Linux 2.6.19.7

[linux-2.6/suspend2-2.6.19.git] / 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>
 *
 * 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/sched.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;
}

static void wipe_auth_tok_list(struct list_head *auth_tok_list_head)
{
        struct list_head *walker;
        struct ecryptfs_auth_tok_list_item *auth_tok_list_item;

        walker = auth_tok_list_head->next;
        while (walker != auth_tok_list_head) {
                auth_tok_list_item =
                    list_entry(walker, struct ecryptfs_auth_tok_list_item,
                               list);
                walker = auth_tok_list_item->list.next;
                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);
        }
}

struct kmem_cache *ecryptfs_auth_tok_list_item_cache;

/**
 * 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) = data[0];
                (*length_size) = 1;
        } else if (data[0] < 224) {
                /* Two-byte length */
                (*size) = ((data[0] - 192) * 256);
                (*size) += (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;
}

/**
 * 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)
{
        int rc = 0;
        size_t body_size;
        struct ecryptfs_auth_tok_list_item *auth_tok_list_item;
        size_t length_size;

        (*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_alloc(ecryptfs_auth_tok_list_item_cache, SLAB_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 */
        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. */
        ECRYPTFS_CLEAR_FLAG((*new_auth_tok)->session_key.flags,
                            ECRYPTFS_USERSPACE_SHOULD_TRY_TO_DECRYPT);
        ECRYPTFS_CLEAR_FLAG((*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)
{
        int rc = 0;
        size_t body_size;
        size_t length_size;

        (*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;
}

/**
 * decrypt_session_key - Decrypt the session key with the given auth_tok.
 *
 * Returns Zero on success; non-zero error otherwise.
 */
static int decrypt_session_key(struct ecryptfs_auth_tok *auth_tok,
                               struct ecryptfs_crypt_stat *crypt_stat)
{
        struct ecryptfs_password *password_s_ptr;
        struct scatterlist src_sg[2], dst_sg[2];
        struct mutex *tfm_mutex = NULL;
        /* TODO: Use virt_to_scatterlist for these */
        char *encrypted_session_key;
        char *session_key;
        struct blkcipher_desc desc = {
                .flags = CRYPTO_TFM_REQ_MAY_SLEEP
        };
        int rc = 0;

        password_s_ptr = &auth_tok->token.password;
        if (ECRYPTFS_CHECK_FLAG(password_s_ptr->flags,
                                ECRYPTFS_SESSION_KEY_ENCRYPTION_KEY_SET))
                ecryptfs_printk(KERN_DEBUG, "Session key encryption key "
                                "set; skipping key generation\n");
        ecryptfs_printk(KERN_DEBUG, "Session key encryption key (size [%d])"
                        ":\n",
                        password_s_ptr->session_key_encryption_key_bytes);
        if (ecryptfs_verbosity > 0)
                ecryptfs_dump_hex(password_s_ptr->session_key_encryption_key,
                                  password_s_ptr->
                                  session_key_encryption_key_bytes);
        if (!strcmp(crypt_stat->cipher,
                    crypt_stat->mount_crypt_stat->global_default_cipher_name)
            && crypt_stat->mount_crypt_stat->global_key_tfm) {
                desc.tfm = crypt_stat->mount_crypt_stat->global_key_tfm;
                tfm_mutex = &crypt_stat->mount_crypt_stat->global_key_tfm_mutex;
        } else {
                char *full_alg_name;

                rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
                                                            crypt_stat->cipher,
                                                            "ecb");
                if (rc)
                        goto out;
                desc.tfm = crypto_alloc_blkcipher(full_alg_name, 0,
                                                  CRYPTO_ALG_ASYNC);
                kfree(full_alg_name);
                if (IS_ERR(desc.tfm)) {
                        rc = PTR_ERR(desc.tfm);
                        printk(KERN_ERR "Error allocating crypto context; "
                               "rc = [%d]\n", rc);
                        goto out;
                }
                crypto_blkcipher_set_flags(desc.tfm, CRYPTO_TFM_REQ_WEAK_KEY);
        }
        if (tfm_mutex)
                mutex_lock(tfm_mutex);
        rc = crypto_blkcipher_setkey(desc.tfm,
                                     password_s_ptr->session_key_encryption_key,
                                     crypt_stat->key_size);
        if (rc < 0) {
                printk(KERN_ERR "Error setting key for crypto context\n");
                rc = -EINVAL;
                goto out_free_tfm;
        }
        /* TODO: virt_to_scatterlist */
        encrypted_session_key = (char *)__get_free_page(GFP_KERNEL);
        if (!encrypted_session_key) {
                ecryptfs_printk(KERN_ERR, "Out of memory\n");
                rc = -ENOMEM;
                goto out_free_tfm;
        }
        session_key = (char *)__get_free_page(GFP_KERNEL);
        if (!session_key) {
                kfree(encrypted_session_key);
                ecryptfs_printk(KERN_ERR, "Out of memory\n");
                rc = -ENOMEM;
                goto out_free_tfm;
        }
        memcpy(encrypted_session_key, auth_tok->session_key.encrypted_key,
               auth_tok->session_key.encrypted_key_size);
        src_sg[0].page = virt_to_page(encrypted_session_key);
        src_sg[0].offset = 0;
        BUG_ON(auth_tok->session_key.encrypted_key_size > PAGE_CACHE_SIZE);
        src_sg[0].length = auth_tok->session_key.encrypted_key_size;
        dst_sg[0].page = virt_to_page(session_key);
        dst_sg[0].offset = 0;
        auth_tok->session_key.decrypted_key_size =
            auth_tok->session_key.encrypted_key_size;
        dst_sg[0].length = auth_tok->session_key.encrypted_key_size;
        rc = crypto_blkcipher_decrypt(&desc, dst_sg, src_sg,
                                      auth_tok->session_key.encrypted_key_size);
        if (rc) {
                printk(KERN_ERR "Error decrypting; rc = [%d]\n", rc);
                goto out_free_memory;
        }
        auth_tok->session_key.decrypted_key_size =
            auth_tok->session_key.encrypted_key_size;
        memcpy(auth_tok->session_key.decrypted_key, session_key,
               auth_tok->session_key.decrypted_key_size);
        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);
        ECRYPTFS_SET_FLAG(crypt_stat->flags, ECRYPTFS_KEY_VALID);
        ecryptfs_printk(KERN_DEBUG, "Decrypted session key:\n");
        if (ecryptfs_verbosity > 0)
                ecryptfs_dump_hex(crypt_stat->key,
                                  crypt_stat->key_size);
out_free_memory:
        memset(encrypted_session_key, 0, PAGE_CACHE_SIZE);
        free_page((unsigned long)encrypted_session_key);
        memset(session_key, 0, PAGE_CACHE_SIZE);
        free_page((unsigned long)session_key);
out_free_tfm:
        if (tfm_mutex)
                mutex_unlock(tfm_mutex);
        else
                crypto_free_blkcipher(desc.tfm);
out:
        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;
        int rc = 0;
        size_t found_auth_tok = 0;
        size_t next_packet_is_auth_tok_packet;
        char sig[ECRYPTFS_SIG_SIZE_HEX];
        struct list_head auth_tok_list;
        struct list_head *walker;
        struct ecryptfs_auth_tok *chosen_auth_tok = NULL;
        struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
                &ecryptfs_superblock_to_private(
                        ecryptfs_dentry->d_sb)->mount_crypt_stat;
        struct ecryptfs_auth_tok *candidate_auth_tok = NULL;
        size_t packet_size;
        struct ecryptfs_auth_tok *new_auth_tok;
        unsigned char sig_tmp_space[ECRYPTFS_SIG_SIZE];
        size_t tag_11_contents_size;
        size_t tag_11_packet_size;

