AST-2012-004: Fix an error that allows AMI users to run shell commands sans authorization.

As detailed in the advisory, AMI users without write authorization for SYSTEM class AMI
actions were able to run system commands by going through other AMI commands which did
not require that authorization. Specifically, GetVar and Status allowed users to do this
by setting their variable/s options to the SHELL or EVAL functions.
Also, within 1.8, 10, and trunk there was a similar flaw with the Originate action that
allowed users with originate permission to run MixMonitor and supply a shell command
in the Data argument. That flaw is fixed in those versions of this patch.

(closes issue ASTERISK-17465)
Reported By: David Woolley
Patches:
	162_ami_readfunc_security_r2.diff uploaded by jrose (license 6182)
	18_ami_readfunc_security_r2.diff uploaded by jrose (license 6182)
	10_ami_readfunc_security_r2.diff uploaded by jrose (license 6182)



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.2@363117 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/manager.c

@@ -415,6 +415,19 @@ static struct permalias {
 	{ 0, "none" },
 };
 
+/*! \brief Checks to see if a string which can be used to evaluate functions should be rejected */
+static int check_user_can_execute_function(const char *evaluating, int writepermlist)
+{
+	if (!(writepermlist & EVENT_FLAG_SYSTEM)
+		&& (
+			strstr(evaluating, "SHELL") ||       /* NoOp(${SHELL(rm -rf /)})  */
+			strstr(evaluating, "EVAL")           /* NoOp(${EVAL(${some_var_containing_SHELL})}) */
+		)) {
+		return 0;
+	}
+	return 1;
+}
+
 /*! \brief Convert authority code to a list of options */
 static char *authority_to_str(int authority, struct ast_str **res)
 {
@@ -1918,6 +1931,12 @@ static int action_getvar(struct mansession *s, const struct message *m)
 		return 0;
 	}
 
+	/* We don't want users with insufficient permissions using certain functions. */
+	if (!(check_user_can_execute_function(varname, s->session->writeperm))) {
+		astman_send_error(s, m, "GetVar Access Forbidden: Variable");
+		return 0;
+	}
+
 	if (!ast_strlen_zero(name)) {
 		c = ast_get_channel_by_name_locked(name);
 		if (!c) {
@@ -1985,6 +2004,11 @@ static int action_status(struct mansession *s, const struct message *m)
 	else
 		idText[0] = '\0';
 
+	if (!(check_user_can_execute_function(variables, s->session->writeperm))) {
+		astman_send_error(s, m, "Status Access Forbidden: Variables");
+		return 0;
+	}
+
 	if (all)
 		c = ast_channel_walk_locked(NULL);
 	else {
@@ -2567,6 +2591,24 @@ static int action_originate(struct mansession *s, const struct message *m)
 			}
 		}
 	} else if (!ast_strlen_zero(app)) {
+		int bad_appdata = 0;
+		/* To run the System application (or anything else that goes to shell), you must have the additional System privilege */
+		if (!(s->session->writeperm & EVENT_FLAG_SYSTEM)
+			&& (
+				strcasestr(app, "system") ||      /* System(rm -rf /)
+				                                     TrySystem(rm -rf /)       */
+				strcasestr(app, "exec") ||        /* Exec(System(rm -rf /))
+				                                     TryExec(System(rm -rf /)) */
+				strcasestr(app, "agi") ||         /* AGI(/bin/rm,-rf /)
+				                                     EAGI(/bin/rm,-rf /)       */
+				(strstr(appdata, "SHELL") && (bad_appdata = 1)) ||       /* NoOp(${SHELL(rm -rf /)})  */
+				(strstr(appdata, "EVAL") && (bad_appdata = 1))           /* NoOp(${EVAL(${some_var_containing_SHELL})}) */
+				)) {
+			char error_buf[64];
+			snprintf(error_buf, sizeof(error_buf), "Originate Access Forbidden: %s", bad_appdata ? "Data" : "Application");
+			astman_send_error(s, m, error_buf);
+			return 0;
+		}
 		res = ast_pbx_outgoing_app(tech, format, data, to, app, appdata, &reason, 1, l, n, vars, account, NULL);
 	} else {
 		if (exten && context && pi)