libfs_avb: support key rotation for standalone partitions
The FstabEntry.avb_key is renamed to FstabEntry.avb_keys, to
allow specifying multiple avb keys, separated by ':'
(because ',' is already used by fstab parsing).
Bug: 124013032
Test: boot live GSI with multiple allowed AVB keys
Change-Id: Iacd3472a1d5a659dfecf09ea6074d622658f4d0b
diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index 0c904c4..272190e 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -1089,7 +1089,7 @@
// Skips mounting the device.
continue;
}
- } else if (!current_entry.avb_key.empty()) {
+ } else if (!current_entry.avb_keys.empty()) {
if (AvbHandle::SetUpStandaloneAvbHashtree(¤t_entry) == AvbHashtreeResult::kFail) {
LERROR << "Failed to set up AVB on standalone partition: "
<< current_entry.mount_point << ", skipping!";
@@ -1320,7 +1320,7 @@
// Skips mounting the device.
continue;
}
- } else if (!fstab_entry.avb_key.empty()) {
+ } else if (!fstab_entry.avb_keys.empty()) {
if (AvbHandle::SetUpStandaloneAvbHashtree(&fstab_entry) == AvbHashtreeResult::kFail) {
LERROR << "Failed to set up AVB on standalone partition: "
<< fstab_entry.mount_point << ", skipping!";
diff --git a/fs_mgr/fs_mgr_fstab.cpp b/fs_mgr/fs_mgr_fstab.cpp
index 82d9144..5d4a3cc 100644
--- a/fs_mgr/fs_mgr_fstab.cpp
+++ b/fs_mgr/fs_mgr_fstab.cpp
@@ -325,8 +325,8 @@
}
} else if (StartsWith(flag, "zram_backing_dev_path=")) {
entry->zram_backing_dev_path = arg;
- } else if (StartsWith(flag, "avb_key=")) {
- entry->avb_key = arg;
+ } else if (StartsWith(flag, "avb_keys=")) {
+ entry->avb_keys = arg;
} else {
LWARNING << "Warning: unknown flag: " << flag;
}
@@ -759,7 +759,8 @@
.fs_type = "ext4",
.flags = MS_RDONLY,
.fs_options = "barrier=1",
- .avb_key = "/gsi.avbpubkey",
+ // could add more keys separated by ':'.
+ .avb_keys = "/avb/gsi.avbpubkey:",
.logical_partition_name = "system"};
system.fs_mgr_flags.wait = true;
system.fs_mgr_flags.logical = true;
diff --git a/fs_mgr/include_fstab/fstab/fstab.h b/fs_mgr/include_fstab/fstab/fstab.h
index a3d9fdd..e811447 100644
--- a/fs_mgr/include_fstab/fstab/fstab.h
+++ b/fs_mgr/include_fstab/fstab/fstab.h
@@ -55,7 +55,7 @@
std::string zram_loopback_path;
uint64_t zram_loopback_size = 512 * 1024 * 1024; // 512MB by default;
std::string zram_backing_dev_path;
- std::string avb_key;
+ std::string avb_keys;
struct FsMgrFlags {
bool wait : 1;
diff --git a/fs_mgr/libfs_avb/avb_util.cpp b/fs_mgr/libfs_avb/avb_util.cpp
index 80fa5c4..7d89902 100644
--- a/fs_mgr/libfs_avb/avb_util.cpp
+++ b/fs_mgr/libfs_avb/avb_util.cpp
@@ -28,6 +28,7 @@
#include "util.h"
using android::base::Basename;
+using android::base::ReadFileToString;
using android::base::StartsWith;
using android::base::unique_fd;
@@ -311,7 +312,8 @@
return footer;
}
-bool VerifyPublicKeyBlob(const uint8_t* key, size_t length, const std::string& expected_key_blob) {
+bool ValidatePublicKeyBlob(const uint8_t* key, size_t length,
+ const std::string& expected_key_blob) {
if (expected_key_blob.empty()) { // no expectation of the key, return true.
