/*
 * SPDX-License-Identifier: LGPL-2.0+
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <https://www.gnu.org/licenses/>.
 */

#include "config.h"

#include "otcore.h"

// This key is used by default if present in the initramfs to verify
// the signature on the target commit object.  When composefs is
// in use, the ostree commit metadata will contain the composefs image digest,
// which can be used to fully verify the target filesystem tree.
#define BINDING_KEYPATH "/etc/ostree/initramfs-root-binding.key"

static bool
proc_cmdline_has_key_starting_with (const char *cmdline, const char *key)
{
  for (const char *iter = cmdline; iter;)
    {
      if (g_str_has_prefix (iter, key))
        return true;

      iter = strchr (iter, ' ');
      if (iter == NULL)
        return false;

      iter += strspn (iter, " ");
    }

  return false;
}

// Parse a kernel cmdline to find the provided key.
// TODO: Deduplicate this with the kernel argument code from libostree.so
char *
otcore_find_proc_cmdline_key (const char *cmdline, const char *key)
{
  const size_t key_len = strlen (key);
  for (const char *iter = cmdline; iter;)
    {
      const char *next = strchr (iter, ' ');
      if (strncmp (iter, key, key_len) == 0 && iter[key_len] == '=')
        {
          const char *start = iter + key_len + 1;
          if (next)
            return strndup (start, next - start);

          return strdup (start);
        }

      if (next)
        next += strspn (next, " ");

      iter = next;
    }

  return NULL;
}

// Find the target OSTree root filesystem from parsing the provided kernel commandline.
// If none is found, @out_target will be set to NULL, and the function will return successfully.
//
// If invalid data is found, @error will be set.
gboolean
otcore_get_ostree_target (const char *cmdline, gboolean *is_aboot, char **out_target,
                          GError **error)
{
  g_assert (cmdline);
  g_assert (out_target && *out_target == NULL);
  static const char slot_a[] = "/ostree/root.a";
  static const char slot_b[] = "/ostree/root.b";

  // First, handle the Android boot case
  g_autofree char *slot_suffix = otcore_find_proc_cmdline_key (cmdline, "androidboot.slot_suffix");
  if (is_aboot)
    *is_aboot = false;

  if (slot_suffix)
    {
      if (is_aboot)
        *is_aboot = true;

      if (strcmp (slot_suffix, "_a") == 0)
        {
          *out_target = g_strdup (slot_a);
          return TRUE;
        }
      else if (strcmp (slot_suffix, "_b") == 0)
        {
          *out_target = g_strdup (slot_b);
          return TRUE;
        }
      return glnx_throw (error, "androidboot.slot_suffix invalid: %s", slot_suffix);
    }

  /* Non-A/B androidboot:
   * https://source.android.com/docs/core/ota/nonab
   */
  if (proc_cmdline_has_key_starting_with (cmdline, "androidboot."))
    {
      *out_target = g_strdup (slot_a);
      return TRUE;
    }

  // Otherwise, fall back to the default `ostree=` kernel cmdline
  *out_target = otcore_find_proc_cmdline_key (cmdline, "ostree");
  return TRUE;
}

// Load a config file; if it doesn't exist, we return an empty configuration.
// NULL will be returned if we caught an error.
GKeyFile *
otcore_load_config (int rootfs_fd, const char *filename, GError **error)
{
  // The path to the config file for this binary
  static const char *const config_roots[] = { "usr/lib", "etc" };
  g_autoptr (GKeyFile) ret = g_key_file_new ();

  for (guint i = 0; i < G_N_ELEMENTS (config_roots); i++)
    {
      glnx_autofd int fd = -1;
      g_autofree char *path = g_build_filename (config_roots[i], filename, NULL);
      if (!ot_openat_ignore_enoent (rootfs_fd, path, &fd, error))
        return NULL;
      /* If the config file doesn't exist, that's OK */
      if (fd == -1)
        continue;

      g_autofree char *buf = glnx_fd_readall_utf8 (fd, NULL, NULL, error);
      if (!buf)
        return NULL;
      if (!g_key_file_load_from_data (ret, buf, -1, 0, error))
        return NULL;
    }

  return g_steal_pointer (&ret);
}

void
otcore_free_composefs_config (ComposefsConfig *config)
{
  g_clear_pointer (&config->pubkeys, g_ptr_array_unref);
  g_free (config->signature_pubkey);
  g_free (config);
}

// Parse the [composefs] section of the prepare-root.conf.
ComposefsConfig *
otcore_load_composefs_config (GKeyFile *config, gboolean load_keys, GError **error)
{
  GLNX_AUTO_PREFIX_ERROR ("Loading composefs config", error);

  g_autoptr (ComposefsConfig) ret = g_new0 (ComposefsConfig, 1);

  g_autofree char *enabled = g_key_file_get_value (config, OTCORE_PREPARE_ROOT_COMPOSEFS_KEY,
                                                   OTCORE_PREPARE_ROOT_ENABLED_KEY, NULL);
  if (g_strcmp0 (enabled, "signed") == 0)
    {
      ret->enabled = OT_TRISTATE_YES;
      ret->is_signed = true;
    }
  else if (!ot_keyfile_get_tristate_with_default (config, OTCORE_PREPARE_ROOT_COMPOSEFS_KEY,
                                                  OTCORE_PREPARE_ROOT_ENABLED_KEY,
                                                  OT_TRISTATE_MAYBE, &ret->enabled, error))
    return NULL;

  // Look for a key - we default to the initramfs binding path.
  if (!ot_keyfile_get_value_with_default (config, OTCORE_PREPARE_ROOT_COMPOSEFS_KEY,
                                          OTCORE_PREPARE_ROOT_KEYPATH_KEY, BINDING_KEYPATH,
                                          &ret->signature_pubkey, error))
    return NULL;

  if (ret->is_signed && load_keys)
    {
      ret->pubkeys = g_ptr_array_new_with_free_func ((GDestroyNotify)g_bytes_unref);

      g_autofree char *pubkeys = NULL;
      gsize pubkeys_size;

      /* Load keys */

      if (!g_file_get_contents (ret->signature_pubkey, &pubkeys, &pubkeys_size, error))
        return glnx_prefix_error_null (error, "Reading public key file '%s'",
                                       ret->signature_pubkey);

      g_auto (GStrv) lines = g_strsplit (pubkeys, "\n", -1);
      for (char **iter = lines; *iter; iter++)
        {
          const char *line = *iter;
          if (!*line)
            continue;

          gsize pubkey_size;
          g_autofree guchar *pubkey = g_base64_decode (line, &pubkey_size);
          g_ptr_array_add (ret->pubkeys, g_bytes_new_take (g_steal_pointer (&pubkey), pubkey_size));
        }

      if (ret->pubkeys->len == 0)
        return glnx_null_throw (error, "public key file specified, but no public keys found");
    }

  return g_steal_pointer (&ret);
}
