1 /* $OpenBSD: rcmdsh.c,v 1.7 2002/03/12 00:05:44 millert Exp $ */ 2 3 /*- 4 * SPDX-License-Identifier: BSD-3-Clause 5 * 6 * Copyright (c) 2001, MagniComp 7 * All rights reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in 16 * the documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the MagniComp nor the names of its contributors may 18 * be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 22 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR 25 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 27 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 28 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE 30 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33 /* 34 * This is an rcmd() replacement originally by 35 * Chris Siebenmann <cks@utcc.utoronto.ca>. 36 */ 37 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 #include "namespace.h" 42 #include <sys/types.h> 43 #include <sys/socket.h> 44 #include <sys/wait.h> 45 #include <arpa/inet.h> 46 47 #include <errno.h> 48 #include <netdb.h> 49 #include <paths.h> 50 #include <pwd.h> 51 #include <stdio.h> 52 #include <string.h> 53 #include <unistd.h> 54 #include "un-namespace.h" 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(char **ahost, int rport, const char *locuser, const char *remuser, 63 const char *cmd, const char *rshprog) 64 { 65 struct addrinfo hints, *res; 66 int sp[2], error; 67 pid_t cpid; 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), "%u", 90 (unsigned int)ntohs(rport)); 91 error = getaddrinfo(*ahost, num, &hints, &res); 92 if (error) { 93 fprintf(stderr, "rcmdsh: getaddrinfo: %s\n", 94 gai_strerror(error)); 95 return (-1); 96 } 97 if (res->ai_canonname) { 98 strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1); 99 hbuf[sizeof(hbuf) - 1] = '\0'; 100 *ahost = hbuf; 101 } 102 freeaddrinfo(res); 103 } 104 105 /* Get a socketpair we'll use for stdin and stdout. */ 106 if (_socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) { 107 perror("rcmdsh: socketpair"); 108 return (-1); 109 } 110 111 cpid = fork(); 112 if (cpid == -1) { 113 perror("rcmdsh: fork failed"); 114 return (-1); 115 } else if (cpid == 0) { 116 /* 117 * Child. We use sp[1] to be stdin/stdout, and close sp[0]. 118 */ 119 (void)_close(sp[0]); 120 if (_dup2(sp[1], 0) == -1 || _dup2(0, 1) == -1) { 121 perror("rcmdsh: dup2 failed"); 122 _exit(255); 123 } 124 /* Fork again to lose parent. */ 125 cpid = fork(); 126 if (cpid == -1) { 127 perror("rcmdsh: fork to lose parent failed"); 128 _exit(255); 129 } 130 if (cpid > 0) 131 _exit(0); 132 133 /* In grandchild here. Become local user for rshprog. */ 134 if (setuid(pw->pw_uid) == -1) { 135 (void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n", 136 pw->pw_uid, strerror(errno)); 137 _exit(255); 138 } 139 140 /* 141 * If remote host is "localhost" and local and remote users 142 * are the same, avoid running remote shell for efficiency. 143 */ 144 if (strcmp(*ahost, "localhost") == 0 && 145 strcmp(locuser, remuser) == 0) { 146 if (pw->pw_shell[0] == '\0') 147 rshprog = _PATH_BSHELL; 148 else 149 rshprog = pw->pw_shell; 150 p = strrchr(rshprog, '/'); 151 execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd, 152 (char *)NULL); 153 } else { 154 p = strrchr(rshprog, '/'); 155 execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l", 156 remuser, cmd, (char *)NULL); 157 } 158 (void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n", 159 rshprog, strerror(errno)); 160 _exit(255); 161 } else { 162 /* Parent. close sp[1], return sp[0]. */ 163 (void)_close(sp[1]); 164 /* Reap child. */ 165 (void)_waitpid(cpid, NULL, 0); 166 return (sp[0]); 167 } 168 /* NOTREACHED */ 169 } 170