process_keys.c

linux 内核源代码

/* process_keys.c: management of a process's keyrings
 *
 * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([e-mail])
 *
 * 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/sched.h>
#include <linux/slab.h>
#include <linux/keyctl.h>
#include <linux/fs.h>
#include <linux/err.h>
#include <linux/mutex.h>
#include <asm/uaccess.h>
#include "internal.h"

/* session keyring create vs join semaphore */
static DEFINE_MUTEX(key_session_mutex);

/* the root user's tracking struct */
struct key_user root_key_user = {
	.usage		= ATOMIC_INIT(3),
	.cons_lock	= __MUTEX_INITIALIZER(root_key_user.cons_lock),
	.lock		= __SPIN_LOCK_UNLOCKED(root_key_user.lock),
	.nkeys		= ATOMIC_INIT(2),
	.nikeys		= ATOMIC_INIT(2),
	.uid		= 0,
};

/* the root user's UID keyring */
struct key root_user_keyring = {
	.usage		= ATOMIC_INIT(1),
	.serial		= 2,
	.type		= &key_type_keyring,
	.user		= &root_key_user,
	.sem		= __RWSEM_INITIALIZER(root_user_keyring.sem),
	.perm		= (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
	.flags		= 1 << KEY_FLAG_INSTANTIATED,
	.description	= "_uid.0",
#ifdef KEY_DEBUGGING
	.magic		= KEY_DEBUG_MAGIC,
#endif
};

/* the root user's default session keyring */
struct key root_session_keyring = {
	.usage		= ATOMIC_INIT(1),
	.serial		= 1,
	.type		= &key_type_keyring,
	.user		= &root_key_user,
	.sem		= __RWSEM_INITIALIZER(root_session_keyring.sem),
	.perm		= (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
	.flags		= 1 << KEY_FLAG_INSTANTIATED,
	.description	= "_uid_ses.0",
#ifdef KEY_DEBUGGING
	.magic		= KEY_DEBUG_MAGIC,
#endif
};

/*****************************************************************************/
/*
 * allocate the keyrings to be associated with a UID
 */
int alloc_uid_keyring(struct user_struct *user,
		      struct task_struct *ctx)
{
	struct key *uid_keyring, *session_keyring;
	char buf[20];
	int ret;

	/* concoct a default session keyring */
	sprintf(buf, "_uid_ses.%u", user->uid);

	session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx,
					KEY_ALLOC_IN_QUOTA, NULL);
	if (IS_ERR(session_keyring)) {
		ret = PTR_ERR(session_keyring);
		goto error;
	}

	/* and a UID specific keyring, pointed to by the default session
	 * keyring */
	sprintf(buf, "_uid.%u", user->uid);

	uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx,
				    KEY_ALLOC_IN_QUOTA, session_keyring);
	if (IS_ERR(uid_keyring)) {
		key_put(session_keyring);
		ret = PTR_ERR(uid_keyring);
		goto error;
	}

	/* install the keyrings */
	user->uid_keyring = uid_keyring;
	user->session_keyring = session_keyring;
	ret = 0;

error:
	return ret;

} /* end alloc_uid_keyring() */

/*****************************************************************************/
/*
 * deal with the UID changing
 */
void switch_uid_keyring(struct user_struct *new_user)
{
#if 0 /* do nothing for now */
	struct key *old;

	/* switch to the new user's session keyring if we were running under
	 * root's default session keyring */
	if (new_user->uid != 0 &&
	    current->session_keyring == &root_session_keyring
	    ) {
		atomic_inc(&new_user->session_keyring->usage);

		task_lock(current);
		old = current->session_keyring;
		current->session_keyring = new_user->session_keyring;
		task_unlock(current);

		key_put(old);
	}
#endif

} /* end switch_uid_keyring() */

/*****************************************************************************/
/*
 * install a fresh thread keyring, discarding the old one
 */
int install_thread_keyring(struct task_struct *tsk)
{
	struct key *keyring, *old;
	char buf[20];
	int ret;

	sprintf(buf, "_tid.%u", tsk->pid);

	keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk,
				KEY_ALLOC_QUOTA_OVERRUN, NULL);
	if (IS_ERR(keyring)) {
		ret = PTR_ERR(keyring);
		goto error;
	}

	task_lock(tsk);
	old = tsk->thread_keyring;
	tsk->thread_keyring = keyring;
	task_unlock(tsk);

	ret = 0;

	key_put(old);
error:
	return ret;

} /* end install_thread_keyring() */

/*****************************************************************************/
/*
 * make sure a process keyring is installed
 */
int install_process_keyring(struct task_struct *tsk)
{
	struct key *keyring;
	char buf[20];
	int ret;

	might_sleep();

	if (!tsk->signal->process_keyring) {
		sprintf(buf, "_pid.%u", tsk->tgid);

		keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk,
					KEY_ALLOC_QUOTA_OVERRUN, NULL);
		if (IS_ERR(keyring)) {
			ret = PTR_ERR(keyring);
			goto error;
		}

