res_ari.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2012 - 2013, Digium, Inc.
 *
 * David M. Lee, II <dlee@digium.com>
 *
 * 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 HTTP binding for the Stasis API
 * \author David M. Lee, II <dlee@digium.com>
 *
 * The API itself is documented using <a
 * href="https://developers.helloreverb.com/swagger/">Swagger</a>, a lightweight
 * mechanism for documenting RESTful API's using JSON. This allows us to use <a
 * href="https://github.com/wordnik/swagger-ui">swagger-ui</a> to provide
 * executable documentation for the API, generate client bindings in different
 * <a href="https://github.com/asterisk/asterisk_rest_libraries">languages</a>,
 * and generate a lot of the boilerplate code for implementing the RESTful
 * bindings. The API docs live in the \c rest-api/ directory.
 *
 * The RESTful bindings are generated from the Swagger API docs using a set of
 * <a href="http://mustache.github.io/mustache.5.html">Mustache</a> templates.
 * The code generator is written in Python, and uses the Python implementation
 * <a href="https://github.com/defunkt/pystache">pystache</a>. Pystache has no
 * dependencies, and be installed easily using \c pip. Code generation code
 * lives in \c rest-api-templates/.
 *
 * The generated code reduces a lot of boilerplate when it comes to handling
 * HTTP requests. It also helps us have greater consistency in the REST API.
 *
 * The structure of the generated code is:
 *
 *  - res/ari/resource_{resource}.h
 *    - For each operation in the resource, a generated argument structure
 *      (holding the parsed arguments from the request) and function
 *      declarations (to implement in res/ari/resource_{resource}.c)
 *  - res_ari_{resource}.c
 *    - A set of \ref stasis_rest_callback functions, which glue the two
 *      together. They parse out path variables and request parameters to
 *      populate a specific \c *_args which is passed to the specific request
 *      handler (in res/ari/resource_{resource}.c)
 *    - A tree of \ref stasis_rest_handlers for routing requests to its
 *      \ref stasis_rest_callback
 *
 * The basic flow of an HTTP request is:
 *
 *  - ast_ari_callback()
 *    1. Initial request validation
 *    2. Routes as either a doc request (ast_ari_get_docs) or API
 *       request (ast_ari_invoke)
 *       - ast_ari_invoke()
 *         1. Further request validation
 *         2. Routes the request through the tree of generated
 *            \ref stasis_rest_handlers.
 *         3. Dispatch to the generated callback
 *            - \c ast_ari_*_cb
 *              1. Populate \c *_args struct with path and get params
 *              2. Invoke the request handler
 *    3. Validates and sends response
 */
 
/*** MODULEINFO
    <depend type="module">res_http_websocket</depend>
    <depend type="module">res_stasis</depend>
    <support_level>core</support_level>
 ***/
 
/*** DOCUMENTATION
    <configInfo name="res_ari" language="en_US">
        <synopsis>HTTP binding for the Stasis API</synopsis>
        <configFile name="ari.conf">
            <configObject name="general">
                <since>
                    <version>12.0.0</version>
                </since>
                <synopsis>General configuration settings</synopsis>
                <configOption name="enabled">
                    <since>
                        <version>12.0.0</version>
                    </since>
                    <synopsis>Enable/disable the ARI module</synopsis>
                    <description>
                        <para>This option enables or disables the ARI module.</para>
                        <note>
                            <para>ARI uses Asterisk's HTTP server, which must also be enabled in <filename>http.conf</filename>.</para>
                        </note>
                    </description>
                    <see-also>
                        <ref type="filename">http.conf</ref>
                        <ref type="link">https://docs.asterisk.org/Configuration/Core-Configuration/Asterisk-Builtin-mini-HTTP-Server/</ref>
                    </see-also>
                </configOption>
                <configOption name="websocket_write_timeout" default="100">
                    <since>
                        <version>11.11.0</version>
                        <version>12.4.0</version>
                    </since>
                    <synopsis>The timeout (in milliseconds) to set on WebSocket connections.</synopsis>
                    <description>
                        <para>If a websocket connection accepts input slowly, the timeout
                        for writes to it can be increased to keep it from being disconnected.
                        Value is in milliseconds.</para>
                    </description>
                </configOption>
                <configOption name="pretty">
                    <since>
                        <version>12.0.0</version>
                    </since>
                    <synopsis>Responses from ARI are formatted to be human readable</synopsis>
                </configOption>
                <configOption name="auth_realm">
                    <since>
                        <version>12.0.0</version>
                    </since>
                    <synopsis>Realm to use for authentication. Defaults to Asterisk REST Interface.</synopsis>
                </configOption>
                <configOption name="allowed_origins">
                    <since>
                        <version>12.0.0</version>
                    </since>
                    <synopsis>Comma separated list of allowed origins, for Cross-Origin Resource Sharing. May be set to * to allow all origins.</synopsis>
                </configOption>
                <configOption name="channelvars">
                    <since>
                        <version>14.2.0</version>
                    </since>
                    <synopsis>Comma separated list of channel variables to display in channel json.</synopsis>
                </configOption>
            </configObject>
 
