--- /dev/null
+/* Large capacity key type
+ *
+ * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/seq_file.h>
+#include <linux/file.h>
+#include <linux/shmem_fs.h>
+#include <linux/err.h>
+#include <keys/user-type.h>
+#include <keys/big_key-type.h>
+
+MODULE_LICENSE("GPL");
+
+/*
+ * If the data is under this limit, there's no point creating a shm file to
+ * hold it as the permanently resident metadata for the shmem fs will be at
+ * least as large as the data.
+ */
+#define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry))
+
+/*
+ * big_key defined keys take an arbitrary string as the description and an
+ * arbitrary blob of data as the payload
+ */
+struct key_type key_type_big_key = {
+ .name = "big_key",
+ .def_lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
+ .instantiate = big_key_instantiate,
+ .match = user_match,
+ .revoke = big_key_revoke,
+ .destroy = big_key_destroy,
+ .describe = big_key_describe,
+ .read = big_key_read,
+};
+
+/*
+ * Instantiate a big key
+ */
+int big_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
+{
+ struct path *path = (struct path *)&key->payload.data2;
+ struct file *file;
+ ssize_t written;
+ size_t datalen = prep->datalen;
+ int ret;
+
+ ret = -EINVAL;
+ if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data)
+ goto error;
+
+ /* Set an arbitrary quota */
+ ret = key_payload_reserve(key, 16);
+ if (ret < 0)
+ goto error;
+
+ key->type_data.x[1] = datalen;
+
+ if (datalen > BIG_KEY_FILE_THRESHOLD) {
+ /* Create a shmem file to store the data in. This will permit the data
+ * to be swapped out if needed.
+ *
+ * TODO: Encrypt the stored data with a temporary key.
+ */
+ file = shmem_kernel_file_setup("", datalen, 0);
+ if (IS_ERR(file)) {
+ ret = PTR_ERR(file);
+ goto err_quota;
+ }
+
+ written = kernel_write(file, prep->data, prep->datalen, 0);
+ if (written != datalen) {
+ ret = written;
+ if (written >= 0)
+ ret = -ENOMEM;
+ goto err_fput;
+ }
+
+ /* Pin the mount and dentry to the key so that we can open it again
+ * later
+ */
+ *path = file->f_path;
+ path_get(path);
+ fput(file);
+ } else {
+ /* Just store the data in a buffer */
+ void *data = kmalloc(datalen, GFP_KERNEL);
+ if (!data) {
+ ret = -ENOMEM;
+ goto err_quota;
+ }
+
+ key->payload.data = memcpy(data, prep->data, prep->datalen);
+ }
+ return 0;
+
+err_fput:
+ fput(file);
+err_quota:
+ key_payload_reserve(key, 0);
+error:
+ return ret;
+}
+
+/*
+ * dispose of the links from a revoked keyring
+ * - called with the key sem write-locked
+ */
+void big_key_revoke(struct key *key)
+{
+ struct path *path = (struct path *)&key->payload.data2;
+
+ /* clear the quota */
+ key_payload_reserve(key, 0);
+ if (key_is_instantiated(key) && key->type_data.x[1] > BIG_KEY_FILE_THRESHOLD)
+ vfs_truncate(path, 0);
+}
+
+/*
+ * dispose of the data dangling from the corpse of a big_key key
+ */
+void big_key_destroy(struct key *key)
+{
+ if (key->type_data.x[1] > BIG_KEY_FILE_THRESHOLD) {
+ struct path *path = (struct path *)&key->payload.data2;
+ path_put(path);
+ path->mnt = NULL;
+ path->dentry = NULL;
+ } else {
+ kfree(key->payload.data);
+ key->payload.data = NULL;
+ }
+}
+
+/*
+ * describe the big_key key
+ */
+void big_key_describe(const struct key *key, struct seq_file *m)
+{
+ unsigned long datalen = key->type_data.x[1];
+
+ seq_puts(m, key->description);
+
+ if (key_is_instantiated(key))
+ seq_printf(m, ": %lu [%s]",
+ datalen,
+ datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff");
+}
+
+/*
+ * read the key data
+ * - the key's semaphore is read-locked
+ */
+long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
+{
+ unsigned long datalen = key->type_data.x[1];
+ long ret;
+
+ if (!buffer || buflen < datalen)
+ return datalen;
+
+ if (datalen > BIG_KEY_FILE_THRESHOLD) {
+ struct path *path = (struct path *)&key->payload.data2;
+ struct file *file;
+ loff_t pos;
+
+ file = dentry_open(path, O_RDONLY, current_cred());
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
+ pos = 0;
+ ret = vfs_read(file, buffer, datalen, &pos);
+ fput(file);
+ if (ret >= 0 && ret != datalen)
+ ret = -EIO;
+ } else {
+ ret = datalen;
+ if (copy_to_user(buffer, key->payload.data, datalen) != 0)
+ ret = -EFAULT;
+ }
+
+ return ret;
+}
+
+/*
+ * Module stuff
+ */
+static int __init big_key_init(void)
+{
+ return register_key_type(&key_type_big_key);
+}
+
+static void __exit big_key_cleanup(void)
+{
+ unregister_key_type(&key_type_big_key);
+}
+
+module_init(big_key_init);
+module_exit(big_key_cleanup);
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