diff --git a/README-SERIOUSLY.bestpractices.txt b/README-SERIOUSLY.bestpractices.txt
index b470fd66cf57f13aaa0fc559b8b407186d979e6f..281d0d38bfd9be2ae1347eff6f09017873071958 100644
--- a/README-SERIOUSLY.bestpractices.txt
+++ b/README-SERIOUSLY.bestpractices.txt
@@ -26,6 +26,9 @@ Sections
 * Manager Class Authorizations:
         Recognizing potential issues with certain classes of authorization
 
+* Avoid Privilege Escalations:
+        Disable the ability to execute functions that may escalate privileges
+
 ----------------
 Additional Links
 ----------------
@@ -344,3 +347,24 @@ same as the class authorization "system".  Good system configuration, such as
 not running Asterisk as root, can prevent serious problems from arising when
 allowing external connections to originate calls into Asterisk.
 
+===========================
+Avoid Privilege Escalations
+===========================
+
+External control protocols, such as Manager, often have the ability to get and
+set channel variables; which allows the execution of dialplan functions.
+
+Dialplan functions within Asterisk are incredibly powerful, which is wonderful
+for building applications using Asterisk. But during the read or write
+execution, certain diaplan functions do much more. For example, reading the
+SHELL() function can execute arbitrary commands on the system Asterisk is
+running on. Writing to the FILE() function can change any file that Asterisk has
+write access to.
+
+When these functions are executed from an external protocol, that execution
+could result in a privilege escalation. Asterisk can inhibit the execution of
+these functions, if live_dangerously in the [options] section of asterisk.conf
+is set to no.
+
+For backwards compatibility, live_dangerously defaults to yes, and must be
+explicitly set to no to enable this privilege escalation protection.
diff --git a/UPGRADE.txt b/UPGRADE.txt
index 2a29420b490475bad89269932ffa395b444a0379..6f221b9f5f30870f93dcd90790c837f38f6e3b13 100644
--- a/UPGRADE.txt
+++ b/UPGRADE.txt
@@ -19,6 +19,16 @@
 ===
 ===========================================================
 
+from 10.12.3 to 10.12.4:
+
+* Certain dialplan functions have been marked as 'dangerous', and may only be
+  executed from the dialplan. Execution from extenal sources (AMI's GetVar and
+  SetVar actions; etc.) may be inhibited by setting live_dangerously in the
+  [options] section of asterisk.conf to no. SHELL(), channel locking, and direct
+  file read/write functions are marked as dangerous. DB_DELETE() and
+  REALTIME_DESTROY() are marked as dangerous for reads, but can now safely
+  accept writes (which ignore the provided value).
+
 from 10.12.0 to 10.12.1:
 
 * Asterisk would previously not output certain error messages when a remote
diff --git a/configs/asterisk.conf.sample b/configs/asterisk.conf.sample
index cc9933044aa0ee0f541fa60dffeb38a140d87f27..b0996f2cc41c8f5dce1effabaffddc14ee90a740 100644
--- a/configs/asterisk.conf.sample
+++ b/configs/asterisk.conf.sample
@@ -74,6 +74,12 @@ documentation_language = en_US	; Set the language you want documentation
 ;lockconfdir = no		; Protect the directory containing the
 				; configuration files (/etc/asterisk) with a
 				; lock.
+;live_dangerously = no		; Enable the execution of 'dangerous' dialplan
+				; functions from external sources (AMI,
+				; etc.) These functions (such as SHELL) are
+				; considered dangerous because they can allow
+				; privilege escalation.
+				; Default yes, for backward compatability.
 
