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swarm-matrix-ctl: mint the swarm's own appservice registration

Browse source 
The swarm gets an appservice identity of its own, separate from each hive's
`hyperhive` registration. `swarm-matrix-ctl appservice render` mints its
tokens inside the matrix container when they are absent and renders the
registration tuwunel loads; `appservice publish` writes its as_token to
`swarm/controller/swarm-controller/matrix/appservice-token`, the one kind no
hive's policy grants.

The homeserver calls move out of swarm-matrix-ctl into swarm-matrix-client,
with a `whoami`, so swarm-controller can mint agents' accounts through the
same pinned device id instead of a copy of them.
This commit is contained in:
atlas 2026-09-24 23:42:36 +02:00 • committed by mara
commit 89aff8d613
10 changed files with 523 additions and 23 deletions
Download patch file Download diff file Expand all files Collapse all files

11
Cargo.lock generated
View file

@ -4935,14 +4935,23 @@ dependencies = [
"swarm-queue-client",
]
[[package]]
name = "swarm-matrix-client"
version = "0.1.0"
dependencies = [
"anyhow",
"reqwest",
"serde_json",
]
[[package]]
name = "swarm-matrix-ctl"
version = "0.1.0"
dependencies = [
"anyhow",
"clap",
"reqwest",
"serde_json",
"swarm-matrix-client",
"swarm-secret-client",
"tokio",
"tracing",

2
Cargo.toml
View file

@ -27,6 +27,7 @@ members = [
"swarm-authelia-bridge",
"swarm-authelia-bridge-sock",
"swarm-controller",
"swarm-matrix-client",
"swarm-matrix-ctl",
"swarm-nats-auth",
"swarm-queue-client",
@ -101,6 +102,7 @@ hive-priv-sock = { path = "hive-priv-sock" }
hive-sock-client = { path = "hive-sock-client" }
hive-types = { path = "hive-types" }
swarm-authelia-bridge-sock = { path = "swarm-authelia-bridge-sock" }
swarm-matrix-client = { path = "swarm-matrix-client" }
swarm-queue-client = { path = "swarm-queue-client" }
swarm-secret-client = { path = "swarm-secret-client" }
thiserror = "2"

13
swarm-matrix-client/Cargo.toml Normal file
View file

@ -0,0 +1,13 @@
[package]
name = "swarm-matrix-client"
version.workspace = true
readme = "README.md"
edition.workspace = true
[dependencies]
anyhow.workspace = true
reqwest.workspace = true
serde_json.workspace = true
[lints]
workspace = true

17
swarm-matrix-client/README.md Normal file
View file

@ -0,0 +1,17 @@
# swarm-matrix-client
The appservice calls against the swarm's homeserver, shared by the two binaries
that make them: `swarm-matrix-ctl` (inside the matrix container, for a hive's
sender account) and `swarm-controller` (for each agent's account, with the
swarm's own appservice token).
Three calls, all client-server API: register an account as the appservice, log
in to an existing one as the appservice, and ask a token who it is. Both mints
pin the device id `hyperhive-<localpart>`, so a second login **replaces** that
device's token instead of adding a device.
## 🩸 A secret is a path, never a value
Every error here is built from the response's status and its `errcode`, never
its body: a successful `/register` or `/login` body is an access token, and an
error body is one malformed response away from being the same bytes.

117
swarm-matrix-ctl/src/homeserver.rs → swarm-matrix-client/src/lib.rs
View file

