Jeffrey Paul 3 months ago
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commit
4a6469b003
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      README.md

105
README.md

@ -4,17 +4,17 @@ Manifest file generator and checker.
# 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
* 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
* 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 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
- 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
# Proposed Solution
@ -24,76 +24,78 @@ 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.
* 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
* 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
* 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?
- 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
- 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
- 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?
# 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
- 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
# 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
* 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)
- Manifest generation speed
- 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)
# Open Questions
* Should the manifest file include checksums of individual file chunks, or just for the whole assembled file?
* If so, should the chunksize be fixed or dynamic?
- Should the manifest file include checksums of individual file chunks, or just for the whole assembled file?
- If so, should the chunksize be fixed or dynamic?
* Should the manifest signature format be GnuPG signatures, or those from
- Should the manifest signature format be GnuPG signatures, or those from
OpenBSD's signify (of which there is a good [golang
implementation](https://github.com/frankbraun/gosignify)?
* Should the on-disk serialization format be proto3 or json?
- Should the on-disk serialization format be proto3 or json?
# Tool Examples
* `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
* `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.
- `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
- `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.
# Implementation Plan
## Phase One:
* golang module for reusability/embedding
* golang module client providing `mfer` CLI
- golang module for reusability/embedding
- golang module client providing `mfer` CLI
## Phase Two:
* ES6 or TypeScript module for reusability/embedding
* ES6/TypeScript module client providing `mfer.js` CLI
- ES6 or TypeScript module for reusability/embedding
- ES6/TypeScript module client providing `mfer.js` CLI
# 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)
* `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
- `aria2c https://example.com/manifestdirectory/`
- (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
# Use Cases
@ -114,6 +116,7 @@ I use filesystems that don't include data checksums, and I would like a cryptogr
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.
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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