1/*- 2 * Copyright (c) 2002 Jacques A. Vidrine <nectar@FreeBSD.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26#include <sys/cdefs.h> 27__FBSDID("$FreeBSD$"); 28 29#include <sys/param.h> 30#include <errno.h> 31#include <stdio.h> 32#include <stdlib.h> 33#include <string.h> 34#include <unistd.h> 35 36#include <krb5.h> 37 38#define PAM_SM_AUTH 39#define PAM_SM_CRED 40#include <security/pam_appl.h> 41#include <security/pam_modules.h> 42#include <security/pam_mod_misc.h> 43 44static const char superuser[] = "root"; 45 46static long get_su_principal(krb5_context, const char *, const char *, 47 char **, krb5_principal *); 48static int auth_krb5(pam_handle_t *, krb5_context, const char *, 49 krb5_principal); 50 51PAM_EXTERN int 52pam_sm_authenticate(pam_handle_t *pamh, int flags __unused, 53 int argc __unused, const char *argv[] __unused) 54{ 55 krb5_context context; 56 krb5_principal su_principal; 57 const char *user; 58 const void *ruser; 59 char *su_principal_name; 60 long rv; 61 int pamret; 62 63 pamret = pam_get_user(pamh, &user, NULL); 64 if (pamret != PAM_SUCCESS) 65 return (pamret); 66 PAM_LOG("Got user: %s", user); 67 pamret = pam_get_item(pamh, PAM_RUSER, &ruser); 68 if (pamret != PAM_SUCCESS) 69 return (pamret); 70 PAM_LOG("Got ruser: %s", (const char *)ruser); 71 rv = krb5_init_context(&context); 72 if (rv != 0) { 73 PAM_LOG("krb5_init_context failed: %s", 74 krb5_get_err_text(context, rv)); 75 return (PAM_SERVICE_ERR); 76 } 77 rv = get_su_principal(context, user, ruser, &su_principal_name, &su_principal); 78 if (rv != 0) 79 return (PAM_AUTH_ERR); 80 PAM_LOG("kuserok: %s -> %s", su_principal_name, user); 81 rv = krb5_kuserok(context, su_principal, user); 82 pamret = rv ? auth_krb5(pamh, context, su_principal_name, su_principal) : PAM_AUTH_ERR; 83 free(su_principal_name); 84 krb5_free_principal(context, su_principal); 85 krb5_free_context(context); 86 return (pamret); 87} 88 89PAM_EXTERN int 90pam_sm_setcred(pam_handle_t *pamh __unused, int flags __unused, 91 int ac __unused, const char *av[] __unused) 92{ 93 94 return (PAM_SUCCESS); 95} 96 97/* Authenticate using Kerberos 5. 98 * pamh -- The PAM handle. 99 * context -- An initialized krb5_context. 100 * su_principal_name -- The target principal name, used only for password prompts. 101 * If NULL, the password prompts will not include a principal 102 * name. 103 * su_principal -- The target krb5_principal. 104 * Note that a valid keytab in the default location with a host entry 105 * must be available, and that the PAM application must have sufficient 106 * privileges to access it. 107 * Returns PAM_SUCCESS if authentication was successful, or an appropriate 108 * PAM error code if it was not. 109 */ 110static int 111auth_krb5(pam_handle_t *pamh, krb5_context context, const char *su_principal_name, 112 krb5_principal su_principal) 113{ 114 krb5_creds creds; 115 krb5_get_init_creds_opt gic_opt; 116 krb5_verify_init_creds_opt vic_opt; 117 const char *pass; 118 char *prompt; 119 long rv; 120 int pamret; 121 122 prompt = NULL; 123 krb5_get_init_creds_opt_init(&gic_opt); 124 krb5_verify_init_creds_opt_init(&vic_opt); 125 if (su_principal_name != NULL) 126 (void)asprintf(&prompt, "Password for %s:", su_principal_name); 127 else 128 (void)asprintf(&prompt, "Password:"); 129 if (prompt == NULL) 130 return (PAM_BUF_ERR); 131 pass = NULL; 132 pamret = pam_get_authtok(pamh, PAM_AUTHTOK, &pass, prompt); 133 free(prompt); 134 if (pamret != PAM_SUCCESS) 135 return (pamret); 136 rv = krb5_get_init_creds_password(context, &creds, su_principal, 137 pass, NULL, NULL, 0, NULL, &gic_opt); 138 if (rv != 0) { 139 PAM_LOG("krb5_get_init_creds_password: %s", 140 krb5_get_err_text(context, rv)); 141 return (PAM_AUTH_ERR); 142 } 143 krb5_verify_init_creds_opt_set_ap_req_nofail(&vic_opt, 1); 144 rv = krb5_verify_init_creds(context, &creds, NULL, NULL, NULL, 145 &vic_opt); 146 krb5_free_cred_contents(context, &creds); 147 if (rv != 0) { 148 PAM_LOG("krb5_verify_init_creds: %s", 149 krb5_get_err_text(context, rv)); 150 return (PAM_AUTH_ERR); 151 } 152 return (PAM_SUCCESS); 153} 154 155/* Determine the target principal given the current user and the target user. 156 * context -- An initialized krb5_context. 