/*
* linux/fs/f2fs/crypto_fname.c
*
* Copied from linux/fs/ext4/crypto.c
*
* Copyright (C) 2015, Google, Inc.
* Copyright (C) 2015, Motorola Mobility
*
* This contains functions for filename crypto management in f2fs
*
* Written by Uday Savagaonkar, 2014.
*
* Adjust f2fs dentry structure
* Jaegeuk Kim, 2015.
*
* This has not yet undergone a rigorous security audit.
*/
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <keys/encrypted-type.h>
#include <keys/user-type.h>
#include <linux/crypto.h>
#include <linux/gfp.h>
#include <linux/kernel.h>
#include <linux/key.h>
#include <linux/list.h>
#include <linux/mempool.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <linux/spinlock_types.h>
#include <linux/f2fs_fs.h>
#include <linux/ratelimit.h>
#include "f2fs.h"
#include "f2fs_crypto.h"
#include "xattr.h"
/**
* f2fs_dir_crypt_complete() -
*/
static void f2fs_dir_crypt_complete(struct crypto_async_request *req, int res)
{
struct f2fs_completion_result *ecr = req->data;
if (res == -EINPROGRESS)
return;
ecr->res = res;
complete(&ecr->completion);
}
bool f2fs_valid_filenames_enc_mode(uint32_t mode)
{
return (mode == F2FS_ENCRYPTION_MODE_AES_256_CTS);
}
static unsigned max_name_len(struct inode *inode)
{
return S_ISLNK(inode->i_mode) ? inode->i_sb->s_blocksize :
F2FS_NAME_LEN;
}
/**
* f2fs_fname_encrypt() -
*
* This function encrypts the input filename, and returns the length of the
* ciphertext. Errors are returned as negative numbers. We trust the caller to
* allocate sufficient memory to oname string.
*/
static int f2fs_fname_encrypt(struct inode *inode,
const struct qstr *iname, struct f2fs_str *oname)
{
u32 ciphertext_len;
struct ablkcipher_request *req = NULL;
DECLARE_F2FS_COMPLETION_RESULT(ecr);
struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
struct crypto_ablkcipher *tfm = ci->ci_ctfm;
int res = 0;
char iv[F2FS_CRYPTO_BLOCK_SIZE];
struct scatterlist src_sg, dst_sg;
int padding = 4 << (ci->ci_flags & F2FS_POLICY_FLAGS_PAD_MASK);
char *workbuf, buf[32], *alloc_buf = NULL;
unsigned lim = max_name_len(inode);
if (iname->len <= 0 || iname->len > lim)
return -EIO;
ciphertext_len = (iname->len < F2FS_CRYPTO_BLOCK_SIZE) ?
F2FS_CRYPTO_BLOCK_SIZE : iname->len;
ciphertext_len = f2fs_fname_crypto_round_up(ciphertext_len, padding);
ciphertext_len = (ciphertext_len > lim) ? lim : ciphertext_len;
if (ciphertext_len <= sizeof(buf)) {
workbuf = buf;
} else {
alloc_buf = kmalloc(ciphertext_len, GFP_NOFS);
if (!alloc_buf)
return -ENOMEM;
workbuf = alloc_buf;
}
/* Allocate request */
req = ablkcipher_request_alloc(tfm, GFP_NOFS);
if (!req) {
printk_ratelimited(KERN_ERR
"%s: crypto_request_alloc() failed\n", __func__);
kfree(alloc_buf);
return -ENOMEM;
}
ablkcipher_request_set_callback(req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
f2fs_dir_crypt_complete, &ecr);
/* Copy the input */
memcpy(workbuf, iname->name, iname->len);
if (iname->len < ciphertext_len)
memset(workbuf + iname->len, 0, ciphertext_len - iname->len);
/* Initialize IV */
memset(iv, 0, F2FS_CRYPTO_BLOCK_SIZE);
/* Create encryption request */
sg_init_one(&src_sg, workbuf, ciphertext_len);
sg_init_one(&dst_sg, oname->name, ciphertext_len);
ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, ciphertext_len, iv);
res = crypto_ablkcipher_encrypt(req);
if (res == -EINPROGRESS || res == -EBUSY) {
BUG_ON(req->base.data != &ecr);
wait_for_completion(&ecr.completion);
res = ecr.res;
}
kfree(alloc_buf);
ablkcipher_request_free(req);
if (res < 0) {
printk_ratelimited(KERN_ERR
"%s: Error (error code %d)\n", __func__, res);
}
oname->len = ciphertext_len;
return res;
}
/*
* f2fs_fname_decrypt()
* This function decrypts the input filename, and returns
* the length of the plaintext.
