func_json.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2021-2022, Naveen Albert
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */
 
/*! \file
 *
 * \brief JSON parsing function
 *
 * \author Naveen Albert <asterisk@phreaknet.org>
 *
 * \ingroup functions
 */
 
/*** MODULEINFO
    <support_level>extended</support_level>
 ***/
 
#include "asterisk.h"
 
#include "asterisk/module.h"
#include "asterisk/channel.h"
#include "asterisk/pbx.h"
#include "asterisk/utils.h"
#include "asterisk/test.h"
#include "asterisk/app.h"
#include "asterisk/conversions.h"
 
/*** DOCUMENTATION
    <function name="JSON_DECODE" language="en_US">
        <since>
            <version>16.24.0</version>
            <version>18.10.0</version>
            <version>19.2.0</version>
        </since>
        <synopsis>
            Returns the string value of a JSON object key from a string containing a
            JSON array.
        </synopsis>
        <syntax>
            <parameter name="varname" required="true">
                <para>The name of the variable containing the JSON string to parse.</para>
            </parameter>
            <parameter name="item" required="true">
                <para>The name of the key whose value to return.</para>
                <para>Multiple keys can be listed separated by a hierarchy delimeter, which will recursively index into a nested JSON string to retrieve a specific subkey's value.</para>
            </parameter>
            <parameter name="separator" required="false">
                <para>A single character that delimits a key hierarchy for nested indexing. Default is a period (.)</para>
                <para>This value should not appear in the key or hierarchy of keys itself, except to delimit the hierarchy of keys.</para>
            </parameter>
            <parameter name="options" required="no">
                <optionlist>
                    <option name="c">
                        <para>For keys that reference a JSON array, return
                        the number of items in the array.</para>
                        <para>This option has no effect on any other type
                        of value.</para>
                    </option>
                </optionlist>
            </parameter>
        </syntax>
        <description>
            <para>The JSON_DECODE function retrieves the value of the given variable name
            and parses it as JSON, returning the value at a specified key. If the key cannot
            be found, an empty string is returned.</para>
        </description>
        <see-also>
            <ref type="function">CURL</ref>
        </see-also>
    </function>
 ***/
 
AST_THREADSTORAGE(result_buf);
 
enum json_option_flags {
    OPT_COUNT = (1 << 0),
};
 
AST_APP_OPTIONS(json_options, {
    AST_APP_OPTION('c', OPT_COUNT),
});
 
#define MAX_JSON_STACK 32
 
static int parse_node(char **key, char *currentkey, char *nestchar, int count, struct ast_json *json, char *buf, size_t len, int *depth)
{
    const char *result = NULL;
    char *previouskey;
    struct ast_json *jsonval = json;
 
    /* Prevent a huge JSON string from blowing the stack. */
    (*depth)++;
    if (*depth > MAX_JSON_STACK) {
        ast_log(LOG_WARNING, "Max JSON stack (%d) exceeded\n", MAX_JSON_STACK);
        return -1;
    }
 
    snprintf(buf, len, "%s", ""); /* clear the buffer from previous round if necessary */
    if (!json) { /* no error or warning should be thrown */
        ast_debug(1, "Could not find key '%s' in parsed JSON\n", currentkey);
        return -1;
    }
 
    switch(ast_json_typeof(jsonval)) {
        unsigned long int size;
        int r;
        double d;
 
