/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */

/* kdc/dispatch.c - Dispatch an incoming packet */

/*

 * Copyright 1990, 2009 by the Massachusetts Institute of Technology.

 *

 * Export of this software from the United States of America may

 *   require a specific license from the United States Government.

 *   It is the responsibility of any person or organization contemplating

 *   export to obtain such a license before exporting.

 *

 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and

 * distribute this software and its documentation for any purpose and

 * without fee is hereby granted, provided that the above copyright

 * notice appear in all copies and that both that copyright notice and

 * this permission notice appear in supporting documentation, and that

 * the name of M.I.T. not be used in advertising or publicity pertaining

 * to distribution of the software without specific, written prior

 * permission.  Furthermore if you modify this software you must label

 * your software as modified software and not distribute it in such a

 * fashion that it might be confused with the original M.I.T. software.

 * M.I.T. makes no representations about the suitability of

 * this software for any purpose.  It is provided "as is" without express

 * or implied warranty.

 */

#include "k5-int.h"

#include <syslog.h>

#include "kdc_util.h"

#include "extern.h"

#include "adm_proto.h"

#include "realm_data.h"

#include <netinet/in.h>

#include <arpa/inet.h>

#include <string.h>

static krb5_int32 last_usec = 0, last_os_random = 0;

static krb5_error_code make_too_big_error(kdc_realm_t *kdc_active_realm,

                                          krb5_data **out);

struct dispatch_state {

    loop_respond_fn respond;

    void *arg;

    krb5_data *request;

    int is_tcp;

    kdc_realm_t *active_realm;

    krb5_context kdc_err_context;

};

static void

finish_dispatch(struct dispatch_state *state, krb5_error_code code,

                krb5_data *response)

{

    loop_respond_fn oldrespond = state->respond;

    void *oldarg = state->arg;

    kdc_realm_t *kdc_active_realm = state->active_realm;

    if (state->is_tcp == 0 && response &&

        response->length > (unsigned int)max_dgram_reply_size) {

        krb5_free_data(kdc_context, response);

        response = NULL;

        code = make_too_big_error(kdc_active_realm, &response);

        if (code)

            krb5_klog_syslog(LOG_ERR, "error constructing "

                             "KRB_ERR_RESPONSE_TOO_BIG error: %s",

                             error_message(code));

    }

    free(state);

    (*oldrespond)(oldarg, code, response);

}

static void

finish_dispatch_cache(void *arg, krb5_error_code code, krb5_data *response)

{

    struct dispatch_state *state = arg;

    krb5_context kdc_err_context = state->kdc_err_context;

#ifndef NOCACHE

    /* Remove the null cache entry unless we actually want to discard this

     * request. */

    if (code != KRB5KDC_ERR_DISCARD)

        kdc_remove_lookaside(kdc_err_context, state->request);

    /* Put the response into the lookaside buffer (if we produced one). */

    if (code == 0 && response != NULL)

        kdc_insert_lookaside(kdc_err_context, state->request, response);

#endif

    finish_dispatch(state, code, response);

}

static void

reseed_random(krb5_context kdc_err_context)

{

    krb5_error_code retval;

    krb5_timestamp now;

    krb5_int32 now_usec, usec_difference;

    krb5_data data;

    retval = krb5_crypto_us_timeofday(&now, &now_usec);

    if (retval == 0) {

        usec_difference = now_usec - last_usec;

        if (last_os_random == 0)

            last_os_random = now;

        /* Grab random data from OS every hour*/

        if (ts_delta(now, last_os_random) >= 60 * 60) {

            krb5_c_random_os_entropy(kdc_err_context, 0, NULL);

            last_os_random = now;

        }

        data.length = sizeof(krb5_int32);

        data.data = (void *)&usec_difference;

        krb5_c_random_add_entropy(kdc_err_context,

                                  KRB5_C_RANDSOURCE_TIMING, &data);

        last_usec = now_usec;

    }

}

void

dispatch(void *cb, const krb5_fulladdr *local_addr,

         const krb5_fulladdr *remote_addr, krb5_data *pkt, int is_tcp,

         verto_ctx *vctx, loop_respond_fn respond, void *arg)

