proto_tacacs_tcp.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: 4493e0bfd6060295c1f6b336cd9d395d93311d17 $
 * @file proto_tacacs_tcp.c
 * @brief TACACS+ handler for TCP.
 * @author Jorge Pereira <jpereira@freeradius.org>
 *
 * @copyright 2020 The FreeRADIUS server project.
 * @copyright 2020 Network RADIUS SAS (legal@networkradius.com)
 */
 
#include <netdb.h>
#include <freeradius-devel/server/protocol.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 "proto_tacacs.h"
 
extern fr_app_io_t proto_tacacs_tcp;
 
#define TACACS_MAX_ATTRIBUTES 256
 
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_tacacs_tcp_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.
        char const                      *port_name;             //!< Name of the port for getservent().
 
        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 recv_buff
        bool                            dynamic_clients;        //!< whether we have dynamic clients
 
        fr_client_list_t                *clients;               //!< local clients
 
        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_tacacs_tcp_t;
 
static const conf_parser_t networks_config[] = {
        { FR_CONF_OFFSET_TYPE_FLAGS("allow", FR_TYPE_COMBO_IP_PREFIX , CONF_FLAG_MULTI, proto_tacacs_tcp_t, allow) },
        { FR_CONF_OFFSET_TYPE_FLAGS("deny", FR_TYPE_COMBO_IP_PREFIX , CONF_FLAG_MULTI, proto_tacacs_tcp_t, deny) },
 
        CONF_PARSER_TERMINATOR
};
 
static const conf_parser_t tcp_listen_config[] = {
        { FR_CONF_OFFSET_TYPE_FLAGS("ipaddr", FR_TYPE_COMBO_IP_ADDR, 0, proto_tacacs_tcp_t, ipaddr) },
        { FR_CONF_OFFSET_TYPE_FLAGS("ipv4addr", FR_TYPE_IPV4_ADDR, 0, proto_tacacs_tcp_t, ipaddr) },
        { FR_CONF_OFFSET_TYPE_FLAGS("ipv6addr", FR_TYPE_IPV6_ADDR, 0, proto_tacacs_tcp_t, ipaddr) },
 
        { FR_CONF_OFFSET("interface", proto_tacacs_tcp_t, interface) },
        { FR_CONF_OFFSET("port_name", proto_tacacs_tcp_t, port_name) },
 
        { FR_CONF_OFFSET("port", proto_tacacs_tcp_t, port), .dflt = "49" },
        { FR_CONF_OFFSET_IS_SET("recv_buff", FR_TYPE_UINT32, 0, proto_tacacs_tcp_t, recv_buff) },
 
        { FR_CONF_OFFSET("dynamic_clients", proto_tacacs_tcp_t, dynamic_clients) } ,
        { FR_CONF_POINTER("networks", 0, CONF_FLAG_SUBSECTION, NULL), .subcs = (void const *) networks_config },
 
        { FR_CONF_OFFSET("max_packet_size", proto_tacacs_tcp_t, max_packet_size), .dflt = "4096" } ,
        { FR_CONF_OFFSET("max_attributes", proto_tacacs_tcp_t, max_attributes), .dflt = STRINGIFY(TACACS_MAX_ATTRIBUTES) } ,
 
        CONF_PARSER_TERMINATOR
};
 
static const char *packet_name[] = {
        [FR_TAC_PLUS_AUTHEN] = "Authentication",
        [FR_TAC_PLUS_AUTHOR] = "Authorization",
        [FR_TAC_PLUS_ACCT] = "Accounting",
};
 
