asterisk/main/pbx_functions.c

740 lines
19 KiB
C

/*
* Asterisk -- An open source telephony toolkit.
*
* Copyright (C) 2015, CFWare, LLC
*
* Corey Farrell <git@cfware.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 Custom function management routines.
*
* \author Corey Farrell <git@cfware.com>
*/
/*** MODULEINFO
<support_level>core</support_level>
***/
#include "asterisk.h"
#include "asterisk/_private.h"
#include "asterisk/cli.h"
#include "asterisk/linkedlists.h"
#include "asterisk/module.h"
#include "asterisk/pbx.h"
#include "asterisk/term.h"
#include "asterisk/threadstorage.h"
#include "asterisk/xmldoc.h"
#include "pbx_private.h"
/*!
* \brief A thread local indicating whether the current thread can run
* 'dangerous' dialplan functions.
*/
AST_THREADSTORAGE(thread_inhibit_escalations_tl);
/*!
* \brief Set to true (non-zero) to globally allow all dangerous dialplan
* functions to run.
*/
static int live_dangerously;
/*!
* \brief Registered functions container.
*
* It is sorted by function name.
*/
static AST_RWLIST_HEAD_STATIC(acf_root, ast_custom_function);
static char *handle_show_functions(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
struct ast_custom_function *acf;
int count_acf = 0;
int like = 0;
switch (cmd) {
case CLI_INIT:
e->command = "core show functions [like]";
e->usage =
"Usage: core show functions [like <text>]\n"
" List builtin functions, optionally only those matching a given string\n";
return NULL;
case CLI_GENERATE:
return NULL;
}
if (a->argc == 5 && (!strcmp(a->argv[3], "like")) ) {
like = 1;
} else if (a->argc != 3) {
return CLI_SHOWUSAGE;
}
ast_cli(a->fd, "%s Custom Functions:\n"
"--------------------------------------------------------------------------------\n",
like ? "Matching" : "Installed");
AST_RWLIST_RDLOCK(&acf_root);
AST_RWLIST_TRAVERSE(&acf_root, acf, acflist) {
if (!like || strstr(acf->name, a->argv[4])) {
count_acf++;
ast_cli(a->fd, "%-20.20s %-35.35s %s\n",
S_OR(acf->name, ""),
S_OR(acf->syntax, ""),
S_OR(acf->synopsis, ""));
}
}
AST_RWLIST_UNLOCK(&acf_root);
ast_cli(a->fd, "%d %scustom functions installed.\n", count_acf, like ? "matching " : "");
return CLI_SUCCESS;
}
static char *complete_functions(const char *word, int pos, int state)
{
struct ast_custom_function *cur;
char *ret = NULL;
int which = 0;
int wordlen;
int cmp;
if (pos != 3) {
return NULL;
}
wordlen = strlen(word);
AST_RWLIST_RDLOCK(&acf_root);
AST_RWLIST_TRAVERSE(&acf_root, cur, acflist) {
/*
* Do a case-insensitive search for convenience in this
* 'complete' function.
*
* We must search the entire container because the functions are
* sorted and normally found case sensitively.
*/
cmp = strncasecmp(word, cur->name, wordlen);
if (!cmp) {
/* Found match. */
if (++which <= state) {
/* Not enough matches. */
continue;
}
ret = ast_strdup(cur->name);
break;
}
}
AST_RWLIST_UNLOCK(&acf_root);
return ret;
}
static char *handle_show_function(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
struct ast_custom_function *acf;
/* Maximum number of characters added by terminal coloring is 22 */
char infotitle[64 + AST_MAX_APP + 22], syntitle[40], desctitle[40], argtitle[40], seealsotitle[40];
char info[64 + AST_MAX_APP], *synopsis = NULL, *description = NULL, *seealso = NULL;
char stxtitle[40], *syntax = NULL, *arguments = NULL;
int syntax_size, description_size, synopsis_size, arguments_size, seealso_size;
switch (cmd) {
case CLI_INIT:
e->command = "core show function";
e->usage =
"Usage: core show function <function>\n"
" Describe a particular dialplan function.\n";
return NULL;
case CLI_GENERATE:
return complete_functions(a->word, a->pos, a->n);
}
if (a->argc != 4) {
