json.c

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/*
 *   This program is 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: e90ea072c88da82d354740724ec29a9a8b1c7a5b $
 * @file json.c
 * @brief Common functions for working with json-c
 *
 * @author Arran Cudbard-Bell
 * @author Matthew Newton
 *
 * @copyright 2015 Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 * @copyright 2015,2020 Network RADIUS SAS (legal@networkradius.com)
 * @copyright 2015 The FreeRADIUS Server Project
 */
#include <freeradius-devel/util/debug.h>
#include <freeradius-devel/util/base16.h>
#include <freeradius-devel/util/sbuff.h>
#include <freeradius-devel/util/types.h>
#include <freeradius-devel/util/value.h>
#include "base.h"
 
fr_table_num_sorted_t const fr_json_format_table[] = {
        { L("array"),           JSON_MODE_ARRAY         },
        { L("array_of_names"),  JSON_MODE_ARRAY_OF_NAMES        },
        { L("array_of_values"), JSON_MODE_ARRAY_OF_VALUES       },
        { L("object"),          JSON_MODE_OBJECT                },
        { L("object_simple"),   JSON_MODE_OBJECT_SIMPLE },
};
size_t fr_json_format_table_len = NUM_ELEMENTS(fr_json_format_table);
 
static fr_json_format_t const default_json_format = {
        .attr = { .prefix = NULL },
        .value = { .value_is_always_array = true },
        .output_mode = JSON_MODE_OBJECT
};
 
static conf_parser_t const json_format_attr_config[] = {
        { FR_CONF_OFFSET("prefix", fr_json_format_attr_t, prefix) },
        CONF_PARSER_TERMINATOR
};
 
static conf_parser_t const json_format_value_config[] = {
        { FR_CONF_OFFSET("single_value_as_array", fr_json_format_value_t, value_is_always_array), .dflt = "no" },
        { FR_CONF_OFFSET("enum_as_integer", fr_json_format_value_t, enum_as_int), .dflt = "no" },
        { FR_CONF_OFFSET("always_string", fr_json_format_value_t, always_string), .dflt = "no" },
        CONF_PARSER_TERMINATOR
};
 
conf_parser_t const fr_json_format_config[] = {
        { FR_CONF_OFFSET("output_mode", fr_json_format_t, output_mode_str), .dflt = "object" },
        { FR_CONF_OFFSET_SUBSECTION("attribute", 0, fr_json_format_t, attr, json_format_attr_config) },
        { FR_CONF_OFFSET_SUBSECTION("value", 0, fr_json_format_t, value, json_format_value_config) },
 
        CONF_PARSER_TERMINATOR
};
 
static inline CC_HINT(always_inline)
void json_object_put_assert(json_object *obj)
{
        int ret;
 
        ret = json_object_put(obj);
        if (ret == 1) return;
 
        fr_assert_fail("json_object_put did not free object (returned %u), likely leaking memory", ret);
}
 
/** Convert json object to fr_value_box_t
 *
 * @param[in] ctx       to allocate any value buffers in (should usually be the same as out).
 * @param[in] out       Where to write value.  Must be initialised.
 * @param[in] object    to convert.
 * @param[in] enumv     Any string values are assumed to be in PRESENTATION format, meaning
 *                      that if an enumv is specified, they'll be checked against the list
 *                      of aliases for that enumeration, and possibly converted into one of
 *                      the enumeration values (which may not be a string).
 * @param[in] tainted   Whether the data source is untrusted.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int fr_json_object_to_value_box(TALLOC_CTX *ctx, fr_value_box_t *out, json_object *object,
                                fr_dict_attr_t const *enumv, bool tainted)
{
        switch (json_object_get_type(object)) {
        case json_type_string:
        {
                char const      *value;
                size_t          len;
                fr_dict_enum_value_t    *found;
 
                value = json_object_get_string(object);
                len = json_object_get_string_len(object);
 
                if (!enumv) goto no_enumv;
 
                if (fr_dict_valid_name(value, len) < 0) goto no_enumv;
 
                /*
                 *      If an alias exists, use that value instead
                 */
                found = fr_dict_enum_by_name(enumv, value, len);
                if (found) {
                        if (fr_value_box_copy(ctx, out, found->value) < 0) return -1;
                        return 0;
                }
 
        no_enumv:
                /*
                 *      Just copy the string to the box.
                 */
                fr_value_box_bstrndup(out, out, NULL, value, len, tainted);
        }
                break;
 
        case json_type_double:
                fr_value_box(out, json_object_get_double(object), tainted);
                break;
 
        case json_type_int:
        {
#ifdef HAVE_JSON_OBJECT_GET_INT64
                int64_t num;
#else
                int32_t num;
#endif
 
