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: ad3f48303ffef20d76140ef1f5261f2f24449ace $
 *
 * Because what we need is yet *ANOTHER* serialisation scheme.
 *
 * @file protocols/internal/decode.c
 * @brief Functions to decode data in our internal structure.
 *
 * @copyright 2020 The FreeRADIUS server project
 * @copyright 2020 Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 */
 
#include <freeradius-devel/internal/internal.h>
#include <freeradius-devel/io/pair.h>
#include <freeradius-devel/io/test_point.h>
#include <freeradius-devel/util/proto.h>
 
static ssize_t internal_decode_pair(TALLOC_CTX *ctx, fr_pair_list_t *head, fr_dict_attr_t const *parent_da,
                                    fr_dbuff_t *dbuff, void *decode_ctx);
 
/** Decodes the value of an attribute, potentially producing a pair (added to the cursor)
 *
 */
static ssize_t internal_decode_pair_value(TALLOC_CTX *ctx, fr_pair_list_t *head, fr_dict_attr_t const *parent_da,
                                          fr_dbuff_t *dbuff,
                                          bool tainted, UNUSED void *decode_ctx)
{
        fr_pair_t       *vp;
        ssize_t         slen;
        fr_dbuff_t      work_dbuff = FR_DBUFF(dbuff);
 
        vp = fr_pair_afrom_da(ctx, parent_da);
        if (!vp) return PAIR_DECODE_OOM;
 
        /*
         *      Zero length is fine here
         */
        slen = fr_value_box_from_network(vp, &vp->data, vp->vp_type, vp->da,
                                         &work_dbuff, fr_dbuff_len(&work_dbuff), tainted);
        if (slen < 0) {
                talloc_free(vp);
                return slen;
        }
        FR_PAIR_APPEND(head, vp);
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** Decode a group
 *
 */
static ssize_t internal_decode_structural(TALLOC_CTX *ctx, fr_pair_list_t *head, fr_dict_attr_t const *parent_da,
                                          fr_dbuff_t *dbuff, void *decode_ctx)
{
        fr_pair_t       *vp;
        ssize_t         slen;
        fr_dbuff_t      work_dbuff = FR_DBUFF(dbuff);
 
        FR_PROTO_TRACE("Decoding group - %s", parent_da->name);
 
        vp = fr_pair_afrom_da(ctx, parent_da);
        if (!vp) return PAIR_DECODE_OOM;
 
        /*
         *      Decode all the children of this group
         */
        while (fr_dbuff_extend(&work_dbuff)) {
                FR_PROTO_HEX_MARKER(fr_dbuff_current(dbuff), fr_dbuff_remaining(dbuff), fr_dbuff_used(&work_dbuff),
                                    "Decoding child");
 
                slen = internal_decode_pair(vp, &vp->vp_group, parent_da, &work_dbuff, decode_ctx);
                if (slen <= 0) {
                        talloc_free(vp);
                        return slen;
                }
        }
        FR_PAIR_APPEND(head, vp);
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
static ssize_t internal_decode_pair(TALLOC_CTX *ctx, fr_pair_list_t *out, fr_dict_attr_t const *parent_da,
                                    fr_dbuff_t *dbuff, void *decode_ctx)
{
        ssize_t                 slen = 0;
        fr_dict_attr_t const    *da;
        uint8_t                 enc_byte = 0, ext_byte = 0, type_field_size, len_field_size;
        fr_dbuff_marker_t       len_field, enc_field, ext_field;
        uint64_t                len = 0, type = 0;
        size_t                  remaining, needed;
        bool                    tainted, extended, unknown = false, internal = false;
        fr_dbuff_t              work_dbuff = FR_DBUFF(dbuff);
 
        /*
         * The first byte of each attribute describes the encoding format.
         *
         * tlen (type field len)   - Describes how many byte(s) were used to encode the type.
         * llen (length field len) - Describes how many byte(s) were used to encode the length.
         * t (tainted)             - This attribute was tainted when it was encoded,
         *                           so should be marked tainted now.
         * e (extended)            - Process the next byte as an extension of the encoding
         *                           field (allows for future extensions).
         *
         * 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
         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         * |tlen |llen |t|e|   Type (min)  |  Length (min) | value...
         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         *
         */
        remaining = fr_dbuff_extend_lowat(NULL, &work_dbuff, 3);
        if (remaining < 3) {
                fr_strerror_printf("%s: Insufficient data.  Need %zu additional byte(s)",
                                   __FUNCTION__, 3 - remaining);
                return -fr_dbuff_len(&work_dbuff);
        }
 
