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OpenCloudOS-Kernel/fs/ecryptfs/crypto.c

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// SPDX-License-Identifier: GPL-2.0-or-later
/**
* eCryptfs: Linux filesystem encryption layer
*
* Copyright (C) 1997-2004 Erez Zadok
* Copyright (C) 2001-2004 Stony Brook University
* Copyright (C) 2004-2007 International Business Machines Corp.
* Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
* Michael C. Thompson <mcthomps@us.ibm.com>
*/
#include <crypto/hash.h>
#include <crypto/skcipher.h>
#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/file.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>
#include <asm/unaligned.h>
#include <linux/kernel.h>
#include <linux/xattr.h>
#include "ecryptfs_kernel.h"
#define DECRYPT 0
#define ENCRYPT 1
/**
* 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 representation 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)
{
int rc = crypto_shash_tfm_digest(crypt_stat->hash_tfm, src, len, dst);
if (rc) {
printk(KERN_ERR
"%s: Error computing crypto hash; rc = [%d]\n",
__func__, rc);
goto out;
}
out:
return rc;
}
static 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 extent whose 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.
*/
int ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
loff_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, "%lld", 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.
*/
int ecryptfs_init_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
{
struct crypto_shash *tfm;
int rc;
tfm = crypto_alloc_shash(ECRYPTFS_DEFAULT_HASH, 0, 0);
if (IS_ERR(tfm)) {
rc = PTR_ERR(tfm);
ecryptfs_printk(KERN_ERR, "Error attempting to "
"allocate crypto context; rc = [%d]\n",
rc);
return rc;
}
memset((void *)crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
INIT_LIST_HEAD(&crypt_stat->keysig_list);
mutex_init(&crypt_stat->keysig_list_mutex);
mutex_init(&crypt_stat->cs_mutex);
mutex_init(&crypt_stat->cs_tfm_mutex);
crypt_stat->hash_tfm = tfm;
crypt_stat->flags |= ECRYPTFS_STRUCT_INITIALIZED;
return 0;
}
/**
* ecryptfs_destroy_crypt_stat
* @crypt_stat: Pointer to the crypt_stat struct to initialize.
*
* Releases all memory associated with a crypt_stat struct.
*/
void ecryptfs_destroy_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
{
struct ecryptfs_key_sig *key_sig, *key_sig_tmp;
crypto_free_skcipher(crypt_stat->tfm);
crypto_free_shash(crypt_stat->hash_tfm);
list_for_each_entry_safe(key_sig, key_sig_tmp,
&crypt_stat->keysig_list, crypt_stat_list) {
list_del(&key_sig->crypt_stat_list);
kmem_cache_free(ecryptfs_key_sig_cache, key_sig);
}
memset(crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
}
void ecryptfs_destroy_mount_crypt_stat(
struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
struct ecryptfs_global_auth_tok *auth_tok, *auth_tok_tmp;
if (!(mount_crypt_stat->flags & ECRYPTFS_MOUNT_CRYPT_STAT_INITIALIZED))
return;
mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
list_for_each_entry_safe(auth_tok, auth_tok_tmp,
&mount_crypt_stat->global_auth_tok_list,
mount_crypt_stat_list) {
list_del(&auth_tok->mount_crypt_stat_list);
if (!(auth_tok->flags & ECRYPTFS_AUTH_TOK_INVALID))
key_put(auth_tok->global_auth_tok_key);
kmem_cache_free(ecryptfs_global_auth_tok_cache, auth_tok);
}
mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
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;
sg_init_table(sg, sg_size);
while (size > 0 && i < sg_size) {
pg = virt_to_page(addr);
offset = offset_in_page(addr);
sg_set_page(&sg[i], pg, 0, offset);
remainder_of_page = PAGE_SIZE - offset;
if (size >= remainder_of_page) {
sg[i].length = remainder_of_page;
addr += remainder_of_page;
size -= remainder_of_page;
} else {
sg[i].length = size;
addr += size;
size = 0;
}
i++;
}
if (size > 0)
return -ENOMEM;
return i;
}
struct extent_crypt_result {
struct completion completion;
int rc;
};
static void extent_crypt_complete(struct crypto_async_request *req, int rc)
{
struct extent_crypt_result *ecr = req->data;
if (rc == -EINPROGRESS)
return;
ecr->rc = rc;
complete(&ecr->completion);
}
/**
* crypt_scatterlist
* @crypt_stat: Pointer to the crypt_stat struct to initialize.
* @dst_sg: Destination of the data after performing the crypto operation
* @src_sg: Data to be encrypted or decrypted
* @size: Length of data
* @iv: IV to use
* @op: ENCRYPT or DECRYPT to indicate the desired operation
*
* Returns the number of bytes encrypted or decrypted; negative value on error
*/
static int crypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
struct scatterlist *dst_sg,
struct scatterlist *src_sg, int size,
unsigned char *iv, int op)
{
struct skcipher_request *req = NULL;
struct extent_crypt_result ecr;
int rc = 0;
if (!crypt_stat || !crypt_stat->tfm
|| !(crypt_stat->flags & ECRYPTFS_STRUCT_INITIALIZED))
return -EINVAL;
if (unlikely(ecryptfs_verbosity > 0)) {
ecryptfs_printk(KERN_DEBUG, "Key size [%zd]; key:\n",
crypt_stat->key_size);
ecryptfs_dump_hex(crypt_stat->key,
crypt_stat->key_size);
}
init_completion(&ecr.completion);
mutex_lock(&crypt_stat->cs_tfm_mutex);
req = skcipher_request_alloc(crypt_stat->tfm, GFP_NOFS);
if (!req) {
mutex_unlock(&crypt_stat->cs_tfm_mutex);
rc = -ENOMEM;
goto out;
}
skcipher_request_set_callback(req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
extent_crypt_complete, &ecr);
/* Consider doing this once, when the file is opened */
if (!(crypt_stat->flags & ECRYPTFS_KEY_SET)) {
rc = crypto_skcipher_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;
}
crypt_stat->flags |= ECRYPTFS_KEY_SET;
}
mutex_unlock(&crypt_stat->cs_tfm_mutex);
skcipher_request_set_crypt(req, src_sg, dst_sg, size, iv);
rc = op == ENCRYPT ? crypto_skcipher_encrypt(req) :
crypto_skcipher_decrypt(req);
if (rc == -EINPROGRESS || rc == -EBUSY) {
struct extent_crypt_result *ecr = req->base.data;
wait_for_completion(&ecr->completion);
rc = ecr->rc;
reinit_completion(&ecr->completion);
}
out:
skcipher_request_free(req);
return rc;
}
/**
* lower_offset_for_page
*
* Convert an eCryptfs page index into a lower byte offset
*/
static loff_t lower_offset_for_page(struct ecryptfs_crypt_stat *crypt_stat,
struct page *page)
{
return ecryptfs_lower_header_size(crypt_stat) +
((loff_t)page->index << PAGE_SHIFT);
}
/**
* crypt_extent
* @crypt_stat: crypt_stat containing cryptographic context for the
* encryption operation
* @dst_page: The page to write the result into
* @src_page: The page to read from
* @extent_offset: Page extent offset for use in generating IV
* @op: ENCRYPT or DECRYPT to indicate the desired operation
*
* Encrypts or decrypts one extent of data.