return CLI_SHOWUSAGE;
}
if (!(acf = ast_custom_function_find(a->argv[3]))) {
ast_cli(a->fd, "No function by that name registered.\n");
return CLI_FAILURE;
}
syntax_size = strlen(S_OR(acf->syntax, "Not Available")) + AST_TERM_MAX_ESCAPE_CHARS;
syntax = ast_malloc(syntax_size);
if (!syntax) {
ast_cli(a->fd, "Memory allocation failure!\n");
return CLI_FAILURE;
}
snprintf(info, sizeof(info), "\n -= Info about function '%s' =- \n\n", acf->name);
term_color(infotitle, info, COLOR_MAGENTA, 0, sizeof(infotitle));
term_color(syntitle, "[Synopsis]\n", COLOR_MAGENTA, 0, 40);
term_color(desctitle, "[Description]\n", COLOR_MAGENTA, 0, 40);
term_color(stxtitle, "[Syntax]\n", COLOR_MAGENTA, 0, 40);
term_color(argtitle, "[Arguments]\n", COLOR_MAGENTA, 0, 40);
term_color(seealsotitle, "[See Also]\n", COLOR_MAGENTA, 0, 40);
term_color(syntax, S_OR(acf->syntax, "Not available"), COLOR_CYAN, 0, syntax_size);
#ifdef AST_XML_DOCS
if (acf->docsrc == AST_XML_DOC) {
arguments = ast_xmldoc_printable(S_OR(acf->arguments, "Not available"), 1);
synopsis = ast_xmldoc_printable(S_OR(acf->synopsis, "Not available"), 1);
description = ast_xmldoc_printable(S_OR(acf->desc, "Not available"), 1);
seealso = ast_xmldoc_printable(S_OR(acf->seealso, "Not available"), 1);
} else
#endif
{
synopsis_size = strlen(S_OR(acf->synopsis, "Not Available")) + AST_TERM_MAX_ESCAPE_CHARS;
synopsis = ast_malloc(synopsis_size);
description_size = strlen(S_OR(acf->desc, "Not Available")) + AST_TERM_MAX_ESCAPE_CHARS;
description = ast_malloc(description_size);
arguments_size = strlen(S_OR(acf->arguments, "Not Available")) + AST_TERM_MAX_ESCAPE_CHARS;
arguments = ast_malloc(arguments_size);
seealso_size = strlen(S_OR(acf->seealso, "Not Available")) + AST_TERM_MAX_ESCAPE_CHARS;
seealso = ast_malloc(seealso_size);
/* check allocated memory. */
if (!synopsis || !description || !arguments || !seealso) {
ast_free(synopsis);
ast_free(description);
ast_free(arguments);
ast_free(seealso);
ast_free(syntax);
return CLI_FAILURE;
}
term_color(arguments, S_OR(acf->arguments, "Not available"), COLOR_CYAN, 0, arguments_size);
term_color(synopsis, S_OR(acf->synopsis, "Not available"), COLOR_CYAN, 0, synopsis_size);
term_color(description, S_OR(acf->desc, "Not available"), COLOR_CYAN, 0, description_size);
term_color(seealso, S_OR(acf->seealso, "Not available"), COLOR_CYAN, 0, seealso_size);
}
ast_cli(a->fd, "%s%s%s\n\n%s%s\n\n%s%s\n\n%s%s\n\n%s%s\n",
infotitle, syntitle, synopsis, desctitle, description,
stxtitle, syntax, argtitle, arguments, seealsotitle, seealso);
ast_free(arguments);
ast_free(synopsis);
ast_free(description);
ast_free(seealso);
ast_free(syntax);
return CLI_SUCCESS;
}
static struct ast_custom_function *ast_custom_function_find_nolock(const char *name)
{
struct ast_custom_function *cur;
int cmp;
AST_RWLIST_TRAVERSE(&acf_root, cur, acflist) {
cmp = strcmp(name, cur->name);
if (cmp > 0) {
continue;
}
if (!cmp) {
/* Found it. */
break;
}
/* Not in container. */
cur = NULL;
break;
}
return cur;
}
struct ast_custom_function *ast_custom_function_find(const char *name)
{
struct ast_custom_function *acf;
AST_RWLIST_RDLOCK(&acf_root);
acf = ast_custom_function_find_nolock(name);
AST_RWLIST_UNLOCK(&acf_root);
return acf;
}
int ast_custom_function_unregister(struct ast_custom_function *acf)
{
struct ast_custom_function *cur;
if (!acf) {
return -1;
}
AST_RWLIST_WRLOCK(&acf_root);
cur = AST_RWLIST_REMOVE(&acf_root, acf, acflist);
if (cur) {
#ifdef AST_XML_DOCS
if (cur->docsrc == AST_XML_DOC) {
ast_string_field_free_memory(acf);
}
#endif
ast_verb(2, "Unregistered custom function %s\n", cur->name);
}
AST_RWLIST_UNLOCK(&acf_root);
return cur ? 0 : -1;
}
/*!
