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use std::{
any::Any,
borrow::Cow,
error::Error,
ffi::{OsStr, OsString},
io::Write,
process::{self, Stdio},
};
use bstr::{io::BufReadExt, BStr, BString, ByteSlice};
use crate::{
client::{self, git, ssh, MessageKind, RequestWriter, SetServiceResponse, WriteMode},
Protocol, Service,
};
// from https://github.com/git/git/blob/20de7e7e4f4e9ae52e6cc7cfaa6469f186ddb0fa/environment.c#L115:L115
const ENV_VARS_TO_REMOVE: &[&str] = &[
"GIT_ALTERNATE_OBJECT_DIRECTORIES",
"GIT_CONFIG",
"GIT_CONFIG_PARAMETERS",
"GIT_OBJECT_DIRECTORY",
"GIT_DIR",
"GIT_WORK_TREE",
"GIT_IMPLICIT_WORK_TREE",
"GIT_GRAFT_FILE",
"GIT_INDEX_FILE",
"GIT_NO_REPLACE_OBJECTS",
"GIT_REPLACE_REF_BASE",
"GIT_PREFIX",
"GIT_INTERNAL_SUPER_PREFIX",
"GIT_SHALLOW_FILE",
"GIT_COMMON_DIR",
"GIT_CONFIG_COUNT",
];
/// A utility to spawn a helper process to actually transmit data, possibly over `ssh`.
///
/// It can only be instantiated using the local [`connect()`] or [ssh connect][crate::client::ssh::connect()].
pub struct SpawnProcessOnDemand {
desired_version: Protocol,
url: gix_url::Url,
path: BString,
ssh_cmd: Option<(OsString, ssh::ProgramKind)>,
/// The environment variables to set in the invoked command.
envs: Vec<(&'static str, String)>,
ssh_disallow_shell: bool,
connection: Option<git::Connection<Box<dyn std::io::Read + Send>, process::ChildStdin>>,
child: Option<process::Child>,
}
impl SpawnProcessOnDemand {
pub(crate) fn new_ssh(
url: gix_url::Url,
program: impl Into<OsString>,
path: BString,
ssh_kind: ssh::ProgramKind,
ssh_disallow_shell: bool,
version: Protocol,
) -> SpawnProcessOnDemand {
SpawnProcessOnDemand {
url,
path,
ssh_cmd: Some((program.into(), ssh_kind)),
envs: Default::default(),
ssh_disallow_shell,
child: None,
connection: None,
desired_version: version,
}
}
fn new_local(path: BString, version: Protocol) -> SpawnProcessOnDemand {
SpawnProcessOnDemand {
url: gix_url::Url::from_parts(gix_url::Scheme::File, None, None, None, None, path.clone(), true)
.expect("valid url"),
path,
ssh_cmd: None,
envs: (version != Protocol::V1)
.then(|| vec![("GIT_PROTOCOL", format!("version={}", version as usize))])
.unwrap_or_default(),
ssh_disallow_shell: false,
child: None,
connection: None,
desired_version: version,
}
}
}
impl client::TransportWithoutIO for SpawnProcessOnDemand {
fn set_identity(&mut self, identity: gix_sec::identity::Account) -> Result<(), client::Error> {
if self.url.scheme == gix_url::Scheme::Ssh {
self.url
.set_user((!identity.username.is_empty()).then_some(identity.username));
Ok(())
} else {
Err(client::Error::AuthenticationUnsupported)
}
}
fn request(
&mut self,
write_mode: WriteMode,
on_into_read: MessageKind,
) -> Result<RequestWriter<'_>, client::Error> {
self.connection
.as_mut()
.expect("handshake() to have been called first")
.request(write_mode, on_into_read)
}
fn to_url(&self) -> Cow<'_, BStr> {
Cow::Owned(self.url.to_bstring())
}
fn connection_persists_across_multiple_requests(&self) -> bool {
true
}
fn configure(&mut self, _config: &dyn Any) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
Ok(())
}
}
struct ReadStdoutFailOnError {
recv: std::sync::mpsc::Receiver<std::io::Error>,
read: std::process::ChildStdout,
}
fn supervise_stderr(
ssh_kind: ssh::ProgramKind,
stderr: std::process::ChildStderr,
stdout: std::process::ChildStdout,
) -> ReadStdoutFailOnError {
impl ReadStdoutFailOnError {
fn swap_err_if_present_in_stderr(&self, wanted: usize, res: std::io::Result<usize>) -> std::io::Result<usize> {
match self.recv.try_recv().ok() {
Some(err) => Err(err),
None => match res {
Ok(n) if n == wanted => Ok(n),
Ok(n) => {
// TODO: fix this
// When parsing refs this seems to happen legitimately
// (even though we read packet lines only and should always know exactly how much to read)
// Maybe this still happens in `read_exact()` as sometimes we just don't get enough bytes
// despite knowing how many.
// To prevent deadlock, we have to set a timeout which slows down legitimate parts of the protocol.
