/*
 * Squashfs - a compressed read only filesystem for Linux
 *
 * Copyright (c) 2010
 * Phillip Lougher <phillip@squashfs.org.uk>
 *
 * 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,
 * 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, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * xattr.c
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/xattr.h>
#include <linux/slab.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"

static const struct xattr_handler *squashfs_xattr_handler(int);

ssize_t squashfs_listxattr(struct dentry *d, char *buffer,
        size_t buffer_size)
{
        struct inode *inode = d_inode(d);
        struct super_block *sb = inode->i_sb;
        struct squashfs_sb_info *msblk = sb->s_fs_info;
        u64 start = SQUASHFS_XATTR_BLK(squashfs_i(inode)->xattr)
                                                 + msblk->xattr_table;
        int offset = SQUASHFS_XATTR_OFFSET(squashfs_i(inode)->xattr);
        int count = squashfs_i(inode)->xattr_count;
        size_t rest = buffer_size;
        int err;

        /* check that the file system has xattrs */
        if (msblk->xattr_id_table == NULL)
                return -EOPNOTSUPP;

        /* loop reading each xattr name */
        while (count--) {
                struct squashfs_xattr_entry entry;
                struct squashfs_xattr_val val;
                const struct xattr_handler *handler;
                int name_size;

                err = squashfs_read_metadata(sb, &entry, &start, &offset,
                                                        sizeof(entry));
                if (err < 0)
                        goto failed;

                name_size = le16_to_cpu(entry.size);
                handler = squashfs_xattr_handler(le16_to_cpu(entry.type));
                if (handler && (!handler->list || handler->list(d))) {
                        const char *prefix = handler->prefix ?: handler->name;
                        size_t prefix_size = strlen(prefix);

                        if (buffer) {
                                if (prefix_size + name_size + 1 > rest) {
                                        err = -ERANGE;
                                        goto failed;
                                }
                                memcpy(buffer, prefix, prefix_size);
                                buffer += prefix_size;
                        }
                        err = squashfs_read_metadata(sb, buffer, &start,
                                &offset, name_size);
                        if (err < 0)
                                goto failed;
                        if (buffer) {
                                buffer[name_size] = '\0';
                                buffer += name_size + 1;
                        }
                        rest -= prefix_size + name_size + 1;
                } else  {
                        /* no handler or insuffficient privileges, so skip */
                        err = squashfs_read_metadata(sb, NULL, &start,
                                &offset, name_size);
                        if (err < 0)
                                goto failed;
                }


                /* skip remaining xattr entry */
                err = squashfs_read_metadata(sb, &val, &start, &offset,
                                                sizeof(val));
                if (err < 0)
                        goto failed;

                err = squashfs_read_metadata(sb, NULL, &start, &offset,
                                                le32_to_cpu(val.vsize));
                if (err < 0)
                        goto failed;
        }
        err = buffer_size - rest;

failed:
        return err;
}


static int squashfs_xattr_get(struct inode *inode, int name_index,
        const char *name, void *buffer, size_t buffer_size)
{
        struct super_block *sb = inode->i_sb;
        struct squashfs_sb_info *msblk = sb->s_fs_info;
        u64 start = SQUASHFS_XATTR_BLK(squashfs_i(inode)->xattr)
                                                 + msblk->xattr_table;
        int offset = SQUASHFS_XATTR_OFFSET(squashfs_i(inode)->xattr);
        int count = squashfs_i(inode)->xattr_count;
        int name_len = strlen(name);
        int err, vsize;
        char *target = kmalloc(name_len, GFP_KERNEL);

        if (target == NULL)
                return  -ENOMEM;

        /* loop reading each xattr name */
        for (; count; count--) {
                struct squashfs_xattr_entry entry;
                struct squashfs_xattr_val val;
                int type, prefix, name_size;

                err = squashfs_read_metadata(sb, &entry, &start, &offset,
                                                        sizeof(entry));
                if (err < 0)
                        goto failed;

                name_size = le16_to_cpu(entry.size);
                type = le16_to_cpu(entry.type);
                prefix = type & SQUASHFS_XATTR_PREFIX_MASK;

                if (prefix == name_index && name_size == name_len)
                        err = squashfs_read_metadata(sb, target, &start,
                                                &offset, name_size);
                else
                        err = squashfs_read_metadata(sb, NULL, &start,
                                                &offset, name_size);
                if (err < 0)
                        goto failed;