{

    krb5_error_code retval;

    krb5_kdc_req *req = NULL;

    krb5_data *response = NULL;

    struct dispatch_state *state;

    struct server_handle *handle = cb;

    krb5_context kdc_err_context = handle->kdc_err_context;

    state = k5alloc(sizeof(*state), &retval);

    if (state == NULL) {

        (*respond)(arg, retval, NULL);

        return;

    }

    state->respond = respond;

    state->arg = arg;

    state->request = pkt;

    state->is_tcp = is_tcp;

    state->kdc_err_context = kdc_err_context;

    /* decode incoming packet, and dispatch */

#ifndef NOCACHE

    /* try the replay lookaside buffer */

    if (kdc_check_lookaside(kdc_err_context, pkt, &response)) {

        /* a hit! */

        const char *name = 0;

        char buf[46];

        name = inet_ntop(ADDRTYPE2FAMILY(remote_addr->address->addrtype),

                         remote_addr->address->contents, buf, sizeof(buf));

        if (name == 0)

            name = "[unknown address type]";

        if (response)

            krb5_klog_syslog(LOG_INFO,

                             "DISPATCH: repeated (retransmitted?) request "

                             "from %s, resending previous response", name);

        else

            krb5_klog_syslog(LOG_INFO,

                             "DISPATCH: repeated (retransmitted?) request "

                             "from %s during request processing, dropping "

                             "repeated request", name);

        finish_dispatch(state, response ? 0 : KRB5KDC_ERR_DISCARD, response);

        return;

    }

    /* Insert a NULL entry into the lookaside to indicate that this request

     * is currently being processed. */

    kdc_insert_lookaside(kdc_err_context, pkt, NULL);

#endif

    reseed_random(kdc_err_context);

    /* try TGS_REQ first; they are more common! */

    if (krb5_is_tgs_req(pkt))

        retval = decode_krb5_tgs_req(pkt, &req;;

    else if (krb5_is_as_req(pkt))

        retval = decode_krb5_as_req(pkt, &req;;

    else

        retval = KRB5KRB_AP_ERR_MSG_TYPE;

    if (retval)

        goto done;

    state->active_realm = setup_server_realm(handle, req->server);

    if (state->active_realm == NULL) {

        retval = KRB5KDC_ERR_WRONG_REALM;

        goto done;

    }

    if (krb5_is_tgs_req(pkt)) {

        /* process_tgs_req frees the request */

        retval = process_tgs_req(req, pkt, remote_addr, state->active_realm,

                                 &response);

        req = NULL;

    } else if (krb5_is_as_req(pkt)) {

        /* process_as_req frees the request and calls finish_dispatch_cache. */

        process_as_req(req, pkt, local_addr, remote_addr, state->active_realm,

                       vctx, finish_dispatch_cache, state);

        return;

    }

done:

    krb5_free_kdc_req(kdc_err_context, req);

    finish_dispatch_cache(state, retval, response);

}

static krb5_error_code

make_too_big_error(kdc_realm_t *kdc_active_realm, krb5_data **out)

{

    krb5_error errpkt;

    krb5_error_code retval;

    krb5_data *scratch;

    *out = NULL;

    memset(&errpkt, 0, sizeof(errpkt));

    retval = krb5_us_timeofday(kdc_context, &errpkt.stime, &errpkt.susec);

    if (retval)

        return retval;

    errpkt.error = KRB_ERR_RESPONSE_TOO_BIG;

    errpkt.server = tgs_server;

    errpkt.client = NULL;

    errpkt.text.length = 0;

    errpkt.text.data = 0;

    errpkt.e_data.length = 0;

    errpkt.e_data.data = 0;

    scratch = malloc(sizeof(*scratch));

    if (scratch == NULL)

        return ENOMEM;

    retval = krb5_mk_error(kdc_context, &errpkt, scratch);

    if (retval) {

        free(scratch);

        return retval;

    }

    *out = scratch;

    return 0;

}

krb5_context get_context(void *handle)

{

    struct server_handle *sh = handle;

    return sh->kdc_err_context;

}