su.c revision 1.4
1 /* $NetBSD: su.c,v 1.4 2013/12/27 20:10:20 christos Exp $ */ 2 3 /*- 4 * Copyright (c) 2002-2003 Networks Associates Technology, Inc. 5 * Copyright (c) 2004-2011 Dag-Erling Smrgrav 6 * All rights reserved. 7 * 8 * This software was developed for the FreeBSD Project by ThinkSec AS and 9 * Network Associates Laboratories, the Security Research Division of 10 * Network Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 11 * ("CBOSS"), as part of the DARPA CHATS research program. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. The name of the author may not be used to endorse or promote 22 * products derived from this software without specific prior written 23 * permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35 * SUCH DAMAGE. 36 * 37 * Id: su.c 648 2013-03-05 17:54:27Z des 38 */ 39 40 #ifdef HAVE_CONFIG_H 41 # include "config.h" 42 #endif 43 44 #include <sys/param.h> 45 #include <sys/wait.h> 46 47 #include <err.h> 48 #include <grp.h> 49 #include <pwd.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 #include <syslog.h> 54 #include <unistd.h> 55 56 #include <security/pam_appl.h> 57 #include <security/openpam.h> /* for openpam_ttyconv() */ 58 59 extern char **environ; 60 61 static pam_handle_t *pamh; 62 static struct pam_conv pamc; 63 64 static void 65 usage(void) 66 { 67 68 fprintf(stderr, "usage: su [login [args]]\n"); 69 exit(1); 70 } 71 72 int 73 main(int argc, char *argv[]) 74 { 75 char hostname[MAXHOSTNAMELEN]; 76 const char *user, *tty; 77 const void *item; 78 char **args, **pam_envlist, **pam_env; 79 struct passwd *pwd; 80 int o, pam_err, status; 81 pid_t pid; 82 83 while ((o = getopt(argc, argv, "")) != -1) 84 switch (o) { 85 default: 86 usage(); 87 } 88 89 argc -= optind; 90 argv += optind; 91 92 if (argc > 0) { 93 user = *argv; 94 --argc; 95 ++argv; 96 } else { 97 user = "root"; 98 } 99 100 /* initialize PAM */ 101 pamc.conv = &openpam_ttyconv; 102 pam_start("su", user, &pamc, &pamh); 103 104 /* set some items */ 105 gethostname(hostname, sizeof(hostname)); 106 if ((pam_err = pam_set_item(pamh, PAM_RHOST, hostname)) != PAM_SUCCESS) 107 goto pamerr; 108 user = getlogin(); 109 if ((pam_err = pam_set_item(pamh, PAM_RUSER, user)) != PAM_SUCCESS) 110 goto pamerr; 111 tty = ttyname(STDERR_FILENO); 112 if ((pam_err = pam_set_item(pamh, PAM_TTY, tty)) != PAM_SUCCESS) 113 goto pamerr; 114 115 /* authenticate the applicant */ 116 if ((pam_err = pam_authenticate(pamh, 0)) != PAM_SUCCESS) 117 goto pamerr; 118 if ((pam_err = pam_acct_mgmt(pamh, 0)) == PAM_NEW_AUTHTOK_REQD) 119 pam_err = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK); 120 if (pam_err != PAM_SUCCESS) 121 goto pamerr; 122 123 /* establish the requested credentials */ 124 if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS) 125 goto pamerr; 126 127 /* authentication succeeded; open a session */ 128 if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS) 129 goto pamerr; 130 131 /* get mapped user name; PAM may have changed it */ 132 pam_err = pam_get_item(pamh, PAM_USER, &item); 133 if (pam_err != PAM_SUCCESS || (pwd = getpwnam(user = item)) == NULL) 134 goto pamerr; 135 136 /* export PAM environment */ 137 if ((pam_envlist = pam_getenvlist(pamh)) != NULL) { 138 for (pam_env = pam_envlist; *pam_env != NULL; ++pam_env) { 139 putenv(*pam_env); 140 free(*pam_env); 141 } 142 free(pam_envlist); 143 } 144 145 /* build argument list */ 146 if ((args = calloc(argc + 2, sizeof *args)) == NULL) { 147 warn("calloc()"); 148 goto err; 149 } 150 *args = pwd->pw_shell; 151 memcpy(args + 1, argv, argc * sizeof *args); 152 153 /* fork and exec */ 154 switch ((pid = fork())) { 155 case -1: 156 warn("fork()"); 157 goto err; 158 case 0: 159 /* child: give up privs and start a shell */ 160 161 /* set uid and groups */ 162 if (initgroups(pwd->pw_name, pwd->pw_gid) == -1) { 163 warn("initgroups()"); 164 _exit(1); 165 } 166 if (setgid(pwd->pw_gid) == -1) { 167 warn("setgid()"); 168 _exit(1); 169 } 170 if (setuid(pwd->pw_uid) == -1) { 171 warn("setuid()"); 172 _exit(1); 173 } 174 execve(*args, args, environ); 175 warn("execve()"); 176 _exit(1); 177 default: 178 /* parent: wait for child to exit */ 179 waitpid(pid, &status, 0); 180 181 /* close the session and release PAM resources */ 182 pam_err = pam_close_session(pamh, 0); 183 pam_end(pamh, pam_err); 184 185 exit(WEXITSTATUS(status)); 186 } 187 188 pamerr: 189 fprintf(stderr, "Sorry\n"); 190 err: 191 pam_end(pamh, pam_err); 192 exit(1); 193 } 194
Indexes created Tue May 19 00:24:48 UTC 2026