Add new Zygisk API to get module dir

native/jni/core/module.cpp

@@ -541,15 +541,7 @@ static void inject_magisk_bins(root_node *system) {
         delete bin->extract(init_applet[i]);
 }
 
-struct module_info {
-    string name;
-    int z32 = -1;
-#if defined(__LP64__)
-    int z64 = -1;
-#endif
-};
-
-static vector<module_info> *modules;
+vector<module_info> *module_list;
 int app_process_32 = -1;
 int app_process_64 = -1;
 
@@ -577,8 +569,8 @@ void magic_mount() {
 
     char buf[4096];
     LOGI("* Loading modules\n");
-    if (modules) {
-        for (const auto &m : *modules) {
+    if (module_list) {
+        for (const auto &m : *module_list) {
             const char *module = m.name.data();
             char *b = buf + sprintf(buf, "%s/" MODULEMNT "/%s/", MAGISKTMP.data(), module);
 
@@ -732,7 +724,7 @@ static void collect_modules(bool open_zygisk) {
             }
         }
         info.name = entry->d_name;
-        modules->push_back(info);
+        module_list->push_back(info);
     });
     if (open_zygisk && zygisk_enabled) {
         bool use_memfd = true;
@@ -752,7 +744,7 @@ static void collect_modules(bool open_zygisk) {
             }
             return fd;
         };
-        std::for_each(modules->begin(), modules->end(), [&](module_info &info) {
+        std::for_each(module_list->begin(), module_list->end(), [&](module_info &info) {
             info.z32 = convert_to_memfd(info.z32);
 #if defined(__LP64__)
             info.z64 = convert_to_memfd(info.z64);
@@ -762,13 +754,13 @@ static void collect_modules(bool open_zygisk) {
 }
 
 void handle_modules() {
-    default_new(modules);
+    default_new(module_list);
     prepare_modules();
     collect_modules(false);
     exec_module_scripts("post-fs-data");
 
     // Recollect modules (module scripts could remove itself)
-    modules->clear();
+    module_list->clear();
     collect_modules(true);
 }
 
@@ -789,24 +781,7 @@ void remove_modules() {
 
 void exec_module_scripts(const char *stage) {
     vector<string_view> module_names;
-    std::transform(modules->begin(), modules->end(), std::back_inserter(module_names),
+    std::transform(module_list->begin(), module_list->end(), std::back_inserter(module_names),
         [](const module_info &info) -> string_view { return info.name; });
     exec_module_scripts(stage, module_names);
 }
-
-vector<int> zygisk_module_fds(bool is_64_bit) {
-    vector<int> fds;
-    // All fds passed to send_fds have to be valid file descriptors.
-    // To workaround this issue, send over STDOUT_FILENO as an indicator of an
-    // invalid fd as it will always be /dev/null in magiskd
-    if (is_64_bit) {
-#if defined(__LP64__)
-        std::transform(modules->begin(), modules->end(), std::back_inserter(fds),
-            [](const module_info &info) { return info.z64 < 0 ? STDOUT_FILENO : info.z64; });
-#endif
-    } else {
-        std::transform(modules->begin(), modules->end(), std::back_inserter(fds),
-            [](const module_info &info) { return info.z32 < 0 ? STDOUT_FILENO : info.z32; });
-    }
-    return fds;
-}

native/jni/include/daemon.hpp

@@ -42,9 +42,18 @@ enum : int {
     DAEMON_LAST
 };
 
+struct module_info {
+    std::string name;
+    int z32 = -1;
+#if defined(__LP64__)
+    int z64 = -1;
+#endif
+};
+
 extern bool zygisk_enabled;
 extern int app_process_32;
 extern int app_process_64;
+extern std::vector<module_info> *module_list;
 
 int connect_daemon(bool create = false);
 
@@ -69,7 +78,6 @@ void boot_complete(int client);
 void denylist_handler(int client, const sock_cred *cred);
 void su_daemon_handler(int client, const sock_cred *cred);
 void zygisk_handler(int client, const sock_cred *cred);
-std::vector<int> zygisk_module_fds(bool is_64_bit);
 
