blob: ca2f5948c1ac52111259441ff0ee5e3405e0502a [file] [log] [blame]
/*
* linux/fs/ext4/crypto_fname.c
*
* Copyright (C) 2015, Google, Inc.
*
* This contains functions for filename crypto management in ext4
*
* Written by Uday Savagaonkar, 2014.
*
* 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/key.h>
#include <linux/list.h>
#include <linux/mempool.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <linux/spinlock_types.h>
#include "ext4.h"
#include "ext4_crypto.h"
#include "xattr.h"
/**
* ext4_dir_crypt_complete() -
*/
static void ext4_dir_crypt_complete(struct crypto_async_request *req, int res)
{
struct ext4_completion_result *ecr = req->data;
if (res == -EINPROGRESS)
return;
ecr->res = res;
complete(&ecr->completion);
}
bool ext4_valid_filenames_enc_mode(uint32_t mode)
{
return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS);
}
/**
* ext4_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 ext4_fname_encrypt(struct ext4_fname_crypto_ctx *ctx,
const struct qstr *iname,
struct ext4_str *oname)
{
u32 ciphertext_len;
struct ablkcipher_request *req = NULL;
DECLARE_EXT4_COMPLETION_RESULT(ecr);
struct crypto_ablkcipher *tfm = ctx->ctfm;
int res = 0;
char iv[EXT4_CRYPTO_BLOCK_SIZE];
struct scatterlist sg[1];
char *workbuf;
if (iname->len <= 0 || iname->len > ctx->lim)
return -EIO;
ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ?
EXT4_CRYPTO_BLOCK_SIZE : iname->len;
ciphertext_len = (ciphertext_len > ctx->lim)
? ctx->lim : ciphertext_len;
/* 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,
ext4_dir_crypt_complete, &ecr);
/* Map the workpage */
workbuf = kmap(ctx->workpage);
/* 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, EXT4_CRYPTO_BLOCK_SIZE);
/* Create encryption request */
sg_init_table(sg, 1);
sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
ablkcipher_request_set_crypt(req, sg, sg, iname->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;
}
if (res >= 0) {
/* Copy the result to output */
memcpy(oname->name, workbuf, ciphertext_len);
res = ciphertext_len;
}
kunmap(ctx->workpage);
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;
}
/*
* ext4_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 ext4_fname_decrypt(struct ext4_fname_crypto_ctx *ctx,
const struct ext4_str *iname,
struct ext4_str *oname)
{
struct ext4_str tmp_in[2], tmp_out[1];
struct ablkcipher_request *req = NULL;
DECLARE_EXT4_COMPLETION_RESULT(ecr);
struct scatterlist sg[1];
struct crypto_ablkcipher *tfm = ctx->ctfm;
int res = 0;
char iv[EXT4_CRYPTO_BLOCK_SIZE];
char *workbuf;
if (iname->len <= 0 || iname->len > ctx->lim)
return -EIO;
tmp_in[0].name = iname->name;
tmp_in[0].len = iname->len;
tmp_out[0].name = oname->name;
/* 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,
ext4_dir_crypt_complete, &ecr);
/* Map the workpage */
workbuf = kmap(ctx->workpage);
/* Copy the input */
memcpy(workbuf, iname->name, iname->len);
/* Initialize IV */
memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
/* Create encryption request */
sg_init_table(sg, 1);
sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
ablkcipher_request_set_crypt(req, sg, 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;
}
if (res >= 0) {
/* Copy the result to output */
memcpy(oname->name, workbuf, iname->len);
res = iname->len;
}
kunmap(ctx->workpage);
ablkcipher_request_free(req);
if (res < 0) {
printk_ratelimited(
KERN_ERR "%s: Error in ext4_fname_encrypt (error code %d)\n",
__func__, res);
return res;
}
oname->len = strnlen(oname->name, iname->len);
return oname->len;
}
/**
* ext4_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.
