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Jeffrey Paul 4 months ago
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README.md

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Manifest file generator and checker.
# Build Status
[![Build Status](https://drone.datavi.be/api/badges/sneak/mfer/status.svg)](https://drone.datavi.be/sneak/mfer)
# Problem Statement
Given a plain URL, there is no standard way to safely and programmatically download everything "under" that URL path. `wget -r` can traverse directory listings if they're enabled, but every server has a different format, and this does not verify cryptographic integrity of the files, or enable them to be fetched using a different protocol other than HTTP/s.
Given a plain URL, there is no standard way to safely and programmatically
download everything "under" that URL path. `wget -r` can traverse directory
listings if they're enabled, but every server has a different format, and
this does not verify cryptographic integrity of the files, or enable them to
be fetched using a different protocol other than HTTP/s.
Currently, the solution that people are using are sidecar files in the format of `SHASUMS` checksum files, as well as a `SHASUMS.asc` PGP detached signature. This is not checksum-algorithm-agnostic and the sidecar file is not always consistently named.
Currently, the solution that people are using are sidecar files in the
format of `SHASUMS` checksum files, as well as a `SHASUMS.asc` PGP detached
signature. This is not checksum-algorithm-agnostic and the sidecar file is
not always consistently named.
Real issues I face:
- when I plug in an ExFAT hard drive, I don't know if any files on the filesystem are corrupted or missing
- when I plug in an ExFAT hard drive, I don't know if any files on the
filesystem are corrupted or missing
- current ad-hoc solution are `SHASUMS`/`SHASUMS.asc` files
- when I want to mirror an HTTP archive, I have to use special tools like debmirror that understand the archive format
- when I want to mirror an HTTP archive, I have to use special tools like
debmirror that understand the archive format
- the debian repository metadata structure is hot garbage
- when I download a large file via HTTP, I have no way of knowing if the file content is what it's supposed to be
- when I download a large file via HTTP, I have no way of knowing if the
file content is what it's supposed to be
# Proposed Solution
@ -24,35 +38,50 @@ The manifest file would be called `index.mf`, and the tool for generating such w
The manifest file would do several important things:
- have a standard filename, so if given `https://example.com/downloadpackage/` one could fetch `https://example.com/downloadpackage/index.mf` to enumerate the full directory listing.
- have a standard filename, so if given
`https://example.com/downloadpackage/` one could fetch
`https://example.com/downloadpackage/index.mf` to enumerate the full
directory listing.
- contain a version field for extensibility
- contain structured data (protobuf, json, or cbor)
- provide an inner signed container, so that the manifest file itself can embed a signature and a public key alongside in a single file
- provide an inner signed container, so that the manifest file itself can
embed a signature and a public key alongside in a single file
- contain a list of files, each with a relative path to the manifest
- contain manifest timestamp
- contain ctime/mtime information for files so that file metadata can be preserved
- contain cryptographic checksums in several different algorithms for each file
- contain ctime/mtime information for files so that file metadata can be
preserved
- contain cryptographic checksums in several different algorithms for each
file
- probably encoded with multihash to indicate algo + hash
- sha256 at the minimum
- would be nice to include an IPFS/IPLD CIDv1 root hash for each file, which likely involves doing an ipfs file object chunking
- maybe even including the complete IPFS/IPLD directory tree objects and chunklists?
- this is because generating an `index.mf` does not imply publishing on ipfs at that time
- maybe a bittorrent chunklist for torrent client compatibility? perhaps a top-level infohash for the whole manifest?
- would be nice to include an IPFS/IPLD CIDv1 root hash for each file,
which likely involves doing an ipfs file object chunking
- maybe even including the complete IPFS/IPLD directory tree objects and
chunklists?
- this is because generating an `index.mf` does not imply publishing on
ipfs at that time
- maybe a bittorrent chunklist for torrent client compatibility? perhaps a
top-level infohash for the whole manifest?
# Design Goals
- Replace SHASUMS/SHASUMS.asc files
- be easy to download/resume a whole directory tree published via HTTP
- be easy to use across protocols (given an HTTPS url, fetch manifest, then download file contents via bittorrent or ipfs)
- not strongly coupled to HTTP use case, should not require special hosting, content types, or HTTP headers being sent
- be easy to use across protocols (given an HTTPS url, fetch manifest, then
download file contents via bittorrent or ipfs)
- not strongly coupled to HTTP use case, should not require special hosting,
content types, or HTTP headers being sent
# Non-Goals
- Manifest generation speed
- likely involves IPFS chunking, bittorrent chunking, and several different cryptographic hash functions over the entirety of each and every file
- likely involves IPFS chunking, bittorrent chunking, and several
different cryptographic hash functions over the entirety of each and
every file
- Small manifest file size (within reason)
- 30MiB files are "small" these days, given modern storage/bandwidth
- metadata size should not be used as an excuse to sacrifice utility (such as providing checksums over each chunk of a large file)
- metadata size should not be used as an excuse to sacrifice utility (such
as providing checksums over each chunk of a large file)
# Open Questions
@ -71,9 +100,12 @@ The manifest file would do several important things:
- `mfer gen` / `mfer gen .`
- recurses under current directory and writes out an `index.mf`
- `mfer check` / `mfer check .`
- verifies checksums of all files in manifest, displaying error and exiting nonzero if any files are missing or corrupted
- verifies checksums of all files in manifest, displaying error and
exiting nonzero if any files are missing or corrupted
- `mfer fetch https://example.com/stuff/`
- fetches `/stuff/index.mf` and downloads all files listed in manifest, optionally resuming any that already exist locally, and assures cryptographic integrity of downloaded files.
