rust-chg: abort if server doesn't have required capabilities

It's checked at Locator::connect() since we'll have to do more stuff in
this function.

Differential Revision: https://phab.mercurial-scm.org/D8361

rust/chg/src/locator.rs

@@ -1,241 +1,266 b''
 // Copyright 2011, 2018 Yuya Nishihara <[e-mail]>
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
 //! Utility for locating command-server process.
 
 use futures::future::{self, Either, Loop};
 use std::env;
 use std::ffi::{OsStr, OsString};
 use std::fs::{self, DirBuilder};
 use std::io;
 use std::os::unix::ffi::{OsStrExt, OsStringExt};
 use std::os::unix::fs::{DirBuilderExt, MetadataExt};
 use std::path::{Path, PathBuf};
 use std::process::{self, Command};
 use std::time::Duration;
 use tokio::prelude::*;
 use tokio_hglib::UnixClient;
 use tokio_process::{Child, CommandExt};
 use tokio_timer;
 
+use super::message::ServerSpec;
 use super::procutil;
 
+const REQUIRED_SERVER_CAPABILITIES: &[&str] = &["attachio", "chdir", "runcommand"];
+
 /// Helper to connect to and spawn a server process.
 #[derive(Clone, Debug)]
 pub struct Locator {
     hg_command: OsString,
     current_dir: PathBuf,
     env_vars: Vec<(OsString, OsString)>,
     process_id: u32,
     base_sock_path: PathBuf,
     timeout: Duration,
 }
 
 impl Locator {
     /// Creates locator capturing the current process environment.
     ///
     /// If no `$CHGSOCKNAME` is specified, the socket directory will be
     /// created as necessary.
     pub fn prepare_from_env() -> io::Result<Locator> {
         Ok(Locator {
             hg_command: default_hg_command(),
             current_dir: env::current_dir()?,
             env_vars: env::vars_os().collect(),
             process_id: process::id(),
             base_sock_path: prepare_server_socket_path()?,
             timeout: default_timeout(),
         })
     }
 
     /// Temporary socket path for this client process.
     fn temp_sock_path(&self) -> PathBuf {
         let src = self.base_sock_path.as_os_str().as_bytes();
         let mut buf = Vec::with_capacity(src.len() + 6); // "{src}.{pid}".len()
         buf.extend_from_slice(src);
         buf.extend_from_slice(format!(".{}", self.process_id).as_bytes());
         OsString::from_vec(buf).into()
     }
 
     /// Connects to the server.
     ///
     /// The server process will be spawned if not running.
     pub fn connect(self) -> impl Future<Item = (Self, UnixClient), Error = io::Error> {
         self.try_connect()
     }
 
     /// Tries to connect to the existing server, or spawns new if not running.
     fn try_connect(self) -> impl Future<Item = (Self, UnixClient), Error = io::Error> {
         debug!("try connect to {}", self.base_sock_path.display());
-        UnixClient::connect(self.base_sock_path.clone()).then(|res| match res {
-            Ok(client) => Either::A(future::ok((self, client))),
-            Err(_) => Either::B(self.spawn_connect()),
-        })
+        UnixClient::connect(self.base_sock_path.clone())
+            .then(|res| match res {
+                Ok(client) => Either::A(future::ok((self, client))),
+                Err(_) => Either::B(self.spawn_connect()),
+            })
+            .and_then(|(loc, client)| {
+                check_server_capabilities(client.server_spec())?;
+                Ok((loc, client))
+            })
     }
 
     /// Spawns new server process and connects to it.
     ///
     /// The server will be spawned at the current working directory, then
     /// chdir to "/", so that the server will load configs from the target
     /// repository.
     fn spawn_connect(self) -> impl Future<Item = (Self, UnixClient), Error = io::Error> {
         let sock_path = self.temp_sock_path();
         debug!("start cmdserver at {}", sock_path.display());
         Command::new(&self.hg_command)
             .arg("serve")
             .arg("--cmdserver")
             .arg("chgunix")
             .arg("--address")
             .arg(&sock_path)
             .arg("--daemon-postexec")
             .arg("chdir:/")
             .current_dir(&self.current_dir)
             .env_clear()
             .envs(self.env_vars.iter().cloned())
             .env("CHGINTERNALMARK", "")
             .spawn_async()
             .into_future()
             .and_then(|server| self.connect_spawned(server, sock_path))
             .and_then(|(loc, client, sock_path)| {
                 debug!(
                     "rename {} to {}",
                     sock_path.display(),
                     loc.base_sock_path.display()
                 );
                 fs::rename(&sock_path, &loc.base_sock_path)?;
                 Ok((loc, client))
             })
     }
 
