/* Request a key from userspace
   *
   * Copyright (C) 2004-2007 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/security/keys-request-key.txt
   */
  
  #include <linux/module.h>
  #include <linux/sched.h>
  #include <linux/kmod.h>
  #include <linux/err.h>
  #include <linux/keyctl.h>
  #include <linux/slab.h>
  #include "internal.h"
  
  #define key_negative_timeout	60	/* default timeout on a negative key's existence */
  
  /*
   * wait_on_bit() sleep function for uninterruptible waiting
   */
  static int key_wait_bit(void *flags)
  {
  	schedule();
  	return 0;
  }
  
  /*
   * wait_on_bit() sleep function for interruptible waiting
   */
  static int key_wait_bit_intr(void *flags)
  {
  	schedule();
  	return signal_pending(current) ? -ERESTARTSYS : 0;
  }
  
  /**
   * complete_request_key - Complete the construction of a key.
   * @cons: The key construction record.
   * @error: The success or failute of the construction.
   *
   * Complete the attempt to construct a key.  The key will be negated
   * if an error is indicated.  The authorisation key will be revoked
   * unconditionally.
   */
  void complete_request_key(struct key_construction *cons, int error)
  {
  	kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);
  
  	if (error < 0)
  		key_negate_and_link(cons->key, key_negative_timeout, NULL,
  				    cons->authkey);
  	else
  		key_revoke(cons->authkey);
  
  	key_put(cons->key);
  	key_put(cons->authkey);
  	kfree(cons);
  }
  EXPORT_SYMBOL(complete_request_key);
  
  /*
   * Initialise a usermode helper that is going to have a specific session
   * keyring.
   *
   * This is called in context of freshly forked kthread before kernel_execve(),
   * so we can simply install the desired session_keyring at this point.
   */
  static int umh_keys_init(struct subprocess_info *info, struct cred *cred)
  {
  	struct key *keyring = info->data;
  
  	return install_session_keyring_to_cred(cred, keyring);
  }
  
  /*
   * Clean up a usermode helper with session keyring.
   */
  static void umh_keys_cleanup(struct subprocess_info *info)
  {
  	struct key *keyring = info->data;
  	key_put(keyring);
  }
  
  /*
   * Call a usermode helper with a specific session keyring.
   */
  static int call_usermodehelper_keys(char *path, char **argv, char **envp,
  					struct key *session_keyring, int wait)
  {
  	struct subprocess_info *info;
  
  	info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL,
  					  umh_keys_init, umh_keys_cleanup,
  					  session_keyring);
  	if (!info)
  		return -ENOMEM;
  
  	key_get(session_keyring);
  	return call_usermodehelper_exec(info, wait);
  }
  
  /*
   * Request userspace finish the construction of a key
   * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
   */
  static int call_sbin_request_key(struct key_construction *cons,
  				 const char *op,
  				 void *aux)
  {
  	const struct cred *cred = current_cred();
  	key_serial_t prkey, sskey;
  	struct key *key = cons->key, *authkey = cons->authkey, *keyring,
  		*session;
  	char *argv[9], *envp[3], uid_str[12], gid_str[12];
  	char key_str[12], keyring_str[3][12];
  	char desc[20];
  	int ret, i;
  
  	kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
  
  	ret = install_user_keyrings();
  	if (ret < 0)
  		goto error_alloc;
  
  	/* allocate a new session keyring */
  	sprintf(desc, "_req.%u", key->serial);
  
  	cred = get_current_cred();
  	keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
  				KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
  				KEY_ALLOC_QUOTA_OVERRUN, NULL);
  	put_cred(cred);
  	if (IS_ERR(keyring)) {
  		ret = PTR_ERR(keyring);
  		goto error_alloc;
  	}
  
  	/* attach the auth key to the session keyring */
  	ret = key_link(keyring, authkey);
  	if (ret < 0)
  		goto error_link;
  
  	/* record the UID and GID */
  	sprintf(uid_str, "%d", from_kuid(&init_user_ns, cred->fsuid));
  	sprintf(gid_str, "%d", from_kgid(&init_user_ns, cred->fsgid));
  
  	/* we say which key is under construction */
  	sprintf(key_str, "%d", key->serial);
  
  	/* we specify the process's default keyrings */
  	sprintf(keyring_str[0], "%d",
  		cred->thread_keyring ? cred->thread_keyring->serial : 0);
  
  	prkey = 0;
  	if (cred->process_keyring)
  		prkey = cred->process_keyring->serial;
  	sprintf(keyring_str[1], "%d", prkey);
  
  	rcu_read_lock();
  	session = rcu_dereference(cred->session_keyring);
  	if (!session)
  		session = cred->user->session_keyring;
  	sskey = session->serial;
  	rcu_read_unlock();
  
  	sprintf(keyring_str[2], "%d", sskey);
  
