fscrypt: Wrapped key support for FBE

Commit imported from:

https: //github.com/LineageOS/android_system_vold/commit/ce024f07c23d0649635a336fff389332b9806f48
Change-Id: I924a9fcbac7d790609fbafcf8c12654fdb267e32

crypto/fscrypt/FsCrypt.cpp

@@ -16,6 +16,7 @@
 
 #include "FsCrypt.h"
 
+#include "Keymaster.h"
 #include "KeyStorage.h"
 #include "KeyUtil.h"
 #include "Utils.h"
@@ -65,6 +66,8 @@ using android::base::StringPrintf;
 using android::fs_mgr::GetEntryForMountPoint;
 using android::vold::kEmptyAuthentication;
 using android::vold::KeyBuffer;
+using android::vold::Keymaster;
+using android::hardware::keymaster::V4_0::KeyFormat;
 // using android::vold::writeStringToFile;
 
 // Store main DE raw ref / policy
@@ -207,12 +210,45 @@ static bool read_and_fixate_user_ce_key(userid_t user_id,
     return false;
 }
 
+static bool is_wrapped_key_supported_common(const std::string& mount_point) {
+    struct fstab_rec* rec = fs_mgr_get_entry_for_mount_point(fstab_default, mount_point);
+    char const* contents_mode = NULL;
+    char const* filenames_mode = NULL;
+
+    fs_mgr_get_file_encryption_modes(rec, &contents_mode, &filenames_mode);
+    if (!contents_mode || !filenames_mode) {
+        LOG(ERROR) << "Couldn't read file or contents mode, returning false";
+        return false;
+    }
+
+    if (strcmp(contents_mode, "ice_wrapped_key_supported") == 0)
+        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;
@@ -242,8 +278,15 @@ static bool destroy_dir(const std::string& dir) {
 // it creates keys in a fixed location.
 static bool create_and_install_user_keys(userid_t user_id, bool create_ephemeral) {
     KeyBuffer de_key, ce_key;
-    if (!android::vold::randomKey(&de_key)) return false;
-    if (!android::vold::randomKey(&ce_key)) return false;
+
+    if(is_wrapped_key_supported()) {
+        if (!generateWrappedKey(user_id, android::vold::KeyType::DE_USER, &de_key)) return false;
+        if (!generateWrappedKey(user_id, android::vold::KeyType::CE_USER, &ce_key)) return false;
+    } else {
+        if (!android::vold::randomKey(&de_key)) return false;
+        if (!android::vold::randomKey(&ce_key)) return false;
+    }
+
     if (create_ephemeral) {
         // If the key should be created as ephemeral, don't store it.
         s_ephemeral_users.insert(user_id);
@@ -262,12 +305,33 @@ static bool create_and_install_user_keys(userid_t user_id, bool create_ephemeral
                                                kEmptyAuthentication, de_key))
             return false;
     }
-    if (!android::vold::installKey(de_key, &de_raw_ref)) return false;
-    s_de_key_raw_refs[user_id] = de_raw_ref;
+
     std::string ce_raw_ref;
+    if (is_wrapped_key_supported()) {
+        KeyBuffer ephemeral_wrapped_de_key;
+        KeyBuffer ephemeral_wrapped_ce_key;
+
+        /* Export and install the DE keys */
+        if (!getEphemeralWrappedKey(KeyFormat::RAW, de_key, &ephemeral_wrapped_de_key)) {
+           LOG(ERROR) << "Failed to export de_key";
+           return false;
+        }
+        /* Export and install the CE keys */
+        if (!getEphemeralWrappedKey(KeyFormat::RAW, ce_key, &ephemeral_wrapped_ce_key)) {
+           LOG(ERROR) << "Failed to export de_key";
+           return false;
+        }
+
+        de_key = std::move(ephemeral_wrapped_de_key);
+        ce_key = std::move(ephemeral_wrapped_ce_key);
+    }
+    if (!android::vold::installKey(de_key, &de_raw_ref)) return false;
     if (!android::vold::installKey(ce_key, &ce_raw_ref)) return false;
-    s_ce_keys[user_id] = ce_key;
+    s_ce_keys[user_id] = std::move(ce_key);
+
+    s_de_key_raw_refs[user_id] = de_raw_ref;
     s_ce_key_raw_refs[user_id] = ce_raw_ref;
+
     LOG(DEBUG) << "Created keys for user " << user_id;
     return true;
 }
@@ -337,6 +401,14 @@ static bool load_all_de_keys() {
             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;
@@ -349,6 +421,7 @@ static bool load_all_de_keys() {
 
 bool fscrypt_initialize_systemwide_keys() {
     LOG(INFO) << "fscrypt_initialize_systemwide_keys";
+    bool wrapped_key_supported = false;
 
     if (s_systemwide_keys_initialized) {
         LOG(INFO) << "Already initialized";
@@ -356,8 +429,11 @@ bool fscrypt_initialize_systemwide_keys() {
     }
 
