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/* ldap_krb_helper.c
Helper routings for allowing LDAP to read configuration with GSSAPI/krb auth */
/*
* Copyright (c) 2015-2017 by Internet Systems Consortium, Inc. ("ISC")
* Copyright (c) 2014 William B.
* 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.
* 3. Neither the name of The Internet Software Consortium nor the names
* of its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM 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 INTERNET SOFTWARE CONSORTIUM 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.
*
* This helper was written by William Brown <william@adelaide.edu.au>,
* inspired by krb5_helper.c from bind-dyndb-ldap by Simo Sorce (Redhat)
*/
#if defined(LDAP_USE_GSSAPI)
#include "dhcpd.h"
#include "ldap_krb_helper.h"
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <time.h>
#define KRB_DEFAULT_KEYTAB "FILE:/etc/dhcp/dhcp.keytab"
#define KRB_MIN_TIME 300
#define CHECK_KRB5(ctx, err, msg, ...) \
do { \
if (err) { \
const char * errmsg = krb5_get_error_message(ctx, err); \
log_error("Err: %s -> %s\n", msg, errmsg); \
result = ISC_R_FAILURE; \
goto cleanup; \
} \
} while (0)
#define CHECK(ret_code, msg) \
if (ret_code != 0) { \
log_error("Error, %i %s\n", ret_code, msg); \
goto cleanup; \
}
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_error_code krberr;
krb5_timestamp now;
isc_result_t result = ISC_R_FAILURE;
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 'krbtgt/REALM' principal");
mcreds.client = service;
krberr = krb5_cc_retrieve_cred(context, ccache, 0, &mcreds, &creds);
if (krberr) {
const char * errmsg = krb5_get_error_message(context, krberr);
log_error("Credentials are not present in cache (%s)\n", errmsg);
krb5_free_error_message(context, errmsg);
result = ISC_R_FAILURE;
goto cleanup;
}
CHECK_KRB5(context, krberr, "Credentials are not present in cache ");
krberr = krb5_timeofday(context, &now);
CHECK_KRB5(context, krberr, "Failed to get time of day");
if (now > (creds.times.endtime + KRB_MIN_TIME)) {
log_error("Credentials cache expired");
result = ISC_R_FAILURE;
goto cleanup;
} else {
char buf[255];
char fill = ' ';
krb5_timestamp_to_sfstring(creds.times.endtime, buf, 16, &fill);
log_info("Credentials valid til %s\n", buf);
}
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
krb5_get_tgt(const char *principal, const char *keyfile)
{
isc_result_t result = ISC_R_FAILURE;
char *ccname = NULL;
krb5_context context = NULL;
krb5_error_code krberr;
krb5_ccache ccache = NULL;
krb5_principal kprincpw = NULL;
krb5_creds my_creds;
krb5_creds * my_creds_ptr = NULL;
krb5_get_init_creds_opt options;
krb5_keytab keytab = NULL;
int ret;
if (keyfile == NULL || keyfile[0] == '\0') {
keyfile = KRB_DEFAULT_KEYTAB;
log_info("Using default keytab %s\n", keyfile);
} else {
if (strncmp(keyfile, "FILE:", 5) != 0) {
log_error("Unknown keytab path format: Does it start with FILE:?\n");
return ISC_R_FAILURE;
}
}
krberr = krb5_init_context(&context);
CHECK_KRB5(NULL, krberr, "Kerberos context initialization failed");
result = ISC_R_SUCCESS;
ccname = "MEMORY:dhcp_ld_krb5_cc";
log_info("Using ccache %s\n" , ccname);
ret = setenv("KRB5CCNAME", ccname, 1);
if (ret == -1) {
log_error("Failed to setup environment\n");
result = ISC_R_FAILURE;
goto cleanup;
}
krberr = krb5_cc_resolve(context, ccname, &ccache);
CHECK_KRB5(context, krberr, "Couldnt resolve ccache '%s'", ccname);
krberr = krb5_parse_name(context, principal, &kprincpw);
CHECK_KRB5(context, krberr, "Failed to parse princ '%s'", princpal);
result = check_credentials(context, ccache, kprincpw);
if (result == ISC_R_SUCCESS) {
log_info("Found valid kerberos credentials\n");
goto cleanup;
} else {
log_error("No valid krb5 credentials\n");
}
krberr = krb5_kt_resolve(context, keyfile, &keytab);
CHECK_KRB5(context, krberr,
"Failed to resolve kt files '%s'\n", keyfile);
memset(&my_creds, 0, sizeof(my_creds));
memset(&options, 0, sizeof(options));
krb5_get_init_creds_opt_set_tkt_life(&options, KRB_MIN_TIME * 2);
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);
krberr = krb5_get_init_creds_keytab(context, &my_creds, kprincpw,
keytab, 0, NULL, &options);
CHECK_KRB5(context, krberr, "Failed to get initial credentials TGT\n");
my_creds_ptr = &my_creds;
krberr = krb5_cc_initialize(context, ccache, kprincpw);
CHECK_KRB5(context, krberr, "Failed to init ccache\n");
krberr = krb5_cc_store_cred(context, ccache, &my_creds);
CHECK_KRB5(context, krberr, "Failed to store credentials\n");
result = ISC_R_SUCCESS;
log_info("Successfully init krb tgt %s", principal);
cleanup:
if (ccache) krb5_cc_close(context, ccache);
if (keytab) krb5_kt_close(context, keytab);
if (kprincpw) krb5_free_principal(context, kprincpw);
if (my_creds_ptr) krb5_free_cred_contents(context, &my_creds);
if (context) krb5_free_context(context);
return result;
}
#endif /* defined(LDAP_USE_GSSAPI) */
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