Merge changes from topic "fscrypt-key-mgmt-improvements" am: 22d50012b0

am: de5c9ad178

Change-Id: I8f9bfce21f40607f95eee57fed835e35abbd02c6

FsCrypt.cpp

@@ -57,6 +57,7 @@
 #include <android-base/logging.h>
 #include <android-base/properties.h>
 #include <android-base/stringprintf.h>
+#include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 
 using android::base::StringPrintf;
@@ -70,7 +71,10 @@ namespace {
 struct PolicyKeyRef {
     std::string contents_mode;
     std::string filenames_mode;
+    int policy_version;
     std::string key_raw_ref;
+
+    PolicyKeyRef() : policy_version(0) {}
 };
 
 const std::string device_key_dir = std::string() + DATA_MNT_POINT + fscrypt_unencrypted_folder;
@@ -199,14 +203,57 @@ static bool read_and_fixate_user_ce_key(userid_t user_id,
     return false;
 }
 
+// Retrieve the options to use for encryption policies on the /data filesystem.
+static void get_data_file_encryption_options(PolicyKeyRef* key_ref) {
+    auto entry = GetEntryForMountPoint(&fstab_default, DATA_MNT_POINT);
+    if (entry == nullptr) {
+        return;
+    }
+    key_ref->contents_mode = entry->file_contents_mode;
+    key_ref->filenames_mode = entry->file_names_mode;
+    key_ref->policy_version = entry->file_policy_version;
+}
+
+// Retrieve the version to use for encryption policies on the /data filesystem.
+static int get_data_file_policy_version(void) {
+    auto entry = GetEntryForMountPoint(&fstab_default, DATA_MNT_POINT);
+    if (entry == nullptr) {
+        return 0;
+    }
+    return entry->file_policy_version;
+}
+
+// Retrieve the options to use for encryption policies on adoptable storage.
+static bool get_volume_file_encryption_options(PolicyKeyRef* key_ref) {
+    key_ref->contents_mode =
+            android::base::GetProperty("ro.crypto.volume.contents_mode", "aes-256-xts");
+    key_ref->filenames_mode =
+            android::base::GetProperty("ro.crypto.volume.filenames_mode", "aes-256-heh");
+    key_ref->policy_version = 1;
+
+    std::string raw_flags = android::base::GetProperty("ro.crypto.volume.flags", "");
+    auto flags = android::base::Split(raw_flags, "+");
+    for (const auto& flag : flags) {
+        if (flag == "v1") {
+            key_ref->policy_version = 1;
+        } else if (flag == "v2") {
+            key_ref->policy_version = 2;
+        } else {
+            LOG(ERROR) << "Unknown flag in ro.crypto.volume.flags: " << flag;
+            return false;
+        }
+    }
+    return true;
+}
+
 // Install a key for use by encrypted files on the /data filesystem.
 static bool install_data_key(const KeyBuffer& key, std::string* raw_ref) {
-    return android::vold::installKey(key, DATA_MNT_POINT, raw_ref);
+    return android::vold::installKey(key, DATA_MNT_POINT, get_data_file_policy_version(), raw_ref);
 }
 
 // Evict a key for use by encrypted files on the /data filesystem.
 static bool evict_data_key(const std::string& raw_ref) {
-    return android::vold::evictKey(DATA_MNT_POINT, raw_ref);
+    return android::vold::evictKey(DATA_MNT_POINT, raw_ref, get_data_file_policy_version());
 }
 
 static bool read_and_install_user_ce_key(userid_t user_id,
@@ -286,19 +333,10 @@ static bool lookup_key_ref(const std::map<userid_t, std::string>& key_map, useri
     return true;
 }
 
