package osbx
Install
Dune Dependency
Authors
Maintainers
Sources
sha256=881813a2e61cb8c4349c1db5c746ac90e4e7b91c556ca6ba5a57c55e606afebe
md5=8e48a67646625702d039f07247b3d576
Description
A single file container/archive that can be reconstructed even after total loss of file system structures (from official SeqBox).
Published: 04 Nov 2017
README
ocaml-SeqBox
Implementation of SeqBox in OCaml
The original pharsing was "Port of SeqBox to OCaml", but since no direct porting/translation was actually done due to the differences between Python 3(implementation language of SeqBox) and OCaml, which also force the architecture and design of this software(ocaml-SeqBox) to be independently developed, thus this is only an implementation(not a port or translation) of SeqBox according to its technical specifications. This is mainly to address the different licenses being used(SeqBox was using AGPL 3.0 at the time of writing while this project uses 3-Clause BSD license).
Official SeqBox Repo - https://github.com/MarcoPon/SeqBox
Table of Contents
Created by gh-md-toc
Acknowledgement
I would like to thank Marco (author of the official SeqBox) for discussing and clarifying several aspects of his project, and providing me with test data.
I would like to thank Ming for his feedback on the documentation, UX design, and several other general aspects of this project. And also his help on testing the building and installation of osbx on macOS.
Getting started
Recordings
You can view the recordings here
Installation
Osbx 1.2.3 is available through OPAM.
opam install osbx
There are four modes/commands for osbx currently : encode, decode, rescue, show
You can consult the man pages of osbx itself and all the four commands via
osbx --help
osbx encode --help
osbx decode --help
osbx rescue --help
osbx show --help
Notes
Version 1.2.4 is considered to be feature complete and mature enough for production use, but any bug reports or suggestions are very welcome - just open an issue!
Contributions are welcome as well, but note that by submitting a contribution, you agree that your code will be licensed under the 3-Clause BSD license.
No major active development will occur, but since 1.2.4 was designed to be quite scriptable via the options, you can always write helper scripts for advanced features. You can check out the ones I am writing here.
CRC-CCITT is currently implemented in pure OCaml and is translated from the implementation in libcrc
See src/crcccitt.ml, src/crcccitt.mli for the OCaml implementation
The translated source code is under the same MIT license used by and stated in libcrc source code
See libcrc_crcccitt/crcccitt.c, libcrc_crcccitt/checksum.h for the source code from libcrc used for the translation
Exact behaviours in non-standard cases are not specified in official SeqBox technical specification
See specification of ocaml-SeqBox for details on how ocaml-SeqBox behaves(if you care about undefined behaviour those sort of things)
Hashing libraries
Nocrypto for SHA1, SHA256, SHA512
Digestif for BLAKE2B_512
Tips
See wiki page
Gotchas
See wiki page
Helpers
See helpers
Links
Possibly useful additional features of ocaml-SeqBox(possibly not yet in official SeqBox)
Allows random ordering in sbx container
This also means block corruption will not stop the decoding process
Allows duplicate metadata/data blocks to exist within one sbx container
This means you can concatenate multiple copies of sbx container together directly to increase chance of recovery in case of corruption
Technical Specification
The following specification is copied directly from the official specification (with possible slight modifications).
Also see section "Features currently NOT planned to be implemented" for features ocaml-SeqBox is probably not going to have.
Byte order: Big Endian
Common blocks header:
| pos | to pos | size | desc |
|---|---|---|---|
| 0 | 2 | 3 | Recoverable Block signature = 'SBx' |
| 3 | 3 | 1 | Version byte |
| 4 | 5 | 2 | CRC-16-CCITT of the rest of the block (Version is used as starting value) |
| 6 | 11 | 6 | file UID |
| 12 | 15 | 4 | Block sequence number |
Block 0
| pos | to pos | size | desc |
|---|---|---|---|
| 16 | n | var | encoded metadata |
| n+1 | blockend | var | padding (0x1a) |
Blocks > 0 & < last:
| pos | to pos | size | desc |
|---|---|---|---|
| 16 | blockend | var | data |
Blocks == last:
| pos | to pos | size | desc |
|---|---|---|---|
| 16 | n | var | data |
| n+1 | blockend | var | padding (0x1a) |
Versions:
N.B. Current versions differs only by blocksize.
| ver | blocksize | note |
|---|---|---|
| 1 | 512 | default |
| 2 | 128 | |
| 3 | 4096 |
Metadata encoding:
| Bytes | Field |
|---|---|
| 3 | ID |
| 1 | Len |
| n | Data |
IDs
| ID | Desc |
|---|---|
| FNM | filename (utf-8) |
| SNM | sbx filename (utf-8) |
| FSZ | filesize (8 bytes) |
| FDT | date & time (8 bytes, seconds since epoch) |
| SDT | sbx date & time (8 bytes) |
| HSH | crypto hash (using Multihash protocol) |
| PID | parent UID (not used at the moment) |
Supported crypto hashes since 1.1.0 are
SHA1
SHA256
SHA512
BLAKE2B_512
Features currently NOT planned to be implemented
Data hiding (XOR encoding/decoding in official seqbox)
Provides neither sufficiently strong encryption nor sufficient stealth for any serious attempt to hide/secure data
You should use the appropriate tools for encryption
License
The following files directly from libcrc are under the MIT License(see license text in each of the code files)
libcrc_crcccitt/crcccitt.c
libcrc_crcccitt/checksum.h
The following files translated from libcrc source code are under the same MIT License as used by libcrc and as stated in libcrc source code, the license text of the crcccitt.c is copied over to src/crcccitt.ml as well
src/crcccitt.ml
src/crcccitt.mli
The files in tests folder copied from official SeqBox are under its license, which is MIT as of time of writing
tests/SeqBox/*
All remaining files are distributed under the 3-Clause BSD license as stated in the LICENSE file