r4348: syncing up for 3.0.11pre1

[Samba.git] / source / libads / kerberos.c

/* 
   Unix SMB/CIFS implementation.
   kerberos utility library
   Copyright (C) Andrew Tridgell 2001
   Copyright (C) Remus Koos 2001
   Copyright (C) Nalin Dahyabhai 2004.
   Copyright (C) Jeremy Allison 2004.

   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 2 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, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"

#ifdef HAVE_KRB5

#define LIBADS_CCACHE_NAME "MEMORY:libads"

/*
  we use a prompter to avoid a crash bug in the kerberos libs when 
  dealing with empty passwords
  this prompter is just a string copy ...
*/
static krb5_error_code 
kerb_prompter(krb5_context ctx, void *data,
               const char *name,
               const char *banner,
               int num_prompts,
               krb5_prompt prompts[])
{
        if (num_prompts == 0) return 0;

        memset(prompts[0].reply->data, '\0', prompts[0].reply->length);
        if (prompts[0].reply->length > 0) {
                if (data) {
                        strncpy(prompts[0].reply->data, data, prompts[0].reply->length-1);
                        prompts[0].reply->length = strlen(prompts[0].reply->data);
                } else {
                        prompts[0].reply->length = 0;
                }
        }
        return 0;
}

/*
  simulate a kinit, putting the tgt in the given cache location. If cache_name == NULL
  place in default cache location.
  remus@snapserver.com
*/
int kerberos_kinit_password(const char *principal,
                                const char *password,
                                int time_offset,
                                time_t *expire_time,
                                const char *cache_name)
{
        krb5_context ctx = NULL;
        krb5_error_code code = 0;
        krb5_ccache cc = NULL;
        krb5_principal me;
        krb5_creds my_creds;

        if ((code = krb5_init_context(&ctx)))
                return code;

        if (time_offset != 0) {
                krb5_set_real_time(ctx, time(NULL) + time_offset, 0);
        }
        
        if ((code = krb5_cc_resolve(ctx, cache_name ?
                        cache_name : krb5_cc_default_name(ctx), &cc))) {
                krb5_free_context(ctx);
                return code;
        }
        
        if ((code = krb5_parse_name(ctx, principal, &me))) {
                krb5_free_context(ctx); 
                return code;
        }
        
        if ((code = krb5_get_init_creds_password(ctx, &my_creds, me, password, 
                                                 kerb_prompter, 
                                                 NULL, 0, NULL, NULL))) {
                krb5_free_principal(ctx, me);
                krb5_free_context(ctx);         
                return code;
        }
        
        if ((code = krb5_cc_initialize(ctx, cc, me))) {
                krb5_free_cred_contents(ctx, &my_creds);
                krb5_free_principal(ctx, me);
                krb5_free_context(ctx);         
                return code;
        }
        
        if ((code = krb5_cc_store_cred(ctx, cc, &my_creds))) {
                krb5_cc_close(ctx, cc);
                krb5_free_cred_contents(ctx, &my_creds);
                krb5_free_principal(ctx, me);
                krb5_free_context(ctx);         
                return code;
        }
        
        if (expire_time)
                *expire_time = (time_t) my_creds.times.endtime;

        krb5_cc_close(ctx, cc);
        krb5_free_cred_contents(ctx, &my_creds);
        krb5_free_principal(ctx, me);
        krb5_free_context(ctx);         
        
        return 0;
}



/* run kinit to setup our ccache */
int ads_kinit_password(ADS_STRUCT *ads)
{
        char *s;
        int ret;

        if (asprintf(&s, "%s@%s", ads->auth.user_name, ads->auth.realm) == -1) {
                return KRB5_CC_NOMEM;
        }

        if (!ads->auth.password) {
                return KRB5_LIBOS_CANTREADPWD;
        }
        
        ret = kerberos_kinit_password(s, ads->auth.password, ads->auth.time_offset,
                        &ads->auth.expire, NULL);

        if (ret) {
                DEBUG(0,("kerberos_kinit_password %s failed: %s\n", 
                         s, error_message(ret)));
        }
        free(s);
        return ret;
}