        fr_dbuff_marker(&enc_field, &work_dbuff);
        fr_dbuff_marker(&ext_field, &work_dbuff);       /* Placed here to make static analysis happy */
        FR_DBUFF_OUT_RETURN(&enc_byte, &work_dbuff);
        type_field_size = ((enc_byte & FR_INTERNAL_MASK_TYPE) >> 5) + 1;        /* bits 0-2 */
        len_field_size = ((enc_byte & FR_INTERNAL_MASK_LEN) >> 2) + 1;          /* bits 3-5 */
 
        tainted = (enc_byte & FR_INTERNAL_FLAG_TAINTED) != 0;                   /* bit 6 */
        extended = (enc_byte & FR_INTERNAL_FLAG_EXTENDED) != 0;                 /* bit 7 */
 
        /* Processed first encoding byte */
 
        needed = type_field_size + len_field_size + extended;
        remaining = fr_dbuff_extend_lowat(NULL, &work_dbuff, needed);
        if (remaining < needed) {
                fr_strerror_printf("%s: Encoding byte invalid, fields overrun input data. "
                                   "%zu byte(s) remaining, need %zu byte(s)",
                                   __FUNCTION__, remaining, needed);
                return -needed;
        }
 
        /*
         * The second (optional) extension byte carries more flag information from the attribute.
         *
         * u (unknown attribute)   - When this pair was converted from network to internal
         *                           format, it was found to be badly formatted, or not
         *                           match an existing dictionary definition.
         *                           A new unknown DA should be allocated for this attribute
         *                           and it should be treated as raw octets.
         * i (internal attribute)  - Resolve this attribute in the internal dictionary.
         * - (currently unused)    - Unused flag.
         * e (extended)            - Encoding definitions continue to a third byte.
         *
         * 0                   1
         * 0 1 2 3 4 5 6 7 8 9 0
         * +-+-+-+-+-+-+-+-+-+-+
         * |u|i|-|-|-|-|-|e|
         * +-+-+-+-+-+-+-+-+-+-+
         *
         */
        if (extended) {
                fr_dbuff_set(&ext_field, &work_dbuff);
                FR_DBUFF_OUT_RETURN(&ext_byte, &work_dbuff);
                unknown = (ext_byte & FR_INTERNAL_FLAG_UNKNOWN) != 0;
                internal = (ext_byte & FR_INTERNAL_FLAG_INTERNAL) != 0;
                if (ext_byte & FR_INTERNAL_FLAG_EXTENDED) {
                        fr_strerror_printf("%s: Third extension byte not in use", __FUNCTION__);
                        return PAIR_DECODE_FATAL_ERROR;
                }
        }
 
        FR_DBUFF_OUT_UINT64V_RETURN(&type, &work_dbuff, type_field_size);
        if (type > UINT32_MAX) {
                fr_strerror_printf("%s: Attribute number %" PRIu64 " is larger than 32 bits", __FUNCTION__, type);
                return PAIR_DECODE_FATAL_ERROR;
        }
 
        /*
         *      This is the length of the start *after* the flags and
         *      type/length fields.
         */
        fr_dbuff_marker(&len_field, &work_dbuff);
        FR_DBUFF_OUT_UINT64V_RETURN(&len, &work_dbuff, len_field_size);
 
        remaining = fr_dbuff_extend_lowat(NULL, &work_dbuff, len);
        if (remaining < len) {
                fr_strerror_printf("%s: Length field value overruns input data. "
                                   "%zu byte(s) remaining, need %zu byte(s)",
                                   __FUNCTION__, remaining, (size_t) len);
                return -(fr_dbuff_current(&len_field) - fr_dbuff_start(&work_dbuff));
        }
 
        /*
         *      Internal flag is only set on the outer attribute
         *      so it's fine to swap the parent_da.
         */
        if (internal) {
                if (!parent_da->flags.is_root && !(parent_da->type == FR_TYPE_GROUP)) {
                        fr_strerror_printf("%s: Internal flag can only be set on top level attribute", __FUNCTION__);
                        return PAIR_DECODE_FATAL_ERROR;
                }
                parent_da = fr_dict_root(fr_dict_internal());
        }
 
        if (unknown || parent_da->flags.is_unknown) {
        unknown:
                FR_PROTO_TRACE("Unknown attribute %" PRIu64, type);
                da = fr_dict_attr_unknown_raw_afrom_num(ctx, parent_da, (unsigned int) type);
                if (!da) return PAIR_DECODE_FATAL_ERROR;
                unknown = true;
        } else {
                da = fr_dict_attr_child_by_num(parent_da, (unsigned int) type);
                if (!da) goto unknown;
        }
 
