Code: finish_process_as_req(struct as_req_state *state, krb5_error_code errcode)
{
    krb5_key_data *server_key;
    krb5_keyblock *as_encrypting_key = NULL;
    krb5_data *response = NULL;
    const char *emsg = 0;
    int did_log = 0;
    loop_respond_fn oldrespond;
    void *oldarg;
    kdc_realm_t *kdc_active_realm = state->active_realm;
    krb5_audit_state *au_state = state->au_state;

    assert(state);
    oldrespond = state->respond;
    oldarg = state->arg;

    if (errcode)
        goto egress;

    au_state->stage = ENCR_REP;

    if ((errcode = validate_forwardable(state->request, *state->client,
                                        *state->server, state->kdc_time,
                                        &state->status))) {
        errcode += ERROR_TABLE_BASE_krb5;
        goto egress;
    }

    errcode = check_indicators(kdc_context, state->server,
                               state->auth_indicators);
    if (errcode) {
        state->status = "HIGHER_AUTHENTICATION_REQUIRED";
        goto egress;
    }

    state->ticket_reply.enc_part2 = &state->enc_tkt_reply;

    /*
     * Find the server key
     */
    if ((errcode = krb5_dbe_find_enctype(kdc_context, state->server,
                                         -1, /* ignore keytype   */
                                         -1, /* Ignore salttype  */
                                         0,  /* Get highest kvno */
                                         &server_key))) {
        state->status = "FINDING_SERVER_KEY";
        goto egress;
    }

    /*
     * Convert server->key into a real key
     * (it may be encrypted in the database)
     *
     *  server_keyblock is later used to generate auth data signatures
     */
    if ((errcode = krb5_dbe_decrypt_key_data(kdc_context, NULL,
                                             server_key,
                                             &state->server_keyblock,
                                             NULL))) {
        state->status = "DECRYPT_SERVER_KEY";
        goto egress;
    }

    /* Start assembling the response */
    state->reply.msg_type = KRB5_AS_REP;
    state->reply.client = state->enc_tkt_reply.client; /* post canonization */
    state->reply.ticket = &state->ticket_reply;
    state->reply_encpart.session = &state->session_key;
    if ((errcode = fetch_last_req_info(state->client,
                                       &state->reply_encpart.last_req))) {
        state->status = "FETCH_LAST_REQ";
        goto egress;
    }
    state->reply_encpart.nonce = state->request->nonce;
    state->reply_encpart.key_exp = get_key_exp(state->client);
    state->reply_encpart.flags = state->enc_tkt_reply.flags;
    state->reply_encpart.server = state->ticket_reply.server;

    /* copy the time fields EXCEPT for authtime; it's location
     *  is used for ktime
     */
    state->reply_encpart.times = state->enc_tkt_reply.times;
    state->reply_encpart.times.authtime = state->authtime = state->kdc_time;

    state->reply_encpart.caddrs = state->enc_tkt_reply.caddrs;
    state->reply_encpart.enc_padata = NULL;

    /* Fetch the padata info to be returned (do this before
     *  authdata to handle possible replacement of reply key
     */
    errcode = return_padata(kdc_context, &state->rock, state->req_pkt,
                            state->request, &state->reply,
                            &state->client_keyblock, &state->pa_context);
    if (errcode) {
        state->status = "KDC_RETURN_PADATA";
        goto egress;
    }

    /* If we didn't find a client long-term key and no preauth mechanism
     * replaced the reply key, error out now. */
    if (state->client_keyblock.enctype == ENCTYPE_NULL) {
        state->status = "CANT_FIND_CLIENT_KEY";
        errcode = KRB5KDC_ERR_ETYPE_NOSUPP;
        goto egress;
    }

    errcode = handle_authdata(kdc_context,
                              state->c_flags,
                              state->client,
                              state->server,
                              NULL,
                              state->local_tgt,
                              &state->client_keyblock,
                              &state->server_keyblock,
                              NULL,
                              state->req_pkt,
                              state->request,
                              NULL, /* for_user_princ */
                              NULL, /* enc_tkt_request */
                              state->auth_indicators,
                              &state->enc_tkt_reply);
    if (errcode) {
        krb5_klog_syslog(LOG_INFO, _("AS_REQ : handle_authdata (%d)"),
                         errcode);
        state->status = "HANDLE_AUTHDATA";
        goto egress;
    }

