1 /* $OpenBSD: rcmdsh.c,v 1.5 1998/04/25 16:23:58 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 #include <sys/cdefs.h> 37 __FBSDID("$FreeBSD$"); 38 39 #include <sys/types.h> 40 #include <sys/socket.h> 41 #include <sys/wait.h> 42 43 #include <errno.h> 44 #include <netdb.h> 45 #include <paths.h> 46 #include <pwd.h> 47 #include <stdio.h> 48 #include <string.h> 49 #include <unistd.h> 50 51 #ifndef _PATH_RSH 52 #define _PATH_RSH "/usr/bin/rsh" 53 #endif 54 55 /* 56 * This is a replacement rcmd() function that uses the rsh(1) 57 * program in place of a direct rcmd(3) function call so as to 58 * avoid having to be root. Note that rport is ignored. 59 */ 60 int 61 rcmdsh(ahost, rport, locuser, remuser, cmd, rshprog) 62 char **ahost; 63 int rport; 64 const char *locuser, *remuser, *cmd, *rshprog; 65 { 66 struct addrinfo hints, *res; 67 int cpid, sp[2], error; 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 (void)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 (void)snprintf(num, sizeof(num), "%d", 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 (void)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 (void)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, 151 (char *)NULL); 152 } else { 153 p = strrchr(rshprog, '/'); 154 execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l", 155 remuser, cmd, (char *)NULL); 156 } 157 (void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n", 158 rshprog, strerror(errno)); 159 _exit(255); 160 } else { 161 /* Parent. close sp[1], return sp[0]. */ 162 (void)close(sp[1]); 163 /* Reap child. */ 164 (void)wait(NULL); 165 return (sp[0]); 166 } 167 /* NOTREACHED */ 168 } 169