One window, the app's own page; the server through /api/v2

The two webviews (local title bar, remote web UI) become one WebviewWindow on
ui/index.html. The window refuses every navigation but the app's page and its
sealed frames; the capability still names only main and no remote URL.

- server.rs: discovery refuses a server older than 2.0 (protocol 3 and major
  version 2) and an app API newer than this app knows; the app's own device
  login for the app scope, the token kept in account.json (0600) and never
  given to the page; a proxy limited to /api/v2 paths; the SSE stream.
- files.rs: list and read the agent's working directory, resolved (links and
  .. included) and refused outside the agent's folders.
- sealed.rs: HTML for the viewer on its own scheme under the server's sealed
  policy: no bridge, no network, no navigation.
- watch.rs + tauri-plugin-notification: a notification when a reply or an
  agent chat finishes out of sight.
- A failed start and panics go to desktop.log; a missing tray no longer stops
  the app; the DMA-BUF renderer is off under NVIDIA's driver.
- The unstable multiwebview feature, the gtk dependency and the theme report
  are gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
HomerandClaude Opus 5.5 committed 2026-10-28 04:55:03 +00:00
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//! The server this app is a front end to: whether it is one this app can talk to, the app's own
//! sign-in to it, and every request the app's pages make to it.
//!
//! - **Discovery** (`/.well-known/lembas.json`) decides first. LLeMbas Desktop 1.0 needs a
//! LLeMbas 2.0 server: one that speaks link protocol 3 and has the app's door (`/api/v2`) in a
//! version this app knows. An older server is refused with a sentence that says which side to
//! update, before anything is signed in.
//! - **The app's sign-in** is the server's device login (RFC 8628), the same one `lembas login`
//! uses, for one scope: `app`, "read and write your chats, as the web interface does". The
//! approval page opens in the system's browser, where the person is signed in already. The
//! token is kept in the app's config directory, readable by this user only.
//! - **The token stays in Rust.** The pages ask for `/api/v2/...` through a command and get the
//! JSON back; they never hold the token, so no page -- and nothing a page shows -- can send it
//! anywhere. A request can only reach the server's `/api/v2`: the path is checked here.
//!
//! The agent's own link is a different token, the CLI's (`lembas login`), which this app never
//! reads: a token that may accept work as a device is not one the chat window needs.
use std::fs;
use std::io::{BufRead, BufReader, Write};
use std::path::{Path, PathBuf};
use std::sync::atomic::{AtomicBool, Ordering};
use std::time::{Duration, Instant};
use serde::{Deserialize, Serialize};
use serde_json::Value;
/// The link protocol a 2.0 server speaks (harness spec `acp.md`, *Versions*).
pub const NEEDS_PROTOCOL: i64 = 3;
/// The server's major version this app is written for.
pub const NEEDS_MAJOR: u64 = 2;
/// The `/api/v2` contract this app is written against: discovery's `app_api`. A higher number is
/// a change an existing client would misread, so this app says it is too old rather than guess.
pub const APP_API: i64 = 1;
/// What discovery said, once it has passed every check.
#[derive(Clone, Debug, Serialize, PartialEq)]
pub struct Discovery {
pub base: String,
pub name: String,
pub version: String,
/// The app's door: `https://host/api/v2`.
#[serde(skip)]
pub app: String,
#[serde(skip)]
pub device_code: String,
#[serde(skip)]
pub device_token: String,
}
fn agent(read: Duration) -> ureq::Agent {
ureq::AgentBuilder::new()
.timeout_connect(Duration::from_secs(10))
.timeout_read(read)
.timeout_write(Duration::from_secs(30))
.user_agent(&format!("llembas-desktop/{}", env!("CARGO_PKG_VERSION")))
.build()
}
/// An error a page can show and act on: the HTTP status (0: the server was not reached) and the
/// server's own sentence (`detail`), or ours.
