/**
   * 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 <mahalcro@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/fs.h>
  #include <linux/mount.h>
  #include <linux/pagemap.h>
  #include <linux/random.h>
  #include <linux/compiler.h>
  #include <linux/key.h>
  #include <linux/namei.h>
  #include <linux/crypto.h>
  #include <linux/file.h>
  #include <linux/scatterlist.h>

  #include <linux/slab.h>

  #include <asm/unaligned.h>

  #include "ecryptfs_kernel.h"
  
  static int
  ecryptfs_decrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
  			     struct page *dst_page, int dst_offset,
  			     struct page *src_page, int src_offset, int size,
  			     unsigned char *iv);
  static int
  ecryptfs_encrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
  			     struct page *dst_page, int dst_offset,
  			     struct page *src_page, int src_offset, int size,
  			     unsigned char *iv);
  
  /**
   * ecryptfs_to_hex
   * @dst: Buffer to take hex character representation of contents of
   *       src; must be at least of size (src_size * 2)
   * @src: Buffer to be converted to a hex string respresentation
   * @src_size: number of bytes to convert
   */
  void ecryptfs_to_hex(char *dst, char *src, size_t src_size)
  {
  	int x;
  
  	for (x = 0; x < src_size; x++)
  		sprintf(&dst[x * 2], "%.2x", (unsigned char)src[x]);
  }
  
  /**
   * ecryptfs_from_hex
   * @dst: Buffer to take the bytes from src hex; must be at least of
   *       size (src_size / 2)
   * @src: Buffer to be converted from a hex string respresentation to raw value
   * @dst_size: size of dst buffer, or number of hex characters pairs to convert
   */
  void ecryptfs_from_hex(char *dst, char *src, int dst_size)
  {
  	int x;
  	char tmp[3] = { 0, };
  
  	for (x = 0; x < dst_size; x++) {
  		tmp[0] = src[x * 2];
  		tmp[1] = src[x * 2 + 1];
  		dst[x] = (unsigned char)simple_strtol(tmp, NULL, 16);
  	}
  }
  
  /**
   * ecryptfs_calculate_md5 - calculates the md5 of @src
   * @dst: Pointer to 16 bytes of allocated memory
   * @crypt_stat: Pointer to crypt_stat struct for the current inode
   * @src: Data to be md5'd
   * @len: Length of @src
   *
   * Uses the allocated crypto context that crypt_stat references to
   * generate the MD5 sum of the contents of src.
   */
  static int ecryptfs_calculate_md5(char *dst,
  				  struct ecryptfs_crypt_stat *crypt_stat,
  				  char *src, int len)
  {

  	struct scatterlist sg;

  	struct hash_desc desc = {
  		.tfm = crypt_stat->hash_tfm,
  		.flags = CRYPTO_TFM_REQ_MAY_SLEEP
  	};
  	int rc = 0;

  	mutex_lock(&crypt_stat->cs_hash_tfm_mutex);

  	sg_init_one(&sg, (u8 *)src, len);

  	if (!desc.tfm) {
  		desc.tfm = crypto_alloc_hash(ECRYPTFS_DEFAULT_HASH, 0,
  					     CRYPTO_ALG_ASYNC);
  		if (IS_ERR(desc.tfm)) {
  			rc = PTR_ERR(desc.tfm);

  			ecryptfs_printk(KERN_ERR, "Error attempting to "

  					"allocate crypto context; rc = [%d]
  ",
  					rc);

  			goto out;
  		}

  		crypt_stat->hash_tfm = desc.tfm;

  	}

  	rc = crypto_hash_init(&desc);
  	if (rc) {
  		printk(KERN_ERR
  		       "%s: Error initializing crypto hash; rc = [%d]
  ",

  		       __func__, rc);

  		goto out;
  	}
  	rc = crypto_hash_update(&desc, &sg, len);
  	if (rc) {
  		printk(KERN_ERR
  		       "%s: Error updating crypto hash; rc = [%d]
  ",

  		       __func__, rc);

  		goto out;
  	}
  	rc = crypto_hash_final(&desc, dst);
  	if (rc) {
  		printk(KERN_ERR
  		       "%s: Error finalizing crypto hash; rc = [%d]
  ",

  		       __func__, rc);

  		goto out;
  	}

  out:

  	mutex_unlock(&crypt_stat->cs_hash_tfm_mutex);

  	return rc;
  }

  static int ecryptfs_crypto_api_algify_cipher_name(char **algified_name,
  						  char *cipher_name,
  						  char *chaining_modifier)

  {
  	int cipher_name_len = strlen(cipher_name);
  	int chaining_modifier_len = strlen(chaining_modifier);
  	int algified_name_len;
  	int rc;
  
  	algified_name_len = (chaining_modifier_len + cipher_name_len + 3);
  	(*algified_name) = kmalloc(algified_name_len, GFP_KERNEL);

  	if (!(*algified_name)) {

  		rc = -ENOMEM;
  		goto out;
  	}
  	snprintf((*algified_name), algified_name_len, "%s(%s)",
  		 chaining_modifier, cipher_name);
  	rc = 0;
  out:
  	return rc;
  }

  /**
   * ecryptfs_derive_iv
   * @iv: destination for the derived iv vale
   * @crypt_stat: Pointer to crypt_stat struct for the current inode

   * @offset: Offset of the extent whose IV we are to derive

   *
   * Generate the initialization vector from the given root IV and page
   * offset.
   *
   * Returns zero on success; non-zero on error.
   */

  int ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
  		       loff_t offset)

  {
  	int rc = 0;
  	char dst[MD5_DIGEST_SIZE];
  	char src[ECRYPTFS_MAX_IV_BYTES + 16];
  
  	if (unlikely(ecryptfs_verbosity > 0)) {
  		ecryptfs_printk(KERN_DEBUG, "root iv:
  ");
  		ecryptfs_dump_hex(crypt_stat->root_iv, crypt_stat->iv_bytes);
  	}
  	/* TODO: It is probably secure to just cast the least
  	 * significant bits of the root IV into an unsigned long and
  	 * add the offset to that rather than go through all this
  	 * hashing business. -Halcrow */
  	memcpy(src, crypt_stat->root_iv, crypt_stat->iv_bytes);
  	memset((src + crypt_stat->iv_bytes), 0, 16);

  	snprintf((src + crypt_stat->iv_bytes), 16, "%lld", offset);

  	if (unlikely(ecryptfs_verbosity > 0)) {
  		ecryptfs_printk(KERN_DEBUG, "source:
  ");
  		ecryptfs_dump_hex(src, (crypt_stat->iv_bytes + 16));
  	}
  	rc = ecryptfs_calculate_md5(dst, crypt_stat, src,
  				    (crypt_stat->iv_bytes + 16));
  	if (rc) {
  		ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
  				"MD5 while generating IV for a page
  ");
  		goto out;
  	}
  	memcpy(iv, dst, crypt_stat->iv_bytes);
  	if (unlikely(ecryptfs_verbosity > 0)) {
  		ecryptfs_printk(KERN_DEBUG, "derived iv:
  ");
  		ecryptfs_dump_hex(iv, crypt_stat->iv_bytes);
  	}
  out:
  	return rc;
  }
  
  /**
   * ecryptfs_init_crypt_stat
   * @crypt_stat: Pointer to the crypt_stat struct to initialize.
   *
   * Initialize the crypt_stat structure.
   */
  void
  ecryptfs_init_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
  {
  	memset((void *)crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));

  	INIT_LIST_HEAD(&crypt_stat->keysig_list);
  	mutex_init(&crypt_stat->keysig_list_mutex);

  	mutex_init(&crypt_stat->cs_mutex);
  	mutex_init(&crypt_stat->cs_tfm_mutex);

  	mutex_init(&crypt_stat->cs_hash_tfm_mutex);

  	crypt_stat->flags |= ECRYPTFS_STRUCT_INITIALIZED;

  }
  
  /**

   * ecryptfs_destroy_crypt_stat

   * @crypt_stat: Pointer to the crypt_stat struct to initialize.
   *
   * Releases all memory associated with a crypt_stat struct.
   */

  void ecryptfs_destroy_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)

  {

  	struct ecryptfs_key_sig *key_sig, *key_sig_tmp;

  	if (crypt_stat->tfm)

  		crypto_free_blkcipher(crypt_stat->tfm);

  	if (crypt_stat->hash_tfm)
  		crypto_free_hash(crypt_stat->hash_tfm);

  	list_for_each_entry_safe(key_sig, key_sig_tmp,
  				 &crypt_stat->keysig_list, crypt_stat_list) {
  		list_del(&key_sig->crypt_stat_list);
  		kmem_cache_free(ecryptfs_key_sig_cache, key_sig);
  	}

  	memset(crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
  }

  void ecryptfs_destroy_mount_crypt_stat(

  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
  {

  	struct ecryptfs_global_auth_tok *auth_tok, *auth_tok_tmp;
  
  	if (!(mount_crypt_stat->flags & ECRYPTFS_MOUNT_CRYPT_STAT_INITIALIZED))
  		return;
  	mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
  	list_for_each_entry_safe(auth_tok, auth_tok_tmp,
  				 &mount_crypt_stat->global_auth_tok_list,
  				 mount_crypt_stat_list) {
  		list_del(&auth_tok->mount_crypt_stat_list);

  		if (auth_tok->global_auth_tok_key
  		    && !(auth_tok->flags & ECRYPTFS_AUTH_TOK_INVALID))
  			key_put(auth_tok->global_auth_tok_key);
  		kmem_cache_free(ecryptfs_global_auth_tok_cache, auth_tok);
  	}
  	mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);

  	memset(mount_crypt_stat, 0, sizeof(struct ecryptfs_mount_crypt_stat));
  }
  
  /**
   * virt_to_scatterlist
   * @addr: Virtual address
   * @size: Size of data; should be an even multiple of the block size
   * @sg: Pointer to scatterlist array; set to NULL to obtain only
   *      the number of scatterlist structs required in array
   * @sg_size: Max array size
   *
   * Fills in a scatterlist array with page references for a passed
   * virtual address.
   *
   * Returns the number of scatterlist structs in array used
   */
  int virt_to_scatterlist(const void *addr, int size, struct scatterlist *sg,
  			int sg_size)
  {
  	int i = 0;
  	struct page *pg;
  	int offset;
  	int remainder_of_page;

  	sg_init_table(sg, sg_size);

  	while (size > 0 && i < sg_size) {
  		pg = virt_to_page(addr);
  		offset = offset_in_page(addr);

  		if (sg)
  			sg_set_page(&sg[i], pg, 0, offset);

  		remainder_of_page = PAGE_CACHE_SIZE - offset;
  		if (size >= remainder_of_page) {
  			if (sg)
  				sg[i].length = remainder_of_page;
  			addr += remainder_of_page;
  			size -= remainder_of_page;
  		} else {
  			if (sg)
  				sg[i].length = size;
  			addr += size;
  			size = 0;
  		}
  		i++;
  	}
  	if (size > 0)
  		return -ENOMEM;
  	return i;
  }
  