#ifndef HAVE_JSON_OBJECT_GET_INT64
                num = json_object_get_int(object);
#else
                num = json_object_get_int64(object);
                if (num < INT32_MIN) {                  /* 64bit signed*/
                        fr_value_box(out, (int64_t)num, tainted);
                } else if (num > UINT32_MAX) {          /* 64bit unsigned */
                        fr_value_box(out, (uint64_t)num, tainted);
                } else
#endif
                if (num < INT16_MIN) {                  /* 32bit signed */
                        fr_value_box(out, (int32_t)num, tainted);
                } else if (num < INT8_MIN) {            /* 16bit signed */
                        fr_value_box(out, (int16_t)num, tainted);
                } else if (num < 0) {                   /* 8bit signed */
                        fr_value_box(out, (int8_t)num, tainted);
                } else if (num > UINT16_MAX) {          /* 32bit unsigned */
                        fr_value_box(out, (uint32_t)num, tainted);
                } else if (num > UINT8_MAX) {           /* 16bit unsigned */
                        fr_value_box(out, (uint16_t)num, tainted);
                } else {                                /* 8bit unsigned */
                        fr_value_box(out, (uint8_t)num, tainted);
                }
        }
                break;
 
        case json_type_boolean:
                /* Must be cast to bool for correct generic case selection */
                fr_value_box(out, ((bool)(json_object_get_boolean(object) > 0)), tainted);
                break;
 
        case json_type_null:
        case json_type_array:
        case json_type_object:
        {
                char const *value = json_object_to_json_string(object);
 
                fr_value_box_bstrndup(out, out, NULL, value, strlen(value), tainted);
        }
                break;
        }
 
        out->tainted = tainted;
 
        return 0;
}
 
/** Convert boxed value_box to a JSON object
 *
 * @param[in] data      to convert.
 */
json_object *json_object_from_value_box(fr_value_box_t const *data)
{
        /*
         *      We're converting to PRESENTATION format
         *      so any attributes with enumeration values
         *      should be converted to string types.
         */
        if (data->enumv) {
                fr_dict_enum_value_t *enumv;
 
                enumv = fr_dict_enum_by_value(data->enumv, data);
                if (enumv) return json_object_new_string(enumv->name);
        }
 
        switch (data->type) {
        default:
        do_string:
        {
                char            buffer[64];
                fr_sbuff_t      sbuff = FR_SBUFF_IN(buffer, sizeof(buffer));
 
                if (fr_value_box_print(&sbuff, data, NULL) <= 0) return NULL;
 
                return json_object_new_string_len(buffer, fr_sbuff_used(&sbuff));
        }
 
        case FR_TYPE_STRING:
                return json_object_new_string_len(data->vb_strvalue, data->vb_length);
 
        case FR_TYPE_OCTETS:
                return json_object_new_string_len((char const *)data->vb_octets, data->vb_length);
 
        case FR_TYPE_BOOL:
                return json_object_new_boolean(data->vb_uint8);
 
        case FR_TYPE_UINT8:
                return json_object_new_int(data->vb_uint8);
 
        case FR_TYPE_UINT16:
                return json_object_new_int(data->vb_uint16);
 
#ifdef HAVE_JSON_OBJECT_GET_INT64
        case FR_TYPE_UINT32:
                return json_object_new_int64((int64_t)data->vb_uint64); /* uint32_t (max) > int32_t (max) */
 
        case FR_TYPE_UINT64:
                if (data->vb_uint64 > INT64_MAX) goto do_string;
                return json_object_new_int64(data->vb_uint64);
#else
        case FR_TYPE_UINT32:
                if (data->vb_uint32 > INT32_MAX) goto do_string;
                return json_object_new_int(data->vb_uint32);
#endif
 
        case FR_TYPE_INT8:
                return json_object_new_int(data->vb_int8);
 
        case FR_TYPE_INT16:
                return json_object_new_int(data->vb_int16);
 
        case FR_TYPE_INT32:
                return json_object_new_int(data->vb_int32);
 
#ifdef HAVE_JSON_OBJECT_GET_INT64
        case FR_TYPE_INT64:
                return json_object_new_int64(data->vb_int64);
 
        case FR_TYPE_SIZE:
                return json_object_new_int64(data->vb_size);
#endif
 
        case FR_TYPE_STRUCTURAL:
                return NULL;
        }
}
 
/** Print a value box as its equivalent JSON format without going via a struct json_object (in most cases)
 *
 * @param[out] out              buffer to write to.
 * @param[in] vb                to print.
 * @param[in] include_quotes    whether we should wrap string values,
 *                              or non-native types like IPv4 addresses in quotes.
 * @return
 *      - <0 on error.
 *      - >= number of bytes written.
 */
fr_slen_t fr_json_str_from_value(fr_sbuff_t *out, fr_value_box_t *vb, bool include_quotes)
{
        fr_sbuff_t our_out = FR_SBUFF(out);
 
        switch (vb->type) {
        case FR_TYPE_NULL:
                FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "null");
                break;
 
        case FR_TYPE_BOOL:
                FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, vb->vb_bool ? "true" : "false");
                break;
 
        /*
         *      This is identical to JSON-C's escaping function
         *      but we avoid creating JSON objects just to be able
         *      to escape strings.
         */
        case FR_TYPE_STRING:
        case FR_TYPE_OCTETS:
        {
                char const *last_app, *p, *end;
 
                if (include_quotes) FR_SBUFF_IN_CHAR_RETURN(&our_out, '"');
 
                last_app = p = vb->vb_strvalue;
                end = p + vb->vb_length;
 
                while (p < end) {
                        if (*p < ' ') {
                                if (p > last_app) FR_SBUFF_IN_BSTRNCPY_RETURN(&our_out, last_app, p - last_app);
 
                                switch (*p) {
                                case '\b':
                                        FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "\\b");
                                        break;
 
