rlm_tacacs.c

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/*
 *   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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * $Id: 3a367b1e197065567f98139443132addf98699a2 $
 * @file rlm_tacacs.c
 * @brief A TACACS client library.
 *
 * @copyright 2023 Network RADIUS SAS (legal@networkradius.com)
 */
RCSID("$Id: 3a367b1e197065567f98139443132addf98699a2 $")
 
#include <freeradius-devel/io/application.h>
#include <freeradius-devel/server/modpriv.h>
#include <freeradius-devel/util/debug.h>
#include <freeradius-devel/util/dlist.h>
 
#include "rlm_tacacs.h"
 
static int type_parse(TALLOC_CTX *ctx, void *out, UNUSED void *parent, CONF_ITEM *ci, conf_parser_t const *rule);
 
/*
 *      Retransmission intervals for the packets we support.
 */
static conf_parser_t retry_config[] = {
        { FR_CONF_OFFSET("initial_rtx_time", fr_retry_config_t, irt), .dflt = STRINGIFY(2) },
        { FR_CONF_OFFSET("max_rtx_time", fr_retry_config_t, mrt), .dflt = STRINGIFY(16) },
        { FR_CONF_OFFSET("max_rtx_count", fr_retry_config_t, mrc), .dflt = STRINGIFY(5) },
        { FR_CONF_OFFSET("max_rtx_duration", fr_retry_config_t, mrd), .dflt = STRINGIFY(30) },
        CONF_PARSER_TERMINATOR
};
 
/*
 *      A mapping of configuration file names to internal variables.
 */
static conf_parser_t const module_config[] = {
        { FR_CONF_OFFSET_TYPE_FLAGS("transport", FR_TYPE_VOID, 0, rlm_tacacs_t, io_submodule),
          .func = module_rlm_submodule_parse },
 
        { FR_CONF_OFFSET_FLAGS("type", CONF_FLAG_NOT_EMPTY | CONF_FLAG_MULTI | CONF_FLAG_REQUIRED, rlm_tacacs_t, types),
          .func = type_parse },
 
        { FR_CONF_OFFSET("max_attributes", rlm_tacacs_t, max_attributes), .dflt = STRINGIFY(FR_MAX_ATTRIBUTES) },
 
        { FR_CONF_OFFSET("response_window", rlm_tacacs_t, response_window), .dflt = STRINGIFY(20) },
 
        { FR_CONF_OFFSET("zombie_period", rlm_tacacs_t, zombie_period), .dflt = STRINGIFY(40) },
 
        { FR_CONF_OFFSET("revive_interval", rlm_tacacs_t, revive_interval) },
 
        { FR_CONF_OFFSET_SUBSECTION("pool", 0, rlm_tacacs_t, trunk_conf, trunk_config ) },
 
        { FR_CONF_OFFSET_SUBSECTION("retry", 0, rlm_tacacs_t, retry, retry_config ) },
 
        CONF_PARSER_TERMINATOR
};
 
static fr_dict_t const *dict_tacacs;
 
extern fr_dict_autoload_t rlm_tacacs_dict[];
fr_dict_autoload_t rlm_tacacs_dict[] = {
        { .out = &dict_tacacs, .proto = "tacacs" },
        DICT_AUTOLOAD_TERMINATOR
};
 
static fr_dict_attr_t const *attr_packet_type;
 
extern fr_dict_attr_autoload_t rlm_tacacs_dict_attr[];
fr_dict_attr_autoload_t rlm_tacacs_dict_attr[] = {
        { .out = &attr_packet_type, .name = "Packet-Type", .type = FR_TYPE_UINT32, .dict = &dict_tacacs },
        DICT_AUTOLOAD_TERMINATOR
};
 
/** Set which types of packets we can parse
 *
 * @param[in] ctx       to allocate data in (instance of rlm_tacacs).
 * @param[out] out      Where to write the parsed data.
 * @param[in] parent    Base structure address.
 * @param[in] ci        #CONF_PAIR specifying the name of the type module.
 * @param[in] rule      unused.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
static int type_parse(UNUSED TALLOC_CTX *ctx, void *out, UNUSED void *parent,
                      CONF_ITEM *ci, UNUSED conf_parser_t const *rule)
{
        char const              *type_str = cf_pair_value(cf_item_to_pair(ci));
        fr_dict_enum_value_t const      *type_enum;
        uint32_t                code;
 
#ifndef NDEBUG
        CONF_SECTION            *cs = cf_item_to_section(cf_parent(ci));
#endif
 
        /*
         *      Must be the TACACS+ module
         */
        fr_assert(cs && (strcmp(cf_section_name1(cs), "tacacs") == 0));
 
        /*
         *      Allow the process module to be specified by
         *      packet type.
         */
        type_enum = fr_dict_enum_by_name(attr_packet_type, type_str, -1);
        if (!type_enum) {
                cf_log_err(ci, "Unknown TACACS+ packet type '%s'", type_str);
                return -1;
        }
 
        code = type_enum->value->vb_uint32;
 
        memcpy(out, &code, sizeof(code));
 
        return 0;
}
 
static void mod_tacacs_signal(module_ctx_t const *mctx, request_t *request, fr_signal_t action)
{
        rlm_tacacs_t const      *inst = talloc_get_type_abort_const(mctx->mi->data, rlm_tacacs_t);
        rlm_tacacs_io_t const   *io = (rlm_tacacs_io_t const *)inst->io_submodule->exported;            /* Public symbol exported by the module */
 