* Errors are returned as negative numbers.
* We trust the caller to allocate sufficient memory to oname string.
*/
static int f2fs_fname_decrypt(struct inode *inode,
const struct f2fs_str *iname, struct f2fs_str *oname)
{
struct ablkcipher_request *req = NULL;
DECLARE_F2FS_COMPLETION_RESULT(ecr);
struct scatterlist src_sg, dst_sg;
struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
struct crypto_ablkcipher *tfm = ci->ci_ctfm;
int res = 0;
char iv[F2FS_CRYPTO_BLOCK_SIZE];
unsigned lim = max_name_len(inode);
if (iname->len <= 0 || iname->len > lim)
return -EIO;
/* Allocate request */
req = ablkcipher_request_alloc(tfm, GFP_NOFS);
if (!req) {
printk_ratelimited(KERN_ERR
"%s: crypto_request_alloc() failed\n", __func__);
return -ENOMEM;
}
ablkcipher_request_set_callback(req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
f2fs_dir_crypt_complete, &ecr);
/* Initialize IV */
memset(iv, 0, F2FS_CRYPTO_BLOCK_SIZE);
/* Create decryption request */
sg_init_one(&src_sg, iname->name, iname->len);
sg_init_one(&dst_sg, oname->name, oname->len);
ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv);
res = crypto_ablkcipher_decrypt(req);
if (res == -EINPROGRESS || res == -EBUSY) {
BUG_ON(req->base.data != &ecr);
wait_for_completion(&ecr.completion);
res = ecr.res;
}
ablkcipher_request_free(req);
if (res < 0) {
printk_ratelimited(KERN_ERR
"%s: Error in f2fs_fname_decrypt (error code %d)\n",
__func__, res);
return res;
}
oname->len = strnlen(oname->name, iname->len);
return oname->len;
}
static const char *lookup_table =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
/**
* f2fs_fname_encode_digest() -
*
* Encodes the input digest using characters from the set [a-zA-Z0-9_+].
* The encoded string is roughly 4/3 times the size of the input string.
*/
static int digest_encode(const char *src, int len, char *dst)
{
int i = 0, bits = 0, ac = 0;
char *cp = dst;
while (i < len) {
ac += (((unsigned char) src[i]) << bits);
bits += 8;
do {
*cp++ = lookup_table[ac & 0x3f];
ac >>= 6;
bits -= 6;
} while (bits >= 6);
i++;
}
if (bits)
*cp++ = lookup_table[ac & 0x3f];
return cp - dst;
}
static int digest_decode(const char *src, int len, char *dst)
{
int i = 0, bits = 0, ac = 0;
const char *p;
char *cp = dst;
while (i < len) {
p = strchr(lookup_table, src[i]);
if (p == NULL || src[i] == 0)
return -2;
ac += (p - lookup_table) << bits;
bits += 6;
if (bits >= 8) {
*cp++ = ac & 0xff;
ac >>= 8;
bits -= 8;
}
i++;
}
if (ac)
return -1;
return cp - dst;
}
/**
* f2fs_fname_crypto_round_up() -
*
* Return: The next multiple of block size
*/
u32 f2fs_fname_crypto_round_up(u32 size, u32 blksize)
{
return ((size + blksize - 1) / blksize) * blksize;
}
/**
* f2fs_fname_crypto_alloc_obuff() -
*
* Allocates an output buffer that is sufficient for the crypto operation
* specified by the context and the direction.
*/
int f2fs_fname_crypto_alloc_buffer(struct inode *inode,
u32 ilen, struct f2fs_str *crypto_str)
{
unsigned int olen;
int padding = 16;
struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
if (ci)
padding = 4 << (ci->ci_flags & F2FS_POLICY_FLAGS_PAD_MASK);
if (padding < F2FS_CRYPTO_BLOCK_SIZE)
padding = F2FS_CRYPTO_BLOCK_SIZE;
olen = f2fs_fname_crypto_round_up(ilen, padding);
crypto_str->len = olen;
if (olen < F2FS_FNAME_CRYPTO_DIGEST_SIZE * 2)
olen = F2FS_FNAME_CRYPTO_DIGEST_SIZE * 2;
/* Allocated buffer can hold one more character to null-terminate the
* string */
crypto_str->name = kmalloc(olen + 1, GFP_NOFS);
if (!(crypto_str->name))
return -ENOMEM;
return 0;
}
/**
* f2fs_fname_crypto_free_buffer() -
*
* Frees the buffer allocated for crypto operation.