-static void get_data_file_encryption_modes(PolicyKeyRef* key_ref) {
-    auto entry = GetEntryForMountPoint(&fstab_default, DATA_MNT_POINT);
-    if (entry == nullptr) {
-        return;
-    }
-    key_ref->contents_mode = entry->file_contents_mode;
-    key_ref->filenames_mode = entry->file_names_mode;
-}
-
 static bool ensure_policy(const PolicyKeyRef& key_ref, const std::string& path) {
     return fscrypt_policy_ensure(path.c_str(), key_ref.key_raw_ref.data(),
                                  key_ref.key_raw_ref.size(), key_ref.contents_mode.c_str(),
-                                 key_ref.filenames_mode.c_str()) == 0;
+                                 key_ref.filenames_mode.c_str(), key_ref.policy_version) == 0;
 }
 
 static bool is_numeric(const char* name) {
@@ -354,14 +392,18 @@ bool fscrypt_initialize_systemwide_keys() {
     }
 
     PolicyKeyRef device_ref;
+    get_data_file_encryption_options(&device_ref);
+
     if (!android::vold::retrieveAndInstallKey(true, kEmptyAuthentication, device_key_path,
-                                              device_key_temp, "", &device_ref.key_raw_ref))
+                                              device_key_temp, "", device_ref.policy_version,
+                                              &device_ref.key_raw_ref))
         return false;
-    get_data_file_encryption_modes(&device_ref);
 
-    std::string modestring = device_ref.contents_mode + ":" + device_ref.filenames_mode;
-    std::string mode_filename = std::string("/data") + fscrypt_key_mode;
-    if (!android::vold::writeStringToFile(modestring, mode_filename)) return false;
+    std::string options_string =
+            StringPrintf("%s:%s:v%d", device_ref.contents_mode.c_str(),
+                         device_ref.filenames_mode.c_str(), device_ref.policy_version);
+    std::string options_filename = std::string("/data") + fscrypt_key_mode;
+    if (!android::vold::writeStringToFile(options_string, options_filename)) return false;
 
     std::string ref_filename = std::string("/data") + fscrypt_key_ref;
     if (!android::vold::writeStringToFile(device_ref.key_raw_ref, ref_filename)) return false;
@@ -560,14 +602,12 @@ static bool read_or_create_volkey(const std::string& misc_path, const std::strin
         return false;
     }
     android::vold::KeyAuthentication auth("", secdiscardable_hash);
-    if (!android::vold::retrieveAndInstallKey(true, auth, key_path, key_path + "_tmp", volume_uuid,
-                                              &key_ref->key_raw_ref))
-        return false;
-    key_ref->contents_mode =
-        android::base::GetProperty("ro.crypto.volume.contents_mode", "aes-256-xts");
-    key_ref->filenames_mode =
-        android::base::GetProperty("ro.crypto.volume.filenames_mode", "aes-256-heh");
-    return true;
+
+    if (!get_volume_file_encryption_options(key_ref)) return false;
+
+    return android::vold::retrieveAndInstallKey(true, auth, key_path, key_path + "_tmp",
+                                                volume_uuid, key_ref->policy_version,
+                                                &key_ref->key_raw_ref);
 }
 
 static bool destroy_volkey(const std::string& misc_path, const std::string& volume_uuid) {
@@ -715,7 +755,7 @@ bool fscrypt_prepare_user_storage(const std::string& volume_uuid, userid_t user_
             PolicyKeyRef de_ref;
             if (volume_uuid.empty()) {
                 if (!lookup_key_ref(s_de_key_raw_refs, user_id, &de_ref.key_raw_ref)) return false;
-                get_data_file_encryption_modes(&de_ref);
+                get_data_file_encryption_options(&de_ref);
                 if (!ensure_policy(de_ref, system_de_path)) return false;
                 if (!ensure_policy(de_ref, misc_de_path)) return false;
                 if (!ensure_policy(de_ref, vendor_de_path)) return false;
@@ -746,7 +786,7 @@ bool fscrypt_prepare_user_storage(const std::string& volume_uuid, userid_t user_
             PolicyKeyRef ce_ref;
             if (volume_uuid.empty()) {
                 if (!lookup_key_ref(s_ce_key_raw_refs, user_id, &ce_ref.key_raw_ref)) return false;
-                get_data_file_encryption_modes(&ce_ref);
+                get_data_file_encryption_options(&ce_ref);
                 if (!ensure_policy(ce_ref, system_ce_path)) return false;
                 if (!ensure_policy(ce_ref, misc_ce_path)) return false;
                 if (!ensure_policy(ce_ref, vendor_ce_path)) return false;