 ; Changing the following lines may compromise your security.
 ;[files]
diff --git a/funcs/func_db.c b/funcs/func_db.c
index 20c8829a616b1cf7c2ee40748de5bab051f2f73a..ebe58f02e3844caa72114913da6bf4fd4ea2d4ad 100644
--- a/funcs/func_db.c
+++ b/funcs/func_db.c
@@ -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;
diff --git a/funcs/func_env.c b/funcs/func_env.c
index cbc80e8d809880e1a615284f8cbf05267d9ba8bc..7fc1823ce9f01f1d5592a65a32920a84ed12167b 100644
--- a/funcs/func_env.c
+++ b/funcs/func_env.c
@@ -71,6 +71,11 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 			<parameter name="filename" required="true" />
 		</syntax>
 		<description>
+			<note>
+				<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
+				is set to <literal>no</literal>, this function can only be executed from the
+				dialplan, and not directly from external protocols.</para>
+			</note>
 		</description>
 	</function>
 	<function name="FILE" language="en_US">
@@ -167,6 +172,11 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 			<para>    Set(FILE(/tmp/foo.txt,-1,,l)=bar)</para>
 			<para>    ; Append "bar" to the file with a newline</para>
 			<para>    Set(FILE(/tmp/foo.txt,,,al)=bar)</para>
+			<note>
+				<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
+				is set to <literal>no</literal>, this function can only be executed from the
+				dialplan, and not directly from external protocols.</para>
+			</note>
 		</description>
 		<see-also>
 			<ref type="function">FILE_COUNT_LINE</ref>
@@ -197,6 +207,11 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 		</syntax>
 		<description>
 			<para>Returns the number of lines, or <literal>-1</literal> on error.</para>
+			<note>
+				<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
+				is set to <literal>no</literal>, this function can only be executed from the
+				dialplan, and not directly from external protocols.</para>
+			</note>
 		</description>
 		<see-also>
 			<ref type="function">FILE</ref>
@@ -216,6 +231,11 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 			<para>'d' - DOS "\r\n" format</para>
 			<para>'m' - Macintosh "\r" format</para>
 			<para>'x' - Cannot be determined</para>
+			<note>
+				<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
+				is set to <literal>no</literal>, this function can only be executed from the
+				dialplan, and not directly from external protocols.</para>
+			</note>
 		</description>
 		<see-also>
 			<ref type="function">FILE</ref>
@@ -1258,10 +1278,10 @@ static int load_module(void)
 	int res = 0;
 
 	res |= ast_custom_function_register(&env_function);
-	res |= ast_custom_function_register(&stat_function);
-	res |= ast_custom_function_register(&file_function);
-	res |= ast_custom_function_register(&file_count_line_function);
-	res |= ast_custom_function_register(&file_format_function);
+	res |= ast_custom_function_register_escalating(&stat_function, AST_CFE_READ);
+	res |= ast_custom_function_register_escalating(&file_function, AST_CFE_BOTH);
+	res |= ast_custom_function_register_escalating(&file_count_line_function, AST_CFE_READ);
+	res |= ast_custom_function_register_escalating(&file_format_function, AST_CFE_READ);
 
 	return res;
 }
diff --git a/funcs/func_lock.c b/funcs/func_lock.c
index 92d57768ffc041b1e0ea7ff41b14d8c10c9784c3..40deb20fec11a3efb4a41ad4e865bd1bd51eed2a 100644
--- a/funcs/func_lock.c
+++ b/funcs/func_lock.c
@@ -59,6 +59,11 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 			Returns <literal>1</literal> if the lock was obtained or <literal>0</literal> on error.</para>
 			<note><para>To avoid the possibility of a deadlock, LOCK will only attempt to
 			obtain the lock for 3 seconds if the channel already has another lock.</para></note>
+			<note>
+				<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
+				is set to <literal>no</literal>, this function can only be executed from the
+				dialplan, and not directly from external protocols.</para>
+			</note>
 		</description>
 	</function>
 	<function name="TRYLOCK" language="en_US">
@@ -72,6 +77,11 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 			<para>Attempts to grab a named lock exclusively, and prevents other channels
 			from obtaining the same lock.  Returns <literal>1</literal> if the lock was 
 			available or <literal>0</literal> otherwise.</para>
+			<note>
+				<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
+				is set to <literal>no</literal>, this function can only be executed from the
+				dialplan, and not directly from external protocols.</para>
+			</note>
 		</description>
 	</function>
 	<function name="UNLOCK" language="en_US">
@@ -86,6 +96,11 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 			had a lock or <literal>0</literal> otherwise.</para>
 			<note><para>It is generally unnecessary to unlock in a hangup routine, as any locks 
 			held are automatically freed when the channel is destroyed.</para></note>
+			<note>
+				<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
+				is set to <literal>no</literal>, this function can only be executed from the
+				dialplan, and not directly from external protocols.</para>
+			</note>
 		</description>
 	</function>
  ***/
@@ -502,9 +517,9 @@ static int unload_module(void)
 
