1 /* $OpenBSD: rcmdsh.c,v 1.14 2015/03/23 22:29:32 halex 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 ssh(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)) || 78 (hp = gethostbyname2(*ahost, AF_INET6))) 79 *ahost = hp->h_name; 80 } 81 82 /* Get a socketpair we'll use for stdin and stdout. */ 83 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) < 0) { 84 perror("rcmdsh: socketpair"); 85 return(-1); 86 } 87 88 cpid = fork(); 89 if (cpid < 0) { 90 perror("rcmdsh: fork failed"); 91 return(-1); 92 } else if (cpid == 0) { 93 /* 94 * Child. We use sp[1] to be stdin/stdout, and close sp[0]. 95 */ 96 (void) close(sp[0]); 97 if (dup2(sp[1], 0) < 0 || dup2(0, 1) < 0) { 98 perror("rcmdsh: dup2 failed"); 99 _exit(255); 100 } 101 /* Fork again to lose parent. */ 102 cpid = fork(); 103 if (cpid < 0) { 104 perror("rcmdsh: fork to lose parent failed"); 105 _exit(255); 106 } 107 if (cpid > 0) 108 _exit(0); 109 110 /* In grandchild here. Become local user for rshprog. */ 111 if (setuid(pw->pw_uid)) { 112 (void) fprintf(stderr, "rcmdsh: setuid(%u): %s\n", 113 pw->pw_uid, strerror(errno)); 114 _exit(255); 115 } 116 117 /* 118 * If remote host is "localhost" and local and remote user 119 * are the same, avoid running remote shell for efficiency. 120 */ 121 if (!strcmp(*ahost, "localhost") && !strcmp(locuser, remuser)) { 122 char *argv[4]; 123 if (pw->pw_shell[0] == '\0') 124 rshprog = _PATH_BSHELL; 125 else 126 rshprog = pw->pw_shell; 127 p = strrchr(rshprog, '/'); 128 argv[0] = p ? p + 1 : rshprog; 129 argv[1] = "-c"; 130 argv[2] = (char *)cmd; 131 argv[3] = NULL; 132 execvp(rshprog, argv); 133 } else if ((p = strchr(rshprog, ' ')) == NULL) { 134 /* simple case */ 135 char *argv[6]; 136 p = strrchr(rshprog, '/'); 137 argv[0] = p ? p + 1 : rshprog; 138 argv[1] = "-l"; 139 argv[2] = (char *)remuser; 140 argv[3] = *ahost; 141 argv[4] = (char *)cmd; 142 argv[5] = NULL; 143 execvp(rshprog, argv); 144 } else { 145 /* must pull args out of rshprog and dyn alloc argv */ 146 char **argv, **ap; 147 int n; 148 for (n = 7; (p = strchr(++p, ' ')) != NULL; n++) 149 continue; 150 rshprog = strdup(rshprog); 151 ap = argv = calloc(sizeof(char *), n); 152 if (rshprog == NULL || argv == NULL) { 153 perror("rcmdsh"); 154 _exit(255); 155 } 156 while ((p = strsep(&rshprog, " ")) != NULL) { 157 if (*p == '\0') 158 continue; 159 *ap++ = p; 160 } 161 if (ap != argv) /* all spaces?!? */ 162 rshprog = argv[0]; 163 if ((p = strrchr(argv[0], '/')) != NULL) 164 argv[0] = p + 1; 165 *ap++ = "-l"; 166 *ap++ = (char *)remuser; 167 *ap++ = *ahost; 168 *ap++ = (char *)cmd; 169 *ap++ = NULL; 170 execvp(rshprog, argv); 171 } 172 (void) fprintf(stderr, "rcmdsh: execvp %s failed: %s\n", 173 rshprog, strerror(errno)); 174 _exit(255); 175 } else { 176 /* Parent. close sp[1], return sp[0]. */ 177 (void) close(sp[1]); 178 /* Reap child. */ 179 (void) wait(NULL); 180 return(sp[0]); 181 } 182 /* NOTREACHED */ 183 } 184