        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';
                        ECRYPTFS_SET_FLAG(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)) {
                rc = -EINVAL; /* Do not support non-encrypted files in
                               * the 0.1 release */
                goto out;
        }
        /* If we have a global auth tok, then we should try to use
         * it */
        if (mount_crypt_stat->global_auth_tok) {
                memcpy(sig, mount_crypt_stat->global_auth_tok_sig,
                       ECRYPTFS_SIG_SIZE_HEX);
                chosen_auth_tok = mount_crypt_stat->global_auth_tok;
        } else
                BUG(); /* We should always have a global auth tok in
                        * the 0.1 release */
        /* Scan list to see if our chosen_auth_tok works */
        list_for_each(walker, &auth_tok_list) {
                struct ecryptfs_auth_tok_list_item *auth_tok_list_item;
                auth_tok_list_item =
                    list_entry(walker, struct ecryptfs_auth_tok_list_item,
                               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);
                }
                /* TODO: Replace ECRYPTFS_SIG_SIZE_HEX w/ dynamic value */
                if (candidate_auth_tok->token_type == ECRYPTFS_PASSWORD
                    && !strncmp(candidate_auth_tok->token.password.signature,
                                sig, ECRYPTFS_SIG_SIZE_HEX)) {
                        found_auth_tok = 1;
                        goto leave_list;
                        /* TODO: Transfer the common salt into the
                         * crypt_stat salt */
                }
        }
leave_list:
        if (!found_auth_tok) {
                ecryptfs_printk(KERN_ERR, "Could not find authentication "
                                "token on temporary list for sig [%.*s]\n",
                                ECRYPTFS_SIG_SIZE_HEX, sig);
                rc = -EIO;
                goto out_wipe_list;
        } else {
                memcpy(&(candidate_auth_tok->token.password),
                       &(chosen_auth_tok->token.password),
                       sizeof(struct ecryptfs_password));
                rc = decrypt_session_key(candidate_auth_tok, crypt_stat);
                if (rc) {
                        ecryptfs_printk(KERN_ERR, "Error decrypting the "
                                        "session key\n");
                        goto out_wipe_list;
                }
                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;
}

/**
 * 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)
{
        int rc = 0;
        size_t packet_size_length;

        (*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 max, 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 signature_is_valid = 0;
        size_t encrypted_session_key_valid = 0;
        char session_key_encryption_key[ECRYPTFS_MAX_KEY_BYTES];
        struct scatterlist dest_sg[2];
        struct scatterlist src_sg[2];
        struct mutex *tfm_mutex = NULL;
        size_t key_rec_size;
        size_t packet_size_length;
        size_t cipher_code;
        struct blkcipher_desc desc = {
                .tfm = NULL,
                .flags = CRYPTO_TFM_REQ_MAY_SLEEP
        };
        int rc = 0;

        (*packet_size) = 0;
        /* Check for a valid signature on the auth_tok */
        for (i = 0; i < ECRYPTFS_SIG_SIZE_HEX; i++)
                signature_is_valid |= auth_tok->token.password.signature[i];
        if (!signature_is_valid)
                BUG();
        ecryptfs_from_hex((*key_rec).sig, auth_tok->token.password.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 =
                        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;
        }
        (*key_rec).enc_key_size =
                auth_tok->session_key.encrypted_key_size;
        if (ECRYPTFS_CHECK_FLAG(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, 2);
        if (!rc) {
                ecryptfs_printk(KERN_ERR, "Error generating scatterlist "
                                "for crypt_stat session key\n");
                rc = -ENOMEM;
                goto out;
        }
        rc = virt_to_scatterlist((*key_rec).enc_key,
                                 (*key_rec).enc_key_size, dest_sg, 2);
        if (!rc) {
                ecryptfs_printk(KERN_ERR, "Error generating scatterlist "
                                "for crypt_stat encrypted session key\n");
                rc = -ENOMEM;
                goto out;
        }
        if (!strcmp(crypt_stat->cipher,
                    crypt_stat->mount_crypt_stat->global_default_cipher_name)
            && crypt_stat->mount_crypt_stat->global_key_tfm) {
                desc.tfm = crypt_stat->mount_crypt_stat->global_key_tfm;
                tfm_mutex = &crypt_stat->mount_crypt_stat->global_key_tfm_mutex;
        } else {
                char *full_alg_name;

                rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
                                                            crypt_stat->cipher,
                                                            "ecb");
                if (rc)
                        goto out;
                desc.tfm = crypto_alloc_blkcipher(full_alg_name, 0,
                                                  CRYPTO_ALG_ASYNC);
                kfree(full_alg_name);
                if (IS_ERR(desc.tfm)) {
                        rc = PTR_ERR(desc.tfm);
                        ecryptfs_printk(KERN_ERR, "Could not initialize crypto "
                                        "context for cipher [%s]; rc = [%d]\n",
                                        crypt_stat->cipher, rc);
                        goto out;
                }
                crypto_blkcipher_set_flags(desc.tfm, CRYPTO_TFM_REQ_WEAK_KEY);
        }
        if (tfm_mutex)
                mutex_lock(tfm_mutex);
        rc = crypto_blkcipher_setkey(desc.tfm, session_key_encryption_key,
                                     crypt_stat->key_size);
        if (rc < 0) {
                if (tfm_mutex)
                        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, dest_sg, src_sg,
                                      (*key_rec).enc_key_size);
        if (rc) {
                printk(KERN_ERR "Error encrypting; rc = [%d]\n", rc);
                goto out;
        }
        if (tfm_mutex)
                mutex_unlock(tfm_mutex);
        ecryptfs_printk(KERN_DEBUG, "This should be the encrypted key:\n");
        if (ecryptfs_verbosity > 0)
                ecryptfs_dump_hex((*key_rec).enc_key,
                                  (*key_rec).enc_key_size);
encrypted_session_key_set:
        /* Now we have a valid key_rec.  Append it to the
         * key_rec set. */
        key_rec_size = (sizeof(struct ecryptfs_key_record)
                        - ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES
                        + ((*key_rec).enc_key_size));
        /* TODO: Include a packet size limit as a parameter to this
         * function once we have multi-packet headers (for versions
         * later than 0.1 */
        if (key_rec_size >= ECRYPTFS_MAX_KEYSET_SIZE) {
                ecryptfs_printk(KERN_ERR, "Keyset too large\n");
                rc = -EINVAL;
                goto out;
        }
        /* TODO: Packet size limit */
        /* We have 5 bytes of surrounding packet data */
        if ((0x05 + ECRYPTFS_SALT_SIZE
             + (*key_rec).enc_key_size) >= max) {
                ecryptfs_printk(KERN_ERR, "Authentication token is too "
                                "large\n");
                rc = -EINVAL;
                goto out;
        }
        /* This format is inspired by OpenPGP; see RFC 2440
         * packet tag 3 */
        dest[(*packet_size)++] = ECRYPTFS_TAG_3_PACKET_TYPE;
        /* ver+cipher+s2k+hash+salt+iter+enc_key */
        rc = write_packet_length(&dest[(*packet_size)],
                                 (0x05 + ECRYPTFS_SALT_SIZE
                                  + (*key_rec).enc_key_size),
                                 &packet_size_length);
        if (rc) {
                ecryptfs_printk(KERN_ERR, "Error generating tag 3 packet "
                                "header; cannot generate packet length\n");
                goto out;
        }
        (*packet_size) += packet_size_length;
        dest[(*packet_size)++] = 0x04; /* version 4 */
        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 (desc.tfm && !tfm_mutex)
                crypto_free_blkcipher(desc.tfm);
        if (rc)
                (*packet_size) = 0;
        return rc;
}

/**
 * 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)
{
        int rc = 0;
        struct ecryptfs_auth_tok *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;

        (*len) = 0;
        if (mount_crypt_stat->global_auth_tok) {
                auth_tok = mount_crypt_stat->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;
                        }
                        (*len) += written;
                        /* Write auth tok signature packet */
                        rc = write_tag_11_packet(
                                (dest_base + (*len)),
                                (max - (*len)),
                                key_rec.sig, ECRYPTFS_SIG_SIZE, &written);
                        if (rc) {
                                ecryptfs_printk(KERN_ERR, "Error writing "
                                                "auth tok signature packet\n");
                                goto out;
                        }
                        (*len) += written;
                } else {
                        ecryptfs_printk(KERN_WARNING, "Unsupported "
                                        "authentication token type\n");
                        rc = -EINVAL;
                        goto out;
                }
                if (rc) {
                        ecryptfs_printk(KERN_WARNING, "Error writing "
                                        "authentication token packet with sig "
                                        "= [%s]\n",
                                        mount_crypt_stat->global_auth_tok_sig);
                        rc = -EIO;
                        goto out;
                }
        } else
                BUG();
        if (likely((max - (*len)) > 0)) {
                dest_base[(*len)] = 0x00;
        } else {
                ecryptfs_printk(KERN_ERR, "Error writing boundary byte\n");
                rc = -EIO;
        }
out:
        if (rc)
                (*len) = 0;
        return rc;
}