*
* Return zero on success; non-zero otherwise
*/
static int crypt_extent(struct ecryptfs_crypt_stat *crypt_stat,
struct page *dst_page,
struct page *src_page,
unsigned long extent_offset, int op)
{
pgoff_t page_index = op == ENCRYPT ? src_page->index : dst_page->index;
loff_t extent_base;
char extent_iv[ECRYPTFS_MAX_IV_BYTES];
struct scatterlist src_sg, dst_sg;
size_t extent_size = crypt_stat->extent_size;
int rc;
extent_base = (((loff_t)page_index) * (PAGE_SIZE / extent_size));
rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
(extent_base + extent_offset));
if (rc) {
ecryptfs_printk(KERN_ERR, "Error attempting to derive IV for "
"extent [0x%.16llx]; rc = [%d]\n",
(unsigned long long)(extent_base + extent_offset), rc);
goto out;
}
sg_init_table(&src_sg, 1);
sg_init_table(&dst_sg, 1);
sg_set_page(&src_sg, src_page, extent_size,
extent_offset * extent_size);
sg_set_page(&dst_sg, dst_page, extent_size,
extent_offset * extent_size);
rc = crypt_scatterlist(crypt_stat, &dst_sg, &src_sg, extent_size,
extent_iv, op);
if (rc < 0) {
printk(KERN_ERR "%s: Error attempting to crypt page with "
"page_index = [%ld], extent_offset = [%ld]; "
"rc = [%d]\n", __func__, page_index, extent_offset, rc);
goto out;
}
rc = 0;
out:
return rc;
}
/**
* ecryptfs_encrypt_page
* @page: Page mapped from the eCryptfs inode for the file; contains
* decrypted content that needs to be encrypted (to a temporary
* page; not in place) and written out to the lower file
*
* 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.
*
* Returns zero on success; negative on error
*/
int ecryptfs_encrypt_page(struct page *page)
{
struct inode *ecryptfs_inode;
struct ecryptfs_crypt_stat *crypt_stat;
char *enc_extent_virt;
struct page *enc_extent_page = NULL;
loff_t extent_offset;
loff_t lower_offset;
int rc = 0;
ecryptfs_inode = page->mapping->host;
crypt_stat =
&(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);
BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
enc_extent_page = alloc_page(GFP_USER);
if (!enc_extent_page) {
rc = -ENOMEM;
ecryptfs_printk(KERN_ERR, "Error allocating memory for "
"encrypted extent\n");
goto out;
}
for (extent_offset = 0;
extent_offset < (PAGE_SIZE / crypt_stat->extent_size);
extent_offset++) {
rc = crypt_extent(crypt_stat, enc_extent_page, page,
extent_offset, ENCRYPT);
if (rc) {
printk(KERN_ERR "%s: Error encrypting extent; "
"rc = [%d]\n", __func__, rc);
goto out;
}
}
lower_offset = lower_offset_for_page(crypt_stat, page);
enc_extent_virt = kmap(enc_extent_page);
rc = ecryptfs_write_lower(ecryptfs_inode, enc_extent_virt, lower_offset,
PAGE_SIZE);
kunmap(enc_extent_page);
if (rc < 0) {
ecryptfs_printk(KERN_ERR,
"Error attempting to write lower page; rc = [%d]\n",
rc);
goto out;
}
rc = 0;
out:
if (enc_extent_page) {
__free_page(enc_extent_page);
}
return rc;
}
/**
* ecryptfs_decrypt_page
* @page: Page mapped from the eCryptfs inode for the file; data read
* and decrypted from the lower file will be written into this
* page
*
* 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 page *page)
{
struct inode *ecryptfs_inode;
struct ecryptfs_crypt_stat *crypt_stat;
char *page_virt;
unsigned long extent_offset;
loff_t lower_offset;
int rc = 0;
ecryptfs_inode = page->mapping->host;
crypt_stat =
&(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);
BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
lower_offset = lower_offset_for_page(crypt_stat, page);
page_virt = kmap(page);
rc = ecryptfs_read_lower(page_virt, lower_offset, PAGE_SIZE,
ecryptfs_inode);
kunmap(page);
if (rc < 0) {
ecryptfs_printk(KERN_ERR,
"Error attempting to read lower page; rc = [%d]\n",
rc);
goto out;
}
for (extent_offset = 0;
extent_offset < (PAGE_SIZE / crypt_stat->extent_size);
extent_offset++) {
rc = crypt_extent(crypt_stat, page, page,
extent_offset, DECRYPT);
if (rc) {
printk(KERN_ERR "%s: Error encrypting extent; "
"rc = [%d]\n", __func__, rc);
goto out;
}
}
out:
return rc;
}
#define ECRYPTFS_MAX_SCATTERLIST_LEN 4
/**
* ecryptfs_init_crypt_ctx
* @crypt_stat: Uninitialized 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;
ecryptfs_printk(KERN_DEBUG,
"Initializing cipher [%s]; strlen = [%d]; "
"key_size_bits = [%zd]\n",
crypt_stat->cipher, (int)strlen(crypt_stat->cipher),
crypt_stat->key_size << 3);
mutex_lock(&crypt_stat->cs_tfm_mutex);
if (crypt_stat->tfm) {
rc = 0;
goto out_unlock;
}
rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
crypt_stat->cipher, "cbc");
if (rc)
goto out_unlock;
crypt_stat->tfm = crypto_alloc_skcipher(full_alg_name, 0, 0);
if (IS_ERR(crypt_stat->tfm)) {
rc = PTR_ERR(crypt_stat->tfm);
crypt_stat->tfm = NULL;
ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): "
"Error initializing cipher [%s]\n",
full_alg_name);
goto out_free;
}
crypto_skcipher_set_flags(crypt_stat->tfm,
CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
rc = 0;
out_free:
kfree(full_alg_name);
out_unlock:
mutex_unlock(&crypt_stat->cs_tfm_mutex);
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 (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
crypt_stat->metadata_size = ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
else {
if (PAGE_SIZE <= ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE)
crypt_stat->metadata_size =
ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
else
crypt_stat->metadata_size = PAGE_SIZE;
}
}
/**
* 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 (!(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);
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);
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_copy_mount_wide_flags_to_inode_flags
* @crypt_stat: The inode's cryptographic context
* @mount_crypt_stat: The mount point's cryptographic context
*
* This function propagates the mount-wide flags to individual inode
* flags.
