proto_dns_udp.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: a51f02412bd56f1be3a9c4c3b6190b8d9ba52798 $
 * @file proto_dns_udp.c
 * @brief DNS handler for UDP.
 *
 * @copyright 2020 Network RADIUS SAS (legal@networkradius.com)
 */
#define LOG_PREFIX "proto_dns_udp"
 
#include <freeradius-devel/server/cf_util.h>
#include <freeradius-devel/util/udp.h>
#include <freeradius-devel/util/trie.h>
#include <freeradius-devel/io/application.h>
#include <freeradius-devel/io/listen.h>
#include <freeradius-devel/io/schedule.h>
#include <freeradius-devel/protocol/dns/freeradius.internal.h>
#include "proto_dns.h"
 
extern fr_app_io_t proto_dns_udp;
 
typedef struct {
        char const                      *name;                  //!< socket name
        int                             sockfd;
 
        fr_io_address_t                 *connection;            //!< for connected sockets.
 
        fr_stats_t                      stats;                  //!< statistics for this socket
}  proto_dns_udp_thread_t;
 
typedef struct {
        CONF_SECTION                    *cs;                    //!< our configuration
 
        fr_ipaddr_t                     ipaddr;                 //!< IP address to listen on.
 
        char const                      *interface;             //!< Interface to bind to.
 
        uint32_t                        recv_buff;              //!< How big the kernel's receive buffer should be.
 
        uint32_t                        max_packet_size;        //!< for message ring buffer.
        uint32_t                        max_attributes;         //!< Limit maximum decodable attributes.
 
        uint16_t                        port;                   //!< Port to listen on.
 
        bool                            recv_buff_is_set;       //!< Whether we were provided with a receive
                                                                //!< buffer value.
 
        fr_client_list_t                        *clients;               //!< local clients
        fr_client_t                     *default_client;        //!< default 0/0 client
 
        fr_trie_t                       *trie;                  //!< for parsed networks
        fr_ipaddr_t                     *allow;                 //!< allowed networks for dynamic clients
        fr_ipaddr_t                     *deny;                  //!< denied networks for dynamic clients
} proto_dns_udp_t;
 
 
static const conf_parser_t networks_config[] = {
        { FR_CONF_OFFSET_TYPE_FLAGS("allow", FR_TYPE_COMBO_IP_PREFIX , CONF_FLAG_MULTI, proto_dns_udp_t, allow) },
        { FR_CONF_OFFSET_TYPE_FLAGS("deny", FR_TYPE_COMBO_IP_PREFIX , CONF_FLAG_MULTI, proto_dns_udp_t, deny) },
 
        CONF_PARSER_TERMINATOR
};
 
 
static const conf_parser_t udp_listen_config[] = {
        { FR_CONF_OFFSET_TYPE_FLAGS("ipaddr", FR_TYPE_COMBO_IP_ADDR, 0, proto_dns_udp_t, ipaddr) },
        { FR_CONF_OFFSET_TYPE_FLAGS("ipv6addr", FR_TYPE_IPV6_ADDR, 0, proto_dns_udp_t, ipaddr) },
        { FR_CONF_OFFSET_TYPE_FLAGS("ipv4addr", FR_TYPE_IPV4_ADDR, 0, proto_dns_udp_t, ipaddr) },
 
        { FR_CONF_OFFSET("interface", proto_dns_udp_t, interface) },
 
        { FR_CONF_OFFSET("port", proto_dns_udp_t, port), .dflt = "53"  },
        { FR_CONF_OFFSET_IS_SET("recv_buff", FR_TYPE_UINT32, 0, proto_dns_udp_t, recv_buff) },
 
        { FR_CONF_POINTER("networks", 0, CONF_FLAG_SUBSECTION, NULL), .subcs = (void const *) networks_config },
 
        { FR_CONF_OFFSET("max_packet_size", proto_dns_udp_t, max_packet_size), .dflt = "576" } ,
        { FR_CONF_OFFSET("max_attributes", proto_dns_udp_t, max_attributes), .dflt = STRINGIFY(DNS_MAX_ATTRIBUTES) } ,
 
