1 /* $OpenBSD: rcmdsh.c,v 1.10 2005/03/25 13:24:12 otto 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 1.10 2005/03/25 13:24:12 otto 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(char **ahost, int rport, const char *locuser, const char *remuser, 61 const char *cmd, char *rshprog) 62 { 63 struct hostent *hp; 64 int sp[2]; 65 pid_t cpid; 66 char *p; 67 struct passwd *pw; 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 if (((hp = gethostbyname2(*ahost, AF_INET)) == NULL) && 82 ((hp = gethostbyname2(*ahost, AF_INET6)) == NULL)) { 83 herror(*ahost); 84 return(-1); 85 } 86 *ahost = hp->h_name; 87 } 88 89 /* Get a socketpair we'll use for stdin and stdout. */ 90 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) < 0) { 91 perror("rcmdsh: socketpair"); 92 return(-1); 93 } 94 95 cpid = fork(); 96 if (cpid < 0) { 97 perror("rcmdsh: fork failed"); 98 return(-1); 99 } else if (cpid == 0) { 100 /* 101 * Child. We use sp[1] to be stdin/stdout, and close sp[0]. 102 */ 103 (void) close(sp[0]); 104 if (dup2(sp[1], 0) < 0 || dup2(0, 1) < 0) { 105 perror("rcmdsh: dup2 failed"); 106 _exit(255); 107 } 108 /* Fork again to lose parent. */ 109 cpid = fork(); 110 if (cpid < 0) { 111 perror("rcmdsh: fork to lose parent failed"); 112 _exit(255); 113 } 114 if (cpid > 0) 115 _exit(0); 116 117 /* In grandchild here. Become local user for rshprog. */ 118 if (setuid(pw->pw_uid)) { 119 (void) fprintf(stderr, "rcmdsh: setuid(%u): %s\n", 120 pw->pw_uid, strerror(errno)); 121 _exit(255); 122 } 123 124 /* 125 * If remote host is "localhost" and local and remote user 126 * are the same, avoid running remote shell for efficiency. 127 */ 128 if (!strcmp(*ahost, "localhost") && !strcmp(locuser, remuser)) { 129 char *argv[4]; 130 if (pw->pw_shell[0] == '\0') 131 rshprog = _PATH_BSHELL; 132 else 133 rshprog = pw->pw_shell; 134 p = strrchr(rshprog, '/'); 135 argv[0] = p ? p + 1 : rshprog; 136 argv[1] = "-c"; 137 argv[2] = (char *)cmd; 138 argv[3] = NULL; 139 execvp(rshprog, argv); 140 } else if ((p = strchr(rshprog, ' ')) == NULL) { 141 /* simple case */ 142 char *argv[6]; 143 p = strrchr(rshprog, '/'); 144 argv[0] = p ? p + 1 : rshprog; 145 argv[1] = "-l"; 146 argv[2] = (char *)remuser; 147 argv[3] = *ahost; 148 argv[4] = (char *)cmd; 149 argv[5] = NULL; 150 execvp(rshprog, argv); 151 } else { 152 /* must pull args out of rshprog and dyn alloc argv */ 153 char **argv, **ap; 154 int n; 155 for (n = 7; (p = strchr(++p, ' ')) != NULL; n++) 156 continue; 157 rshprog = strdup(rshprog); 158 ap = argv = malloc(sizeof(char *) * n); 159 if (rshprog == NULL || argv == NULL) { 160 perror("rcmdsh"); 161 _exit(255); 162 } 163 while ((p = strsep(&rshprog, " ")) != NULL) { 164 if (*p == '\0') 165 continue; 166 *ap++ = p; 167 } 168 if (ap != argv) /* all spaces?!? */ 169 rshprog = argv[0]; 170 if ((p = strrchr(argv[0], '/')) != NULL) 171 argv[0] = p + 1; 172 *ap++ = "-l"; 173 *ap++ = (char *)remuser; 174 *ap++ = *ahost; 175 *ap++ = (char *)cmd; 176 *ap++ = NULL; 177 execvp(rshprog, argv); 178 } 179 (void) fprintf(stderr, "rcmdsh: execvp %s failed: %s\n", 180 rshprog, strerror(errno)); 181 _exit(255); 182 } else { 183 /* Parent. close sp[1], return sp[0]. */ 184 (void) close(sp[1]); 185 /* Reap child. */ 186 (void) wait(NULL); 187 return(sp[0]); 188 } 189 /* NOTREACHED */ 190 } 191