#[derive(Clone, Debug, Serialize, PartialEq)]
pub struct ApiError {
pub status: u16,
pub detail: String,
}
impl ApiError {
pub fn new(status: u16, detail: impl Into<String>) -> Self {
ApiError {
status,
detail: detail.into(),
}
}
}
impl From<ureq::Error> for ApiError {
fn from(e: ureq::Error) -> Self {
match e {
ureq::Error::Status(code, res) => {
let text = res.into_string().unwrap_or_default();
let detail = serde_json::from_str::<Value>(&text)
.ok()
.and_then(|v| v.get("detail").cloned())
.map(|d| match d {
Value::String(s) => s,
other => other.to_string(),
})
.unwrap_or_else(|| format!("The server answered {code}."));
ApiError::new(code, detail)
}
ureq::Error::Transport(t) => {
ApiError::new(0, format!("Could not reach the server: {t}"))
}
}
}
}
/// Ask `base` who it is, and refuse what this app cannot talk to.
pub fn discover(base: &str) -> Result<Discovery, String> {
let url = format!("{base}/.well-known/lembas.json");
let res = agent(Duration::from_secs(15))
.get(&url)
.call()
.map_err(|e| match e {
ureq::Error::Status(404, _) => format!("{base} answers, but is not a LLeMbas server."),
ureq::Error::Status(code, _) => format!("{base} answered {code}."),
ureq::Error::Transport(t) => format!("Could not reach {base}: {t}"),
})?;
let body: Value = res
.into_json()
.map_err(|_| format!("{base} is not a LLeMbas server."))?;
check(&body, base)
}
/// The leading number of a version: `2` of `2.0.0-beta.1`, `1` of `1.7.3`.
fn major(version: &str) -> Option<u64> {
let digits: String = version
.trim_start_matches('v')
.chars()
.take_while(|c| c.is_ascii_digit())
.collect();
digits.parse().ok()
}
/// The checks, on discovery's answer: a LLeMbas server, a 2.0 one (protocol 3, version 2 or
/// later), with an app door whose version this app knows.
pub fn check(body: &Value, base: &str) -> Result<Discovery, String> {
if body.get("service").and_then(Value::as_str) != Some("lembas") {
return Err(format!("{base} is not a LLeMbas server."));
}
let version = body
.get("version")
.and_then(Value::as_str)
.unwrap_or("")
.to_string();
// `protocols` is a 2.0 server's list; a 1.x one has only `protocol`, frozen at 1.
let protocols: Vec<i64> = match body.get("protocols").and_then(Value::as_array) {
Some(list) => list.iter().filter_map(Value::as_i64).collect(),
None => body
.get("protocol")
.and_then(Value::as_i64)
.into_iter()
.collect(),
};
let new_enough =
protocols.contains(&NEEDS_PROTOCOL) && major(&version).is_some_and(|m| m >= NEEDS_MAJOR);
if !new_enough {
let runs = if version.is_empty() {
"an older LLeMbas".to_string()
} else {
format!("LLeMbas {version}")
};
return Err(format!(
"{base} runs {runs}. LLeMbas Desktop {} needs a LLeMbas 2.0 server or later: update the server, or keep using LLeMbas Desktop 0.7 with this one.",
env!("CARGO_PKG_VERSION")
));
}
let app_api = body.get("app_api").and_then(Value::as_i64).unwrap_or(0);
if app_api < 1 {
return Err(format!(
"{base} has no app interface (/api/v2). Update the server to LLeMbas 2.0 or later."