@ -1,4 +1,6 @@
//! The two calls the mint ladder is made of, against the homeserver next door.
//! The appservice calls against the swarm's homeserver: register, log in, and
//! ask a token who it is. Shared by `swarm-matrix-ctl` and `swarm-controller`;
//! see the README for why both mint through the same device id.
//!
//! 🩸 **Every error in this module is built from the response's `status` and
//! its `errcode`, never its body.** A successful `/register` or `/login` body
@ -8,8 +10,8 @@
use anyhow::{Context, Result, bail};
/// Client-server API calls are one round trip each against a homeserver in the
/// same netns; a slow one is a broken one.
/// Every call here is one client-server API round trip; a slow one is a broken
/// one.
const TIMEOUT_SECS: u64 = 10;
/// Bytes of the throwaway password `/register` is given.
@ -21,11 +23,11 @@ const PASSWORD_BYTES: usize = 32;
/// What the homeserver said about a registration attempt.
///
/// An enum rather than a string match on the error text: `M_USER_IN_USE` is the
/// *expected* answer here — the hive's `@hive-<hive>:` account is the appservice
/// registration's own `sender_localpart`, so the homeserver creates it at startup, before
/// anything gets to ask — and an expected answer should not have to be
/// recovered from a formatted message.
/// An enum rather than a string match on the error text: `M_USER_IN_USE` is an
/// *expected* answer — a registration's own `sender_localpart` is created by
/// the homeserver at startup, and an agent minted once before already exists —
/// and an expected answer should not have to be recovered from a formatted
/// message.
pub enum Registered {
/// A fresh account, and the access token minted with it.
Token(String),
@ -68,7 +70,7 @@ pub async fn register(
// request carries the as_token.
"type": "m.login.application_service",
"username": localpart,
"password": random_password()?,
"password": random_hex(PASSWORD_BYTES)?,
"device_id": device_id(localpart),
"initial_device_display_name": format!("hyperhive ({localpart})"),
"inhibit_login": false,
@ -140,6 +142,52 @@ pub async fn appservice_login(
access_token(&json)
}
/// What the homeserver says a token is.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Whoami {
/// A live token, and the full user id it authenticates as.
User(String),
/// `M_UNKNOWN_TOKEN`: the homeserver does not know this token, because a
/// later login on the same device replaced it or it was revoked.
UnknownToken,
}
/// Ask the homeserver who `token` is.
///
/// # Errors
/// When the request cannot be sent, the response will not decode, or the
/// homeserver refuses with anything other than `M_UNKNOWN_TOKEN`. That one is
/// [`Whoami::UnknownToken`], because it is a verdict about the token and the
/// rest are not.
pub async fn whoami(client: &reqwest::Client, base: &str, token: &str) -> Result<Whoami> {
let resp = client
.get(format!("{base}/_matrix/client/v3/account/whoami"))
.bearer_auth(token)
.send()
.await
.context("GET /account/whoami: sending the request")?;
let status = resp.status();
let json = resp
.json::<serde_json::Value>()
.await
.context("GET /account/whoami: decoding the response as JSON")?;
whoami_verdict(status, &json)
}
/// [`whoami`]'s reading of a response, apart from the IO.
fn whoami_verdict(status: reqwest::StatusCode, json: &serde_json::Value) -> Result<Whoami> {
if status.is_success() {
return json["user_id"]
.as_str()
.map(|u| Whoami::User(u.to_owned()))
.context("the homeserver's whoami response carried no `user_id`");
}
if errcode(json) == Some("M_UNKNOWN_TOKEN") {
return Ok(Whoami::UnknownToken);
}
bail!("the homeserver refused whoami: {}", why(status, json))
}
/// The device every token this binary mints is pinned to.
fn device_id(localpart: &str) -> String {
format!("hyperhive-{localpart}")
@ -195,18 +243,18 @@ fn why(status: reqwest::StatusCode, json: &serde_json::Value) -> String {
}
}
/// A throwaway password for [`register`], as hex.
/// `bytes` random bytes from `/dev/urandom`, as hex: [`register`]'s
/// throwaway password, and the appservice tokens `swarm-matrix-ctl` mints.
///
/// From `/dev/urandom` directly rather than through an RNG crate: this is the
/// one random value the binary needs, and the kernel is already the source any
/// such crate would reach for here.
/// From `/dev/urandom` directly rather than through an RNG crate: the kernel is
/// already the source any such crate would reach for here.
///
/// # Errors
/// When `/dev/urandom` cannot be read.
fn random_password() -> Result<String> {
pub fn random_hex(bytes: usize) -> Result<String> {
use std::io::Read as _;
let mut buf = [0u8; PASSWORD_BYTES];
let mut buf = vec![0u8; bytes];
std::fs::File::open("/dev/urandom")
.context("opening /dev/urandom")?
.read_exact(&mut buf)
@ -275,11 +323,48 @@ mod tests {
assert!(!format!("{e}").contains("@hive:t.local"), "{e}");
}
#[test]
fn whoami_reads_the_user_of_a_live_token() {
let json =
serde_json::json!({ "user_id": "@atlas:t.local", "device_id": "hyperhive-atlas" });
assert_eq!(
whoami_verdict(reqwest::StatusCode::OK, &json).expect("a live token"),
Whoami::User("@atlas:t.local".to_owned())
);
}
#[test]
fn a_replaced_token_is_a_verdict_and_not_an_error() {
// The arm a mint decides on: this is how a token some other login on
// the same device replaced looks.
let json = serde_json::json!({ "errcode": "M_UNKNOWN_TOKEN", "error": "Unknown token" });
assert_eq!(
whoami_verdict(reqwest::StatusCode::UNAUTHORIZED, &json).expect("a verdict"),
Whoami::UnknownToken
);
}
#[test]
fn any_other_refusal_is_an_error_so_nobody_mints_on_it() {
// The control for the arm above: a 401 with another code, or a 5xx,
// says nothing about the token, and a caller that minted on it would
// rotate every token during an outage.
for (status, json) in [
(
reqwest::StatusCode::UNAUTHORIZED,
serde_json::json!({ "errcode": "M_MISSING_TOKEN" }),
),
(reqwest::StatusCode::BAD_GATEWAY, serde_json::json!({})),
] {
assert!(whoami_verdict(status, &json).is_err(), "{status}");
}
}
#[test]
fn a_minted_password_is_hex_of_the_declared_length() {
// The control on the hex fold: a short or non-hex password would be
// accepted by the homeserver and only surface much later, if at all.
let pw = random_password().expect("/dev/urandom is readable");
let pw = random_hex(PASSWORD_BYTES).expect("/dev/urandom is readable");
assert_eq!(pw.len(), PASSWORD_BYTES * 2);
assert!(pw.bytes().all(|b| b.is_ascii_hexdigit()), "not hex");
}

