base.c

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/*
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   This library 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
 *   Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * $Id: 1ae2e63121095920132e006e3fe93da6b7d77768 $
 *
 * @file protocols/arp/base.c
 * @brief Functions to send/receive ARP packets.
 *
 * @copyright 2020 Network RADIUS SAS <legal@networkradius.com?
 */
 
RCSID("$Id: 1ae2e63121095920132e006e3fe93da6b7d77768 $")
 
#include <freeradius-devel/util/net.h>
#include <freeradius-devel/util/struct.h>
#include <freeradius-devel/util/syserror.h>
#include <freeradius-devel/io/test_point.h>
#include "attrs.h"
 
#ifdef HAVE_LINUX_IF_PACKET_H
#  include <linux/if_packet.h>
#  include <linux/if_ether.h>
#endif
 
#include <net/if_arp.h>
 
static uint32_t instance_count = 0;
 
fr_dict_t const *dict_arp;
 
extern fr_dict_autoload_t libfreeradius_arp_dict[];
fr_dict_autoload_t libfreeradius_arp_dict[] = {
        { .out = &dict_arp, .proto = "arp" },
        { NULL }
};
 
fr_dict_attr_t const *attr_arp_packet;
 
extern fr_dict_attr_autoload_t libfreeradius_arp_dict_attr[];
fr_dict_attr_autoload_t libfreeradius_arp_dict_attr[] = {
        { .out = &attr_arp_packet, .name = "arp", .type = FR_TYPE_STRUCT, .dict = &dict_arp },
        { NULL }
};
 
 
/*
 *      grep VALUE share/dictionary/arp/dictionary.rfc826  | grep Op | awk '{print "[" $4 "] = \"" $3 "\","}'
 */
char const *fr_arp_packet_codes[FR_ARP_CODE_MAX] = {
        [1] = "Request",
        [2] = "Reply",
        [3] = "Reverse-Request",
        [4] = "Reverse-Reply",
#if 0
        [5] = "DRARP-Request",
        [6] = "DRARP-Reply",
        [7] = "DRARP-Error",
        [8] = "InARP-Request",
        [9] = "InARP-Reply",
        [10] = "ARP-NAK",
        [11] = "MARS-Request",
        [12] = "MARS-Multi",
        [13] = "MARS-MServ",
        [14] = "MARS-Join",
        [15] = "MARS-Leave",
        [16] = "MARS-NAK",
        [17] = "MARS-Unserv",
        [18] = "MARS-SJoin",
        [19] = "MARS-SLeave",
        [20] = "MARS-Grouplist-Request",
        [21] = "MARS-Grouplist-Reply",
        [22] = "MARS-Redirect-MAP",
        [23] = "MAPOS-UNARP",
        [24] = "OP_EXP1",
        [25] = "OP_EXP2",
#endif
};
 
static uint8_t const zeros[6] = { 0 };
 
#ifdef SIOCSARP
/** Forcibly add an ARP entry so we can send unicast packets to hosts that don't have IP addresses yet
 *
 * @param[in] fd        to add arp entry on.
 * @param[in] interface to add arp entry on.
 * @param[in] ipaddr    to insert into ARP table.
 * @param[in] macaddr   to insert into ARP table.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int fr_arp_entry_add(int fd, char const *interface, uint8_t ipaddr[static 4], uint8_t macaddr[static 6])
{
        struct sockaddr_in *sin;
        struct arpreq req;
 
        if (!interface) {
                fr_strerror_const("No interface specified.  Cannot update ARP table");
                return -1;
        }
 
        memset(&req, 0, sizeof(req));
        sin = (struct sockaddr_in *) &req.arp_pa;
        sin->sin_family = AF_INET;
        memcpy(&sin->sin_addr.s_addr, ipaddr, 4);
 
        strlcpy(req.arp_dev, interface, sizeof(req.arp_dev));
 
        memcpy(&req.arp_ha.sa_data, macaddr, 6);
 
        req.arp_flags = ATF_COM;
        if (ioctl(fd, SIOCSARP, &req) < 0) {
                fr_strerror_printf("Failed to add entry in ARP cache: %s (%d)", fr_syserror(errno), errno);
                return -1;
        }
 
        return 0;
}
#else
int fr_arp_entry_add(UNUSED int fd, UNUSED char const *interface,
                     UNUSED uint8_t ipaddr[static 4], UNUSED uint8_t macaddr[static 6])
{
        fr_strerror_const("Adding ARP entry is unsupported on this system");
        return -1;
}
#endif
 
 
/** Encode VPS into a raw ARP packet.
 *
 */
ssize_t fr_arp_encode(fr_dbuff_t *dbuff, uint8_t const *original, fr_pair_list_t *vps)
{
        ssize_t                 slen;
        fr_pair_t               *vp;
        fr_arp_packet_t         *arp;
        fr_dcursor_t            cursor;
        fr_da_stack_t           da_stack;
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
 
        if (fr_pair_list_empty(vps)) {
                fr_strerror_const("Cannot encode empty packet");
                return -1;
        }
 
        /*
         *      Get a cursor over the ARP attributes.
         */
        vp = fr_pair_dcursor_by_ancestor_init(&cursor, vps, attr_arp_packet);
 
        /*
         *      For simplicity, we allow the caller to omit things
         *      that they don't care about.
         */
        if (!vp) {
                fr_strerror_const("No ARP attributes in the attribute list");
                return -1;
        }
 
        fr_proto_da_stack_build(&da_stack, attr_arp_packet);
        FR_PROTO_STACK_PRINT(&da_stack, 0);
 
