pam_ksu.c revision 1.2
1 /* $NetBSD: pam_ksu.c,v 1.2 2004/12/12 08:18:46 christos Exp $ */ 2 3 /*- 4 * Copyright (c) 2002 Jacques A. Vidrine <nectar (at) FreeBSD.org> 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 the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 #include <sys/cdefs.h> 29 #ifdef __FreeBSD__ 30 __FBSDID("$FreeBSD: src/lib/libpam/modules/pam_ksu/pam_ksu.c,v 1.5 2004/02/10 10:13:21 des Exp $"); 31 #else 32 __RCSID("$NetBSD: pam_ksu.c,v 1.2 2004/12/12 08:18:46 christos Exp $"); 33 #endif 34 35 #include <sys/param.h> 36 #include <errno.h> 37 #include <stdio.h> 38 #include <stdlib.h> 39 #include <string.h> 40 #include <unistd.h> 41 42 #include <krb5/krb5.h> 43 44 #define PAM_SM_AUTH 45 #define PAM_SM_CRED 46 #include <security/pam_appl.h> 47 #include <security/pam_modules.h> 48 #include <security/pam_mod_misc.h> 49 50 static const char superuser[] = "root"; 51 52 static long get_su_principal(krb5_context, const char *, const char *, 53 char **, krb5_principal *); 54 static int auth_krb5(pam_handle_t *, krb5_context, const char *, 55 krb5_principal); 56 57 PAM_EXTERN int 58 pam_sm_authenticate(pam_handle_t *pamh, int flags __unused, 59 int argc __unused, const char *argv[] __unused) 60 { 61 krb5_context context; 62 krb5_principal su_principal; 63 const char *user; 64 const void *ruser; 65 char *su_principal_name; 66 long rv; 67 int pamret; 68 69 pamret = pam_get_user(pamh, &user, NULL); 70 if (pamret != PAM_SUCCESS) 71 return (pamret); 72 PAM_LOG("Got user: %s", user); 73 pamret = pam_get_item(pamh, PAM_RUSER, &ruser); 74 if (pamret != PAM_SUCCESS) 75 return (pamret); 76 PAM_LOG("Got ruser: %s", (const char *)ruser); 77 rv = krb5_init_context(&context); 78 if (rv != 0) { 79 PAM_LOG("krb5_init_context failed: %s", 80 krb5_get_err_text(context, rv)); 81 return (PAM_SERVICE_ERR); 82 } 83 rv = get_su_principal(context, user, ruser, &su_principal_name, &su_principal); 84 if (rv != 0) 85 return (PAM_AUTH_ERR); 86 PAM_LOG("kuserok: %s -> %s", su_principal_name, user); 87 rv = krb5_kuserok(context, su_principal, user); 88 pamret = rv ? auth_krb5(pamh, context, su_principal_name, su_principal) : PAM_AUTH_ERR; 89 free(su_principal_name); 90 krb5_free_principal(context, su_principal); 91 krb5_free_context(context); 92 return (pamret); 93 } 94 95 PAM_EXTERN int 96 pam_sm_setcred(pam_handle_t *pamh __unused, int flags __unused, 97 int ac __unused, const char *av[] __unused) 98 { 99 100 return (PAM_SUCCESS); 101 } 102 103 /* Authenticate using Kerberos 5. 104 * pamh -- The PAM handle. 105 * context -- An initialized krb5_context. 106 * su_principal_name -- The target principal name, used only for password prompts. 107 * If NULL, the password prompts will not include a principal 108 * name. 109 * su_principal -- The target krb5_principal. 110 * Note that a valid keytab in the default location with a host entry 111 * must be available, and that the PAM application must have sufficient 112 * privileges to access it. 113 * Returns PAM_SUCCESS if authentication was successful, or an appropriate 114 * PAM error code if it was not. 115 */ 116 static int 117 auth_krb5(pam_handle_t *pamh, krb5_context context, const char *su_principal_name, 118 krb5_principal su_principal) 119 { 120 krb5_creds creds; 121 krb5_get_init_creds_opt gic_opt; 122 krb5_verify_init_creds_opt vic_opt; 123 const char *pass; 124 char *prompt; 125 long rv; 126 int pamret; 127 128 prompt = NULL; 129 krb5_get_init_creds_opt_init(&gic_opt); 130 krb5_verify_init_creds_opt_init(&vic_opt); 131 if (su_principal_name != NULL) 132 (void)asprintf(&prompt, "Password for %s:", su_principal_name); 133 else 134 (void)asprintf(&prompt, "Password:"); 135 if (prompt == NULL) 136 return (PAM_BUF_ERR); 137 pass = NULL; 138 pamret = pam_get_authtok(pamh, PAM_AUTHTOK, &pass, prompt); 139 free(prompt); 140 if (pamret != PAM_SUCCESS) 141 return (pamret); 142 rv = krb5_get_init_creds_password(context, &creds, su_principal, 143 pass, NULL, NULL, 0, NULL, &gic_opt); 144 if (rv != 0) { 145 PAM_LOG("krb5_get_init_creds_password: %s", 146 krb5_get_err_text(context, rv)); 147 return (PAM_AUTH_ERR); 148 } 149 krb5_verify_init_creds_opt_set_ap_req_nofail(&vic_opt, 1); 150 rv = krb5_verify_init_creds(context, &creds, NULL, NULL, NULL, 151 &vic_opt); 152 krb5_free_cred_contents(context, &creds); 153 if (rv != 0) { 154 PAM_LOG("krb5_verify_init_creds: %s", 155 krb5_get_err_text(context, rv)); 156 return (PAM_AUTH_ERR); 157 } 158 return (PAM_SUCCESS); 159 } 160 161 /* Determine the target principal given the current user and the target user. 162 * context -- An initialized krb5_context. 