int ads_kdestroy(const char *cc_name)
{
        krb5_error_code code;
        krb5_context ctx = NULL;
        krb5_ccache cc = NULL;

        if ((code = krb5_init_context (&ctx))) {
                DEBUG(3, ("ads_kdestroy: kdb5_init_context failed: %s\n", 
                        error_message(code)));
                return code;
        }
  
        if (!cc_name) {
                if ((code = krb5_cc_default(ctx, &cc))) {
                        krb5_free_context(ctx);
                        return code;
                }
        } else {
                if ((code = krb5_cc_resolve(ctx, cc_name, &cc))) {
                        DEBUG(3, ("ads_kdestroy: krb5_cc_resolve failed: %s\n",
                                  error_message(code)));
                        krb5_free_context(ctx);
                        return code;
                }
        }

        if ((code = krb5_cc_destroy (ctx, cc))) {
                DEBUG(3, ("ads_kdestroy: krb5_cc_destroy failed: %s\n", 
                        error_message(code)));
        }

        krb5_free_context (ctx);
        return code;
}

/************************************************************************
 Routine to fetch the salting principal for a service.  Active
 Directory may use a non-obvious principal name to generate the salt
 when it determines the key to use for encrypting tickets for a service,
 and hopefully we detected that when we joined the domain.
 ************************************************************************/

static char *kerberos_secrets_fetch_salting_principal(const char *service, int enctype)
{
        char *key = NULL;
        char *ret = NULL;

        asprintf(&key, "%s/%s/enctype=%d", SECRETS_SALTING_PRINCIPAL, service, enctype);
        if (!key) {
                return NULL;
        }
        ret = (char *)secrets_fetch(key, NULL);
        SAFE_FREE(key);
        return ret;
}

/************************************************************************
 Routine to get the salting principal for this service.  Active
 Directory may use a non-obvious principal name to generate the salt
 when it determines the key to use for encrypting tickets for a service,
 and hopefully we detected that when we joined the domain.
 Caller must free if return is not null.
 ************************************************************************/

krb5_principal kerberos_fetch_salt_princ_for_host_princ(krb5_context context,
                                                        krb5_principal host_princ,
                                                        int enctype)
{
        char *unparsed_name = NULL, *salt_princ_s = NULL;
        krb5_principal ret_princ = NULL;

        if (krb5_unparse_name(context, host_princ, &unparsed_name) != 0) {
                return (krb5_principal)NULL;
        }

        if ((salt_princ_s = kerberos_secrets_fetch_salting_principal(unparsed_name, enctype)) == NULL) {
                krb5_free_unparsed_name(context, unparsed_name);
                return (krb5_principal)NULL;
        }

        if (krb5_parse_name(context, salt_princ_s, &ret_princ) != 0) {
                krb5_free_unparsed_name(context, unparsed_name);
                SAFE_FREE(salt_princ_s);
                return (krb5_principal)NULL;
        }
        krb5_free_unparsed_name(context, unparsed_name);
        SAFE_FREE(salt_princ_s);
        return ret_princ;
}

/************************************************************************
 Routine to set the salting principal for this service.  Active
 Directory may use a non-obvious principal name to generate the salt
 when it determines the key to use for encrypting tickets for a service,
 and hopefully we detected that when we joined the domain.
 Setting principal to NULL deletes this entry.
 ************************************************************************/

 BOOL kerberos_secrets_store_salting_principal(const char *service,
                                              int enctype,
                                              const char *principal)
{
        char *key = NULL;
        BOOL ret = False;
        krb5_context context = NULL;
        krb5_principal princ = NULL;
        char *princ_s = NULL;
        char *unparsed_name = NULL;

        krb5_init_context(&context);
        if (!context) {
                return False;
        }
        if (strchr_m(service, '@')) {
                asprintf(&princ_s, "%s", service);
        } else {
                asprintf(&princ_s, "%s@%s", service, lp_realm());
        }

        if (krb5_parse_name(context, princ_s, &princ) != 0) {
                goto out;
                
        }
        if (krb5_unparse_name(context, princ, &unparsed_name) != 0) {
                goto out;
        }

        asprintf(&key, "%s/%s/enctype=%d", SECRETS_SALTING_PRINCIPAL, unparsed_name, enctype);
        if (!key)  {
                goto out;
        }

        if ((principal != NULL) && (strlen(principal) > 0)) {
                ret = secrets_store(key, principal, strlen(principal) + 1);
        } else {
                ret = secrets_delete(key);
        }

 out:

