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keystore.c

/**
 * 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 "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\n");
            rc = -ENOENT;
            break;
      case EKEYEXPIRED:
            ecryptfs_printk(KERN_WARNING, "Key expired\n");
            rc = -ETIME;
            break;
      case EKEYREVOKED:
            ecryptfs_printk(KERN_WARNING, "Key revoked\n");
            rc = -EINVAL;
            break;
      default:
            ecryptfs_printk(KERN_WARNING, "Unknown error code: "
                        "[0x%.16x]\n", err_code);
            rc = -EINVAL;
      }
      return rc;
}

/**
 * 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
 */
static int 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\n");
            rc = -EINVAL;
            goto out;
      } else {
            ecryptfs_printk(KERN_ERR, "Error parsing packet length\n");
            rc = -EINVAL;
            goto out;
      }
out:
      return rc;
}

/**
 * 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.
 */
static int 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: [%d]\n", 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\n");
            rc = -ENOMEM;
            goto out;
      }
      message[i++] = ECRYPTFS_TAG_64_PACKET_TYPE;
      rc = 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\n");
            goto out;
      }
      i += packet_size_len;
      memcpy(&message[i], signature, ECRYPTFS_SIG_SIZE_HEX);
      i += ECRYPTFS_SIG_SIZE_HEX;
      rc = 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\n");
            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, u16 *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\n");
            rc = -EIO;
            goto out;
      }
      if (data[i++]) {
            ecryptfs_printk(KERN_ERR, "Status indicator has non-zero value "
                        "[%d]\n", data[i-1]);
            rc = -EIO;
            goto out;
      }
      rc = parse_packet_length(&data[i], &m_size, &data_len);
      if (rc) {
            ecryptfs_printk(KERN_WARNING, "Error parsing packet length; "
                        "rc = [%d]\n", rc);
            goto out;
      }
      i += data_len;
      if (message_len < (i + m_size)) {
            ecryptfs_printk(KERN_ERR, "The received netlink message is "
                        "shorter than expected\n");
            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\n");
            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]\n",
                        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]\n", expected_checksum, checksum);
            rc = -EIO;
      }
out:
      return rc;
}


static int
write_tag_66_packet(char *signature, size_t 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\n");
            rc = -ENOMEM;
            goto out;
      }
      message[i++] = ECRYPTFS_TAG_66_PACKET_TYPE;
      rc = 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\n");
            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 = 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\n");
            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;
            goto out;
      }
      if (data[i++] != ECRYPTFS_TAG_67_PACKET_TYPE) {
            ecryptfs_printk(KERN_ERR, "Type should be ECRYPTFS_TAG_67\n");
            rc = -EIO;
            goto out;
      }
      if (data[i++]) {
            ecryptfs_printk(KERN_ERR, "Status indicator has non zero value"
                        " [%d]\n", data[i-1]);
            rc = -EIO;
            goto out;
      }
      rc = parse_packet_length(&data[i], &key_rec->enc_key_size, &data_len);
      if (rc) {
            ecryptfs_printk(KERN_WARNING, "Error parsing packet length; "
                        "rc = [%d]\n", rc);
            goto out;
      }
      i += data_len;
      if (message_len < (i + key_rec->enc_key_size)) {
            ecryptfs_printk(KERN_ERR, "message_len [%d]; max len is [%d]\n",
                        message_len, (i + key_rec->enc_key_size));
            rc = -EIO;
            goto out;
      }
      if (key_rec->enc_key_size > ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES) {
            ecryptfs_printk(KERN_ERR, "Encrypted key_size [%d] larger than "
                        "the maximum key size [%d]\n",
                        key_rec->enc_key_size,
                        ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES);
            rc = -EIO;
            goto out;
      }
      memcpy(key_rec->enc_key, &data[i], key_rec->enc_key_size);
out:
      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]\n",
                   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)
{
      u16 cipher_code = 0;
      struct ecryptfs_msg_ctx *msg_ctx;
      struct ecryptfs_message *msg = NULL;
      char *auth_tok_sig;
      char *netlink_message;
      size_t netlink_message_length;
      int rc;