4
swarm-matrix-ctl/Cargo.toml
View file

@ -14,8 +14,10 @@ anyhow.workspace = true
# single-purpose binary: the next thing that has to run in the matrix container
# is a subcommand here, not a new crate.
clap.workspace = true
reqwest.workspace = true
serde_json.workspace = true
# The appservice calls, shared with `swarm-controller`, which mints agents'
# accounts through the same device id.
swarm-matrix-client.workspace = true
# The agreement this binary is one end of: where the credential lives, what the
# object at that path holds, and the `BAO_*` spellings the unit sets.
swarm-secret-client.workspace = true

279
swarm-matrix-ctl/src/appservice.rs Normal file
View file

@ -0,0 +1,279 @@
//! `swarm-matrix-ctl appservice` — the **swarm's** own appservice
//! registration: minted here, loaded by the homeserver beside us, and published
//! to the one store path `swarm-controller` reads it from.
//!
//! Two verbs, because they have opposite failure rules:
//!
//! - [`render`] runs before tuwunel and touches nothing but this container's
//! state dir. tuwunel loads the file it writes through `LoadCredential`, and
//! a missing credential source fails the homeserver's start, so this half
//! must not be able to fail on a network.
//! - [`publish`] runs after it and needs the store. A sealed store delays it
//! and nothing else.
//!
//! "Only once": the token file in the state dir is the record. [`render`]
//! mints only when it is absent and re-renders from it every time; [`publish`]
//! writes the store only when the store's copy differs.
//!
//! This registration's sender is promoted to homeserver admin at boot
//! (`nix/host-modules/hive-matrix.nix`), which is why its token goes to
//! `swarm_secret_client::matrix::swarm_appservice_token_path` — a path no
//! hive's policy reaches — and to nowhere else.
use std::io::Write as _;
use std::os::unix::fs::OpenOptionsExt as _;
use std::path::{Path, PathBuf};
use anyhow::{Context, Result};
use swarm_secret_client::{
SecretStore,
client::{DEFAULT_CERT_MOUNT, Settings},
matrix,
};
use crate::registration;
/// This container's state dir for the registration and its two tokens.
const ENV_DIR: &str = "MATRIX_APPSERVICE_DIR";
/// The registration's `sender_localpart`: the account the homeserver creates
/// for it and the one `admin_execute` promotes.
const ENV_SENDER: &str = "MATRIX_APPSERVICE_SENDER";
/// The user namespace regex, rendered by nix beside the hive registration's.
const ENV_USER_REGEX: &str = "MATRIX_APPSERVICE_USER_REGEX";
/// Role on the store's `cert` auth mount that [`publish`] logs in with.
const ENV_CERT_ROLE: &str = "MATRIX_APPSERVICE_CERT_ROLE";
/// The registration's `id`. Distinct from the hive registration's
/// (`hyperhive`): tuwunel refuses two registrations with one id.
const ID: &str = "swarm";
/// File names inside [`ENV_DIR`]. `REGISTRATION` is what tuwunel loads.
const AS_TOKEN: &str = "as-token";
const HS_TOKEN: &str = "hs-token";
const REGISTRATION: &str = "swarm.yaml";
/// Random bytes per token, as the hive registration's renderer uses.
const TOKEN_BYTES: usize = 32;
/// Read a required variable.
fn required(get: &impl Fn(&str) -> Option<String>, var: &'static str) -> Result<String> {
get(var)
.filter(|v| !v.is_empty())
.with_context(|| format!("{var} is unset or empty"))
}
/// Mint the tokens if absent and render the registration from them.
