/**
 * eCryptfs: Linux filesystem encryption layer
 *
 * Copyright (C) 1997-2004 Erez Zadok
 * Copyright (C) 2001-2004 Stony Brook University
 * Copyright (C) 2004-2007 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
 *              Michael C. Thompson <mcthomps@us.ibm.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.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */

#include <linux/file.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/security.h>
#include <linux/compat.h>
#include <linux/fs_stack.h>
#include <linux/aio.h>
#include "ecryptfs_kernel.h"

/**
 * ecryptfs_read_update_atime
 *
 * generic_file_read updates the atime of upper layer inode.  But, it
 * doesn't give us a chance to update the atime of the lower layer
 * inode.  This function is a wrapper to generic_file_read.  It
 * updates the atime of the lower level inode if generic_file_read
 * returns without any errors. This is to be used only for file reads.
 * The function to be used for directory reads is ecryptfs_read.
 */
static ssize_t ecryptfs_read_update_atime(struct kiocb *iocb,
                                const struct iovec *iov,
                                unsigned long nr_segs, loff_t pos)
{
        ssize_t rc;
        struct path *path;
        struct file *file = iocb->ki_filp;

        rc = generic_file_aio_read(iocb, iov, nr_segs, pos);
        /*
         * Even though this is a async interface, we need to wait
         * for IO to finish to update atime
         */
        if (-EIOCBQUEUED == rc)
                rc = wait_on_sync_kiocb(iocb);
        if (rc >= 0) {
                path = ecryptfs_dentry_to_lower_path(file->f_path.dentry);
                touch_atime(path);
        }
        return rc;
}

struct ecryptfs_getdents_callback {
        struct dir_context ctx;
        struct dir_context *caller;
        struct super_block *sb;
        int filldir_called;
        int entries_written;
};

/* Inspired by generic filldir in fs/readdir.c */
static int
ecryptfs_filldir(void *dirent, const char *lower_name, int lower_namelen,
                 loff_t offset, u64 ino, unsigned int d_type)
{
        struct ecryptfs_getdents_callback *buf =
            (struct ecryptfs_getdents_callback *)dirent;
        size_t name_size;
        char *name;
        int rc;

        buf->filldir_called++;
        rc = ecryptfs_decode_and_decrypt_filename(&name, &name_size,
                                                  buf->sb, lower_name,
                                                  lower_namelen);
        if (rc) {
                printk(KERN_ERR "%s: Error attempting to decode and decrypt "
                       "filename [%s]; rc = [%d]\n", __func__, lower_name,
                       rc);
                goto out;
        }
        buf->caller->pos = buf->ctx.pos;
        rc = !dir_emit(buf->caller, name, name_size, ino, d_type);
        kfree(name);
        if (!rc)
                buf->entries_written++;
out:
        return rc;
}

/**
 * ecryptfs_readdir
 * @file: The eCryptfs directory file
 * @ctx: The actor to feed the entries to
 */
static int ecryptfs_readdir(struct file *file, struct dir_context *ctx)
{
        int rc;
        struct file *lower_file;
        struct inode *inode = file_inode(file);
        struct ecryptfs_getdents_callback buf = {
                .ctx.actor = ecryptfs_filldir,
                .caller = ctx,
                .sb = inode->i_sb,
        };
        lower_file = ecryptfs_file_to_lower(file);
        lower_file->f_pos = ctx->pos;
        rc = iterate_dir(lower_file, &buf.ctx);
        ctx->pos = buf.ctx.pos;
        if (rc < 0)
                goto out;
        if (buf.filldir_called && !buf.entries_written)
                goto out;
        if (rc >= 0)
                fsstack_copy_attr_atime(inode,
                                        file_inode(lower_file));
out:
        return rc;
}

struct kmem_cache *ecryptfs_file_info_cache;

static int read_or_initialize_metadata(struct dentry *dentry)
{
        struct inode *inode = dentry->d_inode;
        struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
        struct ecryptfs_crypt_stat *crypt_stat;
        int rc;

        crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
        mount_crypt_stat = &ecryptfs_superblock_to_private(
                                                inode->i_sb)->mount_crypt_stat;
        mutex_lock(&crypt_stat->cs_mutex);

        if (crypt_stat->flags & ECRYPTFS_POLICY_APPLIED &&
            crypt_stat->flags & ECRYPTFS_KEY_VALID) {
                rc = 0;
                goto out;
        }

        rc = ecryptfs_read_metadata(dentry);
        if (!rc)
                goto out;

        if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED) {
                crypt_stat->flags &= ~(ECRYPTFS_I_SIZE_INITIALIZED
                                       | ECRYPTFS_ENCRYPTED);
                rc = 0;
                goto out;
        }

        if (!(mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED) &&
            !i_size_read(ecryptfs_inode_to_lower(inode))) {
                rc = ecryptfs_initialize_file(dentry, inode);
                if (!rc)
                        goto out;
        }

        rc = -EIO;
out:
        mutex_unlock(&crypt_stat->cs_mutex);
        return rc;
}