- fetches `/stuff/index.mf` and downloads all files listed in manifest,
optionally resuming any that already exist locally, and assures
cryptographic integrity of downloaded files.
# Implementation Plan
@ -90,33 +122,55 @@ The manifest file would do several important things:
# Hopes And Dreams
- `aria2c https://example.com/manifestdirectory/`
- (fetches `https://example.com/manifestdirectory/index.mf`, downloads and checksums all files, resumes any that exist locally already)
- (fetches `https://example.com/manifestdirectory/index.mf`, downloads and
checksums all files, resumes any that exist locally already)
- `mfer fetch https://example.com/manifestdirectory/`
- a command line option to zero/omit mtime/ctime, as well as manifest timestamp, and sort all directory listings so that manifest file generation is deterministic/reproducible
- URL format `mfer fetch https://exmaple.com/manifestdirectory/?key=5539AD00DE4C42F3AFE11575052443F4DF2A55C2` to assert in the URL which PGP signing key should be used in the manifest, so that shared URLs have a cryptographic trust root
- a "well-known" key in the manifest that maps well known keys (could reuse the http spec) to specific file paths in the manifest.
- example: a `berlin.sneak.app.slideshow` key that maps to a json slideshow config listing what image paths to show, and for how long, and in what order
- a command line option to zero/omit mtime/ctime, as well as manifest
timestamp, and sort all directory listings so that manifest file
generation is deterministic/reproducible
- URL format `mfer fetch
https://exmaple.com/manifestdirectory/?key=5539AD00DE4C42F3AFE11575052443F4DF2A55C2`
to assert in the URL which PGP signing key should be used in the manifest,
so that shared URLs have a cryptographic trust root
- a "well-known" key in the manifest that maps well known keys (could reuse
the http spec) to specific file paths in the manifest.
- example: a `berlin.sneak.app.slideshow` key that maps to a json
slideshow config listing what image paths to show, and for how long, and
in what order
# Use Cases
## Web Images
I'd like to be able to put a bunch of images into a directory, generate a manifest, and then point a slideshow client (such as an ambient display, or a react app with the target directory in a query string arg) at that statically hosted directory, and have it discover the full list of images available at that URL.
I'd like to be able to put a bunch of images into a directory, generate a
manifest, and then point a slideshow client (such as an ambient display, or
a react app with the target directory in a query string arg) at that
statically hosted directory, and have it discover the full list of images
available at that URL.
## Software Distribution
I'd like to be able to download a whole tree of files available via HTTP resumably by either HTTP or IPFS/BitTorrent without a .torrent file.
I'd like to be able to download a whole tree of files available via HTTP
resumably by either HTTP or IPFS/BitTorrent without a .torrent file.
## Filesystem Archive Integrity
I use filesystems that don't include data checksums, and I would like a cryptographically signed checksum file so that I can later verify that a set of archive files have not been modified, none are missing, and that the checksums have not been altered in storage by a second party.
I use filesystems that don't include data checksums, and I would like a
cryptographically signed checksum file so that I can later verify that a set
of archive files have not been modified, none are missing, and that the
checksums have not been altered in storage by a second party.
## Filesystem-Independent Checksums
I would like to be able to plug in a hard drive or flash drive and, if there is an `index.mf` in the root, automatically detect missing/corrupted files, regardless of filesystem format.
I would like to be able to plug in a hard drive or flash drive and, if there
is an `index.mf` in the root, automatically detect missing/corrupted files,
regardless of filesystem format.
# Collaboration
Please email [`sneak@sneak.berlin`](mailto:sneak@sneak.berlin) with your desired username for an account on this Gitea instance.
Please email [`sneak@sneak.berlin`](mailto:sneak@sneak.berlin) with your
desired username for an account on this Gitea instance.
I am currently interested in hiring a contractor skilled with the Go standard library interfaces to specify this tool in full and develop a prototype implementation.
I am currently interested in hiring a contractor skilled with the Go
standard library interfaces to specify this tool in full and develop a
prototype implementation.

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