  /**
   * encrypt_scatterlist
   * @crypt_stat: Pointer to the crypt_stat struct to initialize.
   * @dest_sg: Destination of encrypted data
   * @src_sg: Data to be encrypted
   * @size: Length of data to be encrypted
   * @iv: iv to use during encryption
   *
   * Returns the number of bytes encrypted; negative value on error
   */
  static int encrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
  			       struct scatterlist *dest_sg,
  			       struct scatterlist *src_sg, int size,
  			       unsigned char *iv)
  {

  	struct blkcipher_desc desc = {
  		.tfm = crypt_stat->tfm,
  		.info = iv,
  		.flags = CRYPTO_TFM_REQ_MAY_SLEEP
  	};

  	int rc = 0;
  
  	BUG_ON(!crypt_stat || !crypt_stat->tfm

  	       || !(crypt_stat->flags & ECRYPTFS_STRUCT_INITIALIZED));

  	if (unlikely(ecryptfs_verbosity > 0)) {

  		ecryptfs_printk(KERN_DEBUG, "Key size [%zd]; key:
  ",

  				crypt_stat->key_size);
  		ecryptfs_dump_hex(crypt_stat->key,
  				  crypt_stat->key_size);
  	}
  	/* Consider doing this once, when the file is opened */
  	mutex_lock(&crypt_stat->cs_tfm_mutex);

  	if (!(crypt_stat->flags & ECRYPTFS_KEY_SET)) {
  		rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
  					     crypt_stat->key_size);
  		crypt_stat->flags |= ECRYPTFS_KEY_SET;
  	}

  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]
  ",
  				rc);
  		mutex_unlock(&crypt_stat->cs_tfm_mutex);
  		rc = -EINVAL;
  		goto out;
  	}
  	ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes.
  ", size);

  	crypto_blkcipher_encrypt_iv(&desc, dest_sg, src_sg, size);

  	mutex_unlock(&crypt_stat->cs_tfm_mutex);
  out:
  	return rc;
  }

  /**

   * ecryptfs_lower_offset_for_extent
   *
   * Convert an eCryptfs page index into a lower byte offset
   */

  static void ecryptfs_lower_offset_for_extent(loff_t *offset, loff_t extent_num,
  					     struct ecryptfs_crypt_stat *crypt_stat)

  {

  	(*offset) = ecryptfs_lower_header_size(crypt_stat)
  		    + (crypt_stat->extent_size * extent_num);

  }
  
  /**
   * ecryptfs_encrypt_extent
   * @enc_extent_page: Allocated page into which to encrypt the data in
   *                   @page
   * @crypt_stat: crypt_stat containing cryptographic context for the
   *              encryption operation
   * @page: Page containing plaintext data extent to encrypt
   * @extent_offset: Page extent offset for use in generating IV
   *
   * Encrypts one extent of data.
   *
   * Return zero on success; non-zero otherwise
   */
  static int ecryptfs_encrypt_extent(struct page *enc_extent_page,
  				   struct ecryptfs_crypt_stat *crypt_stat,
  				   struct page *page,
  				   unsigned long extent_offset)
  {

  	loff_t extent_base;

  	char extent_iv[ECRYPTFS_MAX_IV_BYTES];
  	int rc;

  	extent_base = (((loff_t)page->index)

  		       * (PAGE_CACHE_SIZE / crypt_stat->extent_size));
  	rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
  				(extent_base + extent_offset));
  	if (rc) {

  		ecryptfs_printk(KERN_ERR, "Error attempting to derive IV for "
  			"extent [0x%.16llx]; rc = [%d]
  ",
  			(unsigned long long)(extent_base + extent_offset), rc);

  		goto out;
  	}
  	if (unlikely(ecryptfs_verbosity > 0)) {
  		ecryptfs_printk(KERN_DEBUG, "Encrypting extent "
  				"with iv:
  ");
  		ecryptfs_dump_hex(extent_iv, crypt_stat->iv_bytes);
  		ecryptfs_printk(KERN_DEBUG, "First 8 bytes before "
  				"encryption:
  ");
  		ecryptfs_dump_hex((char *)
  				  (page_address(page)
  				   + (extent_offset * crypt_stat->extent_size)),
  				  8);
  	}
  	rc = ecryptfs_encrypt_page_offset(crypt_stat, enc_extent_page, 0,
  					  page, (extent_offset
  						 * crypt_stat->extent_size),
  					  crypt_stat->extent_size, extent_iv);
  	if (rc < 0) {
  		printk(KERN_ERR "%s: Error attempting to encrypt page with "
  		       "page->index = [%ld], extent_offset = [%ld]; "

  		       "rc = [%d]
  ", __func__, page->index, extent_offset,

  		       rc);
  		goto out;
  	}
  	rc = 0;
  	if (unlikely(ecryptfs_verbosity > 0)) {

  		ecryptfs_printk(KERN_DEBUG, "Encrypt extent [0x%.16llx]; "
  			"rc = [%d]
  ",
  			(unsigned long long)(extent_base + extent_offset), rc);

  		ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
  				"encryption:
  ");
  		ecryptfs_dump_hex((char *)(page_address(enc_extent_page)), 8);
  	}
  out:
  	return rc;
  }
  
  /**

   * ecryptfs_encrypt_page

   * @page: Page mapped from the eCryptfs inode for the file; contains
   *        decrypted content that needs to be encrypted (to a temporary
   *        page; not in place) and written out to the lower file

   *
   * Encrypt an eCryptfs page. This is done on a per-extent basis. Note
   * that eCryptfs pages may straddle the lower pages -- for instance,
   * if the file was created on a machine with an 8K page size
   * (resulting in an 8K header), and then the file is copied onto a
   * host with a 32K page size, then when reading page 0 of the eCryptfs
   * file, 24K of page 0 of the lower file will be read and decrypted,
   * and then 8K of page 1 of the lower file will be read and decrypted.
   *

   * Returns zero on success; negative on error
   */

  int ecryptfs_encrypt_page(struct page *page)

  {

  	struct inode *ecryptfs_inode;

  	struct ecryptfs_crypt_stat *crypt_stat;

  	char *enc_extent_virt;
  	struct page *enc_extent_page = NULL;

  	loff_t extent_offset;

  	int rc = 0;

  
  	ecryptfs_inode = page->mapping->host;
  	crypt_stat =
  		&(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);

  	BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));

  	enc_extent_page = alloc_page(GFP_USER);
  	if (!enc_extent_page) {

  		rc = -ENOMEM;
  		ecryptfs_printk(KERN_ERR, "Error allocating memory for "
  				"encrypted extent
  ");
  		goto out;
  	}

  	enc_extent_virt = kmap(enc_extent_page);

  	for (extent_offset = 0;
  	     extent_offset < (PAGE_CACHE_SIZE / crypt_stat->extent_size);
  	     extent_offset++) {
  		loff_t offset;
  
  		rc = ecryptfs_encrypt_extent(enc_extent_page, crypt_stat, page,
  					     extent_offset);

  		if (rc) {

  			printk(KERN_ERR "%s: Error encrypting extent; "

  			       "rc = [%d]
  ", __func__, rc);

  			goto out;
  		}

  		ecryptfs_lower_offset_for_extent(

  			&offset, ((((loff_t)page->index)
  				   * (PAGE_CACHE_SIZE
  				      / crypt_stat->extent_size))

  				  + extent_offset), crypt_stat);
  		rc = ecryptfs_write_lower(ecryptfs_inode, enc_extent_virt,
  					  offset, crypt_stat->extent_size);

  		if (rc < 0) {

  			ecryptfs_printk(KERN_ERR, "Error attempting "
  					"to write lower page; rc = [%d]"
  					"
  ", rc);
  			goto out;

  		}

  	}

  	rc = 0;

  out:

  	if (enc_extent_page) {
  		kunmap(enc_extent_page);
  		__free_page(enc_extent_page);
  	}

  	return rc;
  }
  
  static int ecryptfs_decrypt_extent(struct page *page,
  				   struct ecryptfs_crypt_stat *crypt_stat,
  				   struct page *enc_extent_page,
  				   unsigned long extent_offset)
  {

  	loff_t extent_base;

  	char extent_iv[ECRYPTFS_MAX_IV_BYTES];
  	int rc;

  	extent_base = (((loff_t)page->index)

  		       * (PAGE_CACHE_SIZE / crypt_stat->extent_size));
  	rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
  				(extent_base + extent_offset));

  	if (rc) {

  		ecryptfs_printk(KERN_ERR, "Error attempting to derive IV for "
  			"extent [0x%.16llx]; rc = [%d]
  ",
  			(unsigned long long)(extent_base + extent_offset), rc);

  		goto out;
  	}
  	if (unlikely(ecryptfs_verbosity > 0)) {
  		ecryptfs_printk(KERN_DEBUG, "Decrypting extent "
  				"with iv:
  ");
  		ecryptfs_dump_hex(extent_iv, crypt_stat->iv_bytes);
  		ecryptfs_printk(KERN_DEBUG, "First 8 bytes before "
  				"decryption:
  ");
  		ecryptfs_dump_hex((char *)
  				  (page_address(enc_extent_page)
  				   + (extent_offset * crypt_stat->extent_size)),
  				  8);
  	}
  	rc = ecryptfs_decrypt_page_offset(crypt_stat, page,
  					  (extent_offset
  					   * crypt_stat->extent_size),
  					  enc_extent_page, 0,
  					  crypt_stat->extent_size, extent_iv);
  	if (rc < 0) {
  		printk(KERN_ERR "%s: Error attempting to decrypt to page with "
  		       "page->index = [%ld], extent_offset = [%ld]; "

  		       "rc = [%d]
  ", __func__, page->index, extent_offset,

  		       rc);
  		goto out;
  	}
  	rc = 0;
  	if (unlikely(ecryptfs_verbosity > 0)) {

  		ecryptfs_printk(KERN_DEBUG, "Decrypt extent [0x%.16llx]; "
  			"rc = [%d]
  ",
  			(unsigned long long)(extent_base + extent_offset), rc);

  		ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
  				"decryption:
  ");
  		ecryptfs_dump_hex((char *)(page_address(page)
  					   + (extent_offset
  					      * crypt_stat->extent_size)), 8);

