NetBSD-5.0.2/lib/libpam/modules/pam_ksu/pam_ksu.c
/* $NetBSD: pam_ksu.c,v 1.2 2004/12/12 08:18:46 christos Exp $ */
/*-
* Copyright (c) 2002 Jacques A. Vidrine <nectar@FreeBSD.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#ifdef __FreeBSD__
__FBSDID("$FreeBSD: src/lib/libpam/modules/pam_ksu/pam_ksu.c,v 1.5 2004/02/10 10:13:21 des Exp $");
#else
__RCSID("$NetBSD: pam_ksu.c,v 1.2 2004/12/12 08:18:46 christos Exp $");
#endif
#include <sys/param.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <krb5/krb5.h>
#define PAM_SM_AUTH
#define PAM_SM_CRED
#include <security/pam_appl.h>
#include <security/pam_modules.h>
#include <security/pam_mod_misc.h>
static const char superuser[] = "root";
static long get_su_principal(krb5_context, const char *, const char *,
char **, krb5_principal *);
static int auth_krb5(pam_handle_t *, krb5_context, const char *,
krb5_principal);
PAM_EXTERN int
pam_sm_authenticate(pam_handle_t *pamh, int flags __unused,
int argc __unused, const char *argv[] __unused)
{
krb5_context context;
krb5_principal su_principal;
const char *user;
const void *ruser;
char *su_principal_name;
long rv;
int pamret;
pamret = pam_get_user(pamh, &user, NULL);
if (pamret != PAM_SUCCESS)
return (pamret);
PAM_LOG("Got user: %s", user);
pamret = pam_get_item(pamh, PAM_RUSER, &ruser);
if (pamret != PAM_SUCCESS)
return (pamret);
PAM_LOG("Got ruser: %s", (const char *)ruser);
rv = krb5_init_context(&context);
if (rv != 0) {
PAM_LOG("krb5_init_context failed: %s",
krb5_get_err_text(context, rv));
return (PAM_SERVICE_ERR);
}
rv = get_su_principal(context, user, ruser, &su_principal_name, &su_principal);
if (rv != 0)
return (PAM_AUTH_ERR);
PAM_LOG("kuserok: %s -> %s", su_principal_name, user);
rv = krb5_kuserok(context, su_principal, user);
pamret = rv ? auth_krb5(pamh, context, su_principal_name, su_principal) : PAM_AUTH_ERR;
free(su_principal_name);
krb5_free_principal(context, su_principal);
krb5_free_context(context);
return (pamret);
}
PAM_EXTERN int
pam_sm_setcred(pam_handle_t *pamh __unused, int flags __unused,
int ac __unused, const char *av[] __unused)
{
return (PAM_SUCCESS);
}
/* Authenticate using Kerberos 5.
* pamh -- The PAM handle.
* context -- An initialized krb5_context.
* su_principal_name -- The target principal name, used only for password prompts.
* If NULL, the password prompts will not include a principal
* name.
* su_principal -- The target krb5_principal.
* Note that a valid keytab in the default location with a host entry
* must be available, and that the PAM application must have sufficient
* privileges to access it.
* Returns PAM_SUCCESS if authentication was successful, or an appropriate
* PAM error code if it was not.
*/
static int
auth_krb5(pam_handle_t *pamh, krb5_context context, const char *su_principal_name,
krb5_principal su_principal)
{
krb5_creds creds;
krb5_get_init_creds_opt gic_opt;
krb5_verify_init_creds_opt vic_opt;
const char *pass;
char *prompt;
long rv;
int pamret;
prompt = NULL;
krb5_get_init_creds_opt_init(&gic_opt);
krb5_verify_init_creds_opt_init(&vic_opt);
if (su_principal_name != NULL)
(void)asprintf(&prompt, "Password for %s:", su_principal_name);
else
(void)asprintf(&prompt, "Password:");
if (prompt == NULL)
return (PAM_BUF_ERR);
pass = NULL;
pamret = pam_get_authtok(pamh, PAM_AUTHTOK, &pass, prompt);
free(prompt);
if (pamret != PAM_SUCCESS)
return (pamret);
rv = krb5_get_init_creds_password(context, &creds, su_principal,
pass, NULL, NULL, 0, NULL, &gic_opt);
if (rv != 0) {
PAM_LOG("krb5_get_init_creds_password: %s",
krb5_get_err_text(context, rv));
return (PAM_AUTH_ERR);
}
krb5_verify_init_creds_opt_set_ap_req_nofail(&vic_opt, 1);
rv = krb5_verify_init_creds(context, &creds, NULL, NULL, NULL,
&vic_opt);
krb5_free_cred_contents(context, &creds);
if (rv != 0) {
PAM_LOG("krb5_verify_init_creds: %s",
krb5_get_err_text(context, rv));
return (PAM_AUTH_ERR);
}
return (PAM_SUCCESS);
}
/* Determine the target principal given the current user and the target user.
