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crypto.c
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crypto.c
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/**
* eCryptfs: Linux filesystem encryption layer
*
* Copyright (C) 1997-2004 Erez Zadok
* Copyright (C) 2001-2004 Stony Brook University
* Copyright (C) 2004-2006 International Business Machines Corp.
* Author(s): Michael A. Halcrow <[email protected]>
* Michael C. Thompson <[email protected]>
*
* 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/fs.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/random.h>
#include <linux/compiler.h>
#include <linux/key.h>
#include <linux/namei.h>
#include <linux/crypto.h>
#include <linux/file.h>
#include <linux/scatterlist.h>
#include "ecryptfs_kernel.h"
static int
ecryptfs_decrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
struct page *dst_page, int dst_offset,
struct page *src_page, int src_offset, int size,
unsigned char *iv);
static int
ecryptfs_encrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
struct page *dst_page, int dst_offset,
struct page *src_page, int src_offset, int size,
unsigned char *iv);
/**
* ecryptfs_to_hex
* @dst: Buffer to take hex character representation of contents of
* src; must be at least of size (src_size * 2)
* @src: Buffer to be converted to a hex string respresentation
* @src_size: number of bytes to convert
*/
void ecryptfs_to_hex(char *dst, char *src, size_t src_size)
{
int x;
for (x = 0; x < src_size; x++)
sprintf(&dst[x * 2], "%.2x", (unsigned char)src[x]);
}
/**
* ecryptfs_from_hex
* @dst: Buffer to take the bytes from src hex; must be at least of
* size (src_size / 2)
* @src: Buffer to be converted from a hex string respresentation to raw value
* @dst_size: size of dst buffer, or number of hex characters pairs to convert
*/
void ecryptfs_from_hex(char *dst, char *src, int dst_size)
{
int x;
char tmp[3] = { 0, };
for (x = 0; x < dst_size; x++) {
tmp[0] = src[x * 2];
tmp[1] = src[x * 2 + 1];
dst[x] = (unsigned char)simple_strtol(tmp, NULL, 16);
}
}
/**
* ecryptfs_calculate_md5 - calculates the md5 of @src
* @dst: Pointer to 16 bytes of allocated memory
* @crypt_stat: Pointer to crypt_stat struct for the current inode
* @src: Data to be md5'd
* @len: Length of @src
*
* Uses the allocated crypto context that crypt_stat references to
* generate the MD5 sum of the contents of src.
*/
static int ecryptfs_calculate_md5(char *dst,
struct ecryptfs_crypt_stat *crypt_stat,
char *src, int len)
{
struct scatterlist sg;
struct hash_desc desc = {
.tfm = crypt_stat->hash_tfm,
.flags = CRYPTO_TFM_REQ_MAY_SLEEP
};
int rc = 0;
mutex_lock(&crypt_stat->cs_hash_tfm_mutex);
sg_init_one(&sg, (u8 *)src, len);
if (!desc.tfm) {
desc.tfm = crypto_alloc_hash(ECRYPTFS_DEFAULT_HASH, 0,
CRYPTO_ALG_ASYNC);
if (IS_ERR(desc.tfm)) {
rc = PTR_ERR(desc.tfm);
ecryptfs_printk(KERN_ERR, "Error attempting to "
"allocate crypto context; rc = [%d]\n",
rc);
goto out;
}
crypt_stat->hash_tfm = desc.tfm;
}
crypto_hash_init(&desc);
crypto_hash_update(&desc, &sg, len);
crypto_hash_final(&desc, dst);
mutex_unlock(&crypt_stat->cs_hash_tfm_mutex);
out:
return rc;
}
int ecryptfs_crypto_api_algify_cipher_name(char **algified_name,
char *cipher_name,
char *chaining_modifier)
{
int cipher_name_len = strlen(cipher_name);
int chaining_modifier_len = strlen(chaining_modifier);
int algified_name_len;
int rc;
algified_name_len = (chaining_modifier_len + cipher_name_len + 3);
(*algified_name) = kmalloc(algified_name_len, GFP_KERNEL);
if (!(*algified_name)) {
rc = -ENOMEM;
goto out;
}
snprintf((*algified_name), algified_name_len, "%s(%s)",
chaining_modifier, cipher_name);
rc = 0;
out:
return rc;
}
/**
* ecryptfs_derive_iv
* @iv: destination for the derived iv vale
* @crypt_stat: Pointer to crypt_stat struct for the current inode
* @offset: Offset of the page whose's iv we are to derive
*
* Generate the initialization vector from the given root IV and page
* offset.