        /*
         *      Call the struct encoder to do the actual work.
         */
        slen = fr_struct_to_network(&work_dbuff, &da_stack, 0, &cursor, NULL, NULL, NULL);
        if (slen <= 0) return slen;
 
        if (slen != FR_ARP_PACKET_SIZE) return slen;
 
        /*
         *      Hard-code fields which can be omitted.
         */
        arp = (fr_arp_packet_t *)fr_dbuff_start(&work_dbuff);
 
        if ((arp->htype[0] == 0) && (arp->htype[1] == 0)) arp->htype[1] = FR_HARDWARE_FORMAT_VALUE_ETHERNET;
        if ((arp->ptype[0] == 0) && (arp->ptype[1] == 0)) arp->ptype[0] = (FR_PROTOCOL_FORMAT_VALUE_IPV4 >> 8); /* 0x0800 */
        if (arp->hlen == 0) arp->hlen = 6;
        if (arp->plen == 0) arp->plen = 4;
 
        /*
         *      The reply generally swaps Sender / Target addresses,
         *      BUT fills out the Sender-Hardware-Address with the
         *      queried MAC address.  Ensure that the admin doesn't
         *      have to fill out all of the fields.
         */
        if (original) {
                fr_arp_packet_t const *our_original = (fr_arp_packet_t const *) original;
 
#define COPY(_a, _b) do { \
        if (memcmp(arp->_a, zeros, sizeof(arp->_a)) == 0) { \
                memcpy(arp->_a, our_original->_b, sizeof(arp->_a)); \
        } \
  } while (0)
 
                COPY(spa, tpa);         /* answer is about the asked-for target */
                COPY(tha, sha);         /* answer is sent to the requestor hardware address */
                COPY(tpa, spa);         /* answer is sent to the requestor protocol address */
        }
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** Decode a raw ARP packet into VPs
 *
 */
ssize_t fr_arp_decode(TALLOC_CTX *ctx, fr_pair_list_t *out, uint8_t const *packet, size_t packet_len)
{
        fr_arp_packet_t const *arp;
 
        if (packet_len < FR_ARP_PACKET_SIZE) {
                fr_strerror_printf("Packet is too small (%d) to be ARP", (int) packet_len);
                return -1;
        }
 
        /*
         *      Check that the fields have the desired values.
         */
        arp = (fr_arp_packet_t const *) packet;
        if ((arp->htype[0] != 0) || (arp->htype[1] != 1)) {
                fr_strerror_const("Hardware-Format != Ethernet");
                return -1;
        }
 
        if ((arp->ptype[0] != 8) || (arp->ptype[1] != 0)) {
                fr_strerror_const("Protocol-Format != IPv4");
                return -1;
        }
 
        if (arp->hlen != 6) {
                fr_strerror_const("Hardware-Length != 6");
                return -1;
        }
 
        if (arp->plen != 4) {
                fr_strerror_const("Protocol-Length != 4");
                return -1;
        }
 
        /*
         *      If the packet is too long, we discard any extra data.
         */
        return fr_struct_from_network(ctx, out, attr_arp_packet, packet, FR_ARP_PACKET_SIZE, true,
                                      NULL, NULL, NULL);
}
 
int fr_arp_global_init(void)
{
        if (instance_count > 0) {
                instance_count++;
                return 0;
        }
 
        instance_count++;
 
        if (fr_dict_autoload(libfreeradius_arp_dict) < 0) {
        fail:
                instance_count--;
                return -1;
        }
 
        if (fr_dict_attr_autoload(libfreeradius_arp_dict_attr) < 0) {
                fr_dict_autofree(libfreeradius_arp_dict);
                goto fail;
        }
 
        return 0;
}
 
void fr_arp_global_free(void)
{
        fr_assert(instance_count > 0);
 
        if (--instance_count > 0) return;
 
        fr_dict_autofree(libfreeradius_arp_dict);
}
 
extern fr_dict_protocol_t libfreeradius_arp_dict_protocol;
fr_dict_protocol_t libfreeradius_arp_dict_protocol = {
        .name = "arp",
        .default_type_size = 4,
        .default_type_length = 0,
 
        .init = fr_arp_global_init,
        .free = fr_arp_global_free,
};
 
 
typedef struct {
        bool            tmp;
} fr_arp_ctx_t;
 
static int encode_test_ctx(void **out, TALLOC_CTX *ctx)
{
        fr_arp_ctx_t *test_ctx;
 
        fr_assert(instance_count > 0);
 
        test_ctx = talloc_zero(ctx, fr_arp_ctx_t);
        if (!test_ctx) return -1;
 
        *out = test_ctx;
 
        return 0;
}
 
 
/*
 *      Test points for protocol encode / decode
 *
 *      Because ARP has no TLVs, we don't have test points for pair
 *      encode / decode.
 */
static ssize_t fr_arp_encode_proto(UNUSED TALLOC_CTX *ctx, fr_pair_list_t *vps, uint8_t *data, size_t data_len, UNUSED void *proto_ctx)
{
        return fr_arp_encode(&FR_DBUFF_TMP(data, data_len), NULL, vps);
}
 
extern fr_test_point_proto_encode_t arp_tp_encode_proto;
fr_test_point_proto_encode_t arp_tp_encode_proto = {
        .test_ctx       = encode_test_ctx,
        .func           = fr_arp_encode_proto
};
 
static ssize_t fr_arp_decode_proto(TALLOC_CTX *ctx, fr_pair_list_t *out,
                                   uint8_t const *data, size_t data_len, UNUSED void *proto_ctx)
{
        return fr_arp_decode(ctx, out, data, data_len);
}
 
extern fr_test_point_proto_decode_t arp_tp_decode_proto;
fr_test_point_proto_decode_t arp_tp_decode_proto = {
        .test_ctx       = encode_test_ctx,
        .func           = fr_arp_decode_proto
};