*/
void f2fs_fname_crypto_free_buffer(struct f2fs_str *crypto_str)
{
if (!crypto_str)
return;
kfree(crypto_str->name);
crypto_str->name = NULL;
}
/**
* f2fs_fname_disk_to_usr() - converts a filename from disk space to user space
*/
int f2fs_fname_disk_to_usr(struct inode *inode,
f2fs_hash_t *hash,
const struct f2fs_str *iname,
struct f2fs_str *oname)
{
const struct qstr qname = FSTR_TO_QSTR(iname);
char buf[24];
int ret;
if (is_dot_dotdot(&qname)) {
oname->name[0] = '.';
oname->name[iname->len - 1] = '.';
oname->len = iname->len;
return oname->len;
}
if (F2FS_I(inode)->i_crypt_info)
return f2fs_fname_decrypt(inode, iname, oname);
if (iname->len <= F2FS_FNAME_CRYPTO_DIGEST_SIZE) {
ret = digest_encode(iname->name, iname->len, oname->name);
oname->len = ret;
return ret;
}
if (hash) {
memcpy(buf, hash, 4);
memset(buf + 4, 0, 4);
} else
memset(buf, 0, 8);
memcpy(buf + 8, iname->name + iname->len - 16, 16);
oname->name[0] = '_';
ret = digest_encode(buf, 24, oname->name + 1);
oname->len = ret + 1;
return ret + 1;
}
/**
* f2fs_fname_usr_to_disk() - converts a filename from user space to disk space
*/
int f2fs_fname_usr_to_disk(struct inode *inode,
const struct qstr *iname,
struct f2fs_str *oname)
{
int res;
struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
if (is_dot_dotdot(iname)) {
oname->name[0] = '.';
oname->name[iname->len - 1] = '.';
oname->len = iname->len;
return oname->len;
}
if (ci) {
res = f2fs_fname_encrypt(inode, iname, oname);
return res;
}
/* Without a proper key, a user is not allowed to modify the filenames
* in a directory. Consequently, a user space name cannot be mapped to
* a disk-space name */
return -EACCES;
}
int f2fs_fname_setup_filename(struct inode *dir, const struct qstr *iname,
int lookup, struct f2fs_filename *fname)
{
struct f2fs_crypt_info *ci;
int ret = 0, bigname = 0;
memset(fname, 0, sizeof(struct f2fs_filename));
fname->usr_fname = iname;
if (!f2fs_encrypted_inode(dir) || is_dot_dotdot(iname)) {
fname->disk_name.name = (unsigned char *)iname->name;
fname->disk_name.len = iname->len;
return 0;
}
ret = f2fs_get_encryption_info(dir);
if (ret)
return ret;
ci = F2FS_I(dir)->i_crypt_info;
if (ci) {
ret = f2fs_fname_crypto_alloc_buffer(dir, iname->len,
&fname->crypto_buf);
if (ret < 0)
return ret;
ret = f2fs_fname_encrypt(dir, iname, &fname->crypto_buf);
if (ret < 0)
goto errout;
fname->disk_name.name = fname->crypto_buf.name;
fname->disk_name.len = fname->crypto_buf.len;
return 0;
}
if (!lookup)
return -EACCES;
/* We don't have the key and we are doing a lookup; decode the
* user-supplied name
*/
if (iname->name[0] == '_')
bigname = 1;
if ((bigname && (iname->len != 33)) ||
(!bigname && (iname->len > 43)))
return -ENOENT;
fname->crypto_buf.name = kmalloc(32, GFP_KERNEL);
if (fname->crypto_buf.name == NULL)
return -ENOMEM;
ret = digest_decode(iname->name + bigname, iname->len - bigname,
fname->crypto_buf.name);
if (ret < 0) {
ret = -ENOENT;
goto errout;
}
fname->crypto_buf.len = ret;
if (bigname) {
memcpy(&fname->hash, fname->crypto_buf.name, 4);
} else {
fname->disk_name.name = fname->crypto_buf.name;
fname->disk_name.len = fname->crypto_buf.len;
}
return 0;
errout:
f2fs_fname_crypto_free_buffer(&fname->crypto_buf);
return ret;
}
void f2fs_fname_free_filename(struct f2fs_filename *fname)
{
kfree(fname->crypto_buf.name);
fname->crypto_buf.name = NULL;
fname->usr_fname = NULL;
fname->disk_name.name = NULL;
}