            <configObject name="user">
                <since>
                    <version>12.0.0</version>
                </since>
                <synopsis>Per-user configuration settings</synopsis>
                <configOption name="type">
                    <since>
                        <version>13.30.0</version>
                        <version>16.7.0</version>
                        <version>17.1.0</version>
                    </since>
                    <synopsis>Define this configuration section as a user.</synopsis>
                    <description>
                        <enumlist>
                            <enum name="user"><para>Configure this section as a <replaceable>user</replaceable></para></enum>
                        </enumlist>
                    </description>
                </configOption>
                <configOption name="read_only">
                    <since>
                        <version>13.30.0</version>
                        <version>16.7.0</version>
                        <version>17.1.0</version>
                    </since>
                    <synopsis>When set to yes, user is only authorized for read-only requests</synopsis>
                </configOption>
                <configOption name="password">
                    <since>
                        <version>13.30.0</version>
                        <version>16.7.0</version>
                        <version>17.1.0</version>
                    </since>
                    <synopsis>Crypted or plaintext password (see password_format)</synopsis>
                </configOption>
                <configOption name="password_format">
                    <since>
                        <version>12.0.0</version>
                    </since>
                    <synopsis>password_format may be set to plain (the default) or crypt. When set to crypt, crypt(3) is used to validate the password. A crypted password can be generated using mkpasswd -m sha-512. When set to plain, the password is in plaintext</synopsis>
                </configOption>
            </configObject>
        </configFile>
    </configInfo>
***/
 
#include "asterisk.h"
 
#include "ari/internal.h"
#include "ari/ari_websockets.h"
#include "asterisk/ari.h"
#include "asterisk/astobj2.h"
#include "asterisk/module.h"
#include "asterisk/paths.h"
#include "asterisk/stasis_app.h"
 
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
 
/*! \brief Helper function to check if module is enabled. */
static int is_enabled(void)
{
    RAII_VAR(struct ast_ari_conf *, cfg, ast_ari_config_get(), ao2_cleanup);
    return cfg && cfg->general && cfg->general->enabled;
}
 
/*! Lock for \ref root_handler */
static ast_mutex_t root_handler_lock;
 
/*! Handler for root RESTful resource. */
static struct stasis_rest_handlers *root_handler;
 
/*! Pre-defined message for allocation failures. */
static struct ast_json *oom_json;
 
/*! \brief Callback for the root URI. */
static int ast_ari_callback(struct ast_tcptls_session_instance *ser,
    const struct ast_http_uri *urih, const char *uri,
    enum ast_http_method method, struct ast_variable *get_params,
    struct ast_variable *headers);
 
static struct ast_http_uri http_uri = {
    .callback = ast_ari_callback,
    .description = "Asterisk RESTful API",
    .uri = "ari",
    .has_subtree = 1,
    .data = NULL,
    .key = __FILE__,
    .no_decode_uri = 1,
};
 
struct ast_json *ast_ari_oom_json(void)
{
    return oom_json;
}
 
int ast_ari_add_handler(struct stasis_rest_handlers *handler)
{
    RAII_VAR(struct stasis_rest_handlers *, new_handler, NULL, ao2_cleanup);
    size_t old_size, new_size;
 
    SCOPED_MUTEX(lock, &root_handler_lock);
 
    old_size = sizeof(*new_handler) + root_handler->num_children * sizeof(handler);
    new_size = old_size + sizeof(handler);
 
    new_handler = ao2_alloc(new_size, NULL);
    if (!new_handler) {
        return -1;
    }
    memcpy(new_handler, root_handler, old_size);
    new_handler->children[new_handler->num_children++] = handler;
 
    ao2_cleanup(root_handler);
    ao2_ref(new_handler, +1);
    root_handler = new_handler;
    return 0;
}
 
int ast_ari_remove_handler(struct stasis_rest_handlers *handler)
{
    struct stasis_rest_handlers *new_handler;
    size_t size;
    size_t i;
    size_t j;
 
    ast_assert(root_handler != NULL);
 
    ast_mutex_lock(&root_handler_lock);
    size = sizeof(*new_handler) + root_handler->num_children * sizeof(handler);
 
    new_handler = ao2_alloc(size, NULL);
    if (!new_handler) {
        ast_mutex_unlock(&root_handler_lock);
        return -1;
    }
 
    /* Create replacement root_handler less the handler to remove. */
    memcpy(new_handler, root_handler, sizeof(*new_handler));
    for (i = 0, j = 0; i < root_handler->num_children; ++i) {
        if (root_handler->children[i] == handler) {
            continue;
        }
        new_handler->children[j++] = root_handler->children[i];
    }
    new_handler->num_children = j;
 
    /* Replace the old root_handler with the new. */
    ao2_cleanup(root_handler);
    root_handler = new_handler;
 
    ast_mutex_unlock(&root_handler_lock);
    return 0;
}
 
static struct stasis_rest_handlers *get_root_handler(void)
{
    SCOPED_MUTEX(lock, &root_handler_lock);
    ao2_ref(root_handler, +1);
    return root_handler;
}
 
static struct stasis_rest_handlers *root_handler_create(void)
{
    RAII_VAR(struct stasis_rest_handlers *, handler, NULL, ao2_cleanup);
 
    handler = ao2_alloc(sizeof(*handler), NULL);
    if (!handler) {
        return NULL;
    }
    handler->path_segment = "ari";
 
    ao2_ref(handler, +1);
    return handler;
}
 
void ast_ari_response_error(struct ast_ari_response *response,
                int response_code,
                const char *response_text,
                const char *message_fmt, ...)
{
    RAII_VAR(struct ast_json *, message, NULL, ast_json_unref);
    va_list ap;
 
    va_start(ap, message_fmt);
    message = ast_json_vstringf(message_fmt, ap);
    va_end(ap);
    response->message = ast_json_pack("{s: o}",
                      "message", ast_json_ref(message));
    response->response_code = response_code;
    response->response_text = response_text;
}
 
void ast_ari_response_ok(struct ast_ari_response *response,
                 struct ast_json *message)
{
    response->message = message;
    response->response_code = 200;
    response->response_text = "OK";
}
 
void ast_ari_response_no_content(struct ast_ari_response *response)
{
    response->message = ast_json_null();
    response->response_code = 204;
    response->response_text = "No Content";
}
 
