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 #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 /* 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 int 58 rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser, 59 const char *cmd, const char *rshprog) 60 { 61 struct addrinfo hints, *res; 62 int sp[2], error; 63 pid_t cpid; 64 char *p; 65 struct passwd *pw; 66 char num[8]; 67 static char hbuf[NI_MAXHOST]; 68 69 /* What rsh/shell to use. */ 70 if (rshprog == NULL) 71 rshprog = _PATH_RSH; 72 73 /* locuser must exist on this host. */ 74 if ((pw = getpwnam(locuser)) == NULL) { 75 (void)fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser); 76 return (-1); 77 } 78 79 /* Validate remote hostname. */ 80 if (strcmp(*ahost, "localhost") != 0) { 81 memset(&hints, 0, sizeof(hints)); 82 hints.ai_flags = AI_CANONNAME; 83 hints.ai_family = PF_UNSPEC; 84 hints.ai_socktype = SOCK_STREAM; 85 (void)snprintf(num, sizeof(num), "%u", 86 (unsigned int)ntohs(rport)); 87 error = getaddrinfo(*ahost, num, &hints, &res); 88 if (error) { 89 fprintf(stderr, "rcmdsh: getaddrinfo: %s\n", 90 gai_strerror(error)); 91 return (-1); 92 } 93 if (res->ai_canonname) { 94 strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1); 95 hbuf[sizeof(hbuf) - 1] = '\0'; 96 *ahost = hbuf; 97 } 98 freeaddrinfo(res); 99 } 100 101 /* Get a socketpair we'll use for stdin and stdout. */ 102 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) { 103 perror("rcmdsh: socketpair"); 104 return (-1); 105 } 106 107 cpid = fork(); 108 if (cpid == -1) { 109 perror("rcmdsh: fork failed"); 110 return (-1); 111 } else if (cpid == 0) { 112 /* 113 * Child. We use sp[1] to be stdin/stdout, and close sp[0]. 114 */ 115 (void)close(sp[0]); 116 if (dup2(sp[1], 0) == -1 || dup2(0, 1) == -1) { 117 perror("rcmdsh: dup2 failed"); 118 _exit(255); 119 } 120 /* Fork again to lose parent. */ 121 cpid = fork(); 122 if (cpid == -1) { 123 perror("rcmdsh: fork to lose parent failed"); 124 _exit(255); 125 } 126 if (cpid > 0) 127 _exit(0); 128 129 /* In grandchild here. Become local user for rshprog. */ 130 if (setuid(pw->pw_uid) == -1) { 131 (void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n", 132 pw->pw_uid, strerror(errno)); 133 _exit(255); 134 } 135 136 /* 137 * If remote host is "localhost" and local and remote users 138 * are the same, avoid running remote shell for efficiency. 139 */ 140 if (strcmp(*ahost, "localhost") == 0 && 141 strcmp(locuser, remuser) == 0) { 142 if (pw->pw_shell[0] == '\0') 143 rshprog = _PATH_BSHELL; 144 else 145 rshprog = pw->pw_shell; 146 p = strrchr(rshprog, '/'); 147 execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd, 148 (char *)NULL); 149 } else { 150 p = strrchr(rshprog, '/'); 151 execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l", 152 remuser, cmd, (char *)NULL); 153 } 154 (void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n", 155 rshprog, strerror(errno)); 156 _exit(255); 157 } else { 158 /* Parent. close sp[1], return sp[0]. */ 159 (void)close(sp[1]); 160 /* Reap child. */ 161 (void)wait(NULL); 162 return (sp[0]); 163 } 164 /* NOTREACHED */ 165 } 166