///
/// # Errors
/// If a variable is missing, or the state dir cannot be read or written.
pub fn render() -> Result<()> {
let get = |k: &str| std::env::var(k).ok();
let dir = PathBuf::from(required(&get, ENV_DIR)?);
let sender = required(&get, ENV_SENDER)?;
let regex = required(&get, ENV_USER_REGEX)?;
render_into(&dir, &sender, &regex)?;
tracing::info!(path = %dir.join(REGISTRATION).display(), "rendered the swarm appservice registration");
Ok(())
}
/// [`render`] against an explicit directory, so a test can run it twice.
fn render_into(dir: &Path, sender: &str, regex: &str) -> Result<()> {
let as_token = existing_or_minted(&dir.join(AS_TOKEN))?;
let hs_token = existing_or_minted(&dir.join(HS_TOKEN))?;
write_secret(
&dir.join(REGISTRATION),
&registration_yaml(sender, regex, &as_token, &hs_token),
)
}
/// The token at `path`, minting and writing one first when there is none.
fn existing_or_minted(path: &Path) -> Result<String> {
match std::fs::read_to_string(path) {
Ok(t) if !t.trim().is_empty() => return Ok(t.trim().to_owned()),
Ok(_) => {}
Err(e) if e.kind() == std::io::ErrorKind::NotFound => {}
Err(e) => return Err(e).with_context(|| format!("reading {}", path.display())),
}
let token = swarm_matrix_client::random_hex(TOKEN_BYTES)?;
write_secret(path, &token)?;
tracing::info!(path = %path.display(), "minted a swarm appservice token");
Ok(token)
}
/// Write `contents` to `path` as a `0600` file, through a rename so a reader
/// never sees half of it.
fn write_secret(path: &Path, contents: &str) -> Result<()> {
let tmp = path.with_extension("tmp");
let _ = std::fs::remove_file(&tmp);
let mut f = std::fs::OpenOptions::new()
.write(true)
.create_new(true)
.mode(0o600)
.open(&tmp)
.with_context(|| format!("creating {}", tmp.display()))?;
f.write_all(contents.as_bytes())
.and_then(|()| f.sync_all())
.with_context(|| format!("writing {}", tmp.display()))?;
std::fs::rename(&tmp, path).with_context(|| format!("renaming onto {}", path.display()))
}
/// The registration, in the shape `hive-matrix.nix` renders the hive's.
///
/// `exclusive: false` for that file's reason: an exclusive namespace does not
/// widen what this appservice may do, it refuses everyone else — and the hive
/// registration covers the same names until it is retired.
fn registration_yaml(sender: &str, regex: &str, as_token: &str, hs_token: &str) -> String {
format!(
"id: {ID}\n\
url: null\n\
sender_localpart: {sender}\n\
rate_limited: false\n\
namespaces:\n \
users:\n \
- exclusive: false\n \
regex: '{regex}'\n \
aliases: []\n \
rooms: []\n\
as_token: {as_token}\n\
hs_token: {hs_token}\n"
)
}
/// Whether the store needs the local token written to it.
fn needs_publish(stored: Option<&matrix::Credential>, local: &str) -> bool {
stored.is_none_or(|c| c.value.trim() != local)
}
/// Write the rendered registration's `as_token` to the store, unless the store
/// already holds it.
///
/// # Errors
/// If a variable is missing, the registration has not been rendered, or the
/// store refuses the login, the read or the write.
pub async fn publish() -> Result<()> {
let get = |k: &str| std::env::var(k).ok();
let dir = PathBuf::from(required(&get, ENV_DIR)?);
let cert_role = required(&get, ENV_CERT_ROLE)?;
let registration = dir.join(REGISTRATION);
let local = registration::as_token(&registration.to_string_lossy())?;
let settings = Settings::from_env().context("reading the store's BAO_* environment")?;