        CONF_PARSER_TERMINATOR
};
 
static fr_dict_t const *dict_dns;
 
extern fr_dict_autoload_t proto_dns_udp_dict[];
fr_dict_autoload_t proto_dns_udp_dict[] = {
        { .out = &dict_dns, .proto = "dns" },
        DICT_AUTOLOAD_TERMINATOR
};
 
static fr_dict_attr_t const *attr_packet_type;
 
extern fr_dict_attr_autoload_t proto_dns_udp_dict_attr[];
fr_dict_attr_autoload_t proto_dns_udp_dict_attr[] = {
        { .out = &attr_packet_type, .name = "Packet-Type", .type = FR_TYPE_UINT32, .dict = &dict_dns},
 
        DICT_AUTOLOAD_TERMINATOR
};
 
static ssize_t mod_read(fr_listen_instance_t *li, void **packet_ctx, fr_time_t *recv_time_p, uint8_t *buffer,
                        size_t buffer_len, size_t *leftover)
{
//      proto_dns_udp_t const           *inst = talloc_get_type_abort_const(li->listen->app_io_instance,
//                                                                  proto_dns_udp_t);
        proto_dns_udp_thread_t          *thread = talloc_get_type_abort(li->thread_instance, proto_dns_udp_thread_t);
        fr_io_address_t                 *address, **address_p;
 
        int                             flags;
        ssize_t                         data_size;
        size_t                          packet_len;
        uint32_t                        xid;
        uint8_t                         opcode;
        fr_dns_packet_t                 *packet;
        fr_dns_decode_fail_t            reason;
 
        *leftover = 0;          /* always for UDP */
 
        /*
         *      Where the addresses should go.  This is a special case
         *      for proto_dns.
         */
        address_p = (fr_io_address_t **)packet_ctx;
        address = *address_p;
 
        /*
         *      Tell udp_recv if we're connected or not.
         */
        flags = UDP_FLAGS_CONNECTED * (thread->connection != NULL);
 
        data_size = udp_recv(thread->sockfd, flags, &address->socket, buffer, buffer_len, recv_time_p);
        if (data_size < 0) {
                RATE_LIMIT_GLOBAL(PERROR, "Read error (%zd)", data_size);
                return data_size;
        }
 
        if ((size_t) data_size < DNS_HDR_LEN) {
                RATE_LIMIT_GLOBAL(WARN, "Insufficient data - ignoring");
                return 0;
        }
 
        packet_len = data_size;
 
        /*
         *      We've seen a server reply to this port, but the giaddr
         *      is *not* our address.  Drop it.
         */
        packet = (fr_dns_packet_t *) buffer;
 
        if (!fr_dns_packet_ok(buffer, packet_len, true, &reason)) {
                RATE_LIMIT_GLOBAL(WARN, "Ignoring invalid DNS packet - %s",
                                  fr_table_str_by_value(fr_dns_reason_fail_table, reason, "unknown"));
                return 0;
        }
 
        /*
         *      check packet code
         */
 
        /*
         *      proto_dns sets the priority
         */
 
        xid = fr_nbo_to_uint16(buffer);
 
        /*
         *      fr_dns_packet_ok() rejects opcodes outside fr_dns_packet_names.
         */
        opcode = packet->opcode;
        if (!fr_cond_assert_msg(opcode < FR_DNS_CODE_MAX, "fr_dns_packet_ok() accepted invalid opcode %u", opcode)) {
                return 0;
        }
 
        /*
         *      Print out what we received.
         */
        DEBUG2("Received %s ID %04x length %d %s", fr_dns_packet_names[opcode], xid,
               (int) packet_len, thread->name);
 
        return packet_len;
}
 
static ssize_t mod_write(fr_listen_instance_t *li, void *packet_ctx, UNUSED fr_time_t request_time, uint8_t *buffer,
                         size_t buffer_len, UNUSED size_t written)
{
//      proto_dns_udp_t const           *inst = talloc_get_type_abort_const(li->listen->app_io_instance,
//                                                                  proto_dns_udp_t);
        proto_dns_udp_thread_t          *thread = talloc_get_type_abort(li->thread_instance, proto_dns_udp_thread_t);
 
        fr_io_track_t                   *track = talloc_get_type_abort(packet_ctx, fr_io_track_t);
        fr_socket_t                     socket;
 
        int                             flags;
        ssize_t                         data_size;
 
        /*
         *      @todo - share a stats interface with the parent?  or
         *      put the stats in the listener, so that proto_dns
         *      can update them, too.. <sigh>
         */
        thread->stats.total_responses++;
 
        flags = UDP_FLAGS_CONNECTED * (thread->connection != NULL);
 
        /*
         *      Send packets to the originator.
         */
        fr_socket_addr_swap(&socket, &track->address->socket);
 