*/
int ext4_fname_encode_digest(char *dst, char *src, u32 len)
{
static const char *lookup_table =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_+";
u32 current_chunk, num_chunks, i;
char tmp_buf[3];
u32 c0, c1, c2, c3;
current_chunk = 0;
num_chunks = len/3;
for (i = 0; i < num_chunks; i++) {
c0 = src[3*i] & 0x3f;
c1 = (((src[3*i]>>6)&0x3) | ((src[3*i+1] & 0xf)<<2)) & 0x3f;
c2 = (((src[3*i+1]>>4)&0xf) | ((src[3*i+2] & 0x3)<<4)) & 0x3f;
c3 = (src[3*i+2]>>2) & 0x3f;
dst[4*i] = lookup_table[c0];
dst[4*i+1] = lookup_table[c1];
dst[4*i+2] = lookup_table[c2];
dst[4*i+3] = lookup_table[c3];
}
if (i*3 < len) {
memset(tmp_buf, 0, 3);
memcpy(tmp_buf, &src[3*i], len-3*i);
c0 = tmp_buf[0] & 0x3f;
c1 = (((tmp_buf[0]>>6)&0x3) | ((tmp_buf[1] & 0xf)<<2)) & 0x3f;
c2 = (((tmp_buf[1]>>4)&0xf) | ((tmp_buf[2] & 0x3)<<4)) & 0x3f;
c3 = (tmp_buf[2]>>2) & 0x3f;
dst[4*i] = lookup_table[c0];
dst[4*i+1] = lookup_table[c1];
dst[4*i+2] = lookup_table[c2];
dst[4*i+3] = lookup_table[c3];
i++;
}
return (i * 4);
}
/**
* ext4_fname_hash() -
*
* This function computes the hash of the input filename, and sets the output
* buffer to the *encoded* digest. It returns the length of the digest as its
* return value. Errors are returned as negative numbers. We trust the caller
* to allocate sufficient memory to oname string.
*/
static int ext4_fname_hash(struct ext4_fname_crypto_ctx *ctx,
const struct ext4_str *iname,
struct ext4_str *oname)
{
struct scatterlist sg;
struct hash_desc desc = {
.tfm = (struct crypto_hash *)ctx->htfm,
.flags = CRYPTO_TFM_REQ_MAY_SLEEP
};
int res = 0;
if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {
res = ext4_fname_encode_digest(oname->name, iname->name,
iname->len);
oname->len = res;
return res;
}
sg_init_one(&sg, iname->name, iname->len);
res = crypto_hash_init(&desc);
if (res) {
printk(KERN_ERR
"%s: Error initializing crypto hash; res = [%d]\n",
__func__, res);
goto out;
}
res = crypto_hash_update(&desc, &sg, iname->len);
if (res) {
printk(KERN_ERR
"%s: Error updating crypto hash; res = [%d]\n",
__func__, res);
goto out;
}
res = crypto_hash_final(&desc,
&oname->name[EXT4_FNAME_CRYPTO_DIGEST_SIZE]);
if (res) {
printk(KERN_ERR
"%s: Error finalizing crypto hash; res = [%d]\n",
__func__, res);
goto out;
}
/* Encode the digest as a printable string--this will increase the
* size of the digest */
oname->name[0] = 'I';
res = ext4_fname_encode_digest(oname->name+1,
&oname->name[EXT4_FNAME_CRYPTO_DIGEST_SIZE],
EXT4_FNAME_CRYPTO_DIGEST_SIZE) + 1;
oname->len = res;
out:
return res;
}
/**
* ext4_free_fname_crypto_ctx() -
*
* Frees up a crypto context.
