ipc_listener.cpp

/* SPDX-License-Identifier: MPL-2.0 */

#include "precompiled.hpp"
#include "ipc_listener.hpp"

#if defined ZMQ_HAVE_IPC

#include <new>

#include <string.h>

#include "ipc_address.hpp"
#include "io_thread.hpp"
#include "config.hpp"
#include "err.hpp"
#include "ip.hpp"
#include "socket_base.hpp"
#include "address.hpp"

#ifdef ZMQ_HAVE_WINDOWS
#ifdef ZMQ_IOTHREAD_POLLER_USE_SELECT
#error On Windows, IPC does not work with POLLER=select, use POLLER=epoll instead, or disable IPC transport
#endif

#include <afunix.h>
#include <direct.h>

#define rmdir rmdir_utf8
#define unlink unlink_utf8

#else
#include <unistd.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <sys/un.h>
#endif

#ifdef ZMQ_HAVE_LOCAL_PEERCRED
#include <sys/types.h>
#include <sys/ucred.h>
#endif
#ifdef ZMQ_HAVE_SO_PEERCRED
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
#if defined ZMQ_HAVE_OPENBSD
#define ucred sockpeercred
#endif
#endif

zmq::ipc_listener_t::ipc_listener_t (io_thread_t *io_thread_,
                                     socket_base_t *socket_,
                                     const options_t &options_) :
    stream_listener_base_t (io_thread_, socket_, options_), _has_file (false)
{
}

void zmq::ipc_listener_t::in_event ()
{
    const fd_t fd = accept ();

    //  If connection was reset by the peer in the meantime, just ignore it.
    //  TODO: Handle specific errors like ENFILE/EMFILE etc.
    if (fd == retired_fd) {
        _socket->event_accept_failed (
          make_unconnected_bind_endpoint_pair (_endpoint), zmq_errno ());
        return;
    }

    //  Create the engine object for this connection.
    create_engine (fd);
}

std::string
zmq::ipc_listener_t::get_socket_name (zmq::fd_t fd_,
                                      socket_end_t socket_end_) const
{
    return zmq::get_socket_name<ipc_address_t> (fd_, socket_end_);
}

int zmq::ipc_listener_t::set_local_address (const char *addr_)
{
    //  Create addr on stack for auto-cleanup
    std::string addr (addr_);

    //  Allow wildcard file
    if (options.use_fd == -1 && addr[0] == '*') {
        if (create_ipc_wildcard_address (_tmp_socket_dirname, addr) < 0) {
            return -1;
        }
    }

    //  Get rid of the file associated with the UNIX domain socket that
    //  may have been left behind by the previous run of the application.
    //  MUST NOT unlink if the FD is managed by the user, or it will stop
    //  working after the first client connects. The user will take care of
    //  cleaning up the file after the service is stopped.
    if (options.use_fd == -1) {
        ::unlink (addr.c_str ());
    }
    _filename.clear ();

    //  Initialise the address structure.
    ipc_address_t address;
    int rc = address.resolve (addr.c_str ());
    if (rc != 0) {
        if (!_tmp_socket_dirname.empty ()) {
            // We need to preserve errno to return to the user
            const int tmp_errno = errno;
            ::rmdir (_tmp_socket_dirname.c_str ());
            _tmp_socket_dirname.clear ();
            errno = tmp_errno;
        }
        return -1;
    }

    address.to_string (_endpoint);

    if (options.use_fd != -1) {
        _s = options.use_fd;
    } else {
        //  Create a listening socket.
        _s = open_socket (AF_UNIX, SOCK_STREAM, 0);
        if (_s == retired_fd) {
            if (!_tmp_socket_dirname.empty ()) {
                // We need to preserve errno to return to the user
                const int tmp_errno = errno;
                ::rmdir (_tmp_socket_dirname.c_str ());
                _tmp_socket_dirname.clear ();
                errno = tmp_errno;
            }
            return -1;
        }

        //  Bind the socket to the file path.
        rc = bind (_s, const_cast<sockaddr *> (address.addr ()),
                   address.addrlen ());
        if (rc != 0)
            goto error;

        //  Listen for incoming connections.
        rc = listen (_s, options.backlog);
        if (rc != 0)
            goto error;
    }

    _filename = ZMQ_MOVE (addr);
    _has_file = true;

    _socket->event_listening (make_unconnected_bind_endpoint_pair (_endpoint),
                              _s);
    return 0;

error:
    const int err = errno;
    close ();
    errno = err;
    return -1;
}

int zmq::ipc_listener_t::close ()
{
    zmq_assert (_s != retired_fd);
    const fd_t fd_for_event = _s;
#ifdef ZMQ_HAVE_WINDOWS
    int rc = closesocket (_s);
    wsa_assert (rc != SOCKET_ERROR);
#else
    int rc = ::close (_s);
    errno_assert (rc == 0);
#endif

