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 "namespace.h" 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 #include "un-namespace.h" 52 53 /* 54 * This is a replacement rcmd() function that uses the rsh(1) 55 * program in place of a direct rcmd(3) function call so as to 56 * avoid having to be root. Note that rport is ignored. 57 */ 58 int 59 rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser, 60 const char *cmd, const char *rshprog) 61 { 62 struct addrinfo hints, *res; 63 int sp[2], error; 64 pid_t cpid; 65 char *p; 66 struct passwd *pw; 67 char num[8]; 68 static char hbuf[NI_MAXHOST]; 69 70 /* What rsh/shell to use. */ 71 if (rshprog == NULL) 72 rshprog = _PATH_RSH; 73 74 /* locuser must exist on this host. */ 75 if ((pw = getpwnam(locuser)) == NULL) { 76 (void)fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser); 77 return (-1); 78 } 79 80 /* Validate remote hostname. */ 81 if (strcmp(*ahost, "localhost") != 0) { 82 memset(&hints, 0, sizeof(hints)); 83 hints.ai_flags = AI_CANONNAME; 84 hints.ai_family = PF_UNSPEC; 85 hints.ai_socktype = SOCK_STREAM; 86 (void)snprintf(num, sizeof(num), "%u", 87 (unsigned int)ntohs(rport)); 88 error = getaddrinfo(*ahost, num, &hints, &res); 89 if (error) { 90 fprintf(stderr, "rcmdsh: getaddrinfo: %s\n", 91 gai_strerror(error)); 92 return (-1); 93 } 94 if (res->ai_canonname) { 95 strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1); 96 hbuf[sizeof(hbuf) - 1] = '\0'; 97 *ahost = hbuf; 98 } 99 freeaddrinfo(res); 100 } 101 102 /* Get a socketpair we'll use for stdin and stdout. */ 103 if (_socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) { 104 perror("rcmdsh: socketpair"); 105 return (-1); 106 } 107 108 cpid = fork(); 109 if (cpid == -1) { 110 perror("rcmdsh: fork failed"); 111 return (-1); 112 } else if (cpid == 0) { 113 /* 114 * Child. We use sp[1] to be stdin/stdout, and close sp[0]. 115 */ 116 (void)_close(sp[0]); 117 if (_dup2(sp[1], 0) == -1 || _dup2(0, 1) == -1) { 118 perror("rcmdsh: dup2 failed"); 119 _exit(255); 120 } 121 /* Fork again to lose parent. */ 122 cpid = fork(); 123 if (cpid == -1) { 124 perror("rcmdsh: fork to lose parent failed"); 125 _exit(255); 126 } 127 if (cpid > 0) 128 _exit(0); 129 130 /* In grandchild here. Become local user for rshprog. */ 131 if (setuid(pw->pw_uid) == -1) { 132 (void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n", 133 pw->pw_uid, strerror(errno)); 134 _exit(255); 135 } 136 137 /* 138 * If remote host is "localhost" and local and remote users 139 * are the same, avoid running remote shell for efficiency. 140 */ 141 if (strcmp(*ahost, "localhost") == 0 && 142 strcmp(locuser, remuser) == 0) { 143 if (pw->pw_shell[0] == '\0') 144 rshprog = _PATH_BSHELL; 145 else 146 rshprog = pw->pw_shell; 147 p = strrchr(rshprog, '/'); 148 execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd, 149 (char *)NULL); 150 } else { 151 p = strrchr(rshprog, '/'); 152 execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l", 153 remuser, cmd, (char *)NULL); 154 } 155 (void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n", 156 rshprog, strerror(errno)); 157 _exit(255); 158 } else { 159 /* Parent. close sp[1], return sp[0]. */ 160 (void)_close(sp[1]); 161 /* Reap child. */ 162 (void)_waitpid(cpid, NULL, 0); 163 return (sp[0]); 164 } 165 /* NOTREACHED */ 166 } 167