     PolicyKeyRef device_ref;
-    if (!android::vold::retrieveAndInstallKey(true, kEmptyAuthentication, device_key_path,
-                                              device_key_temp, &device_ref.key_raw_ref))
+    wrapped_key_supported = is_wrapped_key_supported();
+
+    if (!android::vold::retrieveAndInstallKey(true, kEmptyAuthentication,
+                       device_key_path, device_key_temp,
+                           &device_ref.key_raw_ref, wrapped_key_supported))
         return false;
     get_data_file_encryption_modes(&device_ref);
 
@@ -537,6 +613,7 @@ static bool read_or_create_volkey(const std::string& misc_path, const std::strin
                                   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;
@@ -554,8 +631,10 @@ static bool read_or_create_volkey(const std::string& misc_path, const std::strin
         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");
@@ -581,14 +660,28 @@ bool fscrypt_add_user_key_auth(userid_t user_id, int serial, const std::string&
     if (!parse_hex(secret_hex, &secret)) return false;
     auto auth =
         secret.empty() ? kEmptyAuthentication : android::vold::KeyAuthentication(token, secret);
-    auto it = s_ce_keys.find(user_id);
-    if (it == s_ce_keys.end()) {
-        LOG(ERROR) << "Key not loaded into memory, can't change for user " << user_id;
-        return false;
-    }
-    const auto& ce_key = it->second;
     auto const directory_path = get_ce_key_directory_path(user_id);
     auto const paths = get_ce_key_paths(directory_path);
+
+    KeyBuffer ce_key;
+    if(is_wrapped_key_supported()) {
+        std::string ce_key_current_path = get_ce_key_current_path(directory_path);
+        if (android::vold::retrieveKey(ce_key_current_path, kEmptyAuthentication, &ce_key)) {
+            LOG(DEBUG) << "Successfully retrieved key";
+        } else {
+            if (android::vold::retrieveKey(ce_key_current_path, auth, &ce_key)) {
+                LOG(DEBUG) << "Successfully retrieved key";
+            }
+        }
+    } else {
+        auto it = s_ce_keys.find(user_id);
+        if (it == s_ce_keys.end()) {
+            LOG(ERROR) << "Key not loaded into memory, can't change for user " << user_id;
+            return false;
+        }
+        ce_key = it->second;
+    }
+
     std::string ce_key_path;
     if (!get_ce_key_new_path(directory_path, paths, &ce_key_path)) return false;
     if (!android::vold::storeKeyAtomically(ce_key_path, user_key_temp, auth, ce_key)) return false;
@@ -596,6 +689,46 @@ bool fscrypt_add_user_key_auth(userid_t user_id, int serial, const std::string&
     return true;
 }
 
+bool fscrypt_clear_user_key_auth(userid_t user_id, int serial, const std::string& token_hex,
+                                 const std::string& secret_hex) {
+    LOG(DEBUG) << "fscrypt_clear_user_key_auth " << user_id << " serial=" << serial
+               << " token_present=" << (token_hex != "!");
+    if (!fscrypt_is_native()) return true;
+    if (s_ephemeral_users.count(user_id) != 0) return true;
+    std::string token, secret;
+
+    if (!parse_hex(token_hex, &token)) return false;
+    if (!parse_hex(secret_hex, &secret)) return false;
+
+    if (is_wrapped_key_supported()) {
+        auto const directory_path = get_ce_key_directory_path(user_id);
+        auto const paths = get_ce_key_paths(directory_path);
+
+        KeyBuffer ce_key;
+        std::string ce_key_current_path = get_ce_key_current_path(directory_path);
+
+        auto auth = android::vold::KeyAuthentication(token, secret);
+        /* Retrieve key while removing a pin. A secret is needed */
+        if (android::vold::retrieveKey(ce_key_current_path, auth, &ce_key)) {
+            LOG(DEBUG) << "Successfully retrieved key";
+        } else {
+            /* Retrieve key when going None to swipe and vice versa when a
+               synthetic password is present */
+            if (android::vold::retrieveKey(ce_key_current_path, kEmptyAuthentication, &ce_key)) {
+                LOG(DEBUG) << "Successfully retrieved key";
+            }
+        }
+
+        std::string ce_key_path;
+        if (!get_ce_key_new_path(directory_path, paths, &ce_key_path)) return false;
+        if (!android::vold::storeKeyAtomically(ce_key_path, user_key_temp, kEmptyAuthentication, ce_key))
+            return false;
+    } else {
+        if(!fscrypt_add_user_key_auth(user_id, serial, "!", "!")) return false;
+    }
+    return true;
+}
+
 bool fscrypt_fixate_newest_user_key_auth(userid_t user_id) {
     LOG(DEBUG) << "fscrypt_fixate_newest_user_key_auth " << user_id;
     if (!fscrypt_is_native()) return true;

