1 files changed, 733 insertions, 0 deletions

diff --git a/src/lib/libc/net/rcmd.c b/src/lib/libc/net/rcmd.c
new file mode 100644
index 0000000000..be68c599d8
--- /dev/null
+++ b/src/lib/libc/net/rcmd.c
@@ -0,0 +1,733 @@
+/*
+ * 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. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *      This product includes software developed by the University of
+ *      California, Berkeley and its contributors.
+ *      This product includes software developed by Theo de Raadt.
+ * 4. 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.
+ */
+
+#if defined(LIBC_SCCS) && !defined(lint)
+static char *rcsid = "$OpenBSD: rcmd.c,v 1.43 2002/05/24 21:22:37 deraadt Exp $";
+#endif /* LIBC_SCCS and not lint */
+
+#include <sys/param.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+#include <signal.h>
+#include <fcntl.h>
+#include <netdb.h>
+#include <unistd.h>
+#include <pwd.h>
+#include <errno.h>
+#include <stdio.h>
+#include <ctype.h>
+#include <string.h>
+#include <syslog.h>
+#include <stdlib.h>
+#include <netgroup.h>
+
+int     __ivaliduser(FILE *, in_addr_t, const char *, const char *);
+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);
+
+int
+rcmd(ahost, rport, locuser, remuser, cmd, fd2p)
+        char **ahost;
+        in_port_t rport;
+        const char *locuser, *remuser, *cmd;
+        int *fd2p;
+{
+        return rcmd_af(ahost, rport, locuser, remuser, cmd, fd2p, AF_INET);
+}
+
+int
+rcmd_af(ahost, rport, locuser, remuser, cmd, fd2p, af)
+        char **ahost;
+        in_port_t rport;
+        const char *locuser, *remuser, *cmd;
+        int *fd2p;
+        int af;
+{
+        static char hbuf[MAXHOSTNAMELEN];
+        char pbuf[NI_MAXSERV];
+        struct addrinfo hints, *res, *r;
+        int error;
+        struct sockaddr_storage from;
+        fd_set *readsp = NULL;
+        sigset_t oldmask, mask;
+        pid_t pid;
+        int s, lport, timo;
+        char c, *p;
+        int refused;
+
+        /* call rcmdsh() with specified remote shell if appropriate. */
+        if (!issetugid() && (p = getenv("RSH")) && *p) {
+                struct servent *sp = getservbyname("shell", "tcp");
+
+                if (sp && sp->s_port == rport)
+                        return (rcmdsh(ahost, rport, locuser, remuser,
+                            cmd, p));
+        }
+
+        /* use rsh(1) if non-root and remote port is shell. */
+        if (geteuid()) {
+                struct servent *sp = getservbyname("shell", "tcp");
+
+                if (sp && sp->s_port == rport)
+                        return (rcmdsh(ahost, rport, locuser, remuser,
+                            cmd, NULL));
+        }
+
+        pid = getpid();
+        snprintf(pbuf, sizeof(pbuf), "%u", ntohs(rport));
+        memset(&hints, 0, sizeof(hints));
+        hints.ai_family = af;
+        hints.ai_socktype = SOCK_STREAM;
+        hints.ai_flags = AI_CANONNAME;
+        error = getaddrinfo(*ahost, pbuf, &hints, &res);
+        if (error) {
+#if 0
+                warnx("%s: %s", *ahost, gai_strerror(error));
+#endif
+                return (-1);
+        }
+        if (res->ai_canonname) {
+                strlcpy(hbuf, res->ai_canonname, sizeof(hbuf));
+                *ahost = hbuf;
+        } else
+                ; /*XXX*/
+
+        r = res;
+        refused = 0;
+        sigemptyset(&mask);
+        sigaddset(&mask, SIGURG);
+        oldmask = sigprocmask(SIG_BLOCK, &mask, &oldmask);
+        for (timo = 1, lport = IPPORT_RESERVED - 1;;) {
+                s = rresvport_af(&lport, r->ai_family);
+                if (s < 0) {
+                        if (errno == EAGAIN)
+                                (void)fprintf(stderr,
+                                    "rcmd: socket: All ports in use\n");
+                        else
+                                (void)fprintf(stderr, "rcmd: socket: %s\n",
+                                    strerror(errno));
+                        if (r->ai_next) {
+                                r = r->ai_next;
+                                continue;
+                        } else {
+                                sigprocmask(SIG_SETMASK, &oldmask, NULL);
+                                freeaddrinfo(res);
+                                return (-1);
+                        }
