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/* Copyright (C) 2011-2021 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
/* Specification. */
#include "passfd.h"
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/socket.h>
#include "cloexec.h"
/* The code that uses CMSG_FIRSTHDR is enabled on
Linux, Mac OS X, FreeBSD, OpenBSD, NetBSD, AIX, OSF/1, Cygwin.
The code that uses HAVE_STRUCT_MSGHDR_MSG_ACCRIGHTS is enabled on
HP-UX, IRIX, Solaris. */
/* MSG_CMSG_CLOEXEC is defined only on Linux, as of 2011. */
#ifndef MSG_CMSG_CLOEXEC
# define MSG_CMSG_CLOEXEC 0
#endif
#if HAVE_SENDMSG
/* sendfd sends the file descriptor fd along the socket
to a process calling recvfd on the other end.
Return 0 on success, or -1 with errno set in case of error.
*/
int
sendfd (int sock, int fd)
{
char byte = 0;
struct iovec iov;
struct msghdr msg;
# ifdef CMSG_FIRSTHDR
struct cmsghdr *cmsg;
char buf[CMSG_SPACE (sizeof fd)];
# endif
/* send at least one char */
memset (&msg, 0, sizeof msg);
iov.iov_base = &byte;
iov.iov_len = 1;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_name = NULL;
msg.msg_namelen = 0;
# ifdef CMSG_FIRSTHDR
msg.msg_control = buf;
msg.msg_controllen = sizeof buf;
cmsg = CMSG_FIRSTHDR (&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN (sizeof fd);
/* Initialize the payload: */
memcpy (CMSG_DATA (cmsg), &fd, sizeof fd);
msg.msg_controllen = cmsg->cmsg_len;
# elif HAVE_STRUCT_MSGHDR_MSG_ACCRIGHTS
msg.msg_accrights = &fd;
msg.msg_accrightslen = sizeof fd;
# else
errno = ENOSYS;
return -1;
# endif
if (sendmsg (sock, &msg, 0) != iov.iov_len)
return -1;
return 0;
}
#else
int
sendfd (int sock _GL_UNUSED, int fd _GL_UNUSED)
{
errno = ENOSYS;
return -1;
}
#endif
#if HAVE_RECVMSG
/* recvfd receives a file descriptor through the socket.
The flags are a bitmask, possibly including O_CLOEXEC (defined in <fcntl.h>).
Return the fd on success, or -1 with errno set in case of error.
*/
int
recvfd (int sock, int flags)
{
char byte = 0;
struct iovec iov;
struct msghdr msg;
int fd = -1;
ssize_t len;
# ifdef CMSG_FIRSTHDR
struct cmsghdr *cmsg;
char buf[CMSG_SPACE (sizeof fd)];
int flags_recvmsg = flags & O_CLOEXEC ? MSG_CMSG_CLOEXEC : 0;
# endif
if ((flags & ~O_CLOEXEC) != 0)
{
errno = EINVAL;
return -1;
}
/* send at least one char */
memset (&msg, 0, sizeof msg);
iov.iov_base = &byte;
iov.iov_len = 1;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_name = NULL;
msg.msg_namelen = 0;
# ifdef CMSG_FIRSTHDR
msg.msg_control = buf;
msg.msg_controllen = sizeof buf;
cmsg = CMSG_FIRSTHDR (&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN (sizeof fd);
/* Initialize the payload: */
memcpy (CMSG_DATA (cmsg), &fd, sizeof fd);
msg.msg_controllen = cmsg->cmsg_len;
len = recvmsg (sock, &msg, flags_recvmsg);
if (len < 0)
return -1;
cmsg = CMSG_FIRSTHDR (&msg);
/* be paranoiac */
if (len == 0 || cmsg == NULL || cmsg->cmsg_len != CMSG_LEN (sizeof fd)
|| cmsg->cmsg_level != SOL_SOCKET || cmsg->cmsg_type != SCM_RIGHTS)
{
/* fake errno: at end the file is not available */
errno = len ? EACCES : ENOTCONN;
return -1;
}
memcpy (&fd, CMSG_DATA (cmsg), sizeof fd);
/* set close-on-exec flag */
if (!MSG_CMSG_CLOEXEC && (flags & O_CLOEXEC))
{
if (set_cloexec_flag (fd, true) < 0)
{
int saved_errno = errno;
(void) close (fd);
errno = saved_errno;
return -1;
}
}
# elif HAVE_STRUCT_MSGHDR_MSG_ACCRIGHTS
msg.msg_accrights = &fd;
msg.msg_accrightslen = sizeof fd;
if (recvmsg (sock, &msg, 0) < 0)
return -1;
/* set close-on-exec flag */
if (flags & O_CLOEXEC)
{
if (set_cloexec_flag (fd, true) < 0)
{
int saved_errno = errno;
close (fd);
errno = saved_errno;
return -1;
}
}
# else
errno = ENOSYS;
# endif
return fd;
}
#else
int
recvfd (int sock _GL_UNUSED, int flags _GL_UNUSED)
{
errno = ENOSYS;
return -1;
}
#endif
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