));
}
if app_api > APP_API {
return Err(format!(
"{base} speaks a newer app interface (version {app_api}) than LLeMbas Desktop {} knows (version {APP_API}). Update LLeMbas Desktop.",
env!("CARGO_PKG_VERSION")
));
}
let api = body.get("api");
let app = api
.and_then(|a| a.get("app"))
.and_then(Value::as_str)
.map(|s| s.trim_end_matches('/').to_string())
.unwrap_or_else(|| format!("{base}/api/v2"));
let device = body.get("login").and_then(|l| l.get("device"));
let endpoint = |key: &str| {
device
.and_then(|d| d.get(key))
.and_then(Value::as_str)
.map(String::from)
};
let (Some(device_code), Some(device_token)) = (endpoint("code"), endpoint("token")) else {
return Err(format!("{base} offers no device sign-in."));
};
Ok(Discovery {
base: base.to_string(),
name: body
.get("name")
.and_then(Value::as_str)
.unwrap_or("LLeMbas")
.to_string(),
version,
app,
device_code,
device_token,
})
}
// --- The app's sign-in ----------------------------------------------------------------------
/// What the app keeps of its sign-in: which server, the token, and whose it is.
#[derive(Clone, Debug, Default, Serialize, Deserialize, PartialEq)]
#[serde(default)]
pub struct Account {
pub server: String,
#[serde(skip_serializing_if = "String::is_empty")]
pub token: String,
pub email: String,
pub name: String,
}
impl Account {
/// The same account without its token: what a page may see.
pub fn public(&self) -> Account {
Account {
token: String::new(),
..self.clone()
}
}
}
fn account_file(config_dir: &Path) -> PathBuf {
config_dir.join("account.json")
}
/// The sign-in for `server`, if there is one (a sign-in to another server is not this one's).
pub fn load_account(config_dir: &Path, server: &str) -> Option<Account> {
let text = fs::read_to_string(account_file(config_dir)).ok()?;
let a: Account = serde_json::from_str(&text).ok()?;
(a.server == server && !a.token.is_empty()).then_some(a)
}
/// Written to a new file readable by this user only, then moved over the old one.
pub fn save_account(config_dir: &Path, a: &Account) -> std::io::Result<()> {
fs::create_dir_all(config_dir)?;
let tmp = config_dir.join("account.json.tmp");
let _ = fs::remove_file(&tmp);
let mut options = fs::OpenOptions::new();
options.write(true).create_new(true);
#[cfg(unix)]
{
use std::os::unix::fs::OpenOptionsExt;
options.mode(0o600);
}
let mut f = options.open(&tmp)?;
f.write_all((serde_json::to_string_pretty(a)? + "\n").as_bytes())?;
f.sync_all()?;
drop(f);
fs::rename(tmp, account_file(config_dir))
}
pub fn forget_account(config_dir: &Path) {
let _ = fs::remove_file(account_file(config_dir));
}
/// A device login in progress: the code to approve and where.
#[derive(Clone, Debug, Serialize)]
pub struct Code {
pub user_code: String,
pub verification_uri: String,
pub verification_uri_complete: String,
pub expires_in: u64,
#[serde(skip)]
pub interval: u64,
#[serde(skip)]
pub device_code: String,
}
/// Open a device login for the `app` scope.
pub fn start_sign_in(d: &Discovery, host: &str) -> Result<Code, String> {
let platform = format!("{}-{}", std::env::consts::OS, std::env::consts::ARCH);
let device_name = if host.is_empty() {
"LLeMbas Desktop".to_string()
} else {
format!("LLeMbas Desktop on {host}")
};
let res = agent(Duration::from_secs(15))
.post(&d.device_code)
.set("accept", "application/json")
.send_json(serde_json::json!({
"client_id": format!("llembas-desktop {}", env!("CARGO_PKG_VERSION")),
"device_name": device_name,
// No host on purpose: the host names the device an agent chat runs on, and that is
// the CLI's link, not this sign-in.
