crypto.c

/**
 * 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"

#define DECRYPT		0
#define ENCRYPT		1

static int crypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
			     struct page *dst_page, struct page *src_page,
			     int offset, int size, unsigned char *iv, int op);

/**
 * 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]\n",
					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]\n",
		       __func__, rc);
		goto out;
	}
	rc = crypto_hash_update(&desc, &sg, len);
	if (rc) {
		printk(KERN_ERR
		       "%s: Error updating crypto hash; rc = [%d]\n",
		       __func__, rc);
		goto out;
	}
	rc = crypto_hash_final(&desc, dst);
	if (rc) {
		printk(KERN_ERR
		       "%s: Error finalizing crypto hash; rc = [%d]\n",
		       __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:\n");
		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:\n");
		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\n");
		goto out;
	}
	memcpy(iv, dst, crypt_stat->iv_bytes);
	if (unlikely(ecryptfs_verbosity > 0)) {
		ecryptfs_printk(KERN_DEBUG, "derived iv:\n");
		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_ablkcipher(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);
		sg_set_page(&sg[i], pg, 0, offset);
		remainder_of_page = PAGE_CACHE_SIZE - offset;
		if (size >= remainder_of_page) {
			sg[i].length = remainder_of_page;
			addr += remainder_of_page;
			size -= remainder_of_page;
		} else {
			sg[i].length = size;
			addr += size;
			size = 0;
		}
		i++;
	}
	if (size > 0)
		return -ENOMEM;
	return i;
}

struct extent_crypt_result {
	struct completion completion;
	int rc;
};

static void extent_crypt_complete(struct crypto_async_request *req, int rc)
{
	struct extent_crypt_result *ecr = req->data;

	if (rc == -EINPROGRESS)
		return;

	ecr->rc = rc;
	complete(&ecr->completion);
}

/**
 * crypt_scatterlist
 * @crypt_stat: Pointer to the crypt_stat struct to initialize.
 * @dest_sg: Destination of the data after performing the crypto operation
 * @src_sg: Data to be encrypted or decrypted
 * @size: Length of data
 * @iv: IV to use
 * @op: ENCRYPT or DECRYPT to indicate the desired operation
 *
 * Returns the number of bytes encrypted or decrypted; negative value on error
 */
static int crypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
			     struct scatterlist *dest_sg,
			     struct scatterlist *src_sg, int size,
			     unsigned char *iv, int op)
{
	struct ablkcipher_request *req = NULL;
	struct extent_crypt_result ecr;
	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:\n",
				crypt_stat->key_size);
		ecryptfs_dump_hex(crypt_stat->key,
				  crypt_stat->key_size);
	}

	init_completion(&ecr.completion);

	mutex_lock(&crypt_stat->cs_tfm_mutex);
	req = ablkcipher_request_alloc(crypt_stat->tfm, GFP_NOFS);
	if (!req) {
		mutex_unlock(&crypt_stat->cs_tfm_mutex);
		rc = -ENOMEM;
		goto out;
	}

	ablkcipher_request_set_callback(req,
			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
			extent_crypt_complete, &ecr);
	/* Consider doing this once, when the file is opened */
	if (!(crypt_stat->flags & ECRYPTFS_KEY_SET)) {
		rc = crypto_ablkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
					      crypt_stat->key_size);
		if (rc) {
			ecryptfs_printk(KERN_ERR,
					"Error setting key; rc = [%d]\n",
					rc);
			mutex_unlock(&crypt_stat->cs_tfm_mutex);
			rc = -EINVAL;
			goto out;
		}
		crypt_stat->flags |= ECRYPTFS_KEY_SET;
	}
	mutex_unlock(&crypt_stat->cs_tfm_mutex);
	ablkcipher_request_set_crypt(req, src_sg, dest_sg, size, iv);
	rc = op == ENCRYPT ? crypto_ablkcipher_encrypt(req) :
			     crypto_ablkcipher_decrypt(req);
	if (rc == -EINPROGRESS || rc == -EBUSY) {
		struct extent_crypt_result *ecr = req->base.data;

		wait_for_completion(&ecr->completion);
		rc = ecr->rc;
		INIT_COMPLETION(ecr->completion);
	}
out:
	ablkcipher_request_free(req);
	return rc;
}

