decode.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: b52d225a31da6f9bb8b11c204a07848fe985f774 $
 *
 * @file protocols/dhcpv6/decode.c
 * @brief Functions to decode DHCP options.
 *
 * @author Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 *
 * @copyright 2018 The FreeRADIUS server project
 * @copyright 2018 NetworkRADIUS SARL (legal@networkradius.com)
 */
#include <stdint.h>
#include <stddef.h>
 
#include <freeradius-devel/io/test_point.h>
#include <freeradius-devel/util/dns.h>
#include <freeradius-devel/util/proto.h>
#include <freeradius-devel/util/struct.h>
 
#include "dhcpv6.h"
#include "attrs.h"
 
static ssize_t decode_option(TALLOC_CTX *ctx, fr_pair_list_t *out,
                             fr_dict_attr_t const *parent,
                             uint8_t const *data, size_t const data_len, void *decode_ctx);
 
static ssize_t decode_tlv_trampoline(TALLOC_CTX *ctx, fr_pair_list_t *out,
                                     fr_dict_attr_t const *parent,
                                     uint8_t const *data, size_t const data_len, void *decode_ctx)
{
        return fr_pair_tlvs_from_network(ctx, out, parent, data, data_len, decode_ctx, decode_option, NULL, true);
}
 
static ssize_t decode_value(TALLOC_CTX *ctx, fr_pair_list_t *out,
                            fr_dict_attr_t const *parent,
                            uint8_t const *data, size_t const data_len, void *decode_ctx);
 
/** Handle arrays of DNS labels for fr_struct_from_network()
 *
 */
static ssize_t decode_value_trampoline(TALLOC_CTX *ctx, fr_pair_list_t *out,
                                       fr_dict_attr_t const *parent,
                                       uint8_t const *data, size_t const data_len, void *decode_ctx)
{
        if ((parent->type == FR_TYPE_STRING) && fr_dhcpv6_flag_any_dns_label(parent)) {
                return fr_pair_dns_labels_from_network(ctx, out, parent, data, data, data_len, NULL, false);
        }
 
        return decode_value(ctx, out, parent, data, data_len, decode_ctx);
}
 
 
static ssize_t decode_value(TALLOC_CTX *ctx, fr_pair_list_t *out,
                            fr_dict_attr_t const *parent,
                            uint8_t const *data, size_t const data_len, void *decode_ctx)
{
        ssize_t                 slen;
        fr_pair_t               *vp = NULL;
        uint8_t                 prefix_len;
        fr_dict_attr_t const    *ref;
 
        FR_PROTO_HEX_DUMP(data, data_len, "decode_value");
 
        switch (parent->type) {
        /*
         *      Address MAY be shorter than 16 bytes.
         */
        case FR_TYPE_IPV6_PREFIX:
                if (data_len == 0) {
                raw:
                        return fr_pair_raw_from_network(ctx, out, parent, data, data_len);
 
                }
 
                /*
                 *      Structs used fixed length IPv6 addressews.
                 */
                if (parent->parent->type == FR_TYPE_STRUCT) {
                        if (data_len != (1 + sizeof(vp->vp_ipv6addr))) {
                                goto raw;
                        }
 
                        vp = fr_pair_afrom_da(ctx, parent);
                        if (!vp) return PAIR_DECODE_OOM;
 
                        vp->vp_ip.af = AF_INET6;
                        vp->vp_ip.scope_id = 0;
                        vp->vp_ip.prefix = data[0];
                        memcpy(&vp->vp_ipv6addr, data + 1, sizeof(vp->vp_ipv6addr));
                        slen = 1 + sizeof(vp->vp_ipv6addr);
                        break;
                }
 
                /*
                 *      No address, the prefix length MUST be zero.
                 */
                if (data_len == 1) {
                        if (data[0] != 0) goto raw;
 
                        vp = fr_pair_afrom_da(ctx, parent);
                        if (!vp) return PAIR_DECODE_OOM;
 
                        vp->vp_ip.af = AF_INET6;
                        slen = 1;
                        break;
                }
 
                prefix_len = data[0];
 
                /*
                 *      If we have a /64 prefix but only 7 bytes of
                 *      address, that's an error.
                 */
                slen = fr_bytes_from_bits(prefix_len);
                if ((size_t) slen > (data_len - 1)) {
                        goto raw;
                }
 
                vp = fr_pair_afrom_da(ctx, parent);
                if (!vp) return PAIR_DECODE_OOM;
 
                vp->vp_ip.af = AF_INET6;
                vp->vp_ip.prefix = prefix_len;
                memcpy(&vp->vp_ipv6addr, data + 1, slen);
 
                slen++;
                break;
 