    errcode = krb5_encrypt_tkt_part(kdc_context, &state->server_keyblock,
                                    &state->ticket_reply);
    if (errcode) {
        state->status = "ENCRYPT_TICKET";
        goto egress;
    }

    errcode = kau_make_tkt_id(kdc_context, &state->ticket_reply,
                              &au_state->tkt_out_id);
    if (errcode) {
        state->status = "GENERATE_TICKET_ID";
        goto egress;
    }

    state->ticket_reply.enc_part.kvno = server_key->key_data_kvno;
    errcode = kdc_fast_response_handle_padata(state->rstate,
                                              state->request,
                                              &state->reply,
                                              state->client_keyblock.enctype);
    if (errcode) {
        state->status = "MAKE_FAST_RESPONSE";
        goto egress;
    }

    /* now encode/encrypt the response */

    state->reply.enc_part.enctype = state->client_keyblock.enctype;

    errcode = kdc_fast_handle_reply_key(state->rstate, &state->client_keyblock,
                                        &as_encrypting_key);
    if (errcode) {
        state->status = "MAKE_FAST_REPLY_KEY";
        goto egress;
    }
    errcode = return_enc_padata(kdc_context, state->req_pkt, state->request,
                                as_encrypting_key, state->server,
                                &state->reply_encpart, FALSE);
    if (errcode) {
        state->status = "KDC_RETURN_ENC_PADATA";
        goto egress;
    }

    if (kdc_fast_hide_client(state->rstate))
        state->reply.client = (krb5_principal)krb5_anonymous_principal();
    errcode = krb5_encode_kdc_rep(kdc_context, KRB5_AS_REP,
                                  &state->reply_encpart, 0,
                                  as_encrypting_key,
                                  &state->reply, &response);
    if (state->client_key != NULL)
        state->reply.enc_part.kvno = state->client_key->key_data_kvno;
    if (errcode) {
        state->status = "ENCODE_KDC_REP";
        goto egress;
    }

    /* these parts are left on as a courtesy from krb5_encode_kdc_rep so we
       can use them in raw form if needed.  But, we don't... */
    memset(state->reply.enc_part.ciphertext.data, 0,
           state->reply.enc_part.ciphertext.length);
    free(state->reply.enc_part.ciphertext.data);

    log_as_req(kdc_context, state->local_addr, state->remote_addr,
               state->request, &state->reply, state->client, state->cname,
               state->server, state->sname, state->authtime, 0, 0, 0);
     did_log = 1;
 
 egress:
    if (errcode != 0)
        assert (state->status != 0);
 
     au_state->status = state->status;
     au_state->reply = &state->reply;
    kau_as_req(kdc_context,
              (errcode || state->preauth_err) ? FALSE : TRUE, au_state);
    kau_free_kdc_req(au_state);

    free_padata_context(kdc_context, state->pa_context);
    if (as_encrypting_key)
        krb5_free_keyblock(kdc_context, as_encrypting_key);
    if (errcode)
        emsg = krb5_get_error_message(kdc_context, errcode);

    if (state->status) {
        log_as_req(kdc_context, state->local_addr, state->remote_addr,
                   state->request, &state->reply, state->client,
                   state->cname, state->server, state->sname, state->authtime,
                   state->status, errcode, emsg);
        did_log = 1;
    }
    if (errcode) {
        if (state->status == 0) {
            state->status = emsg;
        }
        if (errcode != KRB5KDC_ERR_DISCARD) {
            errcode -= ERROR_TABLE_BASE_krb5;
            if (errcode < 0 || errcode > KRB_ERR_MAX)
                errcode = KRB_ERR_GENERIC;

            errcode = prepare_error_as(state->rstate, state->request,
                                       state->local_tgt, errcode,
                                       state->e_data, state->typed_e_data,
                                       ((state->client != NULL) ?
                                        state->client->princ : NULL),
                                       &response, state->status);
            state->status = 0;
        }
    }

