lib/libc/net/rcmdsh.c

   1 /*      $OpenBSD: rcmdsh.c,v 1.7 2002/03/12 00:05:44 millert Exp $      */
   2
   3 /*
   4  * Copyright (c) 2001, MagniComp
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in
  14  *    the documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the MagniComp nor the names of its contributors may
  16  *    be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  20  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
  23  * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  25  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  26  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  27  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
  28  * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  *
  30  * $FreeBSD: src/lib/libc/net/rcmdsh.c,v 1.5 2003/02/27 13:40:00 nectar Exp $
  31  * $DragonFly: src/lib/libc/net/rcmdsh.c,v 1.4 2005/11/13 02:04:47 swildner Exp $
  32  */
  33
  34 /*
  35  * This is an rcmd() replacement originally by
  36  * Chris Siebenmann <cks@utcc.utoronto.ca>.
  37  */
  38
  39 #include <sys/types.h>
  40 #include <sys/socket.h>
  41 #include <sys/wait.h>
  42 #include <arpa/inet.h>
  43
  44 #include <errno.h>
  45 #include <netdb.h>
  46 #include <paths.h>
  47 #include <pwd.h>
  48 #include <stdio.h>
  49 #include <string.h>
  50 #include <unistd.h>
  51
  52 #ifndef _PATH_RSH
  53 #define _PATH_RSH       "/usr/bin/rsh"
  54 #endif
  55
  56 /*
  57  * This is a replacement rcmd() function that uses the rsh(1)
  58  * program in place of a direct rcmd(3) function call so as to
  59  * avoid having to be root.  Note that rport is ignored.
  60  */
  61 int
  62 rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser,
  63        const char *cmd, const char *rshprog)
  64 {
  65         struct addrinfo hints, *res;
  66         int sp[2], error;
  67         pid_t cpid;
  68         char *p;
  69         struct passwd *pw;
  70         char num[8];
  71         static char hbuf[NI_MAXHOST];
  72
  73         /* What rsh/shell to use. */
  74         if (rshprog == NULL)
  75                 rshprog = _PATH_RSH;
  76
  77         /* locuser must exist on this host. */
  78         if ((pw = getpwnam(locuser)) == NULL) {
  79                 fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
  80                 return (-1);
  81         }
  82
  83         /* Validate remote hostname. */
  84         if (strcmp(*ahost, "localhost") != 0) {
  85                 memset(&hints, 0, sizeof(hints));
  86                 hints.ai_flags = AI_CANONNAME;
  87                 hints.ai_family = PF_UNSPEC;
  88                 hints.ai_socktype = SOCK_STREAM;
  89                 snprintf(num, sizeof(num), "%u", (unsigned int)ntohs(rport));
  90                 error = getaddrinfo(*ahost, num, &hints, &res);
  91                 if (error) {
  92                         fprintf(stderr, "rcmdsh: getaddrinfo: %s\n",
  93                                 gai_strerror(error));
  94                         return (-1);
  95                 }
  96                 if (res->ai_canonname) {
  97                         strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1);
  98                         hbuf[sizeof(hbuf) - 1] = '\0';
  99                         *ahost = hbuf;
 100                 }
 101                 freeaddrinfo(res);
 102         }
 103
 104         /* Get a socketpair we'll use for stdin and stdout. */
 105         if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) {
 106                 perror("rcmdsh: socketpair");
 107                 return (-1);
 108         }
 109
 110         cpid = fork();
 111         if (cpid == -1) {
 112                 perror("rcmdsh: fork failed");
 113                 return (-1);
 114         } else if (cpid == 0) {
 115                 /*
 116                  * Child.  We use sp[1] to be stdin/stdout, and close sp[0].
 117                  */
 118                 close(sp[0]);
 119                 if (dup2(sp[1], 0) == -1 || dup2(0, 1) == -1) {
 120                         perror("rcmdsh: dup2 failed");
 121                         _exit(255);
 122                 }
 123                 /* Fork again to lose parent. */
 124                 cpid = fork();
 125                 if (cpid == -1) {
 126                         perror("rcmdsh: fork to lose parent failed");
 127                         _exit(255);
 128                 }
 129                 if (cpid > 0)
 130                         _exit(0);
 131
 132                 /* In grandchild here.  Become local user for rshprog. */
 133                 if (setuid(pw->pw_uid) == -1) {
 134                         fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
 135                             pw->pw_uid, strerror(errno));
 136                         _exit(255);
 137                 }
 138
 139                 /*
 140                  * If remote host is "localhost" and local and remote users
 141                  * are the same, avoid running remote shell for efficiency.
 142                  */
 143                 if (strcmp(*ahost, "localhost") == 0 &&
 144                     strcmp(locuser, remuser) == 0) {
 145                         if (pw->pw_shell[0] == '\0')
 146                                 rshprog = _PATH_BSHELL;
 147                         else
 148                                 rshprog = pw->pw_shell;
 149                         p = strrchr(rshprog, '/');
 150                         execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd, NULL);
 151                 } else {
 152                         p = strrchr(rshprog, '/');
 153                         execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l",
 154                             remuser, cmd, NULL);
 155                 }
 156                 fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
 157                     rshprog, strerror(errno));
 158                 _exit(255);
 159         } else {
 160                 /* Parent. close sp[1], return sp[0]. */
 161                 close(sp[1]);
 162                 /* Reap child. */
 163                 wait(NULL);
 164                 return (sp[0]);
 165         }
 166         /* NOTREACHED */
 167 }