view rust/chg/src/locator.rs @ 51711:832a1aeb576f

pytype: only try the hacky way of finding PYTHON if not provided

This allows us to work in more environments, like when using pyenv. This
syntax is compatible with all POSIX shells.

// 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 log::debug;
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, Child, Command};
use std::time::{Duration, Instant};
use tokio::time;

use crate::clientext::ChgClient;
use crate::message::{Instruction, ServerSpec};
use crate::procutil;

const REQUIRED_SERVER_CAPABILITIES: &[&str] = &[
    "attachio",
    "chdir",
    "runcommand",
    "setenv",
    "setumask2",
    "validate",
];

/// Helper to connect to and spawn a server process.
#[derive(Clone, Debug)]
pub struct Locator {
    hg_command: OsString,
    hg_early_args: Vec<OsString>,
    current_dir: PathBuf,
    env_vars: Vec<(OsString, OsString)>,
    process_id: u32,
    base_sock_path: PathBuf,
    redirect_sock_path: Option<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(),
            hg_early_args: Vec::new(),
            current_dir: env::current_dir()?,
            env_vars: env::vars_os().collect(),
            process_id: process::id(),
            base_sock_path: prepare_server_socket_path()?,
            redirect_sock_path: None,
            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()
    }

    /// Specifies the arguments to be passed to the server at start.
    pub fn set_early_args(
        &mut self,
        args: impl IntoIterator<Item = impl AsRef<OsStr>>,
    ) {
        self.hg_early_args =
            args.into_iter().map(|a| a.as_ref().to_owned()).collect();
    }

    /// Connects to the server.
    ///
    /// The server process will be spawned if not running.
    pub async fn connect(&mut self) -> io::Result<ChgClient> {
        for _cnt in 0..10 {
            let mut client = self.try_connect().await?;
            let instructions = client.validate(&self.hg_early_args).await?;
            let reconnect = self.run_instructions(&instructions)?;
            if !reconnect {
                return Ok(client);
            }
        }

        let msg = format!(
            concat!(
                "too many redirections.\n",
                "Please make sure {:?} is not a wrapper which ",
                "changes sensitive environment variables ",
                "before executing hg. If you have to use a ",
                "wrapper, wrap chg instead of hg.",
            ),
            self.hg_command
        );
        Err(io::Error::new(io::ErrorKind::Other, msg))
    }

    /// Runs instructions received from the server.
    ///
    /// Returns true if the client should try connecting to the other server.
    fn run_instructions(
        &mut self,
        instructions: &[Instruction],
    ) -> io::Result<bool> {
        let mut reconnect = false;
        for inst in instructions {
            debug!("instruction: {:?}", inst);
            match inst {
                Instruction::Exit(_) => {
                    // Just returns the current connection to run the
                    // unparsable command and report the error
                    return Ok(false);
                }
                Instruction::Reconnect => {
                    reconnect = true;
                }
                Instruction::Redirect(path) => {
                    if path.parent() != self.base_sock_path.parent() {
                        let msg = format!(
                            "insecure redirect instruction from server: {}",
                            path.display()
                        );
                        return Err(io::Error::new(
                            io::ErrorKind::InvalidData,
                            msg,
                        ));
                    }
                    self.redirect_sock_path = Some(path.to_owned());
                    reconnect = true;
                }
                Instruction::Unlink(path) => {
                    if path.parent() != self.base_sock_path.parent() {
                        let msg = format!(
                            "insecure unlink instruction from server: {}",
                            path.display()
                        );
                        return Err(io::Error::new(
                            io::ErrorKind::InvalidData,
                            msg,
                        ));
                    }
                    fs::remove_file(path).unwrap_or(()); // may race
                }
            }
        }

        Ok(reconnect)
    }

    /// Tries to connect to the existing server, or spawns new if not running.
    async fn try_connect(&mut self) -> io::Result<ChgClient> {
        let sock_path = self
            .redirect_sock_path
            .as_ref()
            .unwrap_or(&self.base_sock_path)
            .clone();
        debug!("try connect to {}", sock_path.display());
        let mut client = match ChgClient::connect(sock_path).await {
            Ok(client) => client,
            Err(_) => {
                // Prevent us from being re-connected to the outdated
                // master server: We were told by the server to redirect
                // to redirect_sock_path, which didn't work. We do not
                // want to connect to the same master server again
                // because it would probably tell us the same thing.
                if self.redirect_sock_path.is_some() {
                    fs::remove_file(&self.base_sock_path).unwrap_or(());
                    // may race
                }
                self.spawn_connect().await?
            }
        };
        check_server_capabilities(client.server_spec())?;
        // It's purely optional, and the server might not support this command.
        if client.server_spec().capabilities.contains("setprocname") {
            client
                .set_process_name(format!("chg[worker/{}]", self.process_id))
                .await?;
        }
        client.set_current_dir(&self.current_dir).await?;
        client
            .set_env_vars_os(self.env_vars.iter().cloned())
            .await?;
        Ok(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.
    async fn spawn_connect(&mut self) -> io::Result<ChgClient> {
        let sock_path = self.temp_sock_path();
        debug!("start cmdserver at {}", sock_path.display());
        let server = Command::new(&self.hg_command)
            .arg("serve")
            .arg("--cmdserver")
            .arg("chgunix")
            .arg("--address")
            .arg(&sock_path)
            .arg("--daemon-postexec")
            .arg("chdir:/")
            .args(&self.hg_early_args)
            .current_dir(&self.current_dir)
            .env_clear()
            .envs(self.env_vars.iter().cloned())
            .env("CHGINTERNALMARK", "")
            .spawn()?;
        let client = self.connect_spawned(server, &sock_path).await?;
        debug!(
            "rename {} to {}",
            sock_path.display(),
            self.base_sock_path.display()
        );
        fs::rename(&sock_path, &self.base_sock_path)?;
        Ok(client)
    }

