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/*
* Copyright (C) Simo Sorce <ssorce@redhat.com> 2009
*
* 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; version 2 or later
*
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#define _BSD_SOURCE
#include <isc/util.h>
#include <string.h>
#include <stdlib.h>
#include <krb5.h>
#include "util.h"
#include "str.h"
#include "log.h"
#define DEFAULT_KEYTAB "FILE:/etc/named.keytab"
#define MIN_TIME 300 /* 5 minutes */
#define CHECK_KRB5(ctx, err, msg, ...) \
do { \
if (err) { \
log_error(msg " (%s)", ##__VA_ARGS__, \
krb5_get_error_message(ctx, err)); \
result = ISC_R_FAILURE; \
goto cleanup; \
} \
} while(0)
static isc_result_t
check_credentials(krb5_context context,
krb5_ccache ccache,
krb5_principal service)
{
char *realm = NULL;
krb5_creds creds;
krb5_creds mcreds;
krb5_timestamp now;
krb5_error_code krberr;
isc_result_t result;
memset(&mcreds, 0, sizeof(mcreds));
memset(&creds, 0, sizeof(creds));
krberr = krb5_get_default_realm(context, &realm);
CHECK_KRB5(context, krberr, "Failed to retrieve default realm");
krberr = krb5_build_principal(context, &mcreds.server,
strlen(realm), realm,
"krbtgt", realm, NULL);
CHECK_KRB5(context, krberr, "Failed to build tgt principal");
/* krb5_cc_retrieve_cred filters on both server and client */
mcreds.client = service;
krberr = krb5_cc_retrieve_cred(context, ccache, 0, &mcreds, &creds);
if (krberr) {
log_debug(2, "Principal not found in cred cache (%s)",
krb5_get_error_message(context, krberr));
result = ISC_R_FAILURE;
goto cleanup;
}
krberr = krb5_timeofday(context, &now);
CHECK_KRB5(context, krberr, "Failed to get timeofday");
if (now > (creds.times.endtime + MIN_TIME)) {
log_debug(2, "Credentials expired");
result = ISC_R_FAILURE;
goto cleanup;
}
result = ISC_R_SUCCESS;
cleanup:
krb5_free_cred_contents(context, &creds);
if (mcreds.server) krb5_free_principal(context, mcreds.server);
if (realm) krb5_free_default_realm(context, realm);
return result;
}
isc_result_t
get_krb5_tgt(isc_mem_t *mctx, const char *principal, const char *keyfile)
{
ld_string_t *ccname = NULL;
krb5_context context = NULL;
krb5_keytab keytab = NULL;
krb5_ccache ccache = NULL;
krb5_principal kprincpw;
krb5_creds my_creds;
krb5_get_init_creds_opt options;
krb5_error_code krberr;
isc_result_t result;
int ret;
REQUIRE(principal != NULL && principal[0] != '\0');
if (keyfile == NULL || keyfile[0] == '\0') {
log_debug(2, "Using default keytab file name: %s",
DEFAULT_KEYTAB);
keyfile = DEFAULT_KEYTAB;
} else {
if (strcmp(keyfile, "FILE:") != 0) {
log_error("Unknown keytab file name format, "
"missing leading 'FILE:' prefix");
return ISC_R_FAILURE;
}
}
krberr = krb5_init_context(&context);
if (krberr) {
log_error("Failed to init kerberos context");
return ISC_R_FAILURE;
}
/* get credentials cache */
CHECK(str_new(mctx, &ccname));
CHECK(str_sprintf(ccname, "MEMORY:_ld_krb5_cc_%s", principal));
ret = setenv("KRB5CCNAME", str_buf(ccname), 1);
if (ret == -1) {
log_error("Failed to set KRB5CCNAME environment variable");
result = ISC_R_FAILURE;
goto cleanup;
}
krberr = krb5_cc_resolve(context, str_buf(ccname), &ccache);
CHECK_KRB5(context, krberr,
"Failed to resolve ccache name %s", str_buf(ccname));
/* get krb5_principal from string */
krberr = krb5_parse_name(context, principal, &kprincpw);
CHECK_KRB5(context, krberr,
"Failed to parse the principal name %s", principal);
/* check if we already have valid credentials */
result = check_credentials(context, ccache, kprincpw);
if (result == ISC_R_SUCCESS) {
log_debug(2, "Found valid cached credentials");
goto cleanup;
}
/* open keytab */
krberr = krb5_kt_resolve(context, keyfile, &keytab);
CHECK_KRB5(context, krberr,
"Failed to resolve keytab file %s", keyfile);
memset(&my_creds, 0, sizeof(my_creds));
memset(&options, 0, sizeof(options));
krb5_get_init_creds_opt_set_address_list(&options, NULL);
krb5_get_init_creds_opt_set_forwardable(&options, 0);
krb5_get_init_creds_opt_set_proxiable(&options, 0);
/* get tgt */
krberr = krb5_get_init_creds_keytab(context, &my_creds, kprincpw,
keytab, 0, NULL, &options);
CHECK_KRB5(context, krberr, "Failed to init credentials");
/* store credentials in cache */
krberr = krb5_cc_initialize(context, ccache, kprincpw);
CHECK_KRB5(context, krberr, "Failed to initialize ccache");
krberr = krb5_cc_store_cred(context, ccache, &my_creds);
CHECK_KRB5(context, krberr, "Failed to store ccache");
result = ISC_R_SUCCESS;
cleanup:
if (ccname) str_destroy(&ccname);
if (keytab) krb5_kt_close(context, keytab);
if (context) krb5_free_context(context);
return result;
}
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