/*      $OpenBSD: bindresvport.c,v 1.19 2019/06/28 13:32:42 deraadt Exp $       */

/*
 * Copyright 1996, Jason Downs.  All rights reserved.
 * Copyright 1998, Theo de Raadt.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

/*
 * Bind a socket to a privileged IP port
 */
int
bindresvport(int sd, struct sockaddr_in *sin)
{
        return bindresvport_sa(sd, (struct sockaddr *)sin);
}
DEF_WEAK(bindresvport);

/*
 * Bind a socket to a privileged port for whatever protocol.
 */
int
bindresvport_sa(int sd, struct sockaddr *sa)
{
        int old, error, af;
        struct sockaddr_storage myaddr;
        struct sockaddr_in *sin;
        struct sockaddr_in6 *sin6;
        int proto, portrange, portlow;
        u_int16_t port;
        socklen_t salen;

        if (sa == NULL) {
                salen = sizeof(myaddr);
                sa = (struct sockaddr *)&myaddr;

                if (getsockname(sd, sa, &salen) == -1)
                        return -1;      /* errno is correctly set */

                af = sa->sa_family;
                memset(&myaddr, 0, salen);
        } else
                af = sa->sa_family;

        if (af == AF_INET) {
                proto = IPPROTO_IP;
                portrange = IP_PORTRANGE;
                portlow = IP_PORTRANGE_LOW;
                sin = (struct sockaddr_in *)sa;
                salen = sizeof(struct sockaddr_in);
                port = sin->sin_port;
        } else if (af == AF_INET6) {
                proto = IPPROTO_IPV6;
                portrange = IPV6_PORTRANGE;
                portlow = IPV6_PORTRANGE_LOW;
                sin6 = (struct sockaddr_in6 *)sa;
                salen = sizeof(struct sockaddr_in6);
                port = sin6->sin6_port;
        } else {
                errno = EPFNOSUPPORT;
                return (-1);
        }
        sa->sa_family = af;
        sa->sa_len = salen;

        if (port == 0) {
                socklen_t oldlen = sizeof(old);

                error = getsockopt(sd, proto, portrange, &old, &oldlen);
                if (error == -1)
                        return (error);

                error = setsockopt(sd, proto, portrange, &portlow,
                    sizeof(portlow));
                if (error == -1)
                        return (error);
        }

        error = bind(sd, sa, salen);

        if (port == 0) {
                int saved_errno = errno;

                if (error) {
                        if (setsockopt(sd, proto, portrange, &old,
                            sizeof(old)) == -1)
                                errno = saved_errno;
                        return (error);
                }

                if (sa != (struct sockaddr *)&myaddr) {
                        /* Hmm, what did the kernel assign... */
                        if (getsockname(sd, sa, &salen) == -1)
                                errno = saved_errno;
                        return (error);
                }
        }
        return (error);
}
DEF_WEAK(bindresvport_sa);