eCryptfs: use list_for_each_entry_safe() when wiping auth toks

[safe/jmp/linux-2.6] / fs / ecryptfs / 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.
 */
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
 */
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;
}

/**
 * decrypt_pki_encrypted_session_key - Decrypt the session key with
 * the given auth_tok.
 *
 * 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;

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

        /* we check that:
         *   one byte for the Tag 1 ID flag
         *   two bytes for the body size
         * do not exceed the maximum_packet_size
         */
        if (unlikely((*packet_size) + 3 > max_packet_size)) {
                ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
                rc = -EINVAL;
                goto out;
        }
        /* check for Tag 1 identifier - one byte */
        if (data[(*packet_size)++] != ECRYPTFS_TAG_1_PACKET_TYPE) {
                ecryptfs_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_alloc(ecryptfs_auth_tok_list_item_cache,
                                 GFP_KERNEL);
        if (!auth_tok_list_item) {
                ecryptfs_printk(KERN_ERR, "Unable to allocate memory\n");
                rc = -ENOMEM;
                goto out;
        }
        memset(auth_tok_list_item, 0,
               sizeof(struct ecryptfs_auth_tok_list_item));
        (*new_auth_tok) = &auth_tok_list_item->auth_tok;
        /* check for body size - one to two bytes
         *
         *              ***** TAG 1 Packet Format *****
         *    | version number                     | 1 byte       |
         *    | key ID                             | 8 bytes      |
         *    | public key algorithm               | 1 byte       |
         *    | encrypted session key              | arbitrary    |
         */
        rc = parse_packet_length(&data[(*packet_size)], &body_size,
                                 &length_size);
        if (rc) {
                ecryptfs_printk(KERN_WARNING, "Error parsing packet length; "
                                "rc = [%d]\n", rc);
                goto out_free;
        }
        if (unlikely(body_size < (0x02 + ECRYPTFS_SIG_SIZE))) {
                ecryptfs_printk(KERN_WARNING, "Invalid body size ([%d])\n",
                                body_size);
                rc = -EINVAL;
                goto out_free;
        }
        (*packet_size) += length_size;
        if (unlikely((*packet_size) + body_size > max_packet_size)) {
                ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
                rc = -EINVAL;
                goto out_free;
        }
        /* Version 3 (from RFC2440) - one byte */
        if (unlikely(data[(*packet_size)++] != 0x03)) {
                ecryptfs_printk(KERN_DEBUG, "Unknown version number "
                                "[%d]\n", data[(*packet_size) - 1]);
                rc = -EINVAL;
                goto out_free;
        }
        /* Read Signature */
        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 - (0x02 + ECRYPTFS_SIG_SIZE);
        if ((*new_auth_tok)->session_key.encrypted_key_size
            > ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES) {
                ecryptfs_printk(KERN_ERR, "Tag 1 packet contains key larger "
                                "than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES");
                rc = -EINVAL;
                goto out;
        }
        ecryptfs_printk(KERN_DEBUG, "Encrypted key size = [%d]\n",
                        (*new_auth_tok)->session_key.encrypted_key_size);
        memcpy((*new_auth_tok)->session_key.encrypted_key,
               &data[(*packet_size)], (body_size - 0x02 - ECRYPTFS_SIG_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_type = ECRYPTFS_PRIVATE_KEY;
        (*new_auth_tok)->flags |= ECRYPTFS_PRIVATE_KEY;
        /* TODO: Why are we setting this flag here? Don't we want the
         * 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_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;

        /* we check that:
         *   one byte for the Tag 3 ID flag
         *   two bytes for the body size
         * do not exceed the maximum_packet_size
         */
        if (unlikely((*packet_size) + 3 > max_packet_size)) {
                ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
                rc = -EINVAL;
                goto out;
        }

        /* check for Tag 3 identifyer - one byte */
        if (data[(*packet_size)++] != ECRYPTFS_TAG_3_PACKET_TYPE) {
                ecryptfs_printk(KERN_ERR, "Enter w/ first byte != 0x%.2x\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) {
                ecryptfs_printk(KERN_ERR, "Unable to allocate memory\n");
                rc = -ENOMEM;
                goto out;
        }
        (*new_auth_tok) = &auth_tok_list_item->auth_tok;