let store = SecretStore::connect(&settings, &cert_role, DEFAULT_CERT_MOUNT)
.await
.with_context(|| {
format!("logging in to the swarm secret store as cert role {cert_role}")
})?;
let path = matrix::swarm_appservice_token_path()?;
let stored: Option<matrix::Credential> = store
.read_optional(&path)
.await
.with_context(|| format!("reading {path}"))?;
if !needs_publish(stored.as_ref(), &local) {
tracing::info!(%path, "the swarm appservice token is already published");
return Ok(());
}
store
.write(
&path,
&matrix::Credential {
value: local,
homeserver: None,
},
)
.await
.with_context(|| format!("writing the swarm appservice token to {path}"))?;
tracing::info!(%path, "published the swarm appservice token");
Ok(())
}
#[cfg(test)]
mod tests {
use super::*;
const REGEX: &str = "^@[a-z0-9._=/-]+:t\\.local$";
fn scratch() -> PathBuf {
let dir = std::env::temp_dir().join(format!(
"swarm-appservice-{}-{}",
std::process::id(),
std::time::SystemTime::now()
.duration_since(std::time::UNIX_EPOCH)
.expect("after the epoch")
.as_nanos()
));
std::fs::create_dir_all(&dir).expect("temp dir");
dir
}
#[test]
fn the_rendered_registration_carries_the_token_it_minted() {
let dir = scratch();
render_into(&dir, "swarm", REGEX).expect("renders");
let token = registration::as_token(&dir.join(REGISTRATION).to_string_lossy())
.expect("the as_token line parses");
assert_eq!(token.len(), TOKEN_BYTES * 2);
assert_eq!(
std::fs::read_to_string(dir.join(AS_TOKEN)).expect("minted"),
token
);
std::fs::remove_dir_all(&dir).ok();
}
#[test]
fn a_second_render_keeps_the_token() {
// "Only once": a re-mint on every boot would hand the controller a
// token the homeserver no longer loads until publish catches up.
let dir = scratch();
render_into(&dir, "swarm", REGEX).expect("first");
let first = std::fs::read_to_string(dir.join(REGISTRATION)).expect("rendered");
render_into(&dir, "swarm", REGEX).expect("second");
let second = std::fs::read_to_string(dir.join(REGISTRATION)).expect("rendered");
assert_eq!(first, second);
std::fs::remove_dir_all(&dir).ok();
}
#[test]
fn the_registration_is_the_swarms_and_not_the_hives() {
let y = registration_yaml("swarm", REGEX, "aa", "bb");
assert!(y.starts_with("id: swarm\n"), "{y}");
assert!(y.contains("\nsender_localpart: swarm\n"), "{y}");
assert!(y.contains("\n - exclusive: false\n"), "{y}");
assert!(y.contains(&format!("regex: '{REGEX}'")), "{y}");
assert!(y.contains("\nurl: null\n"), "{y}");
}
#[test]
fn the_registration_and_tokens_are_owner_only() {
use std::os::unix::fs::PermissionsExt as _;
let dir = scratch();
render_into(&dir, "swarm", REGEX).expect("renders");
for f in [AS_TOKEN, HS_TOKEN, REGISTRATION] {
let mode = std::fs::metadata(dir.join(f))
.expect("exists")
.permissions()
.mode();
assert_eq!(mode & 0o777, 0o600, "{f}");
}
std::fs::remove_dir_all(&dir).ok();
}
#[test]
fn publish_writes_only_what_the_store_lacks() {
let same = matrix::Credential {
value: "aa".to_owned(),
homeserver: None,
};
assert!(!needs_publish(Some(&same), "aa"));
assert!(needs_publish(None, "aa"));
let other = matrix::Credential {
value: "bb".to_owned(),
homeserver: None,
};
assert!(needs_publish(Some(&other), "aa"));
}
#[test]
fn every_variable_is_scoped_to_the_verb() {
for var in [ENV_DIR, ENV_SENDER, ENV_USER_REGEX, ENV_CERT_ROLE] {
assert!(var.starts_with("MATRIX_APPSERVICE_"), "{var}");
}
}
}