 static int load_module(void)
 {
-	int res = ast_custom_function_register(&lock_function);
-	res |= ast_custom_function_register(&trylock_function);
-	res |= ast_custom_function_register(&unlock_function);
+	int res = ast_custom_function_register_escalating(&lock_function, AST_CFE_READ);
+	res |= ast_custom_function_register_escalating(&trylock_function, AST_CFE_READ);
+	res |= ast_custom_function_register_escalating(&unlock_function, AST_CFE_READ);
 
 	if (ast_pthread_create_background(&broker_tid, NULL, lock_broker, NULL)) {
 		ast_log(LOG_ERROR, "Failed to start lock broker thread. Unloading func_lock module.\n");
diff --git a/funcs/func_realtime.c b/funcs/func_realtime.c
index a1b6d200eecfa3d607416a2122cee9503f499507..6f7e55053262f93e9948558eb87438d397188d25 100644
--- a/funcs/func_realtime.c
+++ b/funcs/func_realtime.c
@@ -115,6 +115,12 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 		<description>
 			<para>This function acts in the same way as REALTIME(....) does, except that
 			it destroys the matched record in the RT engine.</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>REALTIME_DESTROY(family, fieldmatch)=ignored</literal>)</para>
+			</note>
 		</description>
 		<see-also>
 			<ref type="function">REALTIME</ref>
@@ -432,18 +438,32 @@ static int function_realtime_readdestroy(struct ast_channel *chan, const char *c
 		return -1;
 	}
 
-	resultslen = 0;
-	n = 0;
-	for (var = head; var; n++, var = var->next)
-		resultslen += strlen(var->name) + strlen(var->value);
-	/* add space for delimiters and final '\0' */
-	resultslen += n * (strlen(args.delim1) + strlen(args.delim2)) + 1;
+	if (len > 0) {
+		resultslen = 0;
+		n = 0;
+		for (var = head; var; n++, var = var->next) {
+			resultslen += strlen(var->name) + strlen(var->value);
+		}
+		/* add space for delimiters and final '\0' */
+		resultslen += n * (strlen(args.delim1) + strlen(args.delim2)) + 1;
+
+		if (resultslen > len) {
+			/* Unfortunately this does mean that we cannot destroy
+			 * the row anymore. But OTOH, we're not destroying
+			 * someones data without giving him the chance to look
+			 * at it. */
+			ast_log(LOG_WARNING, "Failed to fetch/destroy. Realtime data is too large: need %zu, have %zu.\n", resultslen, len);
+			return -1;
+		}
 
-	out = ast_str_alloca(resultslen);
-	for (var = head; var; var = var->next) {
-		ast_str_append(&out, 0, "%s%s%s%s", var->name, args.delim2, var->value, args.delim1);
+		/* len is going to be sensible, so we don't need to check for
+		 * stack overflows here. */
+		out = ast_str_alloca(resultslen);
+		for (var = head; var; var = var->next) {
+			ast_str_append(&out, 0, "%s%s%s%s", var->name, args.delim2, var->value, args.delim1);
+		}
+		ast_copy_string(buf, ast_str_buffer(out), len);
 	}
-	ast_copy_string(buf, ast_str_buffer(out), len);
 
 	ast_destroy_realtime(args.family, args.fieldmatch, args.value, SENTINEL);
 	ast_variables_destroy(head);
@@ -454,6 +474,15 @@ static int function_realtime_readdestroy(struct ast_channel *chan, const char *c
 	return 0;
 }
 
