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security: Inhibit execution of privilege escalating functions

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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/
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Merged revisions 403913 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 403917 from http://svn.asterisk.org/svn/asterisk/branches/11
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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
This commit is contained in:
David M. Lee
2013-12-16 19:11:51 +00:00
parent 00dcee2a64
commit 744556c01d
12 changed files with 418 additions and 37 deletions
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20
funcs/func_db.c
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@@ -110,6 +110,12 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
<para>This function will retrieve a value from the Asterisk database
and then remove that key from the database. <variable>DB_RESULT</variable>
will be set to the key's value if it exists.</para>
<note>
<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
is set to <literal>no</literal>, this function can only be read from the
dialplan, and not directly from external protocols. It can, however, be
executed as a write operation (<literal>DB_DELETE(family, key)=ignored</literal>)</para>
</note>
</description>
<see-also>
<ref type="application">DBdel</ref>
@@ -311,10 +317,22 @@ static int function_db_delete(struct ast_channel *chan, const char *cmd,
return 0;
}
/*!
* \brief Wrapper to execute DB_DELETE from a write operation. Allows execution
* even if live_dangerously is disabled.
*/
static int function_db_delete_write(struct ast_channel *chan, const char *cmd, char *parse,
const char *value)
{
/* Throwaway to hold the result from the read */
char buf[128];
return function_db_delete(chan, cmd, parse, buf, sizeof(buf));
}
static struct ast_custom_function db_delete_function = {
.name = "DB_DELETE",
.read = function_db_delete,
.write = function_db_delete_write,
};
static int unload_module(void)
@@ -335,7 +353,7 @@ static int load_module(void)
res |= ast_custom_function_register(&db_function);
res |= ast_custom_function_register(&db_exists_function);
res |= ast_custom_function_register(&db_delete_function);
res |= ast_custom_function_register_escalating(&db_delete_function, AST_CFE_READ);
res |= ast_custom_function_register(&db_keys_function);
return res;