*
* Returns zero on success; non-zero on error.
*/
static int ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
pgoff_t offset)
{
int rc = 0;
char dst[MD5_DIGEST_SIZE];
char src[ECRYPTFS_MAX_IV_BYTES + 16];
if (unlikely(ecryptfs_verbosity > 0)) {
ecryptfs_printk(KERN_DEBUG, "root iv:\n");
ecryptfs_dump_hex(crypt_stat->root_iv, crypt_stat->iv_bytes);
}
/* TODO: It is probably secure to just cast the least
* significant bits of the root IV into an unsigned long and
* add the offset to that rather than go through all this
* hashing business. -Halcrow */
memcpy(src, crypt_stat->root_iv, crypt_stat->iv_bytes);
memset((src + crypt_stat->iv_bytes), 0, 16);
snprintf((src + crypt_stat->iv_bytes), 16, "%ld", offset);
if (unlikely(ecryptfs_verbosity > 0)) {
ecryptfs_printk(KERN_DEBUG, "source:\n");
ecryptfs_dump_hex(src, (crypt_stat->iv_bytes + 16));
}
rc = ecryptfs_calculate_md5(dst, crypt_stat, src,
(crypt_stat->iv_bytes + 16));
if (rc) {
ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
"MD5 while generating IV for a page\n");
goto out;
}
memcpy(iv, dst, crypt_stat->iv_bytes);
if (unlikely(ecryptfs_verbosity > 0)) {
ecryptfs_printk(KERN_DEBUG, "derived iv:\n");
ecryptfs_dump_hex(iv, crypt_stat->iv_bytes);
}
out:
return rc;
}
/**
* ecryptfs_init_crypt_stat
* @crypt_stat: Pointer to the crypt_stat struct to initialize.
*
* Initialize the crypt_stat structure.
*/
void
ecryptfs_init_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
{
memset((void *)crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
mutex_init(&crypt_stat->cs_mutex);
mutex_init(&crypt_stat->cs_tfm_mutex);
mutex_init(&crypt_stat->cs_hash_tfm_mutex);
ECRYPTFS_SET_FLAG(crypt_stat->flags, ECRYPTFS_STRUCT_INITIALIZED);
}
/**
* ecryptfs_destruct_crypt_stat
* @crypt_stat: Pointer to the crypt_stat struct to initialize.
*
* Releases all memory associated with a crypt_stat struct.
*/
void ecryptfs_destruct_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
{
if (crypt_stat->tfm)
crypto_free_blkcipher(crypt_stat->tfm);
if (crypt_stat->hash_tfm)
crypto_free_hash(crypt_stat->hash_tfm);
memset(crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
}
void ecryptfs_destruct_mount_crypt_stat(
struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
if (mount_crypt_stat->global_auth_tok_key)
key_put(mount_crypt_stat->global_auth_tok_key);
if (mount_crypt_stat->global_key_tfm)
crypto_free_blkcipher(mount_crypt_stat->global_key_tfm);
memset(mount_crypt_stat, 0, sizeof(struct ecryptfs_mount_crypt_stat));
}
/**
* virt_to_scatterlist
* @addr: Virtual address
* @size: Size of data; should be an even multiple of the block size
* @sg: Pointer to scatterlist array; set to NULL to obtain only
* the number of scatterlist structs required in array
* @sg_size: Max array size
*
* Fills in a scatterlist array with page references for a passed
* virtual address.
*
* Returns the number of scatterlist structs in array used
*/
int virt_to_scatterlist(const void *addr, int size, struct scatterlist *sg,
int sg_size)
{
int i = 0;
struct page *pg;
int offset;
int remainder_of_page;
while (size > 0 && i < sg_size) {
pg = virt_to_page(addr);
offset = offset_in_page(addr);
if (sg) {
sg[i].page = pg;
sg[i].offset = offset;
}
remainder_of_page = PAGE_CACHE_SIZE - offset;
if (size >= remainder_of_page) {
if (sg)
sg[i].length = remainder_of_page;
addr += remainder_of_page;
size -= remainder_of_page;
} else {
if (sg)
sg[i].length = size;
addr += size;
size = 0;
}
i++;
}
if (size > 0)
return -ENOMEM;
return i;
}
/**
* encrypt_scatterlist
* @crypt_stat: Pointer to the crypt_stat struct to initialize.
