Add new --install-module command

Close #2253

native/jni/core/magisk.cpp

@@ -21,10 +21,11 @@ Options:
    -v                        print running daemon version
    -V                        print running daemon version code
    --list                    list all available applets
-   --daemon                  manually start magisk daemon
    --remove-modules          remove all modules and reboot
+   --install-module ZIP      install a module zip file
 
 Advanced Options (Internal APIs):
+   --daemon                  manually start magisk daemon
    --[init trigger]          start service for init trigger
                              Supported init triggers:
                              post-fs-data, service, boot-complete
@@ -116,6 +117,8 @@ int magisk_main(int argc, char *argv[]) {
 		char *path = read_string(fd);
 		printf("%s\n", path);
 		return 0;
+	} else if (argc >= 3 && argv[1] == "--install-module"sv) {
+		install_module(argv[2]);
 	}
 #if 0
 	/* Entry point for testing stuffs */

native/jni/core/scripting.cpp

@@ -92,3 +92,40 @@ void install_apk(const char *apk) {
 	sprintf(cmds, install_script, apk);
 	exec_command_sync(exec, BBEXEC_CMD, "-c", cmds);
 }
+
+[[noreturn]] static void abort(const char *msg) {
+	fprintf(stderr, "%s\n\n", msg);
+	exit(1);
+}
+
+constexpr char install_module_script[] = R"EOF(
+. /data/adb/magisk/util_functions.sh
+install_module
+exit 0
+)EOF";
+
+void install_module(const char *file) {
+	if (getuid() != 0)
+		abort("Run this command with root");
+	if (access(DATABIN, F_OK) ||
+		access(DATABIN "/busybox", X_OK) ||
+		access(DATABIN "/util_functions.sh", F_OK))
+		abort("Incomplete Magisk install");
+	if (access(file, F_OK)) {
+		char msg[4096];
+		sprintf(msg, "'%s' does not exist", file);
+		abort(msg);
+	}
+
+	setenv("OUTFD", "1", true);
+	setenv("ZIPFILE", file, true);
+	setenv("ASH_STANDALONE", "1", 1);
+
+	int fd = xopen("/dev/null", O_RDONLY);
+	xdup2(fd, STDERR_FILENO);
+	close(fd);
+
+	const char *argv[] = { BBEXEC_CMD, "-c", install_module_script };
+	execve(argv[0], (char **) argv, environ);
+	abort("Failed to execute BusyBox shell");
+}

native/jni/include/daemon.hpp

@@ -69,3 +69,4 @@ void exec_script(const char *script);
 void exec_common_scripts(const char *stage);
 void exec_module_scripts(const char *stage, const std::vector<std::string> &module_list);
 void install_apk(const char *apk);
+[[noreturn]] void install_module(const char *file);