44
swarm-matrix-ctl/src/main.rs
View file

@ -7,18 +7,19 @@
//! identity plumbing to add one action, so the next thing that has to run in
//! here is a verb below, not a new crate.
//!
//! Today that is one verb, [`mint`]: publish the appservice sender account's
//! homeserver access token to the swarm's secret store, once.
//! [`mint`] publishes a hive's appservice sender token to the swarm's secret
//! store, once. [`appservice`] mints the **swarm's** own appservice
//! registration and publishes its token for `swarm-controller`.
//!
//! It lives in the container because the appservice `as_token` that authorises
//! the mint is *already* there — the registration tuwunel loads is bind-mounted
//! in — so no second holder of that secret is created.
//!
//! 🩸 **A secret is a path, never a value.** The only identifier any verb here
//! logs is the store path; see `homeserver`'s module doc for the same rule
//! logs is the store path; see `swarm_matrix_client`'s module doc for the same rule
//! applied to error messages.
mod homeserver;
mod appservice;
mod mint;
mod registration;
@ -44,6 +45,20 @@ enum Command {
/// no flags, because a systemd `Environment=` block is what a nix module
/// can render and a command line full of paths is not.
Mint,
/// The swarm's own appservice registration, whose sender is the
/// homeserver's admin account. Configured by `MATRIX_APPSERVICE_*`.
#[command(subcommand)]
Appservice(Appservice),
}
#[derive(Debug, Subcommand)]
enum Appservice {
/// Mint the tokens when absent and render the registration tuwunel loads.
/// Local only: it runs before the homeserver and must not need a network.
Render,
/// Write the rendered `as_token` to the swarm secret store when the
/// store's copy differs.
Publish,
}
#[tokio::main]
@ -57,6 +72,8 @@ async fn main() -> Result<()> {
match Cli::parse().command {
Command::Mint => mint::run().await,
Command::Appservice(Appservice::Render) => appservice::render(),
Command::Appservice(Appservice::Publish) => appservice::publish().await,
}
}
@ -80,6 +97,25 @@ mod tests {
/// The control: without it the case above passes on a parser that accepts
/// anything.
/// The two units name these verbs, same reason as the test above.
#[test]
fn the_appservice_verbs_are_spelled_the_way_the_units_invoke_them() {
let cli =
Cli::try_parse_from(["swarm-matrix-ctl", "appservice", "render"]).expect("a verb");
assert!(matches!(
cli.command,
Command::Appservice(Appservice::Render)
));
let cli =
Cli::try_parse_from(["swarm-matrix-ctl", "appservice", "publish"]).expect("a verb");
assert!(matches!(
cli.command,
Command::Appservice(Appservice::Publish)
));
Cli::try_parse_from(["swarm-matrix-ctl", "appservice"])
.expect_err("a sub-verb is required");
}
#[test]
fn an_unknown_verb_is_refused() {
Cli::try_parse_from(["swarm-matrix-ctl", "conjure"])

