/*
   * 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/hash.h>
  #include <crypto/sha.h>
  #include <keys/user-type.h>
  #include <keys/encrypted-type.h>
  #include <linux/crypto.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 ablkcipher_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_ablkcipher *tfm = ci->ci_ctfm;

  	int res = 0;

  	req = ablkcipher_request_alloc(tfm, GFP_NOFS);

  	if (!req) {
  		printk_ratelimited(KERN_ERR
  				"%s: crypto_request_alloc() failed
  ",
  				__func__);
  		return -ENOMEM;
  	}
  	ablkcipher_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);
  	ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
  					xts_tweak);
  	if (rw == F2FS_DECRYPT)
  		res = crypto_ablkcipher_decrypt(req);
  	else
  		res = crypto_ablkcipher_encrypt(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) {
  		printk_ratelimited(KERN_ERR
  			"%s: crypto_ablkcipher_encrypt() returned %d
  ",
  			__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;
  }