libgocryptfs/README.md

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==============
An encrypted overlay filesystem written in Go.
Official website: https://nuetzlich.net/gocryptfs

gocryptfs is built on top the excellent
[go-fuse](https://github.com/hanwen/go-fuse) FUSE library and its
LoopbackFileSystem API.

This project was inspired by EncFS and strives to fix its security
issues while providing good performance
([benchmarks](https://nuetzlich.net/gocryptfs/comparison/#performance)).

For details on the security of gocryptfs see the
[Security](https://nuetzlich.net/gocryptfs/security/) design document.

All tags from v0.4 onward are signed by the *gocryptfs signing key*.
Please check [Signed Releases](https://nuetzlich.net/gocryptfs/releases/) for
details.

Current Status
--------------

gocryptfs is a young project. While bugs in any software can cause issues,
bugs in encryption software can cause catastrophic data loss. Keep a backup
of your gocryptfs filesystem *and* store a copy of your master key (printed
on mount) in a safe place. See below for how gocryptfs is tested.

Only Linux is supported at the moment. [Help wanted for a Mac OS X port.](https://github.com/rfjakob/gocryptfs/issues/15)

Testing
-------

gocryptfs comes with is own test suite that is constantly expanded as features are
added. Run it using `./test.bash`. It takes about 1 minute and requires FUSE
as it mounts several test filesystems.

The `stress_tests` directory contains stress tests that run indefinitely.

In addition, I have ported `xfstests` to FUSE, the result is the
[fuse-xfstests](https://github.com/rfjakob/fuse-xfstests) project. gocryptfs
passes the "generic" tests with one exception, results:  [XFSTESTS.md](Documentation/XFSTESTS.md)

A lot of work has gone into this. The testing has found bugs in gocryptfs
as well as in the go-fuse library.

Compile
-------

	$ go get github.com/rfjakob/gocryptfs

Use
---

	$ mkdir cipher plain
	$ $GOPATH/bin/gocryptfs -init cipher
	$ $GOPATH/bin/gocryptfs cipher plain

See the [Quickstart](https://nuetzlich.net/gocryptfs/quickstart/) page for more info.

The [MANPAGE.md](Documentation/MANPAGE.md) containes a description of available command-line options.
If you already have gocryptfs installed, run `./MANPAGE-render.bash` to bring up the rendered manpage in
your man pager (requires pandoc).

Storage Overhead
----------------

* Empty files take 0 bytes on disk
* 18 byte file header for non-empty files (2 bytes version, 16 bytes random file id)
* 28 bytes of storage overhead per 4kB block (12 byte nonce, 16 bytes auth tag)

[file-format.md](Documentation/file-format.md) contains a more detailed description.

Performance
-----------

Since version 0.7.2, gocryptfs is as fast as EncFS in the default mode,
and significantly faster than EncFS' "paranoia" mode that provides
a security level comparable to gocryptfs.

gocryptfs uses OpenSSL through a thin wrapper called `stupidgcm`.
This provides a 4x speedup compared to Go's builtin AES-GCM
implementation - see [openssl-gcm.md](Documentation/openssl-gcm.md)
for details. The use of openssl can disabled on the command-line.

Run `./benchmark.bash` to run gocryptfs' canonical set of
benchmarks that include streaming write, extracting a linux kernel
tarball, recursively listing and finally deleting it. The output will
look like this:

```
$ ./benchmark.bash
linux-3.0.tar.gz       100%[==========================>]  92,20M  2,96MB/s    in 35s
2016-05-04 19:29:20 URL:https://www.kernel.org/pub/linux/kernel/v3.0/linux-3.0.tar.gz
WRITE: 131072000 bytes (131 MB) copied, 1,43137 s, 91,6 MB/s
UNTAR: 23.25
LS:    1.75
RM:    4.42
```

Changelog
---------

v0.11, 2016-06-07
* Deprecate filesystems created by v0.6 and older
 * Filesystems can still be mounted but a warning is printed
 * See https://github.com/rfjakob/gocryptfs/issues/29 for details and
   join the discussion
* Add rsync stress test "pingpong-rsync.bash"
** Fix chown and utimens failures that caused rsync to complain