* @dest_sg: Destination of encrypted data
* @src_sg: Data to be encrypted
* @size: Length of data to be encrypted
* @iv: iv to use during encryption
*
* Returns the number of bytes encrypted; negative value on error
*/
static int encrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
struct scatterlist *dest_sg,
struct scatterlist *src_sg, int size,
unsigned char *iv)
{
struct blkcipher_desc desc = {
.tfm = crypt_stat->tfm,
.info = iv,
.flags = CRYPTO_TFM_REQ_MAY_SLEEP
};
int rc = 0;
BUG_ON(!crypt_stat || !crypt_stat->tfm
|| !ECRYPTFS_CHECK_FLAG(crypt_stat->flags,
ECRYPTFS_STRUCT_INITIALIZED));
if (unlikely(ecryptfs_verbosity > 0)) {
ecryptfs_printk(KERN_DEBUG, "Key size [%d]; key:\n",
crypt_stat->key_size);
ecryptfs_dump_hex(crypt_stat->key,
crypt_stat->key_size);
}
/* Consider doing this once, when the file is opened */
mutex_lock(&crypt_stat->cs_tfm_mutex);
rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
crypt_stat->key_size);
if (rc) {
ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
rc);
mutex_unlock(&crypt_stat->cs_tfm_mutex);
rc = -EINVAL;
goto out;
}
ecryptfs_printk(KERN_DEBUG, "Encrypting [%d] bytes.\n", size);
crypto_blkcipher_encrypt_iv(&desc, dest_sg, src_sg, size);
mutex_unlock(&crypt_stat->cs_tfm_mutex);
out:
return rc;
}
static void
ecryptfs_extent_to_lwr_pg_idx_and_offset(unsigned long *lower_page_idx,
int *byte_offset,
struct ecryptfs_crypt_stat *crypt_stat,
unsigned long extent_num)
{
unsigned long lower_extent_num;
int extents_occupied_by_headers_at_front;
int bytes_occupied_by_headers_at_front;
int extent_offset;
int extents_per_page;
bytes_occupied_by_headers_at_front =
( crypt_stat->header_extent_size
* crypt_stat->num_header_extents_at_front );
extents_occupied_by_headers_at_front =
( bytes_occupied_by_headers_at_front
/ crypt_stat->extent_size );
lower_extent_num = extents_occupied_by_headers_at_front + extent_num;
extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
(*lower_page_idx) = lower_extent_num / extents_per_page;
extent_offset = lower_extent_num % extents_per_page;
(*byte_offset) = extent_offset * crypt_stat->extent_size;
ecryptfs_printk(KERN_DEBUG, " * crypt_stat->header_extent_size = "
"[%d]\n", crypt_stat->header_extent_size);
ecryptfs_printk(KERN_DEBUG, " * crypt_stat->"
"num_header_extents_at_front = [%d]\n",
crypt_stat->num_header_extents_at_front);
ecryptfs_printk(KERN_DEBUG, " * extents_occupied_by_headers_at_"
"front = [%d]\n", extents_occupied_by_headers_at_front);
ecryptfs_printk(KERN_DEBUG, " * lower_extent_num = [0x%.16x]\n",
lower_extent_num);
ecryptfs_printk(KERN_DEBUG, " * extents_per_page = [%d]\n",
extents_per_page);
ecryptfs_printk(KERN_DEBUG, " * (*lower_page_idx) = [0x%.16x]\n",
(*lower_page_idx));
ecryptfs_printk(KERN_DEBUG, " * extent_offset = [%d]\n",
extent_offset);
ecryptfs_printk(KERN_DEBUG, " * (*byte_offset) = [%d]\n",
(*byte_offset));
}
static int ecryptfs_write_out_page(struct ecryptfs_page_crypt_context *ctx,
struct page *lower_page,
struct inode *lower_inode,
int byte_offset_in_page, int bytes_to_write)
{
int rc = 0;
if (ctx->mode == ECRYPTFS_PREPARE_COMMIT_MODE) {
rc = ecryptfs_commit_lower_page(lower_page, lower_inode,
ctx->param.lower_file,
byte_offset_in_page,
bytes_to_write);
if (rc) {
ecryptfs_printk(KERN_ERR, "Error calling lower "
"commit; rc = [%d]\n", rc);
goto out;
}
} else {
rc = ecryptfs_writepage_and_release_lower_page(lower_page,
lower_inode,
ctx->param.wbc);
if (rc) {
ecryptfs_printk(KERN_ERR, "Error calling lower "
"writepage(); rc = [%d]\n", rc);
goto out;
}
}
out:
return rc;
}
static int ecryptfs_read_in_page(struct ecryptfs_page_crypt_context *ctx,