*/
void ext4_free_fname_crypto_ctx(struct ext4_fname_crypto_ctx *ctx)
{
if (ctx == NULL || IS_ERR(ctx))
return;
if (ctx->ctfm && !IS_ERR(ctx->ctfm))
crypto_free_ablkcipher(ctx->ctfm);
if (ctx->htfm && !IS_ERR(ctx->htfm))
crypto_free_hash(ctx->htfm);
if (ctx->workpage && !IS_ERR(ctx->workpage))
__free_page(ctx->workpage);
kfree(ctx);
}
/**
* ext4_put_fname_crypto_ctx() -
*
* Return: The crypto context onto free list. If the free list is above a
* threshold, completely frees up the context, and returns the memory.
*
* TODO: Currently we directly free the crypto context. Eventually we should
* add code it to return to free list. Such an approach will increase
* efficiency of directory lookup.
*/
void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx)
{
if (*ctx == NULL || IS_ERR(*ctx))
return;
ext4_free_fname_crypto_ctx(*ctx);
*ctx = NULL;
}
/**
* ext4_search_fname_crypto_ctx() -
*/
static struct ext4_fname_crypto_ctx *ext4_search_fname_crypto_ctx(
const struct ext4_encryption_key *key)
{
return NULL;
}
/**
* ext4_alloc_fname_crypto_ctx() -
*/
struct ext4_fname_crypto_ctx *ext4_alloc_fname_crypto_ctx(
const struct ext4_encryption_key *key)
{
struct ext4_fname_crypto_ctx *ctx;
ctx = kmalloc(sizeof(struct ext4_fname_crypto_ctx), GFP_NOFS);
if (ctx == NULL)
return ERR_PTR(-ENOMEM);
if (key->mode == EXT4_ENCRYPTION_MODE_INVALID) {
/* This will automatically set key mode to invalid
* As enum for ENCRYPTION_MODE_INVALID is zero */
memset(&ctx->key, 0, sizeof(ctx->key));
} else {
memcpy(&ctx->key, key, sizeof(struct ext4_encryption_key));
}
ctx->has_valid_key = (EXT4_ENCRYPTION_MODE_INVALID == key->mode)
? 0 : 1;
ctx->ctfm_key_is_ready = 0;
ctx->ctfm = NULL;
ctx->htfm = NULL;
ctx->workpage = NULL;
return ctx;
}
/**
* ext4_get_fname_crypto_ctx() -
*
* Allocates a free crypto context and initializes it to hold
* the crypto material for the inode.
*
* Return: NULL if not encrypted. Error value on error. Valid pointer otherwise.
*/
struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(
struct inode *inode, u32 max_ciphertext_len)
{
struct ext4_fname_crypto_ctx *ctx;
struct ext4_inode_info *ei = EXT4_I(inode);
int res;
/* Check if the crypto policy is set on the inode */
res = ext4_encrypted_inode(inode);
if (res == 0)
return NULL;
if (!ext4_has_encryption_key(inode))
ext4_generate_encryption_key(inode);
/* Get a crypto context based on the key.
* A new context is allocated if no context matches the requested key.
*/
ctx = ext4_search_fname_crypto_ctx(&(ei->i_encryption_key));
if (ctx == NULL)
ctx = ext4_alloc_fname_crypto_ctx(&(ei->i_encryption_key));
if (IS_ERR(ctx))
return ctx;
if (ctx->has_valid_key) {
if (ctx->key.mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
printk_once(KERN_WARNING
"ext4: unsupported key mode %d\n",
ctx->key.mode);
return ERR_PTR(-ENOKEY);
}
/* As a first cut, we will allocate new tfm in every call.