*/
static void ecryptfs_copy_mount_wide_flags_to_inode_flags(
struct ecryptfs_crypt_stat *crypt_stat,
struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
if (mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED)
crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
crypt_stat->flags |= ECRYPTFS_VIEW_AS_ENCRYPTED;
if (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES) {
crypt_stat->flags |= ECRYPTFS_ENCRYPT_FILENAMES;
if (mount_crypt_stat->flags
& ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK)
crypt_stat->flags |= ECRYPTFS_ENCFN_USE_MOUNT_FNEK;
else if (mount_crypt_stat->flags
& ECRYPTFS_GLOBAL_ENCFN_USE_FEK)
crypt_stat->flags |= ECRYPTFS_ENCFN_USE_FEK;
}
}
static int ecryptfs_copy_mount_wide_sigs_to_inode_sigs(
struct ecryptfs_crypt_stat *crypt_stat,
struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
struct ecryptfs_global_auth_tok *global_auth_tok;
int rc = 0;
mutex_lock(&crypt_stat->keysig_list_mutex);
mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
list_for_each_entry(global_auth_tok,
&mount_crypt_stat->global_auth_tok_list,
mount_crypt_stat_list) {
if (global_auth_tok->flags & ECRYPTFS_AUTH_TOK_FNEK)
continue;
rc = ecryptfs_add_keysig(crypt_stat, global_auth_tok->sig);
if (rc) {
printk(KERN_ERR "Error adding keysig; rc = [%d]\n", rc);
goto out;
}
}
out:
mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
mutex_unlock(&crypt_stat->keysig_list_mutex);
return rc;
}
/**
* ecryptfs_set_default_crypt_stat_vals
* @crypt_stat: The inode's cryptographic context
* @mount_crypt_stat: The mount point's cryptographic context
*
* 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_copy_mount_wide_flags_to_inode_flags(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;
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_inode: The eCryptfs inode
*
* 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
*/
int ecryptfs_new_file_context(struct inode *ecryptfs_inode)
{
struct ecryptfs_crypt_stat *crypt_stat =
&ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
&ecryptfs_superblock_to_private(
ecryptfs_inode->i_sb)->mount_crypt_stat;
int cipher_name_len;
int rc = 0;
ecryptfs_set_default_crypt_stat_vals(crypt_stat, mount_crypt_stat);
crypt_stat->flags |= (ECRYPTFS_ENCRYPTED | ECRYPTFS_KEY_VALID);
ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
mount_crypt_stat);
rc = ecryptfs_copy_mount_wide_sigs_to_inode_sigs(crypt_stat,
mount_crypt_stat);
if (rc) {
printk(KERN_ERR "Error attempting to copy mount-wide key sigs "
"to the inode key sigs; rc = [%d]\n", rc);
goto out;
}
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);
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);
out:
return rc;
}
/**
* ecryptfs_validate_marker - check for the ecryptfs marker
* @data: The data block in which to check
*
* Returns zero if marker found; -EINVAL if not found
*/
static int ecryptfs_validate_marker(char *data)
{
u32 m_1, m_2;
m_1 = get_unaligned_be32(data);
m_2 = get_unaligned_be32(data + 4);
if ((m_1 ^ MAGIC_ECRYPTFS_MARKER) == m_2)
return 0;
ecryptfs_printk(KERN_DEBUG, "m_1 = [0x%.8x]; m_2 = [0x%.8x]; "
"MAGIC_ECRYPTFS_MARKER = [0x%.8x]\n", m_1, m_2,
MAGIC_ECRYPTFS_MARKER);
ecryptfs_printk(KERN_DEBUG, "(m_1 ^ MAGIC_ECRYPTFS_MARKER) = "
"[0x%.8x]\n", (m_1 ^ MAGIC_ECRYPTFS_MARKER));
return -EINVAL;
}
struct ecryptfs_flag_map_elem {
u32 file_flag;
u32 local_flag;
};
/* Add support for additional flags by adding elements here. */
static struct ecryptfs_flag_map_elem ecryptfs_flag_map[] = {
{0x00000001, ECRYPTFS_ENABLE_HMAC},
{0x00000002, ECRYPTFS_ENCRYPTED},
{0x00000004, ECRYPTFS_METADATA_IN_XATTR},
{0x00000008, ECRYPTFS_ENCRYPT_FILENAMES}
};
/**
* ecryptfs_process_flags
* @crypt_stat: The cryptographic context
* @page_virt: Source data to be parsed
* @bytes_read: Updated with the number of bytes read
*/
static void ecryptfs_process_flags(struct ecryptfs_crypt_stat *crypt_stat,
char *page_virt, int *bytes_read)
{
int i;
u32 flags;
flags = get_unaligned_be32(page_virt);
for (i = 0; i < ARRAY_SIZE(ecryptfs_flag_map); i++)
if (flags & ecryptfs_flag_map[i].file_flag) {
crypt_stat->flags |= ecryptfs_flag_map[i].local_flag;
} else
crypt_stat->flags &= ~(ecryptfs_flag_map[i].local_flag);
/* Version is in top 8 bits of the 32-bit flag vector */
crypt_stat->file_version = ((flags >> 24) & 0xFF);
(*bytes_read) = 4;
}
/**
* write_ecryptfs_marker
* @page_virt: The pointer to in a page to begin writing the marker
* @written: Number of bytes written
*
* Marker = 0x3c81b7f5
*/
static void write_ecryptfs_marker(char *page_virt, size_t *written)
{
u32 m_1, m_2;
get_random_bytes(&m_1, (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
m_2 = (m_1 ^ MAGIC_ECRYPTFS_MARKER);
put_unaligned_be32(m_1, page_virt);
page_virt += (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2);
put_unaligned_be32(m_2, page_virt);
(*written) = MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
}
void ecryptfs_write_crypt_stat_flags(char *page_virt,
struct ecryptfs_crypt_stat *crypt_stat,
size_t *written)
{
u32 flags = 0;
int i;
for (i = 0; i < ARRAY_SIZE(ecryptfs_flag_map); i++)
if (crypt_stat->flags & ecryptfs_flag_map[i].local_flag)
flags |= ecryptfs_flag_map[i].file_flag;
/* Version is in top 8 bits of the 32-bit flag vector */
flags |= ((((u8)crypt_stat->file_version) << 24) & 0xFF000000);
put_unaligned_be32(flags, page_virt);
(*written) = 4;
}
struct ecryptfs_cipher_code_str_map_elem {
char cipher_str[16];
u8 cipher_code;
};
/* Add support for additional ciphers by adding elements here. The
* cipher_code is whatever OpenPGP applications use to identify the
* ciphers. List in order of probability. */
static struct ecryptfs_cipher_code_str_map_elem
ecryptfs_cipher_code_str_map[] = {
{"aes",RFC2440_CIPHER_AES_128 },
{"blowfish", RFC2440_CIPHER_BLOWFISH},
{"des3_ede", RFC2440_CIPHER_DES3_EDE},
{"cast5", RFC2440_CIPHER_CAST_5},
{"twofish", RFC2440_CIPHER_TWOFISH},
{"cast6", RFC2440_CIPHER_CAST_6},
{"aes", RFC2440_CIPHER_AES_192},
{"aes", RFC2440_CIPHER_AES_256}
};
/**
* ecryptfs_code_for_cipher_string
* @cipher_name: The string alias for the cipher
* @key_bytes: Length of key in bytes; used for AES code selection
*
* Returns zero on no match, or the cipher code on match
*/
u8 ecryptfs_code_for_cipher_string(char *cipher_name, size_t key_bytes)
{
int i;
u8 code = 0;
struct ecryptfs_cipher_code_str_map_elem *map =
ecryptfs_cipher_code_str_map;
if (strcmp(cipher_name, "aes") == 0) {
switch (key_bytes) {
case 16:
code = RFC2440_CIPHER_AES_128;
break;
case 24:
code = RFC2440_CIPHER_AES_192;
break;
case 32:
code = RFC2440_CIPHER_AES_256;
}
} else {
for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
if (strcmp(cipher_name, map[i].cipher_str) == 0) {
code = map[i].cipher_code;
break;
}
}
return code;
}
/**
* ecryptfs_cipher_code_to_string
* @str: Destination to write out the cipher name
* @cipher_code: The code to convert to cipher name string
*
* Returns zero on success
*/
int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code)
{
int rc = 0;
int i;
str[0] = '\0';
for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
if (cipher_code == ecryptfs_cipher_code_str_map[i].cipher_code)
strcpy(str, ecryptfs_cipher_code_str_map[i].cipher_str);
if (str[0] == '\0') {
ecryptfs_printk(KERN_WARNING, "Cipher code not recognized: "
"[%d]\n", cipher_code);
rc = -EINVAL;
}
return rc;
}
int ecryptfs_read_and_validate_header_region(struct inode *inode)
{
u8 file_size[ECRYPTFS_SIZE_AND_MARKER_BYTES];
u8 *marker = file_size + ECRYPTFS_FILE_SIZE_BYTES;
int rc;
rc = ecryptfs_read_lower(file_size, 0, ECRYPTFS_SIZE_AND_MARKER_BYTES,
inode);
if (rc < 0)
return rc;
else if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
return -EINVAL;
rc = ecryptfs_validate_marker(marker);
if (!rc)
ecryptfs_i_size_init(file_size, inode);
return rc;
}
void
ecryptfs_write_header_metadata(char *virt,
struct ecryptfs_crypt_stat *crypt_stat,
size_t *written)
{
u32 header_extent_size;
u16 num_header_extents_at_front;
header_extent_size = (u32)crypt_stat->extent_size;
num_header_extents_at_front =
(u16)(crypt_stat->metadata_size / crypt_stat->extent_size);
put_unaligned_be32(header_extent_size, virt);
virt += 4;
put_unaligned_be16(num_header_extents_at_front, virt);
(*written) = 6;
}
struct kmem_cache *ecryptfs_header_cache;
/**
* ecryptfs_write_headers_virt
* @page_virt: The virtual address to write the headers to
* @max: The size of memory allocated at page_virt
* @size: Set to the number of bytes written by this function
* @crypt_stat: The cryptographic context
* @ecryptfs_dentry: The eCryptfs dentry
*
* Format version: 1
*
* Header Extent:
* Octets 0-7: Unencrypted file size (big-endian)
* Octets 8-15: eCryptfs special marker
* Octets 16-19: Flags
* Octet 16: File format version number (between 0 and 255)
* Octets 17-18: Reserved
* Octet 19: Bit 1 (lsb): Reserved
* Bit 2: Encrypted?
