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396 lines
12 KiB
396 lines
12 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* This contains encryption functions for per-file encryption. |
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* |
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* Copyright (C) 2015, Google, Inc. |
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* Copyright (C) 2015, Motorola Mobility |
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* |
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* Written by Michael Halcrow, 2014. |
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* |
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* Filename encryption additions |
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* Uday Savagaonkar, 2014 |
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* Encryption policy handling additions |
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* Ildar Muslukhov, 2014 |
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* Add fscrypt_pullback_bio_page() |
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* Jaegeuk Kim, 2015. |
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* |
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* This has not yet undergone a rigorous security audit. |
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* |
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* The usage of AES-XTS should conform to recommendations in NIST |
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* Special Publication 800-38E and IEEE P1619/D16. |
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*/ |
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#include <linux/pagemap.h> |
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#include <linux/mempool.h> |
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#include <linux/module.h> |
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#include <linux/scatterlist.h> |
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#include <linux/ratelimit.h> |
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#include <crypto/skcipher.h> |
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#include "fscrypt_private.h" |
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static unsigned int num_prealloc_crypto_pages = 32; |
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module_param(num_prealloc_crypto_pages, uint, 0444); |
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MODULE_PARM_DESC(num_prealloc_crypto_pages, |
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"Number of crypto pages to preallocate"); |
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static mempool_t *fscrypt_bounce_page_pool = NULL; |
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static struct workqueue_struct *fscrypt_read_workqueue; |
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static DEFINE_MUTEX(fscrypt_init_mutex); |
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struct kmem_cache *fscrypt_info_cachep; |
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void fscrypt_enqueue_decrypt_work(struct work_struct *work) |
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{ |
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queue_work(fscrypt_read_workqueue, work); |
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} |
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EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work); |
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struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags) |
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{ |
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return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags); |
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} |
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/** |
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* fscrypt_free_bounce_page() - free a ciphertext bounce page |
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* @bounce_page: the bounce page to free, or NULL |
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* |
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* Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(), |
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* or by fscrypt_alloc_bounce_page() directly. |
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*/ |
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void fscrypt_free_bounce_page(struct page *bounce_page) |
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{ |
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if (!bounce_page) |
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return; |
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set_page_private(bounce_page, (unsigned long)NULL); |
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ClearPagePrivate(bounce_page); |
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mempool_free(bounce_page, fscrypt_bounce_page_pool); |
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} |
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EXPORT_SYMBOL(fscrypt_free_bounce_page); |
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void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num, |
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const struct fscrypt_info *ci) |
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{ |
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u8 flags = fscrypt_policy_flags(&ci->ci_policy); |
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memset(iv, 0, ci->ci_mode->ivsize); |
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if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { |
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WARN_ON_ONCE(lblk_num > U32_MAX); |
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WARN_ON_ONCE(ci->ci_inode->i_ino > U32_MAX); |
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lblk_num |= (u64)ci->ci_inode->i_ino << 32; |
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} else if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { |
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WARN_ON_ONCE(lblk_num > U32_MAX); |
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lblk_num = (u32)(ci->ci_hashed_ino + lblk_num); |
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} else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { |
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memcpy(iv->nonce, ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE); |
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} |
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iv->lblk_num = cpu_to_le64(lblk_num); |
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} |
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/* Encrypt or decrypt a single filesystem block of file contents */ |
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int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw, |
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u64 lblk_num, struct page *src_page, |
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struct page *dest_page, unsigned int len, |
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unsigned int offs, gfp_t gfp_flags) |
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{ |
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union fscrypt_iv iv; |
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struct skcipher_request *req = NULL; |
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DECLARE_CRYPTO_WAIT(wait); |
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struct scatterlist dst, src; |
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struct fscrypt_info *ci = inode->i_crypt_info; |
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struct crypto_skcipher *tfm = ci->ci_enc_key.tfm; |
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int res = 0; |
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if (WARN_ON_ONCE(len <= 0)) |
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return -EINVAL; |
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if (WARN_ON_ONCE(len % FS_CRYPTO_BLOCK_SIZE != 0)) |
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return -EINVAL; |
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fscrypt_generate_iv(&iv, lblk_num, ci); |
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req = skcipher_request_alloc(tfm, gfp_flags); |
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if (!req) |
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return -ENOMEM; |
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skcipher_request_set_callback( |
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req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, |
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crypto_req_done, &wait); |
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sg_init_table(&dst, 1); |
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sg_set_page(&dst, dest_page, len, offs); |
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sg_init_table(&src, 1); |
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sg_set_page(&src, src_page, len, offs); |
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skcipher_request_set_crypt(req, &src, &dst, len, &iv); |
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if (rw == FS_DECRYPT) |
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res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait); |
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else |
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res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); |
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skcipher_request_free(req); |
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if (res) { |
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fscrypt_err(inode, "%scryption failed for block %llu: %d", |
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(rw == FS_DECRYPT ? "De" : "En"), lblk_num, res); |
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return res; |
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} |
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return 0; |
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} |
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/** |
