/**
   * eCryptfs: Linux filesystem encryption layer
   * In-kernel key management code.  Includes functions to parse and
   * write authentication token-related packets with the underlying
   * file.
   *
   * Copyright (C) 2004-2006 International Business Machines Corp.
   *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
   *              Michael C. Thompson <mcthomps@us.ibm.com>

   *              Trevor S. Highland <trevor.highland@gmail.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/string.h>

  #include <linux/syscalls.h>
  #include <linux/pagemap.h>
  #include <linux/key.h>
  #include <linux/random.h>
  #include <linux/crypto.h>
  #include <linux/scatterlist.h>

  #include <linux/slab.h>

  #include "ecryptfs_kernel.h"
  
  /**
   * request_key returned an error instead of a valid key address;
   * determine the type of error, make appropriate log entries, and
   * return an error code.
   */

  static int process_request_key_err(long err_code)

  {
  	int rc = 0;
  
  	switch (err_code) {

  	case -ENOKEY:

  		ecryptfs_printk(KERN_WARNING, "No key
  ");
  		rc = -ENOENT;
  		break;

  	case -EKEYEXPIRED:

  		ecryptfs_printk(KERN_WARNING, "Key expired
  ");
  		rc = -ETIME;
  		break;

  	case -EKEYREVOKED:

  		ecryptfs_printk(KERN_WARNING, "Key revoked
  ");
  		rc = -EINVAL;
  		break;
  	default:
  		ecryptfs_printk(KERN_WARNING, "Unknown error code: "

  				"[0x%.16lx]
  ", err_code);

  		rc = -EINVAL;
  	}
  	return rc;
  }

  static int process_find_global_auth_tok_for_sig_err(int err_code)
  {
  	int rc = err_code;
  
  	switch (err_code) {
  	case -ENOENT:
  		ecryptfs_printk(KERN_WARNING, "Missing auth tok
  ");
  		break;
  	case -EINVAL:
  		ecryptfs_printk(KERN_WARNING, "Invalid auth tok
  ");
  		break;
  	default:
  		rc = process_request_key_err(err_code);
  		break;
  	}
  	return rc;
  }

  /**

   * ecryptfs_parse_packet_length

   * @data: Pointer to memory containing length at offset
   * @size: This function writes the decoded size to this memory
   *        address; zero on error
   * @length_size: The number of bytes occupied by the encoded length
   *

   * Returns zero on success; non-zero on error

   */

  int ecryptfs_parse_packet_length(unsigned char *data, size_t *size,
  				 size_t *length_size)

  {
  	int rc = 0;
  
  	(*length_size) = 0;
  	(*size) = 0;
  	if (data[0] < 192) {
  		/* One-byte length */

  		(*size) = (unsigned char)data[0];

  		(*length_size) = 1;
  	} else if (data[0] < 224) {
  		/* Two-byte length */

  		(*size) = (((unsigned char)(data[0]) - 192) * 256);
  		(*size) += ((unsigned char)(data[1]) + 192);

  		(*length_size) = 2;
  	} else if (data[0] == 255) {
  		/* Five-byte length; we're not supposed to see this */
  		ecryptfs_printk(KERN_ERR, "Five-byte packet length not "
  				"supported
  ");
  		rc = -EINVAL;
  		goto out;
  	} else {
  		ecryptfs_printk(KERN_ERR, "Error parsing packet length
  ");
  		rc = -EINVAL;
  		goto out;
  	}
  out:
  	return rc;
  }
  
  /**

   * ecryptfs_write_packet_length

   * @dest: The byte array target into which to write the length. Must
   *        have at least 5 bytes allocated.

   * @size: The length to write.

   * @packet_size_length: The number of bytes used to encode the packet
   *                      length is written to this address.

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

  int ecryptfs_write_packet_length(char *dest, size_t size,
  				 size_t *packet_size_length)

  {
  	int rc = 0;
  
  	if (size < 192) {
  		dest[0] = size;
  		(*packet_size_length) = 1;
  	} else if (size < 65536) {
  		dest[0] = (((size - 192) / 256) + 192);
  		dest[1] = ((size - 192) % 256);
  		(*packet_size_length) = 2;
  	} else {
  		rc = -EINVAL;
  		ecryptfs_printk(KERN_WARNING,

  				"Unsupported packet size: [%zd]
  ", size);

  	}
  	return rc;
  }

  static int
  write_tag_64_packet(char *signature, struct ecryptfs_session_key *session_key,
  		    char **packet, size_t *packet_len)
  {
  	size_t i = 0;
  	size_t data_len;
  	size_t packet_size_len;
  	char *message;
  	int rc;
  
  	/*
  	 *              ***** TAG 64 Packet Format *****
  	 *    | Content Type                       | 1 byte       |
  	 *    | Key Identifier Size                | 1 or 2 bytes |
  	 *    | Key Identifier                     | arbitrary    |
  	 *    | Encrypted File Encryption Key Size | 1 or 2 bytes |
  	 *    | Encrypted File Encryption Key      | arbitrary    |
  	 */
  	data_len = (5 + ECRYPTFS_SIG_SIZE_HEX
  		    + session_key->encrypted_key_size);
  	*packet = kmalloc(data_len, GFP_KERNEL);
  	message = *packet;
  	if (!message) {
  		ecryptfs_printk(KERN_ERR, "Unable to allocate memory
  ");
  		rc = -ENOMEM;
  		goto out;
  	}
  	message[i++] = ECRYPTFS_TAG_64_PACKET_TYPE;

  	rc = ecryptfs_write_packet_length(&message[i], ECRYPTFS_SIG_SIZE_HEX,
  					  &packet_size_len);

  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Error generating tag 64 packet "
  				"header; cannot generate packet length
  ");
  		goto out;
  	}
  	i += packet_size_len;
  	memcpy(&message[i], signature, ECRYPTFS_SIG_SIZE_HEX);
  	i += ECRYPTFS_SIG_SIZE_HEX;

  	rc = ecryptfs_write_packet_length(&message[i],
  					  session_key->encrypted_key_size,
  					  &packet_size_len);

  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Error generating tag 64 packet "
  				"header; cannot generate packet length
  ");
  		goto out;
  	}
  	i += packet_size_len;
  	memcpy(&message[i], session_key->encrypted_key,
  	       session_key->encrypted_key_size);
  	i += session_key->encrypted_key_size;
  	*packet_len = i;
  out:
  	return rc;
  }
  
  static int

  parse_tag_65_packet(struct ecryptfs_session_key *session_key, u8 *cipher_code,

  		    struct ecryptfs_message *msg)
  {
  	size_t i = 0;
  	char *data;
  	size_t data_len;
  	size_t m_size;
  	size_t message_len;
  	u16 checksum = 0;
  	u16 expected_checksum = 0;
  	int rc;
  
  	/*
  	 *              ***** TAG 65 Packet Format *****
  	 *         | Content Type             | 1 byte       |
  	 *         | Status Indicator         | 1 byte       |
  	 *         | File Encryption Key Size | 1 or 2 bytes |
  	 *         | File Encryption Key      | arbitrary    |
  	 */
  	message_len = msg->data_len;
  	data = msg->data;
  	if (message_len < 4) {
  		rc = -EIO;
  		goto out;
  	}
  	if (data[i++] != ECRYPTFS_TAG_65_PACKET_TYPE) {
  		ecryptfs_printk(KERN_ERR, "Type should be ECRYPTFS_TAG_65
  ");
  		rc = -EIO;
  		goto out;
  	}
  	if (data[i++]) {
  		ecryptfs_printk(KERN_ERR, "Status indicator has non-zero value "
  				"[%d]
  ", data[i-1]);
  		rc = -EIO;
  		goto out;
  	}

  	rc = ecryptfs_parse_packet_length(&data[i], &m_size, &data_len);

  	if (rc) {
  		ecryptfs_printk(KERN_WARNING, "Error parsing packet length; "
  				"rc = [%d]
  ", rc);
  		goto out;
  	}
  	i += data_len;
  	if (message_len < (i + m_size)) {

  		ecryptfs_printk(KERN_ERR, "The message received from ecryptfsd "
  				"is shorter than expected
  ");

  		rc = -EIO;
  		goto out;
  	}
  	if (m_size < 3) {
  		ecryptfs_printk(KERN_ERR,
  				"The decrypted key is not long enough to "
  				"include a cipher code and checksum
  ");
  		rc = -EIO;
  		goto out;
  	}
  	*cipher_code = data[i++];
  	/* The decrypted key includes 1 byte cipher code and 2 byte checksum */
  	session_key->decrypted_key_size = m_size - 3;
  	if (session_key->decrypted_key_size > ECRYPTFS_MAX_KEY_BYTES) {
  		ecryptfs_printk(KERN_ERR, "key_size [%d] larger than "
  				"the maximum key size [%d]
  ",
  				session_key->decrypted_key_size,
  				ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES);
  		rc = -EIO;
  		goto out;
  	}
  	memcpy(session_key->decrypted_key, &data[i],
  	       session_key->decrypted_key_size);
  	i += session_key->decrypted_key_size;
  	expected_checksum += (unsigned char)(data[i++]) << 8;
  	expected_checksum += (unsigned char)(data[i++]);
  	for (i = 0; i < session_key->decrypted_key_size; i++)
  		checksum += session_key->decrypted_key[i];
  	if (expected_checksum != checksum) {
  		ecryptfs_printk(KERN_ERR, "Invalid checksum for file "
  				"encryption  key; expected [%x]; calculated "
  				"[%x]
  ", expected_checksum, checksum);
  		rc = -EIO;
  	}
  out:
  	return rc;
  }
  
  
  static int

  write_tag_66_packet(char *signature, u8 cipher_code,

  		    struct ecryptfs_crypt_stat *crypt_stat, char **packet,
  		    size_t *packet_len)
  {
  	size_t i = 0;
  	size_t j;
  	size_t data_len;
  	size_t checksum = 0;
  	size_t packet_size_len;
  	char *message;
  	int rc;
  
  	/*
  	 *              ***** TAG 66 Packet Format *****
  	 *         | Content Type             | 1 byte       |
  	 *         | Key Identifier Size      | 1 or 2 bytes |
  	 *         | Key Identifier           | arbitrary    |
  	 *         | File Encryption Key Size | 1 or 2 bytes |
  	 *         | File Encryption Key      | arbitrary    |
  	 */
  	data_len = (5 + ECRYPTFS_SIG_SIZE_HEX + crypt_stat->key_size);
  	*packet = kmalloc(data_len, GFP_KERNEL);
  	message = *packet;
  	if (!message) {
  		ecryptfs_printk(KERN_ERR, "Unable to allocate memory
  ");
  		rc = -ENOMEM;
  		goto out;
  	}
  	message[i++] = ECRYPTFS_TAG_66_PACKET_TYPE;

  	rc = ecryptfs_write_packet_length(&message[i], ECRYPTFS_SIG_SIZE_HEX,
  					  &packet_size_len);

  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Error generating tag 66 packet "
  				"header; cannot generate packet length
  ");
  		goto out;
  	}
  	i += packet_size_len;
  	memcpy(&message[i], signature, ECRYPTFS_SIG_SIZE_HEX);
  	i += ECRYPTFS_SIG_SIZE_HEX;
  	/* The encrypted key includes 1 byte cipher code and 2 byte checksum */

  	rc = ecryptfs_write_packet_length(&message[i], crypt_stat->key_size + 3,
  					  &packet_size_len);

  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Error generating tag 66 packet "
  				"header; cannot generate packet length
  ");
  		goto out;
  	}
  	i += packet_size_len;
  	message[i++] = cipher_code;
  	memcpy(&message[i], crypt_stat->key, crypt_stat->key_size);
  	i += crypt_stat->key_size;
  	for (j = 0; j < crypt_stat->key_size; j++)
  		checksum += crypt_stat->key[j];
  	message[i++] = (checksum / 256) % 256;
  	message[i++] = (checksum % 256);
  	*packet_len = i;
  out:
  	return rc;
  }
  
  static int
  parse_tag_67_packet(struct ecryptfs_key_record *key_rec,
  		    struct ecryptfs_message *msg)
  {
  	size_t i = 0;
  	char *data;
  	size_t data_len;
  	size_t message_len;
  	int rc;
  
  	/*
  	 *              ***** TAG 65 Packet Format *****
  	 *    | Content Type                       | 1 byte       |
  	 *    | Status Indicator                   | 1 byte       |
  	 *    | Encrypted File Encryption Key Size | 1 or 2 bytes |
  	 *    | Encrypted File Encryption Key      | arbitrary    |
  	 */
  	message_len = msg->data_len;
  	data = msg->data;
  	/* verify that everything through the encrypted FEK size is present */
  	if (message_len < 4) {
  		rc = -EIO;

  		printk(KERN_ERR "%s: message_len is [%zd]; minimum acceptable "