struct page **lower_page,
struct inode *lower_inode,
unsigned long lower_page_idx,
int byte_offset_in_page)
{
int rc = 0;
if (ctx->mode == ECRYPTFS_PREPARE_COMMIT_MODE) {
/* TODO: Limit this to only the data extents that are
* needed */
rc = ecryptfs_get_lower_page(lower_page, lower_inode,
ctx->param.lower_file,
lower_page_idx,
byte_offset_in_page,
(PAGE_CACHE_SIZE
- byte_offset_in_page));
if (rc) {
ecryptfs_printk(
KERN_ERR, "Error attempting to grab, map, "
"and prepare_write lower page with index "
"[0x%.16x]; rc = [%d]\n", lower_page_idx, rc);
goto out;
}
} else {
rc = ecryptfs_grab_and_map_lower_page(lower_page, NULL,
lower_inode,
lower_page_idx);
if (rc) {
ecryptfs_printk(
KERN_ERR, "Error attempting to grab and map "
"lower page with index [0x%.16x]; rc = [%d]\n",
lower_page_idx, rc);
goto out;
}
}
out:
return rc;
}
/**
* ecryptfs_encrypt_page
* @ctx: The context of the page
*
* Encrypt an eCryptfs page. This is done on a per-extent basis. Note
* that eCryptfs pages may straddle the lower pages -- for instance,
* if the file was created on a machine with an 8K page size
* (resulting in an 8K header), and then the file is copied onto a
* host with a 32K page size, then when reading page 0 of the eCryptfs
* file, 24K of page 0 of the lower file will be read and decrypted,
* and then 8K of page 1 of the lower file will be read and decrypted.
*
* The actual operations performed on each page depends on the
* contents of the ecryptfs_page_crypt_context struct.
*
* Returns zero on success; negative on error
*/
int ecryptfs_encrypt_page(struct ecryptfs_page_crypt_context *ctx)
{
char extent_iv[ECRYPTFS_MAX_IV_BYTES];
unsigned long base_extent;
unsigned long extent_offset = 0;
unsigned long lower_page_idx = 0;
unsigned long prior_lower_page_idx = 0;
struct page *lower_page;
struct inode *lower_inode;
struct ecryptfs_inode_info *inode_info;
struct ecryptfs_crypt_stat *crypt_stat;
int rc = 0;
int lower_byte_offset = 0;
int orig_byte_offset = 0;
int num_extents_per_page;
#define ECRYPTFS_PAGE_STATE_UNREAD 0
#define ECRYPTFS_PAGE_STATE_READ 1
#define ECRYPTFS_PAGE_STATE_MODIFIED 2
#define ECRYPTFS_PAGE_STATE_WRITTEN 3
int page_state;
lower_inode = ecryptfs_inode_to_lower(ctx->page->mapping->host);
inode_info = ecryptfs_inode_to_private(ctx->page->mapping->host);
crypt_stat = &inode_info->crypt_stat;
if (!ECRYPTFS_CHECK_FLAG(crypt_stat->flags, ECRYPTFS_ENCRYPTED)) {
rc = ecryptfs_copy_page_to_lower(ctx->page, lower_inode,
ctx->param.lower_file);
if (rc)
ecryptfs_printk(KERN_ERR, "Error attempting to copy "
"page at index [0x%.16x]\n",
ctx->page->index);
goto out;
}
num_extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
base_extent = (ctx->page->index * num_extents_per_page);
page_state = ECRYPTFS_PAGE_STATE_UNREAD;
while (extent_offset < num_extents_per_page) {
ecryptfs_extent_to_lwr_pg_idx_and_offset(
&lower_page_idx, &lower_byte_offset, crypt_stat,
(base_extent + extent_offset));
if (prior_lower_page_idx != lower_page_idx
&& page_state == ECRYPTFS_PAGE_STATE_MODIFIED) {
rc = ecryptfs_write_out_page(ctx, lower_page,
lower_inode,
orig_byte_offset,
(PAGE_CACHE_SIZE
- orig_byte_offset));
if (rc) {
ecryptfs_printk(KERN_ERR, "Error attempting "
"to write out page; rc = [%d]"
"\n", rc);
goto out;
}
page_state = ECRYPTFS_PAGE_STATE_WRITTEN;
}
if (page_state == ECRYPTFS_PAGE_STATE_UNREAD
|| page_state == ECRYPTFS_PAGE_STATE_WRITTEN) {
rc = ecryptfs_read_in_page(ctx, &lower_page,
lower_inode, lower_page_idx,
lower_byte_offset);
if (rc) {
ecryptfs_printk(KERN_ERR, "Error attempting "
"to read in lower page with "
"index [0x%.16x]; rc = [%d]\n",
lower_page_idx, rc);
goto out;
