Merge "BuildSystem: Really do not pass unknown-warning options to the compiler."
[asterisk/asterisk.git] / funcs / func_shell.c
1 /*
2  * Asterisk -- An open source telephony toolkit.
3  *
4  * Copyright (C) 2006-2012, Digium, Inc.
5  *
6  * See http://www.asterisk.org for more information about
7  * the Asterisk project. Please do not directly contact
8  * any of the maintainers of this project for assistance;
9  * the project provides a web site, mailing lists and IRC
10  * channels for your use.
11  *
12  * This program is free software, distributed under the terms of
13  * the GNU General Public License Version 2. See the LICENSE file
14  * at the top of the source tree.
15  */
16
17 /*! \file
18  *
19  * SHELL function to return the output generated by a command issued to the system shell.
20  *
21  * \note Inspiration and Guidance from Russell! Thank You!
22  *
23  * \author Brandon Kruse <bkruse@digium.com>
24  *
25  * \ingroup functions
26  */
27
28 /*** MODULEINFO
29         <support_level>core</support_level>
30  ***/
31
32 #include "asterisk.h"
33
34 #include "asterisk/module.h"
35 #include "asterisk/channel.h"
36 #include "asterisk/pbx.h"
37 #include "asterisk/utils.h"
38 #include "asterisk/app.h"
39
40 static int shell_helper(struct ast_channel *chan, const char *cmd, char *data,
41                                          char *buf, size_t len)
42 {
43         int res = 0;
44
45         if (ast_strlen_zero(data)) {
46                 ast_log(LOG_WARNING, "Missing Argument!  Example:  Set(foo=${SHELL(echo \"bar\")})\n");
47                 return -1;
48         }
49
50         if (chan) {
51                 ast_autoservice_start(chan);
52         }
53
54         if (len >= 1) {
55                 FILE *ptr;
56                 char plbuff[4096];
57
58                 ptr = popen(data, "r");
59                 if (ptr) {
60                         while (fgets(plbuff, sizeof(plbuff), ptr)) {
61                                 strncat(buf, plbuff, len - strlen(buf) - 1);
62                         }
63                         pclose(ptr);
64                 } else {
65                         ast_log(LOG_WARNING, "Failed to execute shell command '%s'\n", data);
66                         res = -1;
67                 }
68         }
69
70         if (chan) {
71                 ast_autoservice_stop(chan);
72         }
73
74         return res;
75 }
76
77 /*** DOCUMENTATION
78         <function name="SHELL" language="en_US">
79                 <synopsis>
80                         Executes a command using the system shell and captures its output.
81                 </synopsis>
82                 <syntax>
83                         <parameter name="command" required="true">
84                                 <para>The command that the shell should execute.</para>
85                                 <warning><para>Do not use untrusted strings such as <variable>CALLERID(num)</variable>
86                                 or <variable>CALLERID(name)</variable> as part of the command parameters.  You
87                                 risk a command injection attack executing arbitrary commands if the untrusted
88                                 strings aren't filtered to remove dangerous characters.  See function
89                                 <variable>FILTER()</variable>.</para></warning>
90                         </parameter>
91                 </syntax>
92                 <description>
93                         <para>Collects the output generated by a command executed by the system shell</para>
94                         <para>Example:  <literal>Set(foo=${SHELL(echo bar)})</literal></para>
95                         <note>
96                                 <para>The command supplied to this function will be executed by the
97                                 system's shell, typically specified in the SHELL environment variable. There
98                                 are many different system shells available with somewhat different behaviors,
99                                 so the output generated by this function may vary between platforms.</para>
100
101                                 <para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
102                                 is set to <literal>no</literal>, this function can only be executed from the
103                                 dialplan, and not directly from external protocols.</para>
104                         </note>
105                 </description>
106
107         </function>
108  ***/
109 static struct ast_custom_function shell_function = {
110         .name = "SHELL",
111         .read = shell_helper,
112 };
113
114 static int unload_module(void)
115 {
116         return ast_custom_function_unregister(&shell_function);
117 }
118
119 static int load_module(void)
120 {
121         return ast_custom_function_register_escalating(&shell_function, AST_CFE_READ);
122 }
123
124 AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Collects the output generated by a command executed by the system shell");