  		       "message length is [%d]
  ", __func__, message_len, 4);

  		goto out;
  	}
  	if (data[i++] != ECRYPTFS_TAG_67_PACKET_TYPE) {

  		rc = -EIO;

  		printk(KERN_ERR "%s: Type should be ECRYPTFS_TAG_67
  ",
  		       __func__);

  		goto out;
  	}
  	if (data[i++]) {

  		rc = -EIO;

  		printk(KERN_ERR "%s: Status indicator has non zero "
  		       "value [%d]
  ", __func__, data[i-1]);

  		goto out;
  	}

  	rc = ecryptfs_parse_packet_length(&data[i], &key_rec->enc_key_size,
  					  &data_len);

  	if (rc) {
  		ecryptfs_printk(KERN_WARNING, "Error parsing packet length; "
  				"rc = [%d]
  ", rc);
  		goto out;
  	}
  	i += data_len;
  	if (message_len < (i + key_rec->enc_key_size)) {

  		rc = -EIO;

  		printk(KERN_ERR "%s: message_len [%zd]; max len is [%zd]
  ",

  		       __func__, message_len, (i + key_rec->enc_key_size));

  		goto out;
  	}
  	if (key_rec->enc_key_size > ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES) {

  		rc = -EIO;

  		printk(KERN_ERR "%s: Encrypted key_size [%zd] larger than "

  		       "the maximum key size [%d]
  ", __func__,
  		       key_rec->enc_key_size,
  		       ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES);

  		goto out;
  	}
  	memcpy(key_rec->enc_key, &data[i], key_rec->enc_key_size);
  out:
  	return rc;
  }

  /**
   * ecryptfs_verify_version
   * @version: The version number to confirm
   *
   * Returns zero on good version; non-zero otherwise
   */
  static int ecryptfs_verify_version(u16 version)
  {
  	int rc = 0;
  	unsigned char major;
  	unsigned char minor;
  
  	major = ((version >> 8) & 0xFF);
  	minor = (version & 0xFF);
  	if (major != ECRYPTFS_VERSION_MAJOR) {
  		ecryptfs_printk(KERN_ERR, "Major version number mismatch. "
  				"Expected [%d]; got [%d]
  ",
  				ECRYPTFS_VERSION_MAJOR, major);
  		rc = -EINVAL;
  		goto out;
  	}
  	if (minor != ECRYPTFS_VERSION_MINOR) {
  		ecryptfs_printk(KERN_ERR, "Minor version number mismatch. "
  				"Expected [%d]; got [%d]
  ",
  				ECRYPTFS_VERSION_MINOR, minor);
  		rc = -EINVAL;
  		goto out;
  	}
  out:
  	return rc;
  }
  
  /**
   * ecryptfs_verify_auth_tok_from_key
   * @auth_tok_key: key containing the authentication token
   * @auth_tok: authentication token
   *
   * Returns zero on valid auth tok; -EINVAL otherwise
   */
  static int
  ecryptfs_verify_auth_tok_from_key(struct key *auth_tok_key,
  				  struct ecryptfs_auth_tok **auth_tok)
  {
  	int rc = 0;
  
  	(*auth_tok) = ecryptfs_get_key_payload_data(auth_tok_key);
  	if (ecryptfs_verify_version((*auth_tok)->version)) {
  		printk(KERN_ERR "Data structure version mismatch. Userspace "
  		       "tools must match eCryptfs kernel module with major "
  		       "version [%d] and minor version [%d]
  ",
  		       ECRYPTFS_VERSION_MAJOR, ECRYPTFS_VERSION_MINOR);
  		rc = -EINVAL;
  		goto out;
  	}
  	if ((*auth_tok)->token_type != ECRYPTFS_PASSWORD
  	    && (*auth_tok)->token_type != ECRYPTFS_PRIVATE_KEY) {
  		printk(KERN_ERR "Invalid auth_tok structure "
  		       "returned from key query
  ");
  		rc = -EINVAL;
  		goto out;
  	}
  out:
  	return rc;
  }

  static int

  ecryptfs_find_global_auth_tok_for_sig(

  	struct key **auth_tok_key,
  	struct ecryptfs_auth_tok **auth_tok,

  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat, char *sig)
  {
  	struct ecryptfs_global_auth_tok *walker;
  	int rc = 0;

  	(*auth_tok_key) = NULL;
  	(*auth_tok) = NULL;

  	mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
  	list_for_each_entry(walker,
  			    &mount_crypt_stat->global_auth_tok_list,
  			    mount_crypt_stat_list) {

  		if (memcmp(walker->sig, sig, ECRYPTFS_SIG_SIZE_HEX))
  			continue;
  
  		if (walker->flags & ECRYPTFS_AUTH_TOK_INVALID) {
  			rc = -EINVAL;

  			goto out;
  		}

  
  		rc = key_validate(walker->global_auth_tok_key);
  		if (rc) {
  			if (rc == -EKEYEXPIRED)
  				goto out;
  			goto out_invalid_auth_tok;
  		}

  		down_write(&(walker->global_auth_tok_key->sem));

  		rc = ecryptfs_verify_auth_tok_from_key(
  				walker->global_auth_tok_key, auth_tok);
  		if (rc)

  			goto out_invalid_auth_tok_unlock;

  
  		(*auth_tok_key) = walker->global_auth_tok_key;
  		key_get(*auth_tok_key);
  		goto out;

  	}

  	rc = -ENOENT;
  	goto out;

  out_invalid_auth_tok_unlock:
  	up_write(&(walker->global_auth_tok_key->sem));

  out_invalid_auth_tok:
  	printk(KERN_WARNING "Invalidating auth tok with sig = [%s]
  ", sig);
  	walker->flags |= ECRYPTFS_AUTH_TOK_INVALID;
  	key_put(walker->global_auth_tok_key);
  	walker->global_auth_tok_key = NULL;

  out:
  	mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
  	return rc;
  }
  
  /**
   * ecryptfs_find_auth_tok_for_sig
   * @auth_tok: Set to the matching auth_tok; NULL if not found
   * @crypt_stat: inode crypt_stat crypto context
   * @sig: Sig of auth_tok to find
   *
   * For now, this function simply looks at the registered auth_tok's
   * linked off the mount_crypt_stat, so all the auth_toks that can be
   * used must be registered at mount time. This function could
   * potentially try a lot harder to find auth_tok's (e.g., by calling
   * out to ecryptfsd to dynamically retrieve an auth_tok object) so
   * that static registration of auth_tok's will no longer be necessary.
   *
   * Returns zero on no error; non-zero on error
   */
  static int
  ecryptfs_find_auth_tok_for_sig(

  	struct key **auth_tok_key,

  	struct ecryptfs_auth_tok **auth_tok,
  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat,
  	char *sig)
  {

  	int rc = 0;

  	rc = ecryptfs_find_global_auth_tok_for_sig(auth_tok_key, auth_tok,
  						   mount_crypt_stat, sig);
  	if (rc == -ENOENT) {

  		/* if the flag ECRYPTFS_GLOBAL_MOUNT_AUTH_TOK_ONLY is set in the
  		 * mount_crypt_stat structure, we prevent to use auth toks that
  		 * are not inserted through the ecryptfs_add_global_auth_tok
  		 * function.
  		 */
  		if (mount_crypt_stat->flags
  				& ECRYPTFS_GLOBAL_MOUNT_AUTH_TOK_ONLY)
  			return -EINVAL;

  		rc = ecryptfs_keyring_auth_tok_for_sig(auth_tok_key, auth_tok,

  						       sig);

  	}

  	return rc;
  }
  
  /**
   * write_tag_70_packet can gobble a lot of stack space. We stuff most
   * of the function's parameters in a kmalloc'd struct to help reduce
   * eCryptfs' overall stack usage.
   */
  struct ecryptfs_write_tag_70_packet_silly_stack {
  	u8 cipher_code;
  	size_t max_packet_size;
  	size_t packet_size_len;
  	size_t block_aligned_filename_size;
  	size_t block_size;
  	size_t i;
  	size_t j;
  	size_t num_rand_bytes;
  	struct mutex *tfm_mutex;
  	char *block_aligned_filename;
  	struct ecryptfs_auth_tok *auth_tok;

  	struct scatterlist src_sg[2];
  	struct scatterlist dst_sg[2];

  	struct blkcipher_desc desc;
  	char iv[ECRYPTFS_MAX_IV_BYTES];
  	char hash[ECRYPTFS_TAG_70_DIGEST_SIZE];
  	char tmp_hash[ECRYPTFS_TAG_70_DIGEST_SIZE];
  	struct hash_desc hash_desc;
  	struct scatterlist hash_sg;
  };
  
  /**
   * write_tag_70_packet - Write encrypted filename (EFN) packet against FNEK
   * @filename: NULL-terminated filename string
   *
   * This is the simplest mechanism for achieving filename encryption in
   * eCryptfs. It encrypts the given filename with the mount-wide
   * filename encryption key (FNEK) and stores it in a packet to @dest,
   * which the callee will encode and write directly into the dentry
   * name.
   */
  int
  ecryptfs_write_tag_70_packet(char *dest, size_t *remaining_bytes,
  			     size_t *packet_size,
  			     struct ecryptfs_mount_crypt_stat *mount_crypt_stat,
  			     char *filename, size_t filename_size)
  {
  	struct ecryptfs_write_tag_70_packet_silly_stack *s;

  	struct key *auth_tok_key = NULL;

  	int rc = 0;
  
  	s = kmalloc(sizeof(*s), GFP_KERNEL);
  	if (!s) {
  		printk(KERN_ERR "%s: Out of memory whilst trying to kmalloc "

  		       "[%zd] bytes of kernel memory
  ", __func__, sizeof(*s));

  		rc = -ENOMEM;

  		goto out;
  	}
  	s->desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;
  	(*packet_size) = 0;

  	rc = ecryptfs_find_auth_tok_for_sig(
  		&auth_tok_key,
  		&s->auth_tok, mount_crypt_stat,
  		mount_crypt_stat->global_default_fnek_sig);
  	if (rc) {
  		printk(KERN_ERR "%s: Error attempting to find auth tok for "
  		       "fnek sig [%s]; rc = [%d]
  ", __func__,
  		       mount_crypt_stat->global_default_fnek_sig, rc);
  		goto out;
  	}

  	rc = ecryptfs_get_tfm_and_mutex_for_cipher_name(
  		&s->desc.tfm,
  		&s->tfm_mutex, mount_crypt_stat->global_default_fn_cipher_name);
  	if (unlikely(rc)) {
  		printk(KERN_ERR "Internal error whilst attempting to get "
  		       "tfm and mutex for cipher name [%s]; rc = [%d]
  ",
  		       mount_crypt_stat->global_default_fn_cipher_name, rc);
  		goto out;
  	}
  	mutex_lock(s->tfm_mutex);
  	s->block_size = crypto_blkcipher_blocksize(s->desc.tfm);
  	/* Plus one for the \0 separator between the random prefix
  	 * and the plaintext filename */
  	s->num_rand_bytes = (ECRYPTFS_FILENAME_MIN_RANDOM_PREPEND_BYTES + 1);
  	s->block_aligned_filename_size = (s->num_rand_bytes + filename_size);
  	if ((s->block_aligned_filename_size % s->block_size) != 0) {
  		s->num_rand_bytes += (s->block_size
  				      - (s->block_aligned_filename_size
  					 % s->block_size));
  		s->block_aligned_filename_size = (s->num_rand_bytes
  						  + filename_size);
  	}
  	/* Octet 0: Tag 70 identifier
  	 * Octets 1-N1: Tag 70 packet size (includes cipher identifier
  	 *              and block-aligned encrypted filename size)
  	 * Octets N1-N2: FNEK sig (ECRYPTFS_SIG_SIZE)
  	 * Octet N2-N3: Cipher identifier (1 octet)
  	 * Octets N3-N4: Block-aligned encrypted filename
  	 *  - Consists of a minimum number of random characters, a \0
  	 *    separator, and then the filename */
  	s->max_packet_size = (1                   /* Tag 70 identifier */
  			      + 3                 /* Max Tag 70 packet size */
  			      + ECRYPTFS_SIG_SIZE /* FNEK sig */
  			      + 1                 /* Cipher identifier */
  			      + s->block_aligned_filename_size);
  	if (dest == NULL) {
  		(*packet_size) = s->max_packet_size;
  		goto out_unlock;
  	}
  	if (s->max_packet_size > (*remaining_bytes)) {

  		printk(KERN_WARNING "%s: Require [%zd] bytes to write; only "
  		       "[%zd] available
  ", __func__, s->max_packet_size,

  		       (*remaining_bytes));
  		rc = -EINVAL;
  		goto out_unlock;
  	}
  	s->block_aligned_filename = kzalloc(s->block_aligned_filename_size,
  					    GFP_KERNEL);
  	if (!s->block_aligned_filename) {
  		printk(KERN_ERR "%s: Out of kernel memory whilst attempting to "

  		       "kzalloc [%zd] bytes
  ", __func__,

  		       s->block_aligned_filename_size);
  		rc = -ENOMEM;
  		goto out_unlock;
  	}
  	s->i = 0;
  	dest[s->i++] = ECRYPTFS_TAG_70_PACKET_TYPE;
  	rc = ecryptfs_write_packet_length(&dest[s->i],
  					  (ECRYPTFS_SIG_SIZE
  					   + 1 /* Cipher code */
  					   + s->block_aligned_filename_size),
  					  &s->packet_size_len);
  	if (rc) {
  		printk(KERN_ERR "%s: Error generating tag 70 packet "
  		       "header; cannot generate packet length; rc = [%d]
  ",
  		       __func__, rc);
  		goto out_free_unlock;
  	}
  	s->i += s->packet_size_len;
  	ecryptfs_from_hex(&dest[s->i],
  			  mount_crypt_stat->global_default_fnek_sig,
  			  ECRYPTFS_SIG_SIZE);
  	s->i += ECRYPTFS_SIG_SIZE;
  	s->cipher_code = ecryptfs_code_for_cipher_string(
  		mount_crypt_stat->global_default_fn_cipher_name,
  		mount_crypt_stat->global_default_fn_cipher_key_bytes);
  	if (s->cipher_code == 0) {
  		printk(KERN_WARNING "%s: Unable to generate code for "

