util.subproj/rcmdsh.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
   7  * Reserved.  This file contains Original Code and/or Modifications of
   8  * Original Code as defined in and that are subject to the Apple Public
   9  * Source License Version 1.1 (the "License").  You may not use this file
  10  * except in compliance with the License.  Please obtain a copy of the
  11  * License at http://www.apple.com/publicsource and read it before using
  12  * this file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
  19  * License for the specific language governing rights and limitations
  20  * under the License.
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24 /*      $OpenBSD: rcmdsh.c,v 1.4 1997/07/23 16:59:37 millert Exp $      */
  25
  26 /*
  27  * This is an rcmd() replacement originally by
  28  * Chris Siebenmann <cks@utcc.utoronto.ca>.
  29  */
  30
  31 #if defined(LIBC_SCCS) && !defined(lint)
  32 static char *rcsid = "$OpenBSD: rcmdsh.c,v 1.4 1997/07/23 16:59:37 millert Exp $";
  33 #endif /* LIBC_SCCS and not lint */
  34
  35 #include      <sys/types.h>
  36 #include      <sys/socket.h>
  37 #include      <sys/wait.h>
  38 #include      <signal.h>
  39 #include      <errno.h>
  40 #include      <netdb.h>
  41 #include      <stdio.h>
  42 #include      <string.h>
  43 #include      <pwd.h>
  44 #include      <paths.h>
  45 #include      <unistd.h>
  46 /*
  47  * This is a replacement rcmd() function that uses the rsh(1)
  48  * program in place of a direct rcmd(3) function call so as to
  49  * avoid having to be root.  Note that rport is ignored.
  50  */
  51 /* ARGSUSED */
  52 int
  53 rcmdsh(ahost, rport, locuser, remuser, cmd, rshprog)
  54         char **ahost;
  55         int rport;
  56         const char *locuser, *remuser, *cmd;
  57         char *rshprog;
  58 {
  59         struct hostent *hp;
  60         int cpid, sp[2];
  61         char *p;
  62         struct passwd *pw;
  63
  64         /* What rsh/shell to use. */
  65         if (rshprog == NULL)
  66                 rshprog = _PATH_RSH;
  67
  68         /* locuser must exist on this host. */
  69         if ((pw = getpwnam(locuser)) == NULL) {
  70                 (void) fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
  71                 return(-1);
  72         }
  73
  74         /* Validate remote hostname. */
  75         if (strcmp(*ahost, "localhost") != 0) {
  76                 if ((hp = gethostbyname(*ahost)) == NULL) {
  77                         herror(*ahost);
  78                         return(-1);
  79                 }
  80                 *ahost = hp->h_name;
  81         }
  82
  83         /* Get a socketpair we'll use for stdin and stdout. */
  84         if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0) {
  85                 perror("rcmdsh: socketpair");
  86                 return(-1);
  87         }
  88
  89         cpid = fork();
  90         if (cpid < 0) {
  91                 perror("rcmdsh: fork failed");
  92                 return(-1);
  93         } else if (cpid == 0) {
  94                 /*
  95                  * Child.  We use sp[1] to be stdin/stdout, and close sp[0].
  96                  */
  97                 (void) close(sp[0]);
  98                 if (dup2(sp[1], 0) < 0 || dup2(0, 1) < 0) {
  99                         perror("rcmdsh: dup2 failed");
 100                         _exit(255);
 101                 }
 102                 /* Fork again to lose parent. */
 103                 cpid = fork();
 104                 if (cpid < 0) {
 105                         perror("rcmdsh: fork to lose parent failed");
 106                         _exit(255);
 107                 }
 108                 if (cpid > 0)
 109                         _exit(0);
 110
 111                 /* In grandchild here.  Become local user for rshprog. */
 112                 if (setuid(pw->pw_uid)) {
 113                         (void) fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
 114                                        pw->pw_uid, strerror(errno));
 115                         _exit(255);
 116                 }
 117
 118                 /*
 119                  * If remote host is "localhost" and local and remote user
 120                  * are the same, avoid running remote shell for efficiency.
 121                  */
 122                 if (!strcmp(*ahost, "localhost") && !strcmp(locuser, remuser)) {
 123                         if (pw->pw_shell[0] == '\0')
 124                                 rshprog = _PATH_BSHELL;
 125                         else
 126                                 rshprog = pw->pw_shell;
 127                         p = strrchr(rshprog, '/');
 128                         execlp(rshprog, p ? p+1 : rshprog, "-c", cmd,
 129                                (char *) NULL);
 130                 } else {
 131                         p = strrchr(rshprog, '/');
 132                         execlp(rshprog, p ? p+1 : rshprog, *ahost, "-l",
 133                                remuser, cmd, (char *) NULL);
 134                 }
 135                 (void) fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
 136                                rshprog, strerror(errno));
 137                 _exit(255);
 138         } else {
 139                 /* Parent. close sp[1], return sp[0]. */
 140                 (void) close(sp[1]);
 141                 /* Reap child. */
 142                 (void) wait(NULL);
 143         }
 144         return(sp[0]);
 145 }