ext4crypt: support wrappedkey for FBE
Qualcomm devices use a special `wrappedkey` mode for FBE. This is ported
from CAF
https://source.codeaurora.org/quic/la/platform/system/vold/commit/?h=LA.UM.7.8.r4-01000-SDM710.0&id=9229262d893a8592f7bc1b4e8a8dab7aad8df68c,
originally by folks at Mokee for vold
https://mokeedev.review/c/MoKee/android_system_vold/+/34102.
This patch ports the above changes to `ext4crypt`, which we can use in
recovery. Note that since we do not have `fs_mgr` in the recovery, we
cannot read the `wrappedkey` flag from fstab. Instead, similar to
`fbe.contents`, we use a special property `fbe.data.wrappedkey` to
indicate support for wrappedkey mode. Devices that need to use this
should set this property to `true` to activate corresponding code.
Change-Id: I79c2855d577156670b45c10c7c7b1fcd9fece8d9
diff --git a/crypto/ext4crypt/Ext4CryptPie.cpp b/crypto/ext4crypt/Ext4CryptPie.cpp
index d6ea531..d76ca24 100644
--- a/crypto/ext4crypt/Ext4CryptPie.cpp
+++ b/crypto/ext4crypt/Ext4CryptPie.cpp
@@ -16,6 +16,7 @@
#include "Ext4CryptPie.h"
+#include "Keymaster4.h"
#include "KeyStorage4.h"
#include "KeyUtil.h"
#include "Utils.h"
@@ -68,6 +69,8 @@
using android::base::WriteStringToFile;
using android::vold::kEmptyAuthentication;
using android::vold::KeyBuffer;
+using android::vold::Keymaster;
+using android::hardware::keymaster::V4_0::KeyFormat;
// Store main DE raw ref / policy
std::string de_raw_ref;
@@ -204,12 +207,42 @@
return false;
}
+static bool is_wrapped_key_supported_common(const std::string& mount_point) {
+ LOG(DEBUG) << "Determining wrapped-key support for " << mount_point;
+ std::string wrapped_key_supported = android::base::GetProperty("fbe.data.wrappedkey", "false");
+ LOG(DEBUG) << "fbe.data.wrappedkey = " << wrapped_key_supported;
+ if (mount_point == DATA_MNT_POINT && wrapped_key_supported == "true") {
+ LOG(DEBUG) << "Wrapped key supported on " << mount_point;
+ return true;
+ } else {
+ return false;
+ }
+}
+
+bool is_wrapped_key_supported() {
+ return is_wrapped_key_supported_common(DATA_MNT_POINT);
+}
+
+bool is_wrapped_key_supported_external() {
+ return false;
+}
+
static bool read_and_install_user_ce_key(userid_t user_id,
const android::vold::KeyAuthentication& auth) {
if (s_ce_key_raw_refs.count(user_id) != 0) return true;
KeyBuffer ce_key;
if (!read_and_fixate_user_ce_key(user_id, auth, &ce_key)) return false;
std::string ce_raw_ref;
+
+ if (is_wrapped_key_supported()) {
+ KeyBuffer ephemeral_wrapped_key;
+ if (!getEphemeralWrappedKey(KeyFormat::RAW, ce_key, &ephemeral_wrapped_key)) {
+ LOG(ERROR) << "Failed to export ce key";
+ return false;
+ }
+
+ ce_key = std::move(ephemeral_wrapped_key);
+ }
if (!android::vold::installKey(ce_key, &ce_raw_ref)) return false;
s_ce_keys[user_id] = std::move(ce_key);
s_ce_key_raw_refs[user_id] = ce_raw_ref;
@@ -335,6 +368,14 @@
KeyBuffer key;
if (!android::vold::retrieveKey(key_path, kEmptyAuthentication, &key)) return false;
std::string raw_ref;
+ if (is_wrapped_key_supported()) {
+ KeyBuffer ephemeral_wrapped_key;
+ if (!getEphemeralWrappedKey(KeyFormat::RAW, key, &ephemeral_wrapped_key)) {
+ LOG(ERROR) << "Failed to export de_key in create_and_install_user_keys";
+ return false;
+ }
+ key = std::move(ephemeral_wrapped_key);
+ }
if (!android::vold::installKey(key, &raw_ref)) return false;
s_de_key_raw_refs[user_id] = raw_ref;
LOG(DEBUG) << "Installed de key for user " << user_id << std::endl;
@@ -347,6 +388,7 @@
bool e4crypt_initialize_global_de() {