+                }
+                fcntl(s, F_SETOWN, pid);
+                if (connect(s, r->ai_addr, r->ai_addrlen) >= 0)
+                        break;
+                (void)close(s);
+                if (errno == EADDRINUSE) {
+                        lport--;
+                        continue;
+                }
+                if (errno == ECONNREFUSED)
+                        refused++;
+                if (r->ai_next) {
+                        int oerrno = errno;
+                        char hbuf[NI_MAXHOST];
+#ifdef NI_WITHSCOPEID
+                        const int niflags = NI_NUMERICHOST | NI_WITHSCOPEID;
+#else
+                        const int niflags = NI_NUMERICHOST;
+#endif
+
+                        hbuf[0] = '\0';
+                        if (getnameinfo(r->ai_addr, r->ai_addrlen,
+                            hbuf, sizeof(hbuf), NULL, 0, niflags) != 0)
+                                strlcpy(hbuf, "(invalid)", sizeof hbuf);
+                        (void)fprintf(stderr, "connect to address %s: ", hbuf);
+                        errno = oerrno;
+                        perror(0);
+                        r = r->ai_next;
+                        hbuf[0] = '\0';
+                        if (getnameinfo(r->ai_addr, r->ai_addrlen,
+                            hbuf, sizeof(hbuf), NULL, 0, niflags) != 0)
+                                strlcpy(hbuf, "(invalid)", sizeof hbuf);
+                        (void)fprintf(stderr, "Trying %s...\n", hbuf);
+                        continue;
+                }
+                if (refused && timo <= 16) {
+                        (void)sleep(timo);
+                        timo *= 2;
+                        r = res;
+                        refused = 0;
+                        continue;
+                }
+                (void)fprintf(stderr, "%s: %s\n", res->ai_canonname,
+                    strerror(errno));
+                sigprocmask(SIG_SETMASK, &oldmask, NULL);
+                freeaddrinfo(res);
+                return (-1);
+        }
+        /* given "af" can be PF_UNSPEC, we need the real af for "s" */
+        af = r->ai_family;
+        freeaddrinfo(res);
+#if 0
+        /*
+         * try to rresvport() to the same port. This will make rresvport()
+         * fail it's first bind, resulting in it choosing a random port.
+         */
+        lport--;
+#endif
+        if (fd2p == 0) {
+                write(s, "", 1);
+                lport = 0;
+        } else {
+                char num[8];
+                int s2 = rresvport_af(&lport, af), s3;
+                int len = sizeof(from);
+                int fdssize = howmany(MAX(s, s2)+1, NFDBITS) * sizeof(fd_mask);
+
+                if (s2 < 0)
+                        goto bad;
+                readsp = (fd_set *)malloc(fdssize);
+                if (readsp == NULL)
+                        goto bad;
+                listen(s2, 1);
+                (void)snprintf(num, sizeof(num), "%d", lport);
+                if (write(s, num, strlen(num)+1) != strlen(num)+1) {
+                        (void)fprintf(stderr,
+                            "rcmd: write (setting up stderr): %s\n",
+                            strerror(errno));
+                        (void)close(s2);
+                        goto bad;
+                }
+again:
+                bzero(readsp, fdssize);
+                FD_SET(s, readsp);
+                FD_SET(s2, readsp);
+                errno = 0;
+                if (select(MAX(s, s2) + 1, readsp, 0, 0, 0) < 1 ||
+                    !FD_ISSET(s2, readsp)) {
+                        if (errno != 0)
+                                (void)fprintf(stderr,
+                                    "rcmd: select (setting up stderr): %s\n",
+                                    strerror(errno));
+                        else
+                                (void)fprintf(stderr,
+                                "select: protocol failure in circuit setup\n");
+                        (void)close(s2);
+                        goto bad;
+                }
+                s3 = accept(s2, (struct sockaddr *)&from, &len);
+                /*
+                 * XXX careful for ftp bounce attacks. If discovered, shut them
+                 * down and check for the real auxiliary channel to connect.
