sb2-show can be used to query string variables from the Lua engine - Also introduces a new C function, sb2__read_string_variable_from_lua__(), which can be used to replace getenv() for variables that have been moved or will be moved away from environment

3 files changed, 50 insertions, 2 deletions

diff --git a/luaif/luaif.c b/luaif/luaif.c
index af9ef05..af1bab2 100644
--- a/luaif/luaif.c
+++ b/luaif/luaif.c
@@ -246,6 +246,30 @@ void sb2_lua_init(void)
 	lua_engine_state = LES_READY;
 }
 
+/* Read string variables from lua.
+ * Note that this function is exported from libsb2.so (for sb2-show etc): */
+char *sb2__read_string_variable_from_lua__(const char *name)
+{
+	struct lua_instance *luaif;
+	char *result = NULL;
+
+	luaif = get_lua();
+
+	if (luaif && name && *name) {
+		lua_getglobal(luaif->lua, name);
+		result = (char *)lua_tostring(luaif->lua, -1);
+		if (result) {
+			result = strdup(result);
+		}
+		SB_LOG(SB_LOGLEVEL_DEBUG,
+			"Lua variable %s = '%s', gettop=%d",
+			name, (result ? result : "<NULL>"),
+			lua_gettop(luaif->lua));
+	}
+	return(result);
+}
+
+
 /* "sb.decolonize_path", to be called from lua code */
 static int lua_sb_decolonize_path(lua_State *l)
 {
diff --git a/preload/interface.master b/preload/interface.master
index efe2119..9b43318 100644
--- a/preload/interface.master
+++ b/preload/interface.master
@@ -31,6 +31,7 @@ EXPORT: int sb2show__execve_mods__( \
 	char *file, \
 	char *const *orig_argv, char *const *orig_envp, \
 	char **new_file, char ***new_argv, char ***new_envp)
+EXPORT: char *sb2__read_string_variable_from_lua__(const char *name)
 
 --    FIXME: The following two functions do not have anything to do with path
 --    remapping. Instead the implementations in libsb2.c prevent locking of
diff --git a/utils/sb2-show.c b/utils/sb2-show.c
index 5fb361c..93641d8 100644
--- a/utils/sb2-show.c
+++ b/utils/sb2-show.c
@@ -40,8 +40,10 @@ static void usage_exit(const char *progname, const char *errmsg, int exitstatus)
 		"\tlog-warning 'message'"
 			"\tAdd a warning message to the log\n"
 		"\tverify-pathlist-mappings required-prefix [ignorelist]"
-			"\tread list of paths from stdin and/n"
-			"\t\tcheck that all paths will be mapped to required prefix/n"
+			"\tread list of paths from stdin and\n"
+			"\t\tcheck that all paths will be mapped to required prefix\n"
+		"\tvar variablename"
+			"\tShow value of a string variable\n"
 		"\n'%s' must be executed inside sb2 sandbox"
 			" (see the 'sb2' command)\n",
 		progname, progname, progname);
@@ -49,6 +51,25 @@ static void usage_exit(const char *progname, const char *errmsg, int exitstatus)
 	exit(exitstatus);
 }
 
+static int command_show_variable(
+	int verbose,
+	const char *progname, 
+	const char *varname)
+{
+	char *value = sb2__read_string_variable_from_lua__(varname);
+
+	if (value) {
+		if (verbose) printf("%s = \"%s\"\n", varname, value);
+		else printf("%s\n", value);
+		free(value);
+		return(0);
+	} 
+	/* failed */
+	if (verbose) printf("%s: %s does not exist\n",
+		progname, varname);
+	return(1);
+}
+
 static void command_show_exec(
 	const char *binary_name,
 	const char *fn_name,
@@ -244,6 +265,8 @@ int main(int argc, char *argv[])
 		return command_verify_pathlist_mappings(binary_name,
 			function_name, ignore_directories,
 			verbose, progname, argv + optind + 1);
+	} else if (!strcmp(argv[optind], "var")) {
+		return(command_show_variable(verbose, progname, argv[optind+1]));
 	} else {
 		usage_exit(progname, "Unknown command", 1);
 	}