}
orig_byte_offset = lower_byte_offset;
prior_lower_page_idx = lower_page_idx;
page_state = ECRYPTFS_PAGE_STATE_READ;
}
BUG_ON(!(page_state == ECRYPTFS_PAGE_STATE_MODIFIED
|| page_state == ECRYPTFS_PAGE_STATE_READ));
rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
(base_extent + extent_offset));
if (rc) {
ecryptfs_printk(KERN_ERR, "Error attempting to "
"derive IV for extent [0x%.16x]; "
"rc = [%d]\n",
(base_extent + extent_offset), rc);
goto out;
}
if (unlikely(ecryptfs_verbosity > 0)) {
ecryptfs_printk(KERN_DEBUG, "Encrypting extent "
"with iv:\n");
ecryptfs_dump_hex(extent_iv, crypt_stat->iv_bytes);
ecryptfs_printk(KERN_DEBUG, "First 8 bytes before "
"encryption:\n");
ecryptfs_dump_hex((char *)
(page_address(ctx->page)
+ (extent_offset
* crypt_stat->extent_size)), 8);
}
rc = ecryptfs_encrypt_page_offset(
crypt_stat, lower_page, lower_byte_offset, ctx->page,
(extent_offset * crypt_stat->extent_size),
crypt_stat->extent_size, extent_iv);
ecryptfs_printk(KERN_DEBUG, "Encrypt extent [0x%.16x]; "
"rc = [%d]\n",
(base_extent + extent_offset), rc);
if (unlikely(ecryptfs_verbosity > 0)) {
ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
"encryption:\n");
ecryptfs_dump_hex((char *)(page_address(lower_page)
+ lower_byte_offset), 8);
}
page_state = ECRYPTFS_PAGE_STATE_MODIFIED;
extent_offset++;
}
BUG_ON(orig_byte_offset != 0);
rc = ecryptfs_write_out_page(ctx, lower_page, lower_inode, 0,
(lower_byte_offset
+ crypt_stat->extent_size));
if (rc) {
ecryptfs_printk(KERN_ERR, "Error attempting to write out "
"page; rc = [%d]\n", rc);
goto out;
}
out:
return rc;
}
/**
* ecryptfs_decrypt_page
* @file: The ecryptfs file
* @page: The page in ecryptfs to decrypt
*
* Decrypt an eCryptfs page. This is done on a per-extent basis. Note
* that eCryptfs pages may straddle the lower pages -- for instance,
* if the file was created on a machine with an 8K page size
* (resulting in an 8K header), and then the file is copied onto a
* host with a 32K page size, then when reading page 0 of the eCryptfs
* file, 24K of page 0 of the lower file will be read and decrypted,
* and then 8K of page 1 of the lower file will be read and decrypted.
*
* Returns zero on success; negative on error
*/
int ecryptfs_decrypt_page(struct file *file, struct page *page)
{
char extent_iv[ECRYPTFS_MAX_IV_BYTES];
unsigned long base_extent;
unsigned long extent_offset = 0;
unsigned long lower_page_idx = 0;
unsigned long prior_lower_page_idx = 0;
struct page *lower_page;
char *lower_page_virt = NULL;
struct inode *lower_inode;
struct ecryptfs_crypt_stat *crypt_stat;
int rc = 0;
int byte_offset;
int num_extents_per_page;
int page_state;
crypt_stat = &(ecryptfs_inode_to_private(
page->mapping->host)->crypt_stat);
lower_inode = ecryptfs_inode_to_lower(page->mapping->host);
if (!ECRYPTFS_CHECK_FLAG(crypt_stat->flags, ECRYPTFS_ENCRYPTED)) {
rc = ecryptfs_do_readpage(file, page, page->index);
if (rc)
ecryptfs_printk(KERN_ERR, "Error attempting to copy "
"page at index [0x%.16x]\n",
page->index);
goto out;
}
num_extents_per_page = PAGE_CACHE_SIZE / crypt_stat->extent_size;
base_extent = (page->index * num_extents_per_page);
lower_page_virt = kmem_cache_alloc(ecryptfs_lower_page_cache,
GFP_KERNEL);
if (!lower_page_virt) {
rc = -ENOMEM;
ecryptfs_printk(KERN_ERR, "Error getting page for encrypted "
"lower page(s)\n");
goto out;
}
lower_page = virt_to_page(lower_page_virt);
page_state = ECRYPTFS_PAGE_STATE_UNREAD;
while (extent_offset < num_extents_per_page) {
ecryptfs_extent_to_lwr_pg_idx_and_offset(
&lower_page_idx, &byte_offset, crypt_stat,
(base_extent + extent_offset));
if (prior_lower_page_idx != lower_page_idx
