add: injection hardening

This commit adds injection hardening mechanism to ReLSPosed, where it will not proceed with the processing/binder-based communication.

Author: ThePedroo

magisk-loader/src/main/jni/api/zygisk_main.cpp

@@ -27,8 +27,10 @@
 #include "zygisk.hpp"
 
 namespace lspd {
+
 int allow_unload = 0;
 int *allowUnload = &allow_unload;
+bool should_ignore = false;
 
 class ZygiskModule : public zygisk::ModuleBase {
     JNIEnv *env_;
@@ -42,12 +44,60 @@ class ZygiskModule : public zygisk::ModuleBase {
     }
 
     void preAppSpecialize(zygisk::AppSpecializeArgs *args) override {
+        int cfd = api_->connectCompanion();
+        if (cfd < 0) {
+            LOGE("Failed to connect to companion: %s", strerror(errno));
+
+            return;
+        }
+
+        uint8_t injection_hardening_disabled = 0;
+        if (read(cfd, &injection_hardening_disabled, sizeof(injection_hardening_disabled)) < 0) {
+            LOGE("Failed to read from companion socket: %s", strerror(errno));
+        }
+
+        close(cfd);
+
+        if (!injection_hardening_disabled) {
+            uint32_t flags = api_->getFlags();
+            if ((flags & zygisk::PROCESS_ON_DENYLIST) == 0) goto bypass_denylist;
+
+            const char *name = env_->GetStringUTFChars(args->nice_name, nullptr);
+            if (strcmp(name, "com.android.shell") == 0) {
+                LOGD("Process is com.android.shell, bypassing denylist check");
+
+                env_->ReleaseStringUTFChars(args->nice_name, name);
+
+                goto bypass_denylist;
+            }
+
+            LOGE("Process %s is on denylist, cannot specialize", name);
+
+            env_->ReleaseStringUTFChars(args->nice_name, name);
+
+            should_ignore = true;
+
+            return;
+        } else {
+            LOGD("Injection hardening is disabled");
+        }
+
+        bypass_denylist:
+
         MagiskLoader::GetInstance()->OnNativeForkAndSpecializePre(
             env_, args->uid, args->gids, args->nice_name,
             args->is_child_zygote ? *args->is_child_zygote : false, args->app_data_dir);
     }
 
     void postAppSpecialize(const zygisk::AppSpecializeArgs *args) override {
+        if (should_ignore) {
+            LOGD("Ignoring postAppSpecialize due to injection hardening being enabled");
+
+            api_->setOption(zygisk::DLCLOSE_MODULE_LIBRARY);
+
+            return;
+        }
+
         MagiskLoader::GetInstance()->OnNativeForkAndSpecializePost(env_, args->nice_name,
                                                                    args->app_data_dir);
         if (*allowUnload) api_->setOption(zygisk::DLCLOSE_MODULE_LIBRARY);
@@ -72,4 +122,22 @@ class ZygiskModule : public zygisk::ModuleBase {
 };
 }  // namespace lspd
 
+void relsposed_companion(int lib_fd) {
+    /* INFO: The only current task we do in companion now is to check if
+               /data/adb/disable_injection_hardening file exists. */
+    uint8_t file_exists = 0;
+    if (access("/data/adb/disable_injection_hardening", F_OK) == 0) {
+        LOGD("Found /data/adb/disable_injection_hardening, disabling injection hardening");
+
+        file_exists = 1;
+    }
+
+    if (write(lib_fd, &file_exists, sizeof(file_exists)) < 0) {
+        LOGE("Failed to write to companion socket: %s", strerror(errno));
+    }
+
+    close(lib_fd);
+}
+
 REGISTER_ZYGISK_MODULE(lspd::ZygiskModule);
+REGISTER_ZYGISK_COMPANION(relsposed_companion);