    _s = retired_fd;

    if (_has_file && options.use_fd == -1) {
        if (!_tmp_socket_dirname.empty ()) {
            //  TODO review this behaviour, it is inconsistent with the use of
            //  unlink in open since 656cdb959a7482c45db979c1d08ede585d12e315;
            //  however, we must at least remove the file before removing the
            //  directory, otherwise it will always fail
            rc = ::unlink (_filename.c_str ());

            if (rc == 0) {
                rc = ::rmdir (_tmp_socket_dirname.c_str ());
                _tmp_socket_dirname.clear ();
            }
        }

        if (rc != 0) {
            _socket->event_close_failed (
              make_unconnected_bind_endpoint_pair (_endpoint), zmq_errno ());
            return -1;
        }
    }

    _socket->event_closed (make_unconnected_bind_endpoint_pair (_endpoint),
                           fd_for_event);
    return 0;
}

#if defined ZMQ_HAVE_SO_PEERCRED

bool zmq::ipc_listener_t::filter (fd_t sock_)
{
    if (options.ipc_uid_accept_filters.empty ()
        && options.ipc_pid_accept_filters.empty ()
        && options.ipc_gid_accept_filters.empty ())
        return true;

    struct ucred cred;
    socklen_t size = sizeof (cred);

    if (getsockopt (sock_, SOL_SOCKET, SO_PEERCRED, &cred, &size))
        return false;
    if (options.ipc_uid_accept_filters.find (cred.uid)
          != options.ipc_uid_accept_filters.end ()
        || options.ipc_gid_accept_filters.find (cred.gid)
             != options.ipc_gid_accept_filters.end ()
        || options.ipc_pid_accept_filters.find (cred.pid)
             != options.ipc_pid_accept_filters.end ())
        return true;

    const struct passwd *pw;
    const struct group *gr;

    if (!(pw = getpwuid (cred.uid)))
        return false;
    for (options_t::ipc_gid_accept_filters_t::const_iterator
           it = options.ipc_gid_accept_filters.begin (),
           end = options.ipc_gid_accept_filters.end ();
         it != end; it++) {
        if (!(gr = getgrgid (*it)))
            continue;
        for (char **mem = gr->gr_mem; *mem; mem++) {
            if (!strcmp (*mem, pw->pw_name))
                return true;
        }
    }
    return false;
}

#elif defined ZMQ_HAVE_LOCAL_PEERCRED

bool zmq::ipc_listener_t::filter (fd_t sock_)
{
    if (options.ipc_uid_accept_filters.empty ()
        && options.ipc_gid_accept_filters.empty ())
        return true;

    struct xucred cred;
    socklen_t size = sizeof (cred);

    if (getsockopt (sock_, 0, LOCAL_PEERCRED, &cred, &size))
        return false;
    if (cred.cr_version != XUCRED_VERSION)
        return false;
    if (options.ipc_uid_accept_filters.find (cred.cr_uid)
        != options.ipc_uid_accept_filters.end ())
        return true;
    for (int i = 0; i < cred.cr_ngroups; i++) {
        if (options.ipc_gid_accept_filters.find (cred.cr_groups[i])
            != options.ipc_gid_accept_filters.end ())
            return true;
    }

    return false;
}

#endif

zmq::fd_t zmq::ipc_listener_t::accept ()
{
    //  Accept one connection and deal with different failure modes.
    //  The situation where connection cannot be accepted due to insufficient
    //  resources is considered valid and treated by ignoring the connection.
    zmq_assert (_s != retired_fd);
#if defined ZMQ_HAVE_SOCK_CLOEXEC && defined HAVE_ACCEPT4
    fd_t sock = ::accept4 (_s, NULL, NULL, SOCK_CLOEXEC);
#else
    struct sockaddr_storage ss;
    memset (&ss, 0, sizeof (ss));
#if defined ZMQ_HAVE_HPUX || defined ZMQ_HAVE_VXWORKS
    int ss_len = sizeof (ss);
#else
    socklen_t ss_len = sizeof (ss);
#endif

    const fd_t sock =
      ::accept (_s, reinterpret_cast<struct sockaddr *> (&ss), &ss_len);
#endif
    if (sock == retired_fd) {
#if defined ZMQ_HAVE_WINDOWS
        const int last_error = WSAGetLastError ();
        wsa_assert (last_error == WSAEWOULDBLOCK || last_error == WSAECONNRESET
                    || last_error == WSAEMFILE || last_error == WSAENOBUFS);
#else
        errno_assert (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR
                      || errno == ECONNABORTED || errno == EPROTO
                      || errno == ENFILE);
#endif
        return retired_fd;
    }

    make_socket_noninheritable (sock);

    // IPC accept() filters
#if defined ZMQ_HAVE_SO_PEERCRED || defined ZMQ_HAVE_LOCAL_PEERCRED
    if (!filter (sock)) {
        int rc = ::close (sock);
        errno_assert (rc == 0);
        return retired_fd;
    }
#endif

    if (zmq::set_nosigpipe (sock)) {
#ifdef ZMQ_HAVE_WINDOWS
        const int rc = closesocket (sock);
        wsa_assert (rc != SOCKET_ERROR);
#else
        int rc = ::close (sock);
        errno_assert (rc == 0);
#endif
        return retired_fd;
    }

    return sock;
}

#endif