  		       "cipher [%s] with key bytes [%zd]
  ", __func__,

  		       mount_crypt_stat->global_default_fn_cipher_name,
  		       mount_crypt_stat->global_default_fn_cipher_key_bytes);
  		rc = -EINVAL;
  		goto out_free_unlock;
  	}
  	dest[s->i++] = s->cipher_code;

  	/* TODO: Support other key modules than passphrase for
  	 * filename encryption */

  	if (s->auth_tok->token_type != ECRYPTFS_PASSWORD) {
  		rc = -EOPNOTSUPP;
  		printk(KERN_INFO "%s: Filename encryption only supports "
  		       "password tokens
  ", __func__);
  		goto out_free_unlock;
  	}

  	sg_init_one(
  		&s->hash_sg,
  		(u8 *)s->auth_tok->token.password.session_key_encryption_key,
  		s->auth_tok->token.password.session_key_encryption_key_bytes);
  	s->hash_desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;
  	s->hash_desc.tfm = crypto_alloc_hash(ECRYPTFS_TAG_70_DIGEST, 0,
  					     CRYPTO_ALG_ASYNC);
  	if (IS_ERR(s->hash_desc.tfm)) {
  			rc = PTR_ERR(s->hash_desc.tfm);
  			printk(KERN_ERR "%s: Error attempting to "
  			       "allocate hash crypto context; rc = [%d]
  ",
  			       __func__, rc);
  			goto out_free_unlock;
  	}
  	rc = crypto_hash_init(&s->hash_desc);
  	if (rc) {
  		printk(KERN_ERR
  		       "%s: Error initializing crypto hash; rc = [%d]
  ",
  		       __func__, rc);
  		goto out_release_free_unlock;
  	}
  	rc = crypto_hash_update(
  		&s->hash_desc, &s->hash_sg,
  		s->auth_tok->token.password.session_key_encryption_key_bytes);
  	if (rc) {
  		printk(KERN_ERR
  		       "%s: Error updating crypto hash; rc = [%d]
  ",
  		       __func__, rc);
  		goto out_release_free_unlock;
  	}
  	rc = crypto_hash_final(&s->hash_desc, s->hash);
  	if (rc) {
  		printk(KERN_ERR
  		       "%s: Error finalizing crypto hash; rc = [%d]
  ",
  		       __func__, rc);
  		goto out_release_free_unlock;
  	}
  	for (s->j = 0; s->j < (s->num_rand_bytes - 1); s->j++) {
  		s->block_aligned_filename[s->j] =
  			s->hash[(s->j % ECRYPTFS_TAG_70_DIGEST_SIZE)];
  		if ((s->j % ECRYPTFS_TAG_70_DIGEST_SIZE)
  		    == (ECRYPTFS_TAG_70_DIGEST_SIZE - 1)) {
  			sg_init_one(&s->hash_sg, (u8 *)s->hash,
  				    ECRYPTFS_TAG_70_DIGEST_SIZE);
  			rc = crypto_hash_init(&s->hash_desc);
  			if (rc) {
  				printk(KERN_ERR
  				       "%s: Error initializing crypto hash; "
  				       "rc = [%d]
  ", __func__, rc);
  				goto out_release_free_unlock;
  			}
  			rc = crypto_hash_update(&s->hash_desc, &s->hash_sg,
  						ECRYPTFS_TAG_70_DIGEST_SIZE);
  			if (rc) {
  				printk(KERN_ERR
  				       "%s: Error updating crypto hash; "
  				       "rc = [%d]
  ", __func__, rc);
  				goto out_release_free_unlock;
  			}
  			rc = crypto_hash_final(&s->hash_desc, s->tmp_hash);
  			if (rc) {
  				printk(KERN_ERR
  				       "%s: Error finalizing crypto hash; "
  				       "rc = [%d]
  ", __func__, rc);
  				goto out_release_free_unlock;
  			}
  			memcpy(s->hash, s->tmp_hash,
  			       ECRYPTFS_TAG_70_DIGEST_SIZE);
  		}
  		if (s->block_aligned_filename[s->j] == '\0')
  			s->block_aligned_filename[s->j] = ECRYPTFS_NON_NULL;
  	}
  	memcpy(&s->block_aligned_filename[s->num_rand_bytes], filename,
  	       filename_size);
  	rc = virt_to_scatterlist(s->block_aligned_filename,

  				 s->block_aligned_filename_size, s->src_sg, 2);
  	if (rc < 1) {

  		printk(KERN_ERR "%s: Internal error whilst attempting to "

  		       "convert filename memory to scatterlist; rc = [%d]. "

  		       "block_aligned_filename_size = [%zd]
  ", __func__, rc,

  		       s->block_aligned_filename_size);
  		goto out_release_free_unlock;
  	}
  	rc = virt_to_scatterlist(&dest[s->i], s->block_aligned_filename_size,

  				 s->dst_sg, 2);
  	if (rc < 1) {

  		printk(KERN_ERR "%s: Internal error whilst attempting to "
  		       "convert encrypted filename memory to scatterlist; "

  		       "rc = [%d]. block_aligned_filename_size = [%zd]
  ",
  		       __func__, rc, s->block_aligned_filename_size);

  		goto out_release_free_unlock;
  	}
  	/* The characters in the first block effectively do the job
  	 * of the IV here, so we just use 0's for the IV. Note the
  	 * constraint that ECRYPTFS_FILENAME_MIN_RANDOM_PREPEND_BYTES
  	 * >= ECRYPTFS_MAX_IV_BYTES. */
  	memset(s->iv, 0, ECRYPTFS_MAX_IV_BYTES);
  	s->desc.info = s->iv;
  	rc = crypto_blkcipher_setkey(
  		s->desc.tfm,
  		s->auth_tok->token.password.session_key_encryption_key,
  		mount_crypt_stat->global_default_fn_cipher_key_bytes);
  	if (rc < 0) {
  		printk(KERN_ERR "%s: Error setting key for crypto context; "
  		       "rc = [%d]. s->auth_tok->token.password.session_key_"
  		       "encryption_key = [0x%p]; mount_crypt_stat->"

  		       "global_default_fn_cipher_key_bytes = [%zd]
  ", __func__,

  		       rc,
  		       s->auth_tok->token.password.session_key_encryption_key,
  		       mount_crypt_stat->global_default_fn_cipher_key_bytes);
  		goto out_release_free_unlock;
  	}

  	rc = crypto_blkcipher_encrypt_iv(&s->desc, s->dst_sg, s->src_sg,

  					 s->block_aligned_filename_size);
  	if (rc) {
  		printk(KERN_ERR "%s: Error attempting to encrypt filename; "
  		       "rc = [%d]
  ", __func__, rc);
  		goto out_release_free_unlock;
  	}
  	s->i += s->block_aligned_filename_size;
  	(*packet_size) = s->i;
  	(*remaining_bytes) -= (*packet_size);
  out_release_free_unlock:
  	crypto_free_hash(s->hash_desc.tfm);
  out_free_unlock:

  	kzfree(s->block_aligned_filename);

  out_unlock:
  	mutex_unlock(s->tfm_mutex);
  out:

  	if (auth_tok_key) {
  		up_write(&(auth_tok_key->sem));

  		key_put(auth_tok_key);

  	}

  	kfree(s);
  	return rc;
  }
  
  struct ecryptfs_parse_tag_70_packet_silly_stack {
  	u8 cipher_code;
  	size_t max_packet_size;
  	size_t packet_size_len;
  	size_t parsed_tag_70_packet_size;
  	size_t block_aligned_filename_size;
  	size_t block_size;
  	size_t i;
  	struct mutex *tfm_mutex;
  	char *decrypted_filename;
  	struct ecryptfs_auth_tok *auth_tok;

  	struct scatterlist src_sg[2];
  	struct scatterlist dst_sg[2];

  	struct blkcipher_desc desc;
  	char fnek_sig_hex[ECRYPTFS_SIG_SIZE_HEX + 1];
  	char iv[ECRYPTFS_MAX_IV_BYTES];
  	char cipher_string[ECRYPTFS_MAX_CIPHER_NAME_SIZE];
  };
  
  /**
   * parse_tag_70_packet - Parse and process FNEK-encrypted passphrase packet
   * @filename: This function kmalloc's the memory for the filename

   * @filename_size: This function sets this to the amount of memory
   *                 kmalloc'd for the filename
   * @packet_size: This function sets this to the the number of octets
   *               in the packet parsed
   * @mount_crypt_stat: The mount-wide cryptographic context
   * @data: The memory location containing the start of the tag 70
   *        packet
   * @max_packet_size: The maximum legal size of the packet to be parsed
   *                   from @data
   *
   * Returns zero on success; non-zero otherwise

   */
  int
  ecryptfs_parse_tag_70_packet(char **filename, size_t *filename_size,
  			     size_t *packet_size,
  			     struct ecryptfs_mount_crypt_stat *mount_crypt_stat,
  			     char *data, size_t max_packet_size)
  {
  	struct ecryptfs_parse_tag_70_packet_silly_stack *s;

  	struct key *auth_tok_key = NULL;

  	int rc = 0;
  
  	(*packet_size) = 0;
  	(*filename_size) = 0;
  	(*filename) = NULL;
  	s = kmalloc(sizeof(*s), GFP_KERNEL);
  	if (!s) {
  		printk(KERN_ERR "%s: Out of memory whilst trying to kmalloc "

  		       "[%zd] bytes of kernel memory
  ", __func__, sizeof(*s));

  		rc = -ENOMEM;

  		goto out;
  	}
  	s->desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;
  	if (max_packet_size < (1 + 1 + ECRYPTFS_SIG_SIZE + 1 + 1)) {

  		printk(KERN_WARNING "%s: max_packet_size is [%zd]; it must be "

  		       "at least [%d]
  ", __func__, max_packet_size,
  			(1 + 1 + ECRYPTFS_SIG_SIZE + 1 + 1));
  		rc = -EINVAL;
  		goto out;
  	}
  	/* Octet 0: Tag 70 identifier
  	 * Octets 1-N1: Tag 70 packet size (includes cipher identifier
  	 *              and block-aligned encrypted filename size)
  	 * Octets N1-N2: FNEK sig (ECRYPTFS_SIG_SIZE)
  	 * Octet N2-N3: Cipher identifier (1 octet)
  	 * Octets N3-N4: Block-aligned encrypted filename
  	 *  - Consists of a minimum number of random numbers, a \0
  	 *    separator, and then the filename */
  	if (data[(*packet_size)++] != ECRYPTFS_TAG_70_PACKET_TYPE) {
  		printk(KERN_WARNING "%s: Invalid packet tag [0x%.2x]; must be "
  		       "tag [0x%.2x]
  ", __func__,
  		       data[((*packet_size) - 1)], ECRYPTFS_TAG_70_PACKET_TYPE);
  		rc = -EINVAL;
  		goto out;
  	}
  	rc = ecryptfs_parse_packet_length(&data[(*packet_size)],
  					  &s->parsed_tag_70_packet_size,
  					  &s->packet_size_len);
  	if (rc) {
  		printk(KERN_WARNING "%s: Error parsing packet length; "
  		       "rc = [%d]
  ", __func__, rc);
  		goto out;
  	}
  	s->block_aligned_filename_size = (s->parsed_tag_70_packet_size
  					  - ECRYPTFS_SIG_SIZE - 1);
  	if ((1 + s->packet_size_len + s->parsed_tag_70_packet_size)
  	    > max_packet_size) {

  		printk(KERN_WARNING "%s: max_packet_size is [%zd]; real packet "
  		       "size is [%zd]
  ", __func__, max_packet_size,

  		       (1 + s->packet_size_len + 1
  			+ s->block_aligned_filename_size));
  		rc = -EINVAL;
  		goto out;
  	}
  	(*packet_size) += s->packet_size_len;
  	ecryptfs_to_hex(s->fnek_sig_hex, &data[(*packet_size)],
  			ECRYPTFS_SIG_SIZE);
  	s->fnek_sig_hex[ECRYPTFS_SIG_SIZE_HEX] = '\0';
  	(*packet_size) += ECRYPTFS_SIG_SIZE;
  	s->cipher_code = data[(*packet_size)++];
  	rc = ecryptfs_cipher_code_to_string(s->cipher_string, s->cipher_code);
  	if (rc) {
  		printk(KERN_WARNING "%s: Cipher code [%d] is invalid
  ",
  		       __func__, s->cipher_code);
  		goto out;
  	}

  	rc = ecryptfs_find_auth_tok_for_sig(&auth_tok_key,
  					    &s->auth_tok, mount_crypt_stat,
  					    s->fnek_sig_hex);
  	if (rc) {
  		printk(KERN_ERR "%s: Error attempting to find auth tok for "
  		       "fnek sig [%s]; rc = [%d]
  ", __func__, s->fnek_sig_hex,
  		       rc);
  		goto out;
  	}

  	rc = ecryptfs_get_tfm_and_mutex_for_cipher_name(&s->desc.tfm,
  							&s->tfm_mutex,
  							s->cipher_string);
  	if (unlikely(rc)) {
  		printk(KERN_ERR "Internal error whilst attempting to get "
  		       "tfm and mutex for cipher name [%s]; rc = [%d]
  ",
  		       s->cipher_string, rc);
  		goto out;
  	}
  	mutex_lock(s->tfm_mutex);
  	rc = virt_to_scatterlist(&data[(*packet_size)],

  				 s->block_aligned_filename_size, s->src_sg, 2);
  	if (rc < 1) {

  		printk(KERN_ERR "%s: Internal error whilst attempting to "
  		       "convert encrypted filename memory to scatterlist; "