* \brief Returns true if given custom function escalates privileges on read.
*
* \param acf Custom function to query.
* \return True (non-zero) if reads escalate privileges.
* \return False (zero) if reads just read.
*/
static int read_escalates(const struct ast_custom_function *acf)
{
return acf->read_escalates;
}
/*!
* \brief Returns true if given custom function escalates privileges on write.
*
* \param acf Custom function to query.
* \return True (non-zero) if writes escalate privileges.
* \return False (zero) if writes just write.
*/
static int write_escalates(const struct ast_custom_function *acf)
{
return acf->write_escalates;
}
/*! \internal
* \brief Retrieve the XML documentation of a specified ast_custom_function,
* and populate ast_custom_function string fields.
* \param acf ast_custom_function structure with empty 'desc' and 'synopsis'
* but with a function 'name'.
* \retval -1 On error.
* \retval 0 On succes.
*/
static int acf_retrieve_docs(struct ast_custom_function *acf)
{
#ifdef AST_XML_DOCS
char *tmpxml;
/* Let's try to find it in the Documentation XML */
if (!ast_strlen_zero(acf->desc) || !ast_strlen_zero(acf->synopsis)) {
return 0;
}
if (ast_string_field_init(acf, 128)) {
return -1;
}
/* load synopsis */
tmpxml = ast_xmldoc_build_synopsis("function", acf->name, ast_module_name(acf->mod));
ast_string_field_set(acf, synopsis, tmpxml);
ast_free(tmpxml);
/* load description */
tmpxml = ast_xmldoc_build_description("function", acf->name, ast_module_name(acf->mod));
ast_string_field_set(acf, desc, tmpxml);
ast_free(tmpxml);
/* load syntax */
tmpxml = ast_xmldoc_build_syntax("function", acf->name, ast_module_name(acf->mod));
ast_string_field_set(acf, syntax, tmpxml);
ast_free(tmpxml);
/* load arguments */
tmpxml = ast_xmldoc_build_arguments("function", acf->name, ast_module_name(acf->mod));
ast_string_field_set(acf, arguments, tmpxml);
ast_free(tmpxml);
/* load seealso */
tmpxml = ast_xmldoc_build_seealso("function", acf->name, ast_module_name(acf->mod));
ast_string_field_set(acf, seealso, tmpxml);
ast_free(tmpxml);
acf->docsrc = AST_XML_DOC;
#endif
return 0;
}
int __ast_custom_function_register(struct ast_custom_function *acf, struct ast_module *mod)
{
struct ast_custom_function *cur;
if (!acf) {
return -1;
}
acf->mod = mod;
#ifdef AST_XML_DOCS
acf->docsrc = AST_STATIC_DOC;
#endif
if (acf_retrieve_docs(acf)) {
return -1;
}
AST_RWLIST_WRLOCK(&acf_root);
cur = ast_custom_function_find_nolock(acf->name);
if (cur) {
ast_log(LOG_ERROR, "Function %s already registered.\n", acf->name);
AST_RWLIST_UNLOCK(&acf_root);
return -1;
}
/* Store in alphabetical order */
AST_RWLIST_TRAVERSE_SAFE_BEGIN(&acf_root, cur, acflist) {
if (strcmp(acf->name, cur->name) < 0) {
AST_RWLIST_INSERT_BEFORE_CURRENT(acf, acflist);
break;
}
}
AST_RWLIST_TRAVERSE_SAFE_END;
if (!cur) {
AST_RWLIST_INSERT_TAIL(&acf_root, acf, acflist);
}
AST_RWLIST_UNLOCK(&acf_root);
ast_verb(2, "Registered custom function '" COLORIZE_FMT "'\n", COLORIZE(COLOR_BRCYAN, 0, acf->name));
return 0;
}
int __ast_custom_function_register_escalating(struct ast_custom_function *acf, enum ast_custom_function_escalation escalation, struct ast_module *mod)
{
int res;
res = __ast_custom_function_register(acf, mod);
if (res != 0) {
return -1;
}
switch (escalation) {
case AST_CFE_NONE:
break;
case AST_CFE_READ:
acf->read_escalates = 1;
break;
case AST_CFE_WRITE:
acf->write_escalates = 1;
