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eCryptfs: Filename Encryption: Encoding and encryption functions 

These functions support encrypting and encoding the filename contents.
The encrypted filename contents may consist of any ASCII characters.  This
patch includes a custom encoding mechanism to map the ASCII characters to
a reduced character set that is appropriate for filenames.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Cc: Dustin Kirkland <dustin.kirkland@gmail.com>
Cc: Eric Sandeen <sandeen@redhat.com>
Cc: Tyler Hicks <tchicks@us.ibm.com>
Cc: David Kleikamp <shaggy@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michael Halcrow 2009-01-06 14:41:59 -08:00 committed by Linus Torvalds
parent a34f60f748
commit 51ca58dcc9
1 changed files with 433 additions and 0 deletions
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433
fs/ecryptfs/crypto.c
View File

@ -1720,6 +1720,98 @@ out:
return error;
}
/**
* 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_crypt_stat *crypt_stat,
struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
int rc = 0;
filename->encrypted_filename = NULL;
filename->encrypted_filename_size = 0;
if ((crypt_stat && (crypt_stat->flags & ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
|| (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) {
printk(KERN_ERR "%s: Out of memory whilst attempting "
"to kmalloc [%Zd] bytes\n", __func__,
filename->encrypted_filename_size);
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 = -ENOTSUPP;
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 + 2), 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 + 1);
out:
return rc;
}
/**
* ecryptfs_process_key_cipher - Perform key cipher initialization.
* @key_tfm: Crypto context for key material, set by this function
@ -1911,3 +2003,344 @@ 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 unsigned char filename_rev_map[] = {
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
};
/**
* 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
*/
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;
}
int 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;
int rc = 0;
if (dst == NULL) {
/* Not exact; conservatively long */
(*dst_size) = (((src_size + 1) * 3) / 4);
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);
dst[dst_byte_offset] = 0;
current_bit_offset = 0;
break;
}
src_byte_offset++;
}
(*dst_size) = dst_byte_offset;
out:
return rc;
}
/**
* 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_crypt_stat *crypt_stat,
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 ((crypt_stat && (crypt_stat->flags & ECRYPTFS_ENCRYPT_FILENAMES))
|| (mount_crypt_stat && (mount_crypt_stat->flags
& ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES))) {
struct ecryptfs_filename *filename;
filename = kzalloc(sizeof(*filename), GFP_KERNEL);
if (!filename) {
printk(KERN_ERR "%s: Out of memory whilst attempting "
"to kzalloc [%d] bytes\n", __func__,
sizeof(*filename));
rc = -ENOMEM;
goto out;
}
filename->filename = (char *)name;
filename->filename_size = name_size;
rc = ecryptfs_encrypt_filename(filename, crypt_stat,
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 ((crypt_stat && (crypt_stat->flags
& ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
|| (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)) {
printk(KERN_ERR "%s: Out of memory whilst attempting "
"to kzalloc [%d] bytes\n", __func__,
(*encoded_name_size));
rc = -ENOMEM;
kfree(filename->encrypted_filename);
kfree(filename);
goto out;
}
if ((crypt_stat && (crypt_stat->flags
& ECRYPTFS_ENCFN_USE_MOUNT_FNEK))
|| (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';
(*encoded_name_size)++;
} else {
rc = -ENOTSUPP;
}
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;
}
/**
* 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 dentry *ecryptfs_dir_dentry,
const char *name, size_t name_size)
{
char *decoded_name;
size_t decoded_name_size;
size_t packet_size;
int rc = 0;
if ((name_size > ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE)
&& (strncmp(name, ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE) == 0)) {
struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
&ecryptfs_superblock_to_private(
ecryptfs_dir_dentry->d_sb)->mount_crypt_stat;
const char *orig_name = name;
size_t orig_name_size = name_size;
name += ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
name_size -= ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE;
rc = ecryptfs_decode_from_filename(NULL, &decoded_name_size,
name, name_size);
if (rc) {
printk(KERN_ERR "%s: Error attempting to decode "
"filename; rc = [%d]\n", __func__, rc);
rc = ecryptfs_copy_filename(plaintext_name,
plaintext_name_size,
orig_name, orig_name_size);
goto out;
}
decoded_name = kmalloc(decoded_name_size, GFP_KERNEL);
if (!decoded_name) {
printk(KERN_ERR "%s: Out of memory whilst attempting "
"to kmalloc [%Zd] bytes\n", __func__,
decoded_name_size);
rc = -ENOMEM;
goto out;
}
rc = ecryptfs_decode_from_filename(decoded_name,
&decoded_name_size,
name, name_size);
if (rc) {
printk(KERN_ERR "%s: Error attempting to decode "
"filename; rc = [%d]\n", __func__, rc);
rc = ecryptfs_copy_filename(plaintext_name,
plaintext_name_size,
orig_name, orig_name_size);
goto out_free;
}
rc = ecryptfs_parse_tag_70_packet(plaintext_name,
plaintext_name_size,
&packet_size,
mount_crypt_stat,
decoded_name,
decoded_name_size);
if (rc) {
printk(KERN_INFO "%s: Could not parse tag 70 packet "
"from filename; copying through filename "
"as-is\n", __func__);
rc = ecryptfs_copy_filename(plaintext_name,
plaintext_name_size,
orig_name, orig_name_size);
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;
}