1 /* $OpenBSD: rcmdsh.c,v 1.9 2004/04/01 04:14:29 marc 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 #if defined(LIBC_SCCS) && !defined(lint) 37 static char *rcsid = "$OpenBSD: rcmdsh.c,v 1.9 2004/04/01 04:14:29 marc Exp $"; 38 #endif /* LIBC_SCCS and not lint */ 39 40 #include <sys/types.h> 41 #include <sys/socket.h> 42 #include <sys/wait.h> 43 #include <signal.h> 44 #include <errno.h> 45 #include <netdb.h> 46 #include <stdio.h> 47 #include <stdlib.h> 48 #include <string.h> 49 #include <pwd.h> 50 #include <paths.h> 51 #include <unistd.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 /* ARGSUSED */ 59 int 60 rcmdsh(ahost, rport, locuser, remuser, cmd, rshprog) 61 char **ahost; 62 int rport; 63 const char *locuser, *remuser, *cmd; 64 char *rshprog; 65 { 66 struct hostent *hp; 67 int sp[2]; 68 pid_t cpid; 69 char *p; 70 struct passwd *pw; 71 72 /* What rsh/shell to use. */ 73 if (rshprog == NULL) 74 rshprog = _PATH_RSH; 75 76 /* locuser must exist on this host. */ 77 if ((pw = getpwnam(locuser)) == NULL) { 78 (void) fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser); 79 return(-1); 80 } 81 82 /* Validate remote hostname. */ 83 if (strcmp(*ahost, "localhost") != 0) { 84 if (((hp = gethostbyname2(*ahost, AF_INET)) == NULL) && 85 ((hp = gethostbyname2(*ahost, AF_INET6)) == NULL)) { 86 herror(*ahost); 87 return(-1); 88 } 89 *ahost = hp->h_name; 90 } 91 92 /* Get a socketpair we'll use for stdin and stdout. */ 93 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) < 0) { 94 perror("rcmdsh: socketpair"); 95 return(-1); 96 } 97 98 cpid = fork(); 99 if (cpid < 0) { 100 perror("rcmdsh: fork failed"); 101 return(-1); 102 } else if (cpid == 0) { 103 /* 104 * Child. We use sp[1] to be stdin/stdout, and close sp[0]. 105 */ 106 (void) close(sp[0]); 107 if (dup2(sp[1], 0) < 0 || dup2(0, 1) < 0) { 108 perror("rcmdsh: dup2 failed"); 109 _exit(255); 110 } 111 /* Fork again to lose parent. */ 112 cpid = fork(); 113 if (cpid < 0) { 114 perror("rcmdsh: fork to lose parent failed"); 115 _exit(255); 116 } 117 if (cpid > 0) 118 _exit(0); 119 120 /* In grandchild here. Become local user for rshprog. */ 121 if (setuid(pw->pw_uid)) { 122 (void) fprintf(stderr, "rcmdsh: setuid(%u): %s\n", 123 pw->pw_uid, strerror(errno)); 124 _exit(255); 125 } 126 127 /* 128 * If remote host is "localhost" and local and remote user 129 * are the same, avoid running remote shell for efficiency. 130 */ 131 if (!strcmp(*ahost, "localhost") && !strcmp(locuser, remuser)) { 132 char *argv[4]; 133 if (pw->pw_shell[0] == '\0') 134 rshprog = _PATH_BSHELL; 135 else 136 rshprog = pw->pw_shell; 137 p = strrchr(rshprog, '/'); 138 argv[0] = p ? p + 1 : rshprog; 139 argv[1] = "-c"; 140 argv[2] = (char *)cmd; 141 argv[3] = NULL; 142 execvp(rshprog, argv); 143 } else if ((p = strchr(rshprog, ' ')) == NULL) { 144 /* simple case */ 145 char *argv[6]; 146 p = strrchr(rshprog, '/'); 147 argv[0] = p ? p + 1 : rshprog; 148 argv[1] = "-l"; 149 argv[2] = (char *)remuser; 150 argv[3] = *ahost; 151 argv[4] = (char *)cmd; 152 argv[5] = NULL; 153 execvp(rshprog, argv); 154 } else { 155 /* must pull args out of rshprog and dyn alloc argv */ 156 char **argv, **ap; 157 int n; 158 for (n = 7; (p = strchr(++p, ' ')) != NULL; n++) 159 continue; 160 rshprog = strdup(rshprog); 161 ap = argv = malloc(sizeof(char *) * n); 162 if (rshprog == NULL || argv == NULL) { 163 perror("rcmdsh"); 164 _exit(255); 165 } 166 while ((p = strsep(&rshprog, " ")) != NULL) { 167 if (*p == '\0') 168 continue; 169 *ap++ = p; 170 } 171 if (ap != argv) /* all spaces?!? */ 172 rshprog = argv[0]; 173 if ((p = strrchr(argv[0], '/')) != NULL) 174 argv[0] = p + 1; 175 *ap++ = "-l"; 176 *ap++ = (char *)remuser; 177 *ap++ = *ahost; 178 *ap++ = (char *)cmd; 179 *ap++ = NULL; 180 execvp(rshprog, argv); 181 } 182 (void) fprintf(stderr, "rcmdsh: execvp %s failed: %s\n", 183 rshprog, strerror(errno)); 184 _exit(255); 185 } else { 186 /* Parent. close sp[1], return sp[0]. */ 187 (void) close(sp[1]); 188 /* Reap child. */ 189 (void) wait(NULL); 190 return(sp[0]); 191 } 192 /* NOTREACHED */ 193 } 194