* Bits 3-8: Reserved
* Octets 20-23: Header extent size (big-endian)
* Octets 24-25: Number of header extents at front of file
* (big-endian)
* Octet 26: Begin RFC 2440 authentication token packet set
* Data Extent 0:
* Lower data (CBC encrypted)
* Data Extent 1:
* Lower data (CBC encrypted)
* ...
*
* Returns zero on success
*/
static int ecryptfs_write_headers_virt(char *page_virt, size_t max,
size_t *size,
struct ecryptfs_crypt_stat *crypt_stat,
struct dentry *ecryptfs_dentry)
{
int rc;
size_t written;
size_t offset;
offset = ECRYPTFS_FILE_SIZE_BYTES;
write_ecryptfs_marker((page_virt + offset), &written);
offset += written;
ecryptfs_write_crypt_stat_flags((page_virt + offset), crypt_stat,
&written);
offset += written;
ecryptfs_write_header_metadata((page_virt + offset), crypt_stat,
&written);
offset += written;
rc = ecryptfs_generate_key_packet_set((page_virt + offset), crypt_stat,
ecryptfs_dentry, &written,
max - offset);
if (rc)
ecryptfs_printk(KERN_WARNING, "Error generating key packet "
"set; rc = [%d]\n", rc);
if (size) {
offset += written;
*size = offset;
}
return rc;
}
static int
ecryptfs_write_metadata_to_contents(struct inode *ecryptfs_inode,
char *virt, size_t virt_len)
{
int rc;
rc = ecryptfs_write_lower(ecryptfs_inode, virt,
0, virt_len);
if (rc < 0)
printk(KERN_ERR "%s: Error attempting to write header "
"information to lower file; rc = [%d]\n", __func__, rc);
else
rc = 0;
return rc;
}
static int
ecryptfs_write_metadata_to_xattr(struct dentry *ecryptfs_dentry,
struct inode *ecryptfs_inode,
char *page_virt, size_t size)
{
int rc;
struct dentry *lower_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry);
struct inode *lower_inode = d_inode(lower_dentry);
if (!(lower_inode->i_opflags & IOP_XATTR)) {
rc = -EOPNOTSUPP;
goto out;
}
inode_lock(lower_inode);
rc = __vfs_setxattr(&init_user_ns, lower_dentry, lower_inode,
ECRYPTFS_XATTR_NAME, page_virt, size, 0);
if (!rc && ecryptfs_inode)
fsstack_copy_attr_all(ecryptfs_inode, lower_inode);
inode_unlock(lower_inode);
out:
return rc;
}
static unsigned long ecryptfs_get_zeroed_pages(gfp_t gfp_mask,
unsigned int order)
{
struct page *page;
page = alloc_pages(gfp_mask | __GFP_ZERO, order);
if (page)
return (unsigned long) page_address(page);
return 0;
}
/**
* ecryptfs_write_metadata
* @ecryptfs_dentry: The eCryptfs dentry, which should be negative
* @ecryptfs_inode: The newly created eCryptfs inode
*
* Write the file headers out. This will likely involve a userspace
* callout, in which the session key is encrypted with one or more
* public keys and/or the passphrase necessary to do the encryption is
* retrieved via a prompt. Exactly what happens at this point should
* be policy-dependent.
*
* Returns zero on success; non-zero on error
*/
int ecryptfs_write_metadata(struct dentry *ecryptfs_dentry,
struct inode *ecryptfs_inode)
{
struct ecryptfs_crypt_stat *crypt_stat =
&ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
unsigned int order;
char *virt;
size_t virt_len;
size_t size = 0;
int rc = 0;
if (likely(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
if (!(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
printk(KERN_ERR "Key is invalid; bailing out\n");
rc = -EINVAL;
goto out;
}
} else {
printk(KERN_WARNING "%s: Encrypted flag not set\n",
__func__);
rc = -EINVAL;
goto out;
}
virt_len = crypt_stat->metadata_size;
order = get_order(virt_len);
/* Released in this function */
virt = (char *)ecryptfs_get_zeroed_pages(GFP_KERNEL, order);
if (!virt) {
printk(KERN_ERR "%s: Out of memory\n", __func__);
rc = -ENOMEM;
goto out;
}
/* Zeroed page ensures the in-header unencrypted i_size is set to 0 */
rc = ecryptfs_write_headers_virt(virt, virt_len, &size, crypt_stat,
ecryptfs_dentry);
if (unlikely(rc)) {
printk(KERN_ERR "%s: Error whilst writing headers; rc = [%d]\n",
__func__, rc);
goto out_free;
}
if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
rc = ecryptfs_write_metadata_to_xattr(ecryptfs_dentry, ecryptfs_inode,
virt, size);
else
rc = ecryptfs_write_metadata_to_contents(ecryptfs_inode, virt,
virt_len);
if (rc) {
printk(KERN_ERR "%s: Error writing metadata out to lower file; "
"rc = [%d]\n", __func__, rc);
goto out_free;
}
out_free:
free_pages((unsigned long)virt, order);
out:
return rc;
}
#define ECRYPTFS_DONT_VALIDATE_HEADER_SIZE 0
#define ECRYPTFS_VALIDATE_HEADER_SIZE 1
static int parse_header_metadata(struct ecryptfs_crypt_stat *crypt_stat,
char *virt, int *bytes_read,
int validate_header_size)
{
int rc = 0;
u32 header_extent_size;
u16 num_header_extents_at_front;
header_extent_size = get_unaligned_be32(virt);
virt += sizeof(__be32);
num_header_extents_at_front = get_unaligned_be16(virt);
crypt_stat->metadata_size = (((size_t)num_header_extents_at_front
* (size_t)header_extent_size));
(*bytes_read) = (sizeof(__be32) + sizeof(__be16));
if ((validate_header_size == ECRYPTFS_VALIDATE_HEADER_SIZE)
&& (crypt_stat->metadata_size
< ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE)) {
rc = -EINVAL;
printk(KERN_WARNING "Invalid header size: [%zd]\n",
crypt_stat->metadata_size);
}
return rc;
}
/**
* set_default_header_data
* @crypt_stat: The cryptographic context
*
* For version 0 file format; this function is only for backwards
* compatibility for files created with the prior versions of
* eCryptfs.