* later, we will keep the tfm around, in case the key gets
* re-used */
if (ctx->ctfm == NULL) {
ctx->ctfm = crypto_alloc_ablkcipher("cts(cbc(aes))",
0, 0);
}
if (IS_ERR(ctx->ctfm)) {
res = PTR_ERR(ctx->ctfm);
printk(
KERN_DEBUG "%s: error (%d) allocating crypto tfm\n",
__func__, res);
ctx->ctfm = NULL;
ext4_put_fname_crypto_ctx(&ctx);
return ERR_PTR(res);
}
if (ctx->ctfm == NULL) {
printk(
KERN_DEBUG "%s: could not allocate crypto tfm\n",
__func__);
ext4_put_fname_crypto_ctx(&ctx);
return ERR_PTR(-ENOMEM);
}
if (ctx->workpage == NULL)
ctx->workpage = alloc_page(GFP_NOFS);
if (IS_ERR(ctx->workpage)) {
res = PTR_ERR(ctx->workpage);
printk(
KERN_DEBUG "%s: error (%d) allocating work page\n",
__func__, res);
ctx->workpage = NULL;
ext4_put_fname_crypto_ctx(&ctx);
return ERR_PTR(res);
}
if (ctx->workpage == NULL) {
printk(
KERN_DEBUG "%s: could not allocate work page\n",
__func__);
ext4_put_fname_crypto_ctx(&ctx);
return ERR_PTR(-ENOMEM);
}
ctx->lim = max_ciphertext_len;
crypto_ablkcipher_clear_flags(ctx->ctfm, ~0);
crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctx->ctfm),
CRYPTO_TFM_REQ_WEAK_KEY);
/* If we are lucky, we will get a context that is already
* set up with the right key. Else, we will have to
* set the key */
if (!ctx->ctfm_key_is_ready) {
/* Since our crypto objectives for filename encryption
* are pretty weak,
* we directly use the inode master key */
res = crypto_ablkcipher_setkey(ctx->ctfm,
ctx->key.raw, ctx->key.size);
if (res) {
ext4_put_fname_crypto_ctx(&ctx);
return ERR_PTR(-EIO);
}
ctx->ctfm_key_is_ready = 1;
} else {
/* In the current implementation, key should never be
* marked "ready" for a context that has just been
* allocated. So we should never reach here */
BUG();
}
}
if (ctx->htfm == NULL)
ctx->htfm = crypto_alloc_hash("sha256", 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(ctx->htfm)) {
res = PTR_ERR(ctx->htfm);
printk(KERN_DEBUG "%s: error (%d) allocating hash tfm\n",
__func__, res);
ctx->htfm = NULL;
ext4_put_fname_crypto_ctx(&ctx);
return ERR_PTR(res);
}
if (ctx->htfm == NULL) {
printk(KERN_DEBUG "%s: could not allocate hash tfm\n",
__func__);
ext4_put_fname_crypto_ctx(&ctx);
return ERR_PTR(-ENOMEM);
}
return ctx;
}
/**
* ext4_fname_crypto_round_up() -
*
* Return: The next multiple of block size
*/
u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
{
return ((size+blksize-1)/blksize)*blksize;
}
/**
* ext4_fname_crypto_namelen_on_disk() -
*/
int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx,
u32 namelen)
{
u32 ciphertext_len;
if (ctx == NULL)
return -EIO;
if (!(ctx->has_valid_key))
return -EACCES;
ciphertext_len = (namelen < EXT4_CRYPTO_BLOCK_SIZE) ?
EXT4_CRYPTO_BLOCK_SIZE : namelen;
ciphertext_len = (ciphertext_len > ctx->lim)
? ctx->lim : ciphertext_len;
return (int) ciphertext_len;
}
/**
* ext4_fname_crypto_alloc_obuff() -
*
* Allocates an output buffer that is sufficient for the crypto operation
* specified by the context and the direction.
*/
int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx,
u32 ilen, struct ext4_str *crypto_str)
{
unsigned int olen;
if (!ctx)
return -EIO;
olen = ext4_fname_crypto_round_up(ilen, EXT4_CRYPTO_BLOCK_SIZE);
crypto_str->len = olen;
if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
olen = EXT4_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;
}
/**
* ext4_fname_crypto_free_buffer() -
*
* Frees the buffer allocated for crypto operation.