    if (emsg)
        krb5_free_error_message(kdc_context, emsg);
    if (state->enc_tkt_reply.authorization_data != NULL)
        krb5_free_authdata(kdc_context,
                           state->enc_tkt_reply.authorization_data);
    if (state->server_keyblock.contents != NULL)
        krb5_free_keyblock_contents(kdc_context, &state->server_keyblock);
    if (state->client_keyblock.contents != NULL)
        krb5_free_keyblock_contents(kdc_context, &state->client_keyblock);
    if (state->reply.padata != NULL)
        krb5_free_pa_data(kdc_context, state->reply.padata);
    if (state->reply_encpart.enc_padata)
        krb5_free_pa_data(kdc_context, state->reply_encpart.enc_padata);

    if (state->cname != NULL)
        free(state->cname);
    if (state->sname != NULL)
        free(state->sname);
    krb5_db_free_principal(kdc_context, state->client);
    krb5_db_free_principal(kdc_context, state->server);
    krb5_db_free_principal(kdc_context, state->local_tgt_storage);
    if (state->session_key.contents != NULL)
        krb5_free_keyblock_contents(kdc_context, &state->session_key);
    if (state->ticket_reply.enc_part.ciphertext.data != NULL) {
        memset(state->ticket_reply.enc_part.ciphertext.data , 0,
               state->ticket_reply.enc_part.ciphertext.length);
        free(state->ticket_reply.enc_part.ciphertext.data);
    }

    krb5_free_pa_data(kdc_context, state->e_data);
    krb5_free_data(kdc_context, state->inner_body);
    kdc_free_rstate(state->rstate);
    krb5_free_kdc_req(kdc_context, state->request);
    k5_free_data_ptr_list(state->auth_indicators);
    assert(did_log != 0);

    free(state);
    (*oldrespond)(oldarg, errcode, response);
}

Commit Message: Prevent KDC unset status assertion failures

Assign status values if S4U2Self padata fails to decode, if an
S4U2Proxy request uses invalid KDC options, or if an S4U2Proxy request
uses an evidence ticket which does not match the canonicalized request
server principal name.  Reported by Samuel Cabrero.

If a status value is not assigned during KDC processing, default to
"UNKNOWN_REASON" rather than failing an assertion.  This change will
prevent future denial of service bugs due to similar mistakes, and
will allow us to omit assigning status values for unlikely errors such
as small memory allocation failures.

CVE-2017-11368:

In MIT krb5 1.7 and later, an authenticated attacker can cause an
assertion failure in krb5kdc by sending an invalid S4U2Self or
S4U2Proxy request.

  CVSSv3 Vector: AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:H/RL:O/RC:C

ticket: 8599 (new)
target_version: 1.15-next
target_version: 1.14-next
tags: pullup
CWE ID: CWE-617
finish_process_as_req(struct as_req_state *state, krb5_error_code errcode)
{
    krb5_key_data *server_key;
    krb5_keyblock *as_encrypting_key = NULL;
    krb5_data *response = NULL;
    const char *emsg = 0;
    int did_log = 0;
    loop_respond_fn oldrespond;
    void *oldarg;
    kdc_realm_t *kdc_active_realm = state->active_realm;
    krb5_audit_state *au_state = state->au_state;

    assert(state);
    oldrespond = state->respond;
    oldarg = state->arg;

    if (errcode)
        goto egress;

    au_state->stage = ENCR_REP;

    if ((errcode = validate_forwardable(state->request, *state->client,
                                        *state->server, state->kdc_time,
                                        &state->status))) {
        errcode += ERROR_TABLE_BASE_krb5;
        goto egress;
    }

    errcode = check_indicators(kdc_context, state->server,
                               state->auth_indicators);
    if (errcode) {
        state->status = "HIGHER_AUTHENTICATION_REQUIRED";
        goto egress;
    }

    state->ticket_reply.enc_part2 = &state->enc_tkt_reply;

    /*
     * Find the server key
     */
    if ((errcode = krb5_dbe_find_enctype(kdc_context, state->server,
                                         -1, /* ignore keytype   */
                                         -1, /* Ignore salttype  */
                                         0,  /* Get highest kvno */
                                         &server_key))) {
        state->status = "FINDING_SERVER_KEY";
        goto egress;
    }