KeyUtil.cpp

@@ -163,28 +163,80 @@ static bool installKeyLegacy(const KeyBuffer& key, const std::string& raw_ref) {
     return true;
 }
 
+// Build a struct fscrypt_key_specifier for use in the key management ioctls.
+static bool buildKeySpecifier(fscrypt_key_specifier* spec, const std::string& raw_ref,
+                              int policy_version) {
+    switch (policy_version) {
+        case 1:
+            if (raw_ref.size() != FSCRYPT_KEY_DESCRIPTOR_SIZE) {
+                LOG(ERROR) << "Invalid key specifier size for v1 encryption policy: "
+                           << raw_ref.size();
+                return false;
+            }
+            spec->type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
+            memcpy(spec->u.descriptor, raw_ref.c_str(), FSCRYPT_KEY_DESCRIPTOR_SIZE);
+            return true;
+        case 2:
+            if (raw_ref.size() != FSCRYPT_KEY_IDENTIFIER_SIZE) {
+                LOG(ERROR) << "Invalid key specifier size for v2 encryption policy: "
+                           << raw_ref.size();
+                return false;
+            }
+            spec->type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
+            memcpy(spec->u.identifier, raw_ref.c_str(), FSCRYPT_KEY_IDENTIFIER_SIZE);
+            return true;
+        default:
+            LOG(ERROR) << "Invalid encryption policy version: " << policy_version;
+            return false;
+    }
+}
+
 // Install a file-based encryption key to the kernel, for use by encrypted files
-// on the specified filesystem.
+// on the specified filesystem using the specified encryption policy version.
 //
-// We use FS_IOC_ADD_ENCRYPTION_KEY if the kernel supports it.  Otherwise we add
-// the key to the legacy global session keyring.
+// For v1 policies, we use FS_IOC_ADD_ENCRYPTION_KEY if the kernel supports it.
+// Otherwise we add the key to the legacy global session keyring.
+//
+// For v2 policies, we always use FS_IOC_ADD_ENCRYPTION_KEY; it's the only way
+// the kernel supports.
 //
 // Returns %true on success, %false on failure.  On success also sets *raw_ref
 // to the raw key reference for use in the encryption policy.
-bool installKey(const KeyBuffer& key, const std::string& mountpoint, std::string* raw_ref) {
-    *raw_ref = generateKeyRef((const uint8_t*)key.data(), key.size());
-    if (!isFsKeyringSupported()) {
-        return installKeyLegacy(key, *raw_ref);
-    }
-
+bool installKey(const KeyBuffer& key, const std::string& mountpoint, int policy_version,
+                std::string* raw_ref) {
     // Put the fscrypt_add_key_arg in an automatically-zeroing buffer, since we
     // have to copy the raw key into it.
     KeyBuffer arg_buf(sizeof(struct fscrypt_add_key_arg) + key.size(), 0);
     struct fscrypt_add_key_arg* arg = (struct fscrypt_add_key_arg*)arg_buf.data();
 
-    arg->key_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
-    memcpy(arg->key_spec.u.descriptor, raw_ref.c_str(), FSCRYPT_KEY_DESCRIPTOR_SIZE);
+    // Initialize the "key specifier", which is like a name for the key.
+    switch (policy_version) {
+        case 1:
+            // A key for a v1 policy is specified by an arbitrary 8-byte
+            // "descriptor", which must be provided by userspace.  We use the
+            // first 8 bytes from the double SHA-512 of the key itself.
+            *raw_ref = generateKeyRef((const uint8_t*)key.data(), key.size());
+            if (!isFsKeyringSupported()) {
+                return installKeyLegacy(key, *raw_ref);
+            }
+            if (!buildKeySpecifier(&arg->key_spec, *raw_ref, policy_version)) {
+                return false;
+            }
+            break;
+        case 2:
+            // A key for a v2 policy is specified by an 16-byte "identifier",
+            // which is a cryptographic hash of the key itself which the kernel
+            // computes and returns.  Any user-provided value is ignored; we
+            // just need to set the specifier type to indicate that we're adding
+            // this type of key.
+            arg->key_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
+            break;
+        default:
+            LOG(ERROR) << "Invalid encryption policy version: " << policy_version;
+            return false;
+    }
 