        /* check for body size - one to two bytes */
        rc = parse_packet_length(&data[(*packet_size)], &body_size,
                                 &length_size);
        if (rc) {
                ecryptfs_printk(KERN_WARNING, "Error parsing packet length; "
                                "rc = [%d]\n", rc);
                goto out_free;
        }
        if (unlikely(body_size < (0x05 + ECRYPTFS_SALT_SIZE))) {
                ecryptfs_printk(KERN_WARNING, "Invalid body size ([%d])\n",
                                body_size);
                rc = -EINVAL;
                goto out_free;
        }
        (*packet_size) += length_size;

        /* now we know the length of the remainting Tag 3 packet size:
         *   5 fix bytes for: version string, cipher, S2K ID, hash algo,
         *                    number of hash iterations
         *   ECRYPTFS_SALT_SIZE bytes for salt
         *   body_size bytes minus the stuff above is the encrypted key size
         */
        if (unlikely((*packet_size) + body_size > max_packet_size)) {
                ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
                rc = -EINVAL;
                goto out_free;
        }

        /* There are 5 characters of additional information in the
         * packet */
        (*new_auth_tok)->session_key.encrypted_key_size =
                body_size - (0x05 + ECRYPTFS_SALT_SIZE);
        ecryptfs_printk(KERN_DEBUG, "Encrypted key size = [%d]\n",
                        (*new_auth_tok)->session_key.encrypted_key_size);

        /* Version 4 (from RFC2440) - one byte */
        if (unlikely(data[(*packet_size)++] != 0x04)) {
                ecryptfs_printk(KERN_DEBUG, "Unknown version number "
                                "[%d]\n", data[(*packet_size) - 1]);
                rc = -EINVAL;
                goto out_free;
        }

        /* cipher - one byte */
        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);
        /* S2K identifier 3 (from RFC2440) */
        if (unlikely(data[(*packet_size)++] != 0x03)) {
                ecryptfs_printk(KERN_ERR, "Only S2K ID 3 is currently "
                                "supported\n");
                rc = -ENOSYS;
                goto out_free;
        }

        /* TODO: finish the hash mapping */
        /* hash algorithm - one byte */
        switch (data[(*packet_size)++]) {
        case 0x01: /* See RFC2440 for these numbers and their mappings */
                /* Choose MD5 */
                /* salt - ECRYPTFS_SALT_SIZE bytes */
                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 */
                /* number of hash iterations - one byte */
                (*new_auth_tok)->token.password.hash_iterations =
                        ((u32) 16 + (data[(*packet_size)] & 15))
                                << ((data[(*packet_size)] >> 4) + 6);
                (*packet_size)++;

                /* encrypted session key -
                 *   (body_size-5-ECRYPTFS_SALT_SIZE) bytes */
                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;
                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;

        /* check that:
         *   one byte for the Tag 11 ID flag
         *   two bytes for the Tag 11 length
         * do not exceed the maximum_packet_size
         */
        if (unlikely((*packet_size) + 3 > max_packet_size)) {
                ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
                rc = -EINVAL;
                goto out;
        }

        /* check for Tag 11 identifyer - one byte */
        if (data[(*packet_size)++] != ECRYPTFS_TAG_11_PACKET_TYPE) {
                ecryptfs_printk(KERN_WARNING,
                                "Invalid tag 11 packet format\n");
                rc = -EINVAL;
                goto out;
        }

        /* get Tag 11 content length - one or two bytes */
        rc = parse_packet_length(&data[(*packet_size)], &body_size,
                                 &length_size);
        if (rc) {
                ecryptfs_printk(KERN_WARNING,
                                "Invalid tag 11 packet format\n");
                goto out;
        }
        (*packet_size) += length_size;

        if (body_size < 13) {
                ecryptfs_printk(KERN_WARNING, "Invalid body size ([%d])\n",
                                body_size);
                rc = -EINVAL;
                goto out;
        }
        /* We have 13 bytes of surrounding packet values */
        (*tag_11_contents_size) = (body_size - 13);

        /* now we know the length of the remainting Tag 11 packet size:
         *   14 fix bytes for: special flag one, special flag two,
         *                     12 skipped bytes
         *   body_size bytes minus the stuff above is the Tag 11 content
         */
        /* FIXME why is the body size one byte smaller than the actual
         * size of the body?
         * this seems to be an error here as well as in
         * write_tag_11_packet() */
        if (unlikely((*packet_size) + body_size + 1 > max_packet_size)) {
                ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n");
                rc = -EINVAL;
                goto out;
        }