  		       "rc = [%d]. block_aligned_filename_size = [%zd]
  ",
  		       __func__, rc, s->block_aligned_filename_size);

  		goto out_unlock;
  	}
  	(*packet_size) += s->block_aligned_filename_size;
  	s->decrypted_filename = kmalloc(s->block_aligned_filename_size,
  					GFP_KERNEL);
  	if (!s->decrypted_filename) {
  		printk(KERN_ERR "%s: Out of memory whilst attempting to "

  		       "kmalloc [%zd] bytes
  ", __func__,

  		       s->block_aligned_filename_size);
  		rc = -ENOMEM;
  		goto out_unlock;
  	}
  	rc = virt_to_scatterlist(s->decrypted_filename,

  				 s->block_aligned_filename_size, s->dst_sg, 2);
  	if (rc < 1) {

  		printk(KERN_ERR "%s: Internal error whilst attempting to "
  		       "convert decrypted filename memory to scatterlist; "

  		       "rc = [%d]. block_aligned_filename_size = [%zd]
  ",
  		       __func__, rc, s->block_aligned_filename_size);

  		goto out_free_unlock;
  	}
  	/* The characters in the first block effectively do the job of
  	 * the IV here, so we just use 0's for the IV. Note the
  	 * constraint that ECRYPTFS_FILENAME_MIN_RANDOM_PREPEND_BYTES
  	 * >= ECRYPTFS_MAX_IV_BYTES. */
  	memset(s->iv, 0, ECRYPTFS_MAX_IV_BYTES);
  	s->desc.info = s->iv;

  	/* TODO: Support other key modules than passphrase for
  	 * filename encryption */

  	if (s->auth_tok->token_type != ECRYPTFS_PASSWORD) {
  		rc = -EOPNOTSUPP;
  		printk(KERN_INFO "%s: Filename encryption only supports "
  		       "password tokens
  ", __func__);
  		goto out_free_unlock;
  	}

  	rc = crypto_blkcipher_setkey(
  		s->desc.tfm,
  		s->auth_tok->token.password.session_key_encryption_key,
  		mount_crypt_stat->global_default_fn_cipher_key_bytes);
  	if (rc < 0) {
  		printk(KERN_ERR "%s: Error setting key for crypto context; "
  		       "rc = [%d]. s->auth_tok->token.password.session_key_"
  		       "encryption_key = [0x%p]; mount_crypt_stat->"

  		       "global_default_fn_cipher_key_bytes = [%zd]
  ", __func__,

  		       rc,
  		       s->auth_tok->token.password.session_key_encryption_key,
  		       mount_crypt_stat->global_default_fn_cipher_key_bytes);
  		goto out_free_unlock;
  	}

  	rc = crypto_blkcipher_decrypt_iv(&s->desc, s->dst_sg, s->src_sg,

  					 s->block_aligned_filename_size);
  	if (rc) {
  		printk(KERN_ERR "%s: Error attempting to decrypt filename; "
  		       "rc = [%d]
  ", __func__, rc);
  		goto out_free_unlock;
  	}
  	s->i = 0;
  	while (s->decrypted_filename[s->i] != '\0'
  	       && s->i < s->block_aligned_filename_size)
  		s->i++;
  	if (s->i == s->block_aligned_filename_size) {
  		printk(KERN_WARNING "%s: Invalid tag 70 packet; could not "
  		       "find valid separator between random characters and "
  		       "the filename
  ", __func__);
  		rc = -EINVAL;
  		goto out_free_unlock;
  	}
  	s->i++;
  	(*filename_size) = (s->block_aligned_filename_size - s->i);
  	if (!((*filename_size) > 0 && (*filename_size < PATH_MAX))) {

  		printk(KERN_WARNING "%s: Filename size is [%zd], which is "

  		       "invalid
  ", __func__, (*filename_size));
  		rc = -EINVAL;
  		goto out_free_unlock;
  	}
  	(*filename) = kmalloc(((*filename_size) + 1), GFP_KERNEL);
  	if (!(*filename)) {
  		printk(KERN_ERR "%s: Out of memory whilst attempting to "

  		       "kmalloc [%zd] bytes
  ", __func__,

  		       ((*filename_size) + 1));
  		rc = -ENOMEM;
  		goto out_free_unlock;
  	}
  	memcpy((*filename), &s->decrypted_filename[s->i], (*filename_size));
  	(*filename)[(*filename_size)] = '\0';
  out_free_unlock:
  	kfree(s->decrypted_filename);
  out_unlock:
  	mutex_unlock(s->tfm_mutex);
  out:
  	if (rc) {
  		(*packet_size) = 0;
  		(*filename_size) = 0;
  		(*filename) = NULL;
  	}

  	if (auth_tok_key) {
  		up_write(&(auth_tok_key->sem));

  		key_put(auth_tok_key);

  	}

  	kfree(s);
  	return rc;
  }
  
  static int

  ecryptfs_get_auth_tok_sig(char **sig, struct ecryptfs_auth_tok *auth_tok)
  {
  	int rc = 0;
  
  	(*sig) = NULL;
  	switch (auth_tok->token_type) {
  	case ECRYPTFS_PASSWORD:
  		(*sig) = auth_tok->token.password.signature;
  		break;
  	case ECRYPTFS_PRIVATE_KEY:
  		(*sig) = auth_tok->token.private_key.signature;
  		break;
  	default:
  		printk(KERN_ERR "Cannot get sig for auth_tok of type [%d]
  ",
  		       auth_tok->token_type);
  		rc = -EINVAL;
  	}
  	return rc;
  }

  /**

   * decrypt_pki_encrypted_session_key - Decrypt the session key with the given auth_tok.
   * @auth_tok: The key authentication token used to decrypt the session key
   * @crypt_stat: The cryptographic context

   *

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

   */

  static int
  decrypt_pki_encrypted_session_key(struct ecryptfs_auth_tok *auth_tok,
  				  struct ecryptfs_crypt_stat *crypt_stat)

  {

  	u8 cipher_code = 0;

  	struct ecryptfs_msg_ctx *msg_ctx;
  	struct ecryptfs_message *msg = NULL;

  	char *auth_tok_sig;

  	char *payload;
  	size_t payload_len;

  	int rc;

  	rc = ecryptfs_get_auth_tok_sig(&auth_tok_sig, auth_tok);
  	if (rc) {

  		printk(KERN_ERR "Unrecognized auth tok type: [%d]
  ",
  		       auth_tok->token_type);
  		goto out;
  	}
  	rc = write_tag_64_packet(auth_tok_sig, &(auth_tok->session_key),

  				 &payload, &payload_len);

  	if (rc) {

  		ecryptfs_printk(KERN_ERR, "Failed to write tag 64 packet
  ");

  		goto out;
  	}

  	rc = ecryptfs_send_message(payload, payload_len, &msg_ctx);

  	if (rc) {

  		ecryptfs_printk(KERN_ERR, "Error sending message to "
  				"ecryptfsd
  ");

  		goto out;
  	}
  	rc = ecryptfs_wait_for_response(msg_ctx, &msg);
  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Failed to receive tag 65 packet "
  				"from the user space daemon
  ");
  		rc = -EIO;
  		goto out;
  	}
  	rc = parse_tag_65_packet(&(auth_tok->session_key),
  				 &cipher_code, msg);
  	if (rc) {
  		printk(KERN_ERR "Failed to parse tag 65 packet; rc = [%d]
  ",
  		       rc);
  		goto out;
  	}
  	auth_tok->session_key.flags |= ECRYPTFS_CONTAINS_DECRYPTED_KEY;
  	memcpy(crypt_stat->key, auth_tok->session_key.decrypted_key,
  	       auth_tok->session_key.decrypted_key_size);
  	crypt_stat->key_size = auth_tok->session_key.decrypted_key_size;
  	rc = ecryptfs_cipher_code_to_string(crypt_stat->cipher, cipher_code);
  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Cipher code [%d] is invalid
  ",
  				cipher_code)
  		goto out;
  	}
  	crypt_stat->flags |= ECRYPTFS_KEY_VALID;
  	if (ecryptfs_verbosity > 0) {
  		ecryptfs_printk(KERN_DEBUG, "Decrypted session key:
  ");
  		ecryptfs_dump_hex(crypt_stat->key,
  				  crypt_stat->key_size);
  	}
  out:
  	if (msg)
  		kfree(msg);
  	return rc;
  }
  
  static void wipe_auth_tok_list(struct list_head *auth_tok_list_head)
  {

  	struct ecryptfs_auth_tok_list_item *auth_tok_list_item;

  	struct ecryptfs_auth_tok_list_item *auth_tok_list_item_tmp;

  	list_for_each_entry_safe(auth_tok_list_item, auth_tok_list_item_tmp,
  				 auth_tok_list_head, list) {
  		list_del(&auth_tok_list_item->list);

  		kmem_cache_free(ecryptfs_auth_tok_list_item_cache,
  				auth_tok_list_item);
  	}

  }
  
  struct kmem_cache *ecryptfs_auth_tok_list_item_cache;

  /**
   * parse_tag_1_packet

   * @crypt_stat: The cryptographic context to modify based on packet contents

   * @data: The raw bytes of the packet.
   * @auth_tok_list: eCryptfs parses packets into authentication tokens;

   *                 a new authentication token will be placed at the
   *                 end of this list for this packet.

   * @new_auth_tok: Pointer to a pointer to memory that this function
   *                allocates; sets the memory address of the pointer to
   *                NULL on error. This object is added to the
   *                auth_tok_list.
   * @packet_size: This function writes the size of the parsed packet
   *               into this memory location; zero on error.

   * @max_packet_size: The maximum allowable packet size

   *
   * Returns zero on success; non-zero on error.
   */
  static int
  parse_tag_1_packet(struct ecryptfs_crypt_stat *crypt_stat,
  		   unsigned char *data, struct list_head *auth_tok_list,
  		   struct ecryptfs_auth_tok **new_auth_tok,
  		   size_t *packet_size, size_t max_packet_size)
  {
  	size_t body_size;
  	struct ecryptfs_auth_tok_list_item *auth_tok_list_item;
  	size_t length_size;
  	int rc = 0;
  
  	(*packet_size) = 0;
  	(*new_auth_tok) = NULL;

  	/**
  	 * This format is inspired by OpenPGP; see RFC 2440
  	 * packet tag 1
  	 *
  	 * Tag 1 identifier (1 byte)
  	 * Max Tag 1 packet size (max 3 bytes)
  	 * Version (1 byte)
  	 * Key identifier (8 bytes; ECRYPTFS_SIG_SIZE)
  	 * Cipher identifier (1 byte)
  	 * Encrypted key size (arbitrary)
  	 *
  	 * 12 bytes minimum packet size

  	 */

  	if (unlikely(max_packet_size < 12)) {
  		printk(KERN_ERR "Invalid max packet size; must be >=12
  ");

  		rc = -EINVAL;
  		goto out;
  	}

  	if (data[(*packet_size)++] != ECRYPTFS_TAG_1_PACKET_TYPE) {

  		printk(KERN_ERR "Enter w/ first byte != 0x%.2x
  ",
  		       ECRYPTFS_TAG_1_PACKET_TYPE);

  		rc = -EINVAL;
  		goto out;
  	}
  	/* Released: wipe_auth_tok_list called in ecryptfs_parse_packet_set or
  	 * at end of function upon failure */
  	auth_tok_list_item =

  		kmem_cache_zalloc(ecryptfs_auth_tok_list_item_cache,
  				  GFP_KERNEL);

  	if (!auth_tok_list_item) {

  		printk(KERN_ERR "Unable to allocate memory
  ");

  		rc = -ENOMEM;
  		goto out;
  	}

  	(*new_auth_tok) = &auth_tok_list_item->auth_tok;

  	rc = ecryptfs_parse_packet_length(&data[(*packet_size)], &body_size,
  					  &length_size);

  	if (rc) {

  		printk(KERN_WARNING "Error parsing packet length; "
  		       "rc = [%d]
  ", rc);

  		goto out_free;
  	}

  	if (unlikely(body_size < (ECRYPTFS_SIG_SIZE + 2))) {

  		printk(KERN_WARNING "Invalid body size ([%td])
  ", body_size);

  		rc = -EINVAL;
  		goto out_free;
  	}
  	(*packet_size) += length_size;
  	if (unlikely((*packet_size) + body_size > max_packet_size)) {

  		printk(KERN_WARNING "Packet size exceeds max
  ");

  		rc = -EINVAL;
  		goto out_free;
  	}

  	if (unlikely(data[(*packet_size)++] != 0x03)) {

  		printk(KERN_WARNING "Unknown version number [%d]
  ",
  		       data[(*packet_size) - 1]);

  		rc = -EINVAL;
  		goto out_free;
  	}

  	ecryptfs_to_hex((*new_auth_tok)->token.private_key.signature,
  			&data[(*packet_size)], ECRYPTFS_SIG_SIZE);
  	*packet_size += ECRYPTFS_SIG_SIZE;
  	/* This byte is skipped because the kernel does not need to
  	 * know which public key encryption algorithm was used */
  	(*packet_size)++;
  	(*new_auth_tok)->session_key.encrypted_key_size =

  		body_size - (ECRYPTFS_SIG_SIZE + 2);

  	if ((*new_auth_tok)->session_key.encrypted_key_size
  	    > ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES) {

  		printk(KERN_WARNING "Tag 1 packet contains key larger "
  		       "than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES");

  		rc = -EINVAL;
  		goto out;
  	}

  	memcpy((*new_auth_tok)->session_key.encrypted_key,

  	       &data[(*packet_size)], (body_size - (ECRYPTFS_SIG_SIZE + 2)));

