diff options
Diffstat (limited to 'fs/crypto/crypto.c')
| -rw-r--r-- | fs/crypto/crypto.c | 411 |
1 files changed, 411 insertions, 0 deletions
diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c new file mode 100644 index 0000000000..6a837e4b80 --- /dev/null +++ b/fs/crypto/crypto.c @@ -0,0 +1,411 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * This contains encryption functions for per-file encryption. + * + * Copyright (C) 2015, Google, Inc. + * Copyright (C) 2015, Motorola Mobility + * + * Written by Michael Halcrow, 2014. + * + * Filename encryption additions + * Uday Savagaonkar, 2014 + * Encryption policy handling additions + * Ildar Muslukhov, 2014 + * Add fscrypt_pullback_bio_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 <linux/pagemap.h> +#include <linux/mempool.h> +#include <linux/module.h> +#include <linux/scatterlist.h> +#include <linux/ratelimit.h> +#include <crypto/skcipher.h> +#include "fscrypt_private.h" + +static unsigned int num_prealloc_crypto_pages = 32; + +module_param(num_prealloc_crypto_pages, uint, 0444); +MODULE_PARM_DESC(num_prealloc_crypto_pages, + "Number of crypto pages to preallocate"); + +static mempool_t *fscrypt_bounce_page_pool = NULL; + +static struct workqueue_struct *fscrypt_read_workqueue; +static DEFINE_MUTEX(fscrypt_init_mutex); + +struct kmem_cache *fscrypt_info_cachep; + +void fscrypt_enqueue_decrypt_work(struct work_struct *work) +{ + queue_work(fscrypt_read_workqueue, work); +} +EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work); + +struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags) +{ + return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags); +} + +/** + * fscrypt_free_bounce_page() - free a ciphertext bounce page + * @bounce_page: the bounce page to free, or NULL + * + * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(), + * or by fscrypt_alloc_bounce_page() directly. + */ +void fscrypt_free_bounce_page(struct page *bounce_page) +{ + if (!bounce_page) + return; + set_page_private(bounce_page, (unsigned long)NULL); + ClearPagePrivate(bounce_page); + mempool_free(bounce_page, fscrypt_bounce_page_pool); +} +EXPORT_SYMBOL(fscrypt_free_bounce_page); + +/* + * Generate the IV for the given logical block number within the given file. + * For filenames encryption, lblk_num == 0. + * + * Keep this in sync with fscrypt_limit_io_blocks(). fscrypt_limit_io_blocks() + * needs to know about any IV generation methods where the low bits of IV don't + * simply contain the lblk_num (e.g., IV_INO_LBLK_32). + */ +void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num, + const struct fscrypt_info *ci) +{ + u8 flags = fscrypt_policy_flags(&ci->ci_policy); + + memset(iv, 0, ci->ci_mode->ivsize); + + if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { + WARN_ON_ONCE(lblk_num > U32_MAX); + WARN_ON_ONCE(ci->ci_inode->i_ino > U32_MAX); + lblk_num |= (u64)ci->ci_inode->i_ino << 32; + } else if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { + WARN_ON_ONCE(lblk_num > U32_MAX); + lblk_num = (u32)(ci->ci_hashed_ino + lblk_num); + } else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { + memcpy(iv->nonce, ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE); + } + iv->lblk_num = cpu_to_le64(lblk_num); +} + +/* Encrypt or decrypt a single filesystem block of file contents */ +int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw, + u64 lblk_num, struct page *src_page, + struct page *dest_page, unsigned int len, + unsigned int offs, gfp_t gfp_flags) +{ + union fscrypt_iv iv; + struct skcipher_request *req = NULL; + DECLARE_CRYPTO_WAIT(wait); + struct scatterlist dst, src; + struct fscrypt_info *ci = inode->i_crypt_info; + struct crypto_skcipher *tfm = ci->ci_enc_key.tfm; + int res = 0; + + if (WARN_ON_ONCE(len <= 0)) + return -EINVAL; + if (WARN_ON_ONCE(len % FSCRYPT_CONTENTS_ALIGNMENT != 0)) + return -EINVAL; + + fscrypt_generate_iv(&iv, lblk_num, ci); + + req = skcipher_request_alloc(tfm, gfp_flags); + if (!req) + return -ENOMEM; + + skcipher_request_set_callback( + req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, + crypto_req_done, &wait); + + sg_init_table(&dst, 1); + sg_set_page(&dst, dest_page, len, offs); + sg_init_table(&src, 1); + sg_set_page(&src, src_page, len, offs); + skcipher_request_set_crypt(req, &src, &dst, len, &iv); + if (rw == FS_DECRYPT) + res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait); + else + res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); + skcipher_request_free(req); + if (res) { + fscrypt_err(inode, "%scryption failed for block %llu: %d", + (rw == FS_DECRYPT ? "De" : "En"), lblk_num, res); + return res; + } + return 0; +} + +/** + * fscrypt_encrypt_pagecache_blocks() - Encrypt filesystem blocks from a + * pagecache page + * @page: The locked pagecache page containing the block(s) to encrypt + * @len: Total size of the block(s) to encrypt. Must be a nonzero + * multiple of the filesystem's block size. + * @offs: Byte offset within @page of the first block to encrypt. Must be + * a multiple of the filesystem's block size. + * @gfp_flags: Memory allocation flags. See details below. + * + * A new bounce page is allocated, and the specified block(s) are encrypted into + * it. In the bounce page, the ciphertext block(s) will be located at the same + * offsets at which the plaintext block(s) were located in the source page; any + * other parts of the bounce page will be left uninitialized. However, normally + * blocksize == PAGE_SIZE and the whole page is encrypted at once. + * + * This is for use by the filesystem's ->writepages() method. + * + * The bounce page allocation is mempool-backed, so it will always succeed when + * @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS. However, + * only the first page of each bio can be allocated this way. To prevent + * deadlocks, for any additional pages a mask like GFP_NOWAIT must be used. + * + * Return: the new encrypted bounce page on success; an ERR_PTR() on failure + */ +struct page *fscrypt_encrypt_pagecache_blocks(struct page *page, + unsigned int len, + unsigned int offs, + gfp_t gfp_flags) + +{ + const struct inode *inode = page->mapping->host; + const unsigned int blockbits = inode->i_blkbits; + const unsigned int blocksize = 1 << blockbits; + struct page *ciphertext_page; + u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) + + (offs >> blockbits); + unsigned int i; + int err; + + if (WARN_ON_ONCE(!PageLocked(page))) + return ERR_PTR(-EINVAL); + + if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize))) + return ERR_PTR(-EINVAL); + + ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags); + if (!ciphertext_page) + return ERR_PTR(-ENOMEM); + + for (i = offs; i < offs + len; i += blocksize, lblk_num++) { + err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, + page, ciphertext_page, + blocksize, i, gfp_flags); + if (err) { + fscrypt_free_bounce_page(ciphertext_page); + return ERR_PTR(err); + } + } + SetPagePrivate(ciphertext_page); + set_page_private(ciphertext_page, (unsigned long)page); + return ciphertext_page; +} +EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks); + +/** + * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place + * @inode: The inode to which this block belongs + * @page: The page containing the block to encrypt + * @len: Size of block to encrypt. This must be a multiple of + * FSCRYPT_CONTENTS_ALIGNMENT. + * @offs: Byte offset within @page at which the block to encrypt begins + * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based + * number of the block within the file + * @gfp_flags: Memory allocation flags + * + * Encrypt a possibly-compressed filesystem block that is located in an + * arbitrary page, not necessarily in the original pagecache page. The @inode + * and @lblk_num must be specified, as they can't be determined from @page. + * + * Return: 0 on success; -errno on failure + */ +int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page, + unsigned int len, unsigned int offs, + u64 lblk_num, gfp_t gfp_flags) +{ + return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page, page, + len, offs, gfp_flags); +} +EXPORT_SYMBOL(fscrypt_encrypt_block_inplace); + +/** + * fscrypt_decrypt_pagecache_blocks() - Decrypt filesystem blocks in a + * pagecache folio + * @folio: The locked pagecache folio containing the block(s) to decrypt + * @len: Total size of the block(s) to decrypt. Must be a nonzero + * multiple of the filesystem's block size. + * @offs: Byte offset within @folio of the first block to decrypt. Must be + * a multiple of the filesystem's block size. + * + * The specified block(s) are decrypted in-place within the pagecache folio, + * which must still be locked and not uptodate. + * + * This is for use by the filesystem's ->readahead() method. + * + * Return: 0 on success; -errno on failure + */ +int fscrypt_decrypt_pagecache_blocks(struct folio *folio, size_t