Force package installation with FUSE unless the package stores on device
The non-A/B package installation is subject to TOC/TOU flaw if the
attacker can switch the package in the middle of installation. And the
most pratical case is to store the package on an external device, e.g. a
sdcard, and swap the device in the middle.
To prevent that, we can adopt the same protection as used in sideloading
a package with FUSE. Specifically, when we install the package with FUSE,
we read the entire package to cryptographically verify its signature.
The hash for each transfer block is recorded in the memory (TOC), and
the subsequent reads (TOU) will be rejected upon dectecting a mismatch.
This CL forces the package installation with FUSE when the package stays
on a removable media.
Bug: 136498130
Test: Run bin/recovery --update_package with various paths;
and packages are installed from FUSE as expected
Test: recovery_component_test - all passing
Merged-In: Ibc9b095036a2fa624e8edf6c347ed4f12aef072f
Change-Id: Ibc9b095036a2fa624e8edf6c347ed4f12aef072f
diff --git a/Android.bp b/Android.bp
index f920782..f367e5e 100644
--- a/Android.bp
+++ b/Android.bp
@@ -69,6 +69,7 @@
],
static_libs: [
+ "libc++fs",
"libinstall",
"librecovery_fastboot",
"libminui",
@@ -94,6 +95,7 @@
],
shared_libs: [
+ "libfusesideload",
"librecovery_ui",
],
}
diff --git a/install/include/install/install.h b/install/include/install/install.h
index c0a8f1f..ed0f6c7 100644
--- a/install/include/install/install.h
+++ b/install/include/install/install.h
@@ -69,3 +69,7 @@
// Mandatory checks: ota-type, pre-device and serial number(if presents)
// AB OTA specific checks: pre-build version, fingerprint, timestamp.
int CheckPackageMetadata(const std::map<std::string, std::string>& metadata, OtaType ota_type);
+
+// Ensures the path to the update package is mounted. Also set the |should_use_fuse| to true if the
+// package stays on a removable media.
+bool SetupPackageMount(const std::string& package_path, bool* should_use_fuse);
diff --git a/install/install.cpp b/install/install.cpp
index e2d4700..9203ef0 100644
--- a/install/install.cpp
+++ b/install/install.cpp
@@ -30,6 +30,7 @@
#include <atomic>
#include <chrono>
#include <condition_variable>
+#include <filesystem>
#include <functional>
#include <limits>
#include <mutex>
@@ -736,3 +737,49 @@
}
return true;
}
+
+bool SetupPackageMount(const std::string& package_path, bool* should_use_fuse) {
+ CHECK(should_use_fuse != nullptr);
+
+ if (package_path.empty()) {
+ return false;
+ }
+
+ *should_use_fuse = true;
+ if (package_path[0] == '@') {
+ auto block_map_path = package_path.substr(1);
+ if (ensure_path_mounted(block_map_path) != 0) {
+ LOG(ERROR) << "Failed to mount " << block_map_path;
+ return false;
+ }
+ // uncrypt only produces block map only if the package stays on /data.
+ *should_use_fuse = false;
+ return true;
+ }
+
+ // Package is not a block map file.
+ if (ensure_path_mounted(package_path) != 0) {
+ LOG(ERROR) << "Failed to mount " << package_path;
+ return false;
+ }
+
+ // Reject the package if the input path doesn't equal the canonicalized path.
+ // e.g. /cache/../sdcard/update_package.