    /*
     * Convert server->key into a real key
     * (it may be encrypted in the database)
     *
     *  server_keyblock is later used to generate auth data signatures
     */
    if ((errcode = krb5_dbe_decrypt_key_data(kdc_context, NULL,
                                             server_key,
                                             &state->server_keyblock,
                                             NULL))) {
        state->status = "DECRYPT_SERVER_KEY";
        goto egress;
    }

    /* Start assembling the response */
    state->reply.msg_type = KRB5_AS_REP;
    state->reply.client = state->enc_tkt_reply.client; /* post canonization */
    state->reply.ticket = &state->ticket_reply;
    state->reply_encpart.session = &state->session_key;
    if ((errcode = fetch_last_req_info(state->client,
                                       &state->reply_encpart.last_req))) {
        state->status = "FETCH_LAST_REQ";
        goto egress;
    }
    state->reply_encpart.nonce = state->request->nonce;
    state->reply_encpart.key_exp = get_key_exp(state->client);
    state->reply_encpart.flags = state->enc_tkt_reply.flags;
    state->reply_encpart.server = state->ticket_reply.server;

    /* copy the time fields EXCEPT for authtime; it's location
     *  is used for ktime
     */
    state->reply_encpart.times = state->enc_tkt_reply.times;
    state->reply_encpart.times.authtime = state->authtime = state->kdc_time;

    state->reply_encpart.caddrs = state->enc_tkt_reply.caddrs;
    state->reply_encpart.enc_padata = NULL;

    /* Fetch the padata info to be returned (do this before
     *  authdata to handle possible replacement of reply key
     */
    errcode = return_padata(kdc_context, &state->rock, state->req_pkt,
                            state->request, &state->reply,
                            &state->client_keyblock, &state->pa_context);
    if (errcode) {
        state->status = "KDC_RETURN_PADATA";
        goto egress;
    }

    /* If we didn't find a client long-term key and no preauth mechanism
     * replaced the reply key, error out now. */
    if (state->client_keyblock.enctype == ENCTYPE_NULL) {
        state->status = "CANT_FIND_CLIENT_KEY";
        errcode = KRB5KDC_ERR_ETYPE_NOSUPP;
        goto egress;
    }

    errcode = handle_authdata(kdc_context,
                              state->c_flags,
                              state->client,
                              state->server,
                              NULL,
                              state->local_tgt,
                              &state->client_keyblock,
                              &state->server_keyblock,
                              NULL,
                              state->req_pkt,
                              state->request,
                              NULL, /* for_user_princ */
                              NULL, /* enc_tkt_request */
                              state->auth_indicators,
                              &state->enc_tkt_reply);
    if (errcode) {
        krb5_klog_syslog(LOG_INFO, _("AS_REQ : handle_authdata (%d)"),
                         errcode);
        state->status = "HANDLE_AUTHDATA";
        goto egress;
    }

    errcode = krb5_encrypt_tkt_part(kdc_context, &state->server_keyblock,
                                    &state->ticket_reply);
    if (errcode) {
        state->status = "ENCRYPT_TICKET";
        goto egress;
    }

    errcode = kau_make_tkt_id(kdc_context, &state->ticket_reply,
                              &au_state->tkt_out_id);
    if (errcode) {
        state->status = "GENERATE_TICKET_ID";
        goto egress;
    }

    state->ticket_reply.enc_part.kvno = server_key->key_data_kvno;
    errcode = kdc_fast_response_handle_padata(state->rstate,
                                              state->request,
                                              &state->reply,
                                              state->client_keyblock.enctype);
    if (errcode) {
        state->status = "MAKE_FAST_RESPONSE";
        goto egress;
    }

    /* now encode/encrypt the response */

    state->reply.enc_part.enctype = state->client_keyblock.enctype;

    errcode = kdc_fast_handle_reply_key(state->rstate, &state->client_keyblock,
                                        &as_encrypting_key);
    if (errcode) {
        state->status = "MAKE_FAST_REPLY_KEY";
        goto egress;
    }
    errcode = return_enc_padata(kdc_context, state->req_pkt, state->request,
                                as_encrypting_key, state->server,
                                &state->reply_encpart, FALSE);
    if (errcode) {
        state->status = "KDC_RETURN_ENC_PADATA";
        goto egress;
    }

    if (kdc_fast_hide_client(state->rstate))
        state->reply.client = (krb5_principal)krb5_anonymous_principal();
    errcode = krb5_encode_kdc_rep(kdc_context, KRB5_AS_REP,
                                  &state->reply_encpart, 0,
                                  as_encrypting_key,
                                  &state->reply, &response);
    if (state->client_key != NULL)
        state->reply.enc_part.kvno = state->client_key->key_data_kvno;
    if (errcode) {
        state->status = "ENCODE_KDC_REP";
        goto egress;
    }

