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 31 /* 32 * This is an rcmd() replacement originally by 33 * Chris Siebenmann <cks@utcc.utoronto.ca>. 34 */ 35 36 #if defined(LIBC_SCCS) && !defined(lint) 37 static char *rcsid = "$OpenBSD: rcmdsh.c,v 1.7 2002/03/12 00:05:44 millert Exp $"; 38 #endif /* LIBC_SCCS and not lint */ 39 40 #include <sys/types.h> 41 #include <sys/socket.h> 42 #include <sys/wait.h> 43 #include <signal.h> 44 #include <errno.h> 45 #include <netdb.h> 46 #include <stdio.h> 47 #include <string.h> 48 #include <pwd.h> 49 #include <paths.h> 50 #include <unistd.h> 51 52 /* 53 * This is a replacement rcmd() function that uses the rsh(1) 54 * program in place of a direct rcmd(3) function call so as to 55 * avoid having to be root. Note that rport is ignored. 56 */ 57 /* ARGSUSED */ 58 int 59 rcmdsh(ahost, rport, locuser, remuser, cmd, rshprog) 60 char **ahost; 61 int rport; 62 const char *locuser, *remuser, *cmd; 63 char *rshprog; 64 { 65 struct hostent *hp; 66 int sp[2]; 67 pid_t cpid; 68 char *p; 69 struct passwd *pw; 70 71 /* What rsh/shell to use. */ 72 if (rshprog == NULL) 73 rshprog = _PATH_RSH; 74 75 /* locuser must exist on this host. */ 76 if ((pw = getpwnam(locuser)) == NULL) { 77 (void) fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser); 78 return(-1); 79 } 80 81 /* Validate remote hostname. */ 82 if (strcmp(*ahost, "localhost") != 0) { 83 if ((hp = gethostbyname(*ahost)) == NULL) { 84 herror(*ahost); 85 return(-1); 86 } 87 *ahost = hp->h_name; 88 } 89 90 /* Get a socketpair we'll use for stdin and stdout. */ 91 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) < 0) { 92 perror("rcmdsh: socketpair"); 93 return(-1); 94 } 95 96 cpid = fork(); 97 if (cpid < 0) { 98 perror("rcmdsh: fork failed"); 99 return(-1); 100 } else if (cpid == 0) { 101 /* 102 * Child. We use sp[1] to be stdin/stdout, and close sp[0]. 103 */ 104 (void) close(sp[0]); 105 if (dup2(sp[1], 0) < 0 || dup2(0, 1) < 0) { 106 perror("rcmdsh: dup2 failed"); 107 _exit(255); 108 } 109 /* Fork again to lose parent. */ 110 cpid = fork(); 111 if (cpid < 0) { 112 perror("rcmdsh: fork to lose parent failed"); 113 _exit(255); 114 } 115 if (cpid > 0) 116 _exit(0); 117 118 /* In grandchild here. Become local user for rshprog. */ 119 if (setuid(pw->pw_uid)) { 120 (void) fprintf(stderr, "rcmdsh: setuid(%u): %s\n", 121 pw->pw_uid, strerror(errno)); 122 _exit(255); 123 } 124 125 /* 126 * If remote host is "localhost" and local and remote user 127 * are the same, avoid running remote shell for efficiency. 128 */ 129 if (!strcmp(*ahost, "localhost") && !strcmp(locuser, remuser)) { 130 if (pw->pw_shell[0] == '\0') 131 rshprog = _PATH_BSHELL; 132 else 133 rshprog = pw->pw_shell; 134 p = strrchr(rshprog, '/'); 135 execlp(rshprog, p ? p+1 : rshprog, "-c", cmd, 136 (char *) NULL); 137 } else { 138 p = strrchr(rshprog, '/'); 139 execlp(rshprog, p ? p+1 : rshprog, *ahost, "-l", 140 remuser, cmd, (char *) NULL); 141 } 142 (void) fprintf(stderr, "rcmdsh: execlp %s failed: %s\n", 143 rshprog, strerror(errno)); 144 _exit(255); 145 } else { 146 /* Parent. close sp[1], return sp[0]. */ 147 (void) close(sp[1]); 148 /* Reap child. */ 149 (void) wait(NULL); 150 return(sp[0]); 151 } 152 /* NOTREACHED */ 153 } 154