     /// Tries to connect to the just spawned server repeatedly until timeout
     /// exceeded.
     fn connect_spawned(
         self,
         server: Child,
         sock_path: PathBuf,
     ) -> impl Future<Item = (Self, UnixClient, PathBuf), Error = io::Error> {
         debug!("try connect to {} repeatedly", sock_path.display());
         let connect = future::loop_fn(sock_path, |sock_path| {
             UnixClient::connect(sock_path.clone()).then(|res| {
                 match res {
                     Ok(client) => Either::A(future::ok(Loop::Break((client, sock_path)))),
                     Err(_) => {
                         // try again with slight delay
                         let fut = tokio_timer::sleep(Duration::from_millis(10))
                             .map(|()| Loop::Continue(sock_path))
                             .map_err(|err| io::Error::new(io::ErrorKind::Other, err));
                         Either::B(fut)
                     }
                 }
             })
         });
 
         // waits for either connection established or server failed to start
         connect
             .select2(server)
             .map_err(|res| res.split().0)
             .timeout(self.timeout)
             .map_err(|err| {
                 err.into_inner().unwrap_or_else(|| {
                     io::Error::new(
                         io::ErrorKind::TimedOut,
                         "timed out while connecting to server",
                     )
                 })
             })
             .and_then(|res| {
                 match res {
                     Either::A(((client, sock_path), server)) => {
                         server.forget(); // continue to run in background
                         Ok((self, client, sock_path))
                     }
                     Either::B((st, _)) => Err(io::Error::new(
                         io::ErrorKind::Other,
                         format!("server exited too early: {}", st),
                     )),
                 }
             })
     }
 }
 
 /// Determines the server socket to connect to.
 ///
 /// If no `$CHGSOCKNAME` is specified, the socket directory will be created
 /// as necessary.
 fn prepare_server_socket_path() -> io::Result<PathBuf> {
     if let Some(s) = env::var_os("CHGSOCKNAME") {
         Ok(PathBuf::from(s))
     } else {
         let mut path = default_server_socket_dir();
         create_secure_dir(&path)?;
         path.push("server");
         Ok(path)
     }
 }
 
 /// Determines the default server socket path as follows.
 ///
 /// 1. `$XDG_RUNTIME_DIR/chg`
 /// 2. `$TMPDIR/chg$UID`
 /// 3. `/tmp/chg$UID`
 pub fn default_server_socket_dir() -> PathBuf {
     // XDG_RUNTIME_DIR should be ignored if it has an insufficient permission.
     // https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
     if let Some(Ok(s)) = env::var_os("XDG_RUNTIME_DIR").map(check_secure_dir) {
         let mut path = PathBuf::from(s);
         path.push("chg");
         path
     } else {
         let mut path = env::temp_dir();
         path.push(format!("chg{}", procutil::get_effective_uid()));
         path
     }
 }
 
 /// Determines the default hg command.
 pub fn default_hg_command() -> OsString {
     // TODO: maybe allow embedding the path at compile time (or load from hgrc)
     env::var_os("CHGHG")
         .or(env::var_os("HG"))
         .unwrap_or(OsStr::new("hg").to_owned())
 }
 
 fn default_timeout() -> Duration {
     let secs = env::var("CHGTIMEOUT")
         .ok()
         .and_then(|s| s.parse().ok())
         .unwrap_or(60);
     Duration::from_secs(secs)
 }
 
 /// Creates a directory which the other users cannot access to.
 ///
 /// If the directory already exists, tests its permission.
 fn create_secure_dir<P>(path: P) -> io::Result<()>
 where
     P: AsRef<Path>,
 {
     DirBuilder::new()
         .mode(0o700)
         .create(path.as_ref())
         .or_else(|err| {
             if err.kind() == io::ErrorKind::AlreadyExists {
                 check_secure_dir(path).map(|_| ())
             } else {
                 Err(err)
             }
         })
 }
 
 fn check_secure_dir<P>(path: P) -> io::Result<P>
 where
     P: AsRef<Path>,
 {
     let a = fs::symlink_metadata(path.as_ref())?;
     if a.is_dir() && a.uid() == procutil::get_effective_uid() && (a.mode() & 0o777) == 0o700 {
         Ok(path)
     } else {
         Err(io::Error::new(io::ErrorKind::Other, "insecure directory"))
     }
 }
+
+fn check_server_capabilities(spec: &ServerSpec) -> io::Result<()> {
+    let unsupported: Vec<_> = REQUIRED_SERVER_CAPABILITIES
+        .iter()
+        .cloned()
+        .filter(|&s| !spec.capabilities.contains(s))
+        .collect();
+    if unsupported.is_empty() {
+        Ok(())
+    } else {
+        let msg = format!(
+            "insufficient server capabilities: {}",
+            unsupported.join(", ")
+        );
+        Err(io::Error::new(io::ErrorKind::Other, msg))
+    }
+}