1 /* $NetBSD: openpam_borrow_cred.c,v 1.5 2023/06/30 21:46:20 christos Exp $ */ 2 3 /*- 4 * Copyright (c) 2002-2003 Networks Associates Technology, Inc. 5 * Copyright (c) 2004-2011 Dag-Erling Smørgrav 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 38 #ifdef HAVE_CONFIG_H 39 # include "config.h" 40 #endif 41 42 #include <sys/cdefs.h> 43 __RCSID("$NetBSD: openpam_borrow_cred.c,v 1.5 2023/06/30 21:46:20 christos Exp $"); 44 45 #include <sys/param.h> 46 47 #include <grp.h> 48 #include <limits.h> 49 #include <pwd.h> 50 #include <stdlib.h> 51 #include <unistd.h> 52 53 #include <security/pam_appl.h> 54 55 #include "openpam_impl.h" 56 #include "openpam_cred.h" 57 58 /* 59 * OpenPAM extension 60 * 61 * Temporarily borrow user credentials 62 */ 63 64 int 65 openpam_borrow_cred(pam_handle_t *pamh, 66 const struct passwd *pwd) 67 { 68 struct pam_saved_cred *scred; 69 const void *scredp; 70 int r; 71 72 ENTERN(pwd->pw_uid); 73 r = pam_get_data(pamh, PAM_SAVED_CRED, &scredp); 74 if (r == PAM_SUCCESS && scredp != NULL) { 75 openpam_log(PAM_LOG_LIBDEBUG, 76 "already operating under borrowed credentials"); 77 RETURNC(PAM_SYSTEM_ERR); 78 } 79 if (geteuid() != 0 && geteuid() != pwd->pw_uid) { 80 openpam_log(PAM_LOG_LIBDEBUG, "called with non-zero euid: %d", 81 (int)geteuid()); 82 RETURNC(PAM_PERM_DENIED); 83 } 84 scred = calloc((size_t)1, sizeof *scred); 85 if (scred == NULL) 86 RETURNC(PAM_BUF_ERR); 87 scred->euid = geteuid(); 88 scred->egid = getegid(); 89 r = getgroups(NGROUPS_MAX, scred->groups); 90 if (r < 0) { 91 FREE(scred); 92 RETURNC(PAM_SYSTEM_ERR); 93 } 94 scred->ngroups = r; 95 r = pam_set_data(pamh, PAM_SAVED_CRED, scred, &openpam_free_data); 96 if (r != PAM_SUCCESS) { 97 FREE(scred); 98 RETURNC(r); 99 } 100 if (geteuid() == pwd->pw_uid) 101 RETURNC(PAM_SUCCESS); 102 if (initgroups(pwd->pw_name, pwd->pw_gid) < 0 || 103 setegid(pwd->pw_gid) < 0 || seteuid(pwd->pw_uid) < 0) { 104 openpam_restore_cred(pamh); 105 RETURNC(PAM_SYSTEM_ERR); 106 } 107 RETURNC(PAM_SUCCESS); 108 } 109 110 /* 111 * Error codes: 112 * 113 * =pam_set_data 114 * PAM_SYSTEM_ERR 115 * PAM_BUF_ERR 116 * PAM_PERM_DENIED 117 */ 118 119 /** 120 * The =openpam_borrow_cred function saves the current credentials and 121 * switches to those of the user specified by its =pwd argument. 122 * The affected credentials are the effective UID, the effective GID, and 123 * the group access list. 124 * The original credentials can be restored using =openpam_restore_cred. 125 * 126 * >setegid 2 127 * >seteuid 2 128 * >setgroups 2 129 */ 130