        /*
         *      A bool is encoded as an empty option if it's
         *      true.  A bool is omitted entirely if it's
         *      false.
         */
        case FR_TYPE_BOOL:
                if (data_len != 0) goto raw;
                vp = fr_pair_afrom_da(ctx, parent);
                if (!vp) return PAIR_DECODE_OOM;
                vp->vp_bool = true;
                slen = 0;
                break;
 
        /*
         *      A standard 32bit integer, but unlike normal UNIX timestamps
         *      starts from the 1st of January 2000.
         *
         *      In the encoder we subtract 30 years to any values, so
         *      here we need to add that to the time here.
         */
        case FR_TYPE_DATE:
                vp = fr_pair_afrom_da(ctx, parent);
                if (!vp) return PAIR_DECODE_OOM;
 
                slen = fr_value_box_from_network(vp, &vp->data, vp->vp_type, vp->da,
                                                 &FR_DBUFF_TMP(data, data_len), data_len, true);
                if (slen < 0) {
                        talloc_free(vp);
                        goto raw;
                }
                vp->vp_date = fr_unix_time_add(vp->vp_date, fr_time_delta_from_sec(DHCPV6_DATE_OFFSET));
                break;
 
        case FR_TYPE_STRUCT:
                slen = fr_struct_from_network(ctx, out, parent, data, data_len,
                                              decode_ctx, decode_value_trampoline, decode_tlv_trampoline);
                if (slen < 0) goto raw;
 
                if (parent->flags.array) return slen;
                return data_len;
 
        case FR_TYPE_GROUP:
                vp = fr_pair_afrom_da(ctx, parent);
                if (!vp) return PAIR_DECODE_OOM;
 
                ref = fr_dict_attr_ref(parent);
                if (ref && (ref->dict != dict_dhcpv6)) {
                        fr_dict_protocol_t const *proto;
 
                        proto = fr_dict_protocol(ref->dict);
                        fr_assert(proto != NULL);
 
                        if (!proto->decode) {
                        raw_free:
                                talloc_free(vp);
                                goto raw;
                        }
 
                        slen = proto->decode(vp, &vp->vp_group, data, data_len);
                        if (slen < 0) goto raw_free;
 
                        vp->vp_tainted = true;
 
                } else {
                        if (!ref) ref = fr_dict_root(dict_dhcpv6);
 
                        /*
                         *      Child VPs go into the child group, not in the main parent list.  BUT, we start
                         *      decoding attributes from the ref, and not from the group parent.
                         */
                        slen = fr_pair_tlvs_from_network(vp, &vp->vp_group, ref, data, data_len, decode_ctx, decode_option, NULL, false);
                        if (slen < 0) goto raw_free;
                }
 
                fr_pair_append(out, vp);
                return data_len;
 
        case FR_TYPE_IPV6_ADDR:
                vp = fr_pair_afrom_da(ctx, parent);
                if (!vp) return PAIR_DECODE_OOM;
 
                /*
                 *      Limit the IPv6 address to 16 octets, with no scope.
                 */
                if (data_len < sizeof(vp->vp_ipv6addr)) goto raw;
 
                slen = fr_value_box_from_network(vp, &vp->data, vp->vp_type, vp->da,
                                                 &FR_DBUFF_TMP(data,  sizeof(vp->vp_ipv6addr)),  sizeof(vp->vp_ipv6addr), true);
                if (slen < 0) goto raw_free;
                break;
 
        default:
                vp = fr_pair_afrom_da(ctx, parent);
                if (!vp) return PAIR_DECODE_OOM;
 
                slen = fr_value_box_from_network(vp, &vp->data, vp->vp_type, vp->da,
                                                 &FR_DBUFF_TMP(data, data_len), data_len, true);
                if (slen < 0) goto raw_free;
                break;
        }
 
        /*
         *      The input is larger than the decoded value, re-do it as a raw attribute.
         */
        if (!parent->flags.array && ((size_t) slen < data_len)) {
                talloc_free(vp);
                goto raw;
        }
 
        fr_assert(vp != NULL);
 
        vp->vp_tainted = true;
        fr_pair_append(out, vp);
 
        if (parent->flags.array) return slen;
 
        return data_len;
}
 
 
static ssize_t decode_vsa(TALLOC_CTX *ctx, fr_pair_list_t *out,
                          fr_dict_attr_t const *parent,
                          uint8_t const *data, size_t const data_len, void *decode_ctx)
{
        uint32_t                pen;
        fr_dict_attr_t const    *da;
        fr_pair_t               *vp;
        fr_dhcpv6_decode_ctx_t  *packet_ctx = decode_ctx;
 
