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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.

(closes issue ASTERISK-22905)
Review: http://reviewboard.digium.internal/r/432/
........

Merged revisions 403913 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@403917 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
David M. Lee
2013-12-16 17:14:14 +00:00
parent faf4f6187b
commit a9ee948e90
12 changed files with 472 additions and 37 deletions
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54
include/asterisk/pbx.h
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@@ -1309,16 +1309,44 @@ struct ast_custom_function* ast_custom_function_find(const char *name);
*/
int ast_custom_function_unregister(struct ast_custom_function *acf);
/*!
* \brief Description of the ways in which a function may escalate privileges.
*/
enum ast_custom_function_escalation {
AST_CFE_NONE,
AST_CFE_READ,
AST_CFE_WRITE,
AST_CFE_BOTH,
};
/*!
* \brief Register a custom function
*/
#define ast_custom_function_register(acf) __ast_custom_function_register(acf, ast_module_info->self)
/*!
* \brief Register a custom function which requires escalated privileges.
*
* Examples would be SHELL() (for which a read needs permission to execute
* arbitrary code) or FILE() (for which write needs permission to change files
* on the filesystem).
*/
#define ast_custom_function_register_escalating(acf, escalation) __ast_custom_function_register_escalating(acf, escalation, ast_module_info->self)
/*!
* \brief Register a custom function
*/
int __ast_custom_function_register(struct ast_custom_function *acf, struct ast_module *mod);
/*!
* \brief Register a custom function which requires escalated privileges.
*
* Examples would be SHELL() (for which a read needs permission to execute
* arbitrary code) or FILE() (for which write needs permission to change files
* on the filesystem).
*/
int __ast_custom_function_register_escalating(struct ast_custom_function *acf, enum ast_custom_function_escalation escalation, struct ast_module *mod);
/*!
* \brief Retrieve the number of active calls
*/
@@ -1432,6 +1460,32 @@ unsigned int ast_hashtab_hash_contexts(const void *obj);
*/
char *ast_complete_applications(const char *line, const char *word, int state);
/*!
* \brief Enable/disable the execution of 'dangerous' functions from external
* protocols (AMI, etc.).
*
* These dialplan functions (such as \c SHELL) provide an opportunity for
* privilege escalation. They are okay to invoke from the dialplan, but external
* protocols with permission controls should not normally invoke them.
*
* This function can globally enable/disable the execution of dangerous
* functions from external protocols.
*
* \param new_live_dangerously If true, enable the execution of escalating
* functions from external protocols.
*/
void pbx_live_dangerously(int new_live_dangerously);
/*!
* \brief Inhibit (in the current thread) the execution of dialplan functions
* which cause privilege escalations. If pbx_live_dangerously() has been
* called, this function has no effect.
*
* \return 0 if successfuly marked current thread.
* \return Non-zero if marking current thread failed.
*/
int ast_thread_inhibit_escalations(void);
#if defined(__cplusplus) || defined(c_plusplus)
}
#endif