return true;
}
@@ -324,6 +326,21 @@
return false;
}
+bool ValidatePublicKeyBlob(const std::string key_blob_to_validate,
+ const std::vector<std::string>& allowed_key_paths) {
+ std::string allowed_key_blob;
+ if (key_blob_to_validate.empty()) {
+ LWARNING << "Failed to validate an empty key";
+ return false;
+ }
+ for (const auto& path : allowed_key_paths) {
+ if (ReadFileToString(path, &allowed_key_blob)) {
+ if (key_blob_to_validate == allowed_key_blob) return true;
+ }
+ }
+ return false;
+}
+
VBMetaVerifyResult VerifyVBMetaSignature(const VBMetaData& vbmeta,
const std::string& expected_public_key_blob,
std::string* out_public_key_data) {
@@ -347,7 +364,7 @@
<< ": Error verifying vbmeta image: failed to get public key";
return VBMetaVerifyResult::kError;
}
- if (!VerifyPublicKeyBlob(pk_data, pk_len, expected_public_key_blob)) {
+ if (!ValidatePublicKeyBlob(pk_data, pk_len, expected_public_key_blob)) {
LERROR << vbmeta.partition() << ": Error verifying vbmeta image: public key used to"
<< " sign data does not match key in chain descriptor";
return VBMetaVerifyResult::kErrorVerification;
diff --git a/fs_mgr/libfs_avb/avb_util.h b/fs_mgr/libfs_avb/avb_util.h
index 5f413e3..986a69a 100644
--- a/fs_mgr/libfs_avb/avb_util.h
+++ b/fs_mgr/libfs_avb/avb_util.h
@@ -78,7 +78,10 @@
const std::string& expected_public_key_blob,
std::string* out_public_key_data);
-bool VerifyPublicKeyBlob(const uint8_t* key, size_t length, const std::string& expected_key_blob);
+bool ValidatePublicKeyBlob(const uint8_t* key, size_t length, const std::string& expected_key_blob);
+
+bool ValidatePublicKeyBlob(const std::string key_blob_to_validate,
+ const std::vector<std::string>& expected_key_paths);
// Detects if whether a partition contains a rollback image.
bool RollbackDetected(const std::string& partition_name, uint64_t rollback_index);
diff --git a/fs_mgr/libfs_avb/fs_avb.cpp b/fs_mgr/libfs_avb/fs_avb.cpp
index 02902f0..f0767dc 100644
--- a/fs_mgr/libfs_avb/fs_avb.cpp
+++ b/fs_mgr/libfs_avb/fs_avb.cpp
@@ -29,6 +29,7 @@
#include <android-base/file.h>
#include <android-base/parseint.h>
#include <android-base/stringprintf.h>
+#include <android-base/strings.h>
#include <libavb/libavb.h>
#include <libdm/dm.h>
@@ -40,6 +41,7 @@
using android::base::Basename;
using android::base::ParseUint;
using android::base::ReadFileToString;
+using android::base::Split;
using android::base::StringPrintf;
namespace android {
@@ -264,8 +266,8 @@
}
AvbUniquePtr AvbHandle::LoadAndVerifyVbmeta(const FstabEntry& fstab_entry) {
- if (fstab_entry.avb_key.empty()) {
- LERROR << "avb_key=/path/to/key is missing for " << fstab_entry.mount_point;
+ if (fstab_entry.avb_keys.empty()) {
+ LERROR << "avb_keys=/path/to/key(s) is missing for " << fstab_entry.mount_point;
return nullptr;
}
@@ -273,24 +275,14 @@
bool allow_verification_error = IsDeviceUnlocked();
bool rollback_protection = !allow_verification_error;
- std::string expected_key_blob;
- if (!ReadFileToString(fstab_entry.avb_key, &expected_key_blob)) {
- if (!allow_verification_error) {
- LERROR << "Failed to load avb_key: " << fstab_entry.avb_key
- << " for mount point: " << fstab_entry.mount_point;
- return nullptr;
- }