        /*
         *      Figure out which kind of packet we're sending.
         */
        if (!thread->connection) {
                // @todo - figure out where to send the packet
        }
 
        /*
         *      proto_dns takes care of suppressing do-not-respond, etc.
         */
        data_size = udp_send(&socket, flags, buffer, buffer_len);
 
        /*
         *      This socket is dead.  That's an error...
         */
        if (data_size <= 0) return data_size;
 
        return data_size;
}
 
 
static int mod_connection_set(fr_listen_instance_t *li, fr_io_address_t *connection)
{
        proto_dns_udp_thread_t  *thread = talloc_get_type_abort(li->thread_instance, proto_dns_udp_thread_t);
 
        thread->connection = connection;
        return 0;
}
 
 
static void mod_network_get(int *ipproto, bool *dynamic_clients, fr_trie_t const **trie, void *instance)
{
        proto_dns_udp_t         *inst = talloc_get_type_abort(instance, proto_dns_udp_t);
 
        *ipproto = IPPROTO_UDP;
        *dynamic_clients = false;
        *trie = inst->trie;
}
 
 
/** Open a UDP listener for DHCPv6
 *
 */
static int mod_open(fr_listen_instance_t *li)
{
        proto_dns_udp_t const   *inst = talloc_get_type_abort_const(li->listen->app_io_instance, proto_dns_udp_t);
        proto_dns_udp_thread_t  *thread = talloc_get_type_abort(li->thread_instance, proto_dns_udp_thread_t);
 
        int                             sockfd, rcode;
        fr_ipaddr_t                     ipaddr = inst->ipaddr;
        uint16_t                        port = inst->port;
 
        li->fd = sockfd = fr_socket_server_udp(&inst->ipaddr, &port, "domain", true);
        if (sockfd < 0) {
                cf_log_err(li->listen->cs, "Failed opening UDP socket - %s", fr_strerror());
        error:
                return -1;
        }
 
        li->app_io_addr = fr_socket_addr_alloc_inet_src(li, IPPROTO_UDP, 0, &inst->ipaddr, port);
 
        /*
         *      Set SO_REUSEPORT before bind, so that all packets can
         *      listen on the same destination IP address.
         */
        if (1) {
                int on = 1;
 
                if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEPORT, &on, sizeof(on)) < 0) {
                        cf_log_err(li->listen->cs, "Failed to set socket 'reuseport' - %s", fr_syserror(errno));
                        close(sockfd);
                        return -1;
                }
        }
 
        /*
         *      SUID up is really only needed if interface is set, OR port <1024.
         */
        rad_suid_up();
        rcode = fr_socket_bind(sockfd, inst->interface, &ipaddr, &port);
        rad_suid_down();
        if (rcode < 0) {
                close(sockfd);
                cf_log_err(li->listen->cs, "Failed binding to socket - %s", fr_strerror());
                cf_log_err(li->listen->cs, DOC_ROOT_REF(troubleshooting/network/bind));
                goto error;
        }
 
        thread->sockfd = sockfd;
 
        fr_assert((cf_parent(inst->cs) != NULL) && (cf_parent(cf_parent(inst->cs)) != NULL));   /* listen { ... } */
 
        thread->name = fr_app_io_socket_name(thread, &proto_dns_udp,
                                             NULL, 0,
                                             &inst->ipaddr, inst->port,
                                             inst->interface);
        return 0;
}
 
 
/** Set the file descriptor for this socket.
 *
 */
static int mod_fd_set(fr_listen_instance_t *li, int fd)
{
        proto_dns_udp_t const   *inst = talloc_get_type_abort_const(li->listen->app_io_instance, proto_dns_udp_t);
        proto_dns_udp_thread_t  *thread = talloc_get_type_abort(li->thread_instance, proto_dns_udp_thread_t);
 
        thread->sockfd = fd;
 
        thread->name = fr_app_io_socket_name(thread, &proto_dns_udp,
                                             &thread->connection->socket.inet.src_ipaddr, thread->connection->socket.inet.src_port,
                                             &inst->ipaddr, inst->port,
                                             inst->interface);
 
        return 0;
}
 
 
static char const *mod_name(fr_listen_instance_t *li)
{
        proto_dns_udp_thread_t  *thread = talloc_get_type_abort(li->thread_instance, proto_dns_udp_thread_t);
 
        return thread->name;
}
 
 
static int mod_instantiate(module_inst_ctx_t const *mctx)
{
        proto_dns_udp_t         *inst = talloc_get_type_abort(mctx->mi->data, proto_dns_udp_t);
        CONF_SECTION            *conf = mctx->mi->conf;
        size_t                  num;
        CONF_SECTION            *server_cs;
        fr_client_t             *client;
 
        inst->cs = conf;
 