                                case '\n':
                                        FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "\\n");
                                        break;
 
                                case '\r':
                                        FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "\\r");
                                        break;
 
                                case '\t':
                                        FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "\\t");
                                        break;
 
                                case '\f':
                                        FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "\\f");
                                        break;
 
                                case '"':
                                        FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "\\\"");
                                        break;
 
                                case '\\':
                                        FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "\\\\");
                                        break;
 
                                case '/':
                                        FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "\\/");
                                        break;
 
                                default:
                                        FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "\\u00");
                                        fr_base16_encode(&our_out, &FR_DBUFF_TMP((uint8_t const *)p, 1));
                                }
 
                                last_app = p + 1;
                        }
                        p++;
                }
                if (end > last_app) FR_SBUFF_IN_BSTRNCPY_RETURN(&our_out, last_app, end - last_app);
                if (include_quotes) FR_SBUFF_IN_CHAR_RETURN(&our_out, '"');
        }
                break;
 
        case FR_TYPE_UINT8:
                FR_SBUFF_IN_SPRINTF_RETURN(&our_out, "%u", vb->vb_uint8);
                break;
 
        case FR_TYPE_UINT16:
                FR_SBUFF_IN_SPRINTF_RETURN(&our_out, "%u", vb->vb_uint16);
                break;
 
        case FR_TYPE_UINT32:
                FR_SBUFF_IN_SPRINTF_RETURN(&our_out, "%u", vb->vb_uint32);
                break;
 
        case FR_TYPE_UINT64:
                FR_SBUFF_IN_SPRINTF_RETURN(&our_out, "%u", vb->vb_uint64);
                break;
 
        case FR_TYPE_INT8:
                FR_SBUFF_IN_SPRINTF_RETURN(&our_out, "%i", vb->vb_int8);
                break;
 
        case FR_TYPE_INT16:
                FR_SBUFF_IN_SPRINTF_RETURN(&our_out, "%i", vb->vb_int16);
                break;
 
        case FR_TYPE_INT32:
                FR_SBUFF_IN_SPRINTF_RETURN(&our_out, "%i", vb->vb_int32);
                break;
 
        case FR_TYPE_INT64:
                FR_SBUFF_IN_SPRINTF_RETURN(&our_out, "%i", vb->vb_int64);
                break;
 
        case FR_TYPE_SIZE:
                FR_SBUFF_IN_SPRINTF_RETURN(&our_out, "%zu", vb->vb_size);
                break;
 
        /*
         *      It's too complex to replicate the float/double printing
         *      here, so pass it off to JSON-C's printing functions.
         */
        case FR_TYPE_FLOAT32:
        {
                struct json_object *obj;
                fr_slen_t slen;
 
                obj = json_object_new_double((double)vb->vb_float32);
                if (unlikely(obj == NULL)) return -1;
                slen = fr_sbuff_in_strcpy(&our_out, json_object_to_json_string(obj));
                json_object_put_assert(obj);
                return slen;
        }
 
        case FR_TYPE_FLOAT64:
        {
                struct json_object *obj;
                fr_slen_t slen;
 
                obj = json_object_new_double((double)vb->vb_float64);
                if (unlikely(obj == NULL)) return -1;
                slen = fr_sbuff_in_strcpy(&our_out, json_object_to_json_string(obj));
                json_object_put_assert(obj);
                return slen;
        }
 
        case FR_TYPE_IPV4_ADDR:
        case FR_TYPE_IPV4_PREFIX:
        case FR_TYPE_IPV6_ADDR:
        case FR_TYPE_IPV6_PREFIX:
        case FR_TYPE_COMBO_IP_ADDR:
        case FR_TYPE_COMBO_IP_PREFIX:
        case FR_TYPE_IFID:
        case FR_TYPE_ETHERNET:
        case FR_TYPE_DATE:
        case FR_TYPE_TIME_DELTA:
        {
                fr_slen_t slen;
 
                if (include_quotes) FR_SBUFF_IN_CHAR_RETURN(&our_out, '"');
                slen = fr_value_box_print(&our_out, vb, NULL);
                if (include_quotes) FR_SBUFF_IN_CHAR_RETURN(&our_out, '"');
                if (slen < 0) return slen;
        }
                break;
 
        case FR_TYPE_STRUCTURAL:
                fr_strerror_const("Structural boxes not yet supported");
                return -1;
 
        case FR_TYPE_VOID:
        case FR_TYPE_VALUE_BOX:
        case FR_TYPE_MAX:
                fr_strerror_printf("Box type %s cannot be converted to string", fr_type_to_str(vb->type));
                return -1;
        }
 
        return fr_sbuff_set(out, &our_out);
}
 
/** Print JSON-C version
 *
 */
void fr_json_version_print(void)
{
#ifdef HAVE_JSON_C_VERSION
        INFO("libfreeradius-json: json-c version: %s", json_c_version());
#else
        INFO("libfreeradius-json: json-c version: Unknown (less than 0.10) - Please upgrade");
#endif
}
 