  	}
  out:
  	return rc;
  }
  
  /**
   * ecryptfs_decrypt_page

   * @page: Page mapped from the eCryptfs inode for the file; data read
   *        and decrypted from the lower file will be written into this
   *        page

   *
   * Decrypt an eCryptfs page. This is done on a per-extent basis. Note
   * that eCryptfs pages may straddle the lower pages -- for instance,
   * if the file was created on a machine with an 8K page size
   * (resulting in an 8K header), and then the file is copied onto a
   * host with a 32K page size, then when reading page 0 of the eCryptfs
   * file, 24K of page 0 of the lower file will be read and decrypted,
   * and then 8K of page 1 of the lower file will be read and decrypted.
   *
   * Returns zero on success; negative on error
   */

  int ecryptfs_decrypt_page(struct page *page)

  {

  	struct inode *ecryptfs_inode;

  	struct ecryptfs_crypt_stat *crypt_stat;

  	char *enc_extent_virt;
  	struct page *enc_extent_page = NULL;

  	unsigned long extent_offset;

  	int rc = 0;

  	ecryptfs_inode = page->mapping->host;
  	crypt_stat =
  		&(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);

  	BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));

  	enc_extent_page = alloc_page(GFP_USER);
  	if (!enc_extent_page) {

  		rc = -ENOMEM;

  		ecryptfs_printk(KERN_ERR, "Error allocating memory for "
  				"encrypted extent
  ");

  		goto out;

  	}

  	enc_extent_virt = kmap(enc_extent_page);

  	for (extent_offset = 0;
  	     extent_offset < (PAGE_CACHE_SIZE / crypt_stat->extent_size);
  	     extent_offset++) {
  		loff_t offset;
  
  		ecryptfs_lower_offset_for_extent(
  			&offset, ((page->index * (PAGE_CACHE_SIZE
  						  / crypt_stat->extent_size))
  				  + extent_offset), crypt_stat);
  		rc = ecryptfs_read_lower(enc_extent_virt, offset,
  					 crypt_stat->extent_size,
  					 ecryptfs_inode);

  		if (rc < 0) {

  			ecryptfs_printk(KERN_ERR, "Error attempting "
  					"to read lower page; rc = [%d]"
  					"
  ", rc);

  			goto out;

  		}

  		rc = ecryptfs_decrypt_extent(page, crypt_stat, enc_extent_page,
  					     extent_offset);
  		if (rc) {
  			printk(KERN_ERR "%s: Error encrypting extent; "

  			       "rc = [%d]
  ", __func__, rc);

  			goto out;

  		}

  	}
  out:

  	if (enc_extent_page) {
  		kunmap(enc_extent_page);
  		__free_page(enc_extent_page);
  	}

  	return rc;
  }
  
  /**
   * decrypt_scatterlist

   * @crypt_stat: Cryptographic context
   * @dest_sg: The destination scatterlist to decrypt into
   * @src_sg: The source scatterlist to decrypt from
   * @size: The number of bytes to decrypt
   * @iv: The initialization vector to use for the decryption

   *
   * Returns the number of bytes decrypted; negative value on error
   */
  static int decrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
  			       struct scatterlist *dest_sg,
  			       struct scatterlist *src_sg, int size,
  			       unsigned char *iv)
  {

  	struct blkcipher_desc desc = {
  		.tfm = crypt_stat->tfm,
  		.info = iv,
  		.flags = CRYPTO_TFM_REQ_MAY_SLEEP
  	};

  	int rc = 0;
  
  	/* Consider doing this once, when the file is opened */
  	mutex_lock(&crypt_stat->cs_tfm_mutex);

  	rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
  				     crypt_stat->key_size);

  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]
  ",
  				rc);
  		mutex_unlock(&crypt_stat->cs_tfm_mutex);
  		rc = -EINVAL;
  		goto out;
  	}
  	ecryptfs_printk(KERN_DEBUG, "Decrypting [%d] bytes.
  ", size);

  	rc = crypto_blkcipher_decrypt_iv(&desc, dest_sg, src_sg, size);

  	mutex_unlock(&crypt_stat->cs_tfm_mutex);
  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Error decrypting; rc = [%d]
  ",
  				rc);
  		goto out;
  	}
  	rc = size;
  out:
  	return rc;
  }
  
  /**
   * ecryptfs_encrypt_page_offset

   * @crypt_stat: The cryptographic context
   * @dst_page: The page to encrypt into
   * @dst_offset: The offset in the page to encrypt into
   * @src_page: The page to encrypt from
   * @src_offset: The offset in the page to encrypt from
   * @size: The number of bytes to encrypt
   * @iv: The initialization vector to use for the encryption

   *
   * Returns the number of bytes encrypted
   */
  static int
  ecryptfs_encrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
  			     struct page *dst_page, int dst_offset,
  			     struct page *src_page, int src_offset, int size,
  			     unsigned char *iv)
  {
  	struct scatterlist src_sg, dst_sg;

  	sg_init_table(&src_sg, 1);
  	sg_init_table(&dst_sg, 1);

  	sg_set_page(&src_sg, src_page, size, src_offset);
  	sg_set_page(&dst_sg, dst_page, size, dst_offset);

  	return encrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
  }
  
  /**
   * ecryptfs_decrypt_page_offset

   * @crypt_stat: The cryptographic context
   * @dst_page: The page to decrypt into
   * @dst_offset: The offset in the page to decrypt into
   * @src_page: The page to decrypt from
   * @src_offset: The offset in the page to decrypt from
   * @size: The number of bytes to decrypt
   * @iv: The initialization vector to use for the decryption

   *
   * Returns the number of bytes decrypted
   */
  static int
  ecryptfs_decrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
  			     struct page *dst_page, int dst_offset,
  			     struct page *src_page, int src_offset, int size,
  			     unsigned char *iv)
  {
  	struct scatterlist src_sg, dst_sg;

  	sg_init_table(&src_sg, 1);

  	sg_set_page(&src_sg, src_page, size, src_offset);

  	sg_init_table(&dst_sg, 1);

  	sg_set_page(&dst_sg, dst_page, size, dst_offset);

  	return decrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
  }
  
  #define ECRYPTFS_MAX_SCATTERLIST_LEN 4
  
  /**
   * ecryptfs_init_crypt_ctx

   * @crypt_stat: Uninitialized crypt stats structure

   *
   * Initialize the crypto context.
   *
   * TODO: Performance: Keep a cache of initialized cipher contexts;
   * only init if needed
   */
  int ecryptfs_init_crypt_ctx(struct ecryptfs_crypt_stat *crypt_stat)
  {

  	char *full_alg_name;

  	int rc = -EINVAL;
  
  	if (!crypt_stat->cipher) {
  		ecryptfs_printk(KERN_ERR, "No cipher specified
  ");
  		goto out;
  	}
  	ecryptfs_printk(KERN_DEBUG,
  			"Initializing cipher [%s]; strlen = [%d]; "

  			"key_size_bits = [%zd]
  ",

  			crypt_stat->cipher, (int)strlen(crypt_stat->cipher),
  			crypt_stat->key_size << 3);
  	if (crypt_stat->tfm) {
  		rc = 0;
  		goto out;
  	}
  	mutex_lock(&crypt_stat->cs_tfm_mutex);

  	rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
  						    crypt_stat->cipher, "cbc");
  	if (rc)

  		goto out_unlock;

  	crypt_stat->tfm = crypto_alloc_blkcipher(full_alg_name, 0,
  						 CRYPTO_ALG_ASYNC);
  	kfree(full_alg_name);

  	if (IS_ERR(crypt_stat->tfm)) {
  		rc = PTR_ERR(crypt_stat->tfm);

  		crypt_stat->tfm = NULL;

  		ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): "
  				"Error initializing cipher [%s]
  ",
  				crypt_stat->cipher);

  		goto out_unlock;

  	}

  	crypto_blkcipher_set_flags(crypt_stat->tfm, CRYPTO_TFM_REQ_WEAK_KEY);

  	rc = 0;

  out_unlock:
  	mutex_unlock(&crypt_stat->cs_tfm_mutex);

  out:
  	return rc;
  }
  
  static void set_extent_mask_and_shift(struct ecryptfs_crypt_stat *crypt_stat)
  {
  	int extent_size_tmp;
  
  	crypt_stat->extent_mask = 0xFFFFFFFF;
  	crypt_stat->extent_shift = 0;
  	if (crypt_stat->extent_size == 0)
  		return;
  	extent_size_tmp = crypt_stat->extent_size;
  	while ((extent_size_tmp & 0x01) == 0) {
  		extent_size_tmp >>= 1;
  		crypt_stat->extent_mask <<= 1;
  		crypt_stat->extent_shift++;
  	}
  }
  
  void ecryptfs_set_default_sizes(struct ecryptfs_crypt_stat *crypt_stat)
  {
  	/* Default values; may be overwritten as we are parsing the
  	 * packets. */
  	crypt_stat->extent_size = ECRYPTFS_DEFAULT_EXTENT_SIZE;
  	set_extent_mask_and_shift(crypt_stat);
  	crypt_stat->iv_bytes = ECRYPTFS_DEFAULT_IV_BYTES;

  	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)

  		crypt_stat->metadata_size = ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;

  	else {
  		if (PAGE_CACHE_SIZE <= ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE)

  			crypt_stat->metadata_size =

  				ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;

  		else

  			crypt_stat->metadata_size = PAGE_CACHE_SIZE;

  	}

  }
  
  /**
   * ecryptfs_compute_root_iv
   * @crypt_stats
   *
   * On error, sets the root IV to all 0's.
   */
  int ecryptfs_compute_root_iv(struct ecryptfs_crypt_stat *crypt_stat)
  {
  	int rc = 0;
  	char dst[MD5_DIGEST_SIZE];
  
  	BUG_ON(crypt_stat->iv_bytes > MD5_DIGEST_SIZE);
  	BUG_ON(crypt_stat->iv_bytes <= 0);

  	if (!(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {

  		rc = -EINVAL;
  		ecryptfs_printk(KERN_WARNING, "Session key not valid; "
  				"cannot generate root IV
  ");
  		goto out;
  	}
  	rc = ecryptfs_calculate_md5(dst, crypt_stat, crypt_stat->key,
  				    crypt_stat->key_size);
  	if (rc) {
  		ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
  				"MD5 while generating root IV
  ");
  		goto out;
  	}
  	memcpy(crypt_stat->root_iv, dst, crypt_stat->iv_bytes);
  out:
  	if (rc) {
  		memset(crypt_stat->root_iv, 0, crypt_stat->iv_bytes);

  		crypt_stat->flags |= ECRYPTFS_SECURITY_WARNING;

