/**
 * 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/mount.h>
#include <linux/pagemap.h>
#include <linux/security.h>
#include <linux/compat.h>
#include <linux/fs_stack.h>
#include <linux/smp_lock.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)
{
        int rc;
        struct dentry *lower_dentry;
        struct vfsmount *lower_vfsmount;
        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) {
                lower_dentry = ecryptfs_dentry_to_lower(file->f_path.dentry);
                lower_vfsmount = ecryptfs_dentry_to_lower_mnt(file->f_path.dentry);
                touch_atime(lower_vfsmount, lower_dentry);
        }
        return rc;
}

struct ecryptfs_getdents_callback {
        void *dirent;
        struct dentry *dentry;
        filldir_t filldir;
        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->dentry, 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;
        }
        rc = buf->filldir(buf->dirent, name, name_size, offset, ino, d_type);
        kfree(name);
        if (rc >= 0)
                buf->entries_written++;
out:
        return rc;
}

/**
 * ecryptfs_readdir
 * @file: The eCryptfs directory file
 * @dirent: Directory entry handle
 * @filldir: The filldir callback function
 */
static int ecryptfs_readdir(struct file *file, void *dirent, filldir_t filldir)
{
        int rc;
        struct file *lower_file;
        struct inode *inode;
        struct ecryptfs_getdents_callback buf;

        lower_file = ecryptfs_file_to_lower(file);
        lower_file->f_pos = file->f_pos;
        inode = file->f_path.dentry->d_inode;
        memset(&buf, 0, sizeof(buf));
        buf.dirent = dirent;
        buf.dentry = file->f_path.dentry;
        buf.filldir = filldir;
        buf.filldir_called = 0;
        buf.entries_written = 0;
        rc = vfs_readdir(lower_file, ecryptfs_filldir, (void *)&buf);
        file->f_pos = lower_file->f_pos;
        if (rc < 0)
                goto out;
        if (buf.filldir_called && !buf.entries_written)
                goto out;
        if (rc >= 0)
                fsstack_copy_attr_atime(inode,
                                        lower_file->f_path.dentry->d_inode);
out:
        return rc;
}

struct kmem_cache *ecryptfs_file_info_cache;

/**
 * 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 dentry *lower_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry);
        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;
        }
        lower_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry);
        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);
        if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_RDONLY)
            && !(file->f_flags & O_RDONLY)) {
                rc = -EPERM;
                printk(KERN_WARNING "%s: Lower persistent file is RO; eCryptfs "
                       "file must hence be opened RO\n", __func__);
                goto out;
        }
        if (!ecryptfs_inode_to_private(inode)->lower_file) {
                rc = ecryptfs_init_persistent_file(ecryptfs_dentry);
                if (rc) {
                        printk(KERN_ERR "%s: Error attempting to initialize "
                               "the persistent file for the dentry with name "
                               "[%s]; rc = [%d]\n", __func__,
                               ecryptfs_dentry->d_name.name, rc);
                        goto out;
                }
        }
        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;
        }
        mutex_lock(&crypt_stat->cs_mutex);
        if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)
            || !(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
                rc = ecryptfs_read_metadata(ecryptfs_dentry);
                if (rc) {
                        ecryptfs_printk(KERN_DEBUG,
                                        "Valid headers not found\n");
                        if (!(mount_crypt_stat->flags
                              & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED)) {
                                rc = -EIO;
                                printk(KERN_WARNING "Either the lower file "
                                       "is not in a valid eCryptfs format, "
                                       "or the key could not be retrieved. "
                                       "Plaintext passthrough mode is not "
                                       "enabled; returning -EIO\n");
                                mutex_unlock(&crypt_stat->cs_mutex);
                                goto out_free;
                        }
                        rc = 0;
                        crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
                        mutex_unlock(&crypt_stat->cs_mutex);
                        goto out;
                }
        }
        mutex_unlock(&crypt_stat->cs_mutex);
        ecryptfs_printk(KERN_DEBUG, "inode w/ addr = [0x%p], i_ino = [0x%.16x] "
                        "size: [0x%.16x]\n", inode, inode->i_ino,
                        i_size_read(inode));
        goto out;
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)
{
        int rc = 0;
        struct file *lower_file = NULL;

        lower_file = ecryptfs_file_to_lower(file);
        if (lower_file->f_op && lower_file->f_op->flush)
                rc = lower_file->f_op->flush(lower_file, td);
        return rc;
}

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

static int
ecryptfs_fsync(struct file *file, struct dentry *dentry, int datasync)
{
        return vfs_fsync(ecryptfs_file_to_lower(file),
                         ecryptfs_dentry_to_lower(dentry),
                         datasync);
}

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

        lock_kernel();
        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);
        unlock_kernel();
        return rc;
}

static int ecryptfs_ioctl(struct inode *inode, struct file *file,
                          unsigned int cmd, unsigned long arg);

const struct file_operations ecryptfs_dir_fops = {
        .readdir = ecryptfs_readdir,
        .ioctl = ecryptfs_ioctl,
        .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,
};

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,
        .readdir = ecryptfs_readdir,
        .ioctl = ecryptfs_ioctl,
        .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,
};

static int
ecryptfs_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
               unsigned long arg)
{
        int rc = 0;
        struct file *lower_file = NULL;

        if (ecryptfs_file_to_private(file))
                lower_file = ecryptfs_file_to_lower(file);
        if (lower_file && lower_file->f_op && lower_file->f_op->ioctl)
                rc = lower_file->f_op->ioctl(ecryptfs_inode_to_lower(inode),
                                             lower_file, cmd, arg);
        else
                rc = -ENOTTY;
        return rc;
}