+/*!
+ * \brief Wrapper to execute REALTIME_DESTROY from a write operation. Allows
+ * execution even if live_dangerously is disabled.
+ */
+static int function_realtime_writedestroy(struct ast_channel *chan, const char *cmd, char *data, const char *value)
+{
+	return function_realtime_readdestroy(chan, cmd, data, NULL, 0);
+}
+
 static struct ast_custom_function realtime_function = {
 	.name = "REALTIME",
 	.read = function_realtime_read,
@@ -479,6 +508,7 @@ static struct ast_custom_function realtime_store_function = {
 static struct ast_custom_function realtime_destroy_function = {
 	.name = "REALTIME_DESTROY",
 	.read = function_realtime_readdestroy,
+	.write = function_realtime_writedestroy,
 };
 
 static int unload_module(void)
@@ -497,7 +527,7 @@ static int load_module(void)
 	int res = 0;
 	res |= ast_custom_function_register(&realtime_function);
 	res |= ast_custom_function_register(&realtime_store_function);
-	res |= ast_custom_function_register(&realtime_destroy_function);
+	res |= ast_custom_function_register_escalating(&realtime_destroy_function, AST_CFE_READ);
 	res |= ast_custom_function_register(&realtimefield_function);
 	res |= ast_custom_function_register(&realtimehash_function);
 	return res;
diff --git a/funcs/func_shell.c b/funcs/func_shell.c
index bad10b381e269019623f68efbe70252f75e8d0ad..e403efc2e82cf3a4d5d24e1b6e53869bfb9ec1e2 100644
--- a/funcs/func_shell.c
+++ b/funcs/func_shell.c
@@ -88,11 +88,17 @@ static int shell_helper(struct ast_channel *chan, const char *cmd, char *data,
 		</syntax>
 		<description>
 			<para>Collects the output generated by a command executed by the system shell</para>
-			<para>Example:  <literal>Set(foo=${SHELL(echo \bar\)})</literal></para>
-			<note><para>The command supplied to this function will be executed by the
-			system's shell, typically specified in the SHELL environment variable. There
-			are many different system shells available with somewhat different behaviors,
-			so the output generated by this function may vary between platforms.</para></note>
+			<para>Example:  <literal>Set(foo=${SHELL(echo bar)})</literal></para>
+			<note>
+				<para>The command supplied to this function will be executed by the
+				system's shell, typically specified in the SHELL environment variable. There
+				are many different system shells available with somewhat different behaviors,
+				so the output generated by this function may vary between platforms.</para>
+
+				<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
+				is set to <literal>no</literal>, this function can only be executed from the
+				dialplan, and not directly from external protocols.</para>
+			</note>
 		</description>
 
 	</function>
@@ -109,7 +115,7 @@ static int unload_module(void)
 
 static int load_module(void)
 {
-	return ast_custom_function_register(&shell_function);
+	return ast_custom_function_register_escalating(&shell_function, AST_CFE_READ);
 }
 
 AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Collects the output generated by a command executed by the system shell");
diff --git a/include/asterisk/pbx.h b/include/asterisk/pbx.h
index 02b0654f77fcaef5466f12db3ae06349f0a91037..8b949fa0224ebace374325883a4cad26d9ee6642 100644
--- a/include/asterisk/pbx.h
+++ b/include/asterisk/pbx.h
@@ -1138,16 +1138,44 @@ 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
  */
@@ -1261,6 +1289,32 @@ 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
diff --git a/main/asterisk.c b/main/asterisk.c
index 669ae462c793ffcc09cc7e014631aad261448d7e..ed60d9cae5ca521f4a7b4fdc81490165e8c84ea7 100644
--- a/main/asterisk.c
+++ b/main/asterisk.c
@@ -3033,6 +3033,8 @@ static void ast_readconfig(void)
 		unsigned int dbdir:1;
 		unsigned int keydir:1;
 	} found = { 0, 0 };
+	/* Default to true for backward compatibility */
+	int live_dangerously = 1;
 