  	}
  	return rc;
  }
  
  static void ecryptfs_generate_new_key(struct ecryptfs_crypt_stat *crypt_stat)
  {
  	get_random_bytes(crypt_stat->key, crypt_stat->key_size);

  	crypt_stat->flags |= ECRYPTFS_KEY_VALID;

  	ecryptfs_compute_root_iv(crypt_stat);
  	if (unlikely(ecryptfs_verbosity > 0)) {
  		ecryptfs_printk(KERN_DEBUG, "Generated new session key:
  ");
  		ecryptfs_dump_hex(crypt_stat->key,
  				  crypt_stat->key_size);
  	}
  }
  
  /**

   * ecryptfs_copy_mount_wide_flags_to_inode_flags

   * @crypt_stat: The inode's cryptographic context
   * @mount_crypt_stat: The mount point's cryptographic context

   *
   * This function propagates the mount-wide flags to individual inode
   * flags.
   */
  static void ecryptfs_copy_mount_wide_flags_to_inode_flags(
  	struct ecryptfs_crypt_stat *crypt_stat,
  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
  {
  	if (mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED)
  		crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
  	if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
  		crypt_stat->flags |= ECRYPTFS_VIEW_AS_ENCRYPTED;

  	if (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES) {
  		crypt_stat->flags |= ECRYPTFS_ENCRYPT_FILENAMES;
  		if (mount_crypt_stat->flags
  		    & ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK)
  			crypt_stat->flags |= ECRYPTFS_ENCFN_USE_MOUNT_FNEK;
  		else if (mount_crypt_stat->flags
  			 & ECRYPTFS_GLOBAL_ENCFN_USE_FEK)
  			crypt_stat->flags |= ECRYPTFS_ENCFN_USE_FEK;
  	}

  }

  static int ecryptfs_copy_mount_wide_sigs_to_inode_sigs(
  	struct ecryptfs_crypt_stat *crypt_stat,
  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
  {
  	struct ecryptfs_global_auth_tok *global_auth_tok;
  	int rc = 0;

  	mutex_lock(&crypt_stat->keysig_list_mutex);

  	mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);

  	list_for_each_entry(global_auth_tok,
  			    &mount_crypt_stat->global_auth_tok_list,
  			    mount_crypt_stat_list) {

  		if (global_auth_tok->flags & ECRYPTFS_AUTH_TOK_FNEK)
  			continue;

  		rc = ecryptfs_add_keysig(crypt_stat, global_auth_tok->sig);
  		if (rc) {
  			printk(KERN_ERR "Error adding keysig; rc = [%d]
  ", rc);

  			goto out;
  		}
  	}

  out:

  	mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
  	mutex_unlock(&crypt_stat->keysig_list_mutex);

  	return rc;
  }

  /**

   * ecryptfs_set_default_crypt_stat_vals

   * @crypt_stat: The inode's cryptographic context
   * @mount_crypt_stat: The mount point's cryptographic context

   *
   * Default values in the event that policy does not override them.
   */
  static void ecryptfs_set_default_crypt_stat_vals(
  	struct ecryptfs_crypt_stat *crypt_stat,
  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
  {

  	ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
  						      mount_crypt_stat);

  	ecryptfs_set_default_sizes(crypt_stat);
  	strcpy(crypt_stat->cipher, ECRYPTFS_DEFAULT_CIPHER);
  	crypt_stat->key_size = ECRYPTFS_DEFAULT_KEY_BYTES;

  	crypt_stat->flags &= ~(ECRYPTFS_KEY_VALID);

  	crypt_stat->file_version = ECRYPTFS_FILE_VERSION;
  	crypt_stat->mount_crypt_stat = mount_crypt_stat;
  }
  
  /**
   * ecryptfs_new_file_context

   * @ecryptfs_inode: The eCryptfs inode

   *
   * If the crypto context for the file has not yet been established,
   * this is where we do that.  Establishing a new crypto context
   * involves the following decisions:
   *  - What cipher to use?
   *  - What set of authentication tokens to use?
   * Here we just worry about getting enough information into the
   * authentication tokens so that we know that they are available.
   * We associate the available authentication tokens with the new file
   * via the set of signatures in the crypt_stat struct.  Later, when
   * the headers are actually written out, we may again defer to
   * userspace to perform the encryption of the session key; for the
   * foreseeable future, this will be the case with public key packets.
   *
   * Returns zero on success; non-zero otherwise
   */

  int ecryptfs_new_file_context(struct inode *ecryptfs_inode)

  {

  	struct ecryptfs_crypt_stat *crypt_stat =

  	    &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;

  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
  	    &ecryptfs_superblock_to_private(

  		    ecryptfs_inode->i_sb)->mount_crypt_stat;

  	int cipher_name_len;

  	int rc = 0;

  
  	ecryptfs_set_default_crypt_stat_vals(crypt_stat, mount_crypt_stat);

  	crypt_stat->flags |= (ECRYPTFS_ENCRYPTED | ECRYPTFS_KEY_VALID);

  	ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
  						      mount_crypt_stat);
  	rc = ecryptfs_copy_mount_wide_sigs_to_inode_sigs(crypt_stat,
  							 mount_crypt_stat);
  	if (rc) {
  		printk(KERN_ERR "Error attempting to copy mount-wide key sigs "
  		       "to the inode key sigs; rc = [%d]
  ", rc);
  		goto out;
  	}
  	cipher_name_len =
  		strlen(mount_crypt_stat->global_default_cipher_name);
  	memcpy(crypt_stat->cipher,
  	       mount_crypt_stat->global_default_cipher_name,
  	       cipher_name_len);
  	crypt_stat->cipher[cipher_name_len] = '\0';
  	crypt_stat->key_size =
  		mount_crypt_stat->global_default_cipher_key_size;
  	ecryptfs_generate_new_key(crypt_stat);

  	rc = ecryptfs_init_crypt_ctx(crypt_stat);
  	if (rc)
  		ecryptfs_printk(KERN_ERR, "Error initializing cryptographic "
  				"context for cipher [%s]: rc = [%d]
  ",
  				crypt_stat->cipher, rc);

  out:

  	return rc;
  }
  
  /**

   * ecryptfs_validate_marker - check for the ecryptfs marker

   * @data: The data block in which to check
   *

   * Returns zero if marker found; -EINVAL if not found

   */

  static int ecryptfs_validate_marker(char *data)

  {
  	u32 m_1, m_2;

  	m_1 = get_unaligned_be32(data);
  	m_2 = get_unaligned_be32(data + 4);

  	if ((m_1 ^ MAGIC_ECRYPTFS_MARKER) == m_2)

  		return 0;

  	ecryptfs_printk(KERN_DEBUG, "m_1 = [0x%.8x]; m_2 = [0x%.8x]; "
  			"MAGIC_ECRYPTFS_MARKER = [0x%.8x]
  ", m_1, m_2,
  			MAGIC_ECRYPTFS_MARKER);
  	ecryptfs_printk(KERN_DEBUG, "(m_1 ^ MAGIC_ECRYPTFS_MARKER) = "
  			"[0x%.8x]
  ", (m_1 ^ MAGIC_ECRYPTFS_MARKER));

  	return -EINVAL;

  }
  
  struct ecryptfs_flag_map_elem {
  	u32 file_flag;
  	u32 local_flag;
  };
  
  /* Add support for additional flags by adding elements here. */
  static struct ecryptfs_flag_map_elem ecryptfs_flag_map[] = {
  	{0x00000001, ECRYPTFS_ENABLE_HMAC},

  	{0x00000002, ECRYPTFS_ENCRYPTED},

  	{0x00000004, ECRYPTFS_METADATA_IN_XATTR},
  	{0x00000008, ECRYPTFS_ENCRYPT_FILENAMES}

  };
  
  /**
   * ecryptfs_process_flags

   * @crypt_stat: The cryptographic context

   * @page_virt: Source data to be parsed
   * @bytes_read: Updated with the number of bytes read
   *
   * Returns zero on success; non-zero if the flag set is invalid
   */
  static int ecryptfs_process_flags(struct ecryptfs_crypt_stat *crypt_stat,
  				  char *page_virt, int *bytes_read)
  {
  	int rc = 0;
  	int i;
  	u32 flags;

  	flags = get_unaligned_be32(page_virt);

  	for (i = 0; i < ((sizeof(ecryptfs_flag_map)
  			  / sizeof(struct ecryptfs_flag_map_elem))); i++)
  		if (flags & ecryptfs_flag_map[i].file_flag) {

  			crypt_stat->flags |= ecryptfs_flag_map[i].local_flag;

  		} else

  			crypt_stat->flags &= ~(ecryptfs_flag_map[i].local_flag);

  	/* Version is in top 8 bits of the 32-bit flag vector */
  	crypt_stat->file_version = ((flags >> 24) & 0xFF);
  	(*bytes_read) = 4;
  	return rc;
  }
  
  /**
   * write_ecryptfs_marker
   * @page_virt: The pointer to in a page to begin writing the marker
   * @written: Number of bytes written
   *
   * Marker = 0x3c81b7f5
   */
  static void write_ecryptfs_marker(char *page_virt, size_t *written)
  {
  	u32 m_1, m_2;
  
  	get_random_bytes(&m_1, (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
  	m_2 = (m_1 ^ MAGIC_ECRYPTFS_MARKER);

  	put_unaligned_be32(m_1, page_virt);
  	page_virt += (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2);
  	put_unaligned_be32(m_2, page_virt);

  	(*written) = MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
  }

  void ecryptfs_write_crypt_stat_flags(char *page_virt,
  				     struct ecryptfs_crypt_stat *crypt_stat,
  				     size_t *written)

  {
  	u32 flags = 0;
  	int i;
  
  	for (i = 0; i < ((sizeof(ecryptfs_flag_map)
  			  / sizeof(struct ecryptfs_flag_map_elem))); i++)

  		if (crypt_stat->flags & ecryptfs_flag_map[i].local_flag)

  			flags |= ecryptfs_flag_map[i].file_flag;
  	/* Version is in top 8 bits of the 32-bit flag vector */
  	flags |= ((((u8)crypt_stat->file_version) << 24) & 0xFF000000);

  	put_unaligned_be32(flags, page_virt);

  	(*written) = 4;
  }
  
  struct ecryptfs_cipher_code_str_map_elem {
  	char cipher_str[16];

  	u8 cipher_code;

  };
  