/**
 * lower_offset_for_page
 *
 * Convert an eCryptfs page index into a lower byte offset
 */
static loff_t lower_offset_for_page(struct ecryptfs_crypt_stat *crypt_stat,
				    struct page *page)
{
	return ecryptfs_lower_header_size(crypt_stat) +
	       (page->index << PAGE_CACHE_SHIFT);
}

/**
 * crypt_extent
 * @dst_page: The page to write the result into
 * @crypt_stat: crypt_stat containing cryptographic context for the
 *              encryption operation
 * @src_page: The page to read from
 * @extent_offset: Page extent offset for use in generating IV
 * @op: ENCRYPT or DECRYPT to indicate the desired operation
 *
 * Encrypts or decrypts one extent of data.
 *
 * Return zero on success; non-zero otherwise
 */
static int crypt_extent(struct page *dst_page,
			struct ecryptfs_crypt_stat *crypt_stat,
			struct page *src_page,
			unsigned long extent_offset, int op)
{
	pgoff_t page_index = op == ENCRYPT ? src_page->index : dst_page->index;
	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]\n",
			(unsigned long long)(extent_base + extent_offset), rc);
		goto out;
	}
	rc = crypt_page_offset(crypt_stat, dst_page, src_page,
			       (extent_offset * crypt_stat->extent_size),
			       crypt_stat->extent_size, extent_iv, op);
	if (rc < 0) {
		printk(KERN_ERR "%s: Error attempting to crypt page with "
		       "page_index = [%ld], extent_offset = [%ld]; "
		       "rc = [%d]\n", __func__, page_index, extent_offset, rc);
		goto out;
	}
	rc = 0;
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;
	loff_t lower_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\n");
		goto out;
	}

	for (extent_offset = 0;
	     extent_offset < (PAGE_CACHE_SIZE / crypt_stat->extent_size);
	     extent_offset++) {
		rc = crypt_extent(enc_extent_page, crypt_stat, page,
				  extent_offset, ENCRYPT);
		if (rc) {
			printk(KERN_ERR "%s: Error encrypting extent; "
			       "rc = [%d]\n", __func__, rc);
			goto out;
		}
	}

	lower_offset = lower_offset_for_page(crypt_stat, page);
	enc_extent_virt = kmap(enc_extent_page);
	rc = ecryptfs_write_lower(ecryptfs_inode, enc_extent_virt, lower_offset,
				  PAGE_CACHE_SIZE);
	kunmap(enc_extent_page);
	if (rc < 0) {
		ecryptfs_printk(KERN_ERR,
			"Error attempting to write lower page; rc = [%d]\n",
			rc);
		goto out;
	}
	rc = 0;
out:
	if (enc_extent_page) {
		__free_page(enc_extent_page);
	}
	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 *page_virt;
	unsigned long extent_offset;
	loff_t lower_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));

	lower_offset = lower_offset_for_page(crypt_stat, page);
	page_virt = kmap(page);
	rc = ecryptfs_read_lower(page_virt, lower_offset, PAGE_CACHE_SIZE,
				 ecryptfs_inode);
	kunmap(page);
	if (rc < 0) {
		ecryptfs_printk(KERN_ERR,
			"Error attempting to read lower page; rc = [%d]\n",
			rc);
		goto out;
	}

	for (extent_offset = 0;
	     extent_offset < (PAGE_CACHE_SIZE / crypt_stat->extent_size);
	     extent_offset++) {
		rc = crypt_extent(page, crypt_stat, page,
				  extent_offset, DECRYPT);
		if (rc) {
			printk(KERN_ERR "%s: Error encrypting extent; "
			       "rc = [%d]\n", __func__, rc);
			goto out;
		}
	}
out:
	return rc;
}