len, + size_t offs) +{ + const struct inode *inode = folio->mapping->host; + const unsigned int blockbits = inode->i_blkbits; + const unsigned int blocksize = 1 << blockbits; + u64 lblk_num = ((u64)folio->index << (PAGE_SHIFT - blockbits)) + + (offs >> blockbits); + size_t i; + int err; + + if (WARN_ON_ONCE(!folio_test_locked(folio))) + return -EINVAL; + + if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize))) + return -EINVAL; + + for (i = offs; i < offs + len; i += blocksize, lblk_num++) { + struct page *page = folio_page(folio, i >> PAGE_SHIFT); + + err = fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, + page, blocksize, i & ~PAGE_MASK, + GFP_NOFS); + if (err) + return err; + } + return 0; +} +EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks); + +/** + * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place + * @inode: The inode to which this block belongs + * @page: The page containing the block to decrypt + * @len: Size of block to decrypt. This must be a multiple of + * FSCRYPT_CONTENTS_ALIGNMENT. + * @offs: Byte offset within @page at which the block to decrypt begins + * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based + * number of the block within the file + * + * Decrypt a possibly-compressed filesystem block that is located in an + * arbitrary page, not necessarily in the original pagecache page. The @inode + * and @lblk_num must be specified, as they can't be determined from @page. + * + * Return: 0 on success; -errno on failure + */ +int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page, + unsigned int len, unsigned int offs, + u64 lblk_num) +{ + return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page, + len, offs, GFP_NOFS); +} +EXPORT_SYMBOL(fscrypt_decrypt_block_inplace); + +/** + * fscrypt_initialize() - allocate major buffers for fs encryption. + * @sb: the filesystem superblock + * + * We only call this when we start accessing encrypted files, since it + * results in memory getting allocated that wouldn't otherwise be used. + * + * Return: 0 on success; -errno on failure + */ +int fscrypt_initialize(struct super_block *sb) +{ + int err = 0; + mempool_t *pool; + + /* pairs with smp_store_release() below */ + if (likely(smp_load_acquire(&fscrypt_bounce_page_pool))) + return 0; + + /* No need to allocate a bounce page pool if this FS won't use it. */ + if (sb->s_cop->flags & FS_CFLG_OWN_PAGES) + return 0; + + mutex_lock(&fscrypt_init_mutex); + if (fscrypt_bounce_page_pool) + goto out_unlock; + + err = -ENOMEM; + pool = mempool_create_page_pool(num_prealloc_crypto_pages, 0); + if (!pool) + goto out_unlock; + /* pairs with smp_load_acquire() above */ + smp_store_release(&fscrypt_bounce_page_pool, pool); + err = 0; +out_unlock: + mutex_unlock(&fscrypt_init_mutex); + return err; +} + +void fscrypt_msg(const struct inode *inode, const char *level, + const char *fmt, ...) +{ + static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, + DEFAULT_RATELIMIT_BURST); + struct va_format vaf; + va_list args; + + if (!__ratelimit(&rs)) + return; + + va_start(args, fmt); + vaf.fmt = fmt; + vaf.va = &args; + if (inode && inode->i_ino) + printk("%sfscrypt (%s, inode %lu): %pV\n", + level, inode->i_sb->s_id, inode->i_ino, &vaf); + else if (inode) + printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf); + else + printk("%sfscrypt: %pV\n", level, &vaf); + va_end(args); +} + +/** + * fscrypt_init() - Set up for fs encryption. + * + * Return: 0 on success; -errno on failure + */ +static int __init fscrypt_init(void) +{ + int err = -ENOMEM; + + /* + * Use an unbound workqueue to allow bios to be decrypted in parallel + * even when they happen to complete on the same CPU. This sacrifices + * locality, but it's worthwhile since decryption is CPU-intensive. + * + * Also use a high-priority workqueue to prioritize decryption work, + * which blocks reads from completing, over regular application tasks. + */ + fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue", + WQ_UNBOUND | WQ_HIGHPRI, + num_online_cpus()); + if (!fscrypt_read_workqueue) + goto fail; + + fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT); + if (!fscrypt_info_cachep) + goto fail_free_queue; + + err = fscrypt_init_keyring(); + if (err) + goto fail_free_info; + + return 0; + +fail_free_info: + kmem_cache_destroy(fscrypt_info_cachep); +fail_free_queue: + destroy_workqueue(fscrypt_read_workqueue); +fail: + return err; +} +late_initcall(fscrypt_init) |