|| page_state == ECRYPTFS_PAGE_STATE_UNREAD) {
rc = ecryptfs_do_readpage(file, lower_page,
lower_page_idx);
if (rc) {
ecryptfs_printk(KERN_ERR, "Error reading "
"lower encrypted page; rc = "
"[%d]\n", rc);
goto out;
}
prior_lower_page_idx = lower_page_idx;
page_state = ECRYPTFS_PAGE_STATE_READ;
}
rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
(base_extent + extent_offset));
if (rc) {
ecryptfs_printk(KERN_ERR, "Error attempting to "
"derive IV for extent [0x%.16x]; rc = "
"[%d]\n",
(base_extent + extent_offset), rc);
goto out;
}
if (unlikely(ecryptfs_verbosity > 0)) {
ecryptfs_printk(KERN_DEBUG, "Decrypting extent "
"with iv:\n");
ecryptfs_dump_hex(extent_iv, crypt_stat->iv_bytes);
ecryptfs_printk(KERN_DEBUG, "First 8 bytes before "
"decryption:\n");
ecryptfs_dump_hex((lower_page_virt + byte_offset), 8);
}
rc = ecryptfs_decrypt_page_offset(crypt_stat, page,
(extent_offset
* crypt_stat->extent_size),
lower_page, byte_offset,
crypt_stat->extent_size,
extent_iv);
if (rc != crypt_stat->extent_size) {
ecryptfs_printk(KERN_ERR, "Error attempting to "
"decrypt extent [0x%.16x]\n",
(base_extent + extent_offset));
goto out;
}
rc = 0;
if (unlikely(ecryptfs_verbosity > 0)) {
ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
"decryption:\n");
ecryptfs_dump_hex((char *)(page_address(page)
+ byte_offset), 8);
}
extent_offset++;
}
out:
if (lower_page_virt)
kmem_cache_free(ecryptfs_lower_page_cache, lower_page_virt);
return rc;
}
/**
* decrypt_scatterlist
*
* Returns the number of bytes decrypted; negative value on error
*/
static int decrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
struct scatterlist *dest_sg,
struct scatterlist *src_sg, int size,
unsigned char *iv)
{
struct blkcipher_desc desc = {
.tfm = crypt_stat->tfm,
.info = iv,
.flags = CRYPTO_TFM_REQ_MAY_SLEEP
};
int rc = 0;
/* Consider doing this once, when the file is opened */
mutex_lock(&crypt_stat->cs_tfm_mutex);
rc = crypto_blkcipher_setkey(crypt_stat->tfm, crypt_stat->key,
crypt_stat->key_size);
if (rc) {
ecryptfs_printk(KERN_ERR, "Error setting key; rc = [%d]\n",
rc);
mutex_unlock(&crypt_stat->cs_tfm_mutex);
rc = -EINVAL;
goto out;
}
ecryptfs_printk(KERN_DEBUG, "Decrypting [%d] bytes.\n", size);
rc = crypto_blkcipher_decrypt_iv(&desc, dest_sg, src_sg, size);
mutex_unlock(&crypt_stat->cs_tfm_mutex);
if (rc) {
ecryptfs_printk(KERN_ERR, "Error decrypting; rc = [%d]\n",
rc);
goto out;
}
rc = size;
out:
return rc;
}
/**
* ecryptfs_encrypt_page_offset
*
* Returns the number of bytes encrypted
*/
static int
ecryptfs_encrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
struct page *dst_page, int dst_offset,
struct page *src_page, int src_offset, int size,
unsigned char *iv)
{
struct scatterlist src_sg, dst_sg;
src_sg.page = src_page;
src_sg.offset = src_offset;
src_sg.length = size;
dst_sg.page = dst_page;
dst_sg.offset = dst_offset;
dst_sg.length = size;
return encrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
}
/**
* ecryptfs_decrypt_page_offset
*
* Returns the number of bytes decrypted
*/
static int
ecryptfs_decrypt_page_offset(struct ecryptfs_crypt_stat *crypt_stat,
struct page *dst_page, int dst_offset,
struct page *src_page, int src_offset, int size,
unsigned char *iv)
{
struct scatterlist src_sg, dst_sg;
src_sg.page = src_page;
src_sg.offset = src_offset;
src_sg.length = size;
dst_sg.page = dst_page;
dst_sg.offset = dst_offset;
dst_sg.length = size;
return decrypt_scatterlist(crypt_stat, &dst_sg, &src_sg, size, iv);
}
#define ECRYPTFS_MAX_SCATTERLIST_LEN 4
/**
* ecryptfs_init_crypt_ctx
* @crypt_stat: Uninitilized crypt stats structure
*
* Initialize the crypto context.