* context -- An initialized krb5_context.
* target_user -- The target username.
* current_user -- The current username.
* su_principal_name -- (out) The target principal name.
* su_principal -- (out) The target krb5_principal.
* When the target user is `root', the target principal will be a `root
* instance', e.g. `luser/root@REA.LM'. Otherwise, the target principal
* will simply be the current user's default principal name. Note that
* in any case, if KRB5CCNAME is set and a credentials cache exists, the
* principal name found there will be the `starting point', rather than
* the ruser parameter.
*
* Returns 0 for success, or a com_err error code on failure.
*/
static long
get_su_principal(krb5_context context, const char *target_user, const char *current_user,
char **su_principal_name, krb5_principal *su_principal)
{
krb5_principal default_principal;
krb5_ccache ccache;
char *principal_name, *ccname, *p;
long rv;
uid_t euid, ruid;
*su_principal = NULL;
default_principal = NULL;
/* Unless KRB5CCNAME was explicitly set, we won't really be able
* to look at the credentials cache since krb5_cc_default will
* look at getuid().
*/
ruid = getuid();
euid = geteuid();
rv = seteuid(ruid);
if (rv != 0)
return (errno);
p = getenv("KRB5CCNAME");
if (p != NULL)
ccname = strdup(p);
else
(void)asprintf(&ccname, "%s%lu", KRB5_DEFAULT_CCROOT, (unsigned long)ruid);
if (ccname == NULL)
return (errno);
rv = krb5_cc_resolve(context, ccname, &ccache);
free(ccname);
if (rv == 0) {
rv = krb5_cc_get_principal(context, ccache, &default_principal);
krb5_cc_close(context, ccache);
if (rv != 0)
default_principal = NULL; /* just to be safe */
}
rv = seteuid(euid);
if (rv != 0)
return (errno);
if (default_principal == NULL) {
rv = krb5_make_principal(context, &default_principal, NULL, current_user, NULL);
if (rv != 0) {
PAM_LOG("Could not determine default principal name.");
return (rv);
}
}
/* Now that we have some principal, if the target account is
* `root', then transform it into a `root' instance, e.g.
* `user@REA.LM' -> `user/root@REA.LM'.
*/
rv = krb5_unparse_name(context, default_principal, &principal_name);
krb5_free_principal(context, default_principal);
if (rv != 0) {
PAM_LOG("krb5_unparse_name: %s",
krb5_get_err_text(context, rv));
return (rv);
}
PAM_LOG("Default principal name: %s", principal_name);
if (strcmp(target_user, superuser) == 0) {
p = strrchr(principal_name, '@');
if (p == NULL) {
PAM_LOG("malformed principal name `%s'", principal_name);
free(principal_name);
return (rv);
}
*p++ = '\0';
*su_principal_name = NULL;
(void)asprintf(su_principal_name, "%s/%s@%s", principal_name, superuser, p);
free(principal_name);
} else
*su_principal_name = principal_name;
if (*su_principal_name == NULL)
return (errno);
rv = krb5_parse_name(context, *su_principal_name, &default_principal);
if (rv != 0) {
PAM_LOG("krb5_parse_name `%s': %s", *su_principal_name,
krb5_get_err_text(context, rv));
free(*su_principal_name);
return (rv);
}
PAM_LOG("Target principal name: %s", *su_principal_name);
*su_principal = default_principal;
return (0);
}
PAM_MODULE_ENTRY("pam_ksu");