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* fscrypt_encrypt_pagecache_blocks() - Encrypt filesystem blocks from a |
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* pagecache page |
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* @page: The locked pagecache page containing the block(s) to encrypt |
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* @len: Total size of the block(s) to encrypt. Must be a nonzero |
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* multiple of the filesystem's block size. |
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* @offs: Byte offset within @page of the first block to encrypt. Must be |
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* a multiple of the filesystem's block size. |
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* @gfp_flags: Memory allocation flags. See details below. |
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* |
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* A new bounce page is allocated, and the specified block(s) are encrypted into |
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* it. In the bounce page, the ciphertext block(s) will be located at the same |
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* offsets at which the plaintext block(s) were located in the source page; any |
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* other parts of the bounce page will be left uninitialized. However, normally |
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* blocksize == PAGE_SIZE and the whole page is encrypted at once. |
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* |
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* This is for use by the filesystem's ->writepages() method. |
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* |
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* The bounce page allocation is mempool-backed, so it will always succeed when |
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* @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS. However, |
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* only the first page of each bio can be allocated this way. To prevent |
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* deadlocks, for any additional pages a mask like GFP_NOWAIT must be used. |
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* |
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* Return: the new encrypted bounce page on success; an ERR_PTR() on failure |
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*/ |
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struct page *fscrypt_encrypt_pagecache_blocks(struct page *page, |
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unsigned int len, |
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unsigned int offs, |
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gfp_t gfp_flags) |
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{ |
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const struct inode *inode = page->mapping->host; |
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const unsigned int blockbits = inode->i_blkbits; |
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const unsigned int blocksize = 1 << blockbits; |
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struct page *ciphertext_page; |
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u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) + |
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(offs >> blockbits); |
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unsigned int i; |
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int err; |
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if (WARN_ON_ONCE(!PageLocked(page))) |
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return ERR_PTR(-EINVAL); |
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if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize))) |
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return ERR_PTR(-EINVAL); |
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ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags); |
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if (!ciphertext_page) |
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return ERR_PTR(-ENOMEM); |
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for (i = offs; i < offs + len; i += blocksize, lblk_num++) { |
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err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, |
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page, ciphertext_page, |
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blocksize, i, gfp_flags); |
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if (err) { |
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fscrypt_free_bounce_page(ciphertext_page); |
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return ERR_PTR(err); |
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} |
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} |
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SetPagePrivate(ciphertext_page); |
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set_page_private(ciphertext_page, (unsigned long)page); |
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return ciphertext_page; |
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} |
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EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks); |
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/** |
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* fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place |
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* @inode: The inode to which this block belongs |
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* @page: The page containing the block to encrypt |
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* @len: Size of block to encrypt. Doesn't need to be a multiple of the |
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* fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE. |
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* @offs: Byte offset within @page at which the block to encrypt begins |
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* @lblk_num: Filesystem logical block number of the block, i.e. the 0-based |
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* number of the block within the file |
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* @gfp_flags: Memory allocation flags |
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* |
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* Encrypt a possibly-compressed filesystem block that is located in an |
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* arbitrary page, not necessarily in the original pagecache page. The @inode |
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* and @lblk_num must be specified, as they can't be determined from @page. |
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* |
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* Return: 0 on success; -errno on failure |
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*/ |
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int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page, |
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unsigned int len, unsigned int offs, |
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u64 lblk_num, gfp_t gfp_flags) |
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{ |
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return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page, page, |
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len, offs, gfp_flags); |
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} |
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EXPORT_SYMBOL(fscrypt_encrypt_block_inplace); |
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/** |
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* fscrypt_decrypt_pagecache_blocks() - Decrypt filesystem blocks in a |
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* pagecache page |
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* @page: The locked pagecache page containing the block(s) to decrypt |
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* @len: Total size of the block(s) to decrypt. Must be a nonzero |
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* multiple of the filesystem's block size. |
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* @offs: Byte offset within @page of the first block to decrypt. Must be |
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* a multiple of the filesystem's block size. |
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* |
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* The specified block(s) are decrypted in-place within the pagecache page, |
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* which must still be locked and not uptodate. Normally, blocksize == |
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* PAGE_SIZE and the whole page is decrypted at once. |
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* |
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* This is for use by the filesystem's ->readpages() method. |
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* |
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* Return: 0 on success; -errno on failure |
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*/ |
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int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len, |
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unsigned int offs) |
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{ |
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const struct inode *inode = page->mapping->host; |
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const unsigned int blockbits = inode->i_blkbits; |
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const unsigned int blocksize = 1 << blockbits; |
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u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) + |
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(offs >> blockbits); |
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unsigned int i; |
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int err; |