"device_platform": platform,
"scope": "app",
}))
.map_err(|e| oauth_error(e, "The server refused to start a sign-in"))?;
let v: Value = res
.into_json()
.map_err(|e| format!("The server's answer was not understood: {e}"))?;
let s = |k: &str| v.get(k).and_then(Value::as_str).unwrap_or("").to_string();
let n = |k: &str, or: u64| v.get(k).and_then(Value::as_u64).unwrap_or(or);
let code = Code {
user_code: s("user_code"),
verification_uri: s("verification_uri"),
verification_uri_complete: match s("verification_uri_complete") {
c if c.is_empty() => s("verification_uri"),
c => c,
},
expires_in: n("expires_in", 600),
interval: n("interval", 5).max(1),
device_code: s("device_code"),
};
if code.device_code.is_empty() || code.verification_uri.is_empty() {
return Err("The server's answer was not understood: no code.".into());
}
Ok(code)
}
/// RFC 8628's error, in words.
fn oauth_error(e: ureq::Error, what: &str) -> String {
match e {
ureq::Error::Status(code, res) => {
let v: Value = res.into_json().unwrap_or(Value::Null);
let said = v
.get("error_description")
.or_else(|| v.get("error"))
.and_then(Value::as_str)
.map(String::from)
.unwrap_or_else(|| format!("{code}"));
format!("{what}: {said}")
}
ureq::Error::Transport(t) => format!("Could not reach the server: {t}"),
}
}
/// Wait for the person to approve the code (or not), checking `cancelled` while waiting.
pub fn await_sign_in(
d: &Discovery,
code: &Code,
cancelled: &AtomicBool,
) -> Result<Account, String> {
let deadline = Instant::now() + Duration::from_secs(code.expires_in.max(1));
let mut interval = Duration::from_secs(code.interval);
let http = agent(Duration::from_secs(15));
while Instant::now() < deadline {
let until = Instant::now() + interval;
while Instant::now() < until {
if cancelled.load(Ordering::SeqCst) {
return Err("The sign-in was cancelled.".into());
}
std::thread::sleep(Duration::from_millis(250));
}
let res = http
.post(&d.device_token)
.set("accept", "application/json")
.send_json(serde_json::json!({
"grant_type": "urn:ietf:params:oauth:grant-type:device_code",
"device_code": code.device_code,
}));
let v: Value = match res {
Ok(r) => r.into_json().unwrap_or(Value::Null),
Err(ureq::Error::Status(_, r)) => r.into_json().unwrap_or(Value::Null),
Err(ureq::Error::Transport(t)) => {
return Err(format!("Could not reach the server: {t}"))
}
};
if let Some(token) = v.get("access_token").and_then(Value::as_str) {
let account = v.get("account");
let field = |k: &str| {
account
.and_then(|a| a.get(k))
.and_then(Value::as_str)
.unwrap_or("")
.to_string()
};
return Ok(Account {
server: d.base.clone(),
token: token.to_string(),
email: field("email"),
name: field("name"),
});
}
match v.get("error").and_then(Value::as_str) {
Some("authorization_pending") => {}
Some("slow_down") => interval += Duration::from_secs(5),
Some("access_denied") => return Err("The sign-in was denied on the server.".into()),
Some("expired_token") => {
return Err("The code expired before it was approved. Sign in again.".into())
}
Some(other) => return Err(format!("The server refused the sign-in: {other}")),
None => return Err("The server's answer was not understood.".into()),
}
}
Err("The code expired before it was approved. Sign in again.".into())
}
/// Give the token up on the server (it is gone from the server's device list then). Best effort:
/// the app forgets it either way.
pub fn sign_out(base: &str, token: &str) {
let _ = agent(Duration::from_secs(10))
.delete(&format!("{base}/api/v1/token"))
.set("authorization", &format!("Bearer {token}"))
.call();
}
// --- The app's door -------------------------------------------------------------------------
/// A path a page may ask for: on the app's door, and nothing that could leave it.
pub fn checked_path(path: &str) -> Result<&str, ApiError> {
let ok = path.starts_with('/')
&& !path.starts_with("//")
&& !path.contains("://")
&& !path.contains('#')
&& !path.contains('\\')
&& !path.split(['/', '?']).any(|part| part == "..")