  	(*packet_size) += (*new_auth_tok)->session_key.encrypted_key_size;
  	(*new_auth_tok)->session_key.flags &=
  		~ECRYPTFS_CONTAINS_DECRYPTED_KEY;
  	(*new_auth_tok)->session_key.flags |=
  		ECRYPTFS_CONTAINS_ENCRYPTED_KEY;
  	(*new_auth_tok)->token_type = ECRYPTFS_PRIVATE_KEY;

  	(*new_auth_tok)->flags = 0;

  	(*new_auth_tok)->session_key.flags &=
  		~(ECRYPTFS_USERSPACE_SHOULD_TRY_TO_DECRYPT);
  	(*new_auth_tok)->session_key.flags &=
  		~(ECRYPTFS_USERSPACE_SHOULD_TRY_TO_ENCRYPT);

  	list_add(&auth_tok_list_item->list, auth_tok_list);
  	goto out;
  out_free:
  	(*new_auth_tok) = NULL;
  	memset(auth_tok_list_item, 0,
  	       sizeof(struct ecryptfs_auth_tok_list_item));
  	kmem_cache_free(ecryptfs_auth_tok_list_item_cache,
  			auth_tok_list_item);
  out:
  	if (rc)
  		(*packet_size) = 0;
  	return rc;
  }

  /**
   * parse_tag_3_packet
   * @crypt_stat: The cryptographic context to modify based on packet
   *              contents.
   * @data: The raw bytes of the packet.
   * @auth_tok_list: eCryptfs parses packets into authentication tokens;
   *                 a new authentication token will be placed at the end
   *                 of this list for this packet.
   * @new_auth_tok: Pointer to a pointer to memory that this function
   *                allocates; sets the memory address of the pointer to
   *                NULL on error. This object is added to the
   *                auth_tok_list.
   * @packet_size: This function writes the size of the parsed packet
   *               into this memory location; zero on error.
   * @max_packet_size: maximum number of bytes to parse
   *
   * Returns zero on success; non-zero on error.
   */
  static int
  parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat,
  		   unsigned char *data, struct list_head *auth_tok_list,
  		   struct ecryptfs_auth_tok **new_auth_tok,
  		   size_t *packet_size, size_t max_packet_size)
  {

  	size_t body_size;
  	struct ecryptfs_auth_tok_list_item *auth_tok_list_item;
  	size_t length_size;

  	int rc = 0;

  
  	(*packet_size) = 0;
  	(*new_auth_tok) = NULL;

  	/**
  	 *This format is inspired by OpenPGP; see RFC 2440
  	 * packet tag 3
  	 *
  	 * Tag 3 identifier (1 byte)
  	 * Max Tag 3 packet size (max 3 bytes)
  	 * Version (1 byte)
  	 * Cipher code (1 byte)
  	 * S2K specifier (1 byte)
  	 * Hash identifier (1 byte)
  	 * Salt (ECRYPTFS_SALT_SIZE)
  	 * Hash iterations (1 byte)
  	 * Encrypted key (arbitrary)
  	 *
  	 * (ECRYPTFS_SALT_SIZE + 7) minimum packet size

  	 */

  	if (max_packet_size < (ECRYPTFS_SALT_SIZE + 7)) {
  		printk(KERN_ERR "Max packet size too large
  ");

  		rc = -EINVAL;
  		goto out;
  	}

  	if (data[(*packet_size)++] != ECRYPTFS_TAG_3_PACKET_TYPE) {

  		printk(KERN_ERR "First byte != 0x%.2x; invalid packet
  ",
  		       ECRYPTFS_TAG_3_PACKET_TYPE);

  		rc = -EINVAL;
  		goto out;
  	}
  	/* Released: wipe_auth_tok_list called in ecryptfs_parse_packet_set or
  	 * at end of function upon failure */
  	auth_tok_list_item =

  	    kmem_cache_zalloc(ecryptfs_auth_tok_list_item_cache, GFP_KERNEL);

  	if (!auth_tok_list_item) {

  		printk(KERN_ERR "Unable to allocate memory
  ");

  		rc = -ENOMEM;
  		goto out;
  	}

  	(*new_auth_tok) = &auth_tok_list_item->auth_tok;

  	rc = ecryptfs_parse_packet_length(&data[(*packet_size)], &body_size,
  					  &length_size);

  	if (rc) {

  		printk(KERN_WARNING "Error parsing packet length; rc = [%d]
  ",
  		       rc);

  		goto out_free;
  	}

  	if (unlikely(body_size < (ECRYPTFS_SALT_SIZE + 5))) {

  		printk(KERN_WARNING "Invalid body size ([%td])
  ", body_size);

  		rc = -EINVAL;
  		goto out_free;
  	}
  	(*packet_size) += length_size;

  	if (unlikely((*packet_size) + body_size > max_packet_size)) {

  		printk(KERN_ERR "Packet size exceeds max
  ");

  		rc = -EINVAL;
  		goto out_free;
  	}

  	(*new_auth_tok)->session_key.encrypted_key_size =

  		(body_size - (ECRYPTFS_SALT_SIZE + 5));

  	if ((*new_auth_tok)->session_key.encrypted_key_size
  	    > ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES) {
  		printk(KERN_WARNING "Tag 3 packet contains key larger "
  		       "than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES
  ");
  		rc = -EINVAL;
  		goto out_free;
  	}

  	if (unlikely(data[(*packet_size)++] != 0x04)) {

  		printk(KERN_WARNING "Unknown version number [%d]
  ",
  		       data[(*packet_size) - 1]);

  		rc = -EINVAL;
  		goto out_free;
  	}

  	rc = ecryptfs_cipher_code_to_string(crypt_stat->cipher,
  					    (u16)data[(*packet_size)]);
  	if (rc)
  		goto out_free;

  	/* A little extra work to differentiate among the AES key
  	 * sizes; see RFC2440 */
  	switch(data[(*packet_size)++]) {
  	case RFC2440_CIPHER_AES_192:
  		crypt_stat->key_size = 24;
  		break;
  	default:
  		crypt_stat->key_size =
  			(*new_auth_tok)->session_key.encrypted_key_size;
  	}

  	rc = ecryptfs_init_crypt_ctx(crypt_stat);
  	if (rc)
  		goto out_free;

  	if (unlikely(data[(*packet_size)++] != 0x03)) {

  		printk(KERN_WARNING "Only S2K ID 3 is currently supported
  ");

  		rc = -ENOSYS;
  		goto out_free;
  	}

  	/* TODO: finish the hash mapping */

  	switch (data[(*packet_size)++]) {
  	case 0x01: /* See RFC2440 for these numbers and their mappings */
  		/* Choose MD5 */

  		memcpy((*new_auth_tok)->token.password.salt,
  		       &data[(*packet_size)], ECRYPTFS_SALT_SIZE);
  		(*packet_size) += ECRYPTFS_SALT_SIZE;

  		/* This conversion was taken straight from RFC2440 */

  		(*new_auth_tok)->token.password.hash_iterations =
  			((u32) 16 + (data[(*packet_size)] & 15))
  				<< ((data[(*packet_size)] >> 4) + 6);
  		(*packet_size)++;

  		/* Friendly reminder:
  		 * (*new_auth_tok)->session_key.encrypted_key_size =
  		 *         (body_size - (ECRYPTFS_SALT_SIZE + 5)); */

  		memcpy((*new_auth_tok)->session_key.encrypted_key,
  		       &data[(*packet_size)],
  		       (*new_auth_tok)->session_key.encrypted_key_size);
  		(*packet_size) +=
  			(*new_auth_tok)->session_key.encrypted_key_size;
  		(*new_auth_tok)->session_key.flags &=
  			~ECRYPTFS_CONTAINS_DECRYPTED_KEY;
  		(*new_auth_tok)->session_key.flags |=
  			ECRYPTFS_CONTAINS_ENCRYPTED_KEY;

  		(*new_auth_tok)->token.password.hash_algo = 0x01; /* MD5 */

  		break;
  	default:
  		ecryptfs_printk(KERN_ERR, "Unsupported hash algorithm: "
  				"[%d]
  ", data[(*packet_size) - 1]);
  		rc = -ENOSYS;
  		goto out_free;
  	}
  	(*new_auth_tok)->token_type = ECRYPTFS_PASSWORD;
  	/* TODO: Parametarize; we might actually want userspace to
  	 * decrypt the session key. */

  	(*new_auth_tok)->session_key.flags &=
  			    ~(ECRYPTFS_USERSPACE_SHOULD_TRY_TO_DECRYPT);
  	(*new_auth_tok)->session_key.flags &=
  			    ~(ECRYPTFS_USERSPACE_SHOULD_TRY_TO_ENCRYPT);

  	list_add(&auth_tok_list_item->list, auth_tok_list);
  	goto out;
  out_free:
  	(*new_auth_tok) = NULL;
  	memset(auth_tok_list_item, 0,
  	       sizeof(struct ecryptfs_auth_tok_list_item));
  	kmem_cache_free(ecryptfs_auth_tok_list_item_cache,
  			auth_tok_list_item);
  out:
  	if (rc)
  		(*packet_size) = 0;
  	return rc;
  }
  
  /**
   * parse_tag_11_packet
   * @data: The raw bytes of the packet
   * @contents: This function writes the data contents of the literal
   *            packet into this memory location
   * @max_contents_bytes: The maximum number of bytes that this function
   *                      is allowed to write into contents
   * @tag_11_contents_size: This function writes the size of the parsed
   *                        contents into this memory location; zero on
   *                        error
   * @packet_size: This function writes the size of the parsed packet
   *               into this memory location; zero on error
   * @max_packet_size: maximum number of bytes to parse
   *
   * Returns zero on success; non-zero on error.
   */
  static int
  parse_tag_11_packet(unsigned char *data, unsigned char *contents,
  		    size_t max_contents_bytes, size_t *tag_11_contents_size,
  		    size_t *packet_size, size_t max_packet_size)
  {

  	size_t body_size;
  	size_t length_size;

  	int rc = 0;

  
  	(*packet_size) = 0;
  	(*tag_11_contents_size) = 0;

  	/* This format is inspired by OpenPGP; see RFC 2440
  	 * packet tag 11
  	 *
  	 * Tag 11 identifier (1 byte)
  	 * Max Tag 11 packet size (max 3 bytes)
  	 * Binary format specifier (1 byte)
  	 * Filename length (1 byte)
  	 * Filename ("_CONSOLE") (8 bytes)
  	 * Modification date (4 bytes)
  	 * Literal data (arbitrary)
  	 *
  	 * We need at least 16 bytes of data for the packet to even be
  	 * valid.

