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/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/*
 *  Authors: Jeffrey Stedfast <fejj@ximian.com>
 *
 *  Copyright 2001 Ximian, Inc. (www.ximian.com)
 *
 *  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., 59 Temple Street #330, Boston, MA 02111-1307, USA.
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#ifdef HAVE_KRB4

#include <krb.h>
/* MIT krb4 des.h #defines _. Sigh. We don't need it. #undef it here
 * so we get the gettexty _ definition later.
 */
#undef _

#include <string.h>
#include "camel-sasl-kerberos4.h"
#include "camel-service.h"

CamelServiceAuthType camel_sasl_kerberos4_authtype = {
    N_("Kerberos 4"),

    N_("This option will connect to the server using "
       "Kerberos 4 authentication."),

    "KERBEROS_V4",
    FALSE,
    FALSE
};

#define KERBEROS_V4_PROTECTION_NONE      1
#define KERBEROS_V4_PROTECTION_INTEGRITY 2
#define KERBEROS_V4_PROTECTION_PRIVACY   4

static CamelSaslClass *parent_class = NULL;

/* Returns the class for a CamelSaslKerberos4 */
#define CSK4_CLASS(so) CAMEL_SASL_KERBEROS4_CLASS (CAMEL_OBJECT_GET_CLASS (so))

static GByteArray *krb4_challenge (CamelSasl *sasl, GByteArray *token, CamelException *ex);

struct _CamelSaslKerberos4Private {
    int state;
    
    guint32 nonce_n;
    guint32 nonce_h;
    
    des_cblock session;
    des_key_schedule schedule;
};

static void
camel_sasl_kerberos4_class_init (CamelSaslKerberos4Class *camel_sasl_kerberos4_class)
{
    CamelSaslClass *camel_sasl_class = CAMEL_SASL_CLASS (camel_sasl_kerberos4_class);
    
    parent_class = CAMEL_SASL_CLASS (camel_type_get_global_classfuncs (camel_sasl_get_type ()));
    
    /* virtual method overload */
    camel_sasl_class->challenge = krb4_challenge;
}

static void
camel_sasl_kerberos4_init (gpointer object, gpointer klass)
{
    CamelSaslKerberos4 *sasl_krb4 = CAMEL_SASL_KERBEROS4 (object);
    
    sasl_krb4->priv = g_new0 (struct _CamelSaslKerberos4Private, 1);
}

static void
camel_sasl_kerberos4_finalize (CamelObject *object)
{
    CamelSaslKerberos4 *sasl = CAMEL_SASL_KERBEROS4 (object);

    if (sasl->priv) {
        memset (sasl->priv, 0, sizeof (sasl->priv));
        g_free (sasl->priv);
    }
}


CamelType
camel_sasl_kerberos4_get_type (void)
{
    static CamelType type = CAMEL_INVALID_TYPE;
    
    if (type == CAMEL_INVALID_TYPE) {
        type = camel_type_register (camel_sasl_get_type (),
                        "CamelSaslKerberos4",
                        sizeof (CamelSaslKerberos4),
                        sizeof (CamelSaslKerberos4Class),
                        (CamelObjectClassInitFunc) camel_sasl_kerberos4_class_init,
                        NULL,
                        (CamelObjectInitFunc) camel_sasl_kerberos4_init,
                        (CamelObjectFinalizeFunc) camel_sasl_kerberos4_finalize);
    }
    
    return type;
}

static GByteArray *
krb4_challenge (CamelSasl *sasl, GByteArray *token, CamelException *ex)
{
    struct _CamelSaslKerberos4Private *priv = CAMEL_SASL_KERBEROS4 (sasl)->priv;
    GByteArray *ret = NULL;
    char *inst, *realm, *username;
    struct hostent *h;
    int status, len;
    KTEXT_ST authenticator;
    CREDENTIALS credentials;
    guint32 plus1;

    /* Need to wait for the server */
    if (!token)
        return NULL;

    switch (priv->state) {
    case 0:
        if (token->len != 4)
            goto lose;

        memcpy (&priv->nonce_n, token->data, 4);
        priv->nonce_h = ntohl (priv->nonce_n);

        /* Our response is an authenticator including that number. */
        h = camel_service_gethost (sasl->service, ex);
        inst = g_strndup (h->h_name, strcspn (h->h_name, "."));
        g_strdown (inst);
        realm = g_strdup (krb_realmofhost (h->h_name));
        camel_free_host(h);
        status = krb_mk_req (&authenticator, sasl->service_name, inst, realm, priv->nonce_h);
        if (status == KSUCCESS) {
            status = krb_get_cred (sasl->service_name, inst, realm, &credentials);
            memcpy (priv->session, credentials.session, sizeof (priv->session));
            memset (&credentials, 0, sizeof (credentials));
        }
        g_free (inst);
        g_free (realm);

        if (status != KSUCCESS) {
            camel_exception_setv (ex, CAMEL_EXCEPTION_SERVICE_CANT_AUTHENTICATE,
                          _("Could not get Kerberos ticket:\n%s"),
                          krb_err_txt[status]);
            goto lose;
        }
        des_key_sched (&priv->session, priv->schedule);

        ret = g_byte_array_new ();
        g_byte_array_append (ret, (const guint8 *)authenticator.dat, authenticator.length);
        break;

    case 1:
        if (token->len != 8)
            goto lose;

        /* This one is encrypted. */
        des_ecb_encrypt ((des_cblock *)token->data, (des_cblock *)token->data, priv->schedule, 0);

        /* Check that the returned value is the original nonce plus one. */
        memcpy (&plus1, token->data, 4);
        if (ntohl (plus1) != priv->nonce_h + 1)
            goto lose;

        /* "the fifth octet contain[s] a bit-mask specifying the
         * protection mechanisms supported by the server"
         */
        if (!(token->data[4] & KERBEROS_V4_PROTECTION_NONE)) {
            g_warning ("Server does not support `no protection' :-(");
            goto lose;
        }

        username = sasl->service->url->user;
        len = strlen (username) + 9;
        len += 8 - len % 8;
        ret = g_byte_array_new ();
        g_byte_array_set_size (ret, len);
        memset (ret->data, 0, len);
        memcpy (ret->data, &priv->nonce_n, 4);
        ret->data[4] = KERBEROS_V4_PROTECTION_NONE;
        ret->data[5] = ret->data[6] = ret->data[7] = 0;
        strcpy (ret->data + 8, username);

        des_pcbc_encrypt ((void *)ret->data, (void *)ret->data, len,
                  priv->schedule, &priv->session, 1);
        memset (&priv->session, 0, sizeof (priv->session));

        sasl->authenticated = TRUE;
        break;
    }

    priv->state++;
    return ret;

 lose:
    memset (&priv->session, 0, sizeof (priv->session));

    if (!camel_exception_is_set (ex)) {
        camel_exception_set (ex, CAMEL_EXCEPTION_SERVICE_CANT_AUTHENTICATE,
                     _("Bad authentication response from server."));
    }
    return NULL;
}

#endif /* HAVE_KRB4 */