&& path.chars().all(|c| !c.is_control() && c != ' ');
if ok {
Ok(path)
} else {
Err(ApiError::new(
400,
format!("Not a path on the server: {path}"),
))
}
}
/// One request to `/api/v2`, as the signed-in account. The JSON answer, or `null` for none.
pub fn request(
app: &str,
token: &str,
method: &str,
path: &str,
body: Option<&Value>,
) -> Result<Value, ApiError> {
let path = checked_path(path)?;
let method = method.to_ascii_uppercase();
if !["GET", "POST", "PATCH", "PUT", "DELETE"].contains(&method.as_str()) {
return Err(ApiError::new(400, format!("No such method: {method}")));
}
let req = agent(Duration::from_secs(60))
.request(&method, &format!("{app}{path}"))
.set("authorization", &format!("Bearer {token}"))
.set("accept", "application/json");
let res = match body {
Some(b) => req.send_json(b),
None => req.call(),
}?;
if res.status() == 204 {
return Ok(Value::Null);
}
let text = res
.into_string()
.map_err(|e| ApiError::new(0, format!("The server's answer could not be read: {e}")))?;
if text.trim().is_empty() {
return Ok(Value::Null);
}
serde_json::from_str(&text)
.map_err(|_| ApiError::new(0, "The server's answer was not JSON.".to_string()))
}
/// Server-sent events, a line at a time: what `stream` hands on, one `(event, data)` per frame.
#[derive(Default)]
pub struct Sse {
event: String,
data: Vec<String>,
}
impl Sse {
/// Feed one line (without its newline); a blank line ends a frame and returns it.
pub fn line(&mut self, line: &str) -> Option<(String, String)> {
let line = line.strip_suffix('\r').unwrap_or(line);
if line.is_empty() {
if self.data.is_empty() && self.event.is_empty() {
return None;
}
let event = std::mem::take(&mut self.event);
let data = std::mem::take(&mut self.data).join("\n");
return Some((
if event.is_empty() {
"message".into()
} else {
event
},
data,
));
}
if line.starts_with(':') {
return None; // a keepalive
}
let (field, value) = match line.split_once(':') {
Some((f, v)) => (f, v.strip_prefix(' ').unwrap_or(v)),
None => (line, ""),
};
match field {
"event" => self.event = value.to_string(),
"data" => self.data.push(value.to_string()),
_ => {}
}
None
}
}
/// Follow a reply as it is written (`GET …/stream`), handing each frame to `frame` until the
/// server closes it, `frame` says stop (false), or `stop` is set. Keepalives arrive often enough
/// that `stop` is noticed within seconds.
pub fn stream(
app: &str,
token: &str,
path: &str,
stop: &AtomicBool,
mut frame: impl FnMut(&str, &str) -> bool,
) -> Result<(), ApiError> {
let path = checked_path(path)?;
let res = agent(Duration::from_secs(90))
.get(&format!("{app}{path}"))
.set("authorization", &format!("Bearer {token}"))
.set("accept", "text/event-stream")
.call()?;
let mut sse = Sse::default();
for line in BufReader::new(res.into_reader()).lines() {
if stop.load(Ordering::SeqCst) {
return Ok(());
}
let line = line.map_err(|e| ApiError::new(0, format!("The stream broke off: {e}")))?;
if let Some((event, data)) = sse.line(&line) {
if !frame(&event, &data) || event == "close" {
return Ok(());
}
}
}
Ok(())
}
#[cfg(test)]
mod tests {
use super::*;
use serde_json::json;
fn two_oh() -> Value {
json!({
"service": "lembas",
"version": "2.0.0-beta.1",
"name": "Example",
"protocol": 3,
"protocols": [3],
"app_api": 1,
"api": {"app": "https://ai.example/api/v2"},
"login": {"device": {
"code": "https://ai.example/api/device/code",
"token": "https://ai.example/api/device/token"
}}
})
}
#[test]
fn a_2_0_server_passes() {
let d = check(&two_oh(), "https://ai.example").unwrap();
assert_eq!(d.app, "https://ai.example/api/v2");
assert_eq!(d.name, "Example");
assert_eq!(d.device_token, "https://ai.example/api/device/token");
}
#[test]
fn an_older_server_is_refused_and_told_which_side_to_update() {
// 1.x: protocol frozen at 1, no `protocols`, no app door.
