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/* -*- c++ -*- */
/*
* Copyright 2008 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 <http://www.gnu.org/licenses/>.
*/
/*!
* setuid root program that opens a socket using (PF_PACKET, SOCK_RAW,
* htons(0xBEEF)), and sends the resulting file descriptor by way of
* of the file descriptor specified as the first command line argument.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <sys/types.h>
#include <sys/socket.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#elif defined(HAVE_NETINET_IN_H)
#include <netinet/in.h>
#endif
ssize_t
write_fd(int fd, const void *ptr, size_t nbytes, int sendfd)
{
struct msghdr msg;
struct iovec iov[1];
#ifdef HAVE_STRUCT_MSGHDR_MSG_CONTROL
union {
struct cmsghdr cm;
char control[CMSG_SPACE(sizeof(int))];
} control_un;
struct cmsghdr *cmptr;
msg.msg_control = control_un.control;
msg.msg_controllen = sizeof(control_un.control);
cmptr = CMSG_FIRSTHDR(&msg);
cmptr->cmsg_len = CMSG_LEN(sizeof(int));
cmptr->cmsg_level = SOL_SOCKET;
cmptr->cmsg_type = SCM_RIGHTS;
*((int *) CMSG_DATA(cmptr)) = sendfd;
#else
msg.msg_accrights = (char *) &sendfd;
msg.msg_accrightslen = sizeof(int);
#endif
msg.msg_name = NULL;
msg.msg_namelen = 0;
iov[0].iov_base = const_cast<void *>(ptr);
iov[0].iov_len = nbytes;
msg.msg_iov = iov;
msg.msg_iovlen = 1;
return sendmsg(fd, &msg, 0);
}
bool
reset_eids()
{
if (setgid(getgid()) < 0){
perror("setguid");
return false;
}
if (setuid(getuid()) < 0){
perror("setuid");
return false;
}
return true;
}
static void
usage()
{
fprintf(stderr, "usage: usrp2_socket_opener file-descriptor\n");
exit(1);
}
int
main(int argc, char **argv)
{
if (argc != 2)
usage();
char *endptr;
int unix_domain_fd = strtol(argv[1], &endptr, 0);
if (*endptr != 0)
usage();
// FIXME get client credentials from unix_domain_fd using SCM_CREDENTIALS
// open the raw socket
int socket_fd = socket(PF_PACKET, SOCK_RAW, htons(0xBEEF));
if (socket_fd == -1){
perror("socket(PF_PACKET, SOCK_RAW, htons(0xBEEF))");
// printf("errno = %d\n", errno);
if (errno == EACCES || errno == ESPIPE){
fprintf(stderr, "usrp2_socket_opener must be setuid root to open the socket using SOCK_RAW.\n");
fprintf(stderr, "Running as root, please execute: \n");
fprintf(stderr, " # chown root:usrp usrp2_socket_opener\n");
fprintf(stderr, " # chmod 04750 usrp2_socket_opener\n");
}
exit(2);
}
// drop privs
if (!reset_eids()){
fprintf(stderr, "Can't drop root permissions\n");
exit(3);
}
if (write_fd(unix_domain_fd, "", 1, socket_fd) != 1){
perror("write_fd");
exit(4);
}
return 0;
}
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