Merge "Revert "Remove fsverity_init"" into main

fsverity_init/Android.bp

@@ -0,0 +1,25 @@
+package {
+    // See: http://go/android-license-faq
+    // A large-scale-change added 'default_applicable_licenses' to import
+    // all of the 'license_kinds' from "system_security_license"
+    // to get the below license kinds:
+    //   SPDX-license-identifier-Apache-2.0
+    default_applicable_licenses: ["system_security_license"],
+}
+
+cc_binary {
+    name: "fsverity_init",
+    srcs: [
+        "fsverity_init.cpp",
+    ],
+    static_libs: [
+        "libc++fs",
+        "libmini_keyctl_static",
+    ],
+    shared_libs: [
+        "libbase",
+        "libkeyutils",
+        "liblog",
+    ],
+    cflags: ["-Werror", "-Wall", "-Wextra"],
+}

fsverity_init/OWNERS

@@ -0,0 +1,5 @@
+alanstokes@google.com
+ebiggers@google.com
+jeffv@google.com
+jiyong@google.com
+victorhsieh@google.com

fsverity_init/fsverity_init.cpp

@@ -0,0 +1,104 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// fsverity_init is a tool for loading X.509 certificates into the kernel keyring used by the
+// fsverity builtin signature verification kernel feature
+// (https://www.kernel.org/doc/html/latest/filesystems/fsverity.html#built-in-signature-verification).
+// Starting in Android 14, Android has actually stopped using this feature, as it was too inflexible
+// and caused problems.  It has been replaced by userspace signature verification.  Also, some uses
+// of fsverity in Android are now for integrity-only use cases.
+//
+// Regardless, there may exist fsverity files on-disk that were created by Android 13 or earlier.
+// These files still have builtin signatures.  If the kernel is an older kernel that still has
+// CONFIG_FS_VERITY_BUILTIN_SIGNATURES enabled, these files cannot be opened unless the
+// corresponding key is in the ".fs-verity" keyring.  Therefore, this tool still has to exist and be
+// used to load keys into the kernel, even though this has no security purpose anymore.
+//
+// This tool can be removed as soon as all supported kernels are guaranteed to have
+// CONFIG_FS_VERITY_BUILTIN_SIGNATURES disabled, or alternatively as soon as support for upgrades
+// from Android 13 or earlier is no longer required.
+//
+
+#define LOG_TAG "fsverity_init"
+
+#include <sys/types.h>
+
+#include <filesystem>
+#include <string>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/strings.h>
+#include <log/log.h>
+#include <mini_keyctl_utils.h>
+
+void LoadKeyFromFile(key_serial_t keyring_id, const char* keyname, const std::string& path) {
+    LOG(INFO) << "LoadKeyFromFile path=" << path << " keyname=" << keyname;
+    std::string content;
+    if (!android::base::ReadFileToString(path, &content)) {
+        LOG(ERROR) << "Failed to read key from " << path;
+        return;
+    }
+    if (add_key("asymmetric", keyname, content.c_str(), content.size(), keyring_id) < 0) {
+        PLOG(ERROR) << "Failed to add key from " << path;
+    }
+}
+
+void LoadKeyFromDirectory(key_serial_t keyring_id, const char* keyname_prefix, const char* dir) {
+    if (!std::filesystem::exists(dir)) {
+        return;
+    }
+    int counter = 0;
+    for (const auto& entry : std::filesystem::directory_iterator(dir)) {
+        if (!android::base::EndsWithIgnoreCase(entry.path().c_str(), ".der")) continue;
+        std::string keyname = keyname_prefix + std::to_string(counter);
+        counter++;
+        LoadKeyFromFile(keyring_id, keyname.c_str(), entry.path());
+    }
+}
+
+void LoadKeyFromVerifiedPartitions(key_serial_t keyring_id) {
+    // NB: Directories need to be synced with FileIntegrityService.java in
+    // frameworks/base.
+    LoadKeyFromDirectory(keyring_id, "fsv_system_", "/system/etc/security/fsverity");
+    LoadKeyFromDirectory(keyring_id, "fsv_product_", "/product/etc/security/fsverity");
+}
+
+int main(int argc, const char** argv) {
+    if (argc < 2) {
+        LOG(ERROR) << "Not enough arguments";
+        return -1;
+    }
+
+    key_serial_t keyring_id = android::GetKeyringId(".fs-verity");
+    if (keyring_id < 0) {
+        // This is expected on newer kernels.  See comment at the beginning of this file.
+        LOG(DEBUG) << "no initialization required";
+        return 0;
+    }
+
+    const std::string_view command = argv[1];
+
+    if (command == "--load-verified-keys") {
+        LoadKeyFromVerifiedPartitions(keyring_id);
+    } else {
+        LOG(ERROR) << "Unknown argument(s).";
+        return -1;
+    }
+
+    return 0;
+}