 
/** Convert fr_pair_t into a JSON object
 *
 * If format.value.enum_as_int is set, and the given VP is an enum
 * value, the integer value is returned as a json_object rather
 * than the text representation.
 *
 * If format.value.always_string is set then a numeric value pair
 * will be returned as a JSON string object.
 *
 * @param[in] ctx       Talloc context.
 * @param[out] out      returned json object.
 * @param[in] vp        to get the value of.
 * @param[in] format    format definition, or NULL.
 * @return
 *      - 1 if 'out' is the integer enum value, 0 otherwise
 *      - -1 on error.
 */
static int json_afrom_value_box(TALLOC_CTX *ctx, json_object **out,
                                fr_pair_t *vp, fr_json_format_t const *format)
{
        struct json_object      *obj;
        fr_value_box_t const    *vb;
        fr_value_box_t          vb_str = FR_VALUE_BOX_INITIALISER_NULL(vb_str);
        int                     is_enum = 0;
 
        fr_assert(vp);
 
        vb = &vp->data;
 
        if (format && format->value.enum_as_int) {
                is_enum = fr_pair_value_enum_box(&vb, vp);
                fr_assert(is_enum >= 0);
        }
 
        if (format && format->value.always_string) {
                if (fr_value_box_cast(ctx, &vb_str, FR_TYPE_STRING, NULL, vb) < 0) {
                        return -1;
                }
 
                vb = &vb_str;
        }
 
        MEM(obj = json_object_from_value_box(vb));
 
        if (format && format->value.always_string) {
                fr_value_box_clear(&vb_str);
        }
 
        *out = obj;
        return is_enum;
}
 
 
/** Get attribute name with optional prefix
 *
 * If the format "attr.prefix" string is set then prepend this
 * to the given attribute name, otherwise just return name alone.
 *
 * @param[out] out sbuff to write the new name
 * @param[in] da dictionary attribute to get name of
 * @param[in] format json format structure
 * @return length of attribute name
 */
static inline ssize_t attr_name_with_prefix(fr_sbuff_t *out, fr_dict_attr_t const *da, fr_json_format_t const *format)
{
        fr_sbuff_t our_out;
 
        if (!out) return 0;
 
        our_out = FR_SBUFF(out);
 
        if (format->attr.prefix) {
                FR_SBUFF_IN_STRCPY_RETURN(&our_out, format->attr.prefix);
                FR_SBUFF_IN_CHAR_RETURN(&our_out, ':');
        }
 
        FR_SBUFF_IN_BSTRNCPY_RETURN(&our_out, da->name, da->name_len);
 
        FR_SBUFF_SET_RETURN(out, &our_out);
}
 
 
/** Verify that the options in fr_json_format_t are valid
 *
 * Warnings are optional, will fatal error if the format is corrupt.
 *
 * @param[in] format    the format structure to check
 * @param[in] verbose   print out warnings if set
 * @return              true if format is good, otherwise false
 */
bool fr_json_format_verify(fr_json_format_t const *format, bool verbose)
{
        bool ret = true;
 
        fr_assert(format);
 
        switch (format->output_mode) {
        case JSON_MODE_OBJECT:
        case JSON_MODE_OBJECT_SIMPLE:
        case JSON_MODE_ARRAY:
                /* all options are valid */
                return true;
        case JSON_MODE_ARRAY_OF_VALUES:
                if (format->attr.prefix) {
                        if (verbose) WARN("attribute name prefix not valid in output_mode 'array_of_values' and will be ignored");
                        ret = false;
                }
                if (format->value.value_is_always_array) {
                        if (verbose) WARN("'value_is_always_array' not valid in output_mode 'array_of_values' and will be ignored");
                        ret = false;
                }
                return ret;
        case JSON_MODE_ARRAY_OF_NAMES:
                if (format->value.value_is_always_array) {
                        if (verbose) WARN("'value_is_always_array' not valid in output_mode 'array_of_names' and will be ignored");
                        ret = false;
                }
                if (format->value.enum_as_int) {
                        if (verbose) WARN("'enum_as_int' not valid in output_mode 'array_of_names' and will be ignored");
                        ret = false;
                }
                if (format->value.always_string) {
                        if (verbose) WARN("'always_string' not valid in output_mode 'array_of_names' and will be ignored");
                        ret = false;
                }
                return ret;
        default:
                ERROR("JSON format output mode is invalid");
        }
 
        /* If we get here, something has gone wrong */
        fr_assert(0);
 
        return false;
}
 
#define INVALID_TYPE \
do { \
        fr_assert(0); \
        fr_strerror_printf("Invalid type %s for attribute %s", fr_type_to_str(vp->vp_type), vp->da->name); \
        return NULL; \
} while (0)
 
/** Returns a JSON object representation of a list of value pairs
 *
 * The result is a struct json_object, which should be free'd with
 * json_object_put() by the caller. Intended to only be called by
 * fr_json_afrom_pair_list().
 *
 * This function generates the "object" format, JSON_MODE_OBJECT.
 * @see fr_json_format_s
 *
@verbatim
{
        "<attribute0>":{
                "type":"<type0>",
                "value":[<value0>,<value1>,<valueN>]            // if value_is_always_array is true
        },                                                      // or
        "<attribute1>":{
                "type":"<type1>",
                "value":<value0>                                // if value_is_always_array is false
                                                                // and there is only one value
        },
        "<attributeN>":{
                "type":"<typeN>",
                "value":[...]
        }
}
@endverbatim
 *
 * @param[in] ctx       Talloc context.
 * @param[in] vps       a list of value pairs.
 * @param[in] format    Formatting control, must be set.
 * @return JSON object with the generated representation.
 */
static json_object *json_object_afrom_pair_list(TALLOC_CTX *ctx, fr_pair_list_t *vps,
                                                fr_json_format_t const *format)
{
        fr_pair_t               *vp;
        struct json_object      *obj;
        char                    buf[FR_DICT_ATTR_MAX_NAME_LEN + 32];
 