  	/* set up a minimal environment */
  	i = 0;
  	envp[i++] = "HOME=/";
  	envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
  	envp[i] = NULL;
  
  	/* set up the argument list */
  	i = 0;
  	argv[i++] = "/sbin/request-key";
  	argv[i++] = (char *) op;
  	argv[i++] = key_str;
  	argv[i++] = uid_str;
  	argv[i++] = gid_str;
  	argv[i++] = keyring_str[0];
  	argv[i++] = keyring_str[1];
  	argv[i++] = keyring_str[2];
  	argv[i] = NULL;
  
  	/* do it */
  	ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
  				       UMH_WAIT_PROC);
  	kdebug("usermode -> 0x%x", ret);
  	if (ret >= 0) {
  		/* ret is the exit/wait code */
  		if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
  		    key_validate(key) < 0)
  			ret = -ENOKEY;
  		else
  			/* ignore any errors from userspace if the key was
  			 * instantiated */
  			ret = 0;
  	}
  
  error_link:
  	key_put(keyring);
  
  error_alloc:
  	complete_request_key(cons, ret);
  	kleave(" = %d", ret);
  	return ret;
  }
  
  /*
   * Call out to userspace for key construction.
   *
   * Program failure is ignored in favour of key status.
   */
  static int construct_key(struct key *key, const void *callout_info,
  			 size_t callout_len, void *aux,
  			 struct key *dest_keyring)
  {
  	struct key_construction *cons;
  	request_key_actor_t actor;
  	struct key *authkey;
  	int ret;
  
  	kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
  
  	cons = kmalloc(sizeof(*cons), GFP_KERNEL);
  	if (!cons)
  		return -ENOMEM;
  
  	/* allocate an authorisation key */
  	authkey = request_key_auth_new(key, callout_info, callout_len,
  				       dest_keyring);
  	if (IS_ERR(authkey)) {
  		kfree(cons);
  		ret = PTR_ERR(authkey);
  		authkey = NULL;
  	} else {
  		cons->authkey = key_get(authkey);
  		cons->key = key_get(key);
  
  		/* make the call */
  		actor = call_sbin_request_key;
  		if (key->type->request_key)
  			actor = key->type->request_key;
  
  		ret = actor(cons, "create", aux);
  
  		/* check that the actor called complete_request_key() prior to
  		 * returning an error */
  		WARN_ON(ret < 0 &&
  			!test_bit(KEY_FLAG_REVOKED, &authkey->flags));
  		key_put(authkey);
  	}
  
  	kleave(" = %d", ret);
  	return ret;
  }
  
  /*
   * Get the appropriate destination keyring for the request.
   *
   * The keyring selected is returned with an extra reference upon it which the
   * caller must release.
   */
  static void construct_get_dest_keyring(struct key **_dest_keyring)
  {
  	struct request_key_auth *rka;
  	const struct cred *cred = current_cred();
  	struct key *dest_keyring = *_dest_keyring, *authkey;
  
  	kenter("%p", dest_keyring);
  
  	/* find the appropriate keyring */
  	if (dest_keyring) {
  		/* the caller supplied one */
  		key_get(dest_keyring);
  	} else {
  		/* use a default keyring; falling through the cases until we
  		 * find one that we actually have */
  		switch (cred->jit_keyring) {
  		case KEY_REQKEY_DEFL_DEFAULT:
  		case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
  			if (cred->request_key_auth) {
  				authkey = cred->request_key_auth;
  				down_read(&authkey->sem);
  				rka = authkey->payload.data;
  				if (!test_bit(KEY_FLAG_REVOKED,
  					      &authkey->flags))
  					dest_keyring =
  						key_get(rka->dest_keyring);
  				up_read(&authkey->sem);
  				if (dest_keyring)
  					break;
  			}
  
  		case KEY_REQKEY_DEFL_THREAD_KEYRING:
  			dest_keyring = key_get(cred->thread_keyring);
  			if (dest_keyring)
  				break;
  
  		case KEY_REQKEY_DEFL_PROCESS_KEYRING:
  			dest_keyring = key_get(cred->process_keyring);
  			if (dest_keyring)
  				break;
  
  		case KEY_REQKEY_DEFL_SESSION_KEYRING:
  			rcu_read_lock();
  			dest_keyring = key_get(
  				rcu_dereference(cred->session_keyring));
  			rcu_read_unlock();
  
  			if (dest_keyring)
  				break;
  
  		case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
  			dest_keyring =
  				key_get(cred->user->session_keyring);
  			break;
  
  		case KEY_REQKEY_DEFL_USER_KEYRING:
  			dest_keyring = key_get(cred->user->uid_keyring);
  			break;
  
  		case KEY_REQKEY_DEFL_GROUP_KEYRING:
  		default:
  			BUG();
  		}
  	}
  
  	*_dest_keyring = dest_keyring;
  	kleave(" [dk %d]", key_serial(dest_keyring));
  	return;
  }
  