		/* attach keyring */
		spin_lock_irq(&tsk->sighand->siglock);
		if (!tsk->signal->process_keyring) {
			tsk->signal->process_keyring = keyring;
			keyring = NULL;
		}
		spin_unlock_irq(&tsk->sighand->siglock);

		key_put(keyring);
	}

	ret = 0;
error:
	return ret;

} /* end install_process_keyring() */

/*****************************************************************************/
/*
 * install a session keyring, discarding the old one
 * - if a keyring is not supplied, an empty one is invented
 */
static int install_session_keyring(struct task_struct *tsk,
				   struct key *keyring)
{
	unsigned long flags;
	struct key *old;
	char buf[20];

	might_sleep();

	/* create an empty session keyring */
	if (!keyring) {
		sprintf(buf, "_ses.%u", tsk->tgid);

		flags = KEY_ALLOC_QUOTA_OVERRUN;
		if (tsk->signal->session_keyring)
			flags = KEY_ALLOC_IN_QUOTA;

		keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk,
					flags, NULL);
		if (IS_ERR(keyring))
			return PTR_ERR(keyring);
	}
	else {
		atomic_inc(&keyring->usage);
	}

	/* install the keyring */
	spin_lock_irq(&tsk->sighand->siglock);
	old = tsk->signal->session_keyring;
	rcu_assign_pointer(tsk->signal->session_keyring, keyring);
	spin_unlock_irq(&tsk->sighand->siglock);

	/* we're using RCU on the pointer, but there's no point synchronising
	 * on it if it didn't previously point to anything */
	if (old) {
		synchronize_rcu();
		key_put(old);
	}

	return 0;

} /* end install_session_keyring() */

/*****************************************************************************/
/*
 * copy the keys in a thread group for fork without CLONE_THREAD
 */
int copy_thread_group_keys(struct task_struct *tsk)
{
	key_check(current->thread_group->session_keyring);
	key_check(current->thread_group->process_keyring);

	/* no process keyring yet */
	tsk->signal->process_keyring = NULL;

	/* same session keyring */
	rcu_read_lock();
	tsk->signal->session_keyring =
		key_get(rcu_dereference(current->signal->session_keyring));
	rcu_read_unlock();

	return 0;

} /* end copy_thread_group_keys() */

/*****************************************************************************/
/*
 * copy the keys for fork
 */
int copy_keys(unsigned long clone_flags, struct task_struct *tsk)
{
	key_check(tsk->thread_keyring);
	key_check(tsk->request_key_auth);

	/* no thread keyring yet */
	tsk->thread_keyring = NULL;

	/* copy the request_key() authorisation for this thread */
	key_get(tsk->request_key_auth);

	return 0;

} /* end copy_keys() */

/*****************************************************************************/
/*
 * dispose of thread group keys upon thread group destruction
 */
void exit_thread_group_keys(struct signal_struct *tg)
{
	key_put(tg->session_keyring);
	key_put(tg->process_keyring);

} /* end exit_thread_group_keys() */

/*****************************************************************************/
/*
 * dispose of per-thread keys upon thread exit
 */
void exit_keys(struct task_struct *tsk)
{
	key_put(tsk->thread_keyring);
	key_put(tsk->request_key_auth);

} /* end exit_keys() */

/*****************************************************************************/
/*
 * deal with execve()
 */
int exec_keys(struct task_struct *tsk)
{
	struct key *old;

	/* newly exec'd tasks don't get a thread keyring */
	task_lock(tsk);
	old = tsk->thread_keyring;
	tsk->thread_keyring = NULL;
	task_unlock(tsk);

	key_put(old);

	/* discard the process keyring from a newly exec'd task */
	spin_lock_irq(&tsk->sighand->siglock);
	old = tsk->signal->process_keyring;
	tsk->signal->process_keyring = NULL;
	spin_unlock_irq(&tsk->sighand->siglock);

	key_put(old);

	return 0;

} /* end exec_keys() */

/*****************************************************************************/
/*
 * deal with SUID programs
 * - we might want to make this invent a new session keyring
 */
int suid_keys(struct task_struct *tsk)
{
	return 0;

} /* end suid_keys() */

/*****************************************************************************/
/*
 * the filesystem user ID changed
 */
void key_fsuid_changed(struct task_struct *tsk)
{
	/* update the ownership of the thread keyring */
	if (tsk->thread_keyring) {
		down_write(&tsk->thread_keyring->sem);
		tsk->thread_keyring->uid = tsk->fsuid;
		up_write(&tsk->thread_keyring->sem);
	}

} /* end key_fsuid_changed() */

/*****************************************************************************/
/*
 * the filesystem group ID changed
 */
void key_fsgid_changed(struct task_struct *tsk)
{
	/* update the ownership of the thread keyring */
	if (tsk->thread_keyring) {
		down_write(&tsk->thread_keyring->sem);
		tsk->thread_keyring->gid = tsk->fsgid;
		up_write(&tsk->thread_keyring->sem);
	}

} /* end key_fsgid_changed() */

/*****************************************************************************/
/*