+                 */
+                switch (from.ss_family) {
+                case AF_INET:
+                case AF_INET6:
+                        if (getnameinfo((struct sockaddr *)&from, len,
+                            NULL, 0, num, sizeof(num), NI_NUMERICSERV) == 0 &&
+                            atoi(num) != 20) {
+                                break;
+                        }
+                        close(s3);
+                        goto again;
+                default:
+                        break;
+                }
+                (void)close(s2);
+                if (s3 < 0) {
+                        (void)fprintf(stderr,
+                            "rcmd: accept: %s\n", strerror(errno));
+                        lport = 0;
+                        goto bad;
+                }
+                *fd2p = s3;
+                switch (from.ss_family) {
+                case AF_INET:
+                case AF_INET6:
+                        if (getnameinfo((struct sockaddr *)&from, len,
+                            NULL, 0, num, sizeof(num), NI_NUMERICSERV) != 0 ||
+                            (atoi(num) >= IPPORT_RESERVED ||
+                             atoi(num) < IPPORT_RESERVED / 2)) {
+                                (void)fprintf(stderr,
+                                    "socket: protocol failure in circuit setup.\n");
+                                goto bad2;
+                        }
+                        break;
+                default:
+                        break;
+                }
+        }
+        (void)write(s, locuser, strlen(locuser)+1);
+        (void)write(s, remuser, strlen(remuser)+1);
+        (void)write(s, cmd, strlen(cmd)+1);
+        if (read(s, &c, 1) != 1) {
+                (void)fprintf(stderr,
+                    "rcmd: %s: %s\n", *ahost, strerror(errno));
+                goto bad2;
+        }
+        if (c != 0) {
+                while (read(s, &c, 1) == 1) {
+                        (void)write(STDERR_FILENO, &c, 1);
+                        if (c == '\n')
+                                break;
+                }
+                goto bad2;
+        }
+        sigprocmask(SIG_SETMASK, &oldmask, NULL);
+        free(readsp);
+        return (s);
+bad2:
+        if (lport)
+                (void)close(*fd2p);
+bad:
+        if (readsp)
+                free(readsp);
+        (void)close(s);
+        sigprocmask(SIG_SETMASK, &oldmask, NULL);
+        return (-1);
+}
+
+int     __check_rhosts_file = 1;
+char    *__rcmd_errstr;
+
+int
+ruserok(rhost, superuser, ruser, luser)
+        const char *rhost, *ruser, *luser;
+        int superuser;
+{
+        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);
+}
+
+/*
+ * New .rhosts strategy: We are passed an ip address. We spin through
+ * hosts.equiv and .rhosts looking for a match. When the .rhosts only
+ * has ip addresses, we don't have to trust a nameserver.  When it
+ * contains hostnames, we spin through the list of addresses the nameserver
+ * gives us and look for a match.
+ *
+ * Returns 0 if ok, -1 if not ok.
+ */
+int
+iruserok(raddr, superuser, ruser, luser)
+        u_int32_t raddr;
+        int superuser;
+        const char *ruser, *luser;
+{
+        struct sockaddr_in sin;
+
+        memset(&sin, 0, sizeof(sin));
+        sin.sin_family = AF_INET;
+        sin.sin_len = sizeof(struct sockaddr_in);
+        memcpy(&sin.sin_addr, &raddr, sizeof(sin.sin_addr));
+        return iruserok_sa(&sin, sizeof(struct sockaddr_in), superuser, ruser,
+                    luser);
+}
+
+int
+iruserok_sa(raddr, rlen, superuser, ruser, luser)
+        const void *raddr;
+        int rlen;
+        int superuser;
+        const char *ruser, *luser;
+{
+        struct sockaddr *sa;
+        register char *cp;
+        struct stat sbuf;
+        struct passwd *pwd;
+        FILE *hostf;
+        uid_t uid;
+        int first;
+        char pbuf[MAXPATHLEN];
+
+        sa = (struct sockaddr *)raddr;
+        first = 1;
+        hostf = superuser ? NULL : fopen(_PATH_HEQUIV, "r");
+again:
+        if (hostf) {
+                if (__ivaliduser_sa(hostf, sa, rlen, luser, ruser) == 0) {
+                        (void)fclose(hostf);
+                        return (0);
+                }
+                (void)fclose(hostf);
+        }
+        if (first == 1 && (__check_rhosts_file || superuser)) {
+                first = 0;
+                if ((pwd = getpwnam(luser)) == NULL)
+                        return (-1);
+                snprintf(pbuf, sizeof pbuf, "%s/.rhosts", pwd->pw_dir);
+
+                /*
+                 * 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, "r");
+                (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) < 0)
+                        cp = ".rhosts lstat failed";
+                else if (!S_ISREG(sbuf.st_mode))
+                        cp = ".rhosts not regular file";
+                else if (fstat(fileno(hostf), &sbuf) < 0)
+                        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 writeable by other than owner";
+                /* If there were any problems, quit. */
+                if (cp) {
+                        __rcmd_errstr = cp;
+                        (void)fclose(hostf);
+                        return (-1);
+                }
+                goto again;
+        }
+        return (-1);
+}
+
+/*
+ * XXX
+ * Don't make static, used by lpd(8).