v0.10, 2016-05-30
* **Replace `spacemonkeygo/openssl` with `stupidgcm`**
 * gocryptfs now has its own thin wrapper to OpenSSL's GCM implementation
   called `stupidgcm`.
 * This should fix the [compile issues](https://github.com/rfjakob/gocryptfs/issues/21)
   people are seeing with `spacemonkeygo/openssl`. It also gets us
   a 20% performance boost for streaming writes.
* **Automatically choose between OpenSSL and Go crypto** [issue #23](https://github.com/rfjakob/gocryptfs/issues/23)
 * Go 1.6 added an optimized GCM implementation in amd64 assembly that uses AES-NI.
   This is faster than OpenSSL and is used if available. In all other
   cases OpenSSL is much faster and is used instead.
 * `-openssl=auto` is the new default
 * Passing `-openssl=true/false` overrides the autodetection.
* Warn but continue anyway if fallocate(2) is not supported by the
  underlying filesystem, see [issue #22](https://github.com/rfjakob/gocryptfs/issues/22)
 * Enables to use gocryptfs on ZFS and ext3, albeit with reduced out-of-space safety.
* [Fix statfs](https://github.com/rfjakob/gocryptfs/pull/27), by @lxp
* Fix a fsstress [failure](https://github.com/hanwen/go-fuse/issues/106)
  in the go-fuse library.

v0.9, 2016-04-10
* **Long file name support**
 * gocryptfs now supports file names up to 255 characters.
 * This is a forwards-compatible change. gocryptfs v0.9 can mount filesystems
   created by earlier versions but not the other way round.
* Refactor gocryptfs into multiple "internal" packages
* New command-line options:
 * `-longnames`: Enable long file name support (default true)
 * `-nosyslog`: Print messages to stdout and stderr instead of syslog (default false)
 * `-wpanic`: Make warning messages fatal (used for testing)
 * `-d`: Alias for `-debug`
 * `-q`: Alias for `-quiet`

v0.8, 2016-01-23
* Redirect output to syslog when running in the background
* New command-line option:
 * `-memprofile`: Write a memory allocation debugging profile the specified
   file

v0.7.2, 2016-01-19
* **Fix performance issue in small file creation**
 * This brings performance on-par with EncFS paranoia mode, with streaming writes
   significantly faster
 * The actual [fix](https://github.com/hanwen/go-fuse/commit/c4b6b7949716d13eec856baffc7b7941ae21778c)
   is in the go-fuse library. There are no code changes in gocryptfs.

v0.7.1, 2016-01-09
* Make the `build.bash` script compatible with Go 1.3
* Disable fallocate on OSX (system call not availabe)
* Introduce pre-built binaries for Fedora 23 and Debian 8

v0.7, 2015-12-20
* **Extend GCM IV size to 128 bit from Go's default of 96 bit**
 * This pushes back the birthday bound to make IV collisions virtually
   impossible
 * This is a forwards-compatible change. gocryptfs v0.7 can mount filesystems
   created by earlier versions but not the other way round.
* New command-line option:
 * `-gcmiv128`: Use 128-bit GCM IVs (default true)

v0.6, 2015-12-08
* **Wide-block filename encryption using EME + DirIV**
 * EME (ECB-Mix-ECB) provides even better security than CBC as it fixes
   the prefix leak. The used Go EME implementation is
   https://github.com/rfjakob/eme which is, as far as I know, the first
   implementation of EME in Go.
 * This is a forwards-compatible change. gocryptfs v0.6 can mount filesystems
   created by earlier versions but not the other way round.
* New command-line option:
 * `-emenames`: Enable EME filename encryption (default true)

v0.5.1, 2015-12-06
* Fix a rename regression caused by DirIV and add test case
* Use fallocate to guard against out-of-space errors

v0.5, 2015-12-04
* **Stronger filename encryption: DirIV**
 * Each directory gets a random 128 bit file name IV on creation,
   stored in `gocryptfs.diriv`
 * This makes it impossible to identify identically-named files across
   directories
 * A single-entry IV cache brings the performance cost of DirIV close to
   zero for common operations (see performance.txt)
 * This is a forwards-compatible change. gocryptfs v0.5 can mount filesystems
   created by earlier versions but not the other way round.
* New command-line option:
 * `-diriv`: Use the new per-directory IV file name encryption (default true)
 * `-scryptn`: allows to set the scrypt cost parameter N. This option
   can be used for faster mounting at the cost of lower brute-force
   resistance. It was mainly added to speed up the automated tests.

v0.4, 2015-11-15
* New command-line options:
 * `-plaintextnames`: disables filename encryption, added on user request
 * `-extpass`: calls an external program for prompting for the password
 * `-config`: allows to specify a custom gocryptfs.conf path
* Add `FeatureFlags` gocryptfs.conf paramter
 * This is a config format change, hence the on-disk format is incremented
 * Used for ext4-style filesystem feature flags. This should help avoid future
   format changes. The first user is `-plaintextnames`.
* On-disk format 2

v0.3, 2015-11-01
* **Add a random 128 bit file header to authenticate file->block ownership**
 * This is an on-disk-format change
* On-disk format 1

v0.2, 2015-10-11
* Replace bash daemonization wrapper with native Go implementation
* Better user feedback on mount failures

v0.1, 2015-10-07
* First release
* On-disk format 0