crypto/fscrypt/FsCrypt.h

@@ -27,6 +27,8 @@ bool fscrypt_vold_create_user_key(userid_t user_id, int serial, bool ephemeral);
 bool fscrypt_destroy_user_key(userid_t user_id);
 bool fscrypt_add_user_key_auth(userid_t user_id, int serial, const std::string& token,
                                const std::string& secret);
+bool fscrypt_clear_user_key_auth(userid_t user_id, int serial, const std::string& token_hex,
+                               const std::string& secret_hex);
 bool fscrypt_fixate_newest_user_key_auth(userid_t user_id);
 
 bool fscrypt_unlock_user_key(userid_t user_id, int serial, const std::string& token,
@@ -38,6 +40,7 @@ bool fscrypt_prepare_user_storage(const std::string& volume_uuid, userid_t user_
 bool fscrypt_destroy_user_storage(const std::string& volume_uuid, userid_t user_id, int flags);
 
 bool fscrypt_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);

crypto/fscrypt/KeyStorage.cpp

@@ -64,6 +64,7 @@ static constexpr size_t SECDISCARDABLE_BYTES = 1 << 14;
 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";
@@ -129,6 +130,47 @@ static bool generateKeymasterKey(Keymaster& keymaster, const KeyAuthentication&
     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()

crypto/fscrypt/KeyStorage.h

@@ -17,8 +17,9 @@
 #ifndef ANDROID_VOLD_KEYSTORAGE_H
 #define ANDROID_VOLD_KEYSTORAGE_H
 
+#include "Keymaster.h"
 #include "KeyBuffer.h"
-
+#include <cutils/multiuser.h>
 #include <string>
 
 namespace android {
@@ -39,6 +40,12 @@ class KeyAuthentication {
     const std::string secret;
 };
 
+enum class KeyType {
+    DE_SYS,
+    DE_USER,
+    CE_USER
+};
+
 extern const KeyAuthentication kEmptyAuthentication;
 
 // Checks if path "path" exists.
@@ -68,6 +75,8 @@ bool retrieveKey(const std::string& dir, const KeyAuthentication& auth, KeyBuffe
 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
 

crypto/fscrypt/KeyUtil.cpp

@@ -27,9 +27,14 @@
 #include <android-base/logging.h>
 #include <keyutils.h>
 
+#include "FsCrypt.h"
 #include "KeyStorage.h"
 #include "Utils.h"
 
+#define MAX_USER_ID 0xFFFFFFFF
+
+using android::hardware::keymaster::V4_0::KeyFormat;
+using android::vold::KeyType;
 namespace android {
 namespace vold {
 
@@ -105,7 +110,14 @@ bool installKey(const KeyBuffer& key, std::string* raw_ref) {
     fscrypt_key& fs_key = *reinterpret_cast<fscrypt_key*>(fsKeyBuffer.data());
 
     if (!fillKey(key, &fs_key)) return false;
-    *raw_ref = generateKeyRef(fs_key.raw, fs_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(fs_key.raw, (fs_key.size)/2);
+    } else {
+        *raw_ref = generateKeyRef(fs_key.raw, fs_key.size);
+    }
     key_serial_t device_keyring;
     if (!fscryptKeyring(&device_keyring)) return false;
     for (char const* const* name_prefix = NAME_PREFIXES; *name_prefix != nullptr; name_prefix++) {
@@ -146,7 +158,7 @@ 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) {
     KeyBuffer key;
     if (pathExists(key_path)) {
         LOG(DEBUG) << "Key exists, using: " << key_path;
@@ -157,10 +169,23 @@ bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_a
             return false;
         }
         LOG(INFO) << "Creating new key in " << key_path;
-        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;
         return false;

crypto/fscrypt/KeyUtil.h

@@ -19,6 +19,7 @@
 
 #include "KeyBuffer.h"
 #include "KeyStorage.h"
+#include "Keymaster.h"
 
 #include <memory>
 #include <string>
@@ -31,7 +32,7 @@ bool installKey(const KeyBuffer& key, std::string* raw_ref);
 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, bool keepOld = true);
 

crypto/fscrypt/Keymaster.cpp

@@ -138,6 +138,32 @@ bool Keymaster::generateKey(const km::AuthorizationSet& inParams, std::string* k
     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) {
     auto keyBlob = km::support::blob2hidlVec(key);
     auto error = mDevice->deleteKey(keyBlob);

crypto/fscrypt/Keymaster.h

@@ -102,6 +102,9 @@ class Keymaster {
     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.