+ *
+ * Returns 0 if ok, -1 if not ok.
+ */
+int
+__ivaliduser(hostf, raddrl, luser, ruser)
+        FILE *hostf;
+        in_addr_t raddrl;
+        const char *luser, *ruser;
+{
+        struct sockaddr_in sin;
+
+        memset(&sin, 0, sizeof(sin));
+        sin.sin_family = AF_INET;
+        sin.sin_len = sizeof(struct sockaddr_in);
+        memcpy(&sin.sin_addr, &raddrl, sizeof(sin.sin_addr));
+        return __ivaliduser_sa(hostf, (struct sockaddr *)&sin, sin.sin_len,
+                    luser, ruser);
+}
+
+int
+__ivaliduser_sa(hostf, raddr, salen, luser, ruser)
+        FILE *hostf;
+        struct sockaddr *raddr;
+        socklen_t salen;
+        const char *luser, *ruser;
+{
+        register char *user, *p;
+        char *buf;
+        const char *auser, *ahost;
+        int hostok, userok;
+        char *rhost = (char *)-1;
+        char domain[MAXHOSTNAMELEN];
+        size_t buflen;
+
+        getdomainname(domain, sizeof(domain));
+
+        while ((buf = fgetln(hostf, &buflen))) {
+                p = buf;
+                if (*p == '#')
+                        continue;
+                while (*p != '\n' && *p != ' ' && *p != '\t' && p < buf + buflen) {
+                        if (!isprint(*p))
+                                goto bail;
+                        *p = isupper(*p) ? tolower(*p) : *p;
+                        p++;
+                }
+                if (p >= buf + buflen)
+                        continue;
+                if (*p == ' ' || *p == '\t') {
+                        *p++ = '\0';
+                        while ((*p == ' ' || *p == '\t') && p < buf + buflen)
+                                p++;
+                        if (p >= buf + buflen)
+                                continue;
+                        user = p;
+                        while (*p != '\n' && *p != ' ' &&
+                            *p != '\t' && p < buf + buflen) {
+                                if (!isprint(*p))
+                                        goto bail;
+                                p++;
+                        }
+                } else
+                        user = p;
+                *p = '\0';
+
+                if (p == buf)
+                        continue;
+
+                auser = *user ? user : luser;
+                ahost = buf;
+
+                if (strlen(ahost) >= MAXHOSTNAMELEN)
+                        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.
+ *
+ * NI_WITHSCOPEID is useful for comparing sin6_scope_id portion
+ * if af == AF_INET6.
+ */
+static int
+__icheckhost(raddr, salen, lhost)
+        struct sockaddr *raddr;
+        socklen_t salen;
+        const char *lhost;
+{
+        struct addrinfo hints, *res, *r;
+        char h1[NI_MAXHOST], h2[NI_MAXHOST];
+        int error;
+#ifdef NI_WITHSCOPEID
+        const int niflags = NI_NUMERICHOST | NI_WITHSCOPEID;
+#else
+        const int niflags = NI_NUMERICHOST;
+#endif
+
+        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.
+ *
+ * NI_WITHSCOPEID is useful for comparing sin6_scope_id portion
+ * if af == AF_INET6.
+ */
+static char *
+__gethostloop(raddr, salen)
+        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;
+#ifdef NI_WITHSCOPEID
+        const int niflags = NI_NUMERICHOST | NI_WITHSCOPEID;
+#else
+        const int niflags = NI_NUMERICHOST;
+#endif
+
+        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 adminstrator has made a configuration
+         * mistake, or someone has attempted to spoof us
+         */
+        syslog(LOG_NOTICE, "rcmd: address %s not listed for host %s",
+            h1, res->ai_canonname ? res->ai_canonname : remotehost);
+        freeaddrinfo(res);
+        return (NULL);
+}