Add a tool to add keys to keyring.

This CL adds a binary to load keys to a keyring.

Bug: 112038861
Test: mini-keyctl -k .fsverity -c PATH_CONTAINER_CERTS
Test: cat /proc/keys and find the newly added keys
Change-Id: Iead68618ea194e9412616c5c6cff885e3cf78520

libkeyutils/Android.bp

@@ -16,3 +16,16 @@ cc_test {
     srcs: ["keyutils_test.cpp"],
     test_suites: ["device-tests"],
 }
+
+cc_binary {
+    name: "mini-keyctl",
+    srcs: ["mini_keyctl.cpp"],
+
+    shared_libs: [
+        "libbase",
+        "libkeyutils",
+        "liblog",
+    ],
+
+    cflags: ["-Werror", "-Wall", "-Wextra"],
+}

libkeyutils/include/keyutils.h

@@ -51,6 +51,10 @@ long keyctl_setperm(key_serial_t id, int permissions);
 
 long keyctl_unlink(key_serial_t key, key_serial_t keyring);
 
+long keyctl_restrict_keyring(key_serial_t keyring, const char* type, const char* restriction);
+
+long keyctl_get_security(key_serial_t key, char* buffer, size_t buflen);
+
 __END_DECLS
 
 #endif

libkeyutils/keyutils.cpp

@@ -69,3 +69,11 @@ long keyctl_setperm(key_serial_t id, int permissions) {
 long keyctl_unlink(key_serial_t key, key_serial_t keyring) {
   return keyctl(KEYCTL_UNLINK, key, keyring);
 }
+
+long keyctl_restrict_keyring(key_serial_t keyring, const char* type, const char* restriction) {
+  return keyctl(KEYCTL_RESTRICT_KEYRING, keyring, type, restriction);
+}
+
+long keyctl_get_security(key_serial_t id, char* buffer, size_t buflen) {
+  return keyctl(KEYCTL_GET_SECURITY, id, buffer, buflen);
+}