        SAFE_FREE(key);
        SAFE_FREE(princ_s);

        if (unparsed_name) {
                krb5_free_unparsed_name(context, unparsed_name);
        }
        if (context) {
                krb5_free_context(context);
        }

        return ret;
}

/************************************************************************
 Routine to get initial credentials as a service ticket for the local machine.
 Returns a buffer initialized with krb5_mk_req_extended.
 ************************************************************************/

static krb5_error_code get_service_ticket(krb5_context ctx,
                                        krb5_ccache ccache,
                                        const char *service_principal,
                                        int enctype,
                                        krb5_data *p_outbuf)
{
        krb5_creds creds, *new_creds = NULL;
        char *service_s = NULL;
        char *machine_account = NULL, *password = NULL;
        krb5_data in_data;
        krb5_auth_context auth_context = NULL;
        krb5_error_code err = 0;

        ZERO_STRUCT(creds);

        asprintf(&machine_account, "%s$@%s", global_myname(), lp_realm());
        if (machine_account == NULL) {
                goto out;
        }
        password = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
        if (password == NULL) {
                goto out;
        }
        if ((err = kerberos_kinit_password(machine_account, password, 0, NULL, LIBADS_CCACHE_NAME)) != 0) {
                DEBUG(0,("get_service_ticket: kerberos_kinit_password %s@%s failed: %s\n", 
                        machine_account,
                        lp_realm(),
                        error_message(err)));
                goto out;
        }

        /* Ok - the above call has gotten a TGT. Now we need to get a service
           ticket to ourselves. */

        /* Set up the enctype and client and server principal fields for krb5_get_credentials. */
        kerberos_set_creds_enctype(&creds, enctype);

        if ((err = krb5_cc_get_principal(ctx, ccache, &creds.client))) {
                DEBUG(3, ("get_service_ticket: krb5_cc_get_principal failed: %s\n", 
                        error_message(err)));
                goto out;
        }

        if (strchr_m(service_principal, '@')) {
                asprintf(&service_s, "%s", service_principal);
        } else {
                asprintf(&service_s, "%s@%s", service_principal, lp_realm());
        }

        if ((err = krb5_parse_name(ctx, service_s, &creds.server))) {
                DEBUG(0,("get_service_ticket: krb5_parse_name %s failed: %s\n", 
                        service_s, error_message(err)));
                goto out;
        }

        if ((err = krb5_get_credentials(ctx, 0, ccache, &creds, &new_creds))) {
                DEBUG(5,("get_service_ticket: krb5_get_credentials for %s enctype %d failed: %s\n", 
                        service_s, enctype, error_message(err)));
                goto out;
        }

        memset(&in_data, '\0', sizeof(in_data));
        if ((err = krb5_mk_req_extended(ctx, &auth_context, 0, &in_data,
                        new_creds, p_outbuf)) != 0) {
                DEBUG(0,("get_service_ticket: krb5_mk_req_extended failed: %s\n", 
                        error_message(err)));
                goto out;
        }

 out:

        if (auth_context) {
                krb5_auth_con_free(ctx, auth_context);
        }
        if (new_creds) {
                krb5_free_creds(ctx, new_creds);
        }
        if (creds.server) {
                krb5_free_principal(ctx, creds.server);
        }
        if (creds.client) {
                krb5_free_principal(ctx, creds.client);
        }

        SAFE_FREE(service_s);
        SAFE_FREE(password);
        SAFE_FREE(machine_account);
        return err;
}