*
* TODO: Performance: Keep a cache of initialized cipher contexts;
* only init if needed
*/
int ecryptfs_init_crypt_ctx(struct ecryptfs_crypt_stat *crypt_stat)
{
char *full_alg_name;
int rc = -EINVAL;
if (!crypt_stat->cipher) {
ecryptfs_printk(KERN_ERR, "No cipher specified\n");
goto out;
}
ecryptfs_printk(KERN_DEBUG,
"Initializing cipher [%s]; strlen = [%d]; "
"key_size_bits = [%d]\n",
crypt_stat->cipher, (int)strlen(crypt_stat->cipher),
crypt_stat->key_size << 3);
if (crypt_stat->tfm) {
rc = 0;
goto out;
}
mutex_lock(&crypt_stat->cs_tfm_mutex);
rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
crypt_stat->cipher, "cbc");
if (rc)
goto out;
crypt_stat->tfm = crypto_alloc_blkcipher(full_alg_name, 0,
CRYPTO_ALG_ASYNC);
kfree(full_alg_name);
if (IS_ERR(crypt_stat->tfm)) {
rc = PTR_ERR(crypt_stat->tfm);
ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): "
"Error initializing cipher [%s]\n",
crypt_stat->cipher);
mutex_unlock(&crypt_stat->cs_tfm_mutex);
goto out;
}
crypto_blkcipher_set_flags(crypt_stat->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
mutex_unlock(&crypt_stat->cs_tfm_mutex);
rc = 0;
out:
return rc;
}
static void set_extent_mask_and_shift(struct ecryptfs_crypt_stat *crypt_stat)
{
int extent_size_tmp;
crypt_stat->extent_mask = 0xFFFFFFFF;
crypt_stat->extent_shift = 0;
if (crypt_stat->extent_size == 0)
return;
extent_size_tmp = crypt_stat->extent_size;
while ((extent_size_tmp & 0x01) == 0) {
extent_size_tmp >>= 1;
crypt_stat->extent_mask <<= 1;
crypt_stat->extent_shift++;
}
}
void ecryptfs_set_default_sizes(struct ecryptfs_crypt_stat *crypt_stat)
{
/* Default values; may be overwritten as we are parsing the
* packets. */
crypt_stat->extent_size = ECRYPTFS_DEFAULT_EXTENT_SIZE;
set_extent_mask_and_shift(crypt_stat);
crypt_stat->iv_bytes = ECRYPTFS_DEFAULT_IV_BYTES;
if (PAGE_CACHE_SIZE <= ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE) {
crypt_stat->header_extent_size =
ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
} else
crypt_stat->header_extent_size = PAGE_CACHE_SIZE;
crypt_stat->num_header_extents_at_front = 1;
}
/**
* ecryptfs_compute_root_iv
* @crypt_stats
*
* On error, sets the root IV to all 0's.
