aerogramme/src/imap/session.rs

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Rust
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use anyhow::Error;
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use boitalettres::errors::Error as BalError;
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use boitalettres::proto::{Request, Response};
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use futures::future::BoxFuture;
use futures::future::FutureExt;
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use tokio::sync::mpsc::error::TrySendError;
use tokio::sync::{mpsc, oneshot};
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use crate::imap::command::{anonymous, authenticated, examined, selected};
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use crate::imap::flow;
use crate::login::ArcLoginProvider;
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/* This constant configures backpressure in the system,
* or more specifically, how many pipelined messages are allowed
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* before refusing them
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*/
const MAX_PIPELINED_COMMANDS: usize = 10;
struct Message {
req: Request,
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tx: oneshot::Sender<Result<Response, BalError>>,
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}
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//-----
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pub struct Manager {
tx: mpsc::Sender<Message>,
}
impl Manager {
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pub fn new(login_provider: ArcLoginProvider) -> Self {
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let (tx, rx) = mpsc::channel(MAX_PIPELINED_COMMANDS);
tokio::spawn(async move {
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let instance = Instance::new(login_provider, rx);
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instance.start().await;
});
Self { tx }
}
pub fn process(&self, req: Request) -> BoxFuture<'static, Result<Response, BalError>> {
let (tx, rx) = oneshot::channel();
let msg = Message { req, tx };
// We use try_send on a bounded channel to protect the daemons from DoS.
// Pipelining requests in IMAP are a special case: they should not occure often
// and in a limited number (like 3 requests). Someone filling the channel
// will probably be malicious so we "rate limit" them.
match self.tx.try_send(msg) {
Ok(()) => (),
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Err(TrySendError::Full(_)) => {
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return async { Response::bad("Too fast! Send less pipelined requests.") }.boxed()
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}
Err(TrySendError::Closed(_)) => {
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return async { Err(BalError::Text("Terminated session".to_string())) }.boxed()
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}
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};
// @FIXME add a timeout, handle a session that fails.
async {
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match rx.await {
Ok(r) => r,
Err(e) => {
tracing::warn!("Got error {:#?}", e);
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Response::bad("No response from the session handler")
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}
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}
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}
.boxed()
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}
}
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//-----
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pub struct InnerContext<'a> {
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pub req: &'a Request,
pub state: &'a flow::State,
pub login: &'a ArcLoginProvider,
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}
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pub struct Instance {
rx: mpsc::Receiver<Message>,
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pub login_provider: ArcLoginProvider,
pub state: flow::State,
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}
impl Instance {
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fn new(login_provider: ArcLoginProvider, rx: mpsc::Receiver<Message>) -> Self {
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Self {
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login_provider,
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rx,
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state: flow::State::NotAuthenticated,
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}
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}
//@FIXME add a function that compute the runner's name from its local info
// to ease debug
// fn name(&self) -> String { }
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async fn start(mut self) {
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//@FIXME add more info about the runner
tracing::debug!("starting runner");
while let Some(msg) = self.rx.recv().await {
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// Command behavior is modulated by the state.
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// To prevent state error, we handle the same command in separate code paths.
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let ctrl = match &mut self.state {
flow::State::NotAuthenticated => {
let ctx = anonymous::AnonymousContext {
req: &msg.req,
login_provider: Some(&self.login_provider),
};
anonymous::dispatch(ctx).await
}
flow::State::Authenticated(ref user) => {
let ctx = authenticated::AuthenticatedContext {
req: &msg.req,
user,
};
authenticated::dispatch(ctx).await
}
flow::State::Selected(ref user, ref mut mailbox) => {
let ctx = selected::SelectedContext {
req: &msg.req,
user,
mailbox,
};
selected::dispatch(ctx).await
}
flow::State::Examined(ref user, ref mut mailbox) => {
let ctx = examined::ExaminedContext {
req: &msg.req,
user,
mailbox,
};
examined::dispatch(ctx).await
}
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flow::State::Logout => {
Response::bad("No commands are allowed in the LOGOUT state.")
.map(|r| (r, flow::Transition::None))
.map_err(Error::msg)
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}
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};
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// Process result
let res = match ctrl {
Ok((res, tr)) => {
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//@FIXME remove unwrap
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self.state = self.state.apply(tr).unwrap();
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//@FIXME enrich here the command with some global status
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Ok(res)
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}
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// Cast from anyhow::Error to Bal::Error
// @FIXME proper error handling would be great
Err(e) => match e.downcast::<BalError>() {
Ok(be) => Err(be),
Err(e) => {
tracing::warn!(error=%e, "internal.error");
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Response::bad("Internal error")
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}
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},
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};
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//@FIXME I think we should quit this thread on error and having our manager watch it,
// and then abort the session as it is corrupted.
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msg.tx.send(res).unwrap_or_else(|e| {
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tracing::warn!("failed to send imap response to manager: {:#?}", e)
});
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if let flow::State::Logout = &self.state {
break;
}
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}
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//@FIXME add more info about the runner
tracing::debug!("exiting runner");
}
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}