From cd8faf7eeead6fd6ee5912ddd26dab5ab6c7dda7 Mon Sep 17 00:00:00 2001 From: Tianjie Xu Date: Tue, 6 Aug 2019 12:32:05 -0700 Subject: Force off-device package installation with FUSE 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_unit_test - no new failures Change-Id: Ia5afd19854c3737110339fd59491b96708926ae5 Merged-In: I35119c2334895aa0ef4ed71b3ddd08f280c0c031 --- Android.bp | 2 ++ install/include/install/install.h | 4 ++++ install/install.cpp | 47 +++++++++++++++++++++++++++++++++++++++ recovery.cpp | 6 ++++- tests/Android.bp | 1 + tests/unit/install_test.cpp | 28 +++++++++++++++++++++++ 6 files changed, 87 insertions(+), 1 deletion(-) diff --git a/Android.bp b/Android.bp index 4032bcc19..e7e1938b8 100644 --- a/Android.bp +++ b/Android.bp @@ -72,6 +72,7 @@ cc_defaults { ], static_libs: [ + "libc++fs", "libinstall", "librecovery_fastboot", "libminui", @@ -94,6 +95,7 @@ cc_library_static { ], shared_libs: [ + "libfusesideload", "librecovery_ui", ], } diff --git a/install/include/install/install.h b/install/include/install/install.h index 87d43ab09..bef23e9ca 100644 --- a/install/include/install/install.h +++ b/install/include/install/install.h @@ -63,3 +63,7 @@ bool ReadMetadataFromPackage(ZipArchiveHandle zip, std::map& 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 4bb0903cc..1c9bf2fd2 100644 --- a/install/install.cpp +++ b/install/install.cpp @@ -30,6 +30,7 @@ #include #include #include +#include #include #include #include @@ -641,3 +642,49 @@ bool verify_package(Package* package, RecoveryUI* ui) { } 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 9ea616e13..526e1a556 100644 --- a/recovery.cpp +++ b/recovery.cpp @@ -752,7 +752,11 @@ Device::BuiltinAction start_recovery(Device* device, const std::vector& file_map, int fd, int compression_type) { @@ -513,3 +514,30 @@ TEST(InstallTest, CheckPackageMetadata_ab_post_timestamp) { "\n"); TestCheckPackageMetadata(metadata, OtaType::AB, true); } + +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{ + 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)); +} -- cgit v1.2.3