  /*
   * Allocate a new key in under-construction state and attempt to link it in to
   * the requested keyring.
   *
   * May return a key that's already under construction instead if there was a
   * race between two thread calling request_key().
   */
  static int construct_alloc_key(struct keyring_search_context *ctx,
  			       struct key *dest_keyring,
  			       unsigned long flags,
  			       struct key_user *user,
  			       struct key **_key)
  {
  	struct assoc_array_edit *edit;
  	struct key *key;
  	key_perm_t perm;
  	key_ref_t key_ref;
  	int ret;
  
  	kenter("%s,%s,,,",
  	       ctx->index_key.type->name, ctx->index_key.description);
  
  	*_key = NULL;
  	mutex_lock(&user->cons_lock);
  
  	perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
  	perm |= KEY_USR_VIEW;
  	if (ctx->index_key.type->read)
  		perm |= KEY_POS_READ;
  	if (ctx->index_key.type == &key_type_keyring ||
  	    ctx->index_key.type->update)
  		perm |= KEY_POS_WRITE;
  
  	key = key_alloc(ctx->index_key.type, ctx->index_key.description,
  			ctx->cred->fsuid, ctx->cred->fsgid, ctx->cred,
  			perm, flags);
  	if (IS_ERR(key))
  		goto alloc_failed;
  
  	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
  
  	if (dest_keyring) {
  		ret = __key_link_begin(dest_keyring, &ctx->index_key, &edit);
  		if (ret < 0)
  			goto link_prealloc_failed;
  	}
  
  	/* attach the key to the destination keyring under lock, but we do need
  	 * to do another check just in case someone beat us to it whilst we
  	 * waited for locks */
  	mutex_lock(&key_construction_mutex);
  
  	key_ref = search_process_keyrings(ctx);
  	if (!IS_ERR(key_ref))
  		goto key_already_present;
  
  	if (dest_keyring)
  		__key_link(key, &edit);
  
  	mutex_unlock(&key_construction_mutex);
  	if (dest_keyring)
  		__key_link_end(dest_keyring, &ctx->index_key, edit);
  	mutex_unlock(&user->cons_lock);
  	*_key = key;
  	kleave(" = 0 [%d]", key_serial(key));
  	return 0;
  
  	/* the key is now present - we tell the caller that we found it by
  	 * returning -EINPROGRESS  */
  key_already_present:
  	key_put(key);
  	mutex_unlock(&key_construction_mutex);
  	key = key_ref_to_ptr(key_ref);
  	if (dest_keyring) {
  		ret = __key_link_check_live_key(dest_keyring, key);
  		if (ret == 0)
  			__key_link(key, &edit);
  		__key_link_end(dest_keyring, &ctx->index_key, edit);
  		if (ret < 0)
  			goto link_check_failed;
  	}
  	mutex_unlock(&user->cons_lock);
  	*_key = key;
  	kleave(" = -EINPROGRESS [%d]", key_serial(key));
  	return -EINPROGRESS;
  
  link_check_failed:
  	mutex_unlock(&user->cons_lock);
  	key_put(key);
  	kleave(" = %d [linkcheck]", ret);
  	return ret;
  
  link_prealloc_failed:
  	mutex_unlock(&user->cons_lock);
  	kleave(" = %d [prelink]", ret);
  	return ret;
  
  alloc_failed:
  	mutex_unlock(&user->cons_lock);
  	kleave(" = %ld", PTR_ERR(key));
  	return PTR_ERR(key);
  }
  