*/
void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str)
{
if (!crypto_str)
return;
kfree(crypto_str->name);
crypto_str->name = NULL;
}
/**
* ext4_fname_disk_to_usr() - converts a filename from disk space to user space
*/
int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
const struct ext4_str *iname,
struct ext4_str *oname)
{
if (ctx == NULL)
return -EIO;
if (iname->len < 3) {
/*Check for . and .. */
if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') {
oname->name[0] = '.';
oname->name[iname->len-1] = '.';
oname->len = iname->len;
return oname->len;
}
}
if (ctx->has_valid_key)
return ext4_fname_decrypt(ctx, iname, oname);
else
return ext4_fname_hash(ctx, iname, oname);
}
int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
const struct ext4_dir_entry_2 *de,
struct ext4_str *oname)
{
struct ext4_str iname = {.name = (unsigned char *) de->name,
.len = de->name_len };
return _ext4_fname_disk_to_usr(ctx, &iname, oname);
}
/**
* ext4_fname_usr_to_disk() - converts a filename from user space to disk space
*/
int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx,
const struct qstr *iname,
struct ext4_str *oname)
{
int res;
if (ctx == NULL)
return -EIO;
if (iname->len < 3) {
/*Check for . and .. */
if (iname->name[0] == '.' &&
iname->name[iname->len-1] == '.') {
oname->name[0] = '.';
oname->name[iname->len-1] = '.';
oname->len = iname->len;
return oname->len;
}
}
if (ctx->has_valid_key) {
res = ext4_fname_encrypt(ctx, 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;
}
/*
* Calculate the htree hash from a filename from user space
*/
int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx,
const struct qstr *iname,
struct dx_hash_info *hinfo)
{
struct ext4_str tmp, tmp2;
int ret = 0;
if (!ctx || !ctx->has_valid_key ||
((iname->name[0] == '.') &&
((iname->len == 1) ||
((iname->name[1] == '.') && (iname->len == 2))))) {
ext4fs_dirhash(iname->name, iname->len, hinfo);
return 0;
}
/* First encrypt the plaintext name */
ret = ext4_fname_crypto_alloc_buffer(ctx, iname->len, &tmp);
if (ret < 0)
return ret;
ret = ext4_fname_encrypt(ctx, iname, &tmp);
if (ret < 0)
goto out;
tmp2.len = (4 * ((EXT4_FNAME_CRYPTO_DIGEST_SIZE + 2) / 3)) + 1;
tmp2.name = kmalloc(tmp2.len + 1, GFP_KERNEL);
if (tmp2.name == NULL) {
ret = -ENOMEM;
goto out;
}
ret = ext4_fname_hash(ctx, &tmp, &tmp2);
if (ret > 0)
ext4fs_dirhash(tmp2.name, tmp2.len, hinfo);
ext4_fname_crypto_free_buffer(&tmp2);
out:
ext4_fname_crypto_free_buffer(&tmp);
return ret;
}
/**
* ext4_fname_disk_to_htree() - converts a filename from disk space to htree-access string
*/
int ext4_fname_disk_to_hash(struct ext4_fname_crypto_ctx *ctx,
const struct ext4_dir_entry_2 *de,
struct dx_hash_info *hinfo)
{
struct ext4_str iname = {.name = (unsigned char *) de->name,
.len = de->name_len};
struct ext4_str tmp;
int ret;
if (!ctx ||
((iname.name[0] == '.') &&
((iname.len == 1) ||
((iname.name[1] == '.') && (iname.len == 2))))) {
ext4fs_dirhash(iname.name, iname.len, hinfo);
return 0;
}
tmp.len = (4 * ((EXT4_FNAME_CRYPTO_DIGEST_SIZE + 2) / 3)) + 1;
tmp.name = kmalloc(tmp.len + 1, GFP_KERNEL);
if (tmp.name == NULL)
return -ENOMEM;
ret = ext4_fname_hash(ctx, &iname, &tmp);
if (ret > 0)
ext4fs_dirhash(tmp.name, tmp.len, hinfo);
ext4_fname_crypto_free_buffer(&tmp);
return ret;
}