let old = json!({"service": "lembas", "version": "1.7.3", "protocol": 1});
let why = check(&old, "https://ai.example").unwrap_err();
assert!(why.contains("LLeMbas 1.7.3"), "{why}");
assert!(why.contains("needs a LLeMbas 2.0 server"), "{why}");
// Protocol 3 alone is not enough: the version must say 2.
let mut early = two_oh();
early["version"] = json!("1.7.2");
assert!(check(&early, "https://ai.example").is_err());
// Version 2 without protocol 3 is not one either.
let mut odd = two_oh();
odd["protocols"] = json!([1, 2]);
assert!(check(&odd, "https://ai.example").is_err());
}
#[test]
fn an_app_interface_this_app_does_not_know_is_refused() {
let mut newer = two_oh();
newer["app_api"] = json!(APP_API + 1);
assert!(check(&newer, "https://ai.example")
.unwrap_err()
.contains("Update LLeMbas Desktop"));
let mut none = two_oh();
none.as_object_mut().unwrap().remove("app_api");
assert!(check(&none, "https://ai.example").is_err());
let not_ours = json!({"service": "other"});
assert!(check(&not_ours, "https://ai.example").is_err());
}
#[test]
fn versions_read_their_major() {
assert_eq!(major("2.0.0-beta.1"), Some(2));
assert_eq!(major("v10.1.0"), Some(10));
assert_eq!(major("1.7.3"), Some(1));
assert_eq!(major(""), None);
}
#[test]
fn a_page_reaches_only_the_app_door() {
assert!(checked_path("/chats?kind=agent&limit=50").is_ok());
assert!(checked_path("/chats/abc/messages/def/stream").is_ok());
for bad in [
"chats",
"//evil.example/x",
"/x://y",
"/../v1/admin",
"/chats/../../v1",
"/a#b",
"/a b",
"/a\\b",
] {
assert!(checked_path(bad).is_err(), "{bad}");
}
}
#[test]
fn server_sent_events_come_out_whole() {
let mut sse = Sse::default();
let mut got = vec![];
for line in [
": keepalive",
"",
"event: tail",
"data: {\"text\":\"a\"}",
"",
"event: steps",
"data: one",
"data: two",
"\r",
"data: plain",
"",
] {
if let Some(f) = sse.line(line) {
got.push(f);
}
}
assert_eq!(
got,
vec![
("tail".to_string(), "{\"text\":\"a\"}".to_string()),
("steps".to_string(), "one\ntwo".to_string()),
("message".to_string(), "plain".to_string()),
]
);
}
#[test]
fn the_account_file_keeps_its_server_and_hides_its_token() {
let dir = std::env::temp_dir().join(format!("llembas-account-{}", std::process::id()));
let _ = fs::remove_dir_all(&dir);
let a = Account {
server: "https://ai.example".into(),
token: "secret".into(),
email: "a@example.org".into(),
name: "A".into(),
};
save_account(&dir, &a).unwrap();
assert_eq!(load_account(&dir, "https://ai.example"), Some(a.clone()));
assert_eq!(load_account(&dir, "https://other.example"), None);
assert!(!serde_json::to_string(&a.public())
.unwrap()
.contains("secret"));
#[cfg(unix)]
{
use std::os::unix::fs::PermissionsExt;
let mode = fs::metadata(account_file(&dir))
.unwrap()
.permissions()
.mode();
assert_eq!(mode & 0o777, 0o600);
}
forget_account(&dir);
assert_eq!(load_account(&dir, "https://ai.example"), None);
fs::remove_dir_all(&dir).unwrap();
}
}