blob: 95c5cf039711c6c994ef8b4a04d0ef37f777591d [file] [log] [blame]
/*
* linux/fs/f2fs/crypto.c
*
* Copied from linux/fs/ext4/crypto.c
*
* Copyright (C) 2015, Google, Inc.
* Copyright (C) 2015, Motorola Mobility
*
* This contains encryption functions for f2fs
*
* Written by Michael Halcrow, 2014.
*
* Filename encryption additions
* Uday Savagaonkar, 2014
* Encryption policy handling additions
* Ildar Muslukhov, 2014
* Remove ext4_encrypted_zeroout(),
* add f2fs_restore_and_release_control_page()
* Jaegeuk Kim, 2015.
*
* This has not yet undergone a rigorous security audit.
*
* The usage of AES-XTS should conform to recommendations in NIST
* Special Publication 800-38E and IEEE P1619/D16.
*/
#include <crypto/skcipher.h>
#include <keys/user-type.h>
#include <keys/encrypted-type.h>
#include <linux/ecryptfs.h>
#include <linux/gfp.h>
#include <linux/kernel.h>
#include <linux/key.h>
#include <linux/list.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <linux/spinlock_types.h>
#include <linux/f2fs_fs.h>
#include <linux/ratelimit.h>
#include <linux/bio.h>
#include "f2fs.h"
#include "xattr.h"
/* Encryption added and removed here! (L: */
static unsigned int num_prealloc_crypto_pages = 32;
static unsigned int num_prealloc_crypto_ctxs = 128;
module_param(num_prealloc_crypto_pages, uint, 0444);
MODULE_PARM_DESC(num_prealloc_crypto_pages,
"Number of crypto pages to preallocate");
module_param(num_prealloc_crypto_ctxs, uint, 0444);
MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
"Number of crypto contexts to preallocate");
static mempool_t *f2fs_bounce_page_pool;
static LIST_HEAD(f2fs_free_crypto_ctxs);
static DEFINE_SPINLOCK(f2fs_crypto_ctx_lock);
static struct workqueue_struct *f2fs_read_workqueue;
static DEFINE_MUTEX(crypto_init);
static struct kmem_cache *f2fs_crypto_ctx_cachep;
struct kmem_cache *f2fs_crypt_info_cachep;
/**
* f2fs_release_crypto_ctx() - Releases an encryption context
* @ctx: The encryption context to release.
*
* If the encryption context was allocated from the pre-allocated pool, returns
* it to that pool. Else, frees it.
*
* If there's a bounce page in the context, this frees that.
*/
void f2fs_release_crypto_ctx(struct f2fs_crypto_ctx *ctx)
{
unsigned long flags;
if (ctx->flags & F2FS_WRITE_PATH_FL && ctx->w.bounce_page) {
mempool_free(ctx->w.bounce_page, f2fs_bounce_page_pool);
ctx->w.bounce_page = NULL;
}
ctx->w.control_page = NULL;
if (ctx->flags & F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
kmem_cache_free(f2fs_crypto_ctx_cachep, ctx);
} else {
spin_lock_irqsave(&f2fs_crypto_ctx_lock, flags);
list_add(&ctx->free_list, &f2fs_free_crypto_ctxs);
spin_unlock_irqrestore(&f2fs_crypto_ctx_lock, flags);
}
}
/**
* f2fs_get_crypto_ctx() - Gets an encryption context
* @inode: The inode for which we are doing the crypto
*
* Allocates and initializes an encryption context.
*
* Return: An allocated and initialized encryption context on success; error
* value or NULL otherwise.
*/
struct f2fs_crypto_ctx *f2fs_get_crypto_ctx(struct inode *inode)
{
struct f2fs_crypto_ctx *ctx = NULL;
unsigned long flags;
struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
if (ci == NULL)
return ERR_PTR(-ENOKEY);
/*
* We first try getting the ctx from a free list because in
* the common case the ctx will have an allocated and
* initialized crypto tfm, so it's probably a worthwhile
* optimization. For the bounce page, we first try getting it
* from the kernel allocator because that's just about as fast
* as getting it from a list and because a cache of free pages
* should generally be a "last resort" option for a filesystem
* to be able to do its job.
*/
spin_lock_irqsave(&f2fs_crypto_ctx_lock, flags);
ctx = list_first_entry_or_null(&f2fs_free_crypto_ctxs,
struct f2fs_crypto_ctx, free_list);
if (ctx)
list_del(&ctx->free_list);
spin_unlock_irqrestore(&f2fs_crypto_ctx_lock, flags);
if (!ctx) {
ctx = kmem_cache_zalloc(f2fs_crypto_ctx_cachep, GFP_NOFS);
if (!ctx)
return ERR_PTR(-ENOMEM);
ctx->flags |= F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
} else {
ctx->flags &= ~F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
}
ctx->flags &= ~F2FS_WRITE_PATH_FL;
return ctx;
}
/*
* Call f2fs_decrypt on every single page, reusing the encryption
* context.