libkeyutils/mini_keyctl.cpp

@@ -0,0 +1,176 @@
+/*
+ * 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.
+ */
+
+/*
+ * A tool loads keys to keyring.
+ */
+
+#include <dirent.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <fstream>
+#include <iostream>
+#include <iterator>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/properties.h>
+#include <android-base/strings.h>
+#include <keyutils.h>
+
+static constexpr int kMaxCertSize = 4096;
+
+// Add all the certs from directory path to keyring with keyring_id. Returns the number of keys
+// added.
+int AddKeys(const std::string& path, const key_serial_t keyring_id, const std::string& keyring_desc,
+            int start_index) {
+  std::unique_ptr<DIR, int (*)(DIR*)> dir(opendir(path.c_str()), closedir);
+  if (!dir) {
+    PLOG(WARNING) << "Failed to open directory " << path;
+    return 0;
+  }
+  int keys_added = 0;
+  struct dirent* dp;
+  while ((dp = readdir(dir.get())) != NULL) {
+    if (dp->d_type != DT_REG) {
+      continue;
+    }
+    std::string cert_path = path + "/" + dp->d_name;
+    std::string cert_buf;
+    if (!android::base::ReadFileToString(cert_path, &cert_buf, false /* follow_symlinks */)) {
+      LOG(ERROR) << "Failed to read " << cert_path;
+      continue;
+    }
+
+    if (cert_buf.size() > kMaxCertSize) {
+      LOG(ERROR) << "Certficate size too large: " << cert_path;
+      continue;
+    }
+
+    // Add key to keyring.
+    int key_desc_index = keys_added + start_index;
+    std::string key_desc = keyring_desc + "-key" + std::to_string(key_desc_index);
+    key_serial_t key =
+        add_key("asymmetric", key_desc.c_str(), &cert_buf[0], cert_buf.size(), keyring_id);
+    if (key < 0) {
+      PLOG(ERROR) << "Failed to add key to keyring: " << cert_path;
+      continue;
+    }
+    keys_added++;
+  }
+  return keys_added;
+}
+
+std::vector<std::string> SplitBySpace(const std::string& s) {
+  std::istringstream iss(s);
+  return std::vector<std::string>{std::istream_iterator<std::string>{iss},
+                                  std::istream_iterator<std::string>{}};
+}
+
+// Find the keyring id. Because request_key(2) syscall is not available or the key is
+// kernel keyring, the id is looked up from /proc/keys. The keyring description may contain other
+// information in the descritption section depending on the key type, only the first word in the
+// keyring description is used for searching.
+bool GetKeyringId(const std::string& keyring_desc, key_serial_t* keyring_id) {
+  if (!keyring_id) {
+    LOG(ERROR) << "keyring_id is null";
+    return false;
+  }
+
+  // Only keys allowed by SELinux rules will be shown here.
+  std::ifstream proc_keys_file("/proc/keys");
+  if (!proc_keys_file.is_open()) {
+    PLOG(ERROR) << "Failed to open /proc/keys";
+    return false;
+  }
+
+  std::string line;
+  while (getline(proc_keys_file, line)) {
+    std::vector<std::string> tokens = SplitBySpace(line);
+    if (tokens.size() < 9) {
+      continue;
+    }
+    std::string key_id = tokens[0];
+    std::string key_type = tokens[7];
+    // The key description may contain space.
+    std::string key_desc_prefix = tokens[8];
+    // The prefix has a ":" at the end
+    std::string key_desc_pattern = keyring_desc + ":";
+    if (key_type != "keyring" || key_desc_prefix != key_desc_pattern) {
+      continue;
+    }
+    *keyring_id = std::stoi(key_id, nullptr, 16);
+    return true;
+  }
+  return false;
+}
+
+static void Usage(int exit_code) {
+  fprintf(stderr, "usage: mini-keyctl -c PATHS -s DESCRIPTION\n");
+  fprintf(stderr, "\n");
+  fprintf(stderr, "-c, --cert_dirs     the certificate locations, separated by comma\n");
+  fprintf(stderr, "-k, --keyring       the keyring description\n");
+  _exit(exit_code);
+}
+
+int main(int argc, char** argv) {
+  if (argc < 5) Usage(1);
+
+  std::string arg_cert_dirs;
+  std::string arg_keyring_desc;
+
+  for (int i = 1; i < argc; i++) {
+    std::string option = argv[i];
+    if (option == "-c" || option == "--cert_dirs") {
+      if (i + 1 < argc) arg_cert_dirs = argv[++i];
+    } else if (option == "-k" || option == "--keyring") {
+      if (i + 1 < argc) arg_keyring_desc = argv[++i];
+    }
+  }
+
+  if (arg_cert_dirs.empty() || arg_keyring_desc.empty()) {
+    LOG(ERROR) << "Missing cert_dirs or keyring desc";
+    Usage(1);
+  }
+
+  // Get the keyring id
+  key_serial_t key_ring_id;
+  if (!GetKeyringId(arg_keyring_desc, &key_ring_id)) {
+    PLOG(ERROR) << "Can't find keyring with " << arg_keyring_desc;
+    return 1;
+  }
+
+  std::vector<std::string> cert_dirs = android::base::Split(arg_cert_dirs, ",");
+  int start_index = 0;
+  for (const auto& cert_dir : cert_dirs) {
+    int keys_added = AddKeys(cert_dir, key_ring_id, arg_keyring_desc, start_index);
+    start_index += keys_added;
+  }
+
+  // Prevent new keys to be added.
+  if (!android::base::GetBoolProperty("ro.debuggable", false) &&
+      keyctl_restrict_keyring(key_ring_id, nullptr, nullptr) < 0) {
+    PLOG(ERROR) << "Failed to restrict key ring " << arg_keyring_desc;
+    return 1;
+  }
+
+  return 0;
+}