4
swarm-matrix-ctl/src/mint.rs
View file

@ -21,7 +21,9 @@ use swarm_secret_client::{
matrix,
};
use crate::{homeserver, registration};
use swarm_matrix_client as homeserver;
use crate::registration;
/// Role on the store's `cert` auth mount to log in with. Its policy is what
/// allows the write below; the certificate the `BAO_*` variables name has to

55
swarm-secret-client/src/matrix.rs
View file

@ -93,6 +93,28 @@ pub fn appservice_token_path(hive: &str) -> Result<String, Error> {
Ok(format!("{prefix}/matrix/appservice-token"))
}
/// The name segment of the controller's own subtree, and the cert-auth role it
/// logs in under (`swarm-controller`'s `store::CERT_ROLE`).
const CONTROLLER: &str = "swarm-controller";
/// The path holding the **swarm's** appservice token: the one registration
/// on the swarm's homeserver that is not a hive's, whose sender is promoted
/// to homeserver admin at boot.
///
/// The matrix container mints it and publishes it here; `swarm-controller`
/// reads it to create agents' accounts. Under [`Kind::Controller`] because
/// that is the one kind [`crate::policy::render`] grants no hive: every hive
/// reads `agents/*`, its own `hives/<hive>/*` and `services/*`, so under any
/// of those this admin credential would be readable by every hive.
///
/// # Errors
/// Never in practice: the name segment is a constant. The `Result` is
/// [`principal_prefix`]'s.
pub fn swarm_appservice_token_path() -> Result<String, Error> {
let prefix = principal_prefix(Kind::Controller, CONTROLLER)?;
Ok(format!("{prefix}/matrix/appservice-token"))
}
/// What an account's path holds: the token, plus the homeserver it belongs to.
///
/// The homeserver rides with the token rather than on the queue notice that
@ -215,6 +237,39 @@ mod tests {
assert!(matches!(e, Error::PathSegment { kind: "hive", .. }), "{e}");
}
#[test]
fn the_swarm_appservice_token_lands_under_the_controller() {
assert_eq!(
swarm_appservice_token_path().expect("a constant segment"),
"swarm/controller/swarm-controller/matrix/appservice-token"
);
}
#[test]
fn no_hive_policy_reaches_the_swarm_appservice_token() {
// 🩸 The swarm's sender is a homeserver admin, so its token must not
// be under any stanza a hive's policy renders. Checked against the
// rendered document rather than against the prefix, because the
// document is what the store enforces.
let doc = crate::policy::render("pr1ma").expect("a plain name is legal");
// Every stanza is `path "secret/data/<prefix>*" { … }`.
let granted: Vec<&str> = doc
.lines()
.filter_map(|l| l.strip_prefix("path \"secret/data/"))
.filter_map(|p| p.strip_suffix("*\" {"))
.collect();
let reads = |path: &str| granted.iter().any(|g| path.starts_with(g));
let path = swarm_appservice_token_path().expect("a constant segment");
assert!(!reads(&path), "{path} is readable under {granted:?}");
// The control: an agent's account path IS under a hive stanza, so the
// assertion above can fail at all.
let agent = account_path("atlas", "main").expect("legal");
assert!(
reads(&agent),
"{agent} should be readable under {granted:?}"
);
}
#[test]
fn a_segment_cannot_escape_its_own_directory() {
// Each of these is a *different* way to address another agent's tree,