LOG(INFO) << "e4crypt_initialize_global_de" << std::endl;
+ bool wrapped_key_supported = false;
if (s_global_de_initialized) {
LOG(INFO) << "Already initialized" << std::endl;
@@ -354,9 +396,10 @@
}
PolicyKeyRef device_ref;
+ wrapped_key_supported = is_wrapped_key_supported();
LOG(INFO) << "calling retrieveAndInstallKey\n";
if (!android::vold::retrieveAndInstallKey(true, kEmptyAuthentication, device_key_path,
- device_key_temp, &device_ref.key_raw_ref))
+ device_key_temp, &device_ref.key_raw_ref, wrapped_key_supported))
return false;
get_data_file_encryption_modes(&device_ref);
@@ -535,6 +578,7 @@
PolicyKeyRef* key_ref) {
auto secdiscardable_path = volume_secdiscardable_path(volume_uuid);
std::string secdiscardable_hash;
+ bool wrapped_key_supported = false;
if (android::vold::pathExists(secdiscardable_path)) {
if (!android::vold::readSecdiscardable(secdiscardable_path, &secdiscardable_hash))
return false;
@@ -552,8 +596,9 @@
return false;
}
android::vold::KeyAuthentication auth("", secdiscardable_hash);
+ wrapped_key_supported = is_wrapped_key_supported_external();
if (!android::vold::retrieveAndInstallKey(true, auth, key_path, key_path + "_tmp",
- &key_ref->key_raw_ref))
+ &key_ref->key_raw_ref, wrapped_key_supported))
return false;
key_ref->contents_mode =
android::base::GetProperty("ro.crypto.volume.contents_mode", "aes-256-xts");
diff --git a/crypto/ext4crypt/Ext4CryptPie.h b/crypto/ext4crypt/Ext4CryptPie.h
index 6e2afa5..d6d6ecf 100644
--- a/crypto/ext4crypt/Ext4CryptPie.h
+++ b/crypto/ext4crypt/Ext4CryptPie.h
@@ -38,5 +38,8 @@
bool e4crypt_destroy_volume_keys(const std::string& volume_uuid);*/
+bool is_wrapped_key_supported();
+bool is_wrapped_key_supported_external();
+
bool lookup_key_ref(const std::map<userid_t, std::string>& key_map, userid_t user_id,
std::string* raw_ref);
diff --git a/crypto/ext4crypt/KeyStorage4.cpp b/crypto/ext4crypt/KeyStorage4.cpp
index 28efdf1..cab88a1 100644
--- a/crypto/ext4crypt/KeyStorage4.cpp
+++ b/crypto/ext4crypt/KeyStorage4.cpp
@@ -66,6 +66,7 @@
static constexpr size_t STRETCHED_BYTES = 1 << 6;
static constexpr uint32_t AUTH_TIMEOUT = 30; // Seconds
+constexpr int EXT4_AES_256_XTS_KEY_SIZE = 64;
static const char* kCurrentVersion = "1";
static const char* kRmPath = "/system/bin/rm";
@@ -131,6 +132,45 @@
return keymaster.generateKey(paramBuilder, key);
}
+bool generateWrappedKey(userid_t user_id, KeyType key_type,
+ KeyBuffer* key) {
+ Keymaster keymaster;
+ if (!keymaster) return false;
+ *key = KeyBuffer(EXT4_AES_256_XTS_KEY_SIZE);
+ std::string key_temp;
+ auto paramBuilder = km::AuthorizationSetBuilder()
+ .AesEncryptionKey(AES_KEY_BYTES * 8)
+ .GcmModeMinMacLen(GCM_MAC_BYTES * 8)
+ .Authorization(km::TAG_USER_ID, user_id);
+ km::KeyParameter param1;
+ param1.tag = (km::Tag) (android::hardware::keymaster::V4_0::KM_TAG_FBE_ICE);
+ param1.f.boolValue = true;
+ paramBuilder.push_back(param1);
+ km::KeyParameter param2;
+ if ((key_type == KeyType::DE_USER) || (key_type == KeyType::DE_SYS)) {
+ param2.tag = (km::Tag) (android::hardware::keymaster::V4_0::KM_TAG_KEY_TYPE);
+ param2.f.integer = 0;
+ } else if (key_type == KeyType::CE_USER) {
+ param2.tag = (km::Tag) (android::hardware::keymaster::V4_0::KM_TAG_KEY_TYPE);
+ param2.f.integer = 1;
+ }
+ paramBuilder.push_back(param2);
+ if (!keymaster.generateKey(paramBuilder, &key_temp)) return false;
+ *key = KeyBuffer(key_temp.size());
+ memcpy(reinterpret_cast<void*>(key->data()), key_temp.c_str(), key->size());
