Monitor /data/system/packages.xml

Reinstalling system apps as data creates tons of issues.
Calling pm path <pkg> is extremely expensive and doesn't work in post-fs-data.
Parse through packages.xml to get APK path and UID at the same time.
As a bonus, we don't need to traverse /data/app for packages anymore.

native/jni/magiskhide/hide_utils.cpp

@@ -20,7 +20,6 @@ using namespace std;
 // Protect access to both hide_list and hide_uid
 pthread_mutex_t list_lock;
 vector<string> hide_list;
-set<int> hide_uid;
 
 // Treat GMS separately as we're only interested in one component
 int gms_uid = -1;
@@ -60,21 +59,6 @@ static void hide_sensitive_props() {
 	}
 }
 
-/*
- * Bionic's atoi runs through strtol().
- * Use our own implementation for faster conversion.
- */
-static inline int parse_int(const char *s) {
-	int val = 0;
-	char c;
-	while ((c = *(s++))) {
-		if (c > '9' || c < '0')
-			return -1;
-		val = val * 10 + c - '0';
-	}
-	return val;
-}
-
 // Leave /proc fd opened as we're going to read from it repeatedly
 static DIR *procfp;
 void crawl_procfs(const function<bool (int)> &fn) {
@@ -148,22 +132,12 @@ static void kill_process(int uid) {
 	});
 }
 
-static int add_pkg_uid(const char *pkg) {
+static int get_pkg_uid(const char *pkg) {
 	char path[4096];
 	struct stat st;
 	const char *data = SDK_INT >= 24 ? "/data/user_de/0" : "/data/data";
 	sprintf(path, "%s/%s", data, pkg);
-	if (stat(path, &st) == 0) {
-		hide_uid.insert(st.st_uid);
-		return st.st_uid;
-	}
-	return -1;
-}
-
-void refresh_uid() {
-	hide_uid.clear();
-	for (auto &s : hide_list)
-		add_pkg_uid(s.c_str());
+	return stat(path, &st) ? -1 : st.st_uid;
 }
 
 void clean_magisk_props() {
@@ -192,7 +166,7 @@ int add_list(const char *pkg) {
 	{
 		MutexGuard lock(list_lock);
 		hide_list.emplace_back(pkg);
-		uid = add_pkg_uid(pkg);
+		uid = get_pkg_uid(pkg);
 	}
 
 	kill_process(uid);
@@ -235,17 +209,17 @@ int rm_list(int client) {
 	int ret = rm_list(pkg);
 	free(pkg);
 	if (ret == DAEMON_SUCCESS)
-		update_inotify_mask(true);
+		update_inotify_mask();
 	return ret;
 }
 
 static int init_list(void *, int, char **data, char**) {
 	LOGI("hide_list init: [%s]\n", *data);
 	hide_list.emplace_back(*data);
-	kill_process(*data);
-	int uid = add_pkg_uid(*data);
+	int uid = get_pkg_uid(*data);
 	if (strcmp(*data, SAFETYNET_PKG) == 0)
 		gms_uid = uid;
+	kill_process(uid);
 	return 0;
 }
 

native/jni/magiskhide/magiskhide.h

@@ -26,7 +26,7 @@ int rm_list(int client);
 void ls_list(int client);
 
 // Update APK list for inotify
-void update_inotify_mask(bool refresh = false);
+void update_inotify_mask();
 
 // Process monitor
 void proc_monitor();
@@ -34,7 +34,6 @@ void proc_monitor();
 // Utility functions
 void manage_selinux();
 void clean_magisk_props();
-void refresh_uid();
 void crawl_procfs(const std::function<bool (int)> &fn);
 
 static inline int get_uid(const int pid) {
@@ -49,10 +48,24 @@ static inline int get_uid(const int pid) {
 	return st.st_uid % 100000;
 }
 