  /* Add support for additional ciphers by adding elements here. The
   * cipher_code is whatever OpenPGP applicatoins use to identify the
   * ciphers. List in order of probability. */
  static struct ecryptfs_cipher_code_str_map_elem
  ecryptfs_cipher_code_str_map[] = {
  	{"aes",RFC2440_CIPHER_AES_128 },
  	{"blowfish", RFC2440_CIPHER_BLOWFISH},
  	{"des3_ede", RFC2440_CIPHER_DES3_EDE},
  	{"cast5", RFC2440_CIPHER_CAST_5},
  	{"twofish", RFC2440_CIPHER_TWOFISH},
  	{"cast6", RFC2440_CIPHER_CAST_6},
  	{"aes", RFC2440_CIPHER_AES_192},
  	{"aes", RFC2440_CIPHER_AES_256}
  };
  
  /**
   * ecryptfs_code_for_cipher_string

   * @cipher_name: The string alias for the cipher
   * @key_bytes: Length of key in bytes; used for AES code selection

   *
   * Returns zero on no match, or the cipher code on match
   */

  u8 ecryptfs_code_for_cipher_string(char *cipher_name, size_t key_bytes)

  {
  	int i;

  	u8 code = 0;

  	struct ecryptfs_cipher_code_str_map_elem *map =
  		ecryptfs_cipher_code_str_map;

  	if (strcmp(cipher_name, "aes") == 0) {
  		switch (key_bytes) {

  		case 16:
  			code = RFC2440_CIPHER_AES_128;
  			break;
  		case 24:
  			code = RFC2440_CIPHER_AES_192;
  			break;
  		case 32:
  			code = RFC2440_CIPHER_AES_256;
  		}
  	} else {
  		for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)

  			if (strcmp(cipher_name, map[i].cipher_str) == 0) {

  				code = map[i].cipher_code;
  				break;
  			}
  	}
  	return code;
  }
  
  /**
   * ecryptfs_cipher_code_to_string
   * @str: Destination to write out the cipher name
   * @cipher_code: The code to convert to cipher name string
   *
   * Returns zero on success
   */

  int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code)

  {
  	int rc = 0;
  	int i;
  
  	str[0] = '\0';
  	for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
  		if (cipher_code == ecryptfs_cipher_code_str_map[i].cipher_code)
  			strcpy(str, ecryptfs_cipher_code_str_map[i].cipher_str);
  	if (str[0] == '\0') {
  		ecryptfs_printk(KERN_WARNING, "Cipher code not recognized: "
  				"[%d]
  ", cipher_code);
  		rc = -EINVAL;
  	}
  	return rc;
  }

  int ecryptfs_read_and_validate_header_region(struct inode *inode)

  {

  	u8 file_size[ECRYPTFS_SIZE_AND_MARKER_BYTES];
  	u8 *marker = file_size + ECRYPTFS_FILE_SIZE_BYTES;

  	int rc;

  	rc = ecryptfs_read_lower(file_size, 0, ECRYPTFS_SIZE_AND_MARKER_BYTES,
  				 inode);
  	if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
  		return rc >= 0 ? -EINVAL : rc;
  	rc = ecryptfs_validate_marker(marker);
  	if (!rc)
  		ecryptfs_i_size_init(file_size, inode);

  	return rc;
  }

  void
  ecryptfs_write_header_metadata(char *virt,
  			       struct ecryptfs_crypt_stat *crypt_stat,
  			       size_t *written)

  {
  	u32 header_extent_size;
  	u16 num_header_extents_at_front;

  	header_extent_size = (u32)crypt_stat->extent_size;

  	num_header_extents_at_front =

  		(u16)(crypt_stat->metadata_size / crypt_stat->extent_size);

  	put_unaligned_be32(header_extent_size, virt);

  	virt += 4;

  	put_unaligned_be16(num_header_extents_at_front, virt);

  	(*written) = 6;
  }

  struct kmem_cache *ecryptfs_header_cache;

  
  /**
   * ecryptfs_write_headers_virt

   * @page_virt: The virtual address to write the headers to

   * @max: The size of memory allocated at page_virt

   * @size: Set to the number of bytes written by this function
   * @crypt_stat: The cryptographic context
   * @ecryptfs_dentry: The eCryptfs dentry

   *
   * Format version: 1
   *
   *   Header Extent:
   *     Octets 0-7:        Unencrypted file size (big-endian)
   *     Octets 8-15:       eCryptfs special marker
   *     Octets 16-19:      Flags
   *      Octet 16:         File format version number (between 0 and 255)
   *      Octets 17-18:     Reserved
   *      Octet 19:         Bit 1 (lsb): Reserved
   *                        Bit 2: Encrypted?
   *                        Bits 3-8: Reserved
   *     Octets 20-23:      Header extent size (big-endian)
   *     Octets 24-25:      Number of header extents at front of file
   *                        (big-endian)
   *     Octet  26:         Begin RFC 2440 authentication token packet set
   *   Data Extent 0:
   *     Lower data (CBC encrypted)
   *   Data Extent 1:
   *     Lower data (CBC encrypted)
   *   ...
   *
   * Returns zero on success
   */

  static int ecryptfs_write_headers_virt(char *page_virt, size_t max,
  				       size_t *size,

  				       struct ecryptfs_crypt_stat *crypt_stat,
  				       struct dentry *ecryptfs_dentry)

  {
  	int rc;
  	size_t written;
  	size_t offset;
  
  	offset = ECRYPTFS_FILE_SIZE_BYTES;
  	write_ecryptfs_marker((page_virt + offset), &written);
  	offset += written;

  	ecryptfs_write_crypt_stat_flags((page_virt + offset), crypt_stat,
  					&written);

  	offset += written;

  	ecryptfs_write_header_metadata((page_virt + offset), crypt_stat,
  				       &written);

  	offset += written;
  	rc = ecryptfs_generate_key_packet_set((page_virt + offset), crypt_stat,
  					      ecryptfs_dentry, &written,

  					      max - offset);

  	if (rc)
  		ecryptfs_printk(KERN_WARNING, "Error generating key packet "
  				"set; rc = [%d]
  ", rc);

  	if (size) {
  		offset += written;
  		*size = offset;
  	}
  	return rc;
  }

  static int

  ecryptfs_write_metadata_to_contents(struct inode *ecryptfs_inode,

  				    char *virt, size_t virt_len)

  {

  	int rc;

  	rc = ecryptfs_write_lower(ecryptfs_inode, virt,

  				  0, virt_len);

  	if (rc < 0)

  		printk(KERN_ERR "%s: Error attempting to write header "

  		       "information to lower file; rc = [%d]
  ", __func__, rc);
  	else
  		rc = 0;

  	return rc;

  }

  static int
  ecryptfs_write_metadata_to_xattr(struct dentry *ecryptfs_dentry,

  				 char *page_virt, size_t size)

  {
  	int rc;
  
  	rc = ecryptfs_setxattr(ecryptfs_dentry, ECRYPTFS_XATTR_NAME, page_virt,
  			       size, 0);

  	return rc;
  }

  static unsigned long ecryptfs_get_zeroed_pages(gfp_t gfp_mask,
  					       unsigned int order)
  {
  	struct page *page;
  
  	page = alloc_pages(gfp_mask | __GFP_ZERO, order);
  	if (page)
  		return (unsigned long) page_address(page);
  	return 0;
  }

  /**

   * ecryptfs_write_metadata

   * @ecryptfs_dentry: The eCryptfs dentry, which should be negative
   * @ecryptfs_inode: The newly created eCryptfs inode

   *
   * Write the file headers out.  This will likely involve a userspace
   * callout, in which the session key is encrypted with one or more
   * public keys and/or the passphrase necessary to do the encryption is
   * retrieved via a prompt.  Exactly what happens at this point should
   * be policy-dependent.
   *
   * Returns zero on success; non-zero on error
   */

  int ecryptfs_write_metadata(struct dentry *ecryptfs_dentry,
  			    struct inode *ecryptfs_inode)

  {

  	struct ecryptfs_crypt_stat *crypt_stat =

  		&ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;

  	unsigned int order;

  	char *virt;

  	size_t virt_len;

  	size_t size = 0;

  	int rc = 0;

  	if (likely(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
  		if (!(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {

  			printk(KERN_ERR "Key is invalid; bailing out
  ");

  			rc = -EINVAL;
  			goto out;
  		}
  	} else {

  		printk(KERN_WARNING "%s: Encrypted flag not set
  ",

  		       __func__);

  		rc = -EINVAL;

  		goto out;
  	}

  	virt_len = crypt_stat->metadata_size;

  	order = get_order(virt_len);

  	/* Released in this function */

  	virt = (char *)ecryptfs_get_zeroed_pages(GFP_KERNEL, order);

  	if (!virt) {

  		printk(KERN_ERR "%s: Out of memory
  ", __func__);

  		rc = -ENOMEM;
  		goto out;
  	}

  	/* Zeroed page ensures the in-header unencrypted i_size is set to 0 */

  	rc = ecryptfs_write_headers_virt(virt, virt_len, &size, crypt_stat,
  					 ecryptfs_dentry);

  	if (unlikely(rc)) {

  		printk(KERN_ERR "%s: Error whilst writing headers; rc = [%d]
  ",

  		       __func__, rc);

  		goto out_free;
  	}

  	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)

  		rc = ecryptfs_write_metadata_to_xattr(ecryptfs_dentry, virt,
  						      size);

  	else

  		rc = ecryptfs_write_metadata_to_contents(ecryptfs_inode, virt,

  							 virt_len);

  	if (rc) {

  		printk(KERN_ERR "%s: Error writing metadata out to lower file; "

  		       "rc = [%d]
  ", __func__, rc);

  		goto out_free;

  	}

  out_free:

  	free_pages((unsigned long)virt, order);

  out:
  	return rc;
  }

  #define ECRYPTFS_DONT_VALIDATE_HEADER_SIZE 0
  #define ECRYPTFS_VALIDATE_HEADER_SIZE 1

  static int parse_header_metadata(struct ecryptfs_crypt_stat *crypt_stat,

  				 char *virt, int *bytes_read,
  				 int validate_header_size)

  {
  	int rc = 0;
  	u32 header_extent_size;
  	u16 num_header_extents_at_front;

  	header_extent_size = get_unaligned_be32(virt);
  	virt += sizeof(__be32);
  	num_header_extents_at_front = get_unaligned_be16(virt);

  	crypt_stat->metadata_size = (((size_t)num_header_extents_at_front
  				     * (size_t)header_extent_size));

  	(*bytes_read) = (sizeof(__be32) + sizeof(__be16));

  	if ((validate_header_size == ECRYPTFS_VALIDATE_HEADER_SIZE)

  	    && (crypt_stat->metadata_size

  		< ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE)) {

  		rc = -EINVAL;

  		printk(KERN_WARNING "Invalid header size: [%zd]
  ",

  		       crypt_stat->metadata_size);