- LWARNING << "Allowing no expected key blob when verification error is permitted";
- expected_key_blob.clear();
- }
-
+ std::string public_key_data;
bool verification_disabled = false;
VBMetaVerifyResult verify_result = VBMetaVerifyResult::kError;
std::unique_ptr<VBMetaData> vbmeta = LoadAndVerifyVbmetaByPath(
fstab_entry.blk_device, "" /* partition_name, no need for a standalone path */,
- expected_key_blob, allow_verification_error, rollback_protection,
- false /* not is_chained_vbmeta */, nullptr /* out_public_key_data */,
- &verification_disabled, &verify_result);
+ "" /* expected_public_key_blob, */, allow_verification_error, rollback_protection,
+ false /* not is_chained_vbmeta */, &public_key_data, &verification_disabled,
+ &verify_result);
if (!vbmeta) {
LERROR << "Failed to load vbmeta: " << fstab_entry.blk_device;
@@ -316,6 +308,15 @@
return nullptr;
}
+ if (!ValidatePublicKeyBlob(public_key_data, Split(fstab_entry.avb_keys, ":"))) {
+ avb_handle->status_ = AvbHandleStatus::kVerificationError;
+ LWARNING << "Found unknown public key used to sign " << fstab_entry.mount_point;
+ if (!allow_verification_error) {
+ LERROR << "Unknown public key is not allowed";
+ return nullptr;
+ }
+ }
+
if (verification_disabled) {
LINFO << "AVB verification disabled on: " << fstab_entry.mount_point;
avb_handle->status_ = AvbHandleStatus::kVerificationDisabled;
diff --git a/fs_mgr/libfs_avb/tests/avb_util_test.cpp b/fs_mgr/libfs_avb/tests/avb_util_test.cpp
index e4213b7..0d342d3 100644
--- a/fs_mgr/libfs_avb/tests/avb_util_test.cpp
+++ b/fs_mgr/libfs_avb/tests/avb_util_test.cpp
@@ -35,9 +35,9 @@
using android::fs_mgr::GetTotalSize;
using android::fs_mgr::LoadAndVerifyVbmetaByPartition;
using android::fs_mgr::LoadAndVerifyVbmetaByPath;
+using android::fs_mgr::ValidatePublicKeyBlob;
using android::fs_mgr::VBMetaData;
using android::fs_mgr::VBMetaVerifyResult;
-using android::fs_mgr::VerifyPublicKeyBlob;
using android::fs_mgr::VerifyVBMetaData;
using android::fs_mgr::VerifyVBMetaSignature;
@@ -415,7 +415,7 @@
EXPECT_EQ(content_padding.size() - padding.size(), vbmeta_padding.size());
}
-TEST_F(AvbUtilTest, VerifyPublicKeyBlob) {
+TEST_F(AvbUtilTest, ValidatePublicKeyBlob) {
// Generates a raw key.bin
const size_t key_size = 2048;
base::FilePath key_path = GenerateImage("key.bin", key_size);
@@ -425,12 +425,12 @@
std::string expected_key_blob;
EXPECT_TRUE(base::ReadFileToString(key_path, &expected_key_blob));
- EXPECT_TRUE(VerifyPublicKeyBlob(key_data, key_size, expected_key_blob));
+ EXPECT_TRUE(ValidatePublicKeyBlob(key_data, key_size, expected_key_blob));
key_data[10] ^= 0x80; // toggles a bit and expects a failure
- EXPECT_FALSE(VerifyPublicKeyBlob(key_data, key_size, expected_key_blob));
+ EXPECT_FALSE(ValidatePublicKeyBlob(key_data, key_size, expected_key_blob));
key_data[10] ^= 0x80; // toggles the bit again, should pass
- EXPECT_TRUE(VerifyPublicKeyBlob(key_data, key_size, expected_key_blob));
+ EXPECT_TRUE(ValidatePublicKeyBlob(key_data, key_size, expected_key_blob));
}
TEST_F(AvbUtilTest, VerifyEmptyPublicKeyBlob) {
@@ -442,7 +442,37 @@
EXPECT_EQ(key_size, base::ReadFile(key_path, (char*)key_data, key_size));
std::string expected_key_blob = ""; // empty means no expectation, thus return true.