        FR_PROTO_HEX_DUMP(data, data_len, "decode_vsa");
 
        if (!fr_cond_assert_msg(parent->type == FR_TYPE_VSA,
                                "%s: Internal sanity check failed, attribute \"%s\" is not of type 'vsa'",
                                __FUNCTION__, parent->name)) return PAIR_DECODE_FATAL_ERROR;
 
        /*
         *      Enterprise code plus at least one option header
         */
        if (data_len < 8) return fr_pair_raw_from_network(ctx, out, parent, data, data_len);
 
        memcpy(&pen, data, sizeof(pen));
        pen = htonl(pen);
 
        /*
         *      Verify that the parent (which should be a VSA)
         *      contains a fake attribute representing the vendor.
         *
         *      If it doesn't then this vendor is unknown, but we know
         *      vendor attributes have a standard format, so we can
         *      decode the data anyway.
         */
        da = fr_dict_attr_child_by_num(parent, pen);
        if (!da) {
                fr_dict_attr_t *n;
 
                n = fr_dict_attr_unknown_vendor_afrom_num(packet_ctx->tmp_ctx, parent, pen);
                if (!n) return PAIR_DECODE_OOM;
                da = n;
        }
 
        FR_PROTO_TRACE("decode context %s -> %s", parent->name, da->name);
 
        vp = fr_pair_find_by_da(out, NULL, da);
        if (vp) {
                return fr_pair_tlvs_from_network(vp, &vp->vp_group, da, data + 4, data_len - 4, decode_ctx, decode_option, NULL, false);
        }
 
        return fr_pair_tlvs_from_network(ctx, out, da, data + 4, data_len - 4, decode_ctx, decode_option, NULL, true);
}
 
static ssize_t decode_option(TALLOC_CTX *ctx, fr_pair_list_t *out,
                              fr_dict_attr_t const *parent,
                              uint8_t const *data, size_t const data_len, void *decode_ctx)
{
        unsigned int            option;
        size_t                  len;
        ssize_t                 slen;
        fr_dict_attr_t const    *da;
        fr_dhcpv6_decode_ctx_t  *packet_ctx = decode_ctx;
 
#ifdef STATIC_ANALYZER
        if (!packet_ctx || !packet_ctx->tmp_ctx) return PAIR_DECODE_FATAL_ERROR;
#endif
 
        /*
         *      Must have at least an option header.
         */
        if (data_len < 4) {
                fr_strerror_printf("%s: Insufficient data", __FUNCTION__);
                return -(data_len);
        }
 
        option = DHCPV6_GET_OPTION_NUM(data);
        len = DHCPV6_GET_OPTION_LEN(data);
        if (len > (data_len - 4)) {
                fr_strerror_printf("%s: Option overflows input.  "
                                   "Optional length must be less than %zu bytes, got %zu bytes",
                                   __FUNCTION__, data_len - 4, len);
                return PAIR_DECODE_FATAL_ERROR;
        }
 
        da = fr_dict_attr_child_by_num(parent, option);
        if (!da) {
                da = fr_dict_attr_unknown_raw_afrom_num(packet_ctx->tmp_ctx, parent, option);
                if (!da) return PAIR_DECODE_FATAL_ERROR;
        }
        FR_PROTO_TRACE("decode context changed %s -> %s",da->parent->name, da->name);
 
        /*
         *      Relay messages are weird, and contain complete DHCPv6
         *      packets, copied verbatim from the DHCPv6 client.
         */
        if (da == attr_relay_message) {
                fr_pair_t *vp;
 
                vp = fr_pair_afrom_da(ctx, attr_relay_message);
                if (!vp) return PAIR_DECODE_FATAL_ERROR;
 
                slen = fr_dhcpv6_decode(vp, &vp->vp_group, data + 4, len);
                if (slen < 0) {
                        talloc_free(vp);
                raw:
                        slen = fr_pair_raw_from_network(ctx, out, da, data + 4, len);
                        if (slen < 0) return slen;
                        return 4 + slen;
                }
 
                fr_pair_append(out, vp);
 
        } else if ((da->type == FR_TYPE_STRING) && fr_dhcpv6_flag_any_dns_label(da)) {
                slen = fr_pair_dns_labels_from_network(ctx, out, da, data + 4, data + 4, len, NULL, true);
                if (slen < 0) return slen;
 
        } else if (da->flags.array) {
                slen = fr_pair_array_from_network(ctx, out, da, data + 4, len, decode_ctx, decode_value);
 
        } else if (da->type == FR_TYPE_VSA) {
                bool append = false;
                fr_pair_t *vp;
 
                vp = fr_pair_find_by_da(out, NULL, da);
                if (!vp) {
                        vp = fr_pair_afrom_da(ctx, da);
                        if (!vp) return PAIR_DECODE_FATAL_ERROR;
 
