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This patch allows individual dialplan functions to be marked as 'dangerous', to inhibit their execution from external sources. A 'dangerous' function is one which results in a privilege escalation. For example, if one were to read the channel variable SHELL(rm -rf /) Bad Things(TM) could happen; even if the external source has only read permissions. Execution from external sources may be enabled by setting 'live_dangerously' to 'yes' in the [options] section of asterisk.conf. Although doing so is not recommended. Also, the ABI was changed to something more reasonable, since Asterisk 12 does not yet have a public release. (closes issue ASTERISK-22905) Review: http://reviewboard.digium.internal/r/432/ ........ Merged revisions 403913 from http://svn.asterisk.org/svn/asterisk/branches/1.8 ........ Merged revisions 403917 from http://svn.asterisk.org/svn/asterisk/branches/11 ........ Merged revisions 403959 from http://svn.asterisk.org/svn/asterisk/branches/12 git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@403960 65c4cc65-6c06-0410-ace0-fbb531ad65f3
122 lines
3.2 KiB
C
122 lines
3.2 KiB
C
/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 2006-2012, Digium, Inc.
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*! \file
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*
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* SHELL function to return the output generated by a command issued to the system shell.
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*
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* \note Inspiration and Guidance from Russell! Thank You!
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*
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* \author Brandon Kruse <bkruse@digium.com>
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*
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* \ingroup functions
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*/
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/*** MODULEINFO
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<support_level>core</support_level>
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***/
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#include "asterisk.h"
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ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
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#include "asterisk/module.h"
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#include "asterisk/channel.h"
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#include "asterisk/pbx.h"
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#include "asterisk/utils.h"
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#include "asterisk/app.h"
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static int shell_helper(struct ast_channel *chan, const char *cmd, char *data,
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char *buf, size_t len)
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{
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int res = 0;
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if (ast_strlen_zero(data)) {
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ast_log(LOG_WARNING, "Missing Argument! Example: Set(foo=${SHELL(echo \"bar\")})\n");
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return -1;
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}
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if (chan) {
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ast_autoservice_start(chan);
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}
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if (len >= 1) {
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FILE *ptr;
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char plbuff[4096];
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ptr = popen(data, "r");
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if (ptr) {
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while (fgets(plbuff, sizeof(plbuff), ptr)) {
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strncat(buf, plbuff, len - strlen(buf) - 1);
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}
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pclose(ptr);
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} else {
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ast_log(LOG_WARNING, "Failed to execute shell command '%s'\n", data);
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res = -1;
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}
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}
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if (chan) {
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ast_autoservice_stop(chan);
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}
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return res;
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}
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/*** DOCUMENTATION
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<function name="SHELL" language="en_US">
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<synopsis>
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Executes a command using the system shell and captures its output.
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</synopsis>
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<syntax>
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<parameter name="command" required="true">
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<para>The command that the shell should execute.</para>
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</parameter>
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</syntax>
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<description>
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<para>Collects the output generated by a command executed by the system shell</para>
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<para>Example: <literal>Set(foo=${SHELL(echo bar)})</literal></para>
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<note>
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<para>The command supplied to this function will be executed by the
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system's shell, typically specified in the SHELL environment variable. There
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are many different system shells available with somewhat different behaviors,
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so the output generated by this function may vary between platforms.</para>
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<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
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is set to <literal>no</literal>, this function can only be executed from the
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dialplan, and not directly from external protocols.</para>
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</note>
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</description>
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</function>
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***/
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static struct ast_custom_function shell_function = {
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.name = "SHELL",
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.read = shell_helper,
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};
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static int unload_module(void)
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{
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return ast_custom_function_unregister(&shell_function);
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}
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static int load_module(void)
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{
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return ast_custom_function_register_escalating(&shell_function, AST_CFE_READ);
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}
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AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Collects the output generated by a command executed by the system shell");
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