proxmox-backup/docs/file-formats.rst
2021-02-28 11:12:31 +01:00

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File Formats
============
.. _pxar-format:
Proxmox File Archive Format (``.pxar``)
---------------------------------------
.. graphviz:: pxar-format-overview.dot
.. _data-blob-format:
Data Blob Format
----------------
The data blob format is used to store small binary data. The magic number decides the exact format:
.. list-table::
:widths: auto
* - ``[66, 171, 56, 7, 190, 131, 112, 161]``
- unencrypted
- uncompressed
* - ``[49, 185, 88, 66, 111, 182, 163, 127]``
- unencrypted
- compressed
* - ``[123, 103, 133, 190, 34, 45, 76, 240]``
- encrypted
- uncompressed
* - ``[230, 89, 27, 191, 11, 191, 216, 11]``
- encrypted
- compressed
Compression algorithm is ``zstd``. Encryption cipher is ``AES_256_GCM``.
Unencrypted blobs use the following format:
.. list-table::
:widths: auto
* - ``MAGIC: [u8; 8]``
* - ``CRC32: [u8; 4]``
* - ``Data: (max 16MiB)``
Encrypted blobs additionally contains a 16 byte IV, followed by a 16
byte Authenticated Encyryption (AE) tag, followed by the encrypted
data:
.. list-table::
* - ``MAGIC: [u8; 8]``
* - ``CRC32: [u8; 4]``
* - ``ÌV: [u8; 16]``
* - ``TAG: [u8; 16]``
* - ``Data: (max 16MiB)``
.. _fixed-index-format:
Fixed Index Format
------------------
All numbers are stored as little-endian.
.. list-table::
* - ``MAGIC: [u8; 8]``
- ``[47, 127, 65, 237, 145, 253, 15, 205]``
* - ``uuid: [u8; 16]``,
- Unique ID
* - ``ctime: i64``,
- Creation Time (epoch)
* - ``index_csum: [u8; 32]``,
- Sha256 over the index (without header) ``SHA256(digest1||digest2||...)``
* - ``size: u64``,
- Image size
* - ``chunk_size: u64``,
- Chunk size
* - ``reserved: [u8; 4016]``,
- overall header size is one page (4096 bytes)
* - ``digest1: [u8; 32]``
- first chunk digest
* - ``digest2: [u8; 32]``
- next chunk
* - ...
- next chunk ...
.. _dynamic-index-format:
Dynamic Index Format
--------------------
All numbers are stored as little-endian.
.. list-table::
* - ``MAGIC: [u8; 8]``
- ``[28, 145, 78, 165, 25, 186, 179, 205]``
* - ``uuid: [u8; 16]``,
- Unique ID
* - ``ctime: i64``,
- Creation Time (epoch)
* - ``index_csum: [u8; 32]``,
- Sha256 over the index (without header) ``SHA256(offset1||digest1||offset2||digest2||...)``
* - ``reserved: [u8; 4032]``,
- Overall header size is one page (4096 bytes)
* - ``offset1: u64``
- End of first chunk
* - ``digest1: [u8; 32]``
- first chunk digest
* - ``offset2: u64``
- End of second chunk
* - ``digest2: [u8; 32]``
- second chunk digest
* - ...
- next chunk offset/digest