Fallback to /data/apex/sessions if /metadata partition is absent

There might be devices that support updatable apex, but don't have
/metadata partition. For them we need to fallback to storing sessions on
/data/apex/sessions.

This change implements this logic by introducing GetSessionsDir static
method which will pick first existing directory between
/metadata/apex/sessions and /data/apex/sessions. The evaluation will
happen only once, all other calls to GetSessionsDir will return the
cached value.

Additionally, the logic for migrating sessions from /data/apex/sessions
to /metadata/apex/sessions is changed a little bit. Now apexd will
iterate over entires in /data/apex/sessions, and then recursively
copy their content to the corresponding directory under
/metadata/apex/sessions, and then delete the entry under
/data/apex/sessions. This way a directory created by init
(/data/apex/sessions) is kept, which makes it easier to write unit tests
for apexd.

Logic is implemented as function inside apexd_utils.h for the ease of
unit testing.

Test: atest ApexTestCases
Test: atest apexd_host_tests
Test: atest CtsStagedInstallHostTestCases
Bug: 169932155
Bug: 176314162
Merged-In: Ifea8840ee5f1e56428d80bbb3b4e5e078176a578
Change-Id: Ia5e31e53edb411a023c8b090b7eb53ae977adc3e
(cherry picked from commit 7ffc3f6bd74b0b5567e6425090e9d13b6f5d4172)
(cherry picked from commit 69e06a1ddf509e4fc0734e044655d2b876b2bf45)