+/*
+ * Bionic's atoi runs through strtol().
+ * Use our own implementation for faster conversion.
+ */
+static inline int parse_int(const char *s) {
+	int val = 0;
+	char c;
+	while ((c = *(s++))) {
+		if (c > '9' || c < '0')
+			return -1;
+		val = val * 10 + c - '0';
+	}
+	return val;
+}
+
 extern bool hide_enabled;
 extern pthread_mutex_t list_lock;
 extern std::vector<std::string> hide_list;
-extern std::set<int> hide_uid;
 extern int gms_uid;
 
 enum {

native/jni/magiskhide/proc_monitor.cpp

@@ -21,6 +21,7 @@
 #include <vector>
 #include <string>
 #include <map>
+#include <algorithm>
 
 #include <magisk.h>
 #include <utils.h>
@@ -32,6 +33,7 @@ using namespace std;
 extern char *system_block, *vendor_block, *data_block;
 
 static int inotify_fd = -1;
+static set<int> hide_uid;
 
 // Workaround for the lack of pthread_cancel
 static void term_thread(int) {
@@ -189,102 +191,67 @@ static int xinotify_add_watch(int fd, const char* path, uint32_t mask) {
 	return ret;
 }
 
-static char *append_path(char *eof, const char *name) {
-	*(eof++) = '/';
-	char c;
-	while ((c = *(name++)))
-		*(eof++) = c;
-	*eof = '\0';
-	return eof;
-}
-
-#define DATA_APP "/data/app"
 static int new_inotify;
-static int data_app_wd;
-static vector<bool> app_in_data;
-static void find_apks(char *path, char *eof) {
-	DIR *dir = opendir(path);
-	if (dir == nullptr)
-		return;
+static const string_view APK_EXT(".apk");
 
+static bool parse_packages_xml(string_view &s) {
+	if (!str_starts(s, "<package "))
+		return true;
+	/* <package key1="value1" key2="value2"....> */
+	char *start = (char *) s.data();
+	start[s.length() - 2] = '\0';  /* Remove trailing '>' */
+	char key[32], value[1024];
+	char *tok;
+	start += 9;  /* Skip '<package ' */
+	while ((tok = strtok_r(nullptr, " ", &start))) {
+		sscanf(tok, "%[^=]=\"%[^\"]", key, value);
+		string_view value_view(value);
+		if (strcmp(key, "name") == 0) {
+			if (std::count(hide_list.begin(), hide_list.end(), value_view) == 0)
+				return true;
+		} else if (strcmp(key, "codePath") == 0) {
+			if (ends_with(value_view, APK_EXT)) {
+				// Directly add to inotify list
+				xinotify_add_watch(new_inotify, value, IN_OPEN);
+			} else {
+				DIR *dir = opendir(value);
+				if (dir == nullptr)
+					return true;
 				struct dirent *entry;
-	char *dash;
-	for (; (entry = xreaddir(dir)); *eof = '\0') {
-		if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
-			continue;
-		if (entry->d_type == DT_DIR) {
-			find_apks(path, append_path(eof, entry->d_name));
-		} else if (strend(entry->d_name, ".apk") == 0) {
-			append_path(eof, entry->d_name);
-			/* Supported path will be in either format:
-			 * /data/app/[pkg]-[hash or 1 or 2]/base.apk
-			 * /data/app/[pkg]-[1 or 2].apk */
-			if ((dash = strchr(path, '-')) == nullptr)
-				continue;
-			*dash = '\0';
-			for (int i = 0; i < hide_list.size(); ++i) {
-				if (hide_list[i] == path + sizeof(DATA_APP)) {
-					*dash = '-';
-					append_path(eof, entry->d_name);
-					xinotify_add_watch(new_inotify, path, IN_OPEN | IN_DELETE);
-					app_in_data[i] = true;
-					break;
-				}
-			}
-			*dash = '-';
+				while ((entry = xreaddir(dir))) {
+					if (ends_with(entry->d_name, APK_EXT)) {
+						strcpy(value + value_view.length(), "/");
+						strcpy(value + value_view.length() + 1, entry->d_name);
+						xinotify_add_watch(new_inotify, value, IN_OPEN);
 						break;
 					}
 				}
 				closedir(dir);
+			}
+		} else if (strcmp(key, "userId") == 0 || strcmp(key, "sharedUserId") == 0) {
+			hide_uid.insert(parse_int(value));
+		}
+	}
+	return true;
 }
 
