libcontainer/process/

container_main_process.rs

use std::collections::HashMap;
use std::fs;
use std::fs::File;
use std::os::fd::AsRawFd;
use std::path::PathBuf;

use nix::sys::wait::{WaitStatus, waitpid};
use nix::unistd::Pid;
use oci_spec::runtime::{Linux, LinuxNamespaceType};
#[cfg(feature = "libseccomp")]
use oci_spec::runtime::{SECCOMP_FD_NAME, VERSION as OCI_VERSION};

use crate::hooks;
use crate::network::network_device::dev_change_net_namespace;
use crate::process::args::{ContainerArgs, ContainerType};
use crate::process::fork::{self, CloneCb};
use crate::process::intel_rdt::setup_intel_rdt;
use crate::process::{channel, container_intermediate_process};
use crate::syscall::SyscallError;
use crate::user_ns::UserNamespaceConfig;

#[derive(Debug, thiserror::Error)]
pub enum ProcessError {
    #[error(transparent)]
    Channel(#[from] channel::ChannelError),
    #[error("failed to write deny to setgroups")]
    SetGroupsDeny(#[source] std::io::Error),
    #[error(transparent)]
    UserNamespace(#[from] crate::user_ns::UserNamespaceError),
    #[error("container state is required")]
    ContainerStateRequired,
    #[error("failed to wait for intermediate process")]
    WaitIntermediateProcess(#[source] nix::Error),
    #[error(transparent)]
    IntelRdt(#[from] crate::process::intel_rdt::IntelRdtError),
    #[error("failed to create intermediate process")]
    IntermediateProcessFailed(#[source] fork::CloneError),
    #[error("failed seccomp listener")]
    #[cfg(feature = "libseccomp")]
    SeccompListener(#[from] crate::process::seccomp_listener::SeccompListenerError),
    #[error("failed setup network device")]
    Network(#[from] crate::network::NetworkError),
    #[error("failed syscall")]
    SyscallOther(#[source] SyscallError),
    #[error("failed hooks {0}")]
    Hooks(#[from] crate::hooks::HookError),
    #[error("failed to build OCI state: {0}")]
    OciStateBuild(String),
}

type Result<T> = std::result::Result<T, ProcessError>;

pub fn container_main_process(container_args: &ContainerArgs) -> Result<(Pid, bool)> {
    // We use a set of channels to communicate between parent and child process.
    // Each channel is uni-directional. Because we will pass these channel to
    // cloned process, we have to be deligent about closing any unused channel.
    // At minimum, we have to close down any unused senders. The corresponding
    // receivers will be cleaned up once the senders are closed down.
    let (mut main_sender, mut main_receiver) = channel::main_channel()?;
    let mut inter_chan = channel::intermediate_channel()?;
    let mut init_chan = channel::init_channel()?;

    let cb: CloneCb = {
        Box::new(|| {
            if let Err(ret) = prctl::set_name("youki:[1:INTER]") {
                tracing::error!(?ret, "failed to set name for child process");
                return ret;
            }

            match container_intermediate_process::container_intermediate_process(
                container_args,
                &mut inter_chan,
                &mut init_chan,
                &mut main_sender,
            ) {
                Ok(_) => 0,
                Err(err) => {
                    tracing::error!("failed to run intermediate process {}", err);
                    match main_sender.send_error(err.to_string()) {
                        Ok(_) => {}
                        Err(e) => {
                            tracing::error!(
                                "error in sending intermediate error message {} to main: {}",
                                err,
                                e
                            )
                        }
                    }
                    -1
                }
            }
        })
    };

    let container_clone_fn = if container_args.as_sibling {
        fork::container_clone_sibling
    } else {
        fork::container_clone
    };

    let intermediate_pid = container_clone_fn(cb).map_err(|err| {
        tracing::error!("failed to fork intermediate process: {}", err);
        ProcessError::IntermediateProcessFailed(err)
    })?;

    // Close down unused fds. The corresponding fds are duplicated to the
    // child process during clone.
    main_sender.close().map_err(|err| {
        tracing::error!("failed to close unused sender: {}", err);
        err
    })?;

    let (mut inter_sender, inter_receiver) = inter_chan;
    let (mut init_sender, init_receiver) = init_chan;

    // If creating a container with new user namespace, the intermediate process will ask
    // the main process to set up uid and gid mapping, once the intermediate
    // process enters into a new user namespace.
    if let Some(config) = &container_args.user_ns_config {
        main_receiver.wait_for_mapping_request()?;
        setup_mapping(config, intermediate_pid)?;
        inter_sender.mapping_written()?;
    }