        /* special flag one - one byte */
        if (data[(*packet_size)++] != 0x62) {
                ecryptfs_printk(KERN_WARNING, "Unrecognizable packet\n");
                rc = -EINVAL;
                goto out;
        }

        /* special flag two - one byte */
        if (data[(*packet_size)++] != 0x08) {
                ecryptfs_printk(KERN_WARNING, "Unrecognizable packet\n");
                rc = -EINVAL;
                goto out;
        }

        /* skip the next 12 bytes */
        (*packet_size) += 12; /* We don't care about the filename or
                               * the timestamp */

        /* get the Tag 11 contents - tag_11_contents_size bytes */
        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.
 *
 * 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 = NULL;
        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]):\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;
        }
        if ((rc = virt_to_scatterlist(auth_tok->session_key.encrypted_key,
                                      auth_tok->session_key.encrypted_key_size,
                                      &src_sg, 1)) != 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;
        if ((rc = virt_to_scatterlist(auth_tok->session_key.decrypted_key,
                                      auth_tok->session_key.decrypted_key_size,
                                      &dst_sg, 1)) != 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;
}

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;
}

/**
 * ecryptfs_parse_packet_set
 * @dest: The header page in memory
 * @version: Version of file format, to guide parsing behavior
 *
 * 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 = NULL;
        struct ecryptfs_auth_tok *candidate_auth_tok = NULL;
        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);
                }
                if ((rc = ecryptfs_get_auth_tok_sig(&candidate_auth_tok_sig,
                                                    candidate_auth_tok))) {
                        printk(KERN_ERR
                               "Unrecognized candidate auth tok type: [%d]\n",
                               candidate_auth_tok->token_type);
                        rc = -EINVAL;
                        goto out_wipe_list;
                }
                if ((rc = ecryptfs_find_auth_tok_for_sig(
                             &matching_auth_tok, crypt_stat,
                             candidate_auth_tok_sig)))
                        rc = 0;
                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
 * @max: Maximum number of bytes that can be writtn
 * @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 [%d] bytes, but there are only [%d] "
                       "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
 * @max: 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, int max, char *contents, size_t contents_length,
                    size_t *packet_length)
{
        size_t packet_size_length;
        int rc = 0;

        (*packet_length) = 0;
        if ((13 + contents_length) > max) {
                rc = -EINVAL;
                ecryptfs_printk(KERN_ERR, "Packet length larger than "
                                "maximum allowable\n");
                goto out;
        }
        /* General packet header */
        /* Packet tag */
        dest[(*packet_length)++] = ECRYPTFS_TAG_11_PACKET_TYPE;
        /* Packet length */
        rc = write_packet_length(&dest[(*packet_length)],
                                 (13 + contents_length), &packet_size_length);
        if (rc) {
                ecryptfs_printk(KERN_ERR, "Error generating tag 11 packet "
                                "header; cannot generate packet length\n");
                goto out;
        }
        (*packet_length) += packet_size_length;
        /* Tag 11 specific */
        /* One-octet field that describes how the data is formatted */
        dest[(*packet_length)++] = 0x62; /* binary data */
        /* One-octet filename length followed by filename */
        dest[(*packet_length)++] = 8;
        memcpy(&dest[(*packet_length)], "_CONSOLE", 8);
        (*packet_length) += 8;
        /* Four-octet number indicating modification date */
        memset(&dest[(*packet_length)], 0x00, 4);
        (*packet_length) += 4;
        /* Remainder is literal data */
        memcpy(&dest[(*packet_length)], contents, contents_length);
        (*packet_length) += contents_length;
 out:
        if (rc)
                (*packet_length) = 0;
        return rc;
}

/**
 * write_tag_3_packet
 * @dest: Buffer into which to write the packet
 * @max: 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);
        }
        if ((rc = virt_to_scatterlist(crypt_stat->key,
                                      key_rec->enc_key_size, &src_sg, 1))
            != 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;
        }
        if ((rc = virt_to_scatterlist(key_rec->enc_key,
                                      key_rec->enc_key_size, &dst_sg, 1))
            != 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 [%d] bytes, but "
                       "there are only [%d] 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: 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_alloc(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;
}