break;
case AST_CFE_BOTH:
acf->read_escalates = 1;
acf->write_escalates = 1;
break;
}
return 0;
}
/*! \brief return a pointer to the arguments of the function,
* and terminates the function name with '\\0'
*/
static char *func_args(char *function)
{
char *args = strchr(function, '(');
if (!args) {
ast_log(LOG_WARNING, "Function '%s' doesn't contain parentheses. Assuming null argument.\n", function);
} else {
char *p;
*args++ = '\0';
if ((p = strrchr(args, ')'))) {
*p = '\0';
} else {
ast_log(LOG_WARNING, "Can't find trailing parenthesis for function '%s(%s'?\n", function, args);
}
}
return args;
}
void pbx_live_dangerously(int new_live_dangerously)
{
if (new_live_dangerously && !live_dangerously) {
ast_log(LOG_WARNING, "Privilege escalation protection disabled!\n"
"See https://wiki.asterisk.org/wiki/x/1gKfAQ for more details.\n");
}
if (!new_live_dangerously && live_dangerously) {
ast_log(LOG_NOTICE, "Privilege escalation protection enabled.\n");
}
live_dangerously = new_live_dangerously;
}
int ast_thread_inhibit_escalations(void)
{
int *thread_inhibit_escalations;
thread_inhibit_escalations = ast_threadstorage_get(
&thread_inhibit_escalations_tl, sizeof(*thread_inhibit_escalations));
if (thread_inhibit_escalations == NULL) {
ast_log(LOG_ERROR, "Error inhibiting privilege escalations for current thread\n");
return -1;
}
*thread_inhibit_escalations = 1;
return 0;
}
int ast_thread_inhibit_escalations_swap(int inhibit)
{
int *thread_inhibit_escalations;
int orig;
thread_inhibit_escalations = ast_threadstorage_get(
&thread_inhibit_escalations_tl, sizeof(*thread_inhibit_escalations));
if (thread_inhibit_escalations == NULL) {
ast_log(LOG_ERROR, "Error swapping privilege escalations inhibit for current thread\n");
return -1;
}
orig = *thread_inhibit_escalations;
*thread_inhibit_escalations = !!inhibit;
return orig;
}
/*!
* \brief Indicates whether the current thread inhibits the execution of
* dangerous functions.
*
* \return True (non-zero) if dangerous function execution is inhibited.
* \return False (zero) if dangerous function execution is allowed.
*/
static int thread_inhibits_escalations(void)
{
int *thread_inhibit_escalations;
thread_inhibit_escalations = ast_threadstorage_get(
&thread_inhibit_escalations_tl, sizeof(*thread_inhibit_escalations));
if (thread_inhibit_escalations == NULL) {
ast_log(LOG_ERROR, "Error checking thread's ability to run dangerous functions\n");
/* On error, assume that we are inhibiting */
return 1;
}
return *thread_inhibit_escalations;
}
/*!
* \brief Determines whether execution of a custom function's read function
* is allowed.
*
* \param acfptr Custom function to check
* \return True (non-zero) if reading is allowed.
* \return False (zero) if reading is not allowed.
*/
static int is_read_allowed(struct ast_custom_function *acfptr)
{
if (!acfptr) {
return 1;
}
if (!read_escalates(acfptr)) {
return 1;
}
if (!thread_inhibits_escalations()) {
return 1;
}
if (live_dangerously) {
/* Global setting overrides the thread's preference */
ast_debug(2, "Reading %s from a dangerous context\n",
acfptr->name);
return 1;
}
/* We have no reason to allow this function to execute */
return 0;
}
/*!
* \brief Determines whether execution of a custom function's write function
* is allowed.
*
* \param acfptr Custom function to check
* \return True (non-zero) if writing is allowed.
* \return False (zero) if writing is not allowed.