    /// Tries to connect to the just spawned server repeatedly until timeout
    /// exceeded.
    async fn connect_spawned(
        &mut self,
        mut server: Child,
        sock_path: &Path,
    ) -> io::Result<ChgClient> {
        debug!("try connect to {} repeatedly", sock_path.display());
        // waits for either connection established or server failed to start
        let start_time = Instant::now();
        while start_time.elapsed() < self.timeout {
            if let Ok(client) = ChgClient::connect(&sock_path).await {
                // server handle is dropped here, but the detached process
                // will continue running in background
                return Ok(client);
            }

            if let Some(st) = server.try_wait()? {
                return Err(io::Error::new(
                    io::ErrorKind::Other,
                    format!("server exited too early: {}", st),
                ));
            }

            // try again with slight delay
            time::delay_for(Duration::from_millis(10)).await;
        }

        Err(io::Error::new(
            io::ErrorKind::TimedOut,
            "timed out while connecting to server",
        ))
    }
}

/// 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(path: impl AsRef<Path>) -> io::Result<()> {
    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))
    }
}

/// Collects arguments which need to be passed to the server at start.
pub fn collect_early_args(
    args: impl IntoIterator<Item = impl AsRef<OsStr>>,
) -> Vec<OsString> {
    let mut args_iter = args.into_iter();
    let mut early_args = Vec::new();
    while let Some(arg) = args_iter.next() {
        let argb = arg.as_ref().as_bytes();
        if argb == b"--" {
            break;
        } else if argb.starts_with(b"--") {
            let mut split = argb[2..].splitn(2, |&c| c == b'=');
            match split.next().unwrap() {
                b"traceback" => {
                    if split.next().is_none() {
                        early_args.push(arg.as_ref().to_owned());
                    }
                }
                b"config" | b"cwd" | b"repo" | b"repository" => {
                    if split.next().is_some() {
                        // --<flag>=<val>
                        early_args.push(arg.as_ref().to_owned());
                    } else {
                        // --<flag> <val>
                        args_iter.next().map(|val| {
                            early_args.push(arg.as_ref().to_owned());
                            early_args.push(val.as_ref().to_owned());
                        });
                    }
                }
                _ => {}
            }
        } else if argb.starts_with(b"-R") {
            if argb.len() > 2 {
                // -R<val>
                early_args.push(arg.as_ref().to_owned());
            } else {
                // -R <val>
                args_iter.next().map(|val| {
                    early_args.push(arg.as_ref().to_owned());
                    early_args.push(val.as_ref().to_owned());
                });
            }
        }
    }

    early_args
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn collect_early_args_some() {
        assert!(collect_early_args(&[] as &[&OsStr]).is_empty());
        assert!(collect_early_args(&["log"]).is_empty());
        assert_eq!(
            collect_early_args(&["log", "-Ra", "foo"]),
            os_string_vec_from(&[b"-Ra"])
        );
        assert_eq!(
            collect_early_args(&["log", "-R", "repo", "", "--traceback", "a"]),
            os_string_vec_from(&[b"-R", b"repo", b"--traceback"])
        );
        assert_eq!(
            collect_early_args(&["log", "--config", "diff.git=1", "-q"]),
            os_string_vec_from(&[b"--config", b"diff.git=1"])
        );
        assert_eq!(
            collect_early_args(&["--cwd=..", "--repository", "r", "log"]),
            os_string_vec_from(&[b"--cwd=..", b"--repository", b"r"])
        );
        assert_eq!(
            collect_early_args(&["log", "--repo=r", "--repos", "a"]),
            os_string_vec_from(&[b"--repo=r"])
        );
    }

    #[test]
    fn collect_early_args_orphaned() {
        assert!(collect_early_args(&["log", "-R"]).is_empty());
        assert!(collect_early_args(&["log", "--config"]).is_empty());
    }

    #[test]
    fn collect_early_args_unwanted_value() {
        assert!(collect_early_args(&["log", "--traceback="]).is_empty());
    }

    fn os_string_vec_from(v: &[&[u8]]) -> Vec<OsString> {
        v.iter().map(|s| OsStr::from_bytes(s).to_owned()).collect()
    }
}