      rc = ecryptfs_get_auth_tok_sig(&auth_tok_sig, auth_tok);
      if (rc) {
            printk(KERN_ERR "Unrecognized auth tok type: [%d]\n",
                   auth_tok->token_type);
            goto out;
      }
      rc = write_tag_64_packet(auth_tok_sig, &(auth_tok->session_key),
                         &netlink_message, &netlink_message_length);
      if (rc) {
            ecryptfs_printk(KERN_ERR, "Failed to write tag 64 packet");
            goto out;
      }
      rc = ecryptfs_send_message(ecryptfs_transport, netlink_message,
                           netlink_message_length, &msg_ctx);
      if (rc) {
            ecryptfs_printk(KERN_ERR, "Error sending netlink message\n");
            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\n");
            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]\n",
                   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\n",
                        cipher_code)
            goto out;
      }
      crypt_stat->flags |= ECRYPTFS_KEY_VALID;
      if (ecryptfs_verbosity > 0) {
            ecryptfs_printk(KERN_DEBUG, "Decrypted session key:\n");
            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\n");
            rc = -EINVAL;
            goto out;
      }
      if (data[(*packet_size)++] != ECRYPTFS_TAG_1_PACKET_TYPE) {
            printk(KERN_ERR "Enter w/ first byte != 0x%.2x\n",
                   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\n");
            rc = -ENOMEM;
            goto out;
      }
      (*new_auth_tok) = &auth_tok_list_item->auth_tok;
      rc = parse_packet_length(&data[(*packet_size)], &body_size,
                         &length_size);
      if (rc) {
            printk(KERN_WARNING "Error parsing packet length; "
                   "rc = [%d]\n", rc);
            goto out_free;
      }
      if (unlikely(body_size < (ECRYPTFS_SIG_SIZE + 2))) {
            printk(KERN_WARNING "Invalid body size ([%td])\n", 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\n");
            rc = -EINVAL;
            goto out_free;
      }
      if (unlikely(data[(*packet_size)++] != 0x03)) {
            printk(KERN_WARNING "Unknown version number [%d]\n",
                   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\n");
            rc = -EINVAL;
            goto out;
      }
      if (data[(*packet_size)++] != ECRYPTFS_TAG_3_PACKET_TYPE) {
            printk(KERN_ERR "First byte != 0x%.2x; invalid packet\n",
                   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\n");
            rc = -ENOMEM;
            goto out;
      }
      (*new_auth_tok) = &auth_tok_list_item->auth_tok;
      rc = parse_packet_length(&data[(*packet_size)], &body_size,
                         &length_size);
      if (rc) {
            printk(KERN_WARNING "Error parsing packet length; rc = [%d]\n",
                   rc);
            goto out_free;
      }
      if (unlikely(body_size < (ECRYPTFS_SALT_SIZE + 5))) {
            printk(KERN_WARNING "Invalid body size ([%td])\n", 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\n");
            rc = -EINVAL;
            goto out_free;
      }
      (*new_auth_tok)->session_key.encrypted_key_size =
            (body_size - (ECRYPTFS_SALT_SIZE + 5));
      if (unlikely(data[(*packet_size)++] != 0x04)) {
            printk(KERN_WARNING "Unknown version number [%d]\n",
                   data[(*packet_size) - 1]);
            rc = -EINVAL;
            goto out_free;
      }
      ecryptfs_cipher_code_to_string(crypt_stat->cipher,
                               (u16)data[(*packet_size)]);
      /* 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;
      }
      ecryptfs_init_crypt_ctx(crypt_stat);
      if (unlikely(data[(*packet_size)++] != 0x03)) {
            printk(KERN_WARNING "Only S2K ID 3 is currently supported\n");
            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]\n", 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\n");
            rc = -EINVAL;
            goto out;
      }
      if (data[(*packet_size)++] != ECRYPTFS_TAG_11_PACKET_TYPE) {
            printk(KERN_WARNING "Invalid tag 11 packet format\n");
            rc = -EINVAL;
            goto out;
      }
      rc = parse_packet_length(&data[(*packet_size)], &body_size,
                         &length_size);
      if (rc) {
            printk(KERN_WARNING "Invalid tag 11 packet format\n");
            goto out;
      }
      if (body_size < 14) {
            printk(KERN_WARNING "Invalid body size ([%td])\n", 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\n");
            rc = -EINVAL;
            goto out;
      }
      if (data[(*packet_size)++] != 0x62) {
            printk(KERN_WARNING "Unrecognizable packet\n");
            rc = -EINVAL;
            goto out;
      }
      if (data[(*packet_size)++] != 0x08) {
            printk(KERN_WARNING "Unrecognizable packet\n");
            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;
}

