/*
 * Copyright (c) 1995, 1996, 1998 Theo de Raadt.  All rights reserved.
 * Copyright (c) 1983, 1993, 1994
 *      The Regents of the University of California.  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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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 <sys/socket.h>
#include <sys/types.h>

#include <netinet/in.h>
#include <arpa/inet.h>

#include <ctype.h>
#include <limits.h>
#include <netdb.h>
#include <netgroup.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>

static int checkhost(struct sockaddr *, socklen_t, const char *);
static char *gethostloop(struct sockaddr *, socklen_t);

/*
 * Check whether the specified addr is listed in hostf.
 * Returns 0 if allowed, else -1.
 */
int
allowedhost(FILE *hostf, struct sockaddr *raddr, socklen_t salen)
{
        char *cp, *ep, *line = NULL;
        char *ahost, *rhost = (char *)-1;
        char domain[HOST_NAME_MAX+1];
        size_t linesize = 0;
        ssize_t linelen;
        int hostok = 0;

        getdomainname(domain, sizeof(domain));

        while ((linelen = getline(&line, &linesize, hostf)) != -1) {
                cp = line;
                ep = line + linelen;
                if (*cp == '#')
                        continue;
                while (cp < ep && !isspace((unsigned char)*cp)) {
                        if (!isprint((unsigned char)*cp))
                                goto bail;
                        *cp = isupper((unsigned char)*cp) ?
                            tolower((unsigned char)*cp) : *cp;
                        cp++;
                }
                if (cp == line)
                        continue;
                *cp = '\0';

                ahost = line;
                if (strlen(ahost) > HOST_NAME_MAX)
                        continue;

                /*
                 * innetgr() must lookup a hostname (we do not attempt
                 * to change the semantics so that netgroups may have
                 * #.#.#.# addresses in the list.)
                 */
                switch (ahost[0]) {
                case '+':
                case '-':
                        switch (ahost[1]) {
                        case '\0':
                                hostok = 1;
                                break;
                        case '@':
                                if (rhost == (char *)-1)
                                        rhost = gethostloop(raddr, salen);
                                hostok = 0;
                                if (rhost)
                                        hostok = innetgr(&ahost[2], rhost,
                                            NULL, domain);
                                break;
                        default:
                                hostok = checkhost(raddr, salen, &ahost[1]);
                                break;
                        }
                        if (ahost[0] == '-')
                                hostok = -hostok;
                        break;
                default:
                        hostok = checkhost(raddr, salen, ahost);
                        break;
                }

                /* Check if we got a match (positive or negative). */
                if (hostok != 0)
                        break;
        }
bail:
        free(line);
        return (hostok > 0 ? 0 : -1);
}

/*
 * Returns 1 if match, 0 if no match.  If we do not find any
 * semblance of an A->PTR->A loop, allow a simple #.#.#.# match to work.
 */
static int
checkhost(struct sockaddr *raddr, socklen_t salen, const char *lhost)
{
        struct addrinfo hints, *res, *r;
        char h1[NI_MAXHOST], h2[NI_MAXHOST];
        int error;
        const int niflags = NI_NUMERICHOST;

        h1[0] = '\0';
        if (getnameinfo(raddr, salen, h1, sizeof(h1), NULL, 0, niflags) != 0)
                return (0);

        /* Resolve laddr into sockaddr */
        memset(&hints, 0, sizeof(hints));
        hints.ai_family = raddr->sa_family;
        hints.ai_socktype = SOCK_DGRAM; /*dummy*/
        res = NULL;
        error = getaddrinfo(lhost, "0", &hints, &res);
        if (error)
                return (0);

        /*
         * Try string comparisons between raddr and laddr.
         */
        for (r = res; r; r = r->ai_next) {
                h2[0] = '\0';
                if (getnameinfo(r->ai_addr, r->ai_addrlen, h2, sizeof(h2),
                    NULL, 0, niflags) != 0)
                        continue;
                if (strcasecmp(h1, h2) == 0) {
                        freeaddrinfo(res);
                        return (1);
                }
        }

        /* No match. */
        freeaddrinfo(res);
        return (0);
}

/*
 * Return the hostname associated with the supplied address.
 * Do a reverse lookup as well for security. If a loop cannot
 * be found, pack the result of inet_ntoa() into the string.
 */
static char *
gethostloop(struct sockaddr *raddr, socklen_t salen)
{
        static char remotehost[NI_MAXHOST];
        char h1[NI_MAXHOST], h2[NI_MAXHOST];
        struct addrinfo hints, *res, *r;
        int error;
        const int niflags = NI_NUMERICHOST;

        h1[0] = remotehost[0] = '\0';
        if (getnameinfo(raddr, salen, remotehost, sizeof(remotehost),
            NULL, 0, NI_NAMEREQD) != 0)
                return (NULL);
        if (getnameinfo(raddr, salen, h1, sizeof(h1), NULL, 0, niflags) != 0)
                return (NULL);

        /*
         * Look up the name and check that the supplied
         * address is in the list
         */
        memset(&hints, 0, sizeof(hints));
        hints.ai_family = raddr->sa_family;
        hints.ai_socktype = SOCK_DGRAM; /*dummy*/
        hints.ai_flags = AI_CANONNAME;
        res = NULL;
        error = getaddrinfo(remotehost, "0", &hints, &res);
        if (error)
                return (NULL);

        for (r = res; r; r = r->ai_next) {
                h2[0] = '\0';
                if (getnameinfo(r->ai_addr, r->ai_addrlen, h2, sizeof(h2),
                    NULL, 0, niflags) != 0)
                        continue;
                if (strcasecmp(h1, h2) == 0) {
                        freeaddrinfo(res);
                        return (remotehost);
                }
        }

        /*
         * Either the DNS administrator has made a configuration
         * mistake, or someone has attempted to spoof us.
         */
        syslog(LOG_NOTICE, "lpd: address %s not listed for host %s",
            h1, res->ai_canonname ? res->ai_canonname : remotehost);
        freeaddrinfo(res);
        return (NULL);
}

#ifdef DEBUG
int
main(int argc, char *argv[])
{
        struct addrinfo hints;
        int i;

        memset(&hints, 0, sizeof(hints));
        hints.ai_family = PF_UNSPEC;
        hints.ai_socktype = SOCK_STREAM;

        for (i = 1; i < argc; i++) {
                struct addrinfo *res0;
                int error = getaddrinfo(argv[i], NULL, &hints, &res0);
                if (error) {
                        printf("%s: %s\n", argv[i], gai_strerror(error));
                        continue;
                }
                error = allowedhost(stdin, res0->ai_addr, res0->ai_addrlen);
                printf("%s: %s\n", argv[i], error ? "denied" : "allowed");
        }
        exit(0);
}
#endif /* DEBUG */