/** Read TACACS data from a TCP connection
 *
 * @param[in] li                representing a client connection.
 * @param[in] packet_ctx        UNUSED.
 * @param[out] recv_time_p      When we read the packet.
 *                              For some protocols we get this for free (but not here).
 * @param[out] buffer           to read into.
 * @param[in] buffer_len        Maximum length of the buffer.
 * @param[in,out] leftover      If the previous read didn't yield a complete packet
 *                              we will have written how many bytes we read in leftover
 *                              and returned 0.  On the next call, we use the
 *                              value of leftover to offset the position we start
 *                              writing into the buffer.
 *                              *leftover must be subtracted from buffer_len when
 *                              calculating free space in the buffer.
 * @return
 *      - >0 when a packet was read successfully.
 *      - 0 when we read a partial packet.
 *      - <0 on error (socket should be closed).
 */
static ssize_t mod_read(fr_listen_t *li, UNUSED void **packet_ctx, fr_time_t *recv_time_p,
                        uint8_t *buffer, size_t buffer_len, size_t *leftover)
{
        proto_tacacs_tcp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_tacacs_tcp_thread_t);
        ssize_t                         data_size, packet_len;
        size_t                          in_buffer;
 
        /*
         *      We may have read multiple packets in the previous read.  In which case the buffer may already
         *      have packets remaining.  In that case, we can return packets directly from the buffer, and
         *      skip the read().
         */
        if (*leftover >= FR_HEADER_LENGTH) {
                packet_len = fr_tacacs_length(buffer, *leftover);
                if (packet_len < 0) goto invalid;
 
                if (packet_len <= ((ssize_t) *leftover)) {
                        data_size = 0;
                        goto have_packet;
                }
 
                /*
                 *      Else we don't have a full packet, try to read more data from the network.
                 */
        }
 
        /*
         *      Read data into the buffer.
         */
        data_size = read(thread->sockfd, buffer + (*leftover), buffer_len - (*leftover));
        if (data_size < 0) {
                switch (errno) {
#if defined(EWOULDBLOCK) && (EWOULDBLOCK != EAGAIN)
                case EWOULDBLOCK:
#endif
                case EAGAIN:
                        /*
                         *      We didn't read any data leave the buffers alone.
                         *
                         *      i.e. if we had a partial packet in the buffer and we didn't read any data,
                         *      then the partial packet is still left in the buffer.
                         */
                        return 0;
 
                default:
                        break;
                }
 
                ERROR("proto_tacacs_tcp got read error (%zd) - %s", data_size, fr_syserror(errno));
                return data_size;
        }
 
        /*
         *      Note that we return ERROR for all bad packets, as
         *      there's no point in reading TACACS+ packets from a TCP
         *      connection which isn't sending us TACACS+ packets.
         */
 
        /*
         *      TCP read of zero means the socket is dead.
         */
        if (!data_size) {
                DEBUG2("proto_tacacs_tcp - other side closed the socket.");
                return -1;
        }
 
have_packet:
        /*
         *      Represents all the data we've read since we last
         *      decoded a complete packet.
         */
        in_buffer = *leftover + data_size;
 
        /*
         *      Figure out how big the complete TACACS packet should be.
         *      If we don't have enough data it'll likely come
         *      through in the next fragment.
         */
        packet_len = fr_tacacs_length(buffer, in_buffer);
        if (packet_len < 0) {
        invalid:
                PERROR("Invalid TACACS packet");
                return -1;      /* Malformed, close the socket */
        }
 
        /*
         *      We don't have a complete TACACS+ packet.  Tell the
         *      caller that we need to read more, but record
         *      how much we read in leftover.
         */
        if (in_buffer < (size_t) packet_len) {
                DEBUG3("proto_tacacs_tcp - Received packet fragment of %zu bytes (%zu bytes now pending)",
                       packet_len, *leftover);
                *leftover = in_buffer;
                return 0;
        }
 
        /*
         *      We've read at least one packet.  Tell the caller that
         *      there's more data available, and return only one packet.
         */
        *leftover = in_buffer - packet_len;
 
        *recv_time_p = fr_time();
        thread->stats.total_requests++;
 