    // At this point, we don't need to send any message to intermediate process anymore,
    // so we want to close this sender at the earliest point.
    inter_sender.close().map_err(|err| {
        tracing::error!("failed to close unused intermediate sender: {}", err);
        err
    })?;

    // The intermediate process will send the init pid once it forks the init
    // process.  The intermediate process should exit after this point.
    let init_pid = main_receiver.wait_for_intermediate_ready()?;
    let mut need_to_clean_up_intel_rdt_subdirectory = false;

    if let Some(linux) = container_args.spec.linux() {
        if let Some(intel_rdt) = linux.intel_rdt() {
            let container_id = container_args
                .container
                .as_ref()
                .map(|container| container.id());
            need_to_clean_up_intel_rdt_subdirectory =
                setup_intel_rdt(container_id, &init_pid, intel_rdt)?;
        }
    }

    // if file to write the pid to is specified, write pid of the child
    if let Some(pid_file) = &container_args.pid_file {
        if let Err(err) = fs::write(pid_file, format!("{init_pid}")) {
            tracing::warn!("failed to write pid to file: {err}");
        }
    }

    if matches!(container_args.container_type, ContainerType::InitContainer) {
        if let Some(hooks) = container_args.spec.hooks() {
            main_receiver.wait_for_hook_request()?;
            if let Some(container_for_hooks) = &container_args.container {
                hooks::run_hooks(
                    hooks.prestart().as_ref(),
                    Some(&container_for_hooks.state),
                    None,
                    Some(init_pid),
                )
                .map_err(|err| {
                    tracing::error!("failed to run prestart hooks: {}", err);
                    err
                })?;

                hooks::run_hooks(
                    hooks.create_runtime().as_ref(),
                    Some(&container_for_hooks.state),
                    None,
                    Some(init_pid),
                )
                .map_err(|err| {
                    tracing::error!("failed to run create runtime hooks: {}", err);
                    err
                })?;
            }
            init_sender.hook_done()?;
        }
    }

    if let Some(linux) = container_args.spec.linux() {
        move_network_devices_to_container(linux, init_pid, &mut main_receiver, &mut init_sender)?;

        #[cfg(feature = "libseccomp")]
        if let Some(seccomp) = linux.seccomp() {
            let container = container_args
                .container
                .as_ref()
                .ok_or(ProcessError::ContainerStateRequired)?;

            // Determine OCI status based on container type (matching runc behavior)
            let oci_status = match container_args.container_type {
                ContainerType::InitContainer => oci_spec::runtime::ContainerState::Creating,
                ContainerType::TenantContainer { .. } => oci_spec::runtime::ContainerState::Running,
            };

            // Build OCI-compliant ContainerProcessState using builder pattern
            let oci_state = oci_spec::runtime::StateBuilder::default()
                .version(OCI_VERSION)
                .id(container.state.id.clone())
                .status(oci_status)
                .pid(init_pid.as_raw())
                .bundle(container.state.bundle.clone())
                .annotations(container.state.annotations.clone().unwrap_or_default())
                .build()
                .map_err(|e| ProcessError::OciStateBuild(e.to_string()))?;

            let state = oci_spec::runtime::ContainerProcessStateBuilder::default()
                .version(OCI_VERSION)
                .fds(vec![SECCOMP_FD_NAME.to_string()])
                .pid(init_pid.as_raw())
                .metadata(seccomp.listener_metadata().clone().unwrap_or_default())
                .state(oci_state)
                .build()
                .map_err(|e| ProcessError::OciStateBuild(e.to_string()))?;
            crate::process::seccomp_listener::sync_seccomp(
                seccomp,
                &state,
                &mut init_sender,
                &mut main_receiver,
            )?;
        }
    }

    // We don't need to send anything to the init process after this point, so
    // close the sender.
    init_sender.close().map_err(|err| {
        tracing::error!("failed to close unused init sender: {}", err);
        err
    })?;

    main_receiver.wait_for_init_ready().map_err(|err| {
        tracing::error!("failed to wait for init ready: {}", err);
        err
    })?;

    tracing::debug!("init pid is {:?}", init_pid);

    // Close the receiver ends to avoid leaking file descriptors.

    inter_receiver.close().map_err(|err| {
        tracing::error!("failed to close intermediate process receiver: {}", err);
        err
    })?;

    init_receiver.close().map_err(|err| {
        tracing::error!("failed to close init process receiver: {}", err);
        err
    })?;

    main_receiver.close().map_err(|err| {
        tracing::error!("failed to close main process receiver: {}", err);
        err
    })?;