*/
static void set_default_header_data(struct ecryptfs_crypt_stat *crypt_stat)
{
crypt_stat->metadata_size = ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
}
void ecryptfs_i_size_init(const char *page_virt, struct inode *inode)
{
struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
struct ecryptfs_crypt_stat *crypt_stat;
u64 file_size;
crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
mount_crypt_stat =
&ecryptfs_superblock_to_private(inode->i_sb)->mount_crypt_stat;
if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED) {
file_size = i_size_read(ecryptfs_inode_to_lower(inode));
if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
file_size += crypt_stat->metadata_size;
} else
file_size = get_unaligned_be64(page_virt);
i_size_write(inode, (loff_t)file_size);
crypt_stat->flags |= ECRYPTFS_I_SIZE_INITIALIZED;
}
/**
* ecryptfs_read_headers_virt
* @page_virt: The virtual address into which to read the headers
* @crypt_stat: The cryptographic context
* @ecryptfs_dentry: The eCryptfs dentry
* @validate_header_size: Whether to validate the header size while reading
*
* Read/parse the header data. The header format is detailed in the
* comment block for the ecryptfs_write_headers_virt() function.
*
* Returns zero on success
*/
static int ecryptfs_read_headers_virt(char *page_virt,
struct ecryptfs_crypt_stat *crypt_stat,
struct dentry *ecryptfs_dentry,
int validate_header_size)
{
int rc = 0;
int offset;
int bytes_read;
ecryptfs_set_default_sizes(crypt_stat);
crypt_stat->mount_crypt_stat = &ecryptfs_superblock_to_private(
ecryptfs_dentry->d_sb)->mount_crypt_stat;
offset = ECRYPTFS_FILE_SIZE_BYTES;
rc = ecryptfs_validate_marker(page_virt + offset);
if (rc)
goto out;
if (!(crypt_stat->flags & ECRYPTFS_I_SIZE_INITIALIZED))
ecryptfs_i_size_init(page_virt, d_inode(ecryptfs_dentry));
offset += MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
ecryptfs_process_flags(crypt_stat, (page_virt + offset), &bytes_read);
if (crypt_stat->file_version > ECRYPTFS_SUPPORTED_FILE_VERSION) {
ecryptfs_printk(KERN_WARNING, "File version is [%d]; only "
"file version [%d] is supported by this "
"version of eCryptfs\n",
crypt_stat->file_version,
ECRYPTFS_SUPPORTED_FILE_VERSION);
rc = -EINVAL;
goto out;
}
offset += bytes_read;
if (crypt_stat->file_version >= 1) {
rc = parse_header_metadata(crypt_stat, (page_virt + offset),
&bytes_read, validate_header_size);
if (rc) {
ecryptfs_printk(KERN_WARNING, "Error reading header "
"metadata; rc = [%d]\n", rc);
}
offset += bytes_read;
} else
set_default_header_data(crypt_stat);
rc = ecryptfs_parse_packet_set(crypt_stat, (page_virt + offset),
ecryptfs_dentry);
out:
return rc;
}
/**
* ecryptfs_read_xattr_region
* @page_virt: The vitual address into which to read the xattr data
* @ecryptfs_inode: The eCryptfs inode
*
* Attempts to read the crypto metadata from the extended attribute
* region of the lower file.
*
* Returns zero on success; non-zero on error
*/
int ecryptfs_read_xattr_region(char *page_virt, struct inode *ecryptfs_inode)
{
struct dentry *lower_dentry =
ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
ssize_t size;
int rc = 0;
size = ecryptfs_getxattr_lower(lower_dentry,
ecryptfs_inode_to_lower(ecryptfs_inode),
ECRYPTFS_XATTR_NAME,
page_virt, ECRYPTFS_DEFAULT_EXTENT_SIZE);
if (size < 0) {
if (unlikely(ecryptfs_verbosity > 0))
printk(KERN_INFO "Error attempting to read the [%s] "
"xattr from the lower file; return value = "
"[%zd]\n", ECRYPTFS_XATTR_NAME, size);
rc = -EINVAL;
goto out;
}
out:
return rc;
}
int ecryptfs_read_and_validate_xattr_region(struct dentry *dentry,
struct inode *inode)
{
u8 file_size[ECRYPTFS_SIZE_AND_MARKER_BYTES];
u8 *marker = file_size + ECRYPTFS_FILE_SIZE_BYTES;
int rc;
rc = ecryptfs_getxattr_lower(ecryptfs_dentry_to_lower(dentry),
ecryptfs_inode_to_lower(inode),
ECRYPTFS_XATTR_NAME, file_size,
ECRYPTFS_SIZE_AND_MARKER_BYTES);
if (rc < 0)
return rc;
else if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
return -EINVAL;
rc = ecryptfs_validate_marker(marker);
if (!rc)
ecryptfs_i_size_init(file_size, inode);
return rc;
}
/**
* ecryptfs_read_metadata
*
* Common entry point for reading file metadata. From here, we could
* retrieve the header information from the header region of the file,
* the xattr region of the file, or some other repository that is
* stored separately from the file itself. The current implementation
* supports retrieving the metadata information from the file contents
* and from the xattr region.
*
* Returns zero if valid headers found and parsed; non-zero otherwise
*/
int ecryptfs_read_metadata(struct dentry *ecryptfs_dentry)
{
int rc;
char *page_virt;
struct inode *ecryptfs_inode = d_inode(ecryptfs_dentry);
struct ecryptfs_crypt_stat *crypt_stat =
&ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
&ecryptfs_superblock_to_private(
ecryptfs_dentry->d_sb)->mount_crypt_stat;
ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
mount_crypt_stat);
/* Read the first page from the underlying file */
page_virt = kmem_cache_alloc(ecryptfs_header_cache, GFP_USER);
if (!page_virt) {
rc = -ENOMEM;
goto out;
}
rc = ecryptfs_read_lower(page_virt, 0, crypt_stat->extent_size,
ecryptfs_inode);
if (rc >= 0)
rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
ecryptfs_dentry,
ECRYPTFS_VALIDATE_HEADER_SIZE);
if (rc) {
/* metadata is not in the file header, so try xattrs */
memset(page_virt, 0, PAGE_SIZE);
rc = ecryptfs_read_xattr_region(page_virt, ecryptfs_inode);
if (rc) {
printk(KERN_DEBUG "Valid eCryptfs headers not found in "
"file header region or xattr region, inode %lu\n",
ecryptfs_inode->i_ino);
rc = -EINVAL;
goto out;
}
rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
ecryptfs_dentry,
ECRYPTFS_DONT_VALIDATE_HEADER_SIZE);
if (rc) {
printk(KERN_DEBUG "Valid eCryptfs headers not found in "
"file xattr region either, inode %lu\n",
ecryptfs_inode->i_ino);
rc = -EINVAL;
}
if (crypt_stat->mount_crypt_stat->flags
& ECRYPTFS_XATTR_METADATA_ENABLED) {
crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
} else {
printk(KERN_WARNING "Attempt to access file with "
"crypto metadata only in the extended attribute "
"region, but eCryptfs was mounted without "
"xattr support enabled. eCryptfs will not treat "
"this like an encrypted file, inode %lu\n",
ecryptfs_inode->i_ino);
rc = -EINVAL;
}
}
out:
if (page_virt) {
memset(page_virt, 0, PAGE_SIZE);
kmem_cache_free(ecryptfs_header_cache, page_virt);
}
return rc;
}
/**
* ecryptfs_encrypt_filename - encrypt filename
*
* CBC-encrypts the filename. We do not want to encrypt the same
* filename with the same key and IV, which may happen with hard
* links, so we prepend random bits to each filename.