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

      (*global_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) == 0) {
                  (*global_auth_tok) = walker;
                  goto out;
            }
      }
      rc = -EINVAL;
out:
      mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
      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]\n",
                        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]\n",
                        ECRYPTFS_VERSION_MINOR, minor);
            rc = -EINVAL;
            goto out;
      }
out:
      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)) {
            printk(KERN_ERR "Could not find key with description: [%s]\n",
                   sig);
            process_request_key_err(PTR_ERR(*auth_tok_key));
            rc = -EINVAL;
            goto out;
      }
      (*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]\n",
                   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\n");
            rc = -EINVAL;
            goto out;
      }
out:
      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 ecryptfs_auth_tok **auth_tok,
      struct ecryptfs_crypt_stat *crypt_stat, char *sig)
{
      struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
            crypt_stat->mount_crypt_stat;
      struct ecryptfs_global_auth_tok *global_auth_tok;
      int rc = 0;

      (*auth_tok) = NULL;
      if (ecryptfs_find_global_auth_tok_for_sig(&global_auth_tok,
                                      mount_crypt_stat, sig)) {
            struct key *auth_tok_key;

            rc = ecryptfs_keyring_auth_tok_for_sig(&auth_tok_key, auth_tok,
                                           sig);
      } else
            (*auth_tok) = global_auth_tok->global_auth_tok;
      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;
      struct scatterlist src_sg;
      struct mutex *tfm_mutex;
      struct blkcipher_desc desc = {
            .flags = CRYPTO_TFM_REQ_MAY_SLEEP
      };
      int rc = 0;

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

      if (unlikely(ecryptfs_verbosity > 0)) {
            ecryptfs_printk(
                  KERN_DEBUG, "Session key encryption key (size [%d]):\n",
                  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]\n",
                   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, 1);
      if (rc != 1) {
            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]\n", 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, 1);
      if (rc != 1) {
            printk(KERN_ERR "Internal error whilst attempting to convert "
                  "auth_tok->session_key.decrypted_key to scatterlist; "
                  "expected rc = 1; got rc = [%d]\n", 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\n");
            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]\n", 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 [%d]:\n",
                        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;
      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\n");
                        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\n");
                        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 [%d]\n",
                                    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\n");
                        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)\n");
                  rc = -EIO;
                  goto out_wipe_list;
                  break;
            default:
                  ecryptfs_printk(KERN_DEBUG, "No packet at offset "
                              "[%d] of the file header; hex value of "
                              "character is [0x%.2x]\n", 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\n");
            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:\n");
                  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]\n",
                         candidate_auth_tok->token_type);
                  rc = -EINVAL;
                  goto out_wipe_list;
            }
            ecryptfs_find_auth_tok_for_sig(&matching_auth_tok, crypt_stat,
                                     candidate_auth_tok_sig);
            if (matching_auth_tok) {
                  found_auth_tok = 1;
                  goto found_matching_auth_tok;
            }
      }
      if (!found_auth_tok) {
            ecryptfs_printk(KERN_ERR, "Could not find a usable "
                        "authentication token\n");
            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));
            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));
            rc = decrypt_passphrase_encrypted_session_key(
                  candidate_auth_tok, crypt_stat);
      }
      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.\n", candidate_auth_tok_sig,
                        ECRYPTFS_SIG_SIZE_HEX, 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\n");
            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]\n",
                        crypt_stat->cipher, rc);
      }
out_wipe_list:
      wipe_auth_tok_list(&auth_tok_list);
out:
      return rc;
}

static int
pki_encrypt_session_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 *netlink_payload;
      size_t netlink_payload_length;
      struct ecryptfs_message *msg;
      int rc;