/************************************************************************
 Check if the machine password can be used in conjunction with the salting_principal
 to generate a key which will successfully decrypt the AP_REQ already
 gotten as a message to the local machine.
 ************************************************************************/

static BOOL verify_service_password(krb5_context ctx,
                                    int enctype,
                                    const char *salting_principal,
                                    krb5_data *in_data)
{
        BOOL ret = False;
        krb5_principal salting_kprinc = NULL;
        krb5_ticket *ticket = NULL;
        krb5_keyblock key;
        krb5_data passdata;
        char *salting_s = NULL;
        char *machine_account = NULL, *password = NULL;
        krb5_auth_context auth_context = NULL;
        krb5_error_code err;

        memset(&passdata, '\0', sizeof(passdata));
        memset(&key, '\0', sizeof(key));

        asprintf(&machine_account, "%s$@%s", global_myname(), lp_realm());
        if (machine_account == NULL) {
                goto out;
        }
        password = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
        if (password == NULL) {
                goto out;
        }

        if (strchr_m(salting_principal, '@')) {
                asprintf(&salting_s, "%s", salting_principal);
        } else {
                asprintf(&salting_s, "%s@%s", salting_principal, lp_realm());
        }

        if ((err = krb5_parse_name(ctx, salting_s, &salting_kprinc))) {
                DEBUG(0,("verify_service_password: krb5_parse_name %s failed: %s\n", 
                        salting_s, error_message(err)));
                goto out;
        }

        passdata.length = strlen(password);
        passdata.data = (char*)password;
        if ((err = create_kerberos_key_from_string_direct(ctx, salting_kprinc, &passdata, &key, enctype))) {
                DEBUG(0,("verify_service_password: create_kerberos_key_from_string %d failed: %s\n",
                        enctype, error_message(err)));
                goto out;
        }

        if ((err = krb5_auth_con_init(ctx, &auth_context)) != 0) {
                DEBUG(0,("verify_service_password: krb5_auth_con_init failed %s\n", error_message(err)));
                goto out;
        }

        if ((err = krb5_auth_con_setuseruserkey(ctx, auth_context, &key)) != 0) {
                DEBUG(0,("verify_service_password: krb5_auth_con_setuseruserkey failed %s\n", error_message(err)));
                goto out;
        }

        if (!(err = krb5_rd_req(ctx, &auth_context, in_data, NULL, NULL, NULL, &ticket))) {
                DEBUG(10,("verify_service_password: decrypted message with enctype %u salt %s!\n",
                                (unsigned int)enctype, salting_s));
                ret = True;
        }

 out:

        memset(&passdata, 0, sizeof(passdata));
        krb5_free_keyblock_contents(ctx, &key);
        if (ticket != NULL) {
                krb5_free_ticket(ctx, ticket);
        }
        if (salting_kprinc) {
                krb5_free_principal(ctx, salting_kprinc);
        }
        SAFE_FREE(salting_s);
        SAFE_FREE(password);
        SAFE_FREE(machine_account);
        return ret;
}

/************************************************************************
 *
 * From the current draft of kerberos-clarifications:
 *
 *     It is not possible to reliably generate a user's key given a pass
 *     phrase without contacting the KDC, since it will not be known
 *     whether alternate salt or parameter values are required.
 *
 * And because our server has a password, we have this exact problem.  We
 * make multiple guesses as to which principal name provides the salt which
 * the KDC is using.
 *
 ************************************************************************/

static void kerberos_derive_salting_principal_for_enctype(const char *service_principal,
                                                          krb5_context ctx,
                                                          krb5_ccache ccache,
                                                          krb5_enctype enctype,
                                                          krb5_enctype *enctypes)
{
        char *salting_principals[3] = {NULL, NULL, NULL}, *second_principal = NULL;
        krb5_error_code err = 0;
        krb5_data outbuf;
        int i, j;

        memset(&outbuf, '\0', sizeof(outbuf));

        /* Check that the service_principal is useful. */
        if ((service_principal == NULL) || (strlen(service_principal) == 0)) {
                return;
        }

        /* Generate our first guess -- the principal as-given. */
        asprintf(&salting_principals[0], "%s", service_principal);
        if ((salting_principals[0] == NULL) || (strlen(salting_principals[0]) == 0)) {
                return;
        }

        /* Generate our second guess -- the computer's principal, as Win2k3. */
        asprintf(&second_principal, "host/%s.%s", global_myname(), lp_realm());
        if (second_principal != NULL) {
                strlower_m(second_principal);
                asprintf(&salting_principals[1], "%s@%s", second_principal, lp_realm());
                SAFE_FREE(second_principal);
        }
        if ((salting_principals[1] == NULL) || (strlen(salting_principals[1]) == 0)) {
                goto out;
        }

