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/*
* GSSAPI Security Extensions
* Krb5 helpers
* Copyright (C) Simo Sorce 2010.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include "includes.h"
#include "smb_krb5.h"
#include "secrets.h"
#include "librpc/rpc/dcerpc_krb5.h"
#ifdef HAVE_KRB5
static krb5_error_code flush_keytab(krb5_context krbctx, krb5_keytab keytab)
{
krb5_error_code ret;
krb5_kt_cursor kt_cursor;
krb5_keytab_entry kt_entry;
ZERO_STRUCT(kt_entry);
ret = krb5_kt_start_seq_get(krbctx, keytab, &kt_cursor);
if (ret == KRB5_KT_END || ret == ENOENT ) {
/* no entries */
return 0;
}
ret = krb5_kt_next_entry(krbctx, keytab, &kt_entry, &kt_cursor);
while (ret == 0) {
/* we need to close and reopen enumeration because we modify
* the keytab */
ret = krb5_kt_end_seq_get(krbctx, keytab, &kt_cursor);
if (ret) {
DEBUG(1, (__location__ ": krb5_kt_end_seq_get() "
"failed (%s)\n", error_message(ret)));
goto out;
}
/* remove the entry */
ret = krb5_kt_remove_entry(krbctx, keytab, &kt_entry);
if (ret) {
DEBUG(1, (__location__ ": krb5_kt_remove_entry() "
"failed (%s)\n", error_message(ret)));
goto out;
}
ret = smb_krb5_kt_free_entry(krbctx, &kt_entry);
ZERO_STRUCT(kt_entry);
/* now reopen */
ret = krb5_kt_start_seq_get(krbctx, keytab, &kt_cursor);
if (ret) {
DEBUG(1, (__location__ ": krb5_kt_start_seq() failed "
"(%s)\n", error_message(ret)));
goto out;
}
ret = krb5_kt_next_entry(krbctx, keytab,
&kt_entry, &kt_cursor);
}
if (ret != KRB5_KT_END && ret != ENOENT) {
DEBUG(1, (__location__ ": flushing keytab we got [%s]!\n",
error_message(ret)));
}
ret = 0;
out:
return ret;
}
static krb5_error_code get_host_principal(krb5_context krbctx,
krb5_principal *host_princ)
{
krb5_error_code ret;
char *host_princ_s = NULL;
int err;
err = asprintf(&host_princ_s, "%s$@%s", global_myname(), lp_realm());
if (err == -1) {
return -1;
}
strlower_m(host_princ_s);
ret = smb_krb5_parse_name(krbctx, host_princ_s, host_princ);
if (ret) {
DEBUG(1, (__location__ ": smb_krb5_parse_name(%s) "
"failed (%s)\n",
host_princ_s, error_message(ret)));
}
SAFE_FREE(host_princ_s);
return ret;
}
static krb5_error_code fill_keytab_from_password(krb5_context krbctx,
krb5_keytab keytab,
krb5_principal princ,
krb5_kvno vno,
krb5_data *password)
{
krb5_error_code ret;
krb5_enctype *enctypes;
krb5_keytab_entry kt_entry;
unsigned int i;
ret = get_kerberos_allowed_etypes(krbctx, &enctypes);
if (ret) {
DEBUG(1, (__location__
": Can't determine permitted enctypes!\n"));
return ret;
}
for (i = 0; enctypes[i]; i++) {
krb5_keyblock *key = NULL;
key = KRB5_KT_KEY(&kt_entry);
if (create_kerberos_key_from_string(krbctx, princ,
password, key,
enctypes[i], false)) {
DEBUG(10, ("Failed to create key for enctype %d "
"(error: %s)\n",
enctypes[i], error_message(ret)));
continue;
}
kt_entry.principal = princ;
kt_entry.vno = vno;
ret = krb5_kt_add_entry(krbctx, keytab, &kt_entry);
if (ret) {
DEBUG(1, (__location__ ": Failed to add entry to "
"keytab for enctype %d (error: %s)\n",
enctypes[i], error_message(ret)));
krb5_free_keyblock(krbctx, key);
goto out;
}
krb5_free_keyblock(krbctx, key);
}
ret = 0;
out:
SAFE_FREE(enctypes);
return ret;
}
#define SRV_MEM_KEYTAB_NAME "MEMORY:cifs_srv_keytab"
#define CLEARTEXT_PRIV_ENCTYPE -99
static krb5_error_code get_mem_keytab_from_secrets(krb5_context krbctx,
krb5_keytab *keytab)
{
krb5_error_code ret;
char *pwd = NULL;
size_t pwd_len;
krb5_kt_cursor kt_cursor = NULL;
krb5_keytab_entry kt_entry;
krb5_data password;
krb5_principal princ = NULL;
krb5_kvno kvno = 0; /* FIXME: fetch current vno from KDC ? */
char *pwd_old = NULL;
if (!secrets_init()) {
DEBUG(1, (__location__ ": secrets_init failed\n"));
return KRB5_CONFIG_CANTOPEN;
}
pwd = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
if (!pwd) {
DEBUG(2, (__location__ ": failed to fetch machine password\n"));
return KRB5_LIBOS_CANTREADPWD;
}
pwd_len = strlen(pwd);
if (*keytab == NULL) {
/* create memory keytab */
ret = krb5_kt_resolve(krbctx, SRV_MEM_KEYTAB_NAME, keytab);
if (ret) {
DEBUG(1, (__location__ ": Failed to get memory "
"keytab!\n"));