  	}
  	return rc;
  }
  
  /**
   * set_default_header_data

   * @crypt_stat: The cryptographic context

   *
   * For version 0 file format; this function is only for backwards
   * compatibility for files created with the prior versions of
   * eCryptfs.
   */
  static void set_default_header_data(struct ecryptfs_crypt_stat *crypt_stat)
  {

  	crypt_stat->metadata_size = ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;

  }

  void ecryptfs_i_size_init(const char *page_virt, struct inode *inode)
  {
  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
  	struct ecryptfs_crypt_stat *crypt_stat;
  	u64 file_size;
  
  	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
  	mount_crypt_stat =
  		&ecryptfs_superblock_to_private(inode->i_sb)->mount_crypt_stat;
  	if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED) {
  		file_size = i_size_read(ecryptfs_inode_to_lower(inode));
  		if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
  			file_size += crypt_stat->metadata_size;
  	} else
  		file_size = get_unaligned_be64(page_virt);
  	i_size_write(inode, (loff_t)file_size);
  	crypt_stat->flags |= ECRYPTFS_I_SIZE_INITIALIZED;
  }

  /**
   * ecryptfs_read_headers_virt

   * @page_virt: The virtual address into which to read the headers
   * @crypt_stat: The cryptographic context
   * @ecryptfs_dentry: The eCryptfs dentry
   * @validate_header_size: Whether to validate the header size while reading

   *
   * Read/parse the header data. The header format is detailed in the
   * comment block for the ecryptfs_write_headers_virt() function.
   *
   * Returns zero on success
   */
  static int ecryptfs_read_headers_virt(char *page_virt,
  				      struct ecryptfs_crypt_stat *crypt_stat,

  				      struct dentry *ecryptfs_dentry,
  				      int validate_header_size)

  {
  	int rc = 0;
  	int offset;
  	int bytes_read;
  
  	ecryptfs_set_default_sizes(crypt_stat);
  	crypt_stat->mount_crypt_stat = &ecryptfs_superblock_to_private(
  		ecryptfs_dentry->d_sb)->mount_crypt_stat;
  	offset = ECRYPTFS_FILE_SIZE_BYTES;

  	rc = ecryptfs_validate_marker(page_virt + offset);
  	if (rc)

  		goto out;

  	if (!(crypt_stat->flags & ECRYPTFS_I_SIZE_INITIALIZED))
  		ecryptfs_i_size_init(page_virt, ecryptfs_dentry->d_inode);

  	offset += MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
  	rc = ecryptfs_process_flags(crypt_stat, (page_virt + offset),
  				    &bytes_read);
  	if (rc) {
  		ecryptfs_printk(KERN_WARNING, "Error processing flags
  ");
  		goto out;
  	}
  	if (crypt_stat->file_version > ECRYPTFS_SUPPORTED_FILE_VERSION) {
  		ecryptfs_printk(KERN_WARNING, "File version is [%d]; only "
  				"file version [%d] is supported by this "
  				"version of eCryptfs
  ",
  				crypt_stat->file_version,
  				ECRYPTFS_SUPPORTED_FILE_VERSION);
  		rc = -EINVAL;
  		goto out;
  	}
  	offset += bytes_read;
  	if (crypt_stat->file_version >= 1) {
  		rc = parse_header_metadata(crypt_stat, (page_virt + offset),

  					   &bytes_read, validate_header_size);

  		if (rc) {
  			ecryptfs_printk(KERN_WARNING, "Error reading header "
  					"metadata; rc = [%d]
  ", rc);
  		}
  		offset += bytes_read;
  	} else
  		set_default_header_data(crypt_stat);
  	rc = ecryptfs_parse_packet_set(crypt_stat, (page_virt + offset),
  				       ecryptfs_dentry);
  out:
  	return rc;
  }
  
  /**

   * ecryptfs_read_xattr_region

   * @page_virt: The vitual address into which to read the xattr data

   * @ecryptfs_inode: The eCryptfs inode

   *
   * Attempts to read the crypto metadata from the extended attribute
   * region of the lower file.

   *
   * Returns zero on success; non-zero on error

   */

  int ecryptfs_read_xattr_region(char *page_virt, struct inode *ecryptfs_inode)

  {

  	struct dentry *lower_dentry =
  		ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;

  	ssize_t size;
  	int rc = 0;

  	size = ecryptfs_getxattr_lower(lower_dentry, ECRYPTFS_XATTR_NAME,
  				       page_virt, ECRYPTFS_DEFAULT_EXTENT_SIZE);

  	if (size < 0) {

  		if (unlikely(ecryptfs_verbosity > 0))
  			printk(KERN_INFO "Error attempting to read the [%s] "
  			       "xattr from the lower file; return value = "
  			       "[%zd]
  ", ECRYPTFS_XATTR_NAME, size);

  		rc = -EINVAL;
  		goto out;
  	}
  out:
  	return rc;
  }

  int ecryptfs_read_and_validate_xattr_region(struct dentry *dentry,

  					    struct inode *inode)

  {

  	u8 file_size[ECRYPTFS_SIZE_AND_MARKER_BYTES];
  	u8 *marker = file_size + ECRYPTFS_FILE_SIZE_BYTES;

  	int rc;

  	rc = ecryptfs_getxattr_lower(ecryptfs_dentry_to_lower(dentry),
  				     ECRYPTFS_XATTR_NAME, file_size,
  				     ECRYPTFS_SIZE_AND_MARKER_BYTES);
  	if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
  		return rc >= 0 ? -EINVAL : rc;
  	rc = ecryptfs_validate_marker(marker);
  	if (!rc)
  		ecryptfs_i_size_init(file_size, inode);

  	return rc;
  }
  
  /**
   * ecryptfs_read_metadata
   *
   * Common entry point for reading file metadata. From here, we could
   * retrieve the header information from the header region of the file,
   * the xattr region of the file, or some other repostory that is
   * stored separately from the file itself. The current implementation
   * supports retrieving the metadata information from the file contents
   * and from the xattr region.

   *
   * Returns zero if valid headers found and parsed; non-zero otherwise
   */

  int ecryptfs_read_metadata(struct dentry *ecryptfs_dentry)

  {
  	int rc = 0;
  	char *page_virt = NULL;

  	struct inode *ecryptfs_inode = ecryptfs_dentry->d_inode;

  	struct ecryptfs_crypt_stat *crypt_stat =

  	    &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;

  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
  		&ecryptfs_superblock_to_private(
  			ecryptfs_dentry->d_sb)->mount_crypt_stat;

  	ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
  						      mount_crypt_stat);

  	/* Read the first page from the underlying file */

  	page_virt = kmem_cache_alloc(ecryptfs_header_cache, GFP_USER);

  	if (!page_virt) {
  		rc = -ENOMEM;

  		printk(KERN_ERR "%s: Unable to allocate page_virt
  ",

  		       __func__);

  		goto out;
  	}

  	rc = ecryptfs_read_lower(page_virt, 0, crypt_stat->extent_size,
  				 ecryptfs_inode);

  	if (rc >= 0)

  		rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
  						ecryptfs_dentry,
  						ECRYPTFS_VALIDATE_HEADER_SIZE);

  	if (rc) {

  		memset(page_virt, 0, PAGE_CACHE_SIZE);

  		rc = ecryptfs_read_xattr_region(page_virt, ecryptfs_inode);

  		if (rc) {
  			printk(KERN_DEBUG "Valid eCryptfs headers not found in "
  			       "file header region or xattr region
  ");
  			rc = -EINVAL;
  			goto out;
  		}
  		rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
  						ecryptfs_dentry,
  						ECRYPTFS_DONT_VALIDATE_HEADER_SIZE);
  		if (rc) {
  			printk(KERN_DEBUG "Valid eCryptfs headers not found in "
  			       "file xattr region either
  ");
  			rc = -EINVAL;
  		}
  		if (crypt_stat->mount_crypt_stat->flags
  		    & ECRYPTFS_XATTR_METADATA_ENABLED) {
  			crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
  		} else {
  			printk(KERN_WARNING "Attempt to access file with "
  			       "crypto metadata only in the extended attribute "
  			       "region, but eCryptfs was mounted without "
  			       "xattr support enabled. eCryptfs will not treat "
  			       "this like an encrypted file.
  ");
  			rc = -EINVAL;
  		}

  	}
  out:
  	if (page_virt) {
  		memset(page_virt, 0, PAGE_CACHE_SIZE);

  		kmem_cache_free(ecryptfs_header_cache, page_virt);

  	}
  	return rc;
  }
  
  /**

   * ecryptfs_encrypt_filename - encrypt filename
   *
   * CBC-encrypts the filename. We do not want to encrypt the same
   * filename with the same key and IV, which may happen with hard
   * links, so we prepend random bits to each filename.
   *
   * Returns zero on success; non-zero otherwise
   */
  static int
  ecryptfs_encrypt_filename(struct ecryptfs_filename *filename,
  			  struct ecryptfs_crypt_stat *crypt_stat,
  			  struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
  {
  	int rc = 0;
  
  	filename->encrypted_filename = NULL;
  	filename->encrypted_filename_size = 0;
  	if ((crypt_stat && (crypt_stat->flags & ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
  	    || (mount_crypt_stat && (mount_crypt_stat->flags
  				     & ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK))) {
  		size_t packet_size;
  		size_t remaining_bytes;
  
  		rc = ecryptfs_write_tag_70_packet(
  			NULL, NULL,
  			&filename->encrypted_filename_size,
  			mount_crypt_stat, NULL,
  			filename->filename_size);
  		if (rc) {
  			printk(KERN_ERR "%s: Error attempting to get packet "
  			       "size for tag 72; rc = [%d]
  ", __func__,
  			       rc);
  			filename->encrypted_filename_size = 0;
  			goto out;
  		}
  		filename->encrypted_filename =
  			kmalloc(filename->encrypted_filename_size, GFP_KERNEL);
  		if (!filename->encrypted_filename) {
  			printk(KERN_ERR "%s: Out of memory whilst attempting "

  			       "to kmalloc [%zd] bytes
  ", __func__,

  			       filename->encrypted_filename_size);
  			rc = -ENOMEM;
  			goto out;
  		}
  		remaining_bytes = filename->encrypted_filename_size;
  		rc = ecryptfs_write_tag_70_packet(filename->encrypted_filename,
  						  &remaining_bytes,
  						  &packet_size,
  						  mount_crypt_stat,
  						  filename->filename,
  						  filename->filename_size);
  		if (rc) {
  			printk(KERN_ERR "%s: Error attempting to generate "
  			       "tag 70 packet; rc = [%d]
  ", __func__,
  			       rc);
  			kfree(filename->encrypted_filename);
  			filename->encrypted_filename = NULL;
  			filename->encrypted_filename_size = 0;
  			goto out;
  		}
  		filename->encrypted_filename_size = packet_size;
  	} else {
  		printk(KERN_ERR "%s: No support for requested filename "
  		       "encryption method in this release
  ", __func__);

  		rc = -EOPNOTSUPP;

  		goto out;
  	}
  out:
  	return rc;
  }
  
  static int ecryptfs_copy_filename(char **copied_name, size_t *copied_name_size,
  				  const char *name, size_t name_size)
  {
  	int rc = 0;

  	(*copied_name) = kmalloc((name_size + 1), GFP_KERNEL);

  	if (!(*copied_name)) {
  		rc = -ENOMEM;
  		goto out;
  	}
  	memcpy((void *)(*copied_name), (void *)name, name_size);
  	(*copied_name)[(name_size)] = '\0';	/* Only for convenience
  						 * in printing out the
  						 * string in debug
  						 * messages */

  	(*copied_name_size) = name_size;

  out:
  	return rc;
  }
  
  /**

   * ecryptfs_process_key_cipher - Perform key cipher initialization.