        case AST_JSON_STRING:
            result = ast_json_string_get(jsonval);
            ast_debug(1, "Got JSON string: %s\n", result);
            ast_copy_string(buf, result, len);
            break;
        case AST_JSON_INTEGER:
            r = ast_json_integer_get(jsonval);
            ast_debug(1, "Got JSON integer: %d\n", r);
            snprintf(buf, len, "%d", r); /* the snprintf below is mutually exclusive with this one */
            break;
        case AST_JSON_REAL:
            d = ast_json_real_get(jsonval);
            ast_debug(1, "Got JSON real: %.17g\n", d);
            snprintf(buf, len, "%.17g", d); /* the snprintf below is mutually exclusive with this one */
            break;
        case AST_JSON_ARRAY:
            ast_debug(1, "Got JSON array\n");
            previouskey = currentkey;
            currentkey = strsep(key, nestchar); /* retrieve the desired index */
            size = ast_json_array_size(jsonval);
            ast_debug(1, "Parsed JSON array of size %lu, key: %s\n", size, currentkey);
            if (!currentkey) { /* this is the end, so just dump the array */
                if (count) {
                    ast_debug(1, "No key on which to index in the array, so returning count: %lu\n", size);
                    snprintf(buf, len, "%lu", size);
                    return 0;
                } else {
                    char *result2 = ast_json_dump_string(jsonval);
                    ast_debug(1, "No key on which to index in the array, so dumping '%s' array\n", previouskey);
                    ast_copy_string(buf, result2, len);
                    ast_json_free(result2);
                }
            } else if (ast_str_to_int(currentkey, &r) || r < 0) {
                ast_debug(1, "Requested index '%s' is not numeric or is invalid\n", currentkey);
            } else if (r >= size) {
                ast_debug(1, "Requested index '%d' does not exist in parsed array\n", r);
            } else {
                ast_debug(1, "Recursing on index %d in array\n", r);
                if (parse_node(key, currentkey, nestchar, count, ast_json_array_get(jsonval, r), buf, len, depth)) { /* recurse on this node */
                    return -1;
                }
            }
            break;
        case AST_JSON_TRUE:
        case AST_JSON_FALSE:
            r = ast_json_is_true(jsonval);
            ast_debug(1, "Got JSON %s for key %s\n", r ? "true" : "false", currentkey);
            snprintf(buf, len, "%d", r); /* the snprintf below is mutually exclusive with this one */
            break;
        case AST_JSON_NULL:
            ast_debug(1, "Got JSON null for key %s\n", currentkey);
            break;
        case AST_JSON_OBJECT:
            ast_debug(1, "Got generic JSON object for key %s\n", currentkey);
            previouskey = currentkey;
            currentkey = strsep(key, nestchar); /* retrieve the desired index */
            if (!currentkey) { /* this is the end, so just dump the object */
                char *result2 = ast_json_dump_string(jsonval);
                ast_copy_string(buf, result2, len);
                ast_json_free(result2);
            } else {
                ast_debug(1, "Recursing on object (key was '%s' and is now '%s')\n", previouskey, currentkey);
                if (parse_node(key, currentkey, nestchar, count, ast_json_object_get(jsonval, currentkey), buf, len, depth)) { /* recurse on this node */
                    return -1;
                }
            }
            break;
        default:
            ast_log(LOG_WARNING, "Got unsuported type %d\n", ast_json_typeof(jsonval));
            return -1;
    }
    return 0;
}
 
static int json_decode_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
{
    int count = 0;
    struct ast_flags flags = {0};
    struct ast_json *json = NULL, *start = NULL;
    char *nestchar = "."; /* default delimeter for nesting key indexing is . */
    int index, res, depth = 0;
 
    AST_DECLARE_APP_ARGS(args,
        AST_APP_ARG(varname);
        AST_APP_ARG(key);
        AST_APP_ARG(nestchar);
        AST_APP_ARG(options);
    );
    char *varsubst, *key, *currentkey, *nextkey, *firstkey, *tmp;
    struct ast_str *str = ast_str_thread_get(&result_buf, 16);
 
    AST_STANDARD_APP_ARGS(args, data);
 
    if (!ast_strlen_zero(args.options)) {
        ast_app_parse_options(json_options, &flags, NULL, args.options);
        if (ast_test_flag(&flags, OPT_COUNT)) {
            count = 1;
        }
    }
 
    if (ast_strlen_zero(args.varname)) {
        ast_log(LOG_WARNING, "%s requires a variable name\n", cmd);
        return -1;
    }
 
    if (ast_strlen_zero(args.key)) {
        ast_log(LOG_WARNING, "%s requires a key\n", cmd);
        return -1;
    }
 
    key = ast_strdupa(args.key);
    if (!ast_strlen_zero(args.nestchar)) {
        int seplen = strlen(args.nestchar);
        if (seplen != 1) {
            ast_log(LOG_WARNING, "Nesting separator '%s' has length %d and is invalid (must be a single character)\n", args.nestchar, seplen);
        } else {
            nestchar = args.nestchar;
        }
    }
 
    varsubst = ast_alloca(strlen(args.varname) + 4); /* +4 for ${} and null terminator */
    if (!varsubst) {
        ast_log(LOG_ERROR, "Failed to allocate string\n");
        return -1;
    }
    sprintf(varsubst, "${%s}", args.varname); /* safe, because of the above allocation */
    ast_str_substitute_variables(&str, 0, chan, varsubst);
 
    ast_debug(1, "Parsing JSON using nesting delimeter '%s'\n", nestchar);
 
    if (ast_str_strlen(str) == 0) {
        ast_debug(1, "Variable '%s' contains no data, nothing to search!\n", args.varname);
        return -1; /* empty json string */
    }
 