        /*
         *      proto_tacacs sets the priority
         */
 
        /*
         *      Print out what we received.
         */
        FR_PROTO_HEX_DUMP(buffer, packet_len, "tacacs_tcp_recv");
 
        if (DEBUG_ENABLED2) {
                char bogus_type[4];
                char const *type;
 
                if (buffer[1] && buffer[1] <= FR_TAC_PLUS_ACCT) type = packet_name[buffer[1]];
                else {
                        snprintf(bogus_type, sizeof(bogus_type), "%d", buffer[1]);
                        type = bogus_type;
                }
                DEBUG2("proto_tacacs_tcp - Received %s seq_no %d length %zd %s",
                       type, buffer[2],
                       packet_len, thread->name);
        }
 
        return packet_len;
}
 
static ssize_t mod_write(fr_listen_t *li, UNUSED void *packet_ctx, UNUSED fr_time_t request_time,
                         uint8_t *buffer, size_t buffer_len, size_t written)
{
        proto_tacacs_tcp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_tacacs_tcp_thread_t);
        ssize_t                         data_size;
 
        /*
         *      We only write TACACS packets.
         *
         *      @todo - if buffer_len ==1, it means "do not respond".
         *      Which should be suppressed somewhere.  Maybe here...
         */
        fr_assert(buffer_len >= sizeof(fr_tacacs_packet_hdr_t));
        fr_assert(written < buffer_len);
 
        /*
         *      @todo - share a stats interface with the parent?  or
         *      put the stats in the listener, so that proto_tacacs
         *      can update them, too.. <sigh>
         */
        if (written == 0) {
                thread->stats.total_responses++;
        }
 
        /*
         *      Only write replies if they're TACACS+ packets.
         *      sometimes we want to NOT send a reply...
         */
        data_size = write(thread->sockfd, buffer + written, buffer_len - written);
        if (data_size <= 0) return data_size;
 
        /*
         *      If we're supposed to close the socket, then go do that.
         */
        if ((data_size + written) == buffer_len) {
                fr_tacacs_packet_t const *pkt = (fr_tacacs_packet_t const *) buffer;
 
                switch (pkt->hdr.type) {
                case FR_TAC_PLUS_AUTHEN:
                        if (pkt->authen_reply.status == FR_TAC_PLUS_AUTHEN_STATUS_ERROR) goto close_it;
                        break;
 
 
                case FR_TAC_PLUS_AUTHOR:
                        if (pkt->author_reply.status == FR_TAC_PLUS_AUTHOR_STATUS_ERROR) {
                        close_it:
                                DEBUG("Closing connection due to unrecoverable server error response");
                                return 0;
                        }
                        break;
 
                default:
                        break;
                }
        }
 
        /*
         *      Return the packet we wrote, plus any bytes previously
         *      left over from previous packets.
         */
        return data_size + written;
}
 
static int mod_connection_set(fr_listen_t *li, fr_io_address_t *connection)
{
        proto_tacacs_tcp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_tacacs_tcp_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_tacacs_tcp_t *inst = talloc_get_type_abort(instance, proto_tacacs_tcp_t);
 
        *ipproto = IPPROTO_TCP;
        *dynamic_clients = inst->dynamic_clients;
        *trie = inst->trie;
}
 
/** Open a TCP listener for TACACS+
 *
 */
static int mod_open(fr_listen_t *li)
{
        proto_tacacs_tcp_t const        *inst = talloc_get_type_abort_const(li->app_io_instance, proto_tacacs_tcp_t);
        proto_tacacs_tcp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_tacacs_tcp_thread_t);
 
        int                             sockfd;
        fr_ipaddr_t                     ipaddr = inst->ipaddr;
        uint16_t                        port = inst->port;
 
        fr_assert(!thread->connection);
 
        li->fd = sockfd = fr_socket_server_tcp(&inst->ipaddr, &port, inst->port_name, true);
        if (sockfd < 0) {
                PERROR("Failed opening TCP socket");
        error:
                return -1;
        }
 