 	if (ast_opt_override_config) {
 		cfg = ast_config_load2(ast_config_AST_CONFIG_FILE, "" /* core, can't reload */, config_flags);
@@ -3245,8 +3247,11 @@ static void ast_readconfig(void)
 			ast_set2_flag(&ast_options, ast_true(v->value), AST_OPT_FLAG_HIDE_CONSOLE_CONNECT);
 		} else if (!strcasecmp(v->name, "lockconfdir")) {
 			ast_set2_flag(&ast_options, ast_true(v->value),	AST_OPT_FLAG_LOCK_CONFIG_DIR);
+		} else if (!strcasecmp(v->name, "live_dangerously")) {
+			live_dangerously = ast_true(v->value);
 		}
 	}
+	pbx_live_dangerously(live_dangerously);
 	for (v = ast_variable_browse(cfg, "compat"); v; v = v->next) {
 		float version;
 		if (sscanf(v->value, "%30f", &version) != 1) {
diff --git a/main/pbx.c b/main/pbx.c
index 069031d2f284283f20c9e6d318ad8f48f5f42ee2..02ae1385863f5e4d1caaeabb36465ebf6293693b 100644
--- a/main/pbx.c
+++ b/main/pbx.c
@@ -821,6 +821,17 @@ static struct ast_taskprocessor *device_state_tps;
 
 AST_THREADSTORAGE(switch_data);
 AST_THREADSTORAGE(extensionstate_buf);
+/*!
+ * \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 ast_exten: An extension
@@ -1287,6 +1298,19 @@ static int totalcalls;
 
 static AST_RWLIST_HEAD_STATIC(acf_root, ast_custom_function);
 
+/*!
+ * \brief Extra information for an \ref ast_custom_function holding privilege
+ * escalation information. Kept in a separate structure for ABI compatibility.
+ */
+struct ast_custom_escalating_function {
+	AST_RWLIST_ENTRY(ast_custom_escalating_function) list;
+	const struct ast_custom_function *acf;
+	unsigned int read_escalates:1;
+	unsigned int write_escalates:1;
+};
+
+static AST_RWLIST_HEAD_STATIC(escalation_root, ast_custom_escalating_function);
+
 /*! \brief Declaration of builtin applications */
 static struct pbx_builtin {
 	char name[AST_MAX_APP];
@@ -3880,6 +3904,7 @@ struct ast_custom_function *ast_custom_function_find(const char *name)
 int ast_custom_function_unregister(struct ast_custom_function *acf)
 {
 	struct ast_custom_function *cur;
+	struct ast_custom_escalating_function *cur_escalation;
 
 	if (!acf) {
 		return -1;
@@ -3896,9 +3921,64 @@ int ast_custom_function_unregister(struct ast_custom_function *acf)
 	}
 	AST_RWLIST_UNLOCK(&acf_root);
 
+	/* Remove from the escalation list */
+	AST_RWLIST_WRLOCK(&escalation_root);
+	AST_RWLIST_TRAVERSE_SAFE_BEGIN(&escalation_root, cur_escalation, list) {
+		if (cur_escalation->acf == acf) {
+			AST_RWLIST_REMOVE_CURRENT(list);
+			break;
+		}
+	}
+	AST_RWLIST_TRAVERSE_SAFE_END;
+	AST_RWLIST_UNLOCK(&escalation_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) {
+	int res = 0;
+	struct ast_custom_escalating_function *cur_escalation;
+
+	AST_RWLIST_RDLOCK(&escalation_root);
+	AST_RWLIST_TRAVERSE(&escalation_root, cur_escalation, list) {
+		if (cur_escalation->acf == acf) {
+			res = cur_escalation->read_escalates;
+			break;
+		}
+	}
+	AST_RWLIST_UNLOCK(&escalation_root);
+	return res;
+}
+
+/*!
+ * \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) {
+	int res = 0;
+	struct ast_custom_escalating_function *cur_escalation;
+
+	AST_RWLIST_RDLOCK(&escalation_root);
+	AST_RWLIST_TRAVERSE(&escalation_root, cur_escalation, list) {
+		if (cur_escalation->acf == acf) {
+			res = cur_escalation->write_escalates;
+			break;
+		}
+	}
+	AST_RWLIST_UNLOCK(&escalation_root);
+	return res;
+}
+
 /*! \internal
  *  \brief Retrieve the XML documentation of a specified ast_custom_function,
  *         and populate ast_custom_function string fields.
@@ -4000,6 +4080,50 @@ int __ast_custom_function_register(struct ast_custom_function *acf, struct ast_m
 	return 0;
 }
 