        FR_PROTO_TRACE("decode context changed %s -> %s", da->parent->name, da->name);
 
        /*
         *      Set the end of our dbuff to match the length
         *      of the attribute.
         */
        fr_dbuff_set_end(&work_dbuff, fr_dbuff_current(&work_dbuff) + len);
 
        switch (da->type) {
        /*
         *      Structural types
         *
         *      STRUCTs are encoded as TLVs, because the struct
         *      packing only applies to the original protocol, and not
         *      to our internal encoding.
         */
         case FR_TYPE_STRUCTURAL:
                if (fr_type_is_vsa(da->type)) {
                        if (unlikely(unknown)) {
                                fr_strerror_printf("%s: %s can't be marked as unknown", __FUNCTION__,
                                                fr_type_to_str(da->type));
                                fr_dbuff_set(&work_dbuff, &ext_field);
                        error:
                                if (unknown) fr_dict_attr_unknown_free(&da);
                                return fr_pair_decode_slen(slen, fr_dbuff_start(&work_dbuff), fr_dbuff_current(&work_dbuff));
                        }
                }
                /*
                 *      It's ok for this function to return 0
                 *      we can have empty groups (i.e. groups
                 *      with no children)
                 */
                slen = internal_decode_structural(ctx, out, da, &work_dbuff, decode_ctx);
                if (slen < 0) goto error;
                break;
 
        default:
                /*
                 *      It's ok for this function to return 0
                 *      we can have zero length strings.
                 */
                slen = internal_decode_pair_value(ctx, out, da, &work_dbuff, tainted, decode_ctx);
                if (slen < 0) goto error;
        }
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** Create a single fr_pair_t and all its nesting
 *
 */
ssize_t fr_internal_decode_pair(TALLOC_CTX *ctx, fr_pair_list_t *list, fr_dict_attr_t const *parent,
                                uint8_t const *data, size_t data_len, void *decode_ctx)
{
        return fr_internal_decode_pair_dbuff(ctx, list, parent, &FR_DBUFF_TMP(data, data_len), decode_ctx);
}
 
ssize_t fr_internal_decode_pair_dbuff(TALLOC_CTX *ctx, fr_pair_list_t *out, fr_dict_attr_t const *parent,
                                fr_dbuff_t *dbuff, void *decode_ctx)
{
        fr_pair_list_t  tmp;
        ssize_t         slen;
        fr_dbuff_t      work_dbuff = FR_DBUFF(dbuff);
 
        fr_pair_list_init(&tmp);
 
        slen = internal_decode_pair(ctx, &tmp, parent, &work_dbuff, decode_ctx);
        if (slen <= 0) {
                fr_pair_list_free(&tmp);
                return slen;
        }
 
        fr_pair_list_append(out, &tmp);
 
        return fr_dbuff_set(dbuff, &work_dbuff);
}
 
/** Retrieve all pairs from the dbuff
 *
 * @param ctx           to create new pairs in
 * @param out           list to append pairs to
 * @param parent        attribute within which which to decode
 * @param dbuff         to parse
 * @param decode_ctx    to pass to decoder function
 * @return
 *      - bytes of dbuff consumed
 *      - < 0 on error
 */
ssize_t fr_internal_decode_list_dbuff(TALLOC_CTX *ctx, fr_pair_list_t *out, fr_dict_attr_t const *parent,
                                          fr_dbuff_t *dbuff, void *decode_ctx)
{
        ssize_t         ret, len = 0;
 
        while (fr_dbuff_remaining(dbuff)) {
                ret = fr_internal_decode_pair_dbuff(ctx, out, parent, dbuff, decode_ctx);
                if (ret < 0) return ret;
                if (ret == 0) break;
                len += ret;
        }
 
        return len;
}
 
/*
 *      Test points
 */
extern fr_test_point_pair_decode_t internal_tp_decode_pair;
fr_test_point_pair_decode_t internal_tp_decode_pair = {
        .test_ctx       = NULL,
        .func           = fr_internal_decode_pair
};