void ast_ari_response_accepted(struct ast_ari_response *response)
{
    response->message = ast_json_null();
    response->response_code = 202;
    response->response_text = "Accepted";
}
 
void ast_ari_response_alloc_failed(struct ast_ari_response *response)
{
    response->message = ast_json_ref(oom_json);
    response->response_code = 500;
    response->response_text = "Internal Server Error";
}
 
void ast_ari_response_created(struct ast_ari_response *response,
    const char *url, struct ast_json *message)
{
    RAII_VAR(struct stasis_rest_handlers *, root, get_root_handler(), ao2_cleanup);
    response->message = message;
    response->response_code = 201;
    response->response_text = "Created";
    ast_str_append(&response->headers, 0, "Location: /%s%s\r\n", root->path_segment, url);
}
 
static void add_allow_header(struct stasis_rest_handlers *handler,
                 struct ast_ari_response *response)
{
    enum ast_http_method m;
    ast_str_append(&response->headers, 0,
               "Allow: OPTIONS");
    for (m = 0; m < AST_HTTP_MAX_METHOD; ++m) {
        if (handler->callbacks[m] != NULL) {
            ast_str_append(&response->headers, 0,
                       ",%s", ast_get_http_method(m));
        }
    }
    ast_str_append(&response->headers, 0, "\r\n");
}
 
static int origin_allowed(const char *origin)
{
    RAII_VAR(struct ast_ari_conf *, cfg, ast_ari_config_get(), ao2_cleanup);
 
    char *allowed = ast_strdupa(cfg->general->allowed_origins);
    char *current;
 
    while ((current = strsep(&allowed, ","))) {
        if (!strcmp(current, "*")) {
            return 1;
        }
 
        if (!strcmp(current, origin)) {
            return 1;
        }
    }
 
    return 0;
}
 
#define ACR_METHOD "Access-Control-Request-Method"
#define ACR_HEADERS "Access-Control-Request-Headers"
#define ACA_METHODS "Access-Control-Allow-Methods"
#define ACA_HEADERS "Access-Control-Allow-Headers"
 
/*!
 * \brief Handle OPTIONS request, mainly for CORS preflight requests.
 *
 * Some browsers will send this prior to non-simple methods (i.e. DELETE).
 * See http://www.w3.org/TR/cors/ for the spec. Especially section 6.2.
 */
static void handle_options(struct stasis_rest_handlers *handler,
               struct ast_variable *headers,
               struct ast_ari_response *response)
{
    struct ast_variable *header;
    char const *acr_method = NULL;
    char const *acr_headers = NULL;
    char const *origin = NULL;
 
    RAII_VAR(struct ast_str *, allow, NULL, ast_free);
    enum ast_http_method m;
    int allowed = 0;
 
    /* Regular OPTIONS response */
    add_allow_header(handler, response);
    ast_ari_response_no_content(response);
 
    /* Parse CORS headers */
    for (header = headers; header != NULL; header = header->next) {
        if (strcmp(ACR_METHOD, header->name) == 0) {
            acr_method = header->value;
        } else if (strcmp(ACR_HEADERS, header->name) == 0) {
            acr_headers = header->value;
        } else if (strcmp("Origin", header->name) == 0) {
            origin = header->value;
        }
    }
 
    /* CORS 6.2, #1 - "If the Origin header is not present terminate this
     * set of steps."
     */
    if (origin == NULL) {
        return;
    }
 
    /* CORS 6.2, #2 - "If the value of the Origin header is not a
     * case-sensitive match for any of the values in list of origins do not
     * set any additional headers and terminate this set of steps.
     *
     * Always matching is acceptable since the list of origins can be
     * unbounded.
     *
     * The Origin header can only contain a single origin as the user agent
     * will not follow redirects."
     */
    if (!origin_allowed(origin)) {
        ast_log(LOG_NOTICE, "Origin header '%s' does not match an allowed origin.\n", origin);
        return;
    }
 
    /* CORS 6.2, #3 - "If there is no Access-Control-Request-Method header
     * or if parsing failed, do not set any additional headers and terminate
     * this set of steps."
     */
    if (acr_method == NULL) {
        return;
    }
 
    /* CORS 6.2, #4 - "If there are no Access-Control-Request-Headers
     * headers let header field-names be the empty list."
     */
    if (acr_headers == NULL) {
        acr_headers = "";
    }
 
    /* CORS 6.2, #5 - "If method is not a case-sensitive match for any of
     * the values in list of methods do not set any additional headers and
     * terminate this set of steps."
     */
    allow = ast_str_create(20);
 
    if (!allow) {
        ast_ari_response_alloc_failed(response);
        return;
    }
 
    /* Go ahead and build the ACA_METHODS header at the same time */
    for (m = 0; m < AST_HTTP_MAX_METHOD; ++m) {
        if (handler->callbacks[m] != NULL) {
            char const *m_str = ast_get_http_method(m);
            if (strcmp(m_str, acr_method) == 0) {
                allowed = 1;
            }
            ast_str_append(&allow, 0, ",%s", m_str);
        }
    }
 
    if (!allowed) {
        return;
    }
 
    /* CORS 6.2 #6 - "If any of the header field-names is not a ASCII
     * case-insensitive match for any of the values in list of headers do
     * not set any additional headers and terminate this set of steps.
     *
     * Note: Always matching is acceptable since the list of headers can be
     * unbounded."
     */
 
    /* CORS 6.2 #7 - "If the resource supports credentials add a single
     * Access-Control-Allow-Origin header, with the value of the Origin
     * header as value, and add a single Access-Control-Allow-Credentials
     * header with the case-sensitive string "true" as value."
     *
     * Added by process_cors_request() earlier in the request.
     */
 