   * @key_tfm: Crypto context for key material, set by this function

   * @cipher_name: Name of the cipher
   * @key_size: Size of the key in bytes

   *
   * Returns zero on success. Any crypto_tfm structs allocated here
   * should be released by other functions, such as on a superblock put
   * event, regardless of whether this function succeeds for fails.
   */

  static int

  ecryptfs_process_key_cipher(struct crypto_blkcipher **key_tfm,
  			    char *cipher_name, size_t *key_size)

  {
  	char dummy_key[ECRYPTFS_MAX_KEY_BYTES];

  	char *full_alg_name = NULL;

  	int rc;

  	*key_tfm = NULL;
  	if (*key_size > ECRYPTFS_MAX_KEY_BYTES) {

  		rc = -EINVAL;

  		printk(KERN_ERR "Requested key size is [%zd] bytes; maximum "

  		      "allowable is [%d]
  ", *key_size, ECRYPTFS_MAX_KEY_BYTES);

  		goto out;
  	}

  	rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name, cipher_name,
  						    "ecb");
  	if (rc)
  		goto out;
  	*key_tfm = crypto_alloc_blkcipher(full_alg_name, 0, CRYPTO_ALG_ASYNC);

  	if (IS_ERR(*key_tfm)) {
  		rc = PTR_ERR(*key_tfm);

  		printk(KERN_ERR "Unable to allocate crypto cipher with name "

  		       "[%s]; rc = [%d]
  ", full_alg_name, rc);

  		goto out;
  	}

  	crypto_blkcipher_set_flags(*key_tfm, CRYPTO_TFM_REQ_WEAK_KEY);
  	if (*key_size == 0) {
  		struct blkcipher_alg *alg = crypto_blkcipher_alg(*key_tfm);
  
  		*key_size = alg->max_keysize;
  	}

  	get_random_bytes(dummy_key, *key_size);

  	rc = crypto_blkcipher_setkey(*key_tfm, dummy_key, *key_size);

  	if (rc) {

  		printk(KERN_ERR "Error attempting to set key of size [%zd] for "

  		       "cipher [%s]; rc = [%d]
  ", *key_size, full_alg_name,
  		       rc);

  		rc = -EINVAL;
  		goto out;
  	}
  out:

  	kfree(full_alg_name);

  	return rc;
  }

  
  struct kmem_cache *ecryptfs_key_tfm_cache;

  static struct list_head key_tfm_list;

  struct mutex key_tfm_list_mutex;

  int __init ecryptfs_init_crypto(void)

  {
  	mutex_init(&key_tfm_list_mutex);
  	INIT_LIST_HEAD(&key_tfm_list);
  	return 0;
  }

  /**
   * ecryptfs_destroy_crypto - free all cached key_tfms on key_tfm_list
   *
   * Called only at module unload time
   */

  int ecryptfs_destroy_crypto(void)

  {
  	struct ecryptfs_key_tfm *key_tfm, *key_tfm_tmp;
  
  	mutex_lock(&key_tfm_list_mutex);
  	list_for_each_entry_safe(key_tfm, key_tfm_tmp, &key_tfm_list,
  				 key_tfm_list) {
  		list_del(&key_tfm->key_tfm_list);
  		if (key_tfm->key_tfm)
  			crypto_free_blkcipher(key_tfm->key_tfm);
  		kmem_cache_free(ecryptfs_key_tfm_cache, key_tfm);
  	}
  	mutex_unlock(&key_tfm_list_mutex);
  	return 0;
  }
  
  int
  ecryptfs_add_new_key_tfm(struct ecryptfs_key_tfm **key_tfm, char *cipher_name,
  			 size_t key_size)
  {
  	struct ecryptfs_key_tfm *tmp_tfm;
  	int rc = 0;

  	BUG_ON(!mutex_is_locked(&key_tfm_list_mutex));

  	tmp_tfm = kmem_cache_alloc(ecryptfs_key_tfm_cache, GFP_KERNEL);
  	if (key_tfm != NULL)
  		(*key_tfm) = tmp_tfm;
  	if (!tmp_tfm) {
  		rc = -ENOMEM;
  		printk(KERN_ERR "Error attempting to allocate from "
  		       "ecryptfs_key_tfm_cache
  ");
  		goto out;
  	}
  	mutex_init(&tmp_tfm->key_tfm_mutex);
  	strncpy(tmp_tfm->cipher_name, cipher_name,
  		ECRYPTFS_MAX_CIPHER_NAME_SIZE);

  	tmp_tfm->cipher_name[ECRYPTFS_MAX_CIPHER_NAME_SIZE] = '\0';

  	tmp_tfm->key_size = key_size;

  	rc = ecryptfs_process_key_cipher(&tmp_tfm->key_tfm,
  					 tmp_tfm->cipher_name,
  					 &tmp_tfm->key_size);
  	if (rc) {

  		printk(KERN_ERR "Error attempting to initialize key TFM "
  		       "cipher with name = [%s]; rc = [%d]
  ",
  		       tmp_tfm->cipher_name, rc);
  		kmem_cache_free(ecryptfs_key_tfm_cache, tmp_tfm);
  		if (key_tfm != NULL)
  			(*key_tfm) = NULL;
  		goto out;
  	}

  	list_add(&tmp_tfm->key_tfm_list, &key_tfm_list);

  out:
  	return rc;
  }

  /**
   * ecryptfs_tfm_exists - Search for existing tfm for cipher_name.
   * @cipher_name: the name of the cipher to search for
   * @key_tfm: set to corresponding tfm if found
   *
   * Searches for cached key_tfm matching @cipher_name
   * Must be called with &key_tfm_list_mutex held
   * Returns 1 if found, with @key_tfm set
   * Returns 0 if not found, with @key_tfm set to NULL
   */
  int ecryptfs_tfm_exists(char *cipher_name, struct ecryptfs_key_tfm **key_tfm)
  {
  	struct ecryptfs_key_tfm *tmp_key_tfm;
  
  	BUG_ON(!mutex_is_locked(&key_tfm_list_mutex));
  
  	list_for_each_entry(tmp_key_tfm, &key_tfm_list, key_tfm_list) {
  		if (strcmp(tmp_key_tfm->cipher_name, cipher_name) == 0) {
  			if (key_tfm)
  				(*key_tfm) = tmp_key_tfm;
  			return 1;
  		}
  	}
  	if (key_tfm)
  		(*key_tfm) = NULL;
  	return 0;
  }
  
  /**
   * ecryptfs_get_tfm_and_mutex_for_cipher_name
   *
   * @tfm: set to cached tfm found, or new tfm created
   * @tfm_mutex: set to mutex for cached tfm found, or new tfm created
   * @cipher_name: the name of the cipher to search for and/or add
   *
   * Sets pointers to @tfm & @tfm_mutex matching @cipher_name.
   * Searches for cached item first, and creates new if not found.
   * Returns 0 on success, non-zero if adding new cipher failed
   */

  int ecryptfs_get_tfm_and_mutex_for_cipher_name(struct crypto_blkcipher **tfm,
  					       struct mutex **tfm_mutex,
  					       char *cipher_name)
  {
  	struct ecryptfs_key_tfm *key_tfm;
  	int rc = 0;
  
  	(*tfm) = NULL;
  	(*tfm_mutex) = NULL;

  	mutex_lock(&key_tfm_list_mutex);

  	if (!ecryptfs_tfm_exists(cipher_name, &key_tfm)) {
  		rc = ecryptfs_add_new_key_tfm(&key_tfm, cipher_name, 0);
  		if (rc) {
  			printk(KERN_ERR "Error adding new key_tfm to list; "
  					"rc = [%d]
  ", rc);

  			goto out;
  		}
  	}

  	(*tfm) = key_tfm->key_tfm;
  	(*tfm_mutex) = &key_tfm->key_tfm_mutex;
  out:

  	mutex_unlock(&key_tfm_list_mutex);

  	return rc;
  }

  
  /* 64 characters forming a 6-bit target field */
  static unsigned char *portable_filename_chars = ("-.0123456789ABCD"
  						 "EFGHIJKLMNOPQRST"
  						 "UVWXYZabcdefghij"
  						 "klmnopqrstuvwxyz");
  
  /* We could either offset on every reverse map or just pad some 0x00's
   * at the front here */

  static const unsigned char filename_rev_map[256] = {

  	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 7 */
  	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 15 */
  	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 23 */
  	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 31 */
  	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 39 */
  	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* 47 */
  	0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, /* 55 */
  	0x0A, 0x0B, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 63 */
  	0x00, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, /* 71 */
  	0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, /* 79 */
  	0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, /* 87 */
  	0x23, 0x24, 0x25, 0x00, 0x00, 0x00, 0x00, 0x00, /* 95 */
  	0x00, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, /* 103 */
  	0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, /* 111 */
  	0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, /* 119 */

  	0x3D, 0x3E, 0x3F /* 123 - 255 initialized to 0x00 */

  };
  