        /* Generate our third guess -- the computer's principal, as Win2k. */
        asprintf(&second_principal, "HOST/%s", global_myname());
        if (second_principal != NULL) {
                strlower_m(second_principal + 5);
                asprintf(&salting_principals[2], "%s@%s",
                        second_principal, lp_realm());
                SAFE_FREE(second_principal);
        }
        if ((salting_principals[2] == NULL) || (strlen(salting_principals[2]) == 0)) {
                goto out;
        }

        /* Get a service ticket for ourselves into our memory ccache. */
        /* This will commonly fail if there is no principal by that name (and we're trying
           many names). So don't print a debug 0 error. */

        if ((err = get_service_ticket(ctx, ccache, service_principal, enctype, &outbuf)) != 0) {
                DEBUG(3, ("verify_service_password: get_service_ticket failed: %s\n", 
                        error_message(err)));
                goto out;
        }

        /* At this point we have a message to ourselves, salted only the KDC knows how. We
           have to work out what that salting is. */

        /* Try and find the correct salting principal. */
        for (i = 0; i < sizeof(salting_principals) / sizeof(salting_principals[i]); i++) {
                if (verify_service_password(ctx, enctype, salting_principals[i], &outbuf)) {
                        break;
                }
        }

        /* If we failed to get a match, return. */
        if (i >= sizeof(salting_principals) / sizeof(salting_principals[i])) {
                goto out;
        }

        /* If we succeeded, store the principal for use for all enctypes which
         * share the same cipher and string-to-key function.  Doing this here
         * allows servers which just pass a keytab to krb5_rd_req() to work
         * correctly. */
        for (j = 0; enctypes[j] != 0; j++) {
                if (enctype != enctypes[j]) {
                        /* If this enctype isn't compatible with the one which
                         * we used, skip it. */

                        if (!kerberos_compatible_enctypes(ctx, enctypes[j], enctype))
                                continue;
                }
                /* If the principal which gives us the proper salt is the one
                 * which we would normally guess, don't bother noting anything
                 * in the secrets tdb. */
                if (strcmp(service_principal, salting_principals[i]) != 0) {
                        kerberos_secrets_store_salting_principal(service_principal,
                                                                enctypes[j],
                                                                salting_principals[i]);
                }
        }

 out :

        kerberos_free_data_contents(ctx, &outbuf);
        SAFE_FREE(salting_principals[0]);
        SAFE_FREE(salting_principals[1]);
        SAFE_FREE(salting_principals[2]);
        SAFE_FREE(second_principal);
}

/************************************************************************
 Go through all the possible enctypes for this principal.
 ************************************************************************/

static void kerberos_derive_salting_principal_direct(krb5_context context,
                                        krb5_ccache ccache,
                                        krb5_enctype *enctypes,
                                        char *service_principal)
{
        int i;

        /* Try for each enctype separately, because the rules are
         * different for different enctypes. */
        for (i = 0; enctypes[i] != 0; i++) {
                /* Delete secrets entry first. */
                kerberos_secrets_store_salting_principal(service_principal, 0, NULL);
#ifdef ENCTYPE_ARCFOUR_HMAC
                if (enctypes[i] == ENCTYPE_ARCFOUR_HMAC) {
                        /* Of course this'll always work, so just save
                         * ourselves the effort. */
                        continue;
                }
#endif
                /* Try to figure out what's going on with this
                 * principal. */
                kerberos_derive_salting_principal_for_enctype(service_principal,
                                                                context,
                                                                ccache,
                                                                enctypes[i],
                                                                enctypes);
        }
}

/************************************************************************
 Wrapper function for the above.
 ************************************************************************/