    /* CORS 6.2 #8 - "Optionally add a single Access-Control-Max-Age
     * header..."
     */
 
    /* CORS 6.2 #9 - "Add one or more Access-Control-Allow-Methods headers
     * consisting of (a subset of) the list of methods."
     */
    ast_str_append(&response->headers, 0, "%s: OPTIONS%s\r\n",
               ACA_METHODS, ast_str_buffer(allow));
 
 
    /* CORS 6.2, #10 - "Add one or more Access-Control-Allow-Headers headers
     * consisting of (a subset of) the list of headers.
     *
     * Since the list of headers can be unbounded simply returning headers
     * can be enough."
     */
    if (!ast_strlen_zero(acr_headers)) {
        ast_str_append(&response->headers, 0, "%s: %s\r\n",
                   ACA_HEADERS, acr_headers);
    }
}
 
/*!
 * \brief Authenticate a <code>?api_key=userid:password</code>
 *
 * \param api_key API key query parameter
 * \return User object for the authenticated user.
 * \retval NULL if authentication failed.
 */
static struct ast_ari_conf_user *authenticate_api_key(const char *api_key)
{
    RAII_VAR(char *, copy, NULL, ast_free);
    char *username;
    char *password;
 
    password = copy = ast_strdup(api_key);
    if (!copy) {
        return NULL;
    }
 
    username = strsep(&password, ":");
    if (!password) {
        ast_log(LOG_WARNING, "Invalid api_key\n");
        return NULL;
    }
 
    return ast_ari_config_validate_user(username, password);
}
 
/*!
 * \brief Authenticate an HTTP request.
 *
 * \param get_params GET parameters of the request.
 * \param headers HTTP headers.
 * \return User object for the authenticated user.
 * \retval NULL if authentication failed.
 */
static struct ast_ari_conf_user *authenticate_user(struct ast_variable *get_params,
    struct ast_variable *headers)
{
    RAII_VAR(struct ast_http_auth *, http_auth, NULL, ao2_cleanup);
    struct ast_variable *v;
 
    /* HTTP Basic authentication */
    http_auth = ast_http_get_auth(headers);
    if (http_auth) {
        return ast_ari_config_validate_user(http_auth->userid,
            http_auth->password);
    }
 
    /* ?api_key authentication */
    for (v = get_params; v; v = v->next) {
        if (strcasecmp("api_key", v->name) == 0) {
            return authenticate_api_key(v->value);
        }
    }
 
    return NULL;
}
 
static void remove_trailing_slash(const char *uri,
                  struct ast_ari_response *response)
{
    char *slashless = ast_strdupa(uri);
    slashless[strlen(slashless) - 1] = '\0';
 
    /* While it's tempting to redirect the client to the slashless URL,
     * that is problematic. A 302 Found is the most appropriate response,
     * but most clients issue a GET on the location you give them,
     * regardless of the method of the original request.
     *
     * While there are some ways around this, it gets into a lot of client
     * specific behavior and corner cases in the HTTP standard. There's also
     * very little practical benefit of redirecting; only GET and HEAD can
     * be redirected automagically; all other requests "MUST NOT
     * automatically redirect the request unless it can be confirmed by the
     * user, since this might change the conditions under which the request
     * was issued."
     *
     * Given all of that, a 404 with a nice message telling them what to do
     * is probably our best bet.
     */
    ast_ari_response_error(response, 404, "Not Found",
        "ARI URLs do not end with a slash. Try /ari/%s", slashless);
}
 
enum ast_ari_invoke_result ast_ari_invoke(struct ast_tcptls_session_instance *ser,
    enum ast_ari_invoke_source source, const struct ast_http_uri *urih,
    const char *uri, enum ast_http_method method,
    struct ast_variable *get_params, struct ast_variable *headers,
    struct ast_json *body, struct ast_ari_response *response)
{
    RAII_VAR(struct stasis_rest_handlers *, root, NULL, ao2_cleanup);
    struct stasis_rest_handlers *handler = NULL;
    struct stasis_rest_handlers *wildcard_handler = NULL;
    RAII_VAR(struct ast_variable *, path_vars, NULL, ast_variables_destroy);
    RAII_VAR(struct ast_ari_conf_user *, user, NULL, ao2_cleanup);
    RAII_VAR(struct ast_ari_conf *, conf, ast_ari_config_get(), ao2_cleanup);
 
    char *path = ast_strdupa(uri);
    char *path_segment = NULL;
    stasis_rest_callback callback;
    SCOPE_ENTER(3, "Request: %s %s, path:%s\n", ast_get_http_method(method), uri, path);
 
 
    if (!conf || !conf->general) {
        if (ser && source == ARI_INVOKE_SOURCE_REST) {
            ast_http_request_close_on_completion(ser);
        }
        ast_ari_response_error(response, 500, "Server Error", "URI handler config missing");
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CLOSE, "Response: %d : %s\n",
            response->response_code, response->response_text);
    }
 
    user = authenticate_user(get_params, headers);
 
    if (!user && source == ARI_INVOKE_SOURCE_REST) {
        /* Per RFC 2617, section 1.2: The 401 (Unauthorized) response
         * message is used by an origin server to challenge the
         * authorization of a user agent. This response MUST include a
         * WWW-Authenticate header field containing at least one
         * challenge applicable to the requested resource.
         */
        ast_ari_response_error(response, 401, "Unauthorized", "Authentication required");
 
