1 /* $OpenBSD: rcmdsh.c,v 1.12 2007/09/02 15:19:17 deraadt 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/types.h> 37 #include <sys/socket.h> 38 #include <sys/wait.h> 39 #include <signal.h> 40 #include <errno.h> 41 #include <netdb.h> 42 #include <stdio.h> 43 #include <stdlib.h> 44 #include <string.h> 45 #include <pwd.h> 46 #include <paths.h> 47 #include <unistd.h> 48 49 /* 50 * This is a replacement rcmd() function that uses the rsh(1) 51 * program in place of a direct rcmd(3) function call so as to 52 * avoid having to be root. Note that rport is ignored. 53 */ 54 /* ARGSUSED */ 55 int 56 rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser, 57 const char *cmd, char *rshprog) 58 { 59 struct hostent *hp; 60 int sp[2]; 61 pid_t cpid; 62 char *p; 63 struct passwd *pw; 64 65 /* What rsh/shell to use. */ 66 if (rshprog == NULL) 67 rshprog = _PATH_RSH; 68 69 /* locuser must exist on this host. */ 70 if ((pw = getpwnam(locuser)) == NULL) { 71 (void) fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser); 72 return(-1); 73 } 74 75 /* Validate remote hostname. */ 76 if (strcmp(*ahost, "localhost") != 0) { 77 if (((hp = gethostbyname2(*ahost, AF_INET)) == NULL) && 78 ((hp = gethostbyname2(*ahost, AF_INET6)) == NULL)) { 79 herror(*ahost); 80 return(-1); 81 } 82 *ahost = hp->h_name; 83 } 84 85 /* Get a socketpair we'll use for stdin and stdout. */ 86 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) < 0) { 87 perror("rcmdsh: socketpair"); 88 return(-1); 89 } 90 91 cpid = fork(); 92 if (cpid < 0) { 93 perror("rcmdsh: fork failed"); 94 return(-1); 95 } else if (cpid == 0) { 96 /* 97 * Child. We use sp[1] to be stdin/stdout, and close sp[0]. 98 */ 99 (void) close(sp[0]); 100 if (dup2(sp[1], 0) < 0 || dup2(0, 1) < 0) { 101 perror("rcmdsh: dup2 failed"); 102 _exit(255); 103 } 104 /* Fork again to lose parent. */ 105 cpid = fork(); 106 if (cpid < 0) { 107 perror("rcmdsh: fork to lose parent failed"); 108 _exit(255); 109 } 110 if (cpid > 0) 111 _exit(0); 112 113 /* In grandchild here. Become local user for rshprog. */ 114 if (setuid(pw->pw_uid)) { 115 (void) fprintf(stderr, "rcmdsh: setuid(%u): %s\n", 116 pw->pw_uid, strerror(errno)); 117 _exit(255); 118 } 119 120 /* 121 * If remote host is "localhost" and local and remote user 122 * are the same, avoid running remote shell for efficiency. 123 */ 124 if (!strcmp(*ahost, "localhost") && !strcmp(locuser, remuser)) { 125 char *argv[4]; 126 if (pw->pw_shell[0] == '\0') 127 rshprog = _PATH_BSHELL; 128 else 129 rshprog = pw->pw_shell; 130 p = strrchr(rshprog, '/'); 131 argv[0] = p ? p + 1 : rshprog; 132 argv[1] = "-c"; 133 argv[2] = (char *)cmd; 134 argv[3] = NULL; 135 execvp(rshprog, argv); 136 } else if ((p = strchr(rshprog, ' ')) == NULL) { 137 /* simple case */ 138 char *argv[6]; 139 p = strrchr(rshprog, '/'); 140 argv[0] = p ? p + 1 : rshprog; 141 argv[1] = "-l"; 142 argv[2] = (char *)remuser; 143 argv[3] = *ahost; 144 argv[4] = (char *)cmd; 145 argv[5] = NULL; 146 execvp(rshprog, argv); 147 } else { 148 /* must pull args out of rshprog and dyn alloc argv */ 149 char **argv, **ap; 150 int n; 151 for (n = 7; (p = strchr(++p, ' ')) != NULL; n++) 152 continue; 153 rshprog = strdup(rshprog); 154 ap = argv = calloc(sizeof(char *), n); 155 if (rshprog == NULL || argv == NULL) { 156 perror("rcmdsh"); 157 _exit(255); 158 } 159 while ((p = strsep(&rshprog, " ")) != NULL) { 160 if (*p == '\0') 161 continue; 162 *ap++ = p; 163 } 164 if (ap != argv) /* all spaces?!? */ 165 rshprog = argv[0]; 166 if ((p = strrchr(argv[0], '/')) != NULL) 167 argv[0] = p + 1; 168 *ap++ = "-l"; 169 *ap++ = (char *)remuser; 170 *ap++ = *ahost; 171 *ap++ = (char *)cmd; 172 *ap++ = NULL; 173 execvp(rshprog, argv); 174 } 175 (void) fprintf(stderr, "rcmdsh: execvp %s failed: %s\n", 176 rshprog, strerror(errno)); 177 _exit(255); 178 } else { 179 /* Parent. close sp[1], return sp[0]. */ 180 (void) close(sp[1]); 181 /* Reap child. */ 182 (void) wait(NULL); 183 return(sp[0]); 184 } 185 /* NOTREACHED */ 186 } 187