return ret;
}
}
ZERO_STRUCT(kt_entry);
/* check if the keytab already has any entry */
ret = krb5_kt_start_seq_get(krbctx, *keytab, &kt_cursor);
if (ret != KRB5_KT_END && ret != ENOENT ) {
/* check if we have our special enctype used to hold
* the clear text password. If so, check it out so that
* we can verify if the keytab needs to be upgraded */
while ((ret = krb5_kt_next_entry(krbctx, *keytab,
&kt_entry, &kt_cursor)) == 0) {
if (smb_get_enctype_from_kt_entry(&kt_entry) == CLEARTEXT_PRIV_ENCTYPE) {
break;
}
smb_krb5_kt_free_entry(krbctx, &kt_entry);
ZERO_STRUCT(kt_entry);
}
if (ret != 0 && ret != KRB5_KT_END && ret != ENOENT ) {
/* Error parsing keytab */
DEBUG(1, (__location__ ": Failed to parse memory "
"keytab!\n"));
goto out;
}
if (ret == 0) {
/* found private entry,
* check if keytab is up to date */
if ((pwd_len == kt_entry.key.length) &&
(memcmp(kt_entry.key.contents,
pwd, pwd_len) == 0)) {
/* keytab is already up to date, return */
smb_krb5_kt_free_entry(krbctx, &kt_entry);
goto out;
}
smb_krb5_kt_free_entry(krbctx, &kt_entry);
ZERO_STRUCT(kt_entry);
/* flush keytab, we need to regen it */
ret = flush_keytab(krbctx, *keytab);
if (ret) {
DEBUG(1, (__location__ ": Failed to flush "
"memory keytab!\n"));
goto out;
}
}
}
if (kt_cursor) {
/* stop enumeration and free cursor */
krb5_kt_end_seq_get(krbctx, *keytab, &kt_cursor);
kt_cursor = NULL;
}
/* keytab is not up to date, fill it up */
ret = get_host_principal(krbctx, &princ);
if (ret) {
DEBUG(1, (__location__ ": Failed to get host principal!\n"));
goto out;
}
password.data = pwd;
password.length = pwd_len;
ret = fill_keytab_from_password(krbctx, *keytab,
princ, kvno, &password);
if (ret) {
DEBUG(1, (__location__ ": Failed to fill memory keytab!\n"));
goto out;
}
pwd_old = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
if (!pwd_old) {
DEBUG(10, (__location__ ": no prev machine password\n"));
} else {
password.data = pwd_old;
password.length = strlen(pwd_old);
ret = fill_keytab_from_password(krbctx, *keytab,
princ, kvno -1, &password);
if (ret) {
DEBUG(1, (__location__
": Failed to fill memory keytab!\n"));
goto out;
}
}
/* add our private enctype + cleartext password so that we can
* update the keytab if secrets change later on */
ZERO_STRUCT(kt_entry);
kt_entry.principal = princ;
kt_entry.vno = 0;
kt_entry.key.enctype = CLEARTEXT_PRIV_ENCTYPE;
kt_entry.key.length = pwd_len;
kt_entry.key.contents = (uint8_t *)pwd;
ret = krb5_kt_add_entry(krbctx, *keytab, &kt_entry);
if (ret) {
DEBUG(1, (__location__ ": Failed to add entry to "
"keytab for private enctype (%d) (error: %s)\n",
CLEARTEXT_PRIV_ENCTYPE, error_message(ret)));
goto out;
}
ret = 0;
out:
SAFE_FREE(pwd);
SAFE_FREE(pwd_old);
if (kt_cursor) {
/* stop enumeration and free cursor */
krb5_kt_end_seq_get(krbctx, *keytab, &kt_cursor);
kt_cursor = NULL;
}
if (princ) {
krb5_free_principal(krbctx, princ);
}
if (ret) {
if (*keytab) {
krb5_kt_close(krbctx, *keytab);
*keytab = NULL;
}
}
return ret;
}
static krb5_error_code get_mem_keytab_from_system_keytab(krb5_context krbctx,
krb5_keytab *keytab,
bool verify)
{
return KRB5_KT_NOTFOUND;
}
krb5_error_code smb_krb5_get_server_keytab(krb5_context krbctx,
krb5_keytab *keytab)
{
krb5_error_code ret;
*keytab = NULL;
switch (lp_kerberos_method()) {
default:
case KERBEROS_VERIFY_SECRETS:
ret = get_mem_keytab_from_secrets(krbctx, keytab);
break;
case KERBEROS_VERIFY_SYSTEM_KEYTAB:
ret = get_mem_keytab_from_system_keytab(krbctx, keytab, true);
break;
case KERBEROS_VERIFY_DEDICATED_KEYTAB:
/* just use whatever keytab is configured */
ret = get_mem_keytab_from_system_keytab(krbctx, keytab, false);
break;
case KERBEROS_VERIFY_SECRETS_AND_KEYTAB:
ret = get_mem_keytab_from_secrets(krbctx, keytab);
if (ret) {
DEBUG(3, (__location__ ": Warning! Unable to set mem "
"keytab from secrets!\n"));
}
/* Now append system keytab keys too */
ret = get_mem_keytab_from_system_keytab(krbctx, keytab, true);
if (ret) {
DEBUG(3, (__location__ ": Warning! Unable to set mem "
"keytab from secrets!\n"));
}
break;
}
return ret;
}
#endif /* HAVE_KRB5 */
|