  /*
   * Commence key construction.
   */
  static struct key *construct_key_and_link(struct keyring_search_context *ctx,
  					  const char *callout_info,
  					  size_t callout_len,
  					  void *aux,
  					  struct key *dest_keyring,
  					  unsigned long flags)
  {
  	struct key_user *user;
  	struct key *key;
  	int ret;
  
  	kenter("");
  
  	user = key_user_lookup(current_fsuid());
  	if (!user)
  		return ERR_PTR(-ENOMEM);
  
  	construct_get_dest_keyring(&dest_keyring);
  
  	ret = construct_alloc_key(ctx, dest_keyring, flags, user, &key);
  	key_user_put(user);
  
  	if (ret == 0) {
  		ret = construct_key(key, callout_info, callout_len, aux,
  				    dest_keyring);
  		if (ret < 0) {
  			kdebug("cons failed");
  			goto construction_failed;
  		}
  	} else if (ret == -EINPROGRESS) {
  		ret = 0;
  	} else {
  		goto couldnt_alloc_key;
  	}
  
  	key_put(dest_keyring);
  	kleave(" = key %d", key_serial(key));
  	return key;
  
  construction_failed:
  	key_negate_and_link(key, key_negative_timeout, NULL, NULL);
  	key_put(key);
  couldnt_alloc_key:
  	key_put(dest_keyring);
  	kleave(" = %d", ret);
  	return ERR_PTR(ret);
  }
  
  /**
   * request_key_and_link - Request a key and cache it in a keyring.
   * @type: The type of key we want.
   * @description: The searchable description of the key.
   * @callout_info: The data to pass to the instantiation upcall (or NULL).
   * @callout_len: The length of callout_info.
   * @aux: Auxiliary data for the upcall.
   * @dest_keyring: Where to cache the key.
   * @flags: Flags to key_alloc().
   *
   * A key matching the specified criteria is searched for in the process's
   * keyrings and returned with its usage count incremented if found.  Otherwise,
   * if callout_info is not NULL, a key will be allocated and some service
   * (probably in userspace) will be asked to instantiate it.
   *
   * If successfully found or created, the key will be linked to the destination
   * keyring if one is provided.
   *
   * Returns a pointer to the key if successful; -EACCES, -ENOKEY, -EKEYREVOKED
   * or -EKEYEXPIRED if an inaccessible, negative, revoked or expired key was
   * found; -ENOKEY if no key was found and no @callout_info was given; -EDQUOT
   * if insufficient key quota was available to create a new key; or -ENOMEM if
   * insufficient memory was available.
   *
   * If the returned key was created, then it may still be under construction,
   * and wait_for_key_construction() should be used to wait for that to complete.
   */
  struct key *request_key_and_link(struct key_type *type,
  				 const char *description,
  				 const void *callout_info,
  				 size_t callout_len,
  				 void *aux,
  				 struct key *dest_keyring,
  				 unsigned long flags)
  {
  	struct keyring_search_context ctx = {
  		.index_key.type		= type,
  		.index_key.description	= description,
  		.cred			= current_cred(),
  		.match			= type->match,
  		.match_data		= description,
  		.flags			= KEYRING_SEARCH_LOOKUP_DIRECT,
  	};
  	struct key *key;
  	key_ref_t key_ref;
  	int ret;
  
  	kenter("%s,%s,%p,%zu,%p,%p,%lx",
  	       ctx.index_key.type->name, ctx.index_key.description,
  	       callout_info, callout_len, aux, dest_keyring, flags);
  
  	/* search all the process keyrings for a key */
  	key_ref = search_process_keyrings(&ctx);
  
  	if (!IS_ERR(key_ref)) {
  		key = key_ref_to_ptr(key_ref);
  		if (dest_keyring) {
  			construct_get_dest_keyring(&dest_keyring);
  			ret = key_link(dest_keyring, key);
  			key_put(dest_keyring);
  			if (ret < 0) {
  				key_put(key);
  				key = ERR_PTR(ret);
  				goto error;
  			}
  		}
  	} else if (PTR_ERR(key_ref) != -EAGAIN) {
  		key = ERR_CAST(key_ref);
  	} else  {
  		/* the search failed, but the keyrings were searchable, so we
  		 * should consult userspace if we can */
  		key = ERR_PTR(-ENOKEY);
  		if (!callout_info)
  			goto error;
  
  		key = construct_key_and_link(&ctx, callout_info, callout_len,
  					     aux, dest_keyring, flags);
  	}
  
  error:
  	kleave(" = %p", key);
  	return key;
  }
  
  /**
   * wait_for_key_construction - Wait for construction of a key to complete
   * @key: The key being waited for.
   * @intr: Whether to wait interruptibly.
   *
   * Wait for a key to finish being constructed.
   *
   * Returns 0 if successful; -ERESTARTSYS if the wait was interrupted; -ENOKEY
   * if the key was negated; or -EKEYREVOKED or -EKEYEXPIRED if the key was
   * revoked or expired.
   */
  int wait_for_key_construction(struct key *key, bool intr)
  {
  	int ret;
  