        /*
         *      We received a duplicate packet, ignore the dup, and rely on the
         *      IO submodule / trunk to do it's own retransmissions.
         */
        if (action == FR_SIGNAL_DUP) return;
 
        if (!io->signal) return;
 
        io->signal(MODULE_CTX(inst->io_submodule,
                              module_thread(inst->io_submodule)->data, mctx->env_data,
                              mctx->rctx), request, action);
}
 
/** Send packets outbound.
 *
 */
static unlang_action_t CC_HINT(nonnull) mod_process(unlang_result_t *p_result, module_ctx_t const *mctx, request_t *request)
{
        rlm_tacacs_t const      *inst = talloc_get_type_abort_const(mctx->mi->data, rlm_tacacs_t);
        unlang_action_t         ua;
 
        void                    *rctx = NULL;
 
        if (!FR_TACACS_PACKET_CODE_VALID(request->packet->code)) {
                REDEBUG("Invalid packet code %d", request->packet->code);
                RETURN_UNLANG_FAIL;
        }
 
        if (!inst->allowed[request->packet->code]) {
                REDEBUG("Packet code %s is disallowed by the configuration",
                       fr_tacacs_packet_names[request->packet->code]);
                RETURN_UNLANG_FAIL;
        }
 
        /*
         *      Push the request and it's data to the IO submodule.
         *
         *      This may return YIELD, for "please yield", or it may
         *      return another code which indicates what happened to
         *      the request...
         */
        ua = inst->io->enqueue(p_result, &rctx, inst->io_submodule->data,
                               module_thread(inst->io_submodule)->data, request);
        if (ua != UNLANG_ACTION_YIELD) {
                fr_assert(rctx == NULL);
                return UNLANG_ACTION_CALCULATE_RESULT;
        }
 
        return unlang_module_yield(request, inst->io->resume, mod_tacacs_signal, 0, rctx);
}
 
static int mod_instantiate(module_inst_ctx_t const *mctx)
{
        size_t i, num_types;
        rlm_tacacs_t *inst = talloc_get_type_abort(mctx->mi->data, rlm_tacacs_t);
 
        inst->io = (rlm_tacacs_io_t const *)inst->io_submodule->exported;       /* Public symbol exported by the module */
        inst->name = mctx->mi->name;
 
        /*
         *      These limits are specific to TACACS, and cannot be over-ridden, due to 8-bit ID fields!
         */
        FR_INTEGER_BOUND_CHECK("trunk.per_connection_max", inst->trunk_conf.max_req_per_conn, >=, 2);
        FR_INTEGER_BOUND_CHECK("trunk.per_connection_max", inst->trunk_conf.max_req_per_conn, <=, 255);
        FR_INTEGER_BOUND_CHECK("trunk.per_connection_target", inst->trunk_conf.target_req_per_conn, <=, inst->trunk_conf.max_req_per_conn / 2);
 
        FR_TIME_DELTA_BOUND_CHECK("response_window", inst->response_window, >=, fr_time_delta_from_sec(1));
        FR_TIME_DELTA_BOUND_CHECK("response_window", inst->response_window, <=, fr_time_delta_from_sec(120));
 
        FR_TIME_DELTA_BOUND_CHECK("zombie_period", inst->zombie_period, >=, fr_time_delta_from_sec(1));
        FR_TIME_DELTA_BOUND_CHECK("zombie_period", inst->zombie_period, <=, fr_time_delta_from_sec(120));
 
        FR_TIME_DELTA_BOUND_CHECK("revive_interval", inst->revive_interval, >=, fr_time_delta_from_sec(10));
        FR_TIME_DELTA_BOUND_CHECK("revive_interval", inst->revive_interval, <=, fr_time_delta_from_sec(3600));
 
        num_types = talloc_array_length(inst->types);
        fr_assert(num_types > 0);
 
        /*
         *      Allow for O(1) lookup later...
         */
        for (i = 0; i < num_types; i++) {
                uint32_t code;
 
                code = inst->types[i];
                fr_assert(FR_TACACS_PACKET_CODE_VALID(code));
 
                inst->allowed[code] = true;
        }
 
 
        return 0;
}
 
static int mod_load(void)
{
        if (fr_tacacs_global_init() < 0) {
                PERROR("Failed initialising protocol library");
                return -1;
        }
        return 0;
}
 
static void mod_unload(void)
{
        fr_tacacs_global_free();
}
 
/*
 *      The module name should be the only globally exported symbol.
 *      That is, everything else should be 'static'.
 *
 *      If the module needs to temporarily modify it's instantiation
 *      data, the type should be changed to MODULE_TYPE_THREAD_UNSAFE.
 *      The server will then take care of ensuring that the module
 *      is single-threaded.
 */
extern module_rlm_t rlm_tacacs;
module_rlm_t rlm_tacacs = {
        .common = {
                .magic          = MODULE_MAGIC_INIT,
                .name           = "tacacs",
                .inst_size      = sizeof(rlm_tacacs_t),
                .config         = module_config,
                .dict           = &dict_tacacs,
 
                .onload         = mod_load,
                .unload         = mod_unload,
 
                .instantiate    = mod_instantiate,
        },
        .method_group = {
                .bindings = (module_method_binding_t[]){
                        { .section = SECTION_NAME(CF_IDENT_ANY, CF_IDENT_ANY), .method = mod_process },
                        MODULE_BINDING_TERMINATOR
                }
        }
};