        /*
         *      Complain if no "ipaddr" is set.
         */
        if (inst->ipaddr.af == AF_UNSPEC) {
                if (!inst->interface) {
                        cf_log_err(conf, "No 'ipaddr' was specified in the 'udp' section");
                        return -1;
                }
 
                /*
                 *      If there's a named interface, maybe we can
                 *      find a link-local address for it.  If so, just
                 *      use that.
                 */
                if (inst->interface &&
                    (fr_interface_to_ipaddr(inst->interface, &inst->ipaddr, AF_INET, true) < 0)) {
                        cf_log_err(conf, "No 'ipaddr' specified, and we cannot determine one for interface '%s'",
                                   inst->interface);
                                return -1;
                }
        }
 
        if (inst->recv_buff_is_set) {
                FR_INTEGER_BOUND_CHECK("recv_buff", inst->recv_buff, >=, 32);
                FR_INTEGER_BOUND_CHECK("recv_buff", inst->recv_buff, <=, INT_MAX);
        }
 
        FR_INTEGER_BOUND_CHECK("max_packet_size", inst->max_packet_size, >=, 64);
        FR_INTEGER_BOUND_CHECK("max_packet_size", inst->max_packet_size, <=, 65536);
 
        /*
         *      Parse and create the trie for dynamic clients, even if
         *      there's no dynamic clients.
         */
        num = talloc_array_length(inst->allow);
        if (num) {
                inst->trie = fr_master_io_network(inst, inst->ipaddr.af, inst->allow, inst->deny);
                if (!inst->trie) {
                        cf_log_perr(conf, "Failed creating list of networks");
                        return -1;
                }
        }
 
        server_cs = cf_section_find_parent(inst->cs, "server", CF_IDENT_ANY);
        fr_assert(server_cs != NULL);
 
        /*
         *      Look up local clients, if they exist.
         *
         *      @todo - ensure that we only parse clients which are
         *      for IPPROTO_UDP, and don't require a "secret".
         */
        if (cf_section_find_next(server_cs, NULL, "client", CF_IDENT_ANY)) {
                inst->clients = client_list_parse_section(server_cs, IPPROTO_UDP, false);
                if (!inst->clients) {
                        cf_log_err(conf, "Failed creating local clients");
                        return -1;
                }
        }
 
        /*
         *      Create a fake client.
         */
        client = inst->default_client = talloc_zero(inst, fr_client_t);
        if (!inst->default_client) return -1;
 
        client->ipaddr = (fr_ipaddr_t ) {
                .af = AF_INET6,
        };
 
        client->src_ipaddr = client->ipaddr;
 
        client->longname = client->shortname = client->secret = talloc_strdup(client, "default");
        client->nas_type = talloc_strdup(client, "other");
 
        return 0;
}
 
static fr_client_t *mod_client_find(fr_listen_instance_t *li, fr_ipaddr_t const *ipaddr, int ipproto)
{
        proto_dns_udp_t const *inst = talloc_get_type_abort_const(li->listen->app_io_instance, proto_dns_udp_t);
 
        /*
         *      Prefer local clients.
         */
        if (inst->clients) {
                fr_client_t *client;
 
                client = client_find(inst->clients, ipaddr, ipproto);
                if (client) return client;
        }
 
        return inst->default_client;
}
 
fr_app_io_t proto_dns_udp = {
        .common = {
                .magic                  = MODULE_MAGIC_INIT,
                .name                   = "dns_udp",
                .config                 = udp_listen_config,
                .inst_size              = sizeof(proto_dns_udp_t),
                .thread_inst_size       = sizeof(proto_dns_udp_thread_t),
                .instantiate            = mod_instantiate
        },
        .default_message_size   = 576,
        .track_duplicates       = false,
 
        .open                   = mod_open,
        .read                   = mod_read,
        .write                  = mod_write,
        .fd_set                 = mod_fd_set,
        .connection_set         = mod_connection_set,
        .network_get            = mod_network_get,
        .client_find            = mod_client_find,
        .get_name               = mod_name,
};