*
* Returns zero on success; non-zero otherwise
*/
static int
ecryptfs_encrypt_filename(struct ecryptfs_filename *filename,
struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
int rc = 0;
filename->encrypted_filename = NULL;
filename->encrypted_filename_size = 0;
if (mount_crypt_stat && (mount_crypt_stat->flags
& ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK)) {
size_t packet_size;
size_t remaining_bytes;
rc = ecryptfs_write_tag_70_packet(
NULL, NULL,
&filename->encrypted_filename_size,
mount_crypt_stat, NULL,
filename->filename_size);
if (rc) {
printk(KERN_ERR "%s: Error attempting to get packet "
"size for tag 72; rc = [%d]\n", __func__,
rc);
filename->encrypted_filename_size = 0;
goto out;
}
filename->encrypted_filename =
kmalloc(filename->encrypted_filename_size, GFP_KERNEL);
if (!filename->encrypted_filename) {
rc = -ENOMEM;
goto out;
}
remaining_bytes = filename->encrypted_filename_size;
rc = ecryptfs_write_tag_70_packet(filename->encrypted_filename,
&remaining_bytes,
&packet_size,
mount_crypt_stat,
filename->filename,
filename->filename_size);
if (rc) {
printk(KERN_ERR "%s: Error attempting to generate "
"tag 70 packet; rc = [%d]\n", __func__,
rc);
kfree(filename->encrypted_filename);
filename->encrypted_filename = NULL;
filename->encrypted_filename_size = 0;
goto out;
}
filename->encrypted_filename_size = packet_size;
} else {
printk(KERN_ERR "%s: No support for requested filename "
"encryption method in this release\n", __func__);
rc = -EOPNOTSUPP;
goto out;
}
out:
return rc;
}
static int ecryptfs_copy_filename(char **copied_name, size_t *copied_name_size,
const char *name, size_t name_size)
{
int rc = 0;
(*copied_name) = kmalloc((name_size + 1), GFP_KERNEL);
if (!(*copied_name)) {
rc = -ENOMEM;
goto out;
}
memcpy((void *)(*copied_name), (void *)name, name_size);
(*copied_name)[(name_size)] = '\0'; /* Only for convenience
* in printing out the
* string in debug
* messages */
(*copied_name_size) = name_size;
out:
return rc;
}
/**
* ecryptfs_process_key_cipher - Perform key cipher initialization.
* @key_tfm: Crypto context for key material, set by this function
* @cipher_name: Name of the cipher
* @key_size: Size of the key in bytes
*
* Returns zero on success. Any crypto_tfm structs allocated here
* should be released by other functions, such as on a superblock put
* event, regardless of whether this function succeeds for fails.
*/
static int
ecryptfs_process_key_cipher(struct crypto_skcipher **key_tfm,
char *cipher_name, size_t *key_size)
{
char dummy_key[ECRYPTFS_MAX_KEY_BYTES];
char *full_alg_name = NULL;
int rc;
*key_tfm = NULL;
if (*key_size > ECRYPTFS_MAX_KEY_BYTES) {
rc = -EINVAL;
printk(KERN_ERR "Requested key size is [%zd] bytes; maximum "
"allowable is [%d]\n", *key_size, ECRYPTFS_MAX_KEY_BYTES);
goto out;
}
rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name, cipher_name,
"ecb");
if (rc)
goto out;
*key_tfm = crypto_alloc_skcipher(full_alg_name, 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(*key_tfm)) {
rc = PTR_ERR(*key_tfm);
printk(KERN_ERR "Unable to allocate crypto cipher with name "
"[%s]; rc = [%d]\n", full_alg_name, rc);
goto out;
}
crypto_skcipher_set_flags(*key_tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
if (*key_size == 0)
*key_size = crypto_skcipher_max_keysize(*key_tfm);
get_random_bytes(dummy_key, *key_size);
rc = crypto_skcipher_setkey(*key_tfm, dummy_key, *key_size);
if (rc) {
printk(KERN_ERR "Error attempting to set key of size [%zd] for "
"cipher [%s]; rc = [%d]\n", *key_size, full_alg_name,
rc);
rc = -EINVAL;
goto out;
}
out:
kfree(full_alg_name);
return rc;
}
struct kmem_cache *ecryptfs_key_tfm_cache;
static struct list_head key_tfm_list;
struct mutex key_tfm_list_mutex;
int __init ecryptfs_init_crypto(void)
{
mutex_init(&key_tfm_list_mutex);
INIT_LIST_HEAD(&key_tfm_list);
return 0;
}
/**
* ecryptfs_destroy_crypto - free all cached key_tfms on key_tfm_list
*
* Called only at module unload time
*/
int ecryptfs_destroy_crypto(void)
{
struct ecryptfs_key_tfm *key_tfm, *key_tfm_tmp;
mutex_lock(&key_tfm_list_mutex);
list_for_each_entry_safe(key_tfm, key_tfm_tmp, &key_tfm_list,
key_tfm_list) {
list_del(&key_tfm->key_tfm_list);
crypto_free_skcipher(key_tfm->key_tfm);
kmem_cache_free(ecryptfs_key_tfm_cache, key_tfm);
}
mutex_unlock(&key_tfm_list_mutex);
return 0;
}
int
ecryptfs_add_new_key_tfm(struct ecryptfs_key_tfm **key_tfm, char *cipher_name,
size_t key_size)
{
struct ecryptfs_key_tfm *tmp_tfm;
int rc = 0;
BUG_ON(!mutex_is_locked(&key_tfm_list_mutex));
tmp_tfm = kmem_cache_alloc(ecryptfs_key_tfm_cache, GFP_KERNEL);
if (key_tfm)
(*key_tfm) = tmp_tfm;
if (!tmp_tfm) {
rc = -ENOMEM;
goto out;
}
mutex_init(&tmp_tfm->key_tfm_mutex);
strncpy(tmp_tfm->cipher_name, cipher_name,
ECRYPTFS_MAX_CIPHER_NAME_SIZE);
tmp_tfm->cipher_name[ECRYPTFS_MAX_CIPHER_NAME_SIZE] = '\0';
tmp_tfm->key_size = key_size;
rc = ecryptfs_process_key_cipher(&tmp_tfm->key_tfm,
tmp_tfm->cipher_name,
&tmp_tfm->key_size);
if (rc) {
printk(KERN_ERR "Error attempting to initialize key TFM "
"cipher with name = [%s]; rc = [%d]\n",
tmp_tfm->cipher_name, rc);
kmem_cache_free(ecryptfs_key_tfm_cache, tmp_tfm);
if (key_tfm)
(*key_tfm) = NULL;
goto out;
}
list_add(&tmp_tfm->key_tfm_list, &key_tfm_list);
out:
return rc;
}
/**
* ecryptfs_tfm_exists - Search for existing tfm for cipher_name.
