util.subproj/rcmdsh.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*      $OpenBSD: rcmdsh.c,v 1.4 1997/07/23 16:59:37 millert Exp $      */
  26
  27 /*
  28  * This is an rcmd() replacement originally by
  29  * Chris Siebenmann <cks@utcc.utoronto.ca>.
  30  */
  31
  32 #if defined(LIBC_SCCS) && !defined(lint)
  33 static char *rcsid = "$OpenBSD: rcmdsh.c,v 1.4 1997/07/23 16:59:37 millert Exp $";
  34 #endif /* LIBC_SCCS and not lint */
  35
  36 #include      <sys/types.h>
  37 #include      <sys/socket.h>
  38 #include      <sys/wait.h>
  39 #include      <signal.h>
  40 #include      <errno.h>
  41 #include      <netdb.h>
  42 #include      <stdio.h>
  43 #include      <string.h>
  44 #include      <pwd.h>
  45 #include      <paths.h>
  46 #include      <unistd.h>
  47 /*
  48  * This is a replacement rcmd() function that uses the rsh(1)
  49  * program in place of a direct rcmd(3) function call so as to
  50  * avoid having to be root.  Note that rport is ignored.
  51  */
  52 /* ARGSUSED */
  53 int
  54 rcmdsh(ahost, rport, locuser, remuser, cmd, rshprog)
  55         char **ahost;
  56         int rport;
  57         const char *locuser, *remuser, *cmd;
  58         char *rshprog;
  59 {
  60         struct hostent *hp;
  61         int cpid, sp[2];
  62         char *p;
  63         struct passwd *pw;
  64
  65         /* What rsh/shell to use. */
  66         if (rshprog == NULL)
  67                 rshprog = _PATH_RSH;
  68
  69         /* locuser must exist on this host. */
  70         if ((pw = getpwnam(locuser)) == NULL) {
  71                 (void) fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
  72                 return(-1);
  73         }
  74
  75         /* Validate remote hostname. */
  76         if (strcmp(*ahost, "localhost") != 0) {
  77                 if ((hp = gethostbyname(*ahost)) == NULL) {
  78                         herror(*ahost);
  79                         return(-1);
  80                 }
  81                 *ahost = hp->h_name;
  82         }
  83
  84         /* Get a socketpair we'll use for stdin and stdout. */
  85         if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0) {
  86                 perror("rcmdsh: socketpair");
  87                 return(-1);
  88         }
  89
  90         cpid = fork();
  91         if (cpid < 0) {
  92                 perror("rcmdsh: fork failed");
  93                 return(-1);
  94         } else if (cpid == 0) {
  95                 /*
  96                  * Child.  We use sp[1] to be stdin/stdout, and close sp[0].
  97                  */
  98                 (void) close(sp[0]);
  99                 if (dup2(sp[1], 0) < 0 || dup2(0, 1) < 0) {
 100                         perror("rcmdsh: dup2 failed");
 101                         _exit(255);
 102                 }
 103                 /* Fork again to lose parent. */
 104                 cpid = fork();
 105                 if (cpid < 0) {
 106                         perror("rcmdsh: fork to lose parent failed");
 107                         _exit(255);
 108                 }
 109                 if (cpid > 0)
 110                         _exit(0);
 111
 112                 /* In grandchild here.  Become local user for rshprog. */
 113                 if (setuid(pw->pw_uid)) {
 114                         (void) fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
 115                                        pw->pw_uid, strerror(errno));
 116                         _exit(255);
 117                 }
 118
 119                 /*
 120                  * If remote host is "localhost" and local and remote user
 121                  * are the same, avoid running remote shell for efficiency.
 122                  */
 123                 if (!strcmp(*ahost, "localhost") && !strcmp(locuser, remuser)) {
 124                         if (pw->pw_shell[0] == '\0')
 125                                 rshprog = _PATH_BSHELL;
 126                         else
 127                                 rshprog = pw->pw_shell;
 128                         p = strrchr(rshprog, '/');
 129                         execlp(rshprog, p ? p+1 : rshprog, "-c", cmd,
 130                                (char *) NULL);
 131                 } else {
 132                         p = strrchr(rshprog, '/');
 133                         execlp(rshprog, p ? p+1 : rshprog, *ahost, "-l",
 134                                remuser, cmd, (char *) NULL);
 135                 }
 136                 (void) fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
 137                                rshprog, strerror(errno));
 138                 _exit(255);
 139         } else {
 140                 /* Parent. close sp[1], return sp[0]. */
 141                 (void) close(sp[1]);
 142                 /* Reap child. */
 143                 (void) wait(NULL);
 144         }
 145         return(sp[0]);
 146 }