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if (WARN_ON_ONCE(!PageLocked(page))) |
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return -EINVAL; |
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if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize))) |
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return -EINVAL; |
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for (i = offs; i < offs + len; i += blocksize, lblk_num++) { |
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err = fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, |
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page, blocksize, i, GFP_NOFS); |
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if (err) |
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return err; |
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} |
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return 0; |
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} |
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EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks); |
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/** |
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* fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place |
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* @inode: The inode to which this block belongs |
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* @page: The page containing the block to decrypt |
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* @len: Size of block to decrypt. Doesn't need to be a multiple of the |
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* fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE. |
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* @offs: Byte offset within @page at which the block to decrypt begins |
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* @lblk_num: Filesystem logical block number of the block, i.e. the 0-based |
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* number of the block within the file |
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* |
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* Decrypt a possibly-compressed filesystem block that is located in an |
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* arbitrary page, not necessarily in the original pagecache page. The @inode |
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* and @lblk_num must be specified, as they can't be determined from @page. |
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* |
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* Return: 0 on success; -errno on failure |
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*/ |
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int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page, |
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unsigned int len, unsigned int offs, |
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u64 lblk_num) |
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{ |
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return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page, |
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len, offs, GFP_NOFS); |
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} |
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EXPORT_SYMBOL(fscrypt_decrypt_block_inplace); |
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/** |
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* fscrypt_initialize() - allocate major buffers for fs encryption. |
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* @cop_flags: fscrypt operations flags |
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* |
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* We only call this when we start accessing encrypted files, since it |
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* results in memory getting allocated that wouldn't otherwise be used. |
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* |
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* Return: 0 on success; -errno on failure |
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*/ |
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int fscrypt_initialize(unsigned int cop_flags) |
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{ |
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int err = 0; |
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/* No need to allocate a bounce page pool if this FS won't use it. */ |
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if (cop_flags & FS_CFLG_OWN_PAGES) |
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return 0; |
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mutex_lock(&fscrypt_init_mutex); |
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if (fscrypt_bounce_page_pool) |
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goto out_unlock; |
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err = -ENOMEM; |
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fscrypt_bounce_page_pool = |
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mempool_create_page_pool(num_prealloc_crypto_pages, 0); |
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if (!fscrypt_bounce_page_pool) |
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goto out_unlock; |
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err = 0; |
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out_unlock: |
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mutex_unlock(&fscrypt_init_mutex); |
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return err; |
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} |
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void fscrypt_msg(const struct inode *inode, const char *level, |
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const char *fmt, ...) |
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{ |
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static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, |
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DEFAULT_RATELIMIT_BURST); |
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struct va_format vaf; |
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va_list args; |
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if (!__ratelimit(&rs)) |
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return; |
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va_start(args, fmt); |
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vaf.fmt = fmt; |
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vaf.va = &args; |
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if (inode && inode->i_ino) |
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printk("%sfscrypt (%s, inode %lu): %pV\n", |
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level, inode->i_sb->s_id, inode->i_ino, &vaf); |
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else if (inode) |
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printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf); |
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else |
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printk("%sfscrypt: %pV\n", level, &vaf); |
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va_end(args); |
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} |
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/** |
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* fscrypt_init() - Set up for fs encryption. |
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* |
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* Return: 0 on success; -errno on failure |
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*/ |
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static int __init fscrypt_init(void) |
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{ |
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int err = -ENOMEM; |
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/* |
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* Use an unbound workqueue to allow bios to be decrypted in parallel |
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* even when they happen to complete on the same CPU. This sacrifices |
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* locality, but it's worthwhile since decryption is CPU-intensive. |
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* |
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* Also use a high-priority workqueue to prioritize decryption work, |
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* which blocks reads from completing, over regular application tasks. |
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*/ |
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fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue", |
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WQ_UNBOUND | WQ_HIGHPRI, |
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num_online_cpus()); |
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if (!fscrypt_read_workqueue) |
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goto fail; |
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fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT); |
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if (!fscrypt_info_cachep) |
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goto fail_free_queue; |
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err = fscrypt_init_keyring(); |
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if (err) |
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goto fail_free_info; |
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return 0; |
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fail_free_info: |
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kmem_cache_destroy(fscrypt_info_cachep); |
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fail_free_queue: |
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destroy_workqueue(fscrypt_read_workqueue); |
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fail: |
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return err; |
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} |
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late_initcall(fscrypt_init)
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