BOOL kerberos_derive_salting_principal(char *service_principal)
{
        krb5_context context = NULL;
        krb5_enctype *enctypes = NULL;
        krb5_ccache ccache = NULL;
        krb5_error_code ret = 0;

        initialize_krb5_error_table();
        if ((ret = krb5_init_context(&context)) != 0) {
                DEBUG(1,("kerberos_derive_cifs_salting_principals: krb5_init_context failed. %s\n",
                        error_message(ret)));
                return False;
        }
        if ((ret = get_kerberos_allowed_etypes(context, &enctypes)) != 0) {
                DEBUG(1,("kerberos_derive_cifs_salting_principals: get_kerberos_allowed_etypes failed. %s\n",
                        error_message(ret)));
                goto out;
        }

        if ((ret = krb5_cc_resolve(context, LIBADS_CCACHE_NAME, &ccache)) != 0) {
                DEBUG(3, ("get_service_ticket: krb5_cc_resolve for %s failed: %s\n", 
                        LIBADS_CCACHE_NAME, error_message(ret)));
                goto out;
        }

        kerberos_derive_salting_principal_direct(context, ccache, enctypes, service_principal);

  out: 
        if (enctypes) {
                free_kerberos_etypes(context, enctypes);
        }
        if (ccache) {
                krb5_cc_destroy(context, ccache);
        }
        if (context) {
                krb5_free_context(context);
        }

        return ret ? False : True;
}

/************************************************************************
 Core function to try and determine what salt is being used for any keytab
 keys.
 ************************************************************************/

BOOL kerberos_derive_cifs_salting_principals(void)
{
        fstring my_fqdn;
        char *service = NULL;
        krb5_context context = NULL;
        krb5_enctype *enctypes = NULL;
        krb5_ccache ccache = NULL;
        krb5_error_code ret = 0;
        BOOL retval = False;

        initialize_krb5_error_table();
        if ((ret = krb5_init_context(&context)) != 0) {
                DEBUG(1,("kerberos_derive_cifs_salting_principals: krb5_init_context failed. %s\n",
                        error_message(ret)));
                return False;
        }
        if ((ret = get_kerberos_allowed_etypes(context, &enctypes)) != 0) {
                DEBUG(1,("kerberos_derive_cifs_salting_principals: get_kerberos_allowed_etypes failed. %s\n",
                        error_message(ret)));
                goto out;
        }

        if ((ret = krb5_cc_resolve(context, LIBADS_CCACHE_NAME, &ccache)) != 0) {
                DEBUG(3, ("get_service_ticket: krb5_cc_resolve for %s failed: %s\n", 
                        LIBADS_CCACHE_NAME, error_message(ret)));
                goto out;
        }

        if (asprintf(&service, "%s$", global_myname()) != -1) {
                strlower_m(service);
                kerberos_derive_salting_principal_direct(context, ccache, enctypes, service);
                SAFE_FREE(service);
        }
        if (asprintf(&service, "cifs/%s", global_myname()) != -1) {
                strlower_m(service);
                kerberos_derive_salting_principal_direct(context, ccache, enctypes, service);
                SAFE_FREE(service);
        }
        if (asprintf(&service, "host/%s", global_myname()) != -1) {
                strlower_m(service);
                kerberos_derive_salting_principal_direct(context, ccache, enctypes, service);
                SAFE_FREE(service);
        }
        if (asprintf(&service, "cifs/%s.%s", global_myname(), lp_realm()) != -1) {
                strlower_m(service);
                kerberos_derive_salting_principal_direct(context, ccache, enctypes, service);
                SAFE_FREE(service);
        }
        if (asprintf(&service, "host/%s.%s", global_myname(), lp_realm()) != -1) {
                strlower_m(service);
                kerberos_derive_salting_principal_direct(context, ccache, enctypes, service);
                SAFE_FREE(service);
        }
        name_to_fqdn(my_fqdn, global_myname());
        if (asprintf(&service, "cifs/%s", my_fqdn) != -1) {
                strlower_m(service);
                kerberos_derive_salting_principal_direct(context, ccache, enctypes, service);
                SAFE_FREE(service);
        }
        if (asprintf(&service, "host/%s", my_fqdn) != -1) {
                strlower_m(service);
                kerberos_derive_salting_principal_direct(context, ccache, enctypes, service);
                SAFE_FREE(service);
        }

        retval = True;

  out: 
        if (enctypes) {
                free_kerberos_etypes(context, enctypes);
        }
        if (ccache) {
                krb5_cc_destroy(context, ccache);
        }
        if (context) {
                krb5_free_context(context);
        }
        return retval;
}
#endif