  /**
   * ecryptfs_encode_for_filename
   * @dst: Destination location for encoded filename
   * @dst_size: Size of the encoded filename in bytes
   * @src: Source location for the filename to encode
   * @src_size: Size of the source in bytes
   */
  void ecryptfs_encode_for_filename(unsigned char *dst, size_t *dst_size,
  				  unsigned char *src, size_t src_size)
  {
  	size_t num_blocks;
  	size_t block_num = 0;
  	size_t dst_offset = 0;
  	unsigned char last_block[3];
  
  	if (src_size == 0) {
  		(*dst_size) = 0;
  		goto out;
  	}
  	num_blocks = (src_size / 3);
  	if ((src_size % 3) == 0) {
  		memcpy(last_block, (&src[src_size - 3]), 3);
  	} else {
  		num_blocks++;
  		last_block[2] = 0x00;
  		switch (src_size % 3) {
  		case 1:
  			last_block[0] = src[src_size - 1];
  			last_block[1] = 0x00;
  			break;
  		case 2:
  			last_block[0] = src[src_size - 2];
  			last_block[1] = src[src_size - 1];
  		}
  	}
  	(*dst_size) = (num_blocks * 4);
  	if (!dst)
  		goto out;
  	while (block_num < num_blocks) {
  		unsigned char *src_block;
  		unsigned char dst_block[4];
  
  		if (block_num == (num_blocks - 1))
  			src_block = last_block;
  		else
  			src_block = &src[block_num * 3];
  		dst_block[0] = ((src_block[0] >> 2) & 0x3F);
  		dst_block[1] = (((src_block[0] << 4) & 0x30)
  				| ((src_block[1] >> 4) & 0x0F));
  		dst_block[2] = (((src_block[1] << 2) & 0x3C)
  				| ((src_block[2] >> 6) & 0x03));
  		dst_block[3] = (src_block[2] & 0x3F);
  		dst[dst_offset++] = portable_filename_chars[dst_block[0]];
  		dst[dst_offset++] = portable_filename_chars[dst_block[1]];
  		dst[dst_offset++] = portable_filename_chars[dst_block[2]];
  		dst[dst_offset++] = portable_filename_chars[dst_block[3]];
  		block_num++;
  	}
  out:
  	return;
  }

  /**
   * ecryptfs_decode_from_filename
   * @dst: If NULL, this function only sets @dst_size and returns. If
   *       non-NULL, this function decodes the encoded octets in @src
   *       into the memory that @dst points to.
   * @dst_size: Set to the size of the decoded string.
   * @src: The encoded set of octets to decode.
   * @src_size: The size of the encoded set of octets to decode.
   */
  static void
  ecryptfs_decode_from_filename(unsigned char *dst, size_t *dst_size,
  			      const unsigned char *src, size_t src_size)

  {
  	u8 current_bit_offset = 0;
  	size_t src_byte_offset = 0;
  	size_t dst_byte_offset = 0;

  
  	if (dst == NULL) {

  		/* Not exact; conservatively long. Every block of 4
  		 * encoded characters decodes into a block of 3
  		 * decoded characters. This segment of code provides
  		 * the caller with the maximum amount of allocated
  		 * space that @dst will need to point to in a
  		 * subsequent call. */

  		(*dst_size) = (((src_size + 1) * 3) / 4);
  		goto out;
  	}
  	while (src_byte_offset < src_size) {
  		unsigned char src_byte =
  				filename_rev_map[(int)src[src_byte_offset]];
  
  		switch (current_bit_offset) {
  		case 0:
  			dst[dst_byte_offset] = (src_byte << 2);
  			current_bit_offset = 6;
  			break;
  		case 6:
  			dst[dst_byte_offset++] |= (src_byte >> 4);
  			dst[dst_byte_offset] = ((src_byte & 0xF)
  						 << 4);
  			current_bit_offset = 4;
  			break;
  		case 4:
  			dst[dst_byte_offset++] |= (src_byte >> 2);
  			dst[dst_byte_offset] = (src_byte << 6);
  			current_bit_offset = 2;
  			break;
  		case 2:
  			dst[dst_byte_offset++] |= (src_byte);
  			dst[dst_byte_offset] = 0;
  			current_bit_offset = 0;
  			break;
  		}
  		src_byte_offset++;
  	}
  	(*dst_size) = dst_byte_offset;
  out:

  	return;

  }
  
  /**
   * ecryptfs_encrypt_and_encode_filename - converts a plaintext file name to cipher text
   * @crypt_stat: The crypt_stat struct associated with the file anem to encode
   * @name: The plaintext name
   * @length: The length of the plaintext
   * @encoded_name: The encypted name
   *
   * Encrypts and encodes a filename into something that constitutes a
   * valid filename for a filesystem, with printable characters.
   *
   * We assume that we have a properly initialized crypto context,
   * pointed to by crypt_stat->tfm.
   *
   * Returns zero on success; non-zero on otherwise
   */
  int ecryptfs_encrypt_and_encode_filename(
  	char **encoded_name,
  	size_t *encoded_name_size,
  	struct ecryptfs_crypt_stat *crypt_stat,
  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat,
  	const char *name, size_t name_size)
  {
  	size_t encoded_name_no_prefix_size;
  	int rc = 0;
  
  	(*encoded_name) = NULL;
  	(*encoded_name_size) = 0;
  	if ((crypt_stat && (crypt_stat->flags & ECRYPTFS_ENCRYPT_FILENAMES))
  	    || (mount_crypt_stat && (mount_crypt_stat->flags
  				     & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES))) {
  		struct ecryptfs_filename *filename;
  
  		filename = kzalloc(sizeof(*filename), GFP_KERNEL);
  		if (!filename) {
  			printk(KERN_ERR "%s: Out of memory whilst attempting "

  			       "to kzalloc [%zd] bytes
  ", __func__,

  			       sizeof(*filename));
  			rc = -ENOMEM;
  			goto out;
  		}
  		filename->filename = (char *)name;
  		filename->filename_size = name_size;
  		rc = ecryptfs_encrypt_filename(filename, crypt_stat,
  					       mount_crypt_stat);
  		if (rc) {
  			printk(KERN_ERR "%s: Error attempting to encrypt "
  			       "filename; rc = [%d]
  ", __func__, rc);
  			kfree(filename);
  			goto out;
  		}
  		ecryptfs_encode_for_filename(
  			NULL, &encoded_name_no_prefix_size,
  			filename->encrypted_filename,
  			filename->encrypted_filename_size);
  		if ((crypt_stat && (crypt_stat->flags
  				    & ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
  		    || (mount_crypt_stat
  			&& (mount_crypt_stat->flags
  			    & ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK)))
  			(*encoded_name_size) =
  				(ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE
  				 + encoded_name_no_prefix_size);
  		else
  			(*encoded_name_size) =
  				(ECRYPTFS_FEK_ENCRYPTED_FILENAME_PREFIX_SIZE
  				 + encoded_name_no_prefix_size);
  		(*encoded_name) = kmalloc((*encoded_name_size) + 1, GFP_KERNEL);
  		if (!(*encoded_name)) {
  			printk(KERN_ERR "%s: Out of memory whilst attempting "

  			       "to kzalloc [%zd] bytes
  ", __func__,

  			       (*encoded_name_size));
  			rc = -ENOMEM;
  			kfree(filename->encrypted_filename);
  			kfree(filename);
  			goto out;
  		}
  		if ((crypt_stat && (crypt_stat->flags
  				    & ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
  		    || (mount_crypt_stat
  			&& (mount_crypt_stat->flags
  			    & ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK))) {
  			memcpy((*encoded_name),
  			       ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
  			       ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE);
  			ecryptfs_encode_for_filename(
  			    ((*encoded_name)
  			     + ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE),
  			    &encoded_name_no_prefix_size,
  			    filename->encrypted_filename,
  			    filename->encrypted_filename_size);
  			(*encoded_name_size) =
  				(ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE
  				 + encoded_name_no_prefix_size);
  			(*encoded_name)[(*encoded_name_size)] = '\0';

  		} else {

  			rc = -EOPNOTSUPP;

  		}
  		if (rc) {
  			printk(KERN_ERR "%s: Error attempting to encode "
  			       "encrypted filename; rc = [%d]
  ", __func__,
  			       rc);
  			kfree((*encoded_name));
  			(*encoded_name) = NULL;
  			(*encoded_name_size) = 0;
  		}
  		kfree(filename->encrypted_filename);
  		kfree(filename);
  	} else {
  		rc = ecryptfs_copy_filename(encoded_name,
  					    encoded_name_size,
  					    name, name_size);
  	}
  out:
  	return rc;
  }
  
  /**
   * ecryptfs_decode_and_decrypt_filename - converts the encoded cipher text name to decoded plaintext
   * @plaintext_name: The plaintext name
   * @plaintext_name_size: The plaintext name size
   * @ecryptfs_dir_dentry: eCryptfs directory dentry
   * @name: The filename in cipher text
   * @name_size: The cipher text name size
   *
   * Decrypts and decodes the filename.
   *
   * Returns zero on error; non-zero otherwise
   */
  int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,
  					 size_t *plaintext_name_size,
  					 struct dentry *ecryptfs_dir_dentry,
  					 const char *name, size_t name_size)
  {

  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
  		&ecryptfs_superblock_to_private(
  			ecryptfs_dir_dentry->d_sb)->mount_crypt_stat;

  	char *decoded_name;
  	size_t decoded_name_size;
  	size_t packet_size;
  	int rc = 0;

  	if ((mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)
  	    && !(mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
  	    && (name_size > ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE)

  	    && (strncmp(name, ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
  			ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE) == 0)) {

  		const char *orig_name = name;
  		size_t orig_name_size = name_size;
  
  		name += ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
  		name_size -= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;

  		ecryptfs_decode_from_filename(NULL, &decoded_name_size,
  					      name, name_size);

  		decoded_name = kmalloc(decoded_name_size, GFP_KERNEL);
  		if (!decoded_name) {
  			printk(KERN_ERR "%s: Out of memory whilst attempting "

  			       "to kmalloc [%zd] bytes
  ", __func__,

  			       decoded_name_size);
  			rc = -ENOMEM;
  			goto out;
  		}

  		ecryptfs_decode_from_filename(decoded_name, &decoded_name_size,
  					      name, name_size);

  		rc = ecryptfs_parse_tag_70_packet(plaintext_name,
  						  plaintext_name_size,
  						  &packet_size,
  						  mount_crypt_stat,
  						  decoded_name,
  						  decoded_name_size);
  		if (rc) {
  			printk(KERN_INFO "%s: Could not parse tag 70 packet "
  			       "from filename; copying through filename "
  			       "as-is
  ", __func__);
  			rc = ecryptfs_copy_filename(plaintext_name,
  						    plaintext_name_size,
  						    orig_name, orig_name_size);
  			goto out_free;
  		}
  	} else {
  		rc = ecryptfs_copy_filename(plaintext_name,
  					    plaintext_name_size,
  					    name, name_size);
  		goto out;
  	}
  out_free:
  	kfree(decoded_name);
  out:
  	return rc;
  }