        /* Check format and type */
        fr_assert(format);
        fr_assert(format->output_mode == JSON_MODE_OBJECT);
 
        MEM(obj = json_object_new_object());
 
        for (vp = fr_pair_list_head(vps);
             vp;
             vp = fr_pair_list_next(vps, vp)) {
                fr_sbuff_t              attr_name;
                struct json_object      *vp_object, *values, *value, *type_name;
 
                if (vp->vp_raw) continue;
 
                /*
                 *      Get attribute name and value.
                 */
                fr_sbuff_init_in(&attr_name, buf, sizeof(buf) - 1);
                if (attr_name_with_prefix(&attr_name, vp->da, format) < 0) {
                        return NULL;
                }
 
                switch (vp->vp_type) {
                case FR_TYPE_LEAF:
                        if (json_afrom_value_box(ctx, &value, vp, format) < 0) {
                                fr_strerror_const("Failed to convert attribute value to JSON object");
                        error:
                                json_object_put_assert(obj);
 
                                return NULL;
                        }
                        break;
                /*
                 *      For nested attributes we recurse.  The nesting is represented
                 *      as a table, either as the single value, or as an element in
                 *      an array.
                 *
                 *      ...
                 *      "value" : { "nested_attr" : { "type" : "<nested_type>", "value" : "<nested_attr_value>" } }
                 *      ...
                 *
                 *      ...
                 *      "value" : [ { "nested_attr" : { "type" : "<nested_type>", "value" : "<nested_attr_value>" } } ]
                 *      ...
                 *
                 *      The formatting of nested attributes and their structure is
                 *      identical to top level attributes.
                 */
                case FR_TYPE_STRUCTURAL:
                        value = json_object_afrom_pair_list(ctx, &vp->vp_group, format);
                        break;
 
                default:
                        INVALID_TYPE;
                }
 
                /*
                 *      Look in the table to see if we already have a key for the attribute
                 *      we're working on.
                 *
                 *      If we don't we create a new object in either the form:
                 *
                 *      "<attribute>": {
                 *              "type": "<type>",
                 *              "value": [<value>]              // if value_is_always_array is true
                 *                                              // or
                 *              "value": <value>                // if value_is_always_array is false
                 *                                              // and there is only one value
                 *      }
                 */
                if (!json_object_object_get_ex(obj, fr_sbuff_start(&attr_name), &vp_object)) {
                        /*
                         *      Wasn't there, so create a new object for this attribute.
                         */
                        MEM(vp_object = json_object_new_object());
                        json_object_object_add(obj, fr_sbuff_start(&attr_name), vp_object);
 
                        /*
                         *      Add "type" to newly created keys.
                         */
                        MEM(type_name = json_object_new_string(fr_type_to_str(vp->vp_type)));
                        json_object_object_add_ex(vp_object, "type", type_name, JSON_C_OBJECT_KEY_IS_CONSTANT);
 
                        /*
                         *      Create a "value" array to hold any attribute values for this attribute...
                         */
                        if (format->value.value_is_always_array) {
                                MEM(values = json_object_new_array());
                                json_object_object_add_ex(vp_object, "value", values, JSON_C_OBJECT_KEY_IS_CONSTANT);
                                json_object_array_add(values, value);
                                continue;
                        }
 
                        /*
                         *      ...or just add the value directly.
                         */
                        json_object_object_add_ex(vp_object, "value", value, JSON_C_OBJECT_KEY_IS_CONSTANT);
 
                        continue;       /* Next attribute! */
                }
 
                /*
                 *      Find the 'values' array to add the current value to.
                 */
                if (!fr_cond_assert(json_object_object_get_ex(vp_object, "value", &values))) {
                        fr_strerror_const("Inconsistent JSON tree");
                        goto error;
                }
 
                /*
                 *      If value_is_always_array is no set then "values" may not be an array, so it will
                 *      need converting to an array to add this extra attribute.
                 */
                if (!format->value.value_is_always_array) {
                        json_type               type;
                        struct json_object      *convert_value = values;
 
                        /* Check "values" type */
                        type = json_object_get_type(values);
 