* @cipher_name: the name of the cipher to search for
* @key_tfm: set to corresponding tfm if found
*
* Searches for cached key_tfm matching @cipher_name
* Must be called with &key_tfm_list_mutex held
* Returns 1 if found, with @key_tfm set
* Returns 0 if not found, with @key_tfm set to NULL
*/
int ecryptfs_tfm_exists(char *cipher_name, struct ecryptfs_key_tfm **key_tfm)
{
struct ecryptfs_key_tfm *tmp_key_tfm;
BUG_ON(!mutex_is_locked(&key_tfm_list_mutex));
list_for_each_entry(tmp_key_tfm, &key_tfm_list, key_tfm_list) {
if (strcmp(tmp_key_tfm->cipher_name, cipher_name) == 0) {
if (key_tfm)
(*key_tfm) = tmp_key_tfm;
return 1;
}
}
if (key_tfm)
(*key_tfm) = NULL;
return 0;
}
/**
* ecryptfs_get_tfm_and_mutex_for_cipher_name
*
* @tfm: set to cached tfm found, or new tfm created
* @tfm_mutex: set to mutex for cached tfm found, or new tfm created
* @cipher_name: the name of the cipher to search for and/or add
*
* Sets pointers to @tfm & @tfm_mutex matching @cipher_name.
* Searches for cached item first, and creates new if not found.
* Returns 0 on success, non-zero if adding new cipher failed
*/
int ecryptfs_get_tfm_and_mutex_for_cipher_name(struct crypto_skcipher **tfm,
struct mutex **tfm_mutex,
char *cipher_name)
{
struct ecryptfs_key_tfm *key_tfm;
int rc = 0;
(*tfm) = NULL;
(*tfm_mutex) = NULL;
mutex_lock(&key_tfm_list_mutex);
if (!ecryptfs_tfm_exists(cipher_name, &key_tfm)) {
rc = ecryptfs_add_new_key_tfm(&key_tfm, cipher_name, 0);
if (rc) {
printk(KERN_ERR "Error adding new key_tfm to list; "
"rc = [%d]\n", rc);
goto out;
}
}
(*tfm) = key_tfm->key_tfm;
(*tfm_mutex) = &key_tfm->key_tfm_mutex;
out:
mutex_unlock(&key_tfm_list_mutex);
return rc;
}
/* 64 characters forming a 6-bit target field */
static unsigned char *portable_filename_chars = ("-.0123456789ABCD"
"EFGHIJKLMNOPQRST"
"UVWXYZabcdefghij"
"klmnopqrstuvwxyz");
/* We could either offset on every reverse map or just pad some 0x00's
* at the front here */
static const unsigned char filename_rev_map[256] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 7 */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 15 */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 23 */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 31 */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 39 */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* 47 */
0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, /* 55 */
0x0A, 0x0B, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 63 */
0x00, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, /* 71 */
0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, /* 79 */
0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, /* 87 */
0x23, 0x24, 0x25, 0x00, 0x00, 0x00, 0x00, 0x00, /* 95 */
0x00, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, /* 103 */
0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, /* 111 */
0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, /* 119 */
0x3D, 0x3E, 0x3F /* 123 - 255 initialized to 0x00 */
};
/**
* ecryptfs_encode_for_filename
* @dst: Destination location for encoded filename
* @dst_size: Size of the encoded filename in bytes
* @src: Source location for the filename to encode
* @src_size: Size of the source in bytes
*/
static void ecryptfs_encode_for_filename(unsigned char *dst, size_t *dst_size,
unsigned char *src, size_t src_size)
{
size_t num_blocks;
size_t block_num = 0;
size_t dst_offset = 0;
unsigned char last_block[3];
if (src_size == 0) {
(*dst_size) = 0;
goto out;
}
num_blocks = (src_size / 3);
if ((src_size % 3) == 0) {
memcpy(last_block, (&src[src_size - 3]), 3);
} else {
num_blocks++;
last_block[2] = 0x00;
switch (src_size % 3) {
case 1:
last_block[0] = src[src_size - 1];
last_block[1] = 0x00;
break;
case 2:
last_block[0] = src[src_size - 2];
last_block[1] = src[src_size - 1];
}
}
(*dst_size) = (num_blocks * 4);
if (!dst)
goto out;
while (block_num < num_blocks) {
unsigned char *src_block;
unsigned char dst_block[4];
if (block_num == (num_blocks - 1))
src_block = last_block;
else
src_block = &src[block_num * 3];
dst_block[0] = ((src_block[0] >> 2) & 0x3F);
dst_block[1] = (((src_block[0] << 4) & 0x30)
| ((src_block[1] >> 4) & 0x0F));
dst_block[2] = (((src_block[1] << 2) & 0x3C)
| ((src_block[2] >> 6) & 0x03));
dst_block[3] = (src_block[2] & 0x3F);
dst[dst_offset++] = portable_filename_chars[dst_block[0]];
dst[dst_offset++] = portable_filename_chars[dst_block[1]];
dst[dst_offset++] = portable_filename_chars[dst_block[2]];
dst[dst_offset++] = portable_filename_chars[dst_block[3]];
block_num++;
}
out:
return;
}
static size_t ecryptfs_max_decoded_size(size_t encoded_size)
{
/* Not exact; conservatively long. Every block of 4
* encoded characters decodes into a block of 3
* decoded characters. This segment of code provides
* the caller with the maximum amount of allocated
* space that @dst will need to point to in a
* subsequent call. */
return ((encoded_size + 1) * 3) / 4;
}
/**
* ecryptfs_decode_from_filename
* @dst: If NULL, this function only sets @dst_size and returns. If
* non-NULL, this function decodes the encoded octets in @src
* into the memory that @dst points to.
* @dst_size: Set to the size of the decoded string.
* @src: The encoded set of octets to decode.
* @src_size: The size of the encoded set of octets to decode.
*/
static void
ecryptfs_decode_from_filename(unsigned char *dst, size_t *dst_size,
const unsigned char *src, size_t src_size)
{
u8 current_bit_offset = 0;
size_t src_byte_offset = 0;
size_t dst_byte_offset = 0;
if (!dst) {
(*dst_size) = ecryptfs_max_decoded_size(src_size);
goto out;
}
while (src_byte_offset < src_size) {
unsigned char src_byte =
filename_rev_map[(int)src[src_byte_offset]];
switch (current_bit_offset) {
case 0:
dst[dst_byte_offset] = (src_byte << 2);
current_bit_offset = 6;
break;
case 6:
dst[dst_byte_offset++] |= (src_byte >> 4);
dst[dst_byte_offset] = ((src_byte & 0xF)
<< 4);
current_bit_offset = 4;
break;
case 4:
dst[dst_byte_offset++] |= (src_byte >> 2);
dst[dst_byte_offset] = (src_byte << 6);
current_bit_offset = 2;
break;
case 2:
dst[dst_byte_offset++] |= (src_byte);
current_bit_offset = 0;
break;
}
src_byte_offset++;
}
(*dst_size) = dst_byte_offset;
out:
return;
}
/**
* ecryptfs_encrypt_and_encode_filename - converts a plaintext file name to cipher text
* @crypt_stat: The crypt_stat struct associated with the file anem to encode
* @name: The plaintext name
* @length: The length of the plaintext
* @encoded_name: The encypted name
*
* Encrypts and encodes a filename into something that constitutes a
* valid filename for a filesystem, with printable characters.