// This code was specifically written to make the `cargo` test-suite pass, and we can reduce
// the timeouts even more once there is a native ssh transport that is used by `cargo`, it will
// be able to handle these properly.
// Alternatively, one could implement something like `read2` to avoid blocking on stderr entirely.
self.recv
.recv_timeout(std::time::Duration::from_millis(5))
.ok()
.map_or(Ok(n), Err)
}
Err(err) => Err(self.recv.recv().ok().unwrap_or(err)),
},
}
}
}
impl std::io::Read for ReadStdoutFailOnError {
fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
let res = self.read.read(buf);
self.swap_err_if_present_in_stderr(buf.len(), res)
}
}
let (send, recv) = std::sync::mpsc::sync_channel(1);
std::thread::Builder::new()
.name("supervise ssh stderr".into())
.stack_size(128 * 1024)
.spawn(move || -> std::io::Result<()> {
let mut process_stderr = std::io::stderr();
for line in std::io::BufReader::new(stderr).byte_lines() {
let line = line?;
match ssh_kind.line_to_err(line.into()) {
Ok(err) => {
send.send(err).ok();
}
Err(line) => {
process_stderr.write_all(&line).ok();
writeln!(&process_stderr).ok();
}
}
}
Ok(())
})
.expect("named threads with small stack work on all platforms");
ReadStdoutFailOnError { read: stdout, recv }
}
impl client::Transport for SpawnProcessOnDemand {
fn handshake<'a>(
&mut self,
service: Service,
extra_parameters: &'a [(&'a str, Option<&'a str>)],
) -> Result<SetServiceResponse<'_>, client::Error> {
let (mut cmd, ssh_kind, cmd_name) = match &self.ssh_cmd {
Some((command, kind)) => (
kind.prepare_invocation(command, &self.url, self.desired_version, self.ssh_disallow_shell)
.map_err(client::Error::SshInvocation)?
.stderr(Stdio::piped()),
Some(*kind),
Cow::Owned(command.to_owned()),
),
None => (
gix_command::prepare(service.as_str()).stderr(Stdio::null()),
None,
Cow::Borrowed(OsStr::new(service.as_str())),
),
};
cmd.stdin = Stdio::piped();
cmd.stdout = Stdio::piped();
if self.path.first() == Some(&b'-') {
return Err(client::Error::AmbiguousPath {
path: self.path.clone(),
});
}
let repo_path = if self.ssh_cmd.is_some() {
cmd.args.push(service.as_str().into());
gix_quote::single(self.path.as_ref()).to_os_str_lossy().into_owned()
} else {
self.path.to_os_str_lossy().into_owned()
};
cmd.args.push(repo_path);
let mut cmd = std::process::Command::from(cmd);
for env_to_remove in ENV_VARS_TO_REMOVE {
cmd.env_remove(env_to_remove);
}
cmd.envs(std::mem::take(&mut self.envs));
gix_features::trace::debug!(command = ?cmd, "gix_transport::SpawnProcessOnDemand");
let mut child = cmd.spawn().map_err(|err| client::Error::InvokeProgram {
source: err,
command: cmd_name.into_owned(),
})?;
let stdout: Box<dyn std::io::Read + Send> = match ssh_kind {
Some(ssh_kind) => Box::new(supervise_stderr(
ssh_kind,
child.stderr.take().expect("configured beforehand"),
child.stdout.take().expect("configured"),
)),
None => Box::new(child.stdout.take().expect("stdout configured")),
};
self.connection = Some(git::Connection::new_for_spawned_process(
stdout,
child.stdin.take().expect("stdin configured"),
self.desired_version,
self.path.clone(),
));
self.child = Some(child);
self.connection
.as_mut()
.expect("connection to be there right after setting it")
.handshake(service, extra_parameters)
}
}
/// Connect to a locally readable repository at `path` using the given `desired_version`.
///
/// This will spawn a `git` process locally.
pub fn connect(
path: impl Into<BString>,
desired_version: Protocol,
) -> Result<SpawnProcessOnDemand, std::convert::Infallible> {
Ok(SpawnProcessOnDemand::new_local(path.into(), desired_version))
}
#[cfg(test)]
mod tests {
mod ssh {
mod connect {
use crate::{client::blocking_io::ssh::connect, Protocol};
#[test]
fn path() {
for (url, expected) in [
("ssh://host.xy/~/repo", "~/repo"),
("ssh://host.xy/~username/repo", "~username/repo"),
("user@host.xy:/username/repo", "/username/repo"),
("user@host.xy:username/repo", "username/repo"),
("user@host.xy:../username/repo", "../username/repo"),
("user@host.xy:~/repo", "~/repo"),
] {
let url = gix_url::parse((*url).into()).expect("valid url");
let cmd = connect(url, Protocol::V1, Default::default()).expect("parse success");
assert_eq!(cmd.path, expected, "the path will be substituted by the remote shell");
}
}
}
}
}
|