1/* $OpenBSD: rcmdsh.c,v 1.20 2019/06/28 13:32:42 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 <limits.h> 42#include <netdb.h> 43#include <stdio.h> 44#include <stdlib.h> 45#include <string.h> 46#include <pwd.h> 47#include <paths.h> 48#include <unistd.h> 49 50/* 51 * This is a replacement rcmd() function that uses the ssh(1) 52 * program in place of a direct rcmd(3) function call so as to 53 * avoid having to be root. Note that rport is ignored. 54 */ 55int 56rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser, 57 const char *cmd, char *rshprog) 58{ 59 static char hbuf[HOST_NAME_MAX+1]; 60 struct addrinfo hint, *res; 61 int sp[2]; 62 pid_t cpid; 63 char *p, pwbuf[_PW_BUF_LEN]; 64 struct passwd pwstore, *pw = NULL; 65 66 /* What rsh/shell to use. */ 67 if (rshprog == NULL) 68 rshprog = _PATH_RSH; 69 70 /* locuser must exist on this host. */ 71 getpwnam_r(locuser, &pwstore, pwbuf, sizeof(pwbuf), &pw); 72 if (pw == NULL) { 73 (void) fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser); 74 return(-1); 75 } 76 77 /* Validate remote hostname. */ 78 if (strcmp(*ahost, "localhost") != 0) { 79 memset(&hint, 0, sizeof(hint)); 80 hint.ai_family = PF_UNSPEC; 81 hint.ai_flags = AI_CANONNAME; 82 if (getaddrinfo(*ahost, NULL, &hint, &res) == 0) { 83 if (res->ai_canonname) { 84 strlcpy(hbuf, res->ai_canonname, sizeof(hbuf)); 85 *ahost = hbuf; 86 } 87 freeaddrinfo(res); 88 } 89 } 90 91 /* Get a socketpair we'll use for stdin and stdout. */ 92 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) { 93 perror("rcmdsh: socketpair"); 94 return(-1); 95 } 96 97 cpid = fork(); 98 if (cpid == -1) { 99 perror("rcmdsh: fork failed"); 100 return(-1); 101 } else if (cpid == 0) { 102 /* 103 * Child. We use sp[1] to be stdin/stdout, and close sp[0]. 104 */ 105 (void) close(sp[0]); 106 if (dup2(sp[1], 0) == -1 || dup2(0, 1) == -1) { 107 perror("rcmdsh: dup2 failed"); 108 _exit(255); 109 } 110 /* Fork again to lose parent. */ 111 cpid = fork(); 112 if (cpid == -1) { 113 perror("rcmdsh: fork to lose parent failed"); 114 _exit(255); 115 } 116 if (cpid > 0) 117 _exit(0); 118 119 /* In grandchild here. Become local user for rshprog. */ 120 if (setuid(pw->pw_uid)) { 121 (void) fprintf(stderr, "rcmdsh: setuid(%u): %s\n", 122 pw->pw_uid, strerror(errno)); 123 _exit(255); 124 } 125 126 /* 127 * If remote host is "localhost" and local and remote user 128 * are the same, avoid running remote shell for efficiency. 129 */ 130 if (!strcmp(*ahost, "localhost") && !strcmp(locuser, remuser)) { 131 char *argv[4]; 132 if (pw->pw_shell[0] == '\0') 133 rshprog = _PATH_BSHELL; 134 else 135 rshprog = pw->pw_shell; 136 p = strrchr(rshprog, '/'); 137 argv[0] = p ? p + 1 : rshprog; 138 argv[1] = "-c"; 139 argv[2] = (char *)cmd; 140 argv[3] = NULL; 141 execvp(rshprog, argv); 142 } else if ((p = strchr(rshprog, ' ')) == NULL) { 143 /* simple case */ 144 char *argv[6]; 145 p = strrchr(rshprog, '/'); 146 argv[0] = p ? p + 1 : rshprog; 147 argv[1] = "-l"; 148 argv[2] = (char *)remuser; 149 argv[3] = *ahost; 150 argv[4] = (char *)cmd; 151 argv[5] = NULL; 152 execvp(rshprog, argv); 153 } else { 154 /* must pull args out of rshprog and dyn alloc argv */ 155 char **argv, **ap; 156 int n; 157 for (n = 7; (p = strchr(++p, ' ')) != NULL; n++) 158 continue; 159 rshprog = strdup(rshprog); 160 ap = argv = calloc(sizeof(char *), n); 161 if (rshprog == NULL || argv == NULL) { 162 perror("rcmdsh"); 163 _exit(255); 164 } 165 while ((p = strsep(&rshprog, " ")) != NULL) { 166 if (*p == '\0') 167 continue; 168 *ap++ = p; 169 } 170 if (ap != argv) /* all spaces?!? */ 171 rshprog = argv[0]; 172 if ((p = strrchr(argv[0], '/')) != NULL) 173 argv[0] = p + 1; 174 *ap++ = "-l"; 175 *ap++ = (char *)remuser; 176 *ap++ = *ahost; 177 *ap++ = (char *)cmd; 178 *ap++ = NULL; 179 execvp(rshprog, argv); 180 } 181 (void) fprintf(stderr, "rcmdsh: execvp %s failed: %s\n", 182 rshprog, strerror(errno)); 183 _exit(255); 184 } else { 185 /* Parent. close sp[1], return sp[0]. */ 186 (void) close(sp[1]); 187 /* Reap child. */ 188 while (waitpid(cpid, NULL, 0) == -1 && errno == EINTR) 189 ; 190 return(sp[0]); 191 } 192 /* NOTREACHED */ 193} 194DEF_WEAK(rcmdsh); 195