/*
 * 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/stat.h>

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

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

static int __ivaliduser_sa(FILE *, struct sockaddr *, socklen_t,
            const char *, const char *);
static int __icheckhost(struct sockaddr *, socklen_t, const char *);
static char *__gethostloop(struct sockaddr *, socklen_t);
static int iruserok_sa(const void *, int, int, const char *, const char *);

int
ruserok(const char *rhost, int superuser, const char *ruser, const char *luser)
{
        struct addrinfo hints, *res, *r;
        int error;

        memset(&hints, 0, sizeof(hints));
        hints.ai_family = PF_UNSPEC;
        hints.ai_socktype = SOCK_DGRAM; /*dummy*/
        error = getaddrinfo(rhost, "0", &hints, &res);
        if (error)
                return (-1);

        for (r = res; r; r = r->ai_next) {
                if (iruserok_sa(r->ai_addr, r->ai_addrlen, superuser, ruser,
                    luser) == 0) {
                        freeaddrinfo(res);
                        return (0);
                }
        }
        freeaddrinfo(res);
        return (-1);
}

int
iruserok_sa(const void *raddr, int rlen, int superuser, const char *ruser,
    const char *luser)
{
        struct sockaddr *sa;
        char *cp;
        struct stat sbuf;
        struct passwd pwstore, *pwd;
        FILE *hostf;
        uid_t uid;
        int first;
        char pbuf[PATH_MAX], pwbuf[_PW_BUF_LEN];

        sa = (struct sockaddr *)raddr;
        first = 1;
        hostf = superuser ? NULL : fopen(_PATH_HEQUIV, "re");
again:
        if (hostf) {
                if (__ivaliduser_sa(hostf, sa, rlen, luser, ruser) == 0) {
                        (void)fclose(hostf);
                        return (0);
                }
                (void)fclose(hostf);
        }
        if (first == 1) {
                int len;

                first = 0;
                pwd = NULL;
                getpwnam_r(luser, &pwstore, pwbuf, sizeof(pwbuf), &pwd);
                if (pwd == NULL)
                        return (-1);
                len = snprintf(pbuf, sizeof pbuf, "%s/.rhosts", pwd->pw_dir);
                if (len < 0 || len >= sizeof pbuf)
                        return (-1);

                /*
                 * Change effective uid while opening .rhosts.  If root and
                 * reading an NFS mounted file system, can't read files that
                 * are protected read/write owner only.
                 */
                uid = geteuid();
                (void)seteuid(pwd->pw_uid);
                hostf = fopen(pbuf, "re");
                (void)seteuid(uid);

                if (hostf == NULL)
                        return (-1);
                /*
                 * If not a regular file, or is owned by someone other than
                 * user or root or if writeable by anyone but the owner, quit.
                 */
                cp = NULL;
                if (lstat(pbuf, &sbuf) == -1)
                        cp = ".rhosts lstat failed";
                else if (!S_ISREG(sbuf.st_mode))
                        cp = ".rhosts not regular file";
                else if (fstat(fileno(hostf), &sbuf) == -1)
                        cp = ".rhosts fstat failed";
                else if (sbuf.st_uid && sbuf.st_uid != pwd->pw_uid)
                        cp = "bad .rhosts owner";
                else if (sbuf.st_mode & (S_IWGRP|S_IWOTH))
                        cp = ".rhosts writable by other than owner";
                /* If there were any problems, quit. */
                if (cp) {
                        (void)fclose(hostf);
                        return (-1);
                }
                goto again;
        }
        return (-1);
}

int
__ivaliduser_sa(FILE *hostf, struct sockaddr *raddr, socklen_t salen,
    const char *luser, const char *ruser)
{
        char *user, *p;
        char *buf;
        const char *auser, *ahost;
        int hostok, userok;
        char *rhost = (char *)-1;
        char domain[HOST_NAME_MAX+1];
        size_t buflen;

        getdomainname(domain, sizeof(domain));

        while ((buf = fgetln(hostf, &buflen))) {
                p = buf;
                if (*p == '#')
                        continue;
                while (p < buf + buflen && *p != '\n' && *p != ' ' && *p != '\t') {
                        if (!isprint((unsigned char)*p))
                                goto bail;
                        *p = isupper((unsigned char)*p) ?
                            tolower((unsigned char)*p) : *p;
                        p++;
                }
                if (p >= buf + buflen)
                        continue;
                if (*p == ' ' || *p == '\t') {
                        *p++ = '\0';
                        while (p < buf + buflen && (*p == ' ' || *p == '\t'))
                                p++;
                        if (p >= buf + buflen)
                                continue;
                        user = p;
                        while (p < buf + buflen && *p != '\n' && *p != ' ' &&
                            *p != '\t') {
                                if (!isprint((unsigned char)*p))
                                        goto bail;
                                p++;
                        }
                } else
                        user = p;
                *p = '\0';

                if (p == buf)
                        continue;

                auser = *user ? user : luser;
                ahost = buf;

                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.)
                 */
                if (ahost[0] == '+')
                        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 = __icheckhost(raddr, salen, &ahost[1]);
                                break;
                        }
                else if (ahost[0] == '-')
                        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 = -__icheckhost(raddr, salen, &ahost[1]);
                                break;
                        }
                else
                        hostok = __icheckhost(raddr, salen, ahost);


                if (auser[0] == '+')
                        switch (auser[1]) {
                        case '\0':
                                userok = 1;
                                break;
                        case '@':
                                userok = innetgr(&auser[2], NULL, ruser,
                                    domain);
                                break;
                        default:
                                userok = strcmp(ruser, &auser[1]) ? 0 : 1;
                                break;
                        }
                else if (auser[0] == '-')
                        switch (auser[1]) {
                        case '\0':
                                userok = -1;
                                break;
                        case '@':
                                userok = -innetgr(&auser[2], NULL, ruser,
                                    domain);
                                break;
                        default:
                                userok = strcmp(ruser, &auser[1]) ? 0 : -1;
                                break;
                        }
                else
                        userok = strcmp(ruser, auser) ? 0 : 1;

                /* Check if one component did not match */
                if (hostok == 0 || userok == 0)
                        continue;

                /* Check if we got a forbidden pair */
                if (userok <= -1 || hostok <= -1)
                        return (-1);

                /* Check if we got a valid pair */
                if (hostok >= 1 && userok >= 1)
                        return (0);
        }
bail:
        return (-1);
}

/*
 * Returns "true" 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
__icheckhost(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 (strcmp(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 (strcmp(h1, h2) == 0) {
                        freeaddrinfo(res);
                        return (remotehost);
                }
        }

        /*
         * either the DNS administrator has made a configuration
         * mistake, or someone has attempted to spoof us
         */
        freeaddrinfo(res);
        return (NULL);
}