    // Before the main process returns, we want to make sure the intermediate
    // process is exit and reaped. By this point, the intermediate process
    // should already exited successfully. If intermediate process errors out,
    // the `init_ready` will not be sent.
    match waitpid(intermediate_pid, None) {
        Ok(WaitStatus::Exited(_, 0)) => (),
        Ok(WaitStatus::Exited(_, s)) => {
            tracing::warn!("intermediate process failed with exit status: {s}");
        }
        Ok(WaitStatus::Signaled(_, sig, _)) => {
            tracing::warn!("intermediate process killed with signal: {sig}")
        }
        Ok(_) => (),
        Err(nix::errno::Errno::ECHILD) => {
            // This is safe because intermediate_process and main_process check if the process is
            // finished by piping instead of exit code.
            tracing::warn!("intermediate process already reaped");
        }
        Err(err) => return Err(ProcessError::WaitIntermediateProcess(err)),
    };

    Ok((init_pid, need_to_clean_up_intel_rdt_subdirectory))
}

fn setup_mapping(config: &UserNamespaceConfig, pid: Pid) -> Result<()> {
    tracing::debug!("write mapping for pid {:?}", pid);
    if !config.privileged {
        // The main process is running as an unprivileged user and cannot write the mapping
        // until "deny" has been written to setgroups. See CVE-2014-8989.
        std::fs::write(format!("/proc/{pid}/setgroups"), "deny")
            .map_err(ProcessError::SetGroupsDeny)?;
    }

    config.write_uid_mapping(pid).map_err(|err| {
        tracing::error!("failed to write uid mapping for pid {:?}: {}", pid, err);
        err
    })?;
    config.write_gid_mapping(pid).map_err(|err| {
        tracing::error!("failed to write gid mapping for pid {:?}: {}", pid, err);
        err
    })?;
    Ok(())
}

/// Moves configured network devices from the host to the container's network namespace.
/// This function waits for the init process to join its namespace, then transfers each
/// configured device while preserving network addresses. Returns early if the container
/// runs in the host network namespace.
fn move_network_devices_to_container(
    linux: &Linux,
    init_pid: Pid,
    main_receiver: &mut channel::MainReceiver,
    init_sender: &mut channel::InitSender,
) -> Result<()> {
    // Early return if there are no network devices to move
    let devices = match linux.net_devices() {
        Some(devs) if !devs.is_empty() => devs,
        _ => return Ok(()),
    };

    if let Some(namespaces) = linux.namespaces() {
        // network devices are not moved for containers running in the host network.
        let net_ns = match namespaces
            .iter()
            .find(|ns| ns.typ() == LinuxNamespaceType::Network)
        {
            Some(ns) => ns,
            None => return Ok(()),
        };

        // Wait for the init process to signal that it has joined the network namespace
        // and is ready for network device setup
        main_receiver.wait_for_network_setup_ready()?;

        // the container init process has already joined the provided net namespace,
        // so we can use the process's net ns path directly.
        let default_ns_path = PathBuf::from(format!("/proc/{}/ns/net", init_pid.as_raw()));
        let ns_path = net_ns.path().as_deref().unwrap_or(&default_ns_path);

        // Open the network namespace file and validate it exists before moving devices
        let netns_file = File::open(ns_path).map_err(|err| {
            tracing::error!(
                "failed to open network namespace at {}: {}",
                ns_path.display(),
                err
            );
            ProcessError::Network(err.into())
        })?;
        let netns_fd = netns_file.as_raw_fd();

        // If moving any of the network devices fails, we return an error immediately.
        // The runtime spec requires that the kernel handles moving back any devices
        // that were successfully moved before the failure occurred.
        // See: https://github.com/opencontainers/runtime-spec/blob/27cb0027fd92ef81eda1ea3a8153b8337f56d94a/config-linux.md#namespace-lifecycle-and-container-termination
        let addrs_map = devices
            .iter()
            .map(|(name, net_dev)| {
                let addrs = dev_change_net_namespace(name, netns_fd, net_dev).map_err(|err| {
                    tracing::error!("failed to dev_change_net_namespace: {}", err);
                    err
                })?;
                Ok((name.clone(), addrs))
            })
            .collect::<Result<HashMap<String, Vec<crate::network::cidr::CidrAddress>>>>()?;
        init_sender.move_network_device(addrs_map)?;
    }

    Ok(())
}

#[cfg(test)]
mod tests {
    use std::fs;

    use anyhow::Result;
    use nix::sched::{CloneFlags, unshare};
    use nix::unistd::{self, getgid, getuid};
    use oci_spec::runtime::LinuxIdMappingBuilder;
    use serial_test::serial;

    use super::*;
    use crate::process::channel::{intermediate_channel, main_channel};
    use crate::user_ns::UserNamespaceIDMapper;