/**
 * ecryptfs_open
 * @inode: inode speciying file to open
 * @file: Structure to return filled in
 *
 * Opens the file specified by inode.
 *
 * Returns zero on success; non-zero otherwise
 */
static int ecryptfs_open(struct inode *inode, struct file *file)
{
        int rc = 0;
        struct ecryptfs_crypt_stat *crypt_stat = NULL;
        struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
        struct dentry *ecryptfs_dentry = file->f_path.dentry;
        /* Private value of ecryptfs_dentry allocated in
         * ecryptfs_lookup() */
        struct ecryptfs_file_info *file_info;

        mount_crypt_stat = &ecryptfs_superblock_to_private(
                ecryptfs_dentry->d_sb)->mount_crypt_stat;
        if ((mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
            && ((file->f_flags & O_WRONLY) || (file->f_flags & O_RDWR)
                || (file->f_flags & O_CREAT) || (file->f_flags & O_TRUNC)
                || (file->f_flags & O_APPEND))) {
                printk(KERN_WARNING "Mount has encrypted view enabled; "
                       "files may only be read\n");
                rc = -EPERM;
                goto out;
        }
        /* Released in ecryptfs_release or end of function if failure */
        file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
        ecryptfs_set_file_private(file, file_info);
        if (!file_info) {
                ecryptfs_printk(KERN_ERR,
                                "Error attempting to allocate memory\n");
                rc = -ENOMEM;
                goto out;
        }
        crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
        mutex_lock(&crypt_stat->cs_mutex);
        if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)) {
                ecryptfs_printk(KERN_DEBUG, "Setting flags for stat...\n");
                /* Policy code enabled in future release */
                crypt_stat->flags |= (ECRYPTFS_POLICY_APPLIED
                                      | ECRYPTFS_ENCRYPTED);
        }
        mutex_unlock(&crypt_stat->cs_mutex);
        rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
        if (rc) {
                printk(KERN_ERR "%s: Error attempting to initialize "
                        "the lower file for the dentry with name "
                        "[%s]; rc = [%d]\n", __func__,
                        ecryptfs_dentry->d_name.name, rc);
                goto out_free;
        }
        if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_ACCMODE)
            == O_RDONLY && (file->f_flags & O_ACCMODE) != O_RDONLY) {
                rc = -EPERM;
                printk(KERN_WARNING "%s: Lower file is RO; eCryptfs "
                       "file must hence be opened RO\n", __func__);
                goto out_put;
        }
        ecryptfs_set_file_lower(
                file, ecryptfs_inode_to_private(inode)->lower_file);
        if (S_ISDIR(ecryptfs_dentry->d_inode->i_mode)) {
                ecryptfs_printk(KERN_DEBUG, "This is a directory\n");
                mutex_lock(&crypt_stat->cs_mutex);
                crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
                mutex_unlock(&crypt_stat->cs_mutex);
                rc = 0;
                goto out;
        }
        rc = read_or_initialize_metadata(ecryptfs_dentry);
        if (rc)
                goto out_put;
        ecryptfs_printk(KERN_DEBUG, "inode w/ addr = [0x%p], i_ino = "
                        "[0x%.16lx] size: [0x%.16llx]\n", inode, inode->i_ino,
                        (unsigned long long)i_size_read(inode));
        goto out;
out_put:
        ecryptfs_put_lower_file(inode);
out_free:
        kmem_cache_free(ecryptfs_file_info_cache,
                        ecryptfs_file_to_private(file));
out:
        return rc;
}

static int ecryptfs_flush(struct file *file, fl_owner_t td)
{
        struct file *lower_file = ecryptfs_file_to_lower(file);

        if (lower_file->f_op && lower_file->f_op->flush) {
                filemap_write_and_wait(file->f_mapping);
                return lower_file->f_op->flush(lower_file, td);
        }

        return 0;
}

static int ecryptfs_release(struct inode *inode, struct file *file)
{
        ecryptfs_put_lower_file(inode);
        kmem_cache_free(ecryptfs_file_info_cache,
                        ecryptfs_file_to_private(file));
        return 0;
}

static int
ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
        int rc;

        rc = filemap_write_and_wait(file->f_mapping);
        if (rc)
                return rc;

        return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
}

static int ecryptfs_fasync(int fd, struct file *file, int flag)
{
        int rc = 0;
        struct file *lower_file = NULL;

        lower_file = ecryptfs_file_to_lower(file);
        if (lower_file->f_op && lower_file->f_op->fasync)
                rc = lower_file->f_op->fasync(fd, lower_file, flag);
        return rc;
}

static long
ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct file *lower_file = NULL;
        long rc = -ENOTTY;

        if (ecryptfs_file_to_private(file))
                lower_file = ecryptfs_file_to_lower(file);
        if (lower_file && lower_file->f_op && lower_file->f_op->unlocked_ioctl)
                rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
        return rc;
}

#ifdef CONFIG_COMPAT
static long
ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct file *lower_file = NULL;
        long rc = -ENOIOCTLCMD;

        if (ecryptfs_file_to_private(file))
                lower_file = ecryptfs_file_to_lower(file);
        if (lower_file && lower_file->f_op && lower_file->f_op->compat_ioctl)
                rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
        return rc;
}
#endif

const struct file_operations ecryptfs_dir_fops = {
        .iterate = ecryptfs_readdir,
        .read = generic_read_dir,
        .unlocked_ioctl = ecryptfs_unlocked_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = ecryptfs_compat_ioctl,
#endif
        .open = ecryptfs_open,
        .flush = ecryptfs_flush,
        .release = ecryptfs_release,
        .fsync = ecryptfs_fsync,
        .fasync = ecryptfs_fasync,
        .splice_read = generic_file_splice_read,
        .llseek = default_llseek,
};

const struct file_operations ecryptfs_main_fops = {
        .llseek = generic_file_llseek,
        .read = do_sync_read,
        .aio_read = ecryptfs_read_update_atime,
        .write = do_sync_write,
        .aio_write = generic_file_aio_write,
        .iterate = ecryptfs_readdir,
        .unlocked_ioctl = ecryptfs_unlocked_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = ecryptfs_compat_ioctl,
#endif
        .mmap = generic_file_mmap,
        .open = ecryptfs_open,
        .flush = ecryptfs_flush,
        .release = ecryptfs_release,
        .fsync = ecryptfs_fsync,
        .fasync = ecryptfs_fasync,
        .splice_read = generic_file_splice_read,
};