      rc = write_tag_66_packet(auth_tok->token.private_key.signature,
                         ecryptfs_code_for_cipher_string(crypt_stat),
                         crypt_stat, &netlink_payload,
                         &netlink_payload_length);
      if (rc) {
            ecryptfs_printk(KERN_ERR, "Error generating tag 66 packet\n");
            goto out;
      }
      rc = ecryptfs_send_message(ecryptfs_transport, netlink_payload,
                           netlink_payload_length, &msg_ctx);
      if (rc) {
            ecryptfs_printk(KERN_ERR, "Error sending netlink message\n");
            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\n");
            rc = -EIO;
            goto out;
      }
      rc = parse_tag_67_packet(key_rec, msg);
      if (rc)
            ecryptfs_printk(KERN_ERR, "Error parsing tag 67 packet\n");
      kfree(msg);
out:
      if (netlink_payload)
            kfree(netlink_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: 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 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);
            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, crypt_stat, key_rec);
      if (rc) {
            ecryptfs_printk(KERN_ERR, "Failed to encrypt session key "
                        "via a pki");
            goto out;
      }
      if (ecryptfs_verbosity > 0) {
            ecryptfs_printk(KERN_DEBUG, "Encrypted key:\n");
            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\n", max_packet_size, (*remaining_bytes));
            rc = -EINVAL;
            goto out;
      }
      dest[(*packet_size)++] = ECRYPTFS_TAG_1_PACKET_TYPE;
      rc = 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\n");
            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\n", max_packet_size, (*remaining_bytes));
            rc = -EINVAL;
            goto out;
      }
      dest[(*packet_length)++] = ECRYPTFS_TAG_11_PACKET_TYPE;
      rc = 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]\n", 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;
      struct scatterlist src_sg;
      struct mutex *tfm_mutex = NULL;
      size_t 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]\n",
                   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]\n", 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 = [%d]\n",
                        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]\n",
                        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: \n");
            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:\n");
            ecryptfs_dump_hex(session_key_encryption_key, 16);
      }
      rc = virt_to_scatterlist(crypt_stat->key, key_rec->enc_key_size,
                         &src_sg, 1);
      if (rc != 1) {
            ecryptfs_printk(KERN_ERR, "Error generating scatterlist "
                        "for crypt_stat session key; expected rc = 1; "
                        "got rc = [%d]. key_rec->enc_key_size = [%d]\n",
                        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, 1);
      if (rc != 1) {
            ecryptfs_printk(KERN_ERR, "Error generating scatterlist "
                        "for crypt_stat encrypted session key; "
                        "expected rc = 1; got rc = [%d]. "
                        "key_rec->enc_key_size = [%d]\n", 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]\n", rc);
            goto out;
      }
      rc = 0;
      ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes of the key\n",
                  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]\n", rc);
            goto out;
      }
      ecryptfs_printk(KERN_DEBUG, "This should be the encrypted key:\n");
      if (ecryptfs_verbosity > 0) {
            ecryptfs_printk(KERN_DEBUG, "EFEK of size [%d]:\n",
                        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\n", 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 = 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]\n", 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);
      if (cipher_code == 0) {
            ecryptfs_printk(KERN_WARNING, "Unable to generate code for "
                        "cipher [%s]\n", 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 ecryptfs_global_auth_tok *global_auth_tok;
      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(&global_auth_tok,
                                             mount_crypt_stat,
                                             key_sig->keysig);
            if (rc) {
                  printk(KERN_ERR "Error attempting to get the global "
                         "auth_tok; rc = [%d]\n", rc);
                  goto out_free;
            }
            if (global_auth_tok->flags & ECRYPTFS_AUTH_TOK_INVALID) {
                  printk(KERN_WARNING
                         "Skipping invalid auth tok with sig = [%s]\n",
                         global_auth_tok->sig);
                  continue;
            }
            auth_tok = global_auth_tok->global_auth_tok;
            if (auth_tok->token_type == ECRYPTFS_PASSWORD) {
                  rc = write_tag_3_packet((dest_base + (*len)),
                                    &max, auth_tok,
                                    crypt_stat, key_rec,
                                    &written);
                  if (rc) {
                        ecryptfs_printk(KERN_WARNING, "Error "
                                    "writing tag 3 packet\n");
                        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\n");
                        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,
                                    crypt_stat, key_rec, &written);
                  if (rc) {
                        ecryptfs_printk(KERN_WARNING, "Error "
                                    "writing tag 1 packet\n");
                        goto out_free;
                  }
                  (*len) += written;
            } else {
                  ecryptfs_printk(KERN_WARNING, "Unsupported "
                              "authentication token type\n");
                  rc = -EINVAL;
                  goto out_free;
            }
      }
      if (likely(max > 0)) {
            dest_base[(*len)] = 0x00;
      } else {
            ecryptfs_printk(KERN_ERR, "Error writing boundary byte\n");
            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;
      int rc = 0;

      new_key_sig = kmem_cache_alloc(ecryptfs_key_sig_cache, GFP_KERNEL);
      if (!new_key_sig) {
            rc = -ENOMEM;
            printk(KERN_ERR
                   "Error allocating from ecryptfs_key_sig_cache\n");
            goto out;
      }
      memcpy(new_key_sig->keysig, sig, ECRYPTFS_SIG_SIZE_HEX);
      mutex_lock(&crypt_stat->keysig_list_mutex);
      list_add(&new_key_sig->crypt_stat_list, &crypt_stat->keysig_list);
      mutex_unlock(&crypt_stat->keysig_list_mutex);
out:
      return rc;
}

struct kmem_cache *ecryptfs_global_auth_tok_cache;

int
ecryptfs_add_global_auth_tok(struct ecryptfs_mount_crypt_stat *mount_crypt_stat,
                       char *sig)
{
      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\n");
            goto out;
      }
      memcpy(new_auth_tok->sig, sig, ECRYPTFS_SIG_SIZE_HEX);
      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);
      mount_crypt_stat->num_global_auth_toks++;
      mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
out:
      return rc;
}


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