    #[test]
    #[serial]
    fn setup_uid_mapping_should_succeed() -> Result<()> {
        let uid_mapping = LinuxIdMappingBuilder::default()
            .host_id(getuid())
            .container_id(0u32)
            .size(1u32)
            .build()?;
        let uid_mappings = vec![uid_mapping];
        let tmp = tempfile::tempdir()?;
        let id_mapper = UserNamespaceIDMapper::new_test(tmp.path().to_path_buf());
        let ns_config = UserNamespaceConfig {
            uid_mappings: Some(uid_mappings),
            privileged: true,
            id_mapper: id_mapper.clone(),
            ..Default::default()
        };
        let (mut parent_sender, mut parent_receiver) = main_channel()?;
        let (mut child_sender, mut child_receiver) = intermediate_channel()?;
        match unsafe { unistd::fork()? } {
            unistd::ForkResult::Parent { child } => {
                parent_receiver.wait_for_mapping_request()?;
                parent_receiver.close()?;

                // In test, we fake the uid path in /proc/{pid}/uid_map, so we
                // need to ensure the path exists before we write the mapping.
                // The path requires the pid we use, so we can only do do after
                // obtaining the child pid here.
                id_mapper.ensure_uid_path(&child)?;
                setup_mapping(&ns_config, child)?;
                let line = fs::read_to_string(id_mapper.get_uid_path(&child))?;
                let split_lines = line.split_whitespace();
                for (act, expect) in split_lines.zip([
                    uid_mapping.container_id().to_string(),
                    uid_mapping.host_id().to_string(),
                    uid_mapping.size().to_string(),
                ]) {
                    assert_eq!(act, expect);
                }
                child_sender.mapping_written()?;
                child_sender.close()?;
            }
            unistd::ForkResult::Child => {
                prctl::set_dumpable(true).unwrap();
                unshare(CloneFlags::CLONE_NEWUSER)?;
                parent_sender.identifier_mapping_request()?;
                parent_sender.close()?;
                child_receiver.wait_for_mapping_ack()?;
                child_receiver.close()?;
                std::process::exit(0);
            }
        }
        Ok(())
    }

    #[test]
    #[serial]
    fn setup_gid_mapping_should_succeed() -> Result<()> {
        let gid_mapping = LinuxIdMappingBuilder::default()
            .host_id(getgid())
            .container_id(0u32)
            .size(1u32)
            .build()?;
        let gid_mappings = vec![gid_mapping];
        let tmp = tempfile::tempdir()?;
        let id_mapper = UserNamespaceIDMapper::new_test(tmp.path().to_path_buf());
        let ns_config = UserNamespaceConfig {
            gid_mappings: Some(gid_mappings),
            id_mapper: id_mapper.clone(),
            ..Default::default()
        };
        let (mut parent_sender, mut parent_receiver) = main_channel()?;
        let (mut child_sender, mut child_receiver) = intermediate_channel()?;
        match unsafe { unistd::fork()? } {
            unistd::ForkResult::Parent { child } => {
                parent_receiver.wait_for_mapping_request()?;
                parent_receiver.close()?;

                // In test, we fake the gid path in /proc/{pid}/gid_map, so we
                // need to ensure the path exists before we write the mapping.
                // The path requires the pid we use, so we can only do do after
                // obtaining the child pid here.
                id_mapper.ensure_gid_path(&child)?;
                setup_mapping(&ns_config, child)?;
                let line = fs::read_to_string(id_mapper.get_gid_path(&child))?;
                let split_lines = line.split_whitespace();
                for (act, expect) in split_lines.zip([
                    gid_mapping.container_id().to_string(),
                    gid_mapping.host_id().to_string(),
                    gid_mapping.size().to_string(),
                ]) {
                    assert_eq!(act, expect);
                }
                assert_eq!(
                    fs::read_to_string(format!("/proc/{}/setgroups", child.as_raw()))?,
                    "deny\n",
                );
                child_sender.mapping_written()?;
                child_sender.close()?;
            }
            unistd::ForkResult::Child => {
                prctl::set_dumpable(true).unwrap();
                unshare(CloneFlags::CLONE_NEWUSER)?;
                parent_sender.identifier_mapping_request()?;
                parent_sender.close()?;
                child_receiver.wait_for_mapping_ack()?;
                child_receiver.close()?;
                std::process::exit(0);
            }
        }
        Ok(())
    }
}