                        /* It wasn't an array, so turn it into one with the old value as the first entry */
                        if (type != json_type_array) {
                                MEM(values = json_object_new_array());
                                json_object_array_add(values, json_object_get(convert_value));
                                json_object_object_del(vp_object, "value");
                                json_object_object_add_ex(vp_object, "value", values,
                                                                JSON_C_OBJECT_KEY_IS_CONSTANT);
                        }
                }
                json_object_array_add(values, value);
        }
 
        return obj;
}
 
 
/** Returns a JSON object representation of a list of value pairs
 *
 * The result is a struct json_object, which should be free'd with
 * json_object_put() by the caller. Intended to only be called by
 * fr_json_afrom_pair_list().
 *
 * This function generates the "simple object" format, JSON_MODE_OBJECT_SIMPLE.
 * @see fr_json_format_s
 *
@verbatim
{
        "<attribute0>":[<value0>,<value1>,<valueN>]     // if value_is_always_array is true
                                                        // or
        "<attribute1>":<value0>                         // if value_is_always_array is false,
                                                        // and there is only one value
        "<attributeN>":[<value0>,<value1>,<valueN>]
}
@endverbatim
 *
 * @param[in] ctx       Talloc context.
 * @param[in] vps       a list of value pairs.
 * @param[in] format    Formatting control, must be set.
 * @return JSON object with the generated representation.
 */
static json_object *json_smplobj_afrom_pair_list(TALLOC_CTX *ctx, fr_pair_list_t *vps,
                                                 fr_json_format_t const *format)
{
        fr_pair_t               *vp;
        struct json_object      *obj;
        char                    buf[FR_DICT_ATTR_MAX_NAME_LEN + 32];
        json_type               type;
 
        /* Check format and type */
        fr_assert(format);
        fr_assert(format->output_mode == JSON_MODE_OBJECT_SIMPLE);
 
        MEM(obj = json_object_new_object());
 
        for (vp = fr_pair_list_head(vps);
             vp;
             vp = fr_pair_list_next(vps, vp)) {
                fr_sbuff_t              attr_name;
                struct json_object      *vp_object, *value;
                struct json_object      *values = NULL;
                bool                    add_single = false;
 
                if (vp->vp_raw) continue;
 
                /*
                 *      Get attribute name and value.
                 */
                fr_sbuff_init_in(&attr_name, buf, sizeof(buf) - 1);
                if (attr_name_with_prefix(&attr_name, vp->da, format) < 0) {
                        return NULL;
                }
 
                switch (vp->vp_type) {
                case FR_TYPE_LEAF:
                        if (json_afrom_value_box(ctx, &value, vp, format) < 0) {
                                fr_strerror_const("Failed to convert attribute value to JSON object");
                                json_object_put_assert(obj);
 
                                return NULL;
                        }
                        break;
                /*
                 *      For nested attributes we recurse.  The nesting is represented
                 *      as a table, either as the single value, or as an element in
                 *      an array.
                 *
                 *      ...
                 *      "<parent>" : { "<nested_attr>" : <nested_attr_value> }
                 *      ...
                 *
                 *      ...
                 *      "<parent>" : [ { "<nested_attr>" : "<nested_attr_value>" } ]
                 *      ...
                 *
                 *      The formatting of nested attributes and their structure is
                 *      identical to top level attributes.
                 */
                case FR_TYPE_STRUCTURAL:
                        value = json_smplobj_afrom_pair_list(ctx, &vp->vp_group, format);
                        break;
 
                default:
                        INVALID_TYPE;
                }
 
                /*
                 *      See if we already have a key in the table we're working on,
                 *      if not then create a new one.
                 */
                if (!json_object_object_get_ex(obj, fr_sbuff_start(&attr_name), &vp_object)) {
                        if (format->value.value_is_always_array) {
                                /*
                                 *      We have been asked to ensure /all/ values are lists,
                                 *      even if there's only one attribute.
                                 */
                                MEM(values = json_object_new_array());
                                json_object_object_add(obj, fr_sbuff_start(&attr_name), values);
                        } else {
                                /*
                                 *      Deal with it later on.
                                 */
                                add_single = true;
                        }
                /*
                 *      If we do have the key already, get its value array.
                 */
                } else {
                        type = json_object_get_type(vp_object);
 
                        if (type == json_type_array) {
                                values = vp_object;
                        } else {
                                /*
                                 *      We've seen one of these before, but didn't add
                                 *      it as an array the first time. Sort that out.
                                 */
                                MEM(values = json_object_new_array());
                                json_object_array_add(values, json_object_get(vp_object));
 
                                /*
                                 *      Existing key will have refcount decremented
                                 *      and will be freed if this drops to zero.
                                 */
                                json_object_object_add(obj, fr_sbuff_start(&attr_name), values);
                        }
                }
 
                if (add_single) {
                        /*
                         *      Only ever used the first time adding a new
                         *      attribute when "value_is_always_array" is not set.
                         */
                        json_object_object_add(obj, fr_sbuff_start(&attr_name), value);
                } else {
                        /*
                         *      Otherwise we're always appending to a JSON array.
                         */
                        json_object_array_add(values, value);
                }
        }
 
        return obj;
}
 
 
/** Returns a JSON array representation of a list of value pairs
 *
 * The result is a struct json_object, which should be free'd with
 * json_object_put() by the caller. Intended to only be called by
 * fr_json_afrom_pair_list().
 *
 * This function generates the "array" format, JSON_MODE_ARRAY.
 * @see fr_json_format_s
 *
 * @param[in] ctx       Talloc context.
 * @param[in] vps       a list of value pairs.
 * @param[in] format    Formatting control, must be set.
 * @return JSON object with the generated representation.
 */
static struct json_object *json_array_afrom_pair_list(TALLOC_CTX *ctx, fr_pair_list_t *vps,
                                                      fr_json_format_t const *format)
{
        fr_pair_t               *vp;
        struct json_object      *obj;
        struct json_object      *seen_attributes = NULL;
        char                    buf[FR_DICT_ATTR_MAX_NAME_LEN + 32];
 