1 files changed, 183 insertions, 0 deletions

diff --git a/apexd/apexd_utils_test.cpp b/apexd/apexd_utils_test.cpp
new file mode 100644
index 0000000..06b9c46
--- /dev/null
+++ b/apexd/apexd_utils_test.cpp
@@ -0,0 +1,183 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <filesystem>
+#include <string>
+
+#include <errno.h>
+
+#include <android-base/file.h>
+#include <android-base/result.h>
+#include <android-base/stringprintf.h>
+#include <gtest/gtest.h>
+
+#include "apexd_test_utils.h"
+#include "apexd_utils.h"
+
+namespace android {
+namespace apex {
+namespace {
+
+using android::apex::testing::IsOk;
+using android::base::Basename;
+using android::base::StringPrintf;
+using ::testing::UnorderedElementsAre;
+using ::testing::UnorderedElementsAreArray;
+
+// TODO(b/170327382): add unit tests for apexd_utils.h
+
+TEST(ApexdUtilTest, FindFirstExistingDirectoryBothExist) {
+  TemporaryDir first_dir;
+  TemporaryDir second_dir;
+  auto result = FindFirstExistingDirectory(first_dir.path, second_dir.path);
+  ASSERT_TRUE(IsOk(result));
+  ASSERT_EQ(*result, first_dir.path);
+}
+
+TEST(ApexdUtilTest, FindFirstExistingDirectoryOnlyFirstExist) {
+  TemporaryDir first_dir;
+  auto second_dir = "/data/local/tmp/does/not/exist";
+  auto result = FindFirstExistingDirectory(first_dir.path, second_dir);
+  ASSERT_TRUE(IsOk(result));
+  ASSERT_EQ(*result, first_dir.path);
+}
+
+TEST(ApexdUtilTest, FindFirstExistingDirectoryOnlySecondExist) {
+  auto first_dir = "/data/local/tmp/does/not/exist";
+  TemporaryDir second_dir;
+  auto result = FindFirstExistingDirectory(first_dir, second_dir.path);
+  ASSERT_TRUE(IsOk(result));
+  ASSERT_EQ(*result, second_dir.path);
+}
+
+TEST(ApexdUtilTest, FindFirstExistingDirectoryNoneExist) {
+  auto first_dir = "/data/local/tmp/does/not/exist";
+  auto second_dir = "/data/local/tmp/also/does/not/exist";
+  auto result = FindFirstExistingDirectory(first_dir, second_dir);
+  ASSERT_FALSE(IsOk(result));
+}
+
+TEST(ApexdUtilTest, FindFirstExistingDirectoryFirstFileSecondDir) {
+  TemporaryFile first_file;
+  TemporaryDir second_dir;
+  auto result = FindFirstExistingDirectory(first_file.path, second_dir.path);
+  ASSERT_TRUE(IsOk(result));
+  ASSERT_EQ(*result, second_dir.path);
+}
+
+TEST(ApexdUtilTest, FindFirstExistingDirectoryFirstDirSecondFile) {
+  TemporaryDir first_dir;
+  TemporaryFile second_file;
+  auto result = FindFirstExistingDirectory(first_dir.path, second_file.path);
+  ASSERT_TRUE(IsOk(result));
+  ASSERT_EQ(*result, first_dir.path);
+}
+
+TEST(ApexdUtilTest, FindFirstExistingDirectoryBothFiles) {
+  TemporaryFile first_file;
+  TemporaryFile second_file;
+  auto result = FindFirstExistingDirectory(first_file.path, second_file.path);
+  ASSERT_FALSE(IsOk(result));
+}
+
+TEST(ApexdUtilTest, FindFirstExistingDirectoryFirstFileSecondDoesNotExist) {
+  TemporaryFile first_file;
+  auto second_dir = "/data/local/tmp/does/not/exist";
+  auto result = FindFirstExistingDirectory(first_file.path, second_dir);
+  ASSERT_FALSE(IsOk(result));
+}
+
+TEST(ApexdUtilTest, FindFirstExistingDirectoryFirsDoesNotExistSecondFile) {
+  auto first_dir = "/data/local/tmp/does/not/exist";
+  TemporaryFile second_file;
+  auto result = FindFirstExistingDirectory(first_dir, second_file.path);
+  ASSERT_FALSE(IsOk(result));
+}
+
+TEST(ApexdUtilTest, MoveDir) {
+  namespace fs = std::filesystem;
+
+  TemporaryDir from;
+  TemporaryDir to;
+
+  TemporaryFile from_1(from.path);
+  auto from_subdir = StringPrintf("%s/subdir", from.path);
+  if (mkdir(from_subdir.c_str(), 07000) != 0) {
+    FAIL() << "Failed to mkdir " << from_subdir << " : " << strerror(errno);
+  }
+  TemporaryFile from_2(from_subdir);
+
+  auto result = MoveDir(from.path, to.path);
+  ASSERT_TRUE(IsOk(result));
+  ASSERT_TRUE(fs::is_empty(from.path));
+
+  std::vector<std::string> content;
+  for (const auto& it : fs::recursive_directory_iterator(to.path)) {
+    content.push_back(it.path());
+  }
+
+  static const std::vector<std::string> expected = {
+      StringPrintf("%s/%s", to.path, Basename(from_1.path).c_str()),
+      StringPrintf("%s/subdir", to.path),
+      StringPrintf("%s/subdir/%s", to.path, Basename(from_2.path).c_str()),
+  };
+  ASSERT_THAT(content, UnorderedElementsAreArray(expected));
+}
+
+TEST(ApexdUtilTest, MoveDirFromIsNotDirectory) {
+  TemporaryFile from;
+  TemporaryDir to;
+  ASSERT_FALSE(IsOk(MoveDir(from.path, to.path)));
+}
+
+TEST(ApexdUtilTest, MoveDirToIsNotDirectory) {
+  TemporaryDir from;
+  TemporaryFile to;
+  TemporaryFile from_1(from.path);
+  ASSERT_FALSE(IsOk(MoveDir(from.path, to.path)));
+}
+
+TEST(ApexdUtilTest, MoveDirFromDoesNotExist) {
+  TemporaryDir to;
+  ASSERT_FALSE(IsOk(MoveDir("/data/local/tmp/does/not/exist", to.path)));
+}
+
+TEST(ApexdUtilTest, MoveDirToDoesNotExist) {
+  namespace fs = std::filesystem;
+
+  TemporaryDir from;
+  TemporaryFile from_1(from.path);
+  auto from_subdir = StringPrintf("%s/subdir", from.path);
+  if (mkdir(from_subdir.c_str(), 07000) != 0) {
+    FAIL() << "Failed to mkdir " << from_subdir << " : " << strerror(errno);
+  }
+  TemporaryFile from_2(from_subdir);
+
+  ASSERT_FALSE(IsOk(MoveDir(from.path, "/data/local/tmp/does/not/exist")));
+
+  // Check that |from| directory is not empty.
+  std::vector<std::string> content;
+  for (const auto& it : fs::recursive_directory_iterator(from.path)) {
+    content.push_back(it.path());
+  }
+
+  ASSERT_THAT(content,
+              UnorderedElementsAre(from_1.path, from_subdir, from_2.path));
+}
+
+}  // namespace
+}  // namespace apex
+}  // namespace android