+ return true;
+}
+
+bool getEphemeralWrappedKey(km::KeyFormat format, KeyBuffer& kmKey, KeyBuffer* key) {
+ std::string key_temp;
+ Keymaster keymaster;
+ if (!keymaster) return false;
+ if (!keymaster.exportKey(format, kmKey, "!", "!", &key_temp)) return false;
+ *key = KeyBuffer(key_temp.size());
+ memcpy(reinterpret_cast<void*>(key->data()), key_temp.c_str(), key->size());
+ return true;
+}
+
static std::pair<km::AuthorizationSet, km::HardwareAuthToken> beginParams(
const KeyAuthentication& auth, const std::string& appId) {
auto paramBuilder = km::AuthorizationSetBuilder()
diff --git a/crypto/ext4crypt/KeyStorage4.h b/crypto/ext4crypt/KeyStorage4.h
index 35ff65e..f74865f 100644
--- a/crypto/ext4crypt/KeyStorage4.h
+++ b/crypto/ext4crypt/KeyStorage4.h
@@ -17,13 +17,17 @@
#ifndef ANDROID_TWRP_KEYSTORAGE_H
#define ANDROID_TWRP_KEYSTORAGE_H
+#include "Keymaster4.h"
#include "KeyBuffer.h"
+#include <ext4_utils/ext4_crypt.h>
#include <string>
namespace android {
namespace vold {
+namespace km = ::android::hardware::keymaster::V4_0;
+
// Represents the information needed to decrypt a disk encryption key.
// If "token" is nonempty, it is passed in as a required Gatekeeper auth token.
// If "token" and "secret" are nonempty, "secret" is appended to the application-specific
@@ -39,6 +43,12 @@
const std::string secret;
};
+enum class KeyType {
+ DE_SYS,
+ DE_USER,
+ CE_USER
+};
+
extern const KeyAuthentication kEmptyAuthentication;
// Checks if path "path" exists.
@@ -67,6 +77,9 @@
bool destroyKey(const std::string& dir);
bool runSecdiscardSingle(const std::string& file);
+
+bool generateWrappedKey(userid_t user_id, KeyType key_type, KeyBuffer* key);
+bool getEphemeralWrappedKey(km::KeyFormat format, KeyBuffer& kmKey, KeyBuffer* key);
} // namespace vold
} // namespace android
diff --git a/crypto/ext4crypt/KeyUtil.cpp b/crypto/ext4crypt/KeyUtil.cpp
index 946c6cf..3dc0500 100644
--- a/crypto/ext4crypt/KeyUtil.cpp
+++ b/crypto/ext4crypt/KeyUtil.cpp
@@ -27,6 +27,7 @@
#include <keyutils.h>
#include "KeyStorage4.h"
+#include "Ext4CryptPie.h"
#include "Utils.h"
#include <iostream>
@@ -35,6 +36,11 @@
#include <sys/types.h>
#include <unistd.h>
+#define MAX_USER_ID 0xFFFFFFFF
+
+using android::hardware::keymaster::V4_0::KeyFormat;
+using android::vold::KeyType;
+
namespace android {
namespace vold {
@@ -128,7 +134,14 @@
ext4_encryption_key &ext4_key = *reinterpret_cast<ext4_encryption_key*>(ext4KeyBuffer.data());
if (!fillKey(key, &ext4_key)) return false;
- *raw_ref = generateKeyRef(ext4_key.raw, ext4_key.size);
+ if (is_wrapped_key_supported()) {
+ /* When wrapped key is supported, only the first 32 bytes are
+ the same per boot. The second 32 bytes can change as the ephemeral
+ key is different. */
+ *raw_ref = generateKeyRef(ext4_key.raw, (ext4_key.size)/2);
+ } else {
+ *raw_ref = generateKeyRef(ext4_key.raw, ext4_key.size);
+ }
key_serial_t device_keyring;
if (!e4cryptKeyring(&device_keyring)) return false;
for (char const* const* name_prefix = NAME_PREFIXES; *name_prefix != nullptr; name_prefix++) {
@@ -171,7 +184,7 @@
bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_authentication,
const std::string& key_path, const std::string& tmp_path,
- std::string* key_ref) {
+ std::string* key_ref, bool wrapped_key_supported) {
KeyBuffer key;
if (pathExists(key_path)) {
LOG(DEBUG) << "Key exists, using: " << key_path << std::endl;
@@ -182,10 +195,23 @@
return false;
}
LOG(INFO) << "Creating new key in " << key_path << std::endl;