*/
static int is_write_allowed(struct ast_custom_function *acfptr)
{
if (!acfptr) {
return 1;
}
if (!write_escalates(acfptr)) {
return 1;
}
if (!thread_inhibits_escalations()) {
return 1;
}
if (live_dangerously) {
/* Global setting overrides the thread's preference */
ast_debug(2, "Writing %s from a dangerous context\n",
acfptr->name);
return 1;
}
/* We have no reason to allow this function to execute */
return 0;
}
int ast_func_read(struct ast_channel *chan, const char *function, char *workspace, size_t len)
{
char *copy = ast_strdupa(function);
char *args = func_args(copy);
struct ast_custom_function *acfptr = ast_custom_function_find(copy);
int res;
struct ast_module_user *u = NULL;
if (acfptr == NULL) {
ast_log(LOG_ERROR, "Function %s not registered\n", copy);
} else if (!acfptr->read && !acfptr->read2) {
ast_log(LOG_ERROR, "Function %s cannot be read\n", copy);
} else if (!is_read_allowed(acfptr)) {
ast_log(LOG_ERROR, "Dangerous function %s read blocked\n", copy);
} else if (acfptr->read) {
if (acfptr->mod) {
u = __ast_module_user_add(acfptr->mod, chan);
}
res = acfptr->read(chan, copy, args, workspace, len);
if (acfptr->mod && u) {
__ast_module_user_remove(acfptr->mod, u);
}
return res;
} else {
struct ast_str *str = ast_str_create(16);
if (acfptr->mod) {
u = __ast_module_user_add(acfptr->mod, chan);
}
res = acfptr->read2(chan, copy, args, &str, 0);
if (acfptr->mod && u) {
__ast_module_user_remove(acfptr->mod, u);
}
ast_copy_string(workspace, ast_str_buffer(str), len > ast_str_size(str) ? ast_str_size(str) : len);
ast_free(str);
return res;
}
return -1;
}
int ast_func_read2(struct ast_channel *chan, const char *function, struct ast_str **str, ssize_t maxlen)
{
char *copy = ast_strdupa(function);
char *args = func_args(copy);
struct ast_custom_function *acfptr = ast_custom_function_find(copy);
int res;
struct ast_module_user *u = NULL;
if (acfptr == NULL) {
ast_log(LOG_ERROR, "Function %s not registered\n", copy);
} else if (!acfptr->read && !acfptr->read2) {
ast_log(LOG_ERROR, "Function %s cannot be read\n", copy);
} else if (!is_read_allowed(acfptr)) {
ast_log(LOG_ERROR, "Dangerous function %s read blocked\n", copy);
} else {
if (acfptr->mod) {
u = __ast_module_user_add(acfptr->mod, chan);
}
ast_str_reset(*str);
if (acfptr->read2) {
/* ast_str enabled */
res = acfptr->read2(chan, copy, args, str, maxlen);
} else {
/* Legacy function pointer, allocate buffer for result */
int maxsize = ast_str_size(*str);
if (maxlen > -1) {
if (maxlen == 0) {
if (acfptr->read_max) {
maxsize = acfptr->read_max;
} else {
maxsize = VAR_BUF_SIZE;
}
} else {
maxsize = maxlen;
}
ast_str_make_space(str, maxsize);
}
res = acfptr->read(chan, copy, args, ast_str_buffer(*str), maxsize);
ast_str_update(*str); /* Manually set the string length */
}
if (acfptr->mod && u) {
__ast_module_user_remove(acfptr->mod, u);
}
return res;
}
return -1;
}
int ast_func_write(struct ast_channel *chan, const char *function, const char *value)
{
char *copy = ast_strdupa(function);
char *args = func_args(copy);
struct ast_custom_function *acfptr = ast_custom_function_find(copy);
if (acfptr == NULL) {
ast_log(LOG_ERROR, "Function %s not registered\n", copy);
} else if (!acfptr->write) {
ast_log(LOG_ERROR, "Function %s cannot be written to\n", copy);
} else if (!is_write_allowed(acfptr)) {
ast_log(LOG_ERROR, "Dangerous function %s write blocked\n", copy);
} else {
int res;
struct ast_module_user *u = NULL;
if (acfptr->mod) {
u = __ast_module_user_add(acfptr->mod, chan);
}
res = acfptr->write(chan, copy, args, value);
if (acfptr->mod && u) {
__ast_module_user_remove(acfptr->mod, u);
}
return res;
}
return -1;
}
static struct ast_cli_entry acf_cli[] = {
AST_CLI_DEFINE(handle_show_functions, "Shows registered dialplan functions"),
AST_CLI_DEFINE(handle_show_function, "Describe a specific dialplan function"),
};
static void unload_pbx_functions_cli(void)
{
ast_cli_unregister_multiple(acf_cli, ARRAY_LEN(acf_cli));
}
int load_pbx_functions_cli(void)
{
ast_cli_register_multiple(acf_cli, ARRAY_LEN(acf_cli));
ast_register_cleanup(unload_pbx_functions_cli);
return 0;
}