*/
static void completion_pages(struct work_struct *work)
{
struct f2fs_crypto_ctx *ctx =
container_of(work, struct f2fs_crypto_ctx, r.work);
struct bio *bio = ctx->r.bio;
struct bio_vec *bv;
int i;
bio_for_each_segment_all(bv, bio, i) {
struct page *page = bv->bv_page;
int ret = f2fs_decrypt(ctx, page);
if (ret) {
WARN_ON_ONCE(1);
SetPageError(page);
} else
SetPageUptodate(page);
unlock_page(page);
}
f2fs_release_crypto_ctx(ctx);
bio_put(bio);
}
void f2fs_end_io_crypto_work(struct f2fs_crypto_ctx *ctx, struct bio *bio)
{
INIT_WORK(&ctx->r.work, completion_pages);
ctx->r.bio = bio;
queue_work(f2fs_read_workqueue, &ctx->r.work);
}
static void f2fs_crypto_destroy(void)
{
struct f2fs_crypto_ctx *pos, *n;
list_for_each_entry_safe(pos, n, &f2fs_free_crypto_ctxs, free_list)
kmem_cache_free(f2fs_crypto_ctx_cachep, pos);
INIT_LIST_HEAD(&f2fs_free_crypto_ctxs);
if (f2fs_bounce_page_pool)
mempool_destroy(f2fs_bounce_page_pool);
f2fs_bounce_page_pool = NULL;
}
/**
* f2fs_crypto_initialize() - Set up for f2fs encryption.
*
* We only call this when we start accessing encrypted files, since it
* results in memory getting allocated that wouldn't otherwise be used.
*
* Return: Zero on success, non-zero otherwise.
*/
int f2fs_crypto_initialize(void)
{
int i, res = -ENOMEM;
if (f2fs_bounce_page_pool)
return 0;
mutex_lock(&crypto_init);
if (f2fs_bounce_page_pool)
goto already_initialized;
for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
struct f2fs_crypto_ctx *ctx;
ctx = kmem_cache_zalloc(f2fs_crypto_ctx_cachep, GFP_KERNEL);
if (!ctx)
goto fail;
list_add(&ctx->free_list, &f2fs_free_crypto_ctxs);
}
/* must be allocated at the last step to avoid race condition above */
f2fs_bounce_page_pool =
mempool_create_page_pool(num_prealloc_crypto_pages, 0);
if (!f2fs_bounce_page_pool)
goto fail;
already_initialized:
mutex_unlock(&crypto_init);
return 0;
fail:
f2fs_crypto_destroy();
mutex_unlock(&crypto_init);
return res;
}
/**
* f2fs_exit_crypto() - Shutdown the f2fs encryption system
*/
void f2fs_exit_crypto(void)
{
f2fs_crypto_destroy();
if (f2fs_read_workqueue)
destroy_workqueue(f2fs_read_workqueue);
if (f2fs_crypto_ctx_cachep)
kmem_cache_destroy(f2fs_crypto_ctx_cachep);
if (f2fs_crypt_info_cachep)
kmem_cache_destroy(f2fs_crypt_info_cachep);
}
int __init f2fs_init_crypto(void)
{
int res = -ENOMEM;
f2fs_read_workqueue = alloc_workqueue("f2fs_crypto", WQ_HIGHPRI, 0);
if (!f2fs_read_workqueue)
goto fail;
f2fs_crypto_ctx_cachep = KMEM_CACHE(f2fs_crypto_ctx,
SLAB_RECLAIM_ACCOUNT);
if (!f2fs_crypto_ctx_cachep)
goto fail;
f2fs_crypt_info_cachep = KMEM_CACHE(f2fs_crypt_info,
SLAB_RECLAIM_ACCOUNT);
if (!f2fs_crypt_info_cachep)
goto fail;
return 0;
fail:
f2fs_exit_crypto();
return res;
}
void f2fs_restore_and_release_control_page(struct page **page)
{
struct f2fs_crypto_ctx *ctx;
struct page *bounce_page;
/* The bounce data pages are unmapped. */
if ((*page)->mapping)
return;
/* The bounce data page is unmapped. */
bounce_page = *page;
ctx = (struct f2fs_crypto_ctx *)page_private(bounce_page);
/* restore control page */
*page = ctx->w.control_page;
f2fs_restore_control_page(bounce_page);
}
void f2fs_restore_control_page(struct page *data_page)
{
struct f2fs_crypto_ctx *ctx =
(struct f2fs_crypto_ctx *)page_private(data_page);
set_page_private(data_page, (unsigned long)NULL);
ClearPagePrivate(data_page);
unlock_page(data_page);
f2fs_release_crypto_ctx(ctx);
}
/**
* f2fs_crypt_complete() - The completion callback for page encryption
* @req: The asynchronous encryption request context
* @res: The result of the encryption operation
*/
static void f2fs_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);
}
typedef enum {
F2FS_DECRYPT = 0,
F2FS_ENCRYPT,
} f2fs_direction_t;
static int f2fs_page_crypto(struct f2fs_crypto_ctx *ctx,
struct inode *inode,
f2fs_direction_t rw,
pgoff_t index,
struct page *src_page,
struct page *dest_page)
{
u8 xts_tweak[F2FS_XTS_TWEAK_SIZE];
struct skcipher_request *req = NULL;
DECLARE_F2FS_COMPLETION_RESULT(ecr);
struct scatterlist dst, src;
struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
struct crypto_skcipher *tfm = ci->ci_ctfm;
int res = 0;
req = skcipher_request_alloc(tfm, GFP_NOFS);
if (!req) {
printk_ratelimited(KERN_ERR
"%s: crypto_request_alloc() failed\n",
__func__);
return -ENOMEM;
}
skcipher_request_set_callback(
req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
f2fs_crypt_complete, &ecr);
BUILD_BUG_ON(F2FS_XTS_TWEAK_SIZE < sizeof(index));
memcpy(xts_tweak, &index, sizeof(index));
memset(&xts_tweak[sizeof(index)], 0,
F2FS_XTS_TWEAK_SIZE - sizeof(index));
sg_init_table(&dst, 1);
sg_set_page(&dst, dest_page, PAGE_CACHE_SIZE, 0);
sg_init_table(&src, 1);
sg_set_page(&src, src_page, PAGE_CACHE_SIZE, 0);
skcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
xts_tweak);
if (rw == F2FS_DECRYPT)
res = crypto_skcipher_decrypt(req);
else
res = crypto_skcipher_encrypt(req);
if (res == -EINPROGRESS || res == -EBUSY) {
BUG_ON(req->base.data != &ecr);
wait_for_completion(&ecr.completion);
res = ecr.res;
}
skcipher_request_free(req);
if (res) {
printk_ratelimited(KERN_ERR
"%s: crypto_skcipher_encrypt() returned %d\n",
__func__, res);
return res;
}
return 0;
}
static struct page *alloc_bounce_page(struct f2fs_crypto_ctx *ctx)
{
ctx->w.bounce_page = mempool_alloc(f2fs_bounce_page_pool, GFP_NOWAIT);
if (ctx->w.bounce_page == NULL)
return ERR_PTR(-ENOMEM);
ctx->flags |= F2FS_WRITE_PATH_FL;
return ctx->w.bounce_page;
}
/**
* f2fs_encrypt() - Encrypts a page
* @inode: The inode for which the encryption should take place
* @plaintext_page: The page to encrypt. Must be locked.
*
* Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
* encryption context.
*
* Called on the page write path. The caller must call
* f2fs_restore_control_page() on the returned ciphertext page to
* release the bounce buffer and the encryption context.
*
* Return: An allocated page with the encrypted content on success. Else, an
* error value or NULL.
*/
struct page *f2fs_encrypt(struct inode *inode,
struct page *plaintext_page)
{
struct f2fs_crypto_ctx *ctx;
struct page *ciphertext_page = NULL;
int err;
BUG_ON(!PageLocked(plaintext_page));
ctx = f2fs_get_crypto_ctx(inode);
if (IS_ERR(ctx))
return (struct page *)ctx;
/* The encryption operation will require a bounce page. */
ciphertext_page = alloc_bounce_page(ctx);
if (IS_ERR(ciphertext_page))
goto err_out;
ctx->w.control_page = plaintext_page;
err = f2fs_page_crypto(ctx, inode, F2FS_ENCRYPT, plaintext_page->index,
plaintext_page, ciphertext_page);
if (err) {
ciphertext_page = ERR_PTR(err);
goto err_out;
}
SetPagePrivate(ciphertext_page);
set_page_private(ciphertext_page, (unsigned long)ctx);
lock_page(ciphertext_page);
return ciphertext_page;
err_out:
f2fs_release_crypto_ctx(ctx);
return ciphertext_page;
}
/**
* f2fs_decrypt() - Decrypts a page in-place
* @ctx: The encryption context.
* @page: The page to decrypt. Must be locked.
*
* Decrypts page in-place using the ctx encryption context.
*
* Called from the read completion callback.
*
* Return: Zero on success, non-zero otherwise.
*/
int f2fs_decrypt(struct f2fs_crypto_ctx *ctx, struct page *page)
{
BUG_ON(!PageLocked(page));
return f2fs_page_crypto(ctx, page->mapping->host,
F2FS_DECRYPT, page->index, page, page);
}
/*
* Convenience function which takes care of allocating and
* deallocating the encryption context
*/
int f2fs_decrypt_one(struct inode *inode, struct page *page)
{
struct f2fs_crypto_ctx *ctx = f2fs_get_crypto_ctx(inode);
int ret;
if (IS_ERR(ctx))
return PTR_ERR(ctx);
ret = f2fs_decrypt(ctx, page);
f2fs_release_crypto_ctx(ctx);
return ret;
}
bool f2fs_valid_contents_enc_mode(uint32_t mode)
{
return (mode == F2FS_ENCRYPTION_MODE_AES_256_XTS);
}
/**
* f2fs_validate_encryption_key_size() - Validate the encryption key size
* @mode: The key mode.
* @size: The key size to validate.
*
* Return: The validated key size for @mode. Zero if invalid.
*/
uint32_t f2fs_validate_encryption_key_size(uint32_t mode, uint32_t size)
{
if (size == f2fs_encryption_key_size(mode))
return size;
return 0;
}