/* user_defined.c: user defined key type
   *
   * Copyright (C) 2004 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 License
   * as published by the Free Software Foundation; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/seq_file.h>
  #include <linux/err.h>
  #include <keys/user-type.h>
  #include <asm/uaccess.h>
  #include "internal.h"
  
  static int logon_vet_description(const char *desc);
  
  /*
   * user defined keys take an arbitrary string as the description and an
   * arbitrary blob of data as the payload
   */
  struct key_type key_type_user = {
  	.name			= "user",
  	.def_lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
  	.instantiate		= user_instantiate,
  	.update			= user_update,
  	.match			= user_match,
  	.revoke			= user_revoke,
  	.destroy		= user_destroy,
  	.describe		= user_describe,
  	.read			= user_read,
  };
  
  EXPORT_SYMBOL_GPL(key_type_user);
  
  /*
   * This key type is essentially the same as key_type_user, but it does
   * not define a .read op. This is suitable for storing username and
   * password pairs in the keyring that you do not want to be readable
   * from userspace.
   */
  struct key_type key_type_logon = {
  	.name			= "logon",
  	.def_lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
  	.instantiate		= user_instantiate,
  	.update			= user_update,
  	.match			= user_match,
  	.revoke			= user_revoke,
  	.destroy		= user_destroy,
  	.describe		= user_describe,
  	.vet_description	= logon_vet_description,
  };
  EXPORT_SYMBOL_GPL(key_type_logon);
  
  /*
   * instantiate a user defined key
   */
  int user_instantiate(struct key *key, struct key_preparsed_payload *prep)
  {
  	struct user_key_payload *upayload;
  	size_t datalen = prep->datalen;
  	int ret;
  
  	ret = -EINVAL;
  	if (datalen <= 0 || datalen > 32767 || !prep->data)
  		goto error;
  
  	ret = key_payload_reserve(key, datalen);
  	if (ret < 0)
  		goto error;
  
  	ret = -ENOMEM;
  	upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  	if (!upayload)
  		goto error;
  
  	/* attach the data */
  	upayload->datalen = datalen;
  	memcpy(upayload->data, prep->data, datalen);
  	rcu_assign_keypointer(key, upayload);
  	ret = 0;
  
  error:
  	return ret;
  }
  
  EXPORT_SYMBOL_GPL(user_instantiate);
  
  /*
   * update a user defined key
   * - the key's semaphore is write-locked
   */
  int user_update(struct key *key, struct key_preparsed_payload *prep)
  {
  	struct user_key_payload *upayload, *zap;
  	size_t datalen = prep->datalen;
  	int ret;
  
  	ret = -EINVAL;
  	if (datalen <= 0 || datalen > 32767 || !prep->data)
  		goto error;
  
  	/* construct a replacement payload */
  	ret = -ENOMEM;
  	upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
  	if (!upayload)
  		goto error;
  
  	upayload->datalen = datalen;
  	memcpy(upayload->data, prep->data, datalen);
  
  	/* check the quota and attach the new data */
  	zap = upayload;
  
  	ret = key_payload_reserve(key, datalen);
  
  	if (ret == 0) {
  		/* attach the new data, displacing the old */
  		zap = key->payload.data;
  		rcu_assign_keypointer(key, upayload);
  		key->expiry = 0;
  	}
  
  	if (zap)
  		kfree_rcu(zap, rcu);
  
  error:
  	return ret;
  }
  
  EXPORT_SYMBOL_GPL(user_update);
  
  /*
   * match users on their name
   */
  int user_match(const struct key *key, const void *description)
  {
  	return strcmp(key->description, description) == 0;
  }
  
  EXPORT_SYMBOL_GPL(user_match);
  
  /*
   * dispose of the links from a revoked keyring
   * - called with the key sem write-locked
   */
  void user_revoke(struct key *key)
  {
  	struct user_key_payload *upayload = key->payload.data;
  
  	/* clear the quota */
  	key_payload_reserve(key, 0);
  
  	if (upayload) {
  		rcu_assign_keypointer(key, NULL);
  		kfree_rcu(upayload, rcu);
  	}
  }
  
  EXPORT_SYMBOL(user_revoke);
  
  /*
   * dispose of the data dangling from the corpse of a user key
   */
  void user_destroy(struct key *key)
  {
  	struct user_key_payload *upayload = key->payload.data;
  
  	kfree(upayload);
  }
  
  EXPORT_SYMBOL_GPL(user_destroy);
  
  /*
   * describe the user key
   */
  void user_describe(const struct key *key, struct seq_file *m)
  {
  	seq_puts(m, key->description);
  	if (key_is_instantiated(key))
  		seq_printf(m, ": %u", key->datalen);
  }
  
  EXPORT_SYMBOL_GPL(user_describe);
  
  /*
   * read the key data
   * - the key's semaphore is read-locked
   */
  long user_read(const struct key *key, char __user *buffer, size_t buflen)
  {
  	struct user_key_payload *upayload;
  	long ret;
  
  	upayload = rcu_dereference_key(key);
  	ret = upayload->datalen;
  
  	/* we can return the data as is */
  	if (buffer && buflen > 0) {
  		if (buflen > upayload->datalen)
  			buflen = upayload->datalen;
  
  		if (copy_to_user(buffer, upayload->data, buflen) != 0)
  			ret = -EFAULT;
  	}
  
  	return ret;
  }
  
  EXPORT_SYMBOL_GPL(user_read);
  
  /* Vet the description for a "logon" key */
  static int logon_vet_description(const char *desc)
  {
  	char *p;
  
  	/* require a "qualified" description string */
  	p = strchr(desc, ':');
  	if (!p)
  		return -EINVAL;
  
  	/* also reject description with ':' as first char */
  	if (p == desc)
  		return -EINVAL;
  
  	return 0;
  }