/**
 * crypt_page_offset
 * @crypt_stat: The cryptographic context
 * @dst_page: The page to write the result into
 * @src_page: The page to read from
 * @offset: The byte offset into the dst_page and src_page
 * @size: The number of bytes of data
 * @iv: The initialization vector to use for the crypto operation
 * @op: ENCRYPT or DECRYPT to indicate the desired operation
 *
 * Returns the number of bytes encrypted or decrypted
 */
static int crypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
			     struct page *dst_page, struct page *src_page,
			     int offset, int size, unsigned char *iv, int op)
{
	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, offset);
	sg_set_page(&dst_sg, dst_page, size, offset);

	return crypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv, op);
}

#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\n");
		goto out;
	}
	ecryptfs_printk(KERN_DEBUG,
			"Initializing cipher [%s]; strlen = [%d]; "
			"key_size_bits = [%zd]\n",
			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_ablkcipher(full_alg_name, 0, 0);
	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]\n",
				crypt_stat->cipher);
		goto out_unlock;
	}
	crypto_ablkcipher_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\n");
		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\n");
		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:\n");
		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]\n", 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]\n", 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]\n",
				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]\n", m_1, m_2,
			MAGIC_ECRYPTFS_MARKER);
	ecryptfs_printk(KERN_DEBUG, "(m_1 ^ MAGIC_ECRYPTFS_MARKER) = "
			"[0x%.8x]\n", (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]\n", 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]\n", 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]\n", __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\n");
			rc = -EINVAL;
			goto out;
		}
	} else {
		printk(KERN_WARNING "%s: Encrypted flag not set\n",
		       __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\n", __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]\n",
		       __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]\n", __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]\n",
		       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\n");
		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\n",
				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]\n", 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]\n", 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;
	char *page_virt;
	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\n",
		       __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) {
		/* metadata is not in the file header, so try xattrs */
		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, inode %lu\n",
				ecryptfs_inode->i_ino);
			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, inode %lu\n",
				ecryptfs_inode->i_ino);
			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, inode %lu\n",
				ecryptfs_inode->i_ino);
			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]\n", __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\n", __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]\n", __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\n", __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]\n", *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]\n", 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]\n", *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\n");
		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]\n",
		       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]\n", 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
 */
static 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;
}

static size_t ecryptfs_max_decoded_size(size_t encoded_size)
{
	/* 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. */
	return ((encoded_size + 1) * 3) / 4;
}

/**
 * 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) {
		(*dst_size) = ecryptfs_max_decoded_size(src_size);
		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\n", __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]\n", __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\n", __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]\n", __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\n", __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\n", __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;
}

#define ENC_NAME_MAX_BLOCKLEN_8_OR_16	143

int ecryptfs_set_f_namelen(long *namelen, long lower_namelen,
			   struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
	struct blkcipher_desc desc;
	struct mutex *tfm_mutex;
	size_t cipher_blocksize;
	int rc;

	if (!(mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
		(*namelen) = lower_namelen;
		return 0;
	}

	rc = ecryptfs_get_tfm_and_mutex_for_cipher_name(&desc.tfm, &tfm_mutex,
			mount_crypt_stat->global_default_fn_cipher_name);
	if (unlikely(rc)) {
		(*namelen) = 0;
		return rc;
	}

	mutex_lock(tfm_mutex);
	cipher_blocksize = crypto_blkcipher_blocksize(desc.tfm);
	mutex_unlock(tfm_mutex);

	/* Return an exact amount for the common cases */
	if (lower_namelen == NAME_MAX
	    && (cipher_blocksize == 8 || cipher_blocksize == 16)) {
		(*namelen) = ENC_NAME_MAX_BLOCKLEN_8_OR_16;
		return 0;
	}

	/* Return a safe estimate for the uncommon cases */
	(*namelen) = lower_namelen;
	(*namelen) -= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
	/* Since this is the max decoded size, subtract 1 "decoded block" len */
	(*namelen) = ecryptfs_max_decoded_size(*namelen) - 3;
	(*namelen) -= ECRYPTFS_TAG_70_MAX_METADATA_SIZE;
	(*namelen) -= ECRYPTFS_FILENAME_MIN_RANDOM_PREPEND_BYTES;
	/* Worst case is that the filename is padded nearly a full block size */
	(*namelen) -= cipher_blocksize - 1;

	if ((*namelen) < 0)
		(*namelen) = 0;

	return 0;
}