        /* Section 1.2:
         *   realm       = "realm" "=" realm-value
         *   realm-value = quoted-string
         * Section 2:
         *   challenge   = "Basic" realm
         */
        ast_str_append(&response->headers, 0,
            "WWW-Authenticate: Basic realm=\"%s\"\r\n",
            conf->general->auth_realm);
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CONTINUE, "Response: %d : %s\n",
            response->response_code, response->response_text);
    } else if (!ast_fully_booted) {
        ast_ari_response_error(response, 503, "Service Unavailable", "Asterisk not booted");
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CLOSE, "Response: %d : %s\n",
            response->response_code, response->response_text);
    } else if (user && user->read_only && method != AST_HTTP_GET && method != AST_HTTP_OPTIONS) {
        ast_ari_response_error(response, 403, "Forbidden", "Write access denied");
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CONTINUE, "Response: %d : %s\n",
            response->response_code, response->response_text);
    } else if (ast_ends_with(uri, "/")) {
        remove_trailing_slash(uri, response);
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CONTINUE, "Response: %d : %s\n",
            response->response_code, response->response_text);
    } else if (ast_begins_with(uri, "api-docs/")) {
        /* Serving up API docs */
        if (method != AST_HTTP_GET) {
            ast_ari_response_error(response, 405, "Method Not Allowed", "Unsupported method");
        } else {
            if (urih) {
                /* Skip the api-docs prefix */
                ast_ari_get_docs(strchr(uri, '/') + 1, urih->prefix, headers, response);
            } else {
                /*
                 * If we were invoked without a urih, we're probably
                 * being called from the websocket so just use the
                 * default prefix.  It's filled in by ast_http_uri_link().
                 */
                ast_ari_get_docs(strchr(uri, '/') + 1, http_uri.prefix, headers, response);
            }
        }
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CONTINUE, "Response: %d : %s\n",
            response->response_code, response->response_text);
    }
 
    root = handler = get_root_handler();
    ast_assert(root != NULL);
 
    while ((path_segment = strsep(&path, "/")) && (strlen(path_segment) > 0)) {
        struct stasis_rest_handlers *found_handler = NULL;
        int i;
        SCOPE_ENTER(4, "Finding handler for path segment %s\n", path_segment);
 
        ast_uri_decode(path_segment, ast_uri_http_legacy);
 
        for (i = 0; found_handler == NULL && i < handler->num_children; ++i) {
            struct stasis_rest_handlers *child = handler->children[i];
            SCOPE_ENTER(5, "Checking handler path segment %s\n", child->path_segment);
 
            if (child->is_wildcard) {
                /* Record the path variable */
                struct ast_variable *path_var = ast_variable_new(child->path_segment, path_segment, __FILE__);
                path_var->next = path_vars;
                path_vars = path_var;
                wildcard_handler = child;
                ast_trace(-1, "        Checking %s %s:  Matched wildcard.\n", handler->path_segment, child->path_segment);
 
            } else if (strcmp(child->path_segment, path_segment) == 0) {
                found_handler = child;
                ast_trace(-1, "        Checking %s %s:  Explicit match with %s\n", handler->path_segment, child->path_segment, path_segment);
            } else {
                ast_trace(-1, "        Checking %s %s:  Didn't match %s\n", handler->path_segment, child->path_segment, path_segment);
            }
            SCOPE_EXIT("Done checking %s\n", child->path_segment);
        }
 
        if (!found_handler && wildcard_handler) {
            ast_trace(-1, "  No explicit handler found for %s.  Using wildcard %s.\n",
                path_segment, wildcard_handler->path_segment);
            found_handler = wildcard_handler;
            wildcard_handler = NULL;
        }
 
        if (found_handler == NULL) {
            /* resource not found */
            ast_ari_response_error(
                response, 404, "Not Found",
                "Resource not found");
            SCOPE_EXIT_EXPR(break, "Handler not found for %s\n", path_segment);
        } else {
            handler = found_handler;
        }
        SCOPE_EXIT("Done checking %s\n", path_segment);
    }
 
    if (handler == NULL || response->response_code == 404) {
        /* resource not found */
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CONTINUE, "Response: %d : %s %s\n",
            response->response_code, response->response_text, uri);
    }
 
    ast_assert(handler != NULL);
    if (method == AST_HTTP_OPTIONS) {
        handle_options(handler, headers, response);
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CONTINUE, "Was options\n");
    }
 
    if (method < 0 || method >= AST_HTTP_MAX_METHOD) {
        add_allow_header(handler, response);
        ast_ari_response_error(
            response, 405, "Method Not Allowed",
            "Invalid method");
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CONTINUE, "Response: %d : %s\n",
            response->response_code, response->response_text);
    }
 
    if (handler->is_websocket && method == AST_HTTP_GET) {
        if (source == ARI_INVOKE_SOURCE_WEBSOCKET) {
            ast_ari_response_error(
                response, 400, "Bad request",
                "Can't upgrade to websocket from a websocket");
            SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CONTINUE, "Response: %d : %s\n",
                response->response_code, response->response_text);
        }
        /* WebSocket! */
        ast_trace(-1, "Handling websocket %s\n", uri);
        ari_handle_websocket(ser, uri, method,
            get_params, headers);
        /* Since the WebSocket code handles the connection, we shouldn't
         * do anything else; setting no_response */
        response->no_response = 1;
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CONTINUE, "Upgrade to websocket\n");
    }
 
    callback = handler->callbacks[method];
    if (callback == NULL) {
        add_allow_header(handler, response);
        ast_ari_response_error(
            response, 405, "Method Not Allowed",
            "Invalid method");
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CONTINUE, "Response: %d : %s\n",
            response->response_code, response->response_text);
    }
 