+ std::error_code ec;
+ auto canonical_path = std::filesystem::canonical(package_path, ec);
+ if (ec) {
+ LOG(ERROR) << "Failed to get canonical of " << package_path << ", " << ec.message();
+ return false;
+ }
+ if (canonical_path.string() != package_path) {
+ LOG(ERROR) << "Installation aborts. The canonical path " << canonical_path.string()
+ << " doesn't equal the original path " << package_path;
+ return false;
+ }
+
+ constexpr const char* CACHE_ROOT = "/cache";
+ if (android::base::StartsWith(package_path, CACHE_ROOT)) {
+ *should_use_fuse = false;
+ }
+ return true;
+}
diff --git a/recovery.cpp b/recovery.cpp
index 5fc673e..e51687a 100644
--- a/recovery.cpp
+++ b/recovery.cpp
@@ -50,6 +50,7 @@
#include "common.h"
#include "fsck_unshare_blocks.h"
+#include "fuse_sideload.h"
#include "install/adb_install.h"
#include "install/fuse_sdcard_install.h"
#include "install/install.h"
@@ -881,7 +882,29 @@
set_retry_bootloader_message(retry_count + 1, args);
}
- status = install_package(update_package, should_wipe_cache, true, retry_count, ui);
+ bool should_use_fuse = false;
+ if (!SetupPackageMount(update_package, &should_use_fuse)) {
+ LOG(INFO) << "Failed to set up the package access, skipping installation";
+ status = INSTALL_ERROR;
+ } else if (should_use_fuse) {
+ LOG(INFO) << "Installing package " << update_package << " with fuse";
+ auto file_data_reader = std::make_unique<FuseFileDataProvider>(update_package, 65536);
+ status = run_fuse_sideload(std::move(file_data_reader));
+ } else if (auto memory_package = Package::CreateMemoryPackage(
+ update_package,
+ std::bind(&RecoveryUI::SetProgress, ui, std::placeholders::_1));
+ memory_package != nullptr) {
+ status = install_package(update_package, should_wipe_cache, true, retry_count, ui);
+ } else {
+ // We may fail to memory map the package on 32 bit builds for packages with 2GiB+ size.
+ // In such cases, we will try to install the package with fuse. This is not the default
+ // installation method because it introduces a layer of indirection from the kernel space.
+ LOG(WARNING) << "Failed to memory map package " << update_package
+ << "; falling back to install with fuse";
+ auto file_data_reader = std::make_unique<FuseFileDataProvider>(update_package, 65536);
+ status = run_fuse_sideload(std::move(file_data_reader));
+ }
+
if (status != INSTALL_SUCCESS) {
ui->Print("Installation aborted.\n");
diff --git a/tests/Android.bp b/tests/Android.bp
index 09ef716..a0d82d5 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -99,6 +99,7 @@
"liblp",
"libvndksupport",
"libtinyxml2",
+ "libc++fs",
]
cc_test {
diff --git a/tests/component/install_test.cpp b/tests/component/install_test.cpp
index 3851329..c1f0ca8 100644
--- a/tests/component/install_test.cpp
+++ b/tests/component/install_test.cpp
@@ -34,6 +34,7 @@
#include "install/install.h"
#include "otautil/paths.h"
+#include "otautil/roots.h"
#include "private/setup_commands.h"
static void BuildZipArchive(const std::map<std::string, std::string>& file_map, int fd,
@@ -595,3 +596,30 @@
"\n");
test_check_package_metadata(metadata, OtaType::AB, 0);
}
+
+TEST(InstallTest, SetupPackageMount_package_path) {
+ load_volume_table();
+ bool install_with_fuse;
+
+ // Setup should fail if the input path doesn't exist.
+ ASSERT_FALSE(SetupPackageMount("/does_not_exist", &install_with_fuse));
+
+ // Package should be installed with fuse if it's not in /cache.
+ TemporaryDir temp_dir;
+ TemporaryFile update_package(temp_dir.path);
+ ASSERT_TRUE(SetupPackageMount(update_package.path, &install_with_fuse));
+ ASSERT_TRUE(install_with_fuse);
+
+ // Setup should fail if the input path isn't canonicalized.
+ std::string uncanonical_package_path = android::base::Join(
+ std::vector<std::string>{
+ temp_dir.path,
+ "..",
+ android::base::Basename(temp_dir.path),
+ android::base::Basename(update_package.path),
+ },
+ '/');
+
+ ASSERT_EQ(0, access(uncanonical_package_path.c_str(), R_OK));
+ ASSERT_FALSE(SetupPackageMount(uncanonical_package_path, &install_with_fuse));
+}