From d84d4edd902e7ffc66ede1ab8ba7657209f18982 Mon Sep 17 00:00:00 2001
From: Julian Orth <ju.orth@gmail.com>
Date: Sun, 18 Jan 2026 16:01:33 +0100
Subject: [PATCH] dbus: simplify auth function

---
 src/dbus/auth.rs | 45 ++++++++++++++++++++-------------------------
 src/utils/buf.rs |  1 +
 2 files changed, 21 insertions(+), 25 deletions(-)

diff --git a/src/dbus/auth.rs b/src/dbus/auth.rs
index a4685966..344d2697 100644
--- a/src/dbus/auth.rs
+++ b/src/dbus/auth.rs
@@ -52,38 +52,33 @@ impl Auth {
     }
 
     async fn handle_auth(&mut self) -> Result<(), DbusError> {
-        let mut out_buf = Buf::new(128);
-        {
-            let buf = out_buf
-                .write_fmt(format_args!("\0AUTH EXTERNAL\r\nDATA\r\n"))
-                .unwrap();
-            self.write_buf(buf).await?;
+        // dbus-broker hard codes this initial burst of messages
+        const AUTH: &str = "\
+            \0\
+            AUTH EXTERNAL\r\n\
+            DATA\r\n\
+            NEGOTIATE_UNIX_FD\r\n\
+            BEGIN\r\n\
+        ";
+        let out_buf = Buf::from_slice(AUTH.as_bytes());
+        self.write_buf(out_buf).await?;
+        let mut line;
+        macro_rules! read_cmd {
+            () => {{
+                line = self.readline().await?;
+                let (cmd, _) = line_to_cmd(&line);
+                cmd
+            }};
         }
-        let line = self.readline().await?;
-        let (cmd, _) = line_to_cmd(&line);
-        if cmd != "DATA" {
+        if read_cmd!() != "DATA" {
             return Err(DbusError::NoChallenge);
         }
-        let line = self.readline().await?;
-        let (cmd, _) = line_to_cmd(&line);
-        if cmd != "OK" {
+        if read_cmd!() != "OK" {
             return Err(DbusError::Auth);
         }
-        {
-            let buf = out_buf
-                .write_fmt(format_args!("NEGOTIATE_UNIX_FD\r\n"))
-                .unwrap();
-            self.write_buf(buf).await?;
-        }
-        let line = self.readline().await?;
-        let (cmd, _) = line_to_cmd(&line);
-        if cmd != "AGREE_UNIX_FD" {
+        if read_cmd!() != "AGREE_UNIX_FD" {
             return Err(DbusError::UnixFd);
         }
-        {
-            let buf = out_buf.write_fmt(format_args!("BEGIN\r\n")).unwrap();
-            self.write_buf(buf).await?;
-        }
         Ok(())
     }
 
diff --git a/src/utils/buf.rs b/src/utils/buf.rs
index 293f0f5c..b1d87b9d 100644
--- a/src/utils/buf.rs
+++ b/src/utils/buf.rs
@@ -145,6 +145,7 @@ impl Buf {
         unsafe { self.storage.as_ptr().add(self.range.start as _) }
     }
 
+    #[expect(dead_code)]
     pub fn write_fmt(&mut self, args: Arguments) -> Result<Self, io::Error> {
         let cap = self.len();
         let mut buf = self.deref_mut();