                        append = true;
                }
 
                slen = decode_vsa(vp, &vp->vp_group, da, data + 4, len, decode_ctx);
                if (append) {
                        if (slen < 0) {
                                TALLOC_FREE(vp);
                        } else {
                                fr_pair_append(out, vp);
                        }
                }
 
        } else if (da->type == FR_TYPE_TLV) {
                slen = fr_pair_tlvs_from_network(ctx, out, da, data + 4, len, decode_ctx, decode_option, NULL, true);
 
        } else {
                slen = decode_value(ctx, out, da, data + 4, len, decode_ctx);
        }
 
        if (slen < 0) goto raw;
 
        return len + 4;
}
 
 
/** Create a "normal" fr_pair_t from the given data
 *
 *    0                   1                   2                   3
 *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *   |          option-code          |           option-len          |
 *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 */
ssize_t fr_dhcpv6_decode_option(TALLOC_CTX *ctx, fr_pair_list_t *out,
                                uint8_t const *data, size_t data_len, void *decode_ctx)
{
        FR_PROTO_HEX_DUMP(data, data_len, "fr_dhcpv6_decode_pair");
 
        /*
         *      The API changes, so we just bounce directly to the
         *      decode_option() function.
         *
         *      All options including VSAs in DHCPv6 MUST follow the
         *      standard format.
         */
        return decode_option(ctx, out, fr_dict_root(dict_dhcpv6), data, data_len, decode_ctx);
}
 
ssize_t fr_dhcpv6_decode_foreign(TALLOC_CTX *ctx, fr_pair_list_t *out,
                                 uint8_t const *data, size_t data_len)
{
        ssize_t slen;
        uint8_t const *attr, *end;
 
        fr_dhcpv6_decode_ctx_t decode_ctx = {};
 
        fr_assert(dict_dhcpv6 != NULL);
 
        decode_ctx.tmp_ctx = talloc(ctx, uint8_t);
 
        attr = data;
        end = data + data_len;
 
        while (attr < end) {
                slen = fr_dhcpv6_decode_option(ctx, out, attr, (end - attr), &decode_ctx);
                if (slen < 0) {
                        talloc_free(decode_ctx.tmp_ctx);
                        return slen;
                }
 
                /*
                 *      If slen is larger than the room in the packet,
                 *      all kinds of bad things happen.
                 */
                 if (!fr_cond_assert(slen <= (end - attr))) {
                        talloc_free(decode_ctx.tmp_ctx);
                         return -slen - (attr - data);
                 }
 
                attr += slen;
                talloc_free_children(decode_ctx.tmp_ctx);
        }
 
        talloc_free(decode_ctx.tmp_ctx);
        return data_len;
}
 
static int decode_test_ctx(void **out, TALLOC_CTX *ctx, UNUSED fr_dict_t const *dict)
{
        fr_dhcpv6_decode_ctx_t  *test_ctx;
 
        test_ctx = talloc_zero(ctx, fr_dhcpv6_decode_ctx_t);
        if (!test_ctx) return -1;
 
        test_ctx->tmp_ctx = talloc(test_ctx, uint8_t);
 
        *out = test_ctx;
 
        return 0;
}
 
static ssize_t fr_dhcpv6_decode_proto(TALLOC_CTX *ctx, fr_pair_list_t *out, uint8_t const *data, size_t data_len, UNUSED void *proto_ctx)
{
        size_t packet_len = data_len;
//      fr_dhcpv6_decode_ctx_t  *test_ctx = talloc_get_type_abort(proto_ctx, fr_dhcpv6_decode_ctx_t);
 
        if (!fr_dhcpv6_ok(data, packet_len, 200)) return -1;
 
        return fr_dhcpv6_decode(ctx, out, data, packet_len);
}
 
 
static ssize_t decode_pair(TALLOC_CTX *ctx, fr_pair_list_t *out, NDEBUG_UNUSED fr_dict_attr_t const *parent,
                           uint8_t const *data, size_t data_len, void *decode_ctx)
{
        fr_assert(parent == fr_dict_root(dict_dhcpv6));
 
        return decode_option(ctx, out, fr_dict_root(dict_dhcpv6), data, data_len, decode_ctx);
}
 
/*
 *      Test points
 */
extern fr_test_point_pair_decode_t dhcpv6_tp_decode_pair;
fr_test_point_pair_decode_t dhcpv6_tp_decode_pair = {
        .test_ctx       = decode_test_ctx,
        .func           = decode_pair,
};
 
extern fr_test_point_proto_decode_t dhcpv6_tp_decode_proto;
fr_test_point_proto_decode_t dhcpv6_tp_decode_proto = {
        .test_ctx       = decode_test_ctx,
        .func           = fr_dhcpv6_decode_proto
};