From d6429512e880d2f692fb7ee9648d86535775cd2f Mon Sep 17 00:00:00 2001
From: Todd Mortimer <todd@opennet.ca>
Date: Sun, 25 Jul 2021 21:21:07 -0400
Subject: [PATCH] Handle BYE responses explicitly.

In Session::logout(), ignore it. Fixes #210.
---
 src/client.rs | 50 +++++++++++++++++++++++++++++++++++++++++++++++---
 src/error.rs  | 19 +++++++++++++++++++
 2 files changed, 66 insertions(+), 3 deletions(-)

diff --git a/src/client.rs b/src/client.rs
index 2b1400e..c88f048 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -8,7 +8,7 @@ use std::str;
 use std::sync::mpsc;
 
 use super::authenticator::Authenticator;
-use super::error::{Bad, Error, No, ParseError, Result, ValidateError};
+use super::error::{Bad, Bye, Error, No, ParseError, Result, ValidateError};
 use super::extensions;
 use super::parse::*;
 use super::types::*;
@@ -609,7 +609,18 @@ impl<T: Read + Write> Session<T> {
 
     /// Logout informs the server that the client is done with the connection.
     pub fn logout(&mut self) -> Result<()> {
-        self.run_command_and_check_ok("LOGOUT")
+        // Check for OK or BYE.
+        // According to the RFC:
+        // https://datatracker.ietf.org/doc/html/rfc3501#section-6.1.3
+        // We should get an untagged BYE and a tagged OK.
+        // Apparently some servers send a tagged BYE (imap.wp.pl #210)
+        // instead, so we just treat it like OK since we are logging out
+        // anyway and this avoids returning an error on logout.
+        match self.run_command_and_check_ok("LOGOUT") {
+            Ok(_) => Ok(()),
+            Err(Error::Bye(_)) => Ok(()),
+            resp => resp,
+        }
     }
 
     /// The [`CREATE` command](https://tools.ietf.org/html/rfc3501#section-6.3.3) creates a mailbox
@@ -1337,7 +1348,7 @@ impl<T: Read + Write> Connection<T> {
                     )) => {
                         assert_eq!(tag.as_bytes(), match_tag.as_bytes());
                         Some(match status {
-                            Status::Bad | Status::No => Err((
+                            Status::Bad | Status::No | Status::Bye => Err((
                                 status,
                                 information.map(|v| v.into_owned()),
                                 code.map(|v| v.into_owned()),
@@ -1376,6 +1387,13 @@ impl<T: Read + Write> Connection<T> {
                                     .unwrap_or_else(|| "no explanation given".to_string()),
                             }));
                         }
+                        Status::Bye => {
+                            break Err(Error::Bye(Bye {
+                                code,
+                                information: expl
+                                    .unwrap_or_else(|| "no explanation given".to_string()),
+                            }));
+                        }
                         _ => break Err(Error::Parse(ParseError::Invalid(data.split_off(0)))),
                     }
                 }
@@ -1570,6 +1588,32 @@ mod tests {
         );
     }
 
+    #[test]
+    fn logout_with_untagged_bye() {
+        let response = b"* BYE Logging out\r\na1 OK Logout completed.\r\n".to_vec();
+        let command = format!("a1 LOGOUT\r\n");
+        let mock_stream = MockStream::new(response);
+        let mut session = mock_session!(mock_stream);
+        session.logout().unwrap();
+        assert!(
+            session.stream.get_ref().written_buf == command.as_bytes().to_vec(),
+            "Invalid logout command"
+        );
+    }
+
+    #[test]
+    fn logout_with_tagged_bye() {
+        let response = b"a1 BYE IMAP4rev1 Server logging out\r\n".to_vec();
+        let command = format!("a1 LOGOUT\r\n");
+        let mock_stream = MockStream::new(response);
+        let mut session = mock_session!(mock_stream);
+        session.logout().unwrap();
+        assert!(
+            session.stream.get_ref().written_buf == command.as_bytes().to_vec(),
+            "Invalid logout command"
+        );
+    }
+
     #[test]
     fn rename() {
         let response = b"a1 OK RENAME completed\r\n".to_vec();
diff --git a/src/error.rs b/src/error.rs
index 2dda68c..0ea316c 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -52,6 +52,21 @@ impl fmt::Display for No {
     }
 }
 
+/// A BYE response from the server, which indicates it is going to hang up on us.
+#[derive(Debug)]
+#[non_exhaustive]
+pub struct Bye {
+    /// Human-redable message included with the response.
+    pub information: String,
+    /// A more specific error status code included with the response.
+    pub code: Option<ResponseCode<'static>>,
+}
+
+impl fmt::Display for Bye {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.information)
+    }
+}
 /// A set of errors that can occur in the IMAP client
 #[derive(Debug)]
 #[non_exhaustive]
@@ -71,6 +86,8 @@ pub enum Error {
     Bad(Bad),
     /// A NO response from the IMAP server.
     No(No),
+    /// A BYE response from the IMAP server.
+    Bye(Bye),
     /// The connection was terminated unexpectedly.
     ConnectionLost,
     /// Error parsing a server response.
@@ -148,6 +165,7 @@ impl fmt::Display for Error {
             Error::Parse(ref e) => fmt::Display::fmt(e, f),
             Error::No(ref data) => write!(f, "No Response: {}", data),
             Error::Bad(ref data) => write!(f, "Bad Response: {}", data),
+            Error::Bye(ref data) => write!(f, "Bye Response: {}", data),
             Error::ConnectionLost => f.write_str("Connection Lost"),
             Error::Append => f.write_str("Could not append mail to mailbox"),
             Error::Unexpected(ref r) => write!(f, "Unexpected Response: {:?}", r),
@@ -171,6 +189,7 @@ impl StdError for Error {
             Error::Validate(ref e) => e.description(),
             Error::Bad(_) => "Bad Response",
             Error::No(_) => "No Response",
+            Error::Bye(_) => "Bye Response",
             Error::ConnectionLost => "Connection lost",
             Error::Append => "Could not append mail to mailbox",
             Error::Unexpected(_) => "Unexpected Response",