Danny Kim
125 lines
6.3 KiB
Markdown
125 lines
6.3 KiB
Markdown
# Memona signature plugin
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Opens a WebDAV server as a folder inside Memona and signs every Markdown file
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saved to it with an ENS name, writing `signer` and `signature` into the file's
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frontmatter so anyone can check who wrote it against the name's current ENSv2
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records. Signing comes from the
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[md-ens-signature](https://github.com/capsulizers/md-ens-signature) library.
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The plugin is a WASI component: it speaks no sockets of its own and makes every
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request through the host's HTTP interface, under the connection's permissions.
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It registers one provider, `signature`, for the `signed-webdav` scheme.
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## Connecting
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| Field | Key | Meaning |
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| --- | --- | --- |
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| Server address | `url` | The folder's address, for example `https://dav.example.com/files/` |
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| Username | `username` | Optional account name for HTTP basic authentication |
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| Password | `password` | Optional password, stored as a secret |
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| Signer name | `ensName` | The ENS name that signs, for example `laptop.alice.eth` |
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| Signing key | `privateKey` | The private key of the address that owns the name, stored as a secret |
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| Sepolia RPC address | `rpcUrl` | The endpoint used to check signers against ENS, by default `https://ethereum-sepolia-rpc.publicnode.com` |
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| Trusted parent name | `trustedParent` | Optional. Only signers that are this name or one of its subnames count, for example `team.eth` |
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The connection's allowed hosts must include the RPC address's host as well as
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the server's, or every check reads as Sepolia unreachable.
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Listing, reading, writing, creating directories, renaming and deleting behave
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as in the WebDAV plugin: reads and writes stream in pieces of at most 1 MiB,
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conditional writes use `If-Match` and `If-None-Match`, change polling is not
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supported, a rename never replaces an existing target, and a folder with
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contents is refused rather than removed whole.
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## Signing
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Saving a `.md` file holds it whole, up to 96 KiB, and writes it once finished,
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with `signer` and `signature` set in its frontmatter; every other file streams
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straight through. The signature is EIP-191 `personal_sign` over the signer name
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and the body's SHA-256, made with the configured key; other frontmatter and the
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body stay byte for byte. A key that is not 32 bytes of hex refuses the
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connection, and a `.md` file that is not UTF-8 refuses the save.
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## Verifying
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Reading a `.md` file checks its signature against ENSv2 on Sepolia and adds an
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`ens-verification` line to the frontmatter Memona receives, which Memona shows
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as a badge. The owner of the signer name comes from the Universal Resolver's
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`findOwner`, so a name its parent revoked stops counting at once.
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| Badge | Meaning |
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| --- | --- |
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| `Verified: bob.team.eth` | The name's current owner signed this exact body |
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| `Tampered: signed as bob.team.eth` | The body changed after signing, or another key signed it |
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| `Unauthorized: bob.team.eth is not registered` | The signature holds, but no one owns the name now: it was revoked or never granted |
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| `Unauthorized: bob.team.eth is not a member of team.eth` | The signer is outside the trusted parent name |
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| `Unsigned` | The file has no `signer` and `signature` |
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| `Not checked: Sepolia unreachable` | The RPC address did not answer, so nothing was decided |
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| `Not checked: file too large` | The file is over 40 KiB, too large to hash within one call |
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| Verified | Tampered |
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| --- | --- |
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|  |  |
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| Unauthorized | Unsigned |
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| --- | --- |
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|  |  |
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The line never reaches the server: a save drops it before signing, and one
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stored on the server is replaced, so a file cannot claim its own verdict.
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Verdicts are reused for 30 seconds per signed body, a failed lookup included,
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so an editor rereading a file does not flood the RPC. Stat, list and saves
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keep reporting the stored size and the server's etag, so `If-Match` works as
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before.
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Memona gives each call into a plugin a fixed instruction budget, which is where
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the size limits come from: checking hashes the body and recovers a key, so it
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covers files up to 40 KiB; a file up to 1 MiB is marked not checked, and a
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larger one streams through without a badge.
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## Building
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```sh
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rustup target add wasm32-wasip2
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cargo build --locked --release --target wasm32-wasip2
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cargo test --locked --lib
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```
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The component lands at
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`target/wasm32-wasip2/release/memona_plugin_signature.wasm`.
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`wit/filesystem.wit` is a copy of the canonical Memona filesystem contract, and
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`src/sdk.rs` generates the guest bindings from it, so this repository builds
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without a Memona checkout. Refresh the copy from `plugin_system/sdk/wit` in the
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[Memona repository](https://git.capsulizers.com/lead/memona) when the contract
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moves, and keep `apiVersion` in `manifest.json` in step.
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## Packaging for the plugin store
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A `.memona-plugin` package is a ZIP archive with the files at its root, never
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inside a directory:
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```sh
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cargo build --locked --release --target wasm32-wasip2
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cp target/wasm32-wasip2/release/memona_plugin_signature.wasm plugin.wasm
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zip memona-plugin-signature.memona-plugin \
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manifest.json plugin.wasm README.md LICENSE
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```
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`manifest.json` and `plugin.wasm` are required; `README.md` becomes the guide on
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the plugin's public page and `LICENSE` is shown beside it.
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## Attribution
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The WebDAV code in `src/lib.rs`, `src/dav.rs` and `src/sdk.rs` is copied from
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the MIT-licensed
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[Memona WebDAV plugin](https://git.capsulizers.com/commons/memona-plugin-webdav)
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at commit `3d69750`. That crate keeps its provider, reader and writer private
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and exports the component's entry points itself, so it cannot be wrapped as a
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dependency without forking it; the copy stays as close to the original as the
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signing hook allows, so fixes there carry over with a plain diff.
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