  	 */

  	if (max_packet_size < 16) {
  		printk(KERN_ERR "Maximum packet size too small
  ");

  		rc = -EINVAL;
  		goto out;
  	}

  	if (data[(*packet_size)++] != ECRYPTFS_TAG_11_PACKET_TYPE) {

  		printk(KERN_WARNING "Invalid tag 11 packet format
  ");

  		rc = -EINVAL;
  		goto out;
  	}

  	rc = ecryptfs_parse_packet_length(&data[(*packet_size)], &body_size,
  					  &length_size);

  	if (rc) {

  		printk(KERN_WARNING "Invalid tag 11 packet format
  ");

  		goto out;
  	}

  	if (body_size < 14) {

  		printk(KERN_WARNING "Invalid body size ([%td])
  ", body_size);

  		rc = -EINVAL;
  		goto out;
  	}

  	(*packet_size) += length_size;
  	(*tag_11_contents_size) = (body_size - 14);

  	if (unlikely((*packet_size) + body_size + 1 > max_packet_size)) {

  		printk(KERN_ERR "Packet size exceeds max
  ");

  		rc = -EINVAL;
  		goto out;
  	}

  	if (unlikely((*tag_11_contents_size) > max_contents_bytes)) {
  		printk(KERN_ERR "Literal data section in tag 11 packet exceeds "
  		       "expected size
  ");
  		rc = -EINVAL;
  		goto out;
  	}

  	if (data[(*packet_size)++] != 0x62) {

  		printk(KERN_WARNING "Unrecognizable packet
  ");

  		rc = -EINVAL;
  		goto out;
  	}

  	if (data[(*packet_size)++] != 0x08) {

  		printk(KERN_WARNING "Unrecognizable packet
  ");

  		rc = -EINVAL;
  		goto out;
  	}

  	(*packet_size) += 12; /* Ignore filename and modification date */

  	memcpy(contents, &data[(*packet_size)], (*tag_11_contents_size));
  	(*packet_size) += (*tag_11_contents_size);

  out:
  	if (rc) {
  		(*packet_size) = 0;
  		(*tag_11_contents_size) = 0;
  	}
  	return rc;
  }

  int ecryptfs_keyring_auth_tok_for_sig(struct key **auth_tok_key,
  				      struct ecryptfs_auth_tok **auth_tok,
  				      char *sig)
  {
  	int rc = 0;
  
  	(*auth_tok_key) = request_key(&key_type_user, sig, NULL);
  	if (!(*auth_tok_key) || IS_ERR(*auth_tok_key)) {

  		(*auth_tok_key) = ecryptfs_get_encrypted_key(sig);
  		if (!(*auth_tok_key) || IS_ERR(*auth_tok_key)) {
  			printk(KERN_ERR "Could not find key with description: [%s]
  ",
  			      sig);
  			rc = process_request_key_err(PTR_ERR(*auth_tok_key));
  			(*auth_tok_key) = NULL;
  			goto out;
  		}

  	}

  	down_write(&(*auth_tok_key)->sem);

  	rc = ecryptfs_verify_auth_tok_from_key(*auth_tok_key, auth_tok);

  	if (rc) {

  		up_write(&(*auth_tok_key)->sem);

  		key_put(*auth_tok_key);
  		(*auth_tok_key) = NULL;

  		goto out;

  	}
  out:
  	return rc;
  }
  
  /**

   * decrypt_passphrase_encrypted_session_key - Decrypt the session key with the given auth_tok.
   * @auth_tok: The passphrase authentication token to use to encrypt the FEK
   * @crypt_stat: The cryptographic context

   *

   * Returns zero on success; non-zero error otherwise

   */

  static int
  decrypt_passphrase_encrypted_session_key(struct ecryptfs_auth_tok *auth_tok,
  					 struct ecryptfs_crypt_stat *crypt_stat)

  {

  	struct scatterlist dst_sg[2];
  	struct scatterlist src_sg[2];

  	struct mutex *tfm_mutex;

  	struct blkcipher_desc desc = {
  		.flags = CRYPTO_TFM_REQ_MAY_SLEEP
  	};
  	int rc = 0;

  	if (unlikely(ecryptfs_verbosity > 0)) {
  		ecryptfs_printk(
  			KERN_DEBUG, "Session key encryption key (size [%d]):
  ",
  			auth_tok->token.password.session_key_encryption_key_bytes);
  		ecryptfs_dump_hex(
  			auth_tok->token.password.session_key_encryption_key,
  			auth_tok->token.password.session_key_encryption_key_bytes);
  	}
  	rc = ecryptfs_get_tfm_and_mutex_for_cipher_name(&desc.tfm, &tfm_mutex,
  							crypt_stat->cipher);
  	if (unlikely(rc)) {
  		printk(KERN_ERR "Internal error whilst attempting to get "
  		       "tfm and mutex for cipher name [%s]; rc = [%d]
  ",
  		       crypt_stat->cipher, rc);
  		goto out;

  	}

  	rc = virt_to_scatterlist(auth_tok->session_key.encrypted_key,
  				 auth_tok->session_key.encrypted_key_size,

  				 src_sg, 2);
  	if (rc < 1 || rc > 2) {

  		printk(KERN_ERR "Internal error whilst attempting to convert "
  			"auth_tok->session_key.encrypted_key to scatterlist; "
  			"expected rc = 1; got rc = [%d]. "
  		       "auth_tok->session_key.encrypted_key_size = [%d]
  ", rc,
  			auth_tok->session_key.encrypted_key_size);
  		goto out;
  	}
  	auth_tok->session_key.decrypted_key_size =
  		auth_tok->session_key.encrypted_key_size;

  	rc = virt_to_scatterlist(auth_tok->session_key.decrypted_key,
  				 auth_tok->session_key.decrypted_key_size,

  				 dst_sg, 2);
  	if (rc < 1 || rc > 2) {

  		printk(KERN_ERR "Internal error whilst attempting to convert "
  			"auth_tok->session_key.decrypted_key to scatterlist; "
  			"expected rc = 1; got rc = [%d]
  ", rc);
  		goto out;
  	}
  	mutex_lock(tfm_mutex);
  	rc = crypto_blkcipher_setkey(
  		desc.tfm, auth_tok->token.password.session_key_encryption_key,
  		crypt_stat->key_size);
  	if (unlikely(rc < 0)) {
  		mutex_unlock(tfm_mutex);

  		printk(KERN_ERR "Error setting key for crypto context
  ");
  		rc = -EINVAL;

  		goto out;

  	}

  	rc = crypto_blkcipher_decrypt(&desc, dst_sg, src_sg,

  				      auth_tok->session_key.encrypted_key_size);

  	mutex_unlock(tfm_mutex);
  	if (unlikely(rc)) {

  		printk(KERN_ERR "Error decrypting; rc = [%d]
  ", rc);

  		goto out;

  	}

  	auth_tok->session_key.flags |= ECRYPTFS_CONTAINS_DECRYPTED_KEY;
  	memcpy(crypt_stat->key, auth_tok->session_key.decrypted_key,
  	       auth_tok->session_key.decrypted_key_size);

  	crypt_stat->flags |= ECRYPTFS_KEY_VALID;

  	if (unlikely(ecryptfs_verbosity > 0)) {

  		ecryptfs_printk(KERN_DEBUG, "FEK of size [%zd]:
  ",

  				crypt_stat->key_size);

  		ecryptfs_dump_hex(crypt_stat->key,
  				  crypt_stat->key_size);

  	}

  out:
  	return rc;
  }
  
  /**
   * ecryptfs_parse_packet_set

   * @crypt_stat: The cryptographic context
   * @src: Virtual address of region of memory containing the packets
   * @ecryptfs_dentry: The eCryptfs dentry associated with the packet set

   *
   * Get crypt_stat to have the file's session key if the requisite key
   * is available to decrypt the session key.
   *
   * Returns Zero if a valid authentication token was retrieved and
   * processed; negative value for file not encrypted or for error
   * conditions.
   */
  int ecryptfs_parse_packet_set(struct ecryptfs_crypt_stat *crypt_stat,
  			      unsigned char *src,
  			      struct dentry *ecryptfs_dentry)
  {
  	size_t i = 0;

  	size_t found_auth_tok;

  	size_t next_packet_is_auth_tok_packet;

  	struct list_head auth_tok_list;

  	struct ecryptfs_auth_tok *matching_auth_tok;
  	struct ecryptfs_auth_tok *candidate_auth_tok;

  	char *candidate_auth_tok_sig;

  	size_t packet_size;
  	struct ecryptfs_auth_tok *new_auth_tok;
  	unsigned char sig_tmp_space[ECRYPTFS_SIG_SIZE];

  	struct ecryptfs_auth_tok_list_item *auth_tok_list_item;

  	size_t tag_11_contents_size;
  	size_t tag_11_packet_size;

  	struct key *auth_tok_key = NULL;

  	int rc = 0;

  
  	INIT_LIST_HEAD(&auth_tok_list);

  	/* Parse the header to find as many packets as we can; these will be

  	 * added the our &auth_tok_list */
  	next_packet_is_auth_tok_packet = 1;
  	while (next_packet_is_auth_tok_packet) {
  		size_t max_packet_size = ((PAGE_CACHE_SIZE - 8) - i);
  
  		switch (src[i]) {
  		case ECRYPTFS_TAG_3_PACKET_TYPE:
  			rc = parse_tag_3_packet(crypt_stat,
  						(unsigned char *)&src[i],
  						&auth_tok_list, &new_auth_tok,
  						&packet_size, max_packet_size);
  			if (rc) {
  				ecryptfs_printk(KERN_ERR, "Error parsing "
  						"tag 3 packet
  ");
  				rc = -EIO;
  				goto out_wipe_list;
  			}
  			i += packet_size;
  			rc = parse_tag_11_packet((unsigned char *)&src[i],
  						 sig_tmp_space,
  						 ECRYPTFS_SIG_SIZE,
  						 &tag_11_contents_size,
  						 &tag_11_packet_size,
  						 max_packet_size);
  			if (rc) {
  				ecryptfs_printk(KERN_ERR, "No valid "
  						"(ecryptfs-specific) literal "
  						"packet containing "
  						"authentication token "
  						"signature found after "
  						"tag 3 packet
  ");
  				rc = -EIO;
  				goto out_wipe_list;
  			}
  			i += tag_11_packet_size;
  			if (ECRYPTFS_SIG_SIZE != tag_11_contents_size) {
  				ecryptfs_printk(KERN_ERR, "Expected "
  						"signature of size [%d]; "

  						"read size [%zd]
  ",

  						ECRYPTFS_SIG_SIZE,
  						tag_11_contents_size);
  				rc = -EIO;
  				goto out_wipe_list;
  			}
  			ecryptfs_to_hex(new_auth_tok->token.password.signature,
  					sig_tmp_space, tag_11_contents_size);
  			new_auth_tok->token.password.signature[
  				ECRYPTFS_PASSWORD_SIG_SIZE] = '\0';

  			crypt_stat->flags |= ECRYPTFS_ENCRYPTED;

  			break;

  		case ECRYPTFS_TAG_1_PACKET_TYPE:
  			rc = parse_tag_1_packet(crypt_stat,
  						(unsigned char *)&src[i],
  						&auth_tok_list, &new_auth_tok,
  						&packet_size, max_packet_size);
  			if (rc) {
  				ecryptfs_printk(KERN_ERR, "Error parsing "
  						"tag 1 packet
  ");
  				rc = -EIO;
  				goto out_wipe_list;
  			}
  			i += packet_size;

  			crypt_stat->flags |= ECRYPTFS_ENCRYPTED;

  			break;

  		case ECRYPTFS_TAG_11_PACKET_TYPE:
  			ecryptfs_printk(KERN_WARNING, "Invalid packet set "
  					"(Tag 11 not allowed by itself)
  ");
  			rc = -EIO;
  			goto out_wipe_list;
  			break;
  		default:

  			ecryptfs_printk(KERN_DEBUG, "No packet at offset [%zd] "
  					"of the file header; hex value of "

  					"character is [0x%.2x]
  ", i, src[i]);
  			next_packet_is_auth_tok_packet = 0;
  		}
  	}
  	if (list_empty(&auth_tok_list)) {

  		printk(KERN_ERR "The lower file appears to be a non-encrypted "
  		       "eCryptfs file; this is not supported in this version "
  		       "of the eCryptfs kernel module
  ");
  		rc = -EINVAL;

  		goto out;
  	}

  	/* auth_tok_list contains the set of authentication tokens
  	 * parsed from the metadata. We need to find a matching
  	 * authentication token that has the secret component(s)
  	 * necessary to decrypt the EFEK in the auth_tok parsed from
  	 * the metadata. There may be several potential matches, but
  	 * just one will be sufficient to decrypt to get the FEK. */
  find_next_matching_auth_tok:
  	found_auth_tok = 0;
  	list_for_each_entry(auth_tok_list_item, &auth_tok_list, list) {

  		candidate_auth_tok = &auth_tok_list_item->auth_tok;
  		if (unlikely(ecryptfs_verbosity > 0)) {
  			ecryptfs_printk(KERN_DEBUG,
  					"Considering cadidate auth tok:
  ");
  			ecryptfs_dump_auth_tok(candidate_auth_tok);
  		}

  		rc = ecryptfs_get_auth_tok_sig(&candidate_auth_tok_sig,
  					       candidate_auth_tok);
  		if (rc) {

  			printk(KERN_ERR
  			       "Unrecognized candidate auth tok type: [%d]
  ",
  			       candidate_auth_tok->token_type);
  			rc = -EINVAL;
  			goto out_wipe_list;
  		}

  		rc = ecryptfs_find_auth_tok_for_sig(&auth_tok_key,

  					       &matching_auth_tok,

  					       crypt_stat->mount_crypt_stat,

  					       candidate_auth_tok_sig);

  		if (!rc) {

  			found_auth_tok = 1;

  			goto found_matching_auth_tok;

  		}
  	}

  	if (!found_auth_tok) {

  		ecryptfs_printk(KERN_ERR, "Could not find a usable "
  				"authentication token
  ");

  		rc = -EIO;
  		goto out_wipe_list;

  	}

  found_matching_auth_tok:

  	if (candidate_auth_tok->token_type == ECRYPTFS_PRIVATE_KEY) {

  		memcpy(&(candidate_auth_tok->token.private_key),

  		       &(matching_auth_tok->token.private_key),

  		       sizeof(struct ecryptfs_private_key));

  		up_write(&(auth_tok_key->sem));
  		key_put(auth_tok_key);

  		rc = decrypt_pki_encrypted_session_key(candidate_auth_tok,

  						       crypt_stat);
  	} else if (candidate_auth_tok->token_type == ECRYPTFS_PASSWORD) {

  		memcpy(&(candidate_auth_tok->token.password),

  		       &(matching_auth_tok->token.password),

  		       sizeof(struct ecryptfs_password));

  		up_write(&(auth_tok_key->sem));
  		key_put(auth_tok_key);

  		rc = decrypt_passphrase_encrypted_session_key(
  			candidate_auth_tok, crypt_stat);

