/* request_key_auth.c: request key authorisation controlling key def
   *
   * Copyright (C) 2005 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.

   *
   * See Documentation/keys-request-key.txt

   */
  
  #include <linux/module.h>
  #include <linux/sched.h>
  #include <linux/err.h>
  #include <linux/seq_file.h>

  #include <linux/slab.h>

  #include <asm/uaccess.h>

  #include "internal.h"
  
  static int request_key_auth_instantiate(struct key *, const void *, size_t);
  static void request_key_auth_describe(const struct key *, struct seq_file *);

  static void request_key_auth_revoke(struct key *);

  static void request_key_auth_destroy(struct key *);

  static long request_key_auth_read(const struct key *, char __user *, size_t);

  
  /*
   * the request-key authorisation key type definition
   */
  struct key_type key_type_request_key_auth = {
  	.name		= ".request_key_auth",
  	.def_datalen	= sizeof(struct request_key_auth),
  	.instantiate	= request_key_auth_instantiate,
  	.describe	= request_key_auth_describe,

  	.revoke		= request_key_auth_revoke,

  	.destroy	= request_key_auth_destroy,

  	.read		= request_key_auth_read,

  };
  
  /*****************************************************************************/
  /*

   * instantiate a request-key authorisation key

   */
  static int request_key_auth_instantiate(struct key *key,
  					const void *data,
  					size_t datalen)
  {

  	key->payload.data = (struct request_key_auth *) data;
  	return 0;

  
  } /* end request_key_auth_instantiate() */
  
  /*****************************************************************************/
  /*

   * reading a request-key authorisation key retrieves the callout information

   */
  static void request_key_auth_describe(const struct key *key,
  				      struct seq_file *m)
  {
  	struct request_key_auth *rka = key->payload.data;
  
  	seq_puts(m, "key:");
  	seq_puts(m, key->description);

  	seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);

  
  } /* end request_key_auth_describe() */
  
  /*****************************************************************************/
  /*

   * read the callout_info data
   * - the key's semaphore is read-locked
   */
  static long request_key_auth_read(const struct key *key,
  				  char __user *buffer, size_t buflen)
  {
  	struct request_key_auth *rka = key->payload.data;
  	size_t datalen;
  	long ret;

  	datalen = rka->callout_len;

  	ret = datalen;
  
  	/* we can return the data as is */
  	if (buffer && buflen > 0) {
  		if (buflen > datalen)
  			buflen = datalen;
  
  		if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
  			ret = -EFAULT;
  	}
  
  	return ret;
  
  } /* end request_key_auth_read() */
  
  /*****************************************************************************/
  /*

   * handle revocation of an authorisation token key
   * - called with the key sem write-locked
   */
  static void request_key_auth_revoke(struct key *key)
  {
  	struct request_key_auth *rka = key->payload.data;
  
  	kenter("{%d}", key->serial);

  	if (rka->cred) {
  		put_cred(rka->cred);
  		rka->cred = NULL;

  	}
  
  } /* end request_key_auth_revoke() */
  
  /*****************************************************************************/
  /*

   * destroy an instantiation authorisation token key
   */
  static void request_key_auth_destroy(struct key *key)
  {
  	struct request_key_auth *rka = key->payload.data;
  
  	kenter("{%d}", key->serial);

  	if (rka->cred) {
  		put_cred(rka->cred);
  		rka->cred = NULL;

  	}

  	key_put(rka->target_key);

  	key_put(rka->dest_keyring);

  	kfree(rka->callout_info);

  	kfree(rka);

  
  } /* end request_key_auth_destroy() */
  
  /*****************************************************************************/
  /*

   * create an authorisation token for /sbin/request-key or whoever to gain
   * access to the caller's security data

   */

  struct key *request_key_auth_new(struct key *target, const void *callout_info,

  				 size_t callout_len, struct key *dest_keyring)

  {

  	struct request_key_auth *rka, *irka;

  	const struct cred *cred = current->cred;

  	struct key *authkey = NULL;

  	char desc[20];
  	int ret;
  
  	kenter("%d,", target->serial);