+    // Provide the raw key.
     arg->raw_size = key.size();
     memcpy(arg->raw, key.data(), key.size());
 
@@ -195,11 +247,14 @@ bool installKey(const KeyBuffer& key, const std::string& mountpoint, std::string
     }
 
     if (ioctl(fd, FS_IOC_ADD_ENCRYPTION_KEY, arg) != 0) {
-        PLOG(ERROR) << "Failed to install fscrypt key with ref " << keyrefstring(*raw_ref) << " to "
-                    << mountpoint;
+        PLOG(ERROR) << "Failed to install fscrypt key to " << mountpoint;
         return false;
     }
 
+    if (arg->key_spec.type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) {
+        // Retrieve the key identifier that the kernel computed.
+        *raw_ref = std::string((char*)arg->key_spec.u.identifier, FSCRYPT_KEY_IDENTIFIER_SIZE);
+    }
     LOG(DEBUG) << "Installed fscrypt key with ref " << keyrefstring(*raw_ref) << " to "
                << mountpoint;
     return true;
@@ -234,8 +289,8 @@ static bool evictKeyLegacy(const std::string& raw_ref) {
 // remove the key from the legacy global session keyring.
 //
 // In the latter case, the caller is responsible for dropping caches.
-bool evictKey(const std::string& mountpoint, const std::string& raw_ref) {
-    if (!isFsKeyringSupported()) {
+bool evictKey(const std::string& mountpoint, const std::string& raw_ref, int policy_version) {
+    if (policy_version == 1 && !isFsKeyringSupported()) {
         return evictKeyLegacy(raw_ref);
     }
 
@@ -248,8 +303,9 @@ bool evictKey(const std::string& mountpoint, const std::string& raw_ref) {
     struct fscrypt_remove_key_arg arg;
     memset(&arg, 0, sizeof(arg));
 
-    arg.key_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
-    memcpy(arg.key_spec.u.descriptor, raw_ref.c_str(), FSCRYPT_KEY_DESCRIPTOR_SIZE);
+    if (!buildKeySpecifier(&arg.key_spec, raw_ref, policy_version)) {
+        return false;
+    }
 
     std::string ref = keyrefstring(raw_ref);
 
@@ -271,7 +327,8 @@ bool evictKey(const std::string& mountpoint, 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,
-                           const std::string& volume_uuid, std::string* key_ref) {
+                           const std::string& volume_uuid, int policy_version,
+                           std::string* key_ref) {
     KeyBuffer key;
     if (pathExists(key_path)) {
         LOG(DEBUG) << "Key exists, using: " << key_path;
@@ -286,7 +343,7 @@ bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_a
         if (!storeKeyAtomically(key_path, tmp_path, key_authentication, key)) return false;
     }
 
-    if (!installKey(key, BuildDataPath(volume_uuid), key_ref)) {
+    if (!installKey(key, BuildDataPath(volume_uuid), policy_version, key_ref)) {
         LOG(ERROR) << "Failed to install key in " << key_path;
         return false;
     }

KeyUtil.h

@@ -30,11 +30,13 @@ bool randomKey(KeyBuffer* key);
 
 bool isFsKeyringSupported(void);
 
-bool installKey(const KeyBuffer& key, const std::string& mountpoint, std::string* raw_ref);
-bool evictKey(const std::string& mountpoint, const std::string& raw_ref);
+bool installKey(const KeyBuffer& key, const std::string& mountpoint, int policy_version,
+                std::string* raw_ref);
+bool evictKey(const std::string& mountpoint, const std::string& raw_ref, int policy_version);
 bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_authentication,
                            const std::string& key_path, const std::string& tmp_path,
-                           const std::string& volume_uuid, std::string* key_ref);
+                           const std::string& volume_uuid, int policy_version,
+                           std::string* key_ref);
 bool retrieveKey(bool create_if_absent, const std::string& key_path, const std::string& tmp_path,
                  KeyBuffer* key, bool keepOld = true);