- if (!randomKey(&key)) return false;
+ if (wrapped_key_supported) {
+ if(!generateWrappedKey(MAX_USER_ID, KeyType::DE_SYS, &key)) return false;
+ } else {
+ if (!randomKey(&key)) return false;
+ }
if (!storeKeyAtomically(key_path, tmp_path, key_authentication, key)) return false;
}
+ if (wrapped_key_supported) {
+ KeyBuffer ephemeral_wrapped_key;
+ if (!getEphemeralWrappedKey(KeyFormat::RAW, key, &ephemeral_wrapped_key)) {
+ LOG(ERROR) << "Failed to export key in retrieveAndInstallKey";
+ return false;
+ }
+ key = std::move(ephemeral_wrapped_key);
+ }
+
if (!installKey(key, key_ref)) {
LOG(ERROR) << "Failed to install key in " << key_path << std::endl;
return false;
diff --git a/crypto/ext4crypt/KeyUtil.h b/crypto/ext4crypt/KeyUtil.h
index d5ad69f..46a3124 100644
--- a/crypto/ext4crypt/KeyUtil.h
+++ b/crypto/ext4crypt/KeyUtil.h
@@ -19,6 +19,7 @@
#include "KeyBuffer.h"
#include "KeyStorage4.h"
+#include "Keymaster4.h"
#include <string>
#include <memory>
@@ -31,7 +32,7 @@
bool evictKey(const std::string& raw_ref);
bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_authentication,
const std::string& key_path, const std::string& tmp_path,
- std::string* key_ref);
+ std::string* key_ref, bool wrapped_key_supported);
bool retrieveKey(bool create_if_absent, const std::string& key_path,
const std::string& tmp_path, KeyBuffer* key);
diff --git a/crypto/ext4crypt/Keymaster4.cpp b/crypto/ext4crypt/Keymaster4.cpp
index cebe1f1..e5c059a 100644
--- a/crypto/ext4crypt/Keymaster4.cpp
+++ b/crypto/ext4crypt/Keymaster4.cpp
@@ -142,6 +142,32 @@
return true;
}
+bool Keymaster::exportKey(km::KeyFormat format, KeyBuffer& kmKey, const std::string& clientId,
+ const std::string& appData, std::string* key) {
+ auto kmKeyBlob = km::support::blob2hidlVec(std::string(kmKey.data(), kmKey.size()));
+ auto emptyAssign = NULL;
+ auto kmClientId = (clientId == "!") ? emptyAssign: km::support::blob2hidlVec(clientId);
+ auto kmAppData = (appData == "!") ? emptyAssign: km::support::blob2hidlVec(appData);
+ km::ErrorCode km_error;
+ auto hidlCb = [&](km::ErrorCode ret, const hidl_vec<uint8_t>& exportedKeyBlob) {
+ km_error = ret;
+ if (km_error != km::ErrorCode::OK) return;
+ if(key)
+ key->assign(reinterpret_cast<const char*>(&exportedKeyBlob[0]),
+ exportedKeyBlob.size());
+ };
+ auto error = mDevice->exportKey(format, kmKeyBlob, kmClientId, kmAppData, hidlCb);
+ if (!error.isOk()) {
+ LOG(ERROR) << "export_key failed: " << error.description();
+ return false;
+ }
+ if (km_error != km::ErrorCode::OK) {
+ LOG(ERROR) << "export_key failed, code " << int32_t(km_error);
+ return false;
+ }
+ return true;
+}
+
bool Keymaster::deleteKey(const std::string& key) {
LOG(ERROR) << "not actually deleting key\n";
return true;
diff --git a/crypto/ext4crypt/Keymaster4.h b/crypto/ext4crypt/Keymaster4.h
index 37bff4e..14c230b 100644
--- a/crypto/ext4crypt/Keymaster4.h
+++ b/crypto/ext4crypt/Keymaster4.h
@@ -102,6 +102,9 @@
explicit operator bool() { return mDevice.get() != nullptr; }
// Generate a key in the keymaster from the given params.
bool generateKey(const km::AuthorizationSet& inParams, std::string* key);
+ // Export a key from keymaster.
+ bool exportKey(km::KeyFormat format, KeyBuffer& kmKey, const std::string& clientId,
+ const std::string& appData, std::string* key);
// If the keymaster supports it, permanently delete a key.
bool deleteKey(const std::string& key);
// Replace stored key blob in response to KM_ERROR_KEY_REQUIRES_UPGRADE.