  	} else {
  		up_write(&(auth_tok_key->sem));
  		key_put(auth_tok_key);
  		rc = -EINVAL;

  	}
  	if (rc) {

  		struct ecryptfs_auth_tok_list_item *auth_tok_list_item_tmp;
  
  		ecryptfs_printk(KERN_WARNING, "Error decrypting the "
  				"session key for authentication token with sig "
  				"[%.*s]; rc = [%d]. Removing auth tok "
  				"candidate from the list and searching for "

  				"the next match.
  ", ECRYPTFS_SIG_SIZE_HEX,
  				candidate_auth_tok_sig,	rc);

  		list_for_each_entry_safe(auth_tok_list_item,
  					 auth_tok_list_item_tmp,
  					 &auth_tok_list, list) {
  			if (candidate_auth_tok
  			    == &auth_tok_list_item->auth_tok) {
  				list_del(&auth_tok_list_item->list);
  				kmem_cache_free(
  					ecryptfs_auth_tok_list_item_cache,
  					auth_tok_list_item);
  				goto find_next_matching_auth_tok;
  			}
  		}
  		BUG();

  	}
  	rc = ecryptfs_compute_root_iv(crypt_stat);
  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Error computing "
  				"the root IV
  ");
  		goto out_wipe_list;

  	}
  	rc = ecryptfs_init_crypt_ctx(crypt_stat);
  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Error initializing crypto "
  				"context for cipher [%s]; rc = [%d]
  ",
  				crypt_stat->cipher, rc);
  	}
  out_wipe_list:
  	wipe_auth_tok_list(&auth_tok_list);
  out:
  	return rc;
  }

  static int

  pki_encrypt_session_key(struct key *auth_tok_key,
  			struct ecryptfs_auth_tok *auth_tok,

  			struct ecryptfs_crypt_stat *crypt_stat,
  			struct ecryptfs_key_record *key_rec)
  {
  	struct ecryptfs_msg_ctx *msg_ctx = NULL;

  	char *payload = NULL;

  	size_t payload_len = 0;

  	struct ecryptfs_message *msg;
  	int rc;
  
  	rc = write_tag_66_packet(auth_tok->token.private_key.signature,

  				 ecryptfs_code_for_cipher_string(
  					 crypt_stat->cipher,
  					 crypt_stat->key_size),

  				 crypt_stat, &payload, &payload_len);

  	up_write(&(auth_tok_key->sem));
  	key_put(auth_tok_key);

  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Error generating tag 66 packet
  ");
  		goto out;
  	}

  	rc = ecryptfs_send_message(payload, payload_len, &msg_ctx);

  	if (rc) {

  		ecryptfs_printk(KERN_ERR, "Error sending message to "
  				"ecryptfsd
  ");

  		goto out;
  	}
  	rc = ecryptfs_wait_for_response(msg_ctx, &msg);
  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Failed to receive tag 67 packet "
  				"from the user space daemon
  ");
  		rc = -EIO;
  		goto out;
  	}
  	rc = parse_tag_67_packet(key_rec, msg);
  	if (rc)
  		ecryptfs_printk(KERN_ERR, "Error parsing tag 67 packet
  ");
  	kfree(msg);
  out:

  	kfree(payload);

  	return rc;
  }
  /**
   * write_tag_1_packet - Write an RFC2440-compatible tag 1 (public key) packet
   * @dest: Buffer into which to write the packet

   * @remaining_bytes: Maximum number of bytes that can be writtn

   * @auth_tok_key: The authentication token key to unlock and put when done with
   *                @auth_tok

   * @auth_tok: The authentication token used for generating the tag 1 packet
   * @crypt_stat: The cryptographic context
   * @key_rec: The key record struct for the tag 1 packet

   * @packet_size: This function will write the number of bytes that end
   *               up constituting the packet; set to zero on error
   *
   * Returns zero on success; non-zero on error.
   */
  static int

  write_tag_1_packet(char *dest, size_t *remaining_bytes,

  		   struct key *auth_tok_key, struct ecryptfs_auth_tok *auth_tok,

  		   struct ecryptfs_crypt_stat *crypt_stat,

  		   struct ecryptfs_key_record *key_rec, size_t *packet_size)
  {
  	size_t i;
  	size_t encrypted_session_key_valid = 0;

  	size_t packet_size_length;

  	size_t max_packet_size;

  	int rc = 0;
  
  	(*packet_size) = 0;
  	ecryptfs_from_hex(key_rec->sig, auth_tok->token.private_key.signature,
  			  ECRYPTFS_SIG_SIZE);
  	encrypted_session_key_valid = 0;
  	for (i = 0; i < crypt_stat->key_size; i++)
  		encrypted_session_key_valid |=
  			auth_tok->session_key.encrypted_key[i];
  	if (encrypted_session_key_valid) {
  		memcpy(key_rec->enc_key,
  		       auth_tok->session_key.encrypted_key,
  		       auth_tok->session_key.encrypted_key_size);

  		up_write(&(auth_tok_key->sem));
  		key_put(auth_tok_key);

  		goto encrypted_session_key_set;
  	}
  	if (auth_tok->session_key.encrypted_key_size == 0)
  		auth_tok->session_key.encrypted_key_size =
  			auth_tok->token.private_key.key_size;

  	rc = pki_encrypt_session_key(auth_tok_key, auth_tok, crypt_stat,
  				     key_rec);

  	if (rc) {

  		printk(KERN_ERR "Failed to encrypt session key via a key "
  		       "module; rc = [%d]
  ", rc);

  		goto out;
  	}
  	if (ecryptfs_verbosity > 0) {
  		ecryptfs_printk(KERN_DEBUG, "Encrypted key:
  ");
  		ecryptfs_dump_hex(key_rec->enc_key, key_rec->enc_key_size);
  	}
  encrypted_session_key_set:

  	/* This format is inspired by OpenPGP; see RFC 2440
  	 * packet tag 1 */
  	max_packet_size = (1                         /* Tag 1 identifier */
  			   + 3                       /* Max Tag 1 packet size */
  			   + 1                       /* Version */
  			   + ECRYPTFS_SIG_SIZE       /* Key identifier */
  			   + 1                       /* Cipher identifier */
  			   + key_rec->enc_key_size); /* Encrypted key size */
  	if (max_packet_size > (*remaining_bytes)) {
  		printk(KERN_ERR "Packet length larger than maximum allowable; "

  		       "need up to [%td] bytes, but there are only [%td] "

  		       "available
  ", max_packet_size, (*remaining_bytes));

  		rc = -EINVAL;
  		goto out;
  	}
  	dest[(*packet_size)++] = ECRYPTFS_TAG_1_PACKET_TYPE;

  	rc = ecryptfs_write_packet_length(&dest[(*packet_size)],
  					  (max_packet_size - 4),
  					  &packet_size_length);

  	if (rc) {
  		ecryptfs_printk(KERN_ERR, "Error generating tag 1 packet "
  				"header; cannot generate packet length
  ");
  		goto out;
  	}
  	(*packet_size) += packet_size_length;
  	dest[(*packet_size)++] = 0x03; /* version 3 */
  	memcpy(&dest[(*packet_size)], key_rec->sig, ECRYPTFS_SIG_SIZE);
  	(*packet_size) += ECRYPTFS_SIG_SIZE;
  	dest[(*packet_size)++] = RFC2440_CIPHER_RSA;
  	memcpy(&dest[(*packet_size)], key_rec->enc_key,
  	       key_rec->enc_key_size);
  	(*packet_size) += key_rec->enc_key_size;
  out:
  	if (rc)
  		(*packet_size) = 0;

  	else
  		(*remaining_bytes) -= (*packet_size);

  	return rc;
  }

  
  /**
   * write_tag_11_packet
   * @dest: Target into which Tag 11 packet is to be written

   * @remaining_bytes: Maximum packet length

   * @contents: Byte array of contents to copy in
   * @contents_length: Number of bytes in contents
   * @packet_length: Length of the Tag 11 packet written; zero on error
   *
   * Returns zero on success; non-zero on error.
   */
  static int

  write_tag_11_packet(char *dest, size_t *remaining_bytes, char *contents,

  		    size_t contents_length, size_t *packet_length)

  {

  	size_t packet_size_length;

  	size_t max_packet_size;

  	int rc = 0;

  
  	(*packet_length) = 0;

  	/* This format is inspired by OpenPGP; see RFC 2440
  	 * packet tag 11 */
  	max_packet_size = (1                   /* Tag 11 identifier */
  			   + 3                 /* Max Tag 11 packet size */
  			   + 1                 /* Binary format specifier */
  			   + 1                 /* Filename length */
  			   + 8                 /* Filename ("_CONSOLE") */
  			   + 4                 /* Modification date */
  			   + contents_length); /* Literal data */
  	if (max_packet_size > (*remaining_bytes)) {
  		printk(KERN_ERR "Packet length larger than maximum allowable; "

  		       "need up to [%td] bytes, but there are only [%td] "

  		       "available
  ", max_packet_size, (*remaining_bytes));

  		rc = -EINVAL;

  		goto out;
  	}

  	dest[(*packet_length)++] = ECRYPTFS_TAG_11_PACKET_TYPE;

  	rc = ecryptfs_write_packet_length(&dest[(*packet_length)],
  					  (max_packet_size - 4),
  					  &packet_size_length);

  	if (rc) {

  		printk(KERN_ERR "Error generating tag 11 packet header; cannot "
  		       "generate packet length. rc = [%d]
  ", rc);

  		goto out;
  	}
  	(*packet_length) += packet_size_length;

  	dest[(*packet_length)++] = 0x62; /* binary data format specifier */

  	dest[(*packet_length)++] = 8;
  	memcpy(&dest[(*packet_length)], "_CONSOLE", 8);
  	(*packet_length) += 8;

  	memset(&dest[(*packet_length)], 0x00, 4);
  	(*packet_length) += 4;

  	memcpy(&dest[(*packet_length)], contents, contents_length);
  	(*packet_length) += contents_length;
   out:
  	if (rc)
  		(*packet_length) = 0;

  	else
  		(*remaining_bytes) -= (*packet_length);

  	return rc;
  }
  
  /**
   * write_tag_3_packet
   * @dest: Buffer into which to write the packet

   * @remaining_bytes: Maximum number of bytes that can be written

   * @auth_tok: Authentication token
   * @crypt_stat: The cryptographic context
   * @key_rec: encrypted key
   * @packet_size: This function will write the number of bytes that end
   *               up constituting the packet; set to zero on error
   *
   * Returns zero on success; non-zero on error.
   */
  static int

  write_tag_3_packet(char *dest, size_t *remaining_bytes,
  		   struct ecryptfs_auth_tok *auth_tok,

  		   struct ecryptfs_crypt_stat *crypt_stat,
  		   struct ecryptfs_key_record *key_rec, size_t *packet_size)
  {

  	size_t i;

  	size_t encrypted_session_key_valid = 0;
  	char session_key_encryption_key[ECRYPTFS_MAX_KEY_BYTES];

  	struct scatterlist dst_sg[2];
  	struct scatterlist src_sg[2];

  	struct mutex *tfm_mutex = NULL;

  	u8 cipher_code;

  	size_t packet_size_length;
  	size_t max_packet_size;
  	struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
  		crypt_stat->mount_crypt_stat;

  	struct blkcipher_desc desc = {
  		.tfm = NULL,
  		.flags = CRYPTO_TFM_REQ_MAY_SLEEP
  	};
  	int rc = 0;

  
  	(*packet_size) = 0;

  	ecryptfs_from_hex(key_rec->sig, auth_tok->token.password.signature,

  			  ECRYPTFS_SIG_SIZE);

  	rc = ecryptfs_get_tfm_and_mutex_for_cipher_name(&desc.tfm, &tfm_mutex,
  							crypt_stat->cipher);
  	if (unlikely(rc)) {
  		printk(KERN_ERR "Internal error whilst attempting to get "
  		       "tfm and mutex for cipher name [%s]; rc = [%d]
  ",
  		       crypt_stat->cipher, rc);
  		goto out;
  	}
  	if (mount_crypt_stat->global_default_cipher_key_size == 0) {
  		struct blkcipher_alg *alg = crypto_blkcipher_alg(desc.tfm);
  
  		printk(KERN_WARNING "No key size specified at mount; "
  		       "defaulting to [%d]
  ", alg->max_keysize);
  		mount_crypt_stat->global_default_cipher_key_size =
  			alg->max_keysize;

  	}

  	if (crypt_stat->key_size == 0)
  		crypt_stat->key_size =
  			mount_crypt_stat->global_default_cipher_key_size;

  	if (auth_tok->session_key.encrypted_key_size == 0)
  		auth_tok->session_key.encrypted_key_size =
  			crypt_stat->key_size;
  	if (crypt_stat->key_size == 24
  	    && strcmp("aes", crypt_stat->cipher) == 0) {
  		memset((crypt_stat->key + 24), 0, 8);
  		auth_tok->session_key.encrypted_key_size = 32;

