Merge pull request #724 from mahkoh/jorth/dbus-challenge-response

dbus: use challenge-response authentication

src/dbus.rs

@@ -98,6 +98,8 @@ pub enum DbusError {
     ReadError(#[source] IoUringError),
     #[error("timeout")]
     IoUringError(#[source] Box<IoUringError>),
+    #[error("Server did not send auth challenge")]
+    NoChallenge,
     #[error("Server did not accept our authentication")]
     Auth,
     #[error("Array length is not a multiple of the element size")]

src/dbus/auth.rs

@@ -1,7 +1,7 @@
 use {
     crate::{
         dbus::{DbusError, DbusSocket, incoming::handle_incoming, outgoing::handle_outgoing},
-        utils::{buf::Buf, errorfmt::ErrorFmt, hex},
+        utils::{buf::Buf, errorfmt::ErrorFmt},
     },
     std::{ops::Deref, rc::Rc},
 };
@@ -52,34 +52,33 @@ impl Auth {
     }
 
     async fn handle_auth(&mut self) -> Result<(), DbusError> {
-        let uid = hex::to_hex(&uapi::getuid().to_string());
-        let mut out_buf = Buf::new(128);
-        {
-            let buf = out_buf
-                .write_fmt(format_args!("\0AUTH EXTERNAL {}\r\n", uid))
-                .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 != "OK" {
+        if read_cmd!() != "DATA" {
+            return Err(DbusError::NoChallenge);
+        }
+        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(())
     }
 

src/utils.rs

@@ -24,7 +24,6 @@ pub mod free_list;
 pub mod geometric_decay;
 pub mod gfx_api_ext;
 pub mod hash_map_ext;
-pub mod hex;
 pub mod line_logger;
 pub mod linkedlist;
 pub mod log_on_drop;

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();

src/utils/hex.rs

@@ -1,15 +0,0 @@
-pub fn to_hex(b: &str) -> String {
-    let mut s = String::with_capacity(b.len() * 2);
-    for &b in b.as_bytes() {
-        s.push(nibble_to_hex(b >> 4) as char);
-        s.push(nibble_to_hex(b & 7) as char);
-    }
-    s
-}
-
-fn nibble_to_hex(n: u8) -> u8 {
-    match n {
-        n @ 0..=9 => b'0' + n,
-        n => b'a' + n,
-    }
-}