*
* We assume that we have a properly initialized crypto context,
* pointed to by crypt_stat->tfm.
*
* Returns zero on success; non-zero on otherwise
*/
int ecryptfs_encrypt_and_encode_filename(
char **encoded_name,
size_t *encoded_name_size,
struct ecryptfs_mount_crypt_stat *mount_crypt_stat,
const char *name, size_t name_size)
{
size_t encoded_name_no_prefix_size;
int rc = 0;
(*encoded_name) = NULL;
(*encoded_name_size) = 0;
if (mount_crypt_stat && (mount_crypt_stat->flags
& ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
struct ecryptfs_filename *filename;
filename = kzalloc(sizeof(*filename), GFP_KERNEL);
if (!filename) {
rc = -ENOMEM;
goto out;
}
filename->filename = (char *)name;
filename->filename_size = name_size;
rc = ecryptfs_encrypt_filename(filename, mount_crypt_stat);
if (rc) {
printk(KERN_ERR "%s: Error attempting to encrypt "
"filename; rc = [%d]\n", __func__, rc);
kfree(filename);
goto out;
}
ecryptfs_encode_for_filename(
NULL, &encoded_name_no_prefix_size,
filename->encrypted_filename,
filename->encrypted_filename_size);
if (mount_crypt_stat
&& (mount_crypt_stat->flags
& ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK))
(*encoded_name_size) =
(ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE
+ encoded_name_no_prefix_size);
else
(*encoded_name_size) =
(ECRYPTFS_FEK_ENCRYPTED_FILENAME_PREFIX_SIZE
+ encoded_name_no_prefix_size);
(*encoded_name) = kmalloc((*encoded_name_size) + 1, GFP_KERNEL);
if (!(*encoded_name)) {
rc = -ENOMEM;
kfree(filename->encrypted_filename);
kfree(filename);
goto out;
}
if (mount_crypt_stat
&& (mount_crypt_stat->flags
& ECRYPTFS_GLOBAL_ENCFN_USE_MOUNT_FNEK)) {
memcpy((*encoded_name),
ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE);
ecryptfs_encode_for_filename(
((*encoded_name)
+ ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE),
&encoded_name_no_prefix_size,
filename->encrypted_filename,
filename->encrypted_filename_size);
(*encoded_name_size) =
(ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE
+ encoded_name_no_prefix_size);
(*encoded_name)[(*encoded_name_size)] = '\0';
} else {
rc = -EOPNOTSUPP;
}
if (rc) {
printk(KERN_ERR "%s: Error attempting to encode "
"encrypted filename; rc = [%d]\n", __func__,
rc);
kfree((*encoded_name));
(*encoded_name) = NULL;
(*encoded_name_size) = 0;
}
kfree(filename->encrypted_filename);
kfree(filename);
} else {
rc = ecryptfs_copy_filename(encoded_name,
encoded_name_size,
name, name_size);
}
out:
return rc;
}
static bool is_dot_dotdot(const char *name, size_t name_size)
{
if (name_size == 1 && name[0] == '.')
return true;
else if (name_size == 2 && name[0] == '.' && name[1] == '.')
return true;
return false;
}
/**
* ecryptfs_decode_and_decrypt_filename - converts the encoded cipher text name to decoded plaintext
* @plaintext_name: The plaintext name
* @plaintext_name_size: The plaintext name size
* @ecryptfs_dir_dentry: eCryptfs directory dentry
* @name: The filename in cipher text
* @name_size: The cipher text name size
*
* Decrypts and decodes the filename.
*
* Returns zero on error; non-zero otherwise
*/
int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,
size_t *plaintext_name_size,
struct super_block *sb,
const char *name, size_t name_size)
{
struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
&ecryptfs_superblock_to_private(sb)->mount_crypt_stat;
char *decoded_name;
size_t decoded_name_size;
size_t packet_size;
int rc = 0;
if ((mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES) &&
!(mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)) {
if (is_dot_dotdot(name, name_size)) {
rc = ecryptfs_copy_filename(plaintext_name,
plaintext_name_size,
name, name_size);
goto out;
}
if (name_size <= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE ||
strncmp(name, ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE)) {
rc = -EINVAL;
goto out;
}
name += ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
name_size -= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
ecryptfs_decode_from_filename(NULL, &decoded_name_size,
name, name_size);
decoded_name = kmalloc(decoded_name_size, GFP_KERNEL);
if (!decoded_name) {
rc = -ENOMEM;
goto out;
}
ecryptfs_decode_from_filename(decoded_name, &decoded_name_size,
name, name_size);
rc = ecryptfs_parse_tag_70_packet(plaintext_name,
plaintext_name_size,
&packet_size,
mount_crypt_stat,
decoded_name,
decoded_name_size);
if (rc) {
ecryptfs_printk(KERN_DEBUG,
"%s: Could not parse tag 70 packet from filename\n",
__func__);
goto out_free;
}
} else {
rc = ecryptfs_copy_filename(plaintext_name,
plaintext_name_size,
name, name_size);
goto out;
}
out_free:
kfree(decoded_name);
out:
return rc;
}
#define ENC_NAME_MAX_BLOCKLEN_8_OR_16 143
int ecryptfs_set_f_namelen(long *namelen, long lower_namelen,
struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
struct crypto_skcipher *tfm;
struct mutex *tfm_mutex;
size_t cipher_blocksize;
int rc;
if (!(mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
(*namelen) = lower_namelen;
return 0;
}
rc = ecryptfs_get_tfm_and_mutex_for_cipher_name(&tfm, &tfm_mutex,
mount_crypt_stat->global_default_fn_cipher_name);
if (unlikely(rc)) {
(*namelen) = 0;
return rc;
}
mutex_lock(tfm_mutex);
cipher_blocksize = crypto_skcipher_blocksize(tfm);
mutex_unlock(tfm_mutex);
/* Return an exact amount for the common cases */
if (lower_namelen == NAME_MAX
&& (cipher_blocksize == 8 || cipher_blocksize == 16)) {
(*namelen) = ENC_NAME_MAX_BLOCKLEN_8_OR_16;
return 0;
}
/* Return a safe estimate for the uncommon cases */
(*namelen) = lower_namelen;
(*namelen) -= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
/* Since this is the max decoded size, subtract 1 "decoded block" len */
(*namelen) = ecryptfs_max_decoded_size(*namelen) - 3;
(*namelen) -= ECRYPTFS_TAG_70_MAX_METADATA_SIZE;
(*namelen) -= ECRYPTFS_FILENAME_MIN_RANDOM_PREPEND_BYTES;
/* Worst case is that the filename is padded nearly a full block size */
(*namelen) -= cipher_blocksize - 1;
if ((*namelen) < 0)
(*namelen) = 0;
return 0;
}
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