    ast_trace(-1, "Running callback: %s\n", uri);
    callback(ser, get_params, path_vars, headers, body, response);
    if (response->message == NULL && response->response_code == 0) {
        /* Really should not happen */
        ast_log(LOG_ERROR, "ARI %s %s not implemented\n",
            ast_get_http_method(method), uri);
        ast_ari_response_error(
            response, 501, "Not Implemented",
            "Method not implemented");
        SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_ERROR_CONTINUE, "Response: %d : %s\n",
            response->response_code, response->response_text);
    }
    SCOPE_EXIT_RTN_VALUE(ARI_INVOKE_RESULT_SUCCESS, "Response: %d : %s\n",
        response->response_code, response->response_text);
}
 
void ast_ari_get_docs(const char *uri, const char *prefix, struct ast_variable *headers,
              struct ast_ari_response *response)
{
    RAII_VAR(struct ast_str *, absolute_path_builder, NULL, ast_free);
    RAII_VAR(char *, absolute_api_dirname, NULL, ast_std_free);
    RAII_VAR(char *, absolute_filename, NULL, ast_std_free);
    struct ast_json *obj = NULL;
    struct ast_variable *host = NULL;
    struct ast_json_error error = {};
    struct stat file_stat;
 
    ast_debug(3, "%s(%s)\n", __func__, uri);
 
    absolute_path_builder = ast_str_create(80);
    if (absolute_path_builder == NULL) {
        ast_ari_response_alloc_failed(response);
        return;
    }
 
    /* absolute path to the rest-api directory */
    ast_str_append(&absolute_path_builder, 0, "%s", ast_config_AST_DATA_DIR);
    ast_str_append(&absolute_path_builder, 0, "/rest-api/");
    absolute_api_dirname = realpath(ast_str_buffer(absolute_path_builder), NULL);
    if (absolute_api_dirname == NULL) {
        ast_log(LOG_ERROR, "Error determining real directory for rest-api\n");
        ast_ari_response_error(
            response, 500, "Internal Server Error",
            "Cannot find rest-api directory");
        return;
    }
 
    /* absolute path to the requested file */
    ast_str_append(&absolute_path_builder, 0, "%s", uri);
    absolute_filename = realpath(ast_str_buffer(absolute_path_builder), NULL);
    if (absolute_filename == NULL) {
        switch (errno) {
        case ENAMETOOLONG:
        case ENOENT:
        case ENOTDIR:
            ast_ari_response_error(
                response, 404, "Not Found",
                "Resource not found");
            break;
        case EACCES:
            ast_ari_response_error(
                response, 403, "Forbidden",
                "Permission denied");
            break;
        default:
            ast_log(LOG_ERROR,
                "Error determining real path for uri '%s': %s\n",
                uri, strerror(errno));
            ast_ari_response_error(
                response, 500, "Internal Server Error",
                "Cannot find file");
            break;
        }
        return;
    }
 
    if (!ast_begins_with(absolute_filename, absolute_api_dirname)) {
        /* HACKERZ! */
        ast_log(LOG_ERROR,
            "Invalid attempt to access '%s' (not in %s)\n",
            absolute_filename, absolute_api_dirname);
        ast_ari_response_error(
            response, 404, "Not Found",
            "Resource not found");
        return;
    }
 
    if (stat(absolute_filename, &file_stat) == 0) {
        if (!(file_stat.st_mode & S_IFREG)) {
            /* Not a file */
            ast_ari_response_error(
                response, 403, "Forbidden",
                "Invalid access");
            return;
        }
    } else {
        /* Does not exist */
        ast_ari_response_error(
            response, 404, "Not Found",
            "Resource not found");
        return;
    }
 
    /* Load resource object from file */
    obj = ast_json_load_new_file(absolute_filename, &error);
    if (obj == NULL) {
        ast_log(LOG_ERROR, "Error parsing resource file: %s:%d(%d) %s\n",
            error.source, error.line, error.column, error.text);
        ast_ari_response_error(
            response, 500, "Internal Server Error",
            "Yikes! Cannot parse resource");
        return;
    }
 
    /* Update the basePath properly */
    if (ast_json_object_get(obj, "basePath") != NULL) {
        for (host = headers; host; host = host->next) {
            if (strcasecmp(host->name, "Host") == 0) {
                break;
            }
        }
        if (host != NULL) {
            if (prefix != NULL && strlen(prefix) > 0) {
                ast_json_object_set(
                    obj, "basePath",
                    ast_json_stringf("http://%s%s/ari", host->value,prefix));
            } else {
                ast_json_object_set(
                    obj, "basePath",
                    ast_json_stringf("http://%s/ari", host->value));
            }
        } else {
            /* Without the host, we don't have the basePath */
            ast_json_object_del(obj, "basePath");
        }
    }
 
    ast_ari_response_ok(response, obj);
}
 
/*!
 * \brief Handle CORS headers for simple requests.
 *
 * See http://www.w3.org/TR/cors/ for the spec. Especially section 6.1.
 */
static void process_cors_request(struct ast_variable *headers,
                 struct ast_ari_response *response)
{
    char const *origin = NULL;
    struct ast_variable *header;
 
    /* Parse CORS headers */
    for (header = headers; header != NULL; header = header->next) {
        if (strcmp("Origin", header->name) == 0) {
            origin = header->value;
        }
    }
 
    /* CORS 6.1, #1 - "If the Origin header is not present terminate this
     * set of steps."
     */
    if (origin == NULL) {
        return;
    }
 
    /* CORS 6.1, #2 - "If the value of the Origin header is not a
     * case-sensitive match for any of the values in list of origins, do not
     * set any additional headers and terminate this set of steps.
     *
     * Note: Always matching is acceptable since the list of origins can be
     * unbounded."
     */
    if (!origin_allowed(origin)) {
        ast_log(LOG_NOTICE, "Origin header '%s' does not match an allowed origin.\n", origin);
        return;
    }
 