157 * target_user -- The target username. 158 * current_user -- The current username. 159 * su_principal_name -- (out) The target principal name. 160 * su_principal -- (out) The target krb5_principal. 161 * When the target user is `root', the target principal will be a `root 162 * instance', e.g. `luser/root@REA.LM'. Otherwise, the target principal 163 * will simply be the current user's default principal name. Note that 164 * in any case, if KRB5CCNAME is set and a credentials cache exists, the 165 * principal name found there will be the `starting point', rather than 166 * the ruser parameter. 167 * 168 * Returns 0 for success, or a com_err error code on failure. 169 */ 170static long 171get_su_principal(krb5_context context, const char *target_user, const char *current_user, 172 char **su_principal_name, krb5_principal *su_principal) 173{ 174 krb5_principal default_principal; 175 krb5_ccache ccache; 176 char *principal_name, *ccname, *p; 177 long rv; 178 uid_t euid, ruid; 179 180 *su_principal = NULL; 181 default_principal = NULL; 182 /* Unless KRB5CCNAME was explicitly set, we won't really be able 183 * to look at the credentials cache since krb5_cc_default will 184 * look at getuid(). 185 */ 186 ruid = getuid(); 187 euid = geteuid(); 188 rv = seteuid(ruid); 189 if (rv != 0) 190 return (errno); 191 p = getenv("KRB5CCNAME"); 192 if (p != NULL) 193 ccname = strdup(p); 194 else 195 (void)asprintf(&ccname, "%s%lu", KRB5_DEFAULT_CCROOT, (unsigned long)ruid); 196 if (ccname == NULL) 197 return (errno); 198 rv = krb5_cc_resolve(context, ccname, &ccache); 199 free(ccname); 200 if (rv == 0) { 201 rv = krb5_cc_get_principal(context, ccache, &default_principal); 202 krb5_cc_close(context, ccache); 203 if (rv != 0) 204 default_principal = NULL; /* just to be safe */ 205 } 206 rv = seteuid(euid); 207 if (rv != 0) 208 return (errno); 209 if (default_principal == NULL) { 210 rv = krb5_make_principal(context, &default_principal, NULL, current_user, NULL); 211 if (rv != 0) { 212 PAM_LOG("Could not determine default principal name."); 213 return (rv); 214 } 215 } 216 /* Now that we have some principal, if the target account is 217 * `root', then transform it into a `root' instance, e.g. 218 * `user@REA.LM' -> `user/root@REA.LM'. 219 */ 220 rv = krb5_unparse_name(context, default_principal, &principal_name); 221 krb5_free_principal(context, default_principal); 222 if (rv != 0) { 223 PAM_LOG("krb5_unparse_name: %s", 224 krb5_get_err_text(context, rv)); 225 return (rv); 226 } 227 PAM_LOG("Default principal name: %s", principal_name); 228 if (strcmp(target_user, superuser) == 0) { 229 p = strrchr(principal_name, '@'); 230 if (p == NULL) { 231 PAM_LOG("malformed principal name `%s'", principal_name); 232 free(principal_name); 233 return (rv); 234 } 235 *p++ = '\0'; 236 *su_principal_name = NULL; 237 (void)asprintf(su_principal_name, "%s/%s@%s", principal_name, superuser, p); 238 free(principal_name); 239 } else 240 *su_principal_name = principal_name; 241 242 if (*su_principal_name == NULL) 243 return (errno); 244 rv = krb5_parse_name(context, *su_principal_name, &default_principal); 245 if (rv != 0) { 246 PAM_LOG("krb5_parse_name `%s': %s", *su_principal_name, 247 krb5_get_err_text(context, rv)); 248 free(*su_principal_name); 249 return (rv); 250 } 251 PAM_LOG("Target principal name: %s", *su_principal_name); 252 *su_principal = default_principal; 253 return (0); 254} 255 256PAM_MODULE_ENTRY("pam_ksu"); 257