                if (prefix == name_index && name_size == name_len &&
                                        strncmp(target, name, name_size) == 0) {
                        /* found xattr */
                        if (type & SQUASHFS_XATTR_VALUE_OOL) {
                                __le64 xattr_val;
                                u64 xattr;
                                /* val is a reference to the real location */
                                err = squashfs_read_metadata(sb, &val, &start,
                                                &offset, sizeof(val));
                                if (err < 0)
                                        goto failed;
                                err = squashfs_read_metadata(sb, &xattr_val,
                                        &start, &offset, sizeof(xattr_val));
                                if (err < 0)
                                        goto failed;
                                xattr = le64_to_cpu(xattr_val);
                                start = SQUASHFS_XATTR_BLK(xattr) +
                                                        msblk->xattr_table;
                                offset = SQUASHFS_XATTR_OFFSET(xattr);
                        }
                        /* read xattr value */
                        err = squashfs_read_metadata(sb, &val, &start, &offset,
                                                        sizeof(val));
                        if (err < 0)
                                goto failed;

                        vsize = le32_to_cpu(val.vsize);
                        if (buffer) {
                                if (vsize > buffer_size) {
                                        err = -ERANGE;
                                        goto failed;
                                }
                                err = squashfs_read_metadata(sb, buffer, &start,
                                         &offset, vsize);
                                if (err < 0)
                                        goto failed;
                        }
                        break;
                }

                /* no match, skip remaining xattr entry */
                err = squashfs_read_metadata(sb, &val, &start, &offset,
                                                        sizeof(val));
                if (err < 0)
                        goto failed;
                err = squashfs_read_metadata(sb, NULL, &start, &offset,
                                                le32_to_cpu(val.vsize));
                if (err < 0)
                        goto failed;
        }
        err = count ? vsize : -ENODATA;

failed:
        kfree(target);
        return err;
}


static int squashfs_xattr_handler_get(const struct xattr_handler *handler,
                                      struct dentry *unused,
                                      struct inode *inode,
                                      const char *name,
                                      void *buffer, size_t size)
{
        return squashfs_xattr_get(inode, handler->flags, name,
                buffer, size);
}

/*
 * User namespace support
 */
static const struct xattr_handler squashfs_xattr_user_handler = {
        .prefix = XATTR_USER_PREFIX,
        .flags  = SQUASHFS_XATTR_USER,
        .get    = squashfs_xattr_handler_get
};

/*
 * Trusted namespace support
 */
static bool squashfs_trusted_xattr_handler_list(struct dentry *d)
{
        return capable(CAP_SYS_ADMIN);
}

static const struct xattr_handler squashfs_xattr_trusted_handler = {
        .prefix = XATTR_TRUSTED_PREFIX,
        .flags  = SQUASHFS_XATTR_TRUSTED,
        .list   = squashfs_trusted_xattr_handler_list,
        .get    = squashfs_xattr_handler_get
};

/*
 * Security namespace support
 */
static const struct xattr_handler squashfs_xattr_security_handler = {
        .prefix = XATTR_SECURITY_PREFIX,
        .flags  = SQUASHFS_XATTR_SECURITY,
        .get    = squashfs_xattr_handler_get
};

static const struct xattr_handler *squashfs_xattr_handler(int type)
{
        if (type & ~(SQUASHFS_XATTR_PREFIX_MASK | SQUASHFS_XATTR_VALUE_OOL))
                /* ignore unrecognised type */
                return NULL;

        switch (type & SQUASHFS_XATTR_PREFIX_MASK) {
        case SQUASHFS_XATTR_USER:
                return &squashfs_xattr_user_handler;
        case SQUASHFS_XATTR_TRUSTED:
                return &squashfs_xattr_trusted_handler;
        case SQUASHFS_XATTR_SECURITY:
                return &squashfs_xattr_security_handler;
        default:
                /* ignore unrecognised type */
                return NULL;
        }
}

const struct xattr_handler *squashfs_xattr_handlers[] = {
        &squashfs_xattr_user_handler,
        &squashfs_xattr_trusted_handler,
        &squashfs_xattr_security_handler,
        NULL
};