    /* CORS 6.1, #3 - "If the resource supports credentials add a single
     * Access-Control-Allow-Origin header, with the value of the Origin
     * header as value, and add a single Access-Control-Allow-Credentials
     * header with the case-sensitive string "true" as value.
     *
     * Otherwise, add a single Access-Control-Allow-Origin header, with
     * either the value of the Origin header or the string "*" as value."
     */
    ast_str_append(&response->headers, 0,
               "Access-Control-Allow-Origin: %s\r\n", origin);
    ast_str_append(&response->headers, 0,
               "Access-Control-Allow-Credentials: true\r\n");
 
    /* CORS 6.1, #4 - "If the list of exposed headers is not empty add one
     * or more Access-Control-Expose-Headers headers, with as values the
     * header field names given in the list of exposed headers."
     *
     * No exposed headers; skipping
     */
}
 
enum ast_json_encoding_format ast_ari_json_format(void)
{
    RAII_VAR(struct ast_ari_conf *, cfg, NULL, ao2_cleanup);
    cfg = ast_ari_config_get();
    return cfg->general->format;
}
 
/*!
 * \internal
 * \brief ARI HTTP handler.
 *
 * This handler takes the HTTP request and turns it into the appropriate
 * RESTful request (conversion to JSON, routing, etc.)
 *
 * \param ser TCP session.
 * \param urih URI handler.
 * \param uri URI requested.
 * \param method HTTP method.
 * \param get_params HTTP \c GET params.
 * \param headers HTTP headers.
 */
static int ast_ari_callback(struct ast_tcptls_session_instance *ser,
                const struct ast_http_uri *urih,
                const char *uri,
                enum ast_http_method method,
                struct ast_variable *get_params,
                struct ast_variable *headers)
{
    RAII_VAR(struct ast_str *, response_body, ast_str_create(256), ast_free);
    struct ast_ari_response response = { .fd = -1, 0 };
    RAII_VAR(struct ast_variable *, post_vars, NULL, ast_variables_destroy);
    struct ast_variable *var;
    const char *app_name = NULL;
    RAII_VAR(struct ast_json *, body, ast_json_null(), ast_json_unref);
    int debug_app = 0;
    enum ast_ari_invoke_result result;
    SCOPE_ENTER(2, "%s: Request: %s %s\n", ast_sockaddr_stringify(&ser->remote_address),
        ast_get_http_method(method), uri);
 
    if (!response_body) {
        ast_http_request_close_on_completion(ser);
        ast_http_error(ser, 500, "Server Error", "Out of memory");
        SCOPE_EXIT_RTN_VALUE(0, "Out of memory\n");
    }
 
    response.headers = ast_str_create(40);
    if (!response.headers) {
        ast_http_request_close_on_completion(ser);
        ast_http_error(ser, 500, "Server Error", "Out of memory");
        SCOPE_EXIT_RTN_VALUE(0, "Out of memory\n");
    }
 
    process_cors_request(headers, &response);
 
    /* Process form data from a POST. It could be mixed with query
     * parameters, which seems a bit odd. But it's allowed, so that's okay
     * with us.
     */
    post_vars = ast_http_get_post_vars(ser, headers);
    if (!post_vars) {
        ast_trace(-1, "No post_vars\n");
        switch (errno) {
        case EFBIG:
            ast_ari_response_error(&response, 413,
                "Request Entity Too Large",
                "Request body too large");
            goto request_failed;
        case ENOMEM:
            ast_http_request_close_on_completion(ser);
            ast_ari_response_error(&response, 500,
                "Internal Server Error",
                "Out of memory");
            goto request_failed;
        case EIO:
            ast_ari_response_error(&response, 400,
                "Bad Request", "Error parsing request body");
            goto request_failed;
        }
 
        /* Look for a JSON request entity only if there were no post_vars.
         * If there were post_vars, then the request body would already have
         * been consumed and can not be read again.
         */
        ast_trace(-1, "Checking body for vars\n");
        body = ast_http_get_json(ser, headers);
        if (!body) {
            switch (errno) {
            case EFBIG:
                ast_ari_response_error(&response, 413, "Request Entity Too Large", "Request body too large");
                goto request_failed;
            case ENOMEM:
                ast_ari_response_error(&response, 500, "Internal Server Error", "Error processing request");
                goto request_failed;
            case EIO:
                ast_ari_response_error(&response, 400, "Bad Request", "Error parsing request body");
                goto request_failed;
            }
        }
    }
    if (get_params == NULL) {
        ast_trace(-1, "No get_params, using post_vars if any\n");
        get_params = post_vars;
    } else if (get_params && post_vars) {
        /* Has both post_vars and get_params */
        struct ast_variable *last_var = post_vars;
        ast_trace(-1, "Has get_params and post_vars.  Merging\n");
        while (last_var->next) {
            last_var = last_var->next;
        }
        /* The duped get_params will get freed when post_vars gets
         * ast_variables_destroyed.
         */
        last_var->next = ast_variables_dup(get_params);
        get_params = post_vars;
    }
 
    /* At this point, get_params will contain post_vars (if any) */
    app_name = ast_variable_find_in_list(get_params, "app");
    if (!app_name) {
        struct ast_json *app = ast_json_object_get(body, "app");
 
        app_name = (app ? ast_json_string_get(app) : NULL);
    }
    ast_trace(-1, "app_name: %s\n", app_name);
 