        /* Check format and type */
        fr_assert(format);
        fr_assert(format->output_mode == JSON_MODE_ARRAY);
 
        MEM(obj = json_object_new_array());
 
        /*
         *      If attribute values should be in a list format, then keep track
         *      of the attributes we've previously seen in a JSON object.
         */
        if (format->value.value_is_always_array) {
                seen_attributes = json_object_new_object();
        }
 
        for (vp = fr_pair_list_head(vps);
             vp;
             vp = fr_pair_list_next(vps, vp)) {
                fr_sbuff_t              attr_name;
                struct json_object      *name, *value, *type_name;
                struct json_object      *values = NULL;
                struct json_object      *attrobj = NULL;
                bool                    already_seen = false;
 
                if (vp->vp_raw) continue;
 
                /*
                 *      Get attribute name and value.
                 */
                fr_sbuff_init_in(&attr_name, buf, sizeof(buf) - 1);
                if (attr_name_with_prefix(&attr_name, vp->da, format) < 0) {
                        return NULL;
                }
 
                switch (vp->vp_type) {
                case FR_TYPE_LEAF:
                        if (json_afrom_value_box(ctx, &value, vp, format) < 0) {
                                fr_strerror_const("Failed to convert attribute value to JSON object");
                                json_object_put_assert(obj);
                                return NULL;
                        }
                        break;
 
                case FR_TYPE_STRUCTURAL:
                        value = json_array_afrom_pair_list(ctx, &vp->vp_group, format);
                        break;
 
                default:
                        INVALID_TYPE;
                }
 
                if (format->value.value_is_always_array) {
                        /*
                         *      Try and find this attribute in the "seen_attributes" object. If it is
                         *      there then get the "values" array to add this attribute value to.
                         */
                        already_seen = json_object_object_get_ex(seen_attributes, fr_sbuff_start(&attr_name), &values);
                }
 
                /*
                 *      If we're adding all attributes to the toplevel array, or we're adding values
                 *      to an array of an existing attribute but haven't seen it before, then we need
                 *      to create a new JSON object for this attribute.
                 */
                if (!format->value.value_is_always_array || !already_seen) {
                        /*
                         * Create object and add it to top-level array
                         */
                        MEM(attrobj = json_object_new_object());
                        json_object_array_add(obj, attrobj);
 
                        /*
                         * Add the attribute name in the "name" key and the type in the "type" key
                         */
                        MEM(name = json_object_new_string(fr_sbuff_start(&attr_name)));
                        json_object_object_add_ex(attrobj, "name", name, JSON_C_OBJECT_KEY_IS_CONSTANT);
 
                        MEM(type_name = json_object_new_string(fr_type_to_str(vp->vp_type)));
                        json_object_object_add_ex(attrobj, "type", type_name, JSON_C_OBJECT_KEY_IS_CONSTANT);
                }
 
                if (format->value.value_is_always_array) {
                        /*
                         *      We're adding values to an array for the first copy of this attribute
                         *      that we saw. First time around we need to create an array.
                         */
                        if (!already_seen) {
                                MEM(values = json_object_new_array());
                                /*
                                 * Add "value":[] key to the attribute object
                                 */
                                json_object_object_add_ex(attrobj, "value", values, JSON_C_OBJECT_KEY_IS_CONSTANT);
 
                                /*
                                 * Also add to "seen_attributes" to check later
                                 */
                                json_object_object_add(seen_attributes, fr_sbuff_start(&attr_name), json_object_get(values));
                        }
 
                        /*
                         *      Always add the value to the respective "values" array.
                         */
                        json_object_array_add(values, value);
                } else {
                        /*
                         * This is simpler; just add a "value": key to the attribute object.
                         */
                        json_object_object_add_ex(attrobj, "value", value, JSON_C_OBJECT_KEY_IS_CONSTANT);
                }
 
        }
 
        /*
         *      No longer need the "seen_attributes" object, it was just used for tracking.
         */
        if (format->value.value_is_always_array) {
                json_object_put_assert(seen_attributes);
        }
 
        return obj;
}
 
 
/** Returns a JSON array of a list of value pairs
 *
 * The result is a struct json_object, which should be free'd with
 * json_object_put() by the caller. Intended to only be called by
 * fr_json_afrom_pair_list().
 *
 * This function generates the "array_of_values" format,
 * JSON_MODE_ARRAY_OF_VALUES, listing just the attribute values.
 * @see fr_json_format_s
 *
 * @param[in] ctx       Talloc context.
 * @param[in] vps       a list of value pairs.
 * @param[in] format    Formatting control, must be set.
 * @return JSON object with the generated representation.
 */
static struct json_object *json_value_array_afrom_pair_list(TALLOC_CTX *ctx, fr_pair_list_t *vps,
                                                            fr_json_format_t const *format)
{
        fr_pair_t               *vp;
        struct json_object      *obj;
 
        /* Check format and type */
        fr_assert(format);
        fr_assert(format->output_mode == JSON_MODE_ARRAY_OF_VALUES);
 
        MEM(obj = json_object_new_array());
 