  	/* allocate a auth record */
  	rka = kmalloc(sizeof(*rka), GFP_KERNEL);
  	if (!rka) {
  		kleave(" = -ENOMEM");
  		return ERR_PTR(-ENOMEM);
  	}

  	rka->callout_info = kmalloc(callout_len, GFP_KERNEL);

  	if (!rka->callout_info) {
  		kleave(" = -ENOMEM");
  		kfree(rka);
  		return ERR_PTR(-ENOMEM);
  	}

  	/* see if the calling process is already servicing the key request of
  	 * another process */

  	if (cred->request_key_auth) {

  		/* it is - use that instantiation context here too */

  		down_read(&cred->request_key_auth->sem);

  
  		/* if the auth key has been revoked, then the key we're
  		 * servicing is already instantiated */

  		if (test_bit(KEY_FLAG_REVOKED, &cred->request_key_auth->flags))

  			goto auth_key_revoked;

  		irka = cred->request_key_auth->payload.data;
  		rka->cred = get_cred(irka->cred);

  		rka->pid = irka->pid;

  		up_read(&cred->request_key_auth->sem);

  	}

  	else {
  		/* it isn't - use this process as the context */

  		rka->cred = get_cred(cred);

  		rka->pid = current->pid;
  	}
  
  	rka->target_key = key_get(target);

  	rka->dest_keyring = key_get(dest_keyring);

  	memcpy(rka->callout_info, callout_info, callout_len);
  	rka->callout_len = callout_len;

  
  	/* allocate the auth key */
  	sprintf(desc, "%x", target->serial);

  	authkey = key_alloc(&key_type_request_key_auth, desc,

  			    cred->fsuid, cred->fsgid, cred,

  			    KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |

  			    KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA);

  	if (IS_ERR(authkey)) {
  		ret = PTR_ERR(authkey);
  		goto error_alloc;

  	}

  	/* construct the auth key */

  	ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
  	if (ret < 0)
  		goto error_inst;

  	kleave(" = {%d,%d}", authkey->serial, atomic_read(&authkey->usage));

  	return authkey;

  auth_key_revoked:

  	up_read(&cred->request_key_auth->sem);

  	kfree(rka->callout_info);

  	kfree(rka);
  	kleave("= -EKEYREVOKED");
  	return ERR_PTR(-EKEYREVOKED);

  error_inst:
  	key_revoke(authkey);
  	key_put(authkey);
  error_alloc:
  	key_put(rka->target_key);

  	key_put(rka->dest_keyring);

  	kfree(rka->callout_info);

  	kfree(rka);
  	kleave("= %d", ret);
  	return ERR_PTR(ret);

  
  } /* end request_key_auth_new() */
  
  /*****************************************************************************/
  /*

   * see if an authorisation key is associated with a particular key
   */
  static int key_get_instantiation_authkey_match(const struct key *key,
  					       const void *_id)
  {
  	struct request_key_auth *rka = key->payload.data;
  	key_serial_t id = (key_serial_t)(unsigned long) _id;
  
  	return rka->target_key->serial == id;
  
  } /* end key_get_instantiation_authkey_match() */
  
  /*****************************************************************************/
  /*

   * get the authorisation key for instantiation of a specific key if attached to
   * the current process's keyrings
   * - this key is inserted into a keyring and that is set as /sbin/request-key's
   *   session keyring
   * - a target_id of zero specifies any valid token
   */
  struct key *key_get_instantiation_authkey(key_serial_t target_id)
  {

  	const struct cred *cred = current_cred();

  	struct key *authkey;
  	key_ref_t authkey_ref;
  
  	authkey_ref = search_process_keyrings(
  		&key_type_request_key_auth,
  		(void *) (unsigned long) target_id,
  		key_get_instantiation_authkey_match,

  		cred);

  
  	if (IS_ERR(authkey_ref)) {

  		authkey = ERR_CAST(authkey_ref);

  		goto error;
  	}

  	authkey = key_ref_to_ptr(authkey_ref);
  	if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
  		key_put(authkey);
  		authkey = ERR_PTR(-EKEYREVOKED);
  	}

  error:
  	return authkey;

  
  } /* end key_get_instantiation_authkey() */