    /* stasis_app_get_debug_by_name returns an "||" of the app's debug flag
     * and the global debug flag.
     */
    debug_app = stasis_app_get_debug_by_name(app_name);
    if (debug_app) {
        struct ast_str *buf = ast_str_create(512);
        char *str = ast_json_dump_string_format(body, ast_ari_json_format());
 
        if (!buf || (body && !str)) {
            ast_http_request_close_on_completion(ser);
            ast_ari_response_error(&response, 500, "Server Error", "Out of memory");
            ast_json_free(str);
            ast_free(buf);
            goto request_failed;
        }
 
        ast_str_append(&buf, 0, "<--- ARI request received from: %s --->\n",
            ast_sockaddr_stringify(&ser->remote_address));
        ast_str_append(&buf, 0, "%s %s\n", ast_get_http_method(method), uri);
        for (var = headers; var; var = var->next) {
            ast_str_append(&buf, 0, "%s: %s\n", var->name, var->value);
        }
        for (var = get_params; var; var = var->next) {
            ast_str_append(&buf, 0, "%s: %s\n", var->name, var->value);
        }
        ast_verbose("%sbody:\n%s\n\n", ast_str_buffer(buf), S_OR(str, ""));
        ast_json_free(str);
        ast_free(buf);
    }
 
    result = SCOPE_CALL_WITH_RESULT(-1, enum ast_ari_invoke_result,
        ast_ari_invoke, ser, ARI_INVOKE_SOURCE_REST,
        urih, uri, method, get_params, headers, body, &response);
    if (result == ARI_INVOKE_RESULT_ERROR_CLOSE) {
        ast_http_request_close_on_completion(ser);
    }
 
    if (response.no_response) {
        /* The handler indicates no further response is necessary.
         * Probably because it already handled it */
        ast_free(response.headers);
        SCOPE_EXIT_RTN_VALUE(0, "No response needed\n");
    }
 
request_failed:
 
    /* If you explicitly want to have no content, set message to
     * ast_json_null().
     */
    ast_assert(response.message != NULL);
    ast_assert(response.response_code > 0);
 
    /* response.message could be NULL, in which case the empty response_body
     * is correct
     */
    if (response.message && !ast_json_is_null(response.message)) {
        ast_str_append(&response.headers, 0,
                   "Content-type: application/json\r\n");
        if (ast_json_dump_str_format(response.message, &response_body,
            ast_ari_json_format()) != 0) {
            /* Error encoding response */
            response.response_code = 500;
            response.response_text = "Internal Server Error";
            ast_str_set(&response_body, 0, "%s", "");
            ast_str_set(&response.headers, 0, "%s", "");
        }
    }
 
    if (debug_app) {
        ast_verbose("<--- Sending ARI response to %s --->\n%d %s\n%s%s\n\n",
            ast_sockaddr_stringify(&ser->remote_address), response.response_code,
            response.response_text, ast_str_buffer(response.headers),
            ast_str_buffer(response_body));
    }
 
    ast_http_send(ser, method, response.response_code,
              response.response_text, response.headers, response_body,
              response.fd != -1 ? response.fd : 0, 0);
    /* ast_http_send takes ownership, so we don't have to free them */
    response_body = NULL;
 
    ast_json_unref(response.message);
    if (response.fd >= 0) {
        close(response.fd);
    }
    SCOPE_EXIT_RTN_VALUE(0, "Done.  response: %d : %s\n", response.response_code,
        response.response_text);
}
 
static int unload_module(void)
{
    ari_websocket_unload_module();
 
    ast_ari_cli_unregister();
 
    if (is_enabled()) {
        ast_debug(3, "Disabling ARI\n");
        ast_http_uri_unlink(&http_uri);
    }
 
    ast_ari_config_destroy();
 
    ao2_cleanup(root_handler);
    root_handler = NULL;
    ast_mutex_destroy(&root_handler_lock);
 
    ast_json_unref(oom_json);
    oom_json = NULL;
 
    return 0;
}
 
static int load_module(void)
{
    ast_mutex_init(&root_handler_lock);
 
    /* root_handler may have been built during a declined load */
    if (!root_handler) {
        root_handler = root_handler_create();
    }
    if (!root_handler) {
        return AST_MODULE_LOAD_DECLINE;
    }
 
    /* oom_json may have been built during a declined load */
    if (!oom_json) {
        oom_json = ast_json_pack(
            "{s: s}", "error", "Allocation failed");
    }
    if (!oom_json) {
        /* Ironic */
        unload_module();
        return AST_MODULE_LOAD_DECLINE;
    }
 
    if (ast_ari_config_init() != 0) {
        unload_module();
        return AST_MODULE_LOAD_DECLINE;
    }
 
    if (ari_websocket_load_module() != AST_MODULE_LOAD_SUCCESS) {
        unload_module();
        return AST_MODULE_LOAD_DECLINE;
    }
 
    if (is_enabled()) {
        ast_debug(3, "ARI enabled\n");
        ast_http_uri_link(&http_uri);
    } else {
        ast_debug(3, "ARI disabled\n");
    }
 
    if (ast_ari_cli_register() != 0) {
        unload_module();
        return AST_MODULE_LOAD_DECLINE;
    }
 
    return AST_MODULE_LOAD_SUCCESS;
}
 
static int reload_module(void)
{
    char was_enabled = is_enabled();
 
    if (ast_ari_config_reload() != 0) {
        return AST_MODULE_LOAD_DECLINE;
    }
 
    if (was_enabled && !is_enabled()) {
        ast_debug(3, "Disabling ARI\n");
        ast_http_uri_unlink(&http_uri);
    } else if (!was_enabled && is_enabled()) {
        ast_debug(3, "Enabling ARI\n");
        ast_http_uri_link(&http_uri);
    }
 
    return AST_MODULE_LOAD_SUCCESS;
}
 
AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER, "Asterisk RESTful Interface",
    .support_level = AST_MODULE_SUPPORT_CORE,
    .load = load_module,
    .unload = unload_module,
    .reload = reload_module,
    .requires = "http,res_stasis,res_http_websocket",
    .load_pri = AST_MODPRI_APP_DEPEND,
);