrap(err)
}
// DerivePathKey returns the path key for the passed in path by looking up the
// appropriate base key from the store and bucket and deriving the rest.
func DerivePathKey(bucket string, path paths.Unencrypted, store *Store) (key *storj.Key, err error) {
_, consumed, base := store.LookupUnencrypted(bucket, path)
if base == nil {
return nil, errs.New("unable to find encryption base for: %s/%q", bucket, path)
}
// If asking for the key at the bucket, do that and return.
if !path.Valid() {
key, err = derivePathKeyComponent(&base.Key, bucket)
if err != nil {
return nil, errs.Wrap(err)
}
return key, nil
}
remaining, ok := path.Consume(consumed)
if !ok {
return nil, errs.New("unable to derive path key for: %s/%q", bucket, path)
}
// if we didn't consume any path, we're at the root of the bucket, and so we have
// to fold the bucket name into the key.
key = &base.Key
if !consumed.Valid() {
key, err = derivePathKeyComponent(key, bucket)
if err != nil {
return nil, errs.Wrap(err)
}
}
for iter := remaining.Iterator(); !iter.Done(); {
key, err = derivePathKeyComponent(key, iter.Next())
if err != nil {
return nil, errs.Wrap(err)
}
}
return key, nil
}
// derivePathKeyComponent derives a new key from the provided one using the component. It
// should be preferred over DeriveKey when adding path components as it performs the
// necessary transformation to the component.
func derivePathKeyComponent(key *storj.Key, component string) (*storj.Key, error) {
return DeriveKey(key, "path:"+component)
}
// encryptPathComponent encrypts a single path component with the provided cipher and key.
func encryptPathComponent(comp string, cipher storj.CipherSuite, key *storj.Key) (string, error) {
// derive the key for the next path component. this is so that
// every encrypted component has a unique nonce.
derivedKey, err := derivePathKeyComponent(key, comp)
if err != nil {
return "", err
}
// use the derived key to derive the nonce
mac := hmac.New(sha512.New, derivedKey[:])
_, err = mac.Write([]byte("nonce"))
if err != nil {
return "", Error.Wrap(err)
}
nonce := new(storj.Nonce)
copy(nonce[:], mac.Sum(nil))
// encrypt the path components with the parent's key and the derived nonce
cipherText, err := Encrypt([]byte(comp), cipher, key, nonce)
if err != nil {
return "", Error.Wrap(err)
}
nonceSize := storj.NonceSize
if cipher == storj.EncAESGCM {
nonceSize = AESGCMNonceSize
}
// keep the nonce together with the cipher text
return string(encodeSegment(append(nonce[:nonceSize], cipherText...))), nil
}
// decryptPathComponent decrypts a single path component with the provided cipher and key.
func decryptPathComponent(comp string, cipher storj.CipherSuite, key *storj.Key) (string, error) {
if comp == "" {
return "", nil
}
data, err := decodeSegment([]byte(comp))
if err != nil {
return "", Error.Wrap(err)
}
nonceSize := storj.NonceSize
if cipher == storj.EncAESGCM {
nonceSize = AESGCMNonceSize
}
if len(data) < nonceSize || nonceSize < 0 {
return "", errs.New("component did not contain enough nonce bytes")
}
// extract the nonce from the cipher text
nonce := new(storj.Nonce)
copy(nonce[:], data[:nonceSize])
decrypted, err := Decrypt(data[nonceSize:], cipher, key, nonce)
if err != nil {
return "", Error.Wrap(err)
}
return string(decrypted), nil
}
// encodeSegment encodes segment according to specific rules
// The empty path component is encoded as `\x01`
// Any other path component is encoded as `\x02 + escape(component)`
//
// `\x2e` escapes to `\x2e\x01`
// `\x2f` escapes to `\x2e\x02`
// `\xfe` escapes to `\xfe\x01`
// `\xff` escapes to `\xfe\x02`
// `\x00` escapes to `\x01\x01`
// `\x01` escapes to `\x01\x02
// for more details see docs/design/path-component-encoding.md
func encodeSegment(segment []byte) []byte {
if len(segment) == 0 {
return emptyComponent
}
result := make([]byte, 0, len(segment)*2+1)
result = append(result, notEmptyComponentPrefix)
for i := 0; i < len(segment); i++ {
switch segment[i] {
case escapeSlash:
result = append(result, []byte{escapeSlash, 1}...)
case escapeSlash + 1:
result = append(result, []byte{escapeSlash, 2}...)
case escapeFF:
result = append(result, []byte{escapeFF, 1}...)
case escapeFF + 1:
result = append(result, []byte{escapeFF, 2}...)
case escape01 - 1:
result = append(result, []byte{escape01, 1}...)
case escape01:
result = append(result, []byte{escape01, 2}...)
default:
result = append(result, segment[i])
}
}
return result
}
func decodeSegment(segment []byte) ([]byte, error) {
err := validateEncodedSegment(segment)
if err != nil {
return []byte{}, err
}
if segment[0] == emptyComponentPrefix {
return []byte{}, nil
}
currentIndex := 0
for i := 1; i < len(segment); i++ {
switch {
case i == len(segment)-1:
segment[currentIndex] = segment[i]
case segment[i] == escapeSlash || segment[i] == escapeFF:
segment[currentIndex] = segment[i] + segment[i+1] - 1
i++
case segment[i] == escape01:
segment[currentIndex] = segment[i+1] - 1
i++
default:
segment[currentIndex] = segment[i]
}
currentIndex++
}
return segment[:currentIndex], nil
}
// validateEncodedSegment checks if:
// * The last byte/sequence is not in {escape1, escape2, escape3}
// * Any byte after an escape character is \x01 or \x02
// * It does not contain any characters in {\x00, \xff, \x2f}
// * It is non-empty
// * It begins with a character in {\x01, \x02}
func validateEncodedSegment(segment []byte) error {
switch {
case len(segment) == 0:
return errs.New("encoded segment cannot be empty")
case segment[0] != emptyComponentPrefix && segment[0] != notEmptyComponentPrefix:
return errs.New("invalid segment prefix")
case segment[0] == emptyComponentPrefix && len(segment) > 1:
return errs.New("segment encoded as empty but contains data")
case segment[0] == notEmptyComponentPrefix && len(segment) == 1:
return errs.New("segment encoded as not empty but doesn't contain data")
}
if len(segment) == 1 {
return nil
}
index := 1
for ; index < len(segment)-1; index++ {
if isEscapeByte(segment[index]) {
if segment[index+1] == 1 || segment[index+1] == 2 {
index++
continue
}
return errs.New("invalid escape sequence")
}
if isDisallowedByte(segment[index]) {
return errs.New("invalid character in segment")
}
}
if index == len(segment)-1 {
if isEscapeByte(segment[index]) {
return errs.New("invalid escape sequence")
}
if isDisallowedByte(segment[index]) {
return errs.New("invalid character")
}
}
return nil
}
func isEscapeByte(b byte) bool {
return b == escapeSlash || b == escapeFF || b == escape01
}
func isDisallowedByte(b byte) bool {
return b == 0 || b == '\xff' || b == '/'
}