  	} else
  		auth_tok->session_key.encrypted_key_size = crypt_stat->key_size;

  	key_rec->enc_key_size =

  		auth_tok->session_key.encrypted_key_size;

  	encrypted_session_key_valid = 0;
  	for (i = 0; i < auth_tok->session_key.encrypted_key_size; i++)
  		encrypted_session_key_valid |=
  			auth_tok->session_key.encrypted_key[i];
  	if (encrypted_session_key_valid) {
  		ecryptfs_printk(KERN_DEBUG, "encrypted_session_key_valid != 0; "
  				"using auth_tok->session_key.encrypted_key, "

  				"where key_rec->enc_key_size = [%zd]
  ",

  				key_rec->enc_key_size);
  		memcpy(key_rec->enc_key,
  		       auth_tok->session_key.encrypted_key,
  		       key_rec->enc_key_size);
  		goto encrypted_session_key_set;
  	}

  	if (auth_tok->token.password.flags &
  	    ECRYPTFS_SESSION_KEY_ENCRYPTION_KEY_SET) {

  		ecryptfs_printk(KERN_DEBUG, "Using previously generated "
  				"session key encryption key of size [%d]
  ",
  				auth_tok->token.password.
  				session_key_encryption_key_bytes);
  		memcpy(session_key_encryption_key,
  		       auth_tok->token.password.session_key_encryption_key,
  		       crypt_stat->key_size);
  		ecryptfs_printk(KERN_DEBUG,

  				"Cached session key encryption key:
  ");

  		if (ecryptfs_verbosity > 0)
  			ecryptfs_dump_hex(session_key_encryption_key, 16);
  	}
  	if (unlikely(ecryptfs_verbosity > 0)) {
  		ecryptfs_printk(KERN_DEBUG, "Session key encryption key:
  ");
  		ecryptfs_dump_hex(session_key_encryption_key, 16);
  	}

  	rc = virt_to_scatterlist(crypt_stat->key, key_rec->enc_key_size,

  				 src_sg, 2);
  	if (rc < 1 || rc > 2) {

  		ecryptfs_printk(KERN_ERR, "Error generating scatterlist "

  				"for crypt_stat session key; expected rc = 1; "

  				"got rc = [%d]. key_rec->enc_key_size = [%zd]
  ",

  				rc, key_rec->enc_key_size);

  		rc = -ENOMEM;
  		goto out;
  	}

  	rc = virt_to_scatterlist(key_rec->enc_key, key_rec->enc_key_size,

  				 dst_sg, 2);
  	if (rc < 1 || rc > 2) {

  		ecryptfs_printk(KERN_ERR, "Error generating scatterlist "

  				"for crypt_stat encrypted session key; "
  				"expected rc = 1; got rc = [%d]. "

  				"key_rec->enc_key_size = [%zd]
  ", rc,

  				key_rec->enc_key_size);

  		rc = -ENOMEM;
  		goto out;
  	}

  	mutex_lock(tfm_mutex);

  	rc = crypto_blkcipher_setkey(desc.tfm, session_key_encryption_key,
  				     crypt_stat->key_size);

  	if (rc < 0) {

  		mutex_unlock(tfm_mutex);

  		ecryptfs_printk(KERN_ERR, "Error setting key for crypto "

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

  		goto out;
  	}
  	rc = 0;

  	ecryptfs_printk(KERN_DEBUG, "Encrypting [%zd] bytes of the key
  ",

  			crypt_stat->key_size);

  	rc = crypto_blkcipher_encrypt(&desc, dst_sg, src_sg,

  				      (*key_rec).enc_key_size);

  	mutex_unlock(tfm_mutex);

  	if (rc) {
  		printk(KERN_ERR "Error encrypting; rc = [%d]
  ", rc);
  		goto out;
  	}

  	ecryptfs_printk(KERN_DEBUG, "This should be the encrypted key:
  ");

  	if (ecryptfs_verbosity > 0) {

  		ecryptfs_printk(KERN_DEBUG, "EFEK of size [%zd]:
  ",

  				key_rec->enc_key_size);

  		ecryptfs_dump_hex(key_rec->enc_key,
  				  key_rec->enc_key_size);

  	}

  encrypted_session_key_set:
  	/* This format is inspired by OpenPGP; see RFC 2440
  	 * packet tag 3 */
  	max_packet_size = (1                         /* Tag 3 identifier */
  			   + 3                       /* Max Tag 3 packet size */
  			   + 1                       /* Version */
  			   + 1                       /* Cipher code */
  			   + 1                       /* S2K specifier */
  			   + 1                       /* Hash identifier */
  			   + ECRYPTFS_SALT_SIZE      /* Salt */
  			   + 1                       /* Hash iterations */
  			   + key_rec->enc_key_size); /* Encrypted key size */
  	if (max_packet_size > (*remaining_bytes)) {

  		printk(KERN_ERR "Packet too large; need up to [%td] bytes, but "
  		       "there are only [%td] available
  ", max_packet_size,

  		       (*remaining_bytes));

  		rc = -EINVAL;
  		goto out;
  	}

  	dest[(*packet_size)++] = ECRYPTFS_TAG_3_PACKET_TYPE;

  	/* Chop off the Tag 3 identifier(1) and Tag 3 packet size(3)
  	 * to get the number of octets in the actual Tag 3 packet */

  	rc = ecryptfs_write_packet_length(&dest[(*packet_size)],
  					  (max_packet_size - 4),
  					  &packet_size_length);

  	if (rc) {

  		printk(KERN_ERR "Error generating tag 3 packet header; cannot "
  		       "generate packet length. rc = [%d]
  ", rc);

  		goto out;
  	}
  	(*packet_size) += packet_size_length;
  	dest[(*packet_size)++] = 0x04; /* version 4 */

  	/* TODO: Break from RFC2440 so that arbitrary ciphers can be
  	 * specified with strings */

  	cipher_code = ecryptfs_code_for_cipher_string(crypt_stat->cipher,
  						      crypt_stat->key_size);

  	if (cipher_code == 0) {
  		ecryptfs_printk(KERN_WARNING, "Unable to generate code for "
  				"cipher [%s]
  ", crypt_stat->cipher);
  		rc = -EINVAL;
  		goto out;
  	}
  	dest[(*packet_size)++] = cipher_code;
  	dest[(*packet_size)++] = 0x03;	/* S2K */
  	dest[(*packet_size)++] = 0x01;	/* MD5 (TODO: parameterize) */
  	memcpy(&dest[(*packet_size)], auth_tok->token.password.salt,
  	       ECRYPTFS_SALT_SIZE);
  	(*packet_size) += ECRYPTFS_SALT_SIZE;	/* salt */
  	dest[(*packet_size)++] = 0x60;	/* hash iterations (65536) */

  	memcpy(&dest[(*packet_size)], key_rec->enc_key,
  	       key_rec->enc_key_size);
  	(*packet_size) += key_rec->enc_key_size;

  out:

  	if (rc)
  		(*packet_size) = 0;

  	else
  		(*remaining_bytes) -= (*packet_size);

  	return rc;
  }

  struct kmem_cache *ecryptfs_key_record_cache;

  /**
   * ecryptfs_generate_key_packet_set

   * @dest_base: Virtual address from which to write the key record set

   * @crypt_stat: The cryptographic context from which the
   *              authentication tokens will be retrieved
   * @ecryptfs_dentry: The dentry, used to retrieve the mount crypt stat
   *                   for the global parameters
   * @len: The amount written
   * @max: The maximum amount of data allowed to be written
   *
   * Generates a key packet set and writes it to the virtual address
   * passed in.
   *
   * Returns zero on success; non-zero on error.
   */
  int
  ecryptfs_generate_key_packet_set(char *dest_base,
  				 struct ecryptfs_crypt_stat *crypt_stat,
  				 struct dentry *ecryptfs_dentry, size_t *len,
  				 size_t max)
  {

  	struct ecryptfs_auth_tok *auth_tok;

  	struct key *auth_tok_key = NULL;

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

  	struct ecryptfs_key_record *key_rec;

  	struct ecryptfs_key_sig *key_sig;

  	int rc = 0;

  
  	(*len) = 0;

  	mutex_lock(&crypt_stat->keysig_list_mutex);

  	key_rec = kmem_cache_alloc(ecryptfs_key_record_cache, GFP_KERNEL);
  	if (!key_rec) {
  		rc = -ENOMEM;
  		goto out;
  	}

  	list_for_each_entry(key_sig, &crypt_stat->keysig_list,
  			    crypt_stat_list) {
  		memset(key_rec, 0, sizeof(*key_rec));

  		rc = ecryptfs_find_global_auth_tok_for_sig(&auth_tok_key,
  							   &auth_tok,

  							   mount_crypt_stat,
  							   key_sig->keysig);
  		if (rc) {

  			printk(KERN_WARNING "Unable to retrieve auth tok with "
  			       "sig = [%s]
  ", key_sig->keysig);
  			rc = process_find_global_auth_tok_for_sig_err(rc);

  			goto out_free;
  		}

  		if (auth_tok->token_type == ECRYPTFS_PASSWORD) {
  			rc = write_tag_3_packet((dest_base + (*len)),

  						&max, auth_tok,

  						crypt_stat, key_rec,

  						&written);

  			up_write(&(auth_tok_key->sem));
  			key_put(auth_tok_key);

  			if (rc) {
  				ecryptfs_printk(KERN_WARNING, "Error "
  						"writing tag 3 packet
  ");

  				goto out_free;

  			}
  			(*len) += written;
  			/* Write auth tok signature packet */

  			rc = write_tag_11_packet((dest_base + (*len)), &max,
  						 key_rec->sig,
  						 ECRYPTFS_SIG_SIZE, &written);

  			if (rc) {
  				ecryptfs_printk(KERN_ERR, "Error writing "
  						"auth tok signature packet
  ");

  				goto out_free;

  			}
  			(*len) += written;

  		} else if (auth_tok->token_type == ECRYPTFS_PRIVATE_KEY) {

  			rc = write_tag_1_packet(dest_base + (*len), &max,
  						auth_tok_key, auth_tok,

  						crypt_stat, key_rec, &written);

  			if (rc) {
  				ecryptfs_printk(KERN_WARNING, "Error "
  						"writing tag 1 packet
  ");

  				goto out_free;

  			}
  			(*len) += written;

  		} else {

  			up_write(&(auth_tok_key->sem));
  			key_put(auth_tok_key);

  			ecryptfs_printk(KERN_WARNING, "Unsupported "
  					"authentication token type
  ");
  			rc = -EINVAL;

  			goto out_free;

  		}

  	}
  	if (likely(max > 0)) {

  		dest_base[(*len)] = 0x00;
  	} else {
  		ecryptfs_printk(KERN_ERR, "Error writing boundary byte
  ");
  		rc = -EIO;
  	}

  out_free:
  	kmem_cache_free(ecryptfs_key_record_cache, key_rec);

  out:
  	if (rc)
  		(*len) = 0;

  	mutex_unlock(&crypt_stat->keysig_list_mutex);
  	return rc;
  }
  
  struct kmem_cache *ecryptfs_key_sig_cache;
  
  int ecryptfs_add_keysig(struct ecryptfs_crypt_stat *crypt_stat, char *sig)
  {
  	struct ecryptfs_key_sig *new_key_sig;

  
  	new_key_sig = kmem_cache_alloc(ecryptfs_key_sig_cache, GFP_KERNEL);
  	if (!new_key_sig) {

  		printk(KERN_ERR
  		       "Error allocating from ecryptfs_key_sig_cache
  ");

  		return -ENOMEM;

  	}
  	memcpy(new_key_sig->keysig, sig, ECRYPTFS_SIG_SIZE_HEX);

  	new_key_sig->keysig[ECRYPTFS_SIG_SIZE_HEX] = '\0';

  	/* Caller must hold keysig_list_mutex */

  	list_add(&new_key_sig->crypt_stat_list, &crypt_stat->keysig_list);

  
  	return 0;

  }

  
  struct kmem_cache *ecryptfs_global_auth_tok_cache;
  
  int
  ecryptfs_add_global_auth_tok(struct ecryptfs_mount_crypt_stat *mount_crypt_stat,

  			     char *sig, u32 global_auth_tok_flags)

  {
  	struct ecryptfs_global_auth_tok *new_auth_tok;
  	int rc = 0;

  	new_auth_tok = kmem_cache_zalloc(ecryptfs_global_auth_tok_cache,

  					GFP_KERNEL);
  	if (!new_auth_tok) {
  		rc = -ENOMEM;
  		printk(KERN_ERR "Error allocating from "
  		       "ecryptfs_global_auth_tok_cache
  ");
  		goto out;
  	}
  	memcpy(new_auth_tok->sig, sig, ECRYPTFS_SIG_SIZE_HEX);

  	new_auth_tok->flags = global_auth_tok_flags;

  	new_auth_tok->sig[ECRYPTFS_SIG_SIZE_HEX] = '\0';
  	mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
  	list_add(&new_auth_tok->mount_crypt_stat_list,
  		 &mount_crypt_stat->global_auth_tok_list);

  	mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
  out:
  	return rc;
  }