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Force off-device package installation with FUSE

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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
This commit is contained in:
Tianjie Xu
2019-08-06 12:32:05 -07:00
committed by Bryan Ferris
parent 4139a30ec5
commit cd8faf7eee
6 changed files with 87 additions and 1 deletions
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tests/unit/install_test.cpp
+28
View File
@@ -35,6 +35,7 @@
#include "install/wipe_device.h"
#include "otautil/paths.h"
#include "private/setup_commands.h"
#include "recovery_utils/roots.h"
static void BuildZipArchive(const std::map<std::string, std::string>& 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<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));
}