 // Denylist
 void initialize_denylist();

native/jni/zygisk/api.hpp

@@ -9,7 +9,7 @@
 
 #include <jni.h>
 
-#define ZYGISK_API_VERSION 1
+#define ZYGISK_API_VERSION 2
 
 /*
 
@@ -173,6 +173,16 @@ struct Api {
     // module's companion request handler. Returns -1 if the connection attempt failed.
     int connectCompanion();
 
+    // Get the file descriptor of the root folder of the current module.
+    //
+    // This API only works in the pre[XXX]Specialize functions.
+    // Accessing the directory returned is only possible in the pre[XXX]Specialize functions
+    // or in the root companion process (assuming that you sent the fd over the socket).
+    // Both restrictions are due to SELinux and UID.
+    //
+    // Returns -1 if errors occurred.
+    int getModuleDir();
+
     // Set various options for your module.
     // Please note that this function accepts one single option at a time.
     // Check zygisk::Option for the full list of options available.
@@ -261,6 +271,7 @@ struct api_table {
     // Zygisk functions
     int  (*connectCompanion)(void * /* _this */);
     void (*setOption)(void * /* _this */, Option);
+    int  (*getModuleDir)(void * /* _this */);
 };
 
 template <class T>
@@ -278,6 +289,9 @@ void entry_impl(api_table *table, JNIEnv *env) {
 inline int Api::connectCompanion() {
     return impl->connectCompanion ? impl->connectCompanion(impl->_this) : -1;
 }
+inline int Api::getModuleDir() {
+    return impl->getModuleDir ? impl->getModuleDir(impl->_this) : -1;
+}
 inline void Api::setOption(Option opt) {
     if (impl->setOption) impl->setOption(impl->_this, opt);
 }

native/jni/zygisk/entry.cpp

@@ -185,6 +185,23 @@ std::vector<int> remote_get_info(int uid, const char *process, AppInfo *info) {
 
 // The following code runs in magiskd
 
+static vector<int> get_module_fds(bool is_64_bit) {
+    vector<int> fds;
+    // All fds passed to send_fds have to be valid file descriptors.
+    // To workaround this issue, send over STDOUT_FILENO as an indicator of an
+    // invalid fd as it will always be /dev/null in magiskd
+    if (is_64_bit) {
+#if defined(__LP64__)
+        std::transform(module_list->begin(), module_list->end(), std::back_inserter(fds),
+            [](const module_info &info) { return info.z64 < 0 ? STDOUT_FILENO : info.z64; });
+#endif
+    } else {
+        std::transform(module_list->begin(), module_list->end(), std::back_inserter(fds),
+            [](const module_info &info) { return info.z32 < 0 ? STDOUT_FILENO : info.z32; });
+    }
+    return fds;
+}
+
 static bool get_exe(int pid, char *buf, size_t sz) {
     snprintf(buf, sz, "/proc/%d/exe", pid);
     return xreadlink(buf, buf, sz) > 0;
@@ -221,7 +238,7 @@ static void connect_companion(int client, bool is_64_bit) {
             exit(-1);
         }
         close(fds[1]);
-        vector<int> module_fds = zygisk_module_fds(is_64_bit);
+        vector<int> module_fds = get_module_fds(is_64_bit);
         send_fds(zygiskd_socket, module_fds.data(), module_fds.size());
         // Wait for ack
         if (read_int(zygiskd_socket) != 0) {
@@ -342,7 +359,7 @@ static void get_process_info(int client, const sock_cred *cred) {
     if (!info.on_denylist) {
         char buf[256];
         get_exe(cred->pid, buf, sizeof(buf));
-        vector<int> fds = zygisk_module_fds(str_ends(buf, "64"));
+        vector<int> fds = get_module_fds(str_ends(buf, "64"));
         send_fds(client, fds.data(), fds.size());
     }
 }
@@ -357,6 +374,15 @@ static void send_log_pipe(int fd) {
     }
 }
 