    /* allow for multiple key nesting */
    currentkey = key;
    firstkey = ast_strdupa(currentkey);
    tmp = strstr(firstkey, nestchar);
    if (tmp) {
        *tmp = '\0';
    }
 
    /* parse a string as JSON */
    ast_debug(1, "Parsing JSON: %s (key: '%s')\n", ast_str_buffer(str), currentkey);
    if (ast_strlen_zero(currentkey)) {
        ast_debug(1, "Empty JSON key\n");
        return -1;
    }
    if (ast_str_strlen(str) == 0) {
        ast_debug(1, "JSON node '%s', contains no data, nothing to search!\n", currentkey);
        return -1; /* empty json string */
    }
 
    json = ast_json_load_str(str, NULL);
    if (!json) {
        ast_log(LOG_WARNING, "Failed to parse as JSON: %s\n", ast_str_buffer(str));
        return -1;
    }
 
    /* parse the JSON object, potentially recursively */
    nextkey = strsep(&key, nestchar);
    if (ast_json_is_object(json)) {
        start = ast_json_object_get(json, firstkey);
    } else {
        if (ast_str_to_int(currentkey, &index)) {
            ast_debug(1, "Requested index '%s' is not numeric or is invalid\n", currentkey);
            return -1;
        }
        start = ast_json_array_get(json, index);
    }
 
    res = parse_node(&key, nextkey, nestchar, count, start, buf, len, &depth);
    ast_json_unref(json);
    return res;
}
 
static struct ast_custom_function json_decode_function = {
    .name = "JSON_DECODE",
    .read = json_decode_read,
};
 
#ifdef TEST_FRAMEWORK
AST_TEST_DEFINE(test_JSON_DECODE)
{
    int i, res = AST_TEST_PASS;
    struct ast_channel *chan; /* dummy channel */
    struct ast_str *str; /* fancy string for holding comparing value */
 
    const char *test_strings[][6] = {
        {"{\"myboolean\": true, \"state\": \"USA\"}", "", "myboolean", "1"},
        {"{\"myboolean\": false, \"state\": \"USA\"}", "", "myboolean", "0"},
        {"{\"myreal\": 1E+2, \"state\": \"USA\"}", "", "myreal", "100"},
        {"{\"myreal\": 1.23, \"state\": \"USA\"}", "", "myreal", "1.23"},
        {"{\"myarray\": [[1]], \"state\": \"USA\"}", "", "myarray.0.0", "1"},
        {"{\"myarray\": [null], \"state\": \"USA\"}", "", "myarray.0", ""},
        {"{\"myarray\": [0, 1], \"state\": \"USA\"}", "", "myarray", "[0,1]"},
        {"[0, 1]", "", "", ""},
        {"[0, 1]", "", "0", "0"},
        {"[0, 1]", "", "foo", ""},
        {"{\"mynull\": null, \"state\": \"USA\"}", "", "mynull", ""},
        {"{\"city\": \"Anytown\", \"state\": \"USA\"}", "", "city", "Anytown"},
        {"{\"city\": \"Anytown\", \"state\": \"USA\"}", "", "state", "USA"},
        {"{\"city\": \"Anytown\", \"state\": \"USA\"}", "", "blah", ""},
        {"{\"key1\": \"123\", \"key2\": \"456\"}", "", "key1", "123"},
        {"{\"key1\": 123, \"key2\": 456}", "", "key1", "123"},
        {"{ \"path\": { \"to\": { \"elem\": \"someVar\" } } }", "/", "path/to/elem", "someVar"},
        {"{ \"path\": { \"to\": { \"elem\": \"someVar\" } } }", "", "path.to.elem2", ""},
        {"{ \"path\": { \"to\": { \"arr\": [ \"item0\", \"item1\" ] } } }", "/", "path/to/arr/2", ""}, /* nonexistent index */
        {"{ \"path\": { \"to\": { \"arr\": [ \"item0\", \"item1\" ] } } }", "/", "path/to/arr/-1", ""}, /* bogus index */
        {"{ \"path\": { \"to\": { \"arr\": [ \"item0\", \"item1\" ] } } }", "/", "path/to/arr/test", ""}, /* bogus index */
        {"{ \"path\": { \"to\": { \"arr\": [ \"item0\", \"item1\" ] } } }", "", "path.to.arr.test.test2.subkey", ""}, /* bogus index */
        {"{ \"path\": { \"to\": { \"arr\": [ \"item0\", \"item1\" ] } } }", ",c", "path.to.arr", "2"}, /* test count */
        {"{ \"path\": { \"to\": { \"arr\": [ \"item0\", \"item1\" ] } } }", "", "path.to.arr", "[\"item0\",\"item1\"]"},
        {"{ \"path\": { \"to\": { \"arr\": [ \"item0\", \"item1\" ] } } }", ".", "path.to.arr.1", "item1"},
        {"{ \"path\": { \"to\": { \"arr\": [ \"item0\", \"item1\" ] } } }", "/", "path/to/arr", "[\"item0\",\"item1\"]"},
        {"{ \"path\": { \"to\": { \"arr\": [ \"item0\", \"item1\" ] } } }", "/", "path/to/arr/1", "item1"},
        {"{ \"path\": { \"to\": { \"arr\": [ {\"name\": \"John Smith\", \"phone\": \"123\"}, {\"name\": \"Jane Doe\", \"phone\": \"234\"} ] } } }", ",c", "path.to.arr.0.name", "John Smith"},
        {"{ \"path\": { \"to\": { \"arr\": [ {\"name\": 1, \"phone\": 123}, {\"name\": 2, \"phone\": 234} ] } } }", ",c", "path.to.arr.0.name", "1"},
        {"{ \"path\": { \"to\": { \"arr\": [ {\"name\": [ \"item11\", \"item12\" ], \"phone\": [ \"item13\", \"item14\" ]}, {\"name\": [ \"item15\", \"item16\" ], \"phone\": [ \"item17\", \"item18\" ]} ] } } }", ",c", "path.to.arr.0.name.1", "item12"},
        {"{ \"startId\": \"foobar\", \"abcd\": { \"id\": \"abcd\", \"type\": \"EXT\" }, \"bcde\": { \"id\": \"bcde\", \"type\": \"CONDITION\" }, \"defg\": { \"id\": \"defg\", \"type\": \"EXT\" }, \"efgh\": { \"id\": \"efgh\", \"type\": \"VOICEMAIL\" } }", "", "bcde", "{\"id\":\"bcde\",\"type\":\"CONDITION\"}"},
    };
 