- EXPECT_TRUE(VerifyPublicKeyBlob(key_data, key_size, expected_key_blob));
+ EXPECT_TRUE(ValidatePublicKeyBlob(key_data, key_size, expected_key_blob));
+}
+
+TEST_F(AvbUtilTest, ValidatePublicKeyBlob_MultipleAllowedKeys) {
+ base::FilePath rsa2048_public_key =
+ ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa2048.pem"));
+ base::FilePath rsa4096_public_key =
+ ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa4096.pem"));
+ base::FilePath rsa8192_public_key =
+ ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa8192.pem"));
+
+ std::vector<std::string> allowed_key_paths;
+ allowed_key_paths.push_back(rsa2048_public_key.value());
+ allowed_key_paths.push_back(rsa4096_public_key.value());
+
+ std::string expected_key_blob_2048;
+ EXPECT_TRUE(base::ReadFileToString(rsa2048_public_key, &expected_key_blob_2048));
+ std::string expected_key_blob_4096;
+ EXPECT_TRUE(base::ReadFileToString(rsa4096_public_key, &expected_key_blob_4096));
+ std::string expected_key_blob_8192;
+ EXPECT_TRUE(base::ReadFileToString(rsa8192_public_key, &expected_key_blob_8192));
+
+ EXPECT_TRUE(ValidatePublicKeyBlob(expected_key_blob_2048, allowed_key_paths));
+ EXPECT_TRUE(ValidatePublicKeyBlob(expected_key_blob_4096, allowed_key_paths));
+
+ EXPECT_FALSE(ValidatePublicKeyBlob(expected_key_blob_8192, allowed_key_paths));
+ EXPECT_FALSE(ValidatePublicKeyBlob("invalid_content", allowed_key_paths));
+ EXPECT_FALSE(ValidatePublicKeyBlob("", allowed_key_paths));
+
+ allowed_key_paths.push_back(rsa8192_public_key.value());
+ EXPECT_TRUE(ValidatePublicKeyBlob(expected_key_blob_8192, allowed_key_paths));
}
TEST_F(AvbUtilTest, VerifyVBMetaSignature) {
diff --git a/fs_mgr/libfs_avb/tests/fs_avb_device_test.cpp b/fs_mgr/libfs_avb/tests/fs_avb_device_test.cpp
index 4631330..c8605d7 100644
--- a/fs_mgr/libfs_avb/tests/fs_avb_device_test.cpp
+++ b/fs_mgr/libfs_avb/tests/fs_avb_device_test.cpp
@@ -114,8 +114,8 @@
// Use the 2nd fstab entry, which is for physical system_other partition.
FstabEntry* system_other_entry = &fstab[1];
// Assign the default key if it's not specified in the fstab.
- if (system_other_entry->avb_key.empty()) {
- system_other_entry->avb_key = "/system/etc/security/avb/system_other.avbpubkey";
+ if (system_other_entry->avb_keys.empty()) {
+ system_other_entry->avb_keys = "/system/etc/security/avb/system_other.avbpubkey";
}
auto avb_handle = AvbHandle::LoadAndVerifyVbmeta(*system_other_entry);
EXPECT_NE(nullptr, avb_handle) << "Failed to load system_other vbmeta. Try 'adb root'?";
diff --git a/init/first_stage_mount.cpp b/init/first_stage_mount.cpp
index 6e55c11a..17cd470 100644
--- a/init/first_stage_mount.cpp
+++ b/init/first_stage_mount.cpp
@@ -760,7 +760,7 @@
if (!InitAvbHandle()) return false;
hashtree_result =
avb_handle_->SetUpAvbHashtree(fstab_entry, false /* wait_for_verity_dev */);
- } else if (!fstab_entry->avb_key.empty()) {
+ } else if (!fstab_entry->avb_keys.empty()) {
if (!InitAvbHandle()) return false;
// Checks if hashtree should be disabled from the top-level /vbmeta.
if (avb_handle_->status() == AvbHandleStatus::kHashtreeDisabled ||