/**
* 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;
}
