ncm: implement firmware downgrading (#958)

* ncm: implement firmware downgrading

* ncm: make storage list const

libraries/libstratosphere/include/stratosphere/ncm.hpp

@@ -36,6 +36,7 @@
 #include <stratosphere/ncm/ncm_memory_report.hpp>
 #include <stratosphere/ncm/ncm_package_install_task_base.hpp>
 #include <stratosphere/ncm/ncm_package_install_task.hpp>
+#include <stratosphere/ncm/ncm_package_system_downgrade_task.hpp>
 #include <stratosphere/ncm/ncm_package_system_update_task.hpp>
 #include <stratosphere/ncm/ncm_submission_package_install_task.hpp>
 #include <stratosphere/ncm/ncm_storage_utils.hpp>

libraries/libstratosphere/include/stratosphere/ncm/ncm_install_task_base.hpp

@@ -139,10 +139,11 @@ namespace ams::ncm {
             Result CountInstallContentMetaData(s32 *out_count);
             Result GetInstallContentMetaData(InstallContentMeta *out_content_meta, s32 index);
             Result DeleteInstallContentMetaData(const ContentMetaKey *keys, s32 num_keys);
+            virtual Result GetInstallContentMetaInfo(InstallContentMetaInfo *out_info, const ContentMetaKey &key) = 0;
 
             virtual Result PrepareDependency();
             Result PrepareSystemUpdateDependency();
-            Result PrepareContentMetaIfLatest(const ContentMetaKey &key);
+            virtual Result PrepareContentMetaIfLatest(const ContentMetaKey &key); /* NOTE: This is not virtual in Nintendo's code. We do so to facilitate downgrades. */
             u32 GetConfig() const { return this->config; }
             Result WriteContentMetaToPlaceHolder(InstallContentInfo *out_install_content_info, ContentStorage *storage, const InstallContentMetaInfo &meta_info, std::optional<bool> is_temporary);
 
@@ -163,7 +164,6 @@ namespace ams::ncm {
             Result VerifyAllNotCommitted(const StorageContentMetaKey *keys, s32 num_keys);
 
             virtual Result PrepareInstallContentMetaData() = 0;
-            virtual Result GetInstallContentMetaInfo(InstallContentMetaInfo *out_info, const ContentMetaKey &key) = 0;
             virtual Result GetLatestVersion(std::optional<u32> *out_version, u64 id) { return ncm::ResultContentMetaNotFound(); }
 
             virtual Result OnExecuteComplete() { return ResultSuccess(); }

libraries/libstratosphere/include/stratosphere/ncm/ncm_package_system_downgrade_task.hpp

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2019-2020 Adubbz, Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+#include <stratosphere/ncm/ncm_package_system_update_task.hpp>
+
+namespace ams::ncm {
+
+    class PackageSystemDowngradeTask : public PackageSystemUpdateTask {
+        public:
+            Result Commit();
+        protected:
+            virtual Result PrepareContentMetaIfLatest(const ContentMetaKey &key) override;
+        private:
+            Result PreCommit();
+    };
+
+}

libraries/libstratosphere/include/stratosphere/ncm/ncm_package_system_update_task.hpp

@@ -34,9 +34,10 @@ namespace ams::ncm {
             std::optional<ContentMetaKey> GetSystemUpdateMetaKey();
         protected:
             virtual Result PrepareInstallContentMetaData() override;
+            virtual Result GetInstallContentMetaInfo(InstallContentMetaInfo *out, const ContentMetaKey &key) override;
+            InstallTaskDataBase &GetInstallData() { return this->data; } /* Atmosphere extension. */
         private:
             virtual Result PrepareDependency() override;
-            virtual Result GetInstallContentMetaInfo(InstallContentMetaInfo *out, const ContentMetaKey &key) override;
 
             Result GetContentInfoOfContentMeta(ContentInfo *out, const ContentMetaKey &key);
     };

libraries/libstratosphere/source/ncm/ncm_package_system_downgrade_task.cpp

@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2019-2020 Adubbz, Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <stratosphere.hpp>
+
+namespace ams::ncm {
+
+    Result PackageSystemDowngradeTask::PreCommit() {
+        constexpr size_t MaxContentMetas = 0x40;
+
+        auto &data = this->GetInstallData();
+
+        /* Count the number of content meta entries. */
+        s32 count;
+        R_TRY(data.Count(std::addressof(count)));
+
+        /* Iterate over content meta. */
+        for (s32 i = 0; i < count; i++) {
+            /* Obtain the content meta. */
+            InstallContentMeta content_meta;
+            R_TRY(data.Get(std::addressof(content_meta), i));
+
+            /* Create a reader. */
+            const auto reader = content_meta.GetReader();
+            const auto key = reader.GetKey();
+
+            /* Obtain a list of suitable storage ids. */
+            const auto storage_list = GetStorageList(this->GetInstallStorage());
+
+            /* Iterate over storage ids. */
+            for (s32 i = 0; i < storage_list.Count(); i++) {
+                /* Open the content meta database. */
+                ContentMetaDatabase meta_db;
+                if (R_FAILED(OpenContentMetaDatabase(std::addressof(meta_db), storage_list[i]))) {
+                    continue;
+                }
+
+                /* List keys matching the type and id of the install content meta key. */
+                ncm::ContentMetaKey keys[MaxContentMetas];
+                const auto count = meta_db.ListContentMeta(keys, MaxContentMetas, key.type, { key.id });
+
+                /* Remove matching keys. */
+                for (auto i = 0; i < count.total; i++) {
+                    meta_db.Remove(keys[i]);
+                }
+            }
+        }
+
+        return ResultSuccess();
+    }
+
+    Result PackageSystemDowngradeTask::Commit() {
+        R_TRY(this->PreCommit());
+        return InstallTaskBase::Commit();
+    }
+
+    Result PackageSystemDowngradeTask::PrepareContentMetaIfLatest(const ContentMetaKey &key) {
+        /* Get and prepare install content meta info. We aren't concerned if our key is older. */
+        InstallContentMetaInfo install_content_meta_info;
+        R_TRY(this->GetInstallContentMetaInfo(std::addressof(install_content_meta_info), key));
+        return this->PrepareContentMeta(install_content_meta_info, key, std::nullopt);
+    }
+
+}