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 #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(ahost, rport, locuser, remuser, cmd, rshprog) 63 char **ahost; 64 int rport; 65 const char *locuser, *remuser, *cmd, *rshprog; 66 { 67 struct addrinfo hints, *res; 68 int cpid, sp[2], error; 69 char *p; 70 struct passwd *pw; 71 char num[8]; 72 static char hbuf[NI_MAXHOST]; 73 74 /* What rsh/shell to use. */ 75 if (rshprog == NULL) 76 rshprog = _PATH_RSH; 77 78 /* locuser must exist on this host. */ 79 if ((pw = getpwnam(locuser)) == NULL) { 80 (void)fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser); 81 return (-1); 82 } 83 84 /* Validate remote hostname. */ 85 if (strcmp(*ahost, "localhost") != 0) { 86 memset(&hints, 0, sizeof(hints)); 87 hints.ai_flags = AI_CANONNAME; 88 hints.ai_family = PF_UNSPEC; 89 hints.ai_socktype = SOCK_STREAM; 90 (void)snprintf(num, sizeof(num), "%u", 91 (unsigned int)ntohs(rport)); 92 error = getaddrinfo(*ahost, num, &hints, &res); 93 if (error) { 94 fprintf(stderr, "rcmdsh: getaddrinfo: %s\n", 95 gai_strerror(error)); 96 return (-1); 97 } 98 if (res->ai_canonname) { 99 strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1); 100 hbuf[sizeof(hbuf) - 1] = '\0'; 101 *ahost = hbuf; 102 } 103 freeaddrinfo(res); 104 } 105 106 /* Get a socketpair we'll use for stdin and stdout. */ 107 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) { 108 perror("rcmdsh: socketpair"); 109 return (-1); 110 } 111 112 cpid = fork(); 113 if (cpid == -1) { 114 perror("rcmdsh: fork failed"); 115 return (-1); 116 } else if (cpid == 0) { 117 /* 118 * Child. We use sp[1] to be stdin/stdout, and close sp[0]. 119 */ 120 (void)close(sp[0]); 121 if (dup2(sp[1], 0) == -1 || dup2(0, 1) == -1) { 122 perror("rcmdsh: dup2 failed"); 123 _exit(255); 124 } 125 /* Fork again to lose parent. */ 126 cpid = fork(); 127 if (cpid == -1) { 128 perror("rcmdsh: fork to lose parent failed"); 129 _exit(255); 130 } 131 if (cpid > 0) 132 _exit(0); 133 134 /* In grandchild here. Become local user for rshprog. */ 135 if (setuid(pw->pw_uid) == -1) { 136 (void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n", 137 pw->pw_uid, strerror(errno)); 138 _exit(255); 139 } 140 141 /* 142 * If remote host is "localhost" and local and remote users 143 * are the same, avoid running remote shell for efficiency. 144 */ 145 if (strcmp(*ahost, "localhost") == 0 && 146 strcmp(locuser, remuser) == 0) { 147 if (pw->pw_shell[0] == '\0') 148 rshprog = _PATH_BSHELL; 149 else 150 rshprog = pw->pw_shell; 151 p = strrchr(rshprog, '/'); 152 execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd, 153 (char *)NULL); 154 } else { 155 p = strrchr(rshprog, '/'); 156 execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l", 157 remuser, cmd, (char *)NULL); 158 } 159 (void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n", 160 rshprog, strerror(errno)); 161 _exit(255); 162 } else { 163 /* Parent. close sp[1], return sp[0]. */ 164 (void)close(sp[1]); 165 /* Reap child. */ 166 (void)wait(NULL); 167 return (sp[0]); 168 } 169 /* NOTREACHED */ 170 } 171