163 * target_user -- The target username. 164 * current_user -- The current username. 165 * su_principal_name -- (out) The target principal name. 166 * su_principal -- (out) The target krb5_principal. 167 * When the target user is `root', the target principal will be a `root 168 * instance', e.g. `luser/root@REA.LM'. Otherwise, the target principal 169 * will simply be the current user's default principal name. Note that 170 * in any case, if KRB5CCNAME is set and a credentials cache exists, the 171 * principal name found there will be the `starting point', rather than 172 * the ruser parameter. 173 * 174 * Returns 0 for success, or a com_err error code on failure. 175 */ 176 static long 177 get_su_principal(krb5_context context, const char *target_user, const char *current_user, 178 char **su_principal_name, krb5_principal *su_principal) 179 { 180 krb5_principal default_principal; 181 krb5_ccache ccache; 182 char *principal_name, *ccname, *p; 183 long rv; 184 uid_t euid, ruid; 185 186 *su_principal = NULL; 187 default_principal = NULL; 188 /* Unless KRB5CCNAME was explicitly set, we won't really be able 189 * to look at the credentials cache since krb5_cc_default will 190 * look at getuid(). 191 */ 192 ruid = getuid(); 193 euid = geteuid(); 194 rv = seteuid(ruid); 195 if (rv != 0) 196 return (errno); 197 p = getenv("KRB5CCNAME"); 198 if (p != NULL) 199 ccname = strdup(p); 200 else 201 (void)asprintf(&ccname, "%s%lu", KRB5_DEFAULT_CCROOT, (unsigned long)ruid); 202 if (ccname == NULL) 203 return (errno); 204 rv = krb5_cc_resolve(context, ccname, &ccache); 205 free(ccname); 206 if (rv == 0) { 207 rv = krb5_cc_get_principal(context, ccache, &default_principal); 208 krb5_cc_close(context, ccache); 209 if (rv != 0) 210 default_principal = NULL; /* just to be safe */ 211 } 212 rv = seteuid(euid); 213 if (rv != 0) 214 return (errno); 215 if (default_principal == NULL) { 216 rv = krb5_make_principal(context, &default_principal, NULL, current_user, NULL); 217 if (rv != 0) { 218 PAM_LOG("Could not determine default principal name."); 219 return (rv); 220 } 221 } 222 /* Now that we have some principal, if the target account is 223 * `root', then transform it into a `root' instance, e.g. 224 * `user (at) REA.LM' -> `user/root@REA.LM'. 225 */ 226 rv = krb5_unparse_name(context, default_principal, &principal_name); 227 krb5_free_principal(context, default_principal); 228 if (rv != 0) { 229 PAM_LOG("krb5_unparse_name: %s", 230 krb5_get_err_text(context, rv)); 231 return (rv); 232 } 233 PAM_LOG("Default principal name: %s", principal_name); 234 if (strcmp(target_user, superuser) == 0) { 235 p = strrchr(principal_name, '@'); 236 if (p == NULL) { 237 PAM_LOG("malformed principal name `%s'", principal_name); 238 free(principal_name); 239 return (rv); 240 } 241 *p++ = '\0'; 242 *su_principal_name = NULL; 243 (void)asprintf(su_principal_name, "%s/%s@%s", principal_name, superuser, p); 244 free(principal_name); 245 } else 246 *su_principal_name = principal_name; 247 248 if (*su_principal_name == NULL) 249 return (errno); 250 rv = krb5_parse_name(context, *su_principal_name, &default_principal); 251 if (rv != 0) { 252 PAM_LOG("krb5_parse_name `%s': %s", *su_principal_name, 253 krb5_get_err_text(context, rv)); 254 free(*su_principal_name); 255 return (rv); 256 } 257 PAM_LOG("Target principal name: %s", *su_principal_name); 258 *su_principal = default_principal; 259 return (0); 260 } 261 262 PAM_MODULE_ENTRY("pam_ksu"); 263
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