*/
int ecryptfs_compute_root_iv(struct ecryptfs_crypt_stat *crypt_stat)
{
int rc = 0;
char dst[MD5_DIGEST_SIZE];
BUG_ON(crypt_stat->iv_bytes > MD5_DIGEST_SIZE);
BUG_ON(crypt_stat->iv_bytes <= 0);
if (!ECRYPTFS_CHECK_FLAG(crypt_stat->flags, ECRYPTFS_KEY_VALID)) {
rc = -EINVAL;
ecryptfs_printk(KERN_WARNING, "Session key not valid; "
"cannot generate root IV\n");
goto out;
}
rc = ecryptfs_calculate_md5(dst, crypt_stat, crypt_stat->key,
crypt_stat->key_size);
if (rc) {
ecryptfs_printk(KERN_WARNING, "Error attempting to compute "
"MD5 while generating root IV\n");
goto out;
}
memcpy(crypt_stat->root_iv, dst, crypt_stat->iv_bytes);
out:
if (rc) {
memset(crypt_stat->root_iv, 0, crypt_stat->iv_bytes);
ECRYPTFS_SET_FLAG(crypt_stat->flags,
ECRYPTFS_SECURITY_WARNING);
}
return rc;
}
static void ecryptfs_generate_new_key(struct ecryptfs_crypt_stat *crypt_stat)
{
get_random_bytes(crypt_stat->key, crypt_stat->key_size);
ECRYPTFS_SET_FLAG(crypt_stat->flags, ECRYPTFS_KEY_VALID);
ecryptfs_compute_root_iv(crypt_stat);
if (unlikely(ecryptfs_verbosity > 0)) {
ecryptfs_printk(KERN_DEBUG, "Generated new session key:\n");
ecryptfs_dump_hex(crypt_stat->key,
crypt_stat->key_size);
}
}
/**
* ecryptfs_set_default_crypt_stat_vals
* @crypt_stat
*
* Default values in the event that policy does not override them.
*/
static void ecryptfs_set_default_crypt_stat_vals(
struct ecryptfs_crypt_stat *crypt_stat,
struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
ecryptfs_set_default_sizes(crypt_stat);
strcpy(crypt_stat->cipher, ECRYPTFS_DEFAULT_CIPHER);
crypt_stat->key_size = ECRYPTFS_DEFAULT_KEY_BYTES;
ECRYPTFS_CLEAR_FLAG(crypt_stat->flags, ECRYPTFS_KEY_VALID);
crypt_stat->file_version = ECRYPTFS_FILE_VERSION;
crypt_stat->mount_crypt_stat = mount_crypt_stat;
}
/**
* ecryptfs_new_file_context
* @ecryptfs_dentry
*
* If the crypto context for the file has not yet been established,
* this is where we do that. Establishing a new crypto context
* involves the following decisions:
* - What cipher to use?
* - What set of authentication tokens to use?
* Here we just worry about getting enough information into the
* authentication tokens so that we know that they are available.
* We associate the available authentication tokens with the new file
* via the set of signatures in the crypt_stat struct. Later, when
* the headers are actually written out, we may again defer to
* userspace to perform the encryption of the session key; for the
* foreseeable future, this will be the case with public key packets.
*
* Returns zero on success; non-zero otherwise
*/
/* Associate an authentication token(s) with the file */
int ecryptfs_new_file_context(struct dentry *ecryptfs_dentry)
{
int rc = 0;
struct ecryptfs_crypt_stat *crypt_stat =
&ecryptfs_inode_to_private(ecryptfs_dentry->d_inode)->crypt_stat;
struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
&ecryptfs_superblock_to_private(
ecryptfs_dentry->d_sb)->mount_crypt_stat;
int cipher_name_len;
ecryptfs_set_default_crypt_stat_vals(crypt_stat, mount_crypt_stat);
/* See if there are mount crypt options */
if (mount_crypt_stat->global_auth_tok) {
ecryptfs_printk(KERN_DEBUG, "Initializing context for new "
"file using mount_crypt_stat\n");
ECRYPTFS_SET_FLAG(crypt_stat->flags, ECRYPTFS_ENCRYPTED);
ECRYPTFS_SET_FLAG(crypt_stat->flags, ECRYPTFS_KEY_VALID);
memcpy(crypt_stat->keysigs[crypt_stat->num_keysigs++],
mount_crypt_stat->global_auth_tok_sig,
ECRYPTFS_SIG_SIZE_HEX);
cipher_name_len =
strlen(mount_crypt_stat->global_default_cipher_name);
memcpy(crypt_stat->cipher,
mount_crypt_stat->global_default_cipher_name,
cipher_name_len);
crypt_stat->cipher[cipher_name_len] = '\0';
crypt_stat->key_size =
mount_crypt_stat->global_default_cipher_key_size;
ecryptfs_generate_new_key(crypt_stat);
} else
/* We should not encounter this scenario since we
* should detect lack of global_auth_tok at mount time
* TODO: Applies to 0.1 release only; remove in future
* release */
BUG();
rc = ecryptfs_init_crypt_ctx(crypt_stat);
if (rc)
ecryptfs_printk(KERN_ERR, "Error initializing cryptographic "
"context for cipher [%s]: rc = [%d]\n",
crypt_stat->cipher, rc);
return rc;
}
/**
* contains_ecryptfs_marker - check for the ecryptfs marker
* @data: The data block in which to check