+static void get_moddir(int client) {
+    int id = read_int(client);
+    char buf[4096];
+    snprintf(buf, sizeof(buf), MODULEROOT "/%s", module_list->operator[](id).name.data());
+    int dfd = xopen(buf, O_RDONLY | O_CLOEXEC);
+    send_fd(client, dfd);
+    close(dfd);
+}
+
 void zygisk_handler(int client, const sock_cred *cred) {
     int code = read_int(client);
     char buf[256];
@@ -377,6 +403,9 @@ void zygisk_handler(int client, const sock_cred *cred) {
         get_exe(cred->pid, buf, sizeof(buf));
         connect_companion(client, str_ends(buf, "64"));
         break;
+    case ZYGISK_GET_MODDIR:
+        get_moddir(client);
+        break;
     }
     close(client);
 }

native/jni/zygisk/hook.cpp

@@ -294,16 +294,26 @@ bool ZygiskModule::RegisterModule(ApiTable *table, long *module) {
     table->module->ver = module;
 
     // Fill in API accordingly with module API version
+    switch (ver) {
+    case 2:
+        table->v2.getModuleDir = [](ZygiskModule *m) { return m->getModuleDir(); };
+        [[fallthrough]];
+    case 1:
         table->v1.hookJniNativeMethods = &hookJniNativeMethods;
-    table->v1.pltHookRegister = [](const char *path, const char *symbol, void *n, void **o) {
-        xhook_register(path, symbol, n, o);
+        table->v1.pltHookRegister = [](const char *p, const char *s, void *n, void **o) {
+            xhook_register(p, s, n, o);
         };
-    table->v1.pltHookExclude = [](const char *path, const char *symbol) {
-        xhook_ignore(path, symbol);
+        table->v1.pltHookExclude = [](const char *p, const char *s) {
+            xhook_ignore(p, s);
         };
         table->v1.pltHookCommit = []{ bool r = xhook_refresh(0) == 0; xhook_clear(); return r; };
         table->v1.connectCompanion = [](ZygiskModule *m) { return m->connectCompanion(); };
         table->v1.setOption = [](ZygiskModule *m, auto opt) { m->setOption(opt); };
+        break;
+    default:
+        // Unknown version number
+        return false;
+    }
 
     return true;
 }
@@ -318,6 +328,18 @@ int ZygiskModule::connectCompanion() const {
     return -1;
 }
 
+int ZygiskModule::getModuleDir() const {
+    if (int fd = connect_daemon(); fd >= 0) {
+        write_int(fd, ZYGISK_REQUEST);
+        write_int(fd, ZYGISK_GET_MODDIR);
+        write_int(fd, id);
+        int dfd = recv_fd(fd);
+        close(fd);
+        return dfd;
+    }
+    return -1;
+}
+
 void ZygiskModule::setOption(zygisk::Option opt) {
     if (g_ctx == nullptr)
         return;

native/jni/zygisk/module.hpp

@@ -81,6 +81,9 @@ struct ApiTable {
         int (*connectCompanion)(ZygiskModule *);
         void (*setOption)(ZygiskModule *, zygisk::Option);
     } v1;
+    struct {
+        int (*getModuleDir)(ZygiskModule *);
+    } v2;
 
     ApiTable(ZygiskModule *m);
 };
@@ -100,6 +103,7 @@ struct ZygiskModule {
     }
 
     int connectCompanion() const;
+    int getModuleDir() const;
     void setOption(zygisk::Option opt);
     void doUnload() const { if (unload) dlclose(handle); }
 

native/jni/zygisk/zygisk.hpp

@@ -12,6 +12,7 @@ enum : int {
     ZYGISK_GET_INFO,
     ZYGISK_GET_LOG_PIPE,
     ZYGISK_CONNECT_COMPANION,
+    ZYGISK_GET_MODDIR,
 };
 
 #if defined(__LP64__)