        (void) fr_nonblock(sockfd);
 
        if (fr_socket_bind(sockfd, inst->interface, &ipaddr, &port) < 0) {
                close(sockfd);
                PERROR("Failed binding socket");
                goto error;
        }
 
        if (listen(sockfd, 8) < 0) {
                close(sockfd);
                PERROR("Failed listening on socket");
                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_tacacs_tcp,
                                             NULL, 0,
                                             &inst->ipaddr, inst->port,
                                             inst->interface);
 
        return 0;
}
 
 
/** Set the file descriptor for this socket.
 */
static int mod_fd_set(fr_listen_t *li, int fd)
{
        proto_tacacs_tcp_t const  *inst = talloc_get_type_abort_const(li->app_io_instance, proto_tacacs_tcp_t);
        proto_tacacs_tcp_thread_t *thread = talloc_get_type_abort(li->thread_instance, proto_tacacs_tcp_thread_t);
 
        thread->sockfd = fd;
 
        thread->name = fr_app_io_socket_name(thread, &proto_tacacs_tcp,
                                             &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_t *li)
{
        proto_tacacs_tcp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_tacacs_tcp_thread_t);
 
        return thread->name;
}
 
static int mod_instantiate(module_inst_ctx_t const *mctx)
{
        proto_tacacs_tcp_t      *inst = talloc_get_type_abort(mctx->mi->data, proto_tacacs_tcp_t);
        CONF_SECTION            *conf = mctx->mi->conf;
        size_t                  num;
        CONF_ITEM               *ci;
        CONF_SECTION            *server_cs;
 
        inst->cs = conf;
 
        /*
         *      Complain if no "ipaddr" is set.
         */
        if (inst->ipaddr.af == AF_UNSPEC) {
                cf_log_err(conf, "No 'ipaddr' was specified in the 'tcp' section");
                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, >=, 20);
        FR_INTEGER_BOUND_CHECK("max_packet_size", inst->max_packet_size, <=, 65536);
 
        if (!inst->port) {
                struct servent *s;
 
                if (!inst->port_name) {
                        cf_log_err(conf, "No 'port' was specified in the 'tcp' section");
                        return -1;
                }
 
                s = getservbyname(inst->port_name, "tcp");
                if (!s) {
                        cf_log_err(conf, "Unknown value for 'port_name = %s", inst->port_name);
                        return -1;
                }
 
                inst->port = ntohl(s->s_port);
        }
 
        /*
         *      Parse and create the trie for dynamic clients, even if
         *      there's no dynamic clients.
         */
        num = talloc_array_length(inst->allow);
        if (!num) {
                if (inst->dynamic_clients) {
                        cf_log_err(conf, "The 'allow' subsection MUST contain at least one 'network' entry when 'dynamic_clients = true'.");
                        return -1;
                }
        } else {
                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;
                }
        }
 
        ci = cf_section_to_item(mctx->mi->parent->conf); /* listen { ... } */
        fr_assert(ci != NULL);
        ci = cf_parent(ci);
        fr_assert(ci != NULL);
 
        server_cs = cf_item_to_section(ci);
 
        /*
         *      Look up local clients, if they exist.
         *
         *      @todo - ensure that we only parse clients which are
         *      for IPPROTO_TCP, and require a "secret".
         */
        if (cf_section_find_next(server_cs, NULL, "client", CF_IDENT_ANY)) {
                inst->clients = client_list_parse_section(server_cs, IPPROTO_TCP, false);
                if (!inst->clients) {
                        cf_log_err(conf, "Failed creating local clients");
                        return -1;
                }
        }
 
        return 0;
}
 
static fr_client_t *mod_client_find(fr_listen_t *li, fr_ipaddr_t const *ipaddr, int ipproto)
{
        proto_tacacs_tcp_t const        *inst = talloc_get_type_abort_const(li->app_io_instance, proto_tacacs_tcp_t);
 
        /*
         *      Prefer local clients.
         */
        if (inst->clients) {
                fr_client_t *client;
 
                client = client_find(inst->clients, ipaddr, ipproto);
                if (client) return client;
        }
 
        return client_find(NULL, ipaddr, ipproto);
}
 
fr_app_io_t proto_tacacs_tcp = {
        .common = {
                .magic                  = MODULE_MAGIC_INIT,
                .name                   = "tacacs_tcp",
                .config                 = tcp_listen_config,
                .inst_size              = sizeof(proto_tacacs_tcp_t),
                .thread_inst_size       = sizeof(proto_tacacs_tcp_thread_t),
                .instantiate            = mod_instantiate,
        },
        .default_message_size   = 4096,
        .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,
};