    switch (cmd) {
    case TEST_INIT:
        info->name = "func_JSON_DECODE";
        info->category = "/funcs/func_json/";
        info->summary = "Test JSON_DECODE function";
        info->description = "Verify JSON_DECODE behavior";
        return AST_TEST_NOT_RUN;
    case TEST_EXECUTE:
        break;
    }
 
    if (!(chan = ast_dummy_channel_alloc())) {
        ast_test_status_update(test, "Unable to allocate dummy channel\n");
        return AST_TEST_FAIL;
    }
 
    if (!(str = ast_str_create(64))) {
        ast_test_status_update(test, "Unable to allocate dynamic string buffer\n");
        ast_channel_release(chan);
        return AST_TEST_FAIL;
    }
 
    for (i = 0; i < ARRAY_LEN(test_strings); i++) {
        char tmp[512];
 
        struct ast_var_t *var = ast_var_assign("test_string", test_strings[i][0]);
        if (!var) {
            ast_test_status_update(test, "Unable to allocate variable\n");
            ast_free(str);
            ast_channel_release(chan);
            return AST_TEST_FAIL;
        }
 
        AST_LIST_INSERT_HEAD(ast_channel_varshead(chan), var, entries);
 
        snprintf(tmp, sizeof(tmp), "${JSON_DECODE(%s,%s,%s)}", "test_string", test_strings[i][2], test_strings[i][1]);
 
        ast_str_substitute_variables(&str, 0, chan, tmp);
        if (strcmp(test_strings[i][3], ast_str_buffer(str))) {
            ast_test_status_update(test, "Format string '%s' substituted to '%s' (key: %s). Expected '%s'.\n", test_strings[i][0], ast_str_buffer(str), test_strings[i][2], test_strings[i][3]);
            res = AST_TEST_FAIL;
        }
    }
 
    ast_free(str);
    ast_channel_release(chan);
 
    return res;
}
#endif
 
static int unload_module(void)
{
    int res;
 
#ifdef TEST_FRAMEWORK
    AST_TEST_UNREGISTER(test_JSON_DECODE);
#endif
    res = ast_custom_function_unregister(&json_decode_function);
 
    return res;
}
 
static int load_module(void)
{
    int res;
 
#ifdef TEST_FRAMEWORK
    AST_TEST_REGISTER(test_JSON_DECODE);
#endif
    res = ast_custom_function_register(&json_decode_function);
 
    return res;
}
 
AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "JSON decoding function");