        /*
         *      This array format is very simple - just add all the
         *      attribute values to the array in order.
         */
        for (vp = fr_pair_list_head(vps);
             vp;
             vp = fr_pair_list_next(vps, vp)) {
                struct json_object      *value;
 
                if (vp->vp_raw) continue;
 
                switch (vp->vp_type) {
                case FR_TYPE_LEAF:
                        if (json_afrom_value_box(ctx, &value, vp, format) < 0) {
                                fr_strerror_const("Failed to convert attribute value to JSON object");
                                json_object_put_assert(obj);
                                return NULL;
                        }
                        break;
 
                case FR_TYPE_STRUCTURAL:
                        value = json_value_array_afrom_pair_list(ctx, &vp->vp_group, format);
                        break;
 
                default:
                        INVALID_TYPE;
                }
 
                json_object_array_add(obj, value);
        }
 
        return obj;
}
 
 
/** Returns a JSON array of a list of value pairs
 *
 * The result is a struct json_object, which should be free'd with
 * json_object_put() by the caller. Intended to only be called by
 * fr_json_afrom_pair_list().
 *
 * This function generates the "array_of_names" format,
 * JSON_MODE_ARRAY_OF_NAMES, listing just the attribute names.
 * @see fr_json_format_s
 *
 * @param[in] ctx       Talloc context.
 * @param[in] vps       a list of value pairs.
 * @param[in] format    Formatting control, must be set.
 * @return JSON object with the generated representation.
 */
static struct json_object *json_attr_array_afrom_pair_list(TALLOC_CTX *ctx, fr_pair_list_t *vps,
                                                           fr_json_format_t const *format)
{
        fr_pair_t               *vp;
        struct json_object      *obj;
        char                    buf[FR_DICT_ATTR_MAX_NAME_LEN + 32];
 
        /* Check format and type */
        fr_assert(format);
        fr_assert(format->output_mode == JSON_MODE_ARRAY_OF_NAMES);
 
        MEM(obj = json_object_new_array());
 
        /*
         *      Add all the attribute names to the array in order.
         */
        for (vp = fr_pair_list_head(vps);
             vp;
             vp = fr_pair_list_next(vps, vp)) {
                struct json_object      *value;
                fr_sbuff_t              attr_name;
 
                if (vp->vp_raw) continue;
 
                fr_sbuff_init_in(&attr_name, buf, sizeof(buf) - 1);
                if (attr_name_with_prefix(&attr_name, vp->da, format) < 0) {
                        return NULL;
                }
                value = json_object_new_string(fr_sbuff_start(&attr_name));
 
                switch (vp->vp_type) {
                case FR_TYPE_LEAF:
                        break;
 
                case FR_TYPE_STRUCTURAL:
                        json_object_array_add(obj, value);
                        value = json_attr_array_afrom_pair_list(ctx, &vp->vp_group, format);
                        break;
 
                default:
                        INVALID_TYPE;
                }
 
                json_object_array_add(obj, value);
        }
 
        return obj;
}
 
 
/** Returns a JSON string of a list of value pairs
 *
 * The result is a talloc-ed string, freeing the string is
 * the responsibility of the caller.
 *
 * The 'format' struct contains settings to configure the output
 * JSON document format.
 * @see fr_json_format_s
 *
 * Default output, when format is NULL, is:
@verbatim
{
        "<attribute0>":{
                "type":"<type0>",
                "value":[<value0>,<value1>,<valueN>]
        },
        "<attribute1>":{
                "type":"<type1>",
                "value":[...]
        },
        "<attributeN>":{
                "type":"<typeN>",
                "value":[...]
        }
}
@endverbatim
 *
 * @param[in] ctx       Talloc context.
 * @param[in] vps       a list of value pairs.
 * @param[in] format    Formatting control, can be NULL to use default format.
 * @return JSON string representation of the value pairs
 */
char *fr_json_afrom_pair_list(TALLOC_CTX *ctx, fr_pair_list_t *vps,
                              fr_json_format_t const *format)
{
        struct json_object      *obj = NULL;
        const char              *p;
        char                    *out;
 
        if (!format) format = &default_json_format;
 
        switch (format->output_mode) {
        case JSON_MODE_OBJECT:
                MEM(obj = json_object_afrom_pair_list(ctx, vps, format));
                break;
        case JSON_MODE_OBJECT_SIMPLE:
                MEM(obj = json_smplobj_afrom_pair_list(ctx, vps, format));
                break;
        case JSON_MODE_ARRAY:
                MEM(obj = json_array_afrom_pair_list(ctx, vps, format));
                break;
        case JSON_MODE_ARRAY_OF_VALUES:
                MEM(obj = json_value_array_afrom_pair_list(ctx, vps, format));
                break;
        case JSON_MODE_ARRAY_OF_NAMES:
                MEM(obj = json_attr_array_afrom_pair_list(ctx, vps, format));
                break;
        default:
                /* This should never happen */
                fr_assert(0);
        }
 
        /*
         *      p is a buff inside obj, and will be freed
         *      when it is freed.
         */
        MEM(p = json_object_to_json_string_ext(obj, JSON_C_TO_STRING_PLAIN));
        MEM(out = talloc_typed_strdup(ctx, p));
 
        /*
         * Free the JSON structure, it's not needed any more
         */
        json_object_put_assert(obj);
 
        return out;
}