+int __ast_custom_function_register_escalating(struct ast_custom_function *acf, enum ast_custom_function_escalation escalation, struct ast_module *mod)
+{
+	struct ast_custom_escalating_function *acf_escalation = NULL;
+	int res;
+
+	res = __ast_custom_function_register(acf, mod);
+	if (res != 0) {
+		return -1;
+	}
+
+	if (escalation == AST_CFE_NONE) {
+		/* No escalations; no need to do anything else */
+		return 0;
+	}
+
+	acf_escalation = ast_calloc(1, sizeof(*acf_escalation));
+	if (!acf_escalation) {
+		ast_custom_function_unregister(acf);
+		return -1;
+	}
+
+	acf_escalation->acf = acf;
+	switch (escalation) {
+	case AST_CFE_NONE:
+		break;
+	case AST_CFE_READ:
+		acf_escalation->read_escalates = 1;
+		break;
+	case AST_CFE_WRITE:
+		acf_escalation->write_escalates = 1;
+		break;
+	case AST_CFE_BOTH:
+		acf_escalation->read_escalates = 1;
+		acf_escalation->write_escalates = 1;
+		break;
+	}
+
+	AST_RWLIST_WRLOCK(&escalation_root);
+	AST_RWLIST_INSERT_TAIL(&escalation_root, acf_escalation, list);
+	AST_RWLIST_UNLOCK(&escalation_root);
+
+	return 0;
+}
+
 /*! \brief return a pointer to the arguments of the function,
  * and terminates the function name with '\\0'
  */
@@ -4021,6 +4145,124 @@ static char *func_args(char *function)
 	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;
+}
+
+/*!
+ * \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);
@@ -4033,6 +4275,8 @@ int ast_func_read(struct ast_channel *chan, const char *function, char *workspac
 		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);
@@ -4070,6 +4314,8 @@ int ast_func_read2(struct ast_channel *chan, const char *function, struct ast_st
 		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);
@@ -4109,11 +4355,13 @@ int ast_func_write(struct ast_channel *chan, const char *function, const char *v
 	char *args = func_args(copy);
 	struct ast_custom_function *acfptr = ast_custom_function_find(copy);
 
-	if (acfptr == NULL)
+	if (acfptr == NULL) {
 		ast_log(LOG_ERROR, "Function %s not registered\n", copy);
-	else if (!acfptr->write)
+	} else if (!acfptr->write) {
 		ast_log(LOG_ERROR, "Function %s cannot be written to\n", copy);
-	else {
+	} 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)
diff --git a/main/tcptls.c b/main/tcptls.c
index df4e7ad5ea13a84178a1465069ec751932e27301..452cbf2d278461b8a2a819b6c0027c8c261e8e57 100644
--- a/main/tcptls.c
+++ b/main/tcptls.c
@@ -48,6 +48,7 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #include "asterisk/options.h"
 #include "asterisk/manager.h"
 #include "asterisk/astobj2.h"
+#include "asterisk/pbx.h"
 
 /*! \brief
  * replacement read/write functions for SSL support.
@@ -161,6 +162,16 @@ static void *handle_tcptls_connection(void *data)
 	char err[256];
 #endif
 
+	/* TCP/TLS connections are associated with external protocols, and
+	 * should not be allowed to execute 'dangerous' functions. This may
+	 * need to be pushed down into the individual protocol handlers, but
+	 * this seems like a good general policy.
+	 */
+	if (ast_thread_inhibit_escalations()) {
+		ast_log(LOG_ERROR, "Failed to inhibit privilege escalations; killing connection\n");
+		return NULL;
+	}
+
 	/*
 	* open a FILE * as appropriate.
 	*/