    /* these parts are left on as a courtesy from krb5_encode_kdc_rep so we
       can use them in raw form if needed.  But, we don't... */
    memset(state->reply.enc_part.ciphertext.data, 0,
           state->reply.enc_part.ciphertext.length);
    free(state->reply.enc_part.ciphertext.data);

    log_as_req(kdc_context, state->local_addr, state->remote_addr,
               state->request, &state->reply, state->client, state->cname,
               state->server, state->sname, state->authtime, 0, 0, 0);
     did_log = 1;
 
 egress:
    if (errcode != 0 && state->status == NULL)
        state->status = "UNKNOWN_REASON";
 
     au_state->status = state->status;
     au_state->reply = &state->reply;
    kau_as_req(kdc_context,
              (errcode || state->preauth_err) ? FALSE : TRUE, au_state);
    kau_free_kdc_req(au_state);

    free_padata_context(kdc_context, state->pa_context);
    if (as_encrypting_key)
        krb5_free_keyblock(kdc_context, as_encrypting_key);
    if (errcode)
        emsg = krb5_get_error_message(kdc_context, errcode);

    if (state->status) {
        log_as_req(kdc_context, state->local_addr, state->remote_addr,
                   state->request, &state->reply, state->client,
                   state->cname, state->server, state->sname, state->authtime,
                   state->status, errcode, emsg);
        did_log = 1;
    }
    if (errcode) {
        if (state->status == 0) {
            state->status = emsg;
        }
        if (errcode != KRB5KDC_ERR_DISCARD) {
            errcode -= ERROR_TABLE_BASE_krb5;
            if (errcode < 0 || errcode > KRB_ERR_MAX)
                errcode = KRB_ERR_GENERIC;

            errcode = prepare_error_as(state->rstate, state->request,
                                       state->local_tgt, errcode,
                                       state->e_data, state->typed_e_data,
                                       ((state->client != NULL) ?
                                        state->client->princ : NULL),
                                       &response, state->status);
            state->status = 0;
        }
    }

    if (emsg)
        krb5_free_error_message(kdc_context, emsg);
    if (state->enc_tkt_reply.authorization_data != NULL)
        krb5_free_authdata(kdc_context,
                           state->enc_tkt_reply.authorization_data);
    if (state->server_keyblock.contents != NULL)
        krb5_free_keyblock_contents(kdc_context, &state->server_keyblock);
    if (state->client_keyblock.contents != NULL)
        krb5_free_keyblock_contents(kdc_context, &state->client_keyblock);
    if (state->reply.padata != NULL)
        krb5_free_pa_data(kdc_context, state->reply.padata);
    if (state->reply_encpart.enc_padata)
        krb5_free_pa_data(kdc_context, state->reply_encpart.enc_padata);

    if (state->cname != NULL)
        free(state->cname);
    if (state->sname != NULL)
        free(state->sname);
    krb5_db_free_principal(kdc_context, state->client);
    krb5_db_free_principal(kdc_context, state->server);
    krb5_db_free_principal(kdc_context, state->local_tgt_storage);
    if (state->session_key.contents != NULL)
        krb5_free_keyblock_contents(kdc_context, &state->session_key);
    if (state->ticket_reply.enc_part.ciphertext.data != NULL) {
        memset(state->ticket_reply.enc_part.ciphertext.data , 0,
               state->ticket_reply.enc_part.ciphertext.length);
        free(state->ticket_reply.enc_part.ciphertext.data);
    }

    krb5_free_pa_data(kdc_context, state->e_data);
    krb5_free_data(kdc_context, state->inner_body);
    kdc_free_rstate(state->rstate);
    krb5_free_kdc_req(kdc_context, state->request);
    k5_free_data_ptr_list(state->auth_indicators);
    assert(did_log != 0);

    free(state);
    (*oldrespond)(oldarg, errcode, response);
}