  	ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
  			  intr ? key_wait_bit_intr : key_wait_bit,
  			  intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
  	if (ret < 0)
  		return ret;
  	if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
  		smp_rmb();
  		return key->type_data.reject_error;
  	}
  	return key_validate(key);
  }
  EXPORT_SYMBOL(wait_for_key_construction);
  
  /**
   * request_key - Request a key and wait for construction
   * @type: Type of key.
   * @description: The searchable description of the key.
   * @callout_info: The data to pass to the instantiation upcall (or NULL).
   *
   * As for request_key_and_link() except that it does not add the returned key
   * to a keyring if found, new keys are always allocated in the user's quota,
   * the callout_info must be a NUL-terminated string and no auxiliary data can
   * be passed.
   *
   * Furthermore, it then works as wait_for_key_construction() to wait for the
   * completion of keys undergoing construction with a non-interruptible wait.
   */
  struct key *request_key(struct key_type *type,
  			const char *description,
  			const char *callout_info)
  {
  	struct key *key;
  	size_t callout_len = 0;
  	int ret;
  
  	if (callout_info)
  		callout_len = strlen(callout_info);
  	key = request_key_and_link(type, description, callout_info, callout_len,
  				   NULL, NULL, KEY_ALLOC_IN_QUOTA);
  	if (!IS_ERR(key)) {
  		ret = wait_for_key_construction(key, false);
  		if (ret < 0) {
  			key_put(key);
  			return ERR_PTR(ret);
  		}
  	}
  	return key;
  }
  EXPORT_SYMBOL(request_key);
  
  /**
   * request_key_with_auxdata - Request a key with auxiliary data for the upcaller
   * @type: The type of key we want.
   * @description: The searchable description of the key.
   * @callout_info: The data to pass to the instantiation upcall (or NULL).
   * @callout_len: The length of callout_info.
   * @aux: Auxiliary data for the upcall.
   *
   * As for request_key_and_link() except that it does not add the returned key
   * to a keyring if found and new keys are always allocated in the user's quota.
   *
   * Furthermore, it then works as wait_for_key_construction() to wait for the
   * completion of keys undergoing construction with a non-interruptible wait.
   */
  struct key *request_key_with_auxdata(struct key_type *type,
  				     const char *description,
  				     const void *callout_info,
  				     size_t callout_len,
  				     void *aux)
  {
  	struct key *key;
  	int ret;
  
  	key = request_key_and_link(type, description, callout_info, callout_len,
  				   aux, NULL, KEY_ALLOC_IN_QUOTA);
  	if (!IS_ERR(key)) {
  		ret = wait_for_key_construction(key, false);
  		if (ret < 0) {
  			key_put(key);
  			return ERR_PTR(ret);
  		}
  	}
  	return key;
  }
  EXPORT_SYMBOL(request_key_with_auxdata);
  
  /*
   * request_key_async - Request a key (allow async construction)
   * @type: Type of key.
   * @description: The searchable description of the key.
   * @callout_info: The data to pass to the instantiation upcall (or NULL).
   * @callout_len: The length of callout_info.
   *
   * As for request_key_and_link() except that it does not add the returned key
   * to a keyring if found, new keys are always allocated in the user's quota and
   * no auxiliary data can be passed.
   *
   * The caller should call wait_for_key_construction() to wait for the
   * completion of the returned key if it is still undergoing construction.
   */
  struct key *request_key_async(struct key_type *type,
  			      const char *description,
  			      const void *callout_info,
  			      size_t callout_len)
  {
  	return request_key_and_link(type, description, callout_info,
  				    callout_len, NULL, NULL,
  				    KEY_ALLOC_IN_QUOTA);
  }
  EXPORT_SYMBOL(request_key_async);
  
  /*
   * request a key with auxiliary data for the upcaller (allow async construction)
   * @type: Type of key.
   * @description: The searchable description of the key.
   * @callout_info: The data to pass to the instantiation upcall (or NULL).
   * @callout_len: The length of callout_info.
   * @aux: Auxiliary data for the upcall.
   *
   * As for request_key_and_link() except that it does not add the returned key
   * to a keyring if found and new keys are always allocated in the user's quota.
   *
   * The caller should call wait_for_key_construction() to wait for the
   * completion of the returned key if it is still undergoing construction.
   */
  struct key *request_key_async_with_auxdata(struct key_type *type,
  					   const char *description,
  					   const void *callout_info,
  					   size_t callout_len,
  					   void *aux)
  {
  	return request_key_and_link(type, description, callout_info,
  				    callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
  }
  EXPORT_SYMBOL(request_key_async_with_auxdata);