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// OpenVPN -- An application to securely tunnel IP networks
// over a single port, with support for SSL/TLS-based
// session authentication and key exchange,
// packet encryption, packet authentication, and
// packet compression.
//
// Copyright (C) 2012-2022 OpenVPN Inc.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License Version 3
// as published by the Free Software Foundation.
//
// 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program in the COPYING file.
// If not, see <http://www.gnu.org/licenses/>.
// Transmit/Receive file descriptors over a unix domain socket
#ifndef OPENVPN_COMMON_XMITFD_H
#define OPENVPN_COMMON_XMITFD_H
#include <string>
#include <memory>
#include <cstring>
#include <sys/types.h>
#include <sys/socket.h>
#include <poll.h>
#include <errno.h>
#include <openvpn/common/exception.hpp>
#include <openvpn/common/strerror.hpp>
namespace openvpn {
class XmitFD
{
public:
OPENVPN_EXCEPTION(xmit_fd_error);
static void xmit_fd(const int sock_fd,
const int payload_fd, // optional (set to -1 to disable)
const std::string &message,
const int timeout_ms)
{
unsigned char buf[CMSG_SPACE(sizeof(payload_fd))];
std::memset(buf, 0, sizeof(buf));
struct iovec io;
io.iov_base = const_cast<char *>(message.c_str());
io.iov_len = message.length();
struct msghdr msg = {0};
msg.msg_iov = &io;
msg.msg_iovlen = 1;
if (payload_fd >= 0)
{
msg.msg_control = buf;
msg.msg_controllen = sizeof(buf);
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN(sizeof(payload_fd));
std::memcpy(CMSG_DATA(cmsg), &payload_fd, sizeof(payload_fd));
msg.msg_controllen = cmsg->cmsg_len;
}
poll_wait(sock_fd, true, timeout_ms);
const ssize_t status = ::sendmsg(sock_fd, &msg, 0);
if (status < 0)
{
const int eno = errno;
OPENVPN_THROW(xmit_fd_error, "xmit_fd: " << strerror_str(eno));
}
else if (status != static_cast<ssize_t>(message.length()))
OPENVPN_THROW(xmit_fd_error, "xmit_fd: unexpected send size");
}
static int recv_fd(const int sock_fd,
std::string &message,
const size_t buf_size,
const int timeout_ms)
{
struct msghdr msg = {0};
std::unique_ptr<char[]> buf(new char[buf_size]);
struct iovec io = {.iov_base = buf.get(), .iov_len = buf_size};
msg.msg_iov = &io;
msg.msg_iovlen = 1;
unsigned char c_buffer[256];
msg.msg_control = c_buffer;
msg.msg_controllen = sizeof(c_buffer);
poll_wait(sock_fd, false, timeout_ms);
const ssize_t status = ::recvmsg(sock_fd, &msg, 0);
if (status < 0)
{
const int eno = errno;
OPENVPN_THROW(xmit_fd_error, "recv_fd: " << strerror_str(eno));
}
else if (status == 0)
OPENVPN_THROW(xmit_fd_error, "recv_fd: eof");
else if (status > static_cast<ssize_t>(buf_size))
OPENVPN_THROW(xmit_fd_error, "recv_fd: unexpectedly large message");
int fd;
for (struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL; cmsg = CMSG_NXTHDR(&msg, cmsg))
{
if (cmsg->cmsg_len == CMSG_LEN(sizeof(fd))
&& cmsg->cmsg_level == SOL_SOCKET
&& cmsg->cmsg_type == SCM_RIGHTS)
{
std::memcpy(&fd, CMSG_DATA(cmsg), sizeof(fd));
if (fd >= 0)
{
message = std::string(buf.get(), status);
return fd;
}
}
}
OPENVPN_THROW(xmit_fd_error, "recv_fd: no fd in message");
}
private:
static void poll_wait(const int fd,
const bool write,
const int timeout)
{
struct pollfd fds[1];
fds[0].fd = fd;
fds[0].events = write ? POLLOUT : (POLLIN | POLLPRI);
fds[0].revents = 0;
const int status = ::poll(fds, 1, timeout);
if (status < 0)
{
const int eno = errno;
OPENVPN_THROW(xmit_fd_error, "poll_wait: poll failed: " << strerror_str(eno));
}
else if (status == 0)
OPENVPN_THROW(xmit_fd_error, "poll_wait: poll timeout");
else if (status != 1)
OPENVPN_THROW(xmit_fd_error, "poll_wait: poll failed with unexpected return value=" << status);
}
};
} // namespace openvpn
#endif
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