-// Iterate through /data/app and search all .apk files
-void update_inotify_mask(bool refresh) {
-	char buf[4096];
-
+void update_inotify_mask() {
 	new_inotify = inotify_init();
 	if (new_inotify < 0) {
 		LOGE("proc_monitor: Cannot initialize inotify: %s\n", strerror(errno));
 		term_thread(TERM_THREAD);
 	}
+	fcntl(new_inotify, F_SETFD, FD_CLOEXEC);
 
 	LOGD("proc_monitor: Updating inotify list\n");
-	strcpy(buf, DATA_APP);
-	app_in_data.clear();
-	bool reinstall = false;
 	{
 		MutexGuard lock(list_lock);
-		app_in_data.resize(hide_list.size(), false);
-		find_apks(buf, buf + sizeof(DATA_APP) - 1);
-		// Stop monitoring /data/app
-		if (inotify_fd >= 0)
-			inotify_rm_watch(inotify_fd, data_app_wd);
-		// All apps on the hide list should be installed in data
-		auto it = hide_list.begin();
-		for (bool in_data : app_in_data) {
-			if (!in_data) {
-				if (reinstall_apk(it->c_str()) != 0) {
-					// Reinstallation failed, remove from hide list
-					hide_list.erase(it);
-					refresh = true;
-					continue;
-				}
-				reinstall = true;
-			}
-			it++;
-		}
-		if (refresh && !reinstall)
-			refresh_uid();
-	}
-	if (reinstall) {
-		// Rerun detection
-		close(new_inotify);
-		update_inotify_mask(refresh);
-		return;
+		hide_uid.clear();
+		file_readline("/data/system/packages.xml", parse_packages_xml, true);
 	}
 
-	// Add /data/app itself to the watch list to detect app (un)installations/updates
-	data_app_wd = xinotify_add_watch(new_inotify, DATA_APP, IN_CLOSE_WRITE | IN_MOVED_TO | IN_DELETE);
+	// Add /data/system to monitor /data/system/packages.xml
+	xinotify_add_watch(new_inotify, "/data/system", IN_CLOSE_WRITE);
 
 	int tmp = inotify_fd;
 	inotify_fd = new_inotify;
@@ -306,20 +273,19 @@ void proc_monitor() {
 
 	// Read inotify events
 	ssize_t len;
-	char buf[4096];
+	char buf[512];
 	auto event = reinterpret_cast<inotify_event *>(buf);
 	while ((len = read(inotify_fd, buf, sizeof(buf))) >= 0) {
 		if (len < sizeof(*event))
 			continue;
-
 		if (event->mask & IN_OPEN) {
 			// Since we're just watching files,
 			// extracting file name is not possible from querying event
 			MutexGuard lock(list_lock);
 			crawl_procfs(process_pid);
-		} else if (!(event->mask & IN_IGNORED)) {
-			LOGD("proc_monitor: inotify: /data/app change detected\n");
-			update_inotify_mask(true);
+		} else if ((event->mask & IN_CLOSE_WRITE) && strcmp(event->name, "packages.xml") == 0) {
+			LOGD("proc_monitor: /data/system/packages.xml updated\n");
+			update_inotify_mask();
 		}
 	}
 	PLOGE("proc_monitor: read inotify");

native/jni/utils/include/utils.h

@@ -201,6 +201,8 @@ int exec_command_sync(Args &&...args) {
 	return exec_command_sync(exec, args...);
 }
 
+bool ends_with(const std::string_view &s1, const std::string_view &s2);
+
 #endif
 
 #endif

native/jni/utils/misc.cpp

@@ -236,3 +236,9 @@ void set_nice_name(const char *name) {
 	strlcpy(argv0, name, name_len);
 	prctl(PR_SET_NAME, name);
 }
+
+bool ends_with(const std::string_view &s1, const std::string_view &s2) {
+